WO2012024323A2

WO2012024323A2 - Femoral cutting guide

Info

Publication number: WO2012024323A2
Application number: PCT/US2011/047966
Authority: WO
Inventors: Daniel A. Heuer; Ryan L. Landon; Randy C. Winebarger
Original assignee: Smith & Nephew, Inc.
Priority date: 2010-08-16
Filing date: 2011-08-16
Publication date: 2012-02-23
Also published as: WO2012024319A3; WO2012024323A3; WO2012024319A2

Abstract

Systems, devices, and methods are provided for resecting an end of a bone using a cutting guide in which some aspect of the anterior or posterior cutting slots can be adjusted by the surgeon. In certain implementations, the systems, devices, and methods apply to a secondary cutting guide that is used to make a second cut to a bone surface that has already been resected with a conventional cutting guide. In certain implementations, the systems, devices, and methods apply to primary cutting guides used to make any of the anterior, posterior, distal, or chamfer cuts to a bone surface. In certain implementations, the cutting guides or other cutting components are box-matched to an implant in order to provide a desired press-fit.

Description

FEMORAL CUTTING GUIDE

Cross- eference to Related Application

[0001] This application claims the benefit of United States Provisional Patent Application No. 61/373,943, filed August 16, 2010, which is hereby incorporated by reference herein in its entirety.

Background

[0002] In knee replacement surgeries, a cutting guide is generally used to cut various sections of the diseased end of the femur prior to a surgeon implanting a femoral implant. Conventional cutting guides often include multiple cutting slots that are fixed in place for receiving a cutting blade. The cutting blade is used to make anterior, posterior, distal, and chamfer cuts on the end of the femur to shape the end of the bone to match the shape of a femoral implant. After the cuts are made, a femoral trial component is placed on the femur to ensure proper sizing, alignment, and tissue balancing. Once the surgeon is satisfied with the fit of the trial component, the trial component is removed, and the femoral implant is applied to the resected femur either by cemented or by cementless techniques using a system such as the LEGION™ Total Knee System (Smith & Nephew, Inc.).

[0003] Conventional cutting guides are typically sized and shaped to correspond to a standard implant size, having cutting slots that are permanently positioned within the guide. The surgeon accordingly chooses a cutting guide based on the measured size of the bone. The cutting guide shapes the bone to match the final implant geometry. For a cementless system, there is a targeted level of press-fit between the implant and the bone designed into the system based on the relative geometry of the implant and the cutting guide. This press-fit is intended to provide enough initial stability to allow bone ingrowth into the porous surface of the implant to achieve stable long-term fixation. There typically is no way to modify the level of press-fit to accommodate individual surgeon preferences. Furthermore, the manufacturing tolerances of the implants create variability in even "standard" implant sizes such that conventional cutting guides for those "standard" sizes cannot guarantee that a targeted level of press-fit can even be met. [0004] There are several reasons why a surgeon might want to alter the level of press-fit between the implant and bone from that designed into the system. Some of these include such things as different porous coating technologies, different implant substrate materials, different patient bone quality, different press-fit philosophies, etc. A fixed cutting guide may not allow the surgeon to obtain what he or she feels is the ideal fit of the implant. Suboptimal fitting of the implant may cause pain or discomfort in patients, may delay healing or bone ingrowth, and may even lead to loosening of the implant in some cases.

[0005] Cementless implants are desirable because they allow more stable long-term biologic fixation between the implant and the bone compared to cement-based systems, in which the cement layer can fail over time. However, suboptimal fitting of the implant can impede or prevent the bone ingrowth necessary for stable long-term fixation.

[0006] Conventional cutting guides also do not accommodate for variation in component- to-component geometry, which can influence the press-fit obtained between the implant and the resected bone. Furthermore, conventional cutting guides allow for some uncontrolled variability in bone cuts due to individual surgeon technique. Because of the difficulty of achieving a consistent proper press-fit for the implant, some surgeons choose cement-based systems over cementless systems, which may provide greater consistency in results, but can be undesirable for a number of other reasons.

[0007] Another problem with the use of a conventional femoral cutting guide is that the posterior, anterior, and chamfer cuts are all typically made with the guide on the plane of the distal femoral cut. As a result, the blade guides are positioned at a significant distance from the portions of the anterior and posterior bone that will be in contact with the implant. With the blade guides at such a distance from this bone, the blade has a greater chance of deviating from its intended path, which makes it more difficult for a surgeon to make accurate cuts to the anterior and posterior portions of the bone. Deviation from an ideal cutting dimension tends to increase as the distance between the blade guide and the bone increases, thereby resulting in a less accurate bone cut. Such deviations will vary according to bone quality and surgical technique. Conventional cutting guides do not account for that variation.

Summary

[0008] Disclosed herein are systems, devices, and methods for resecting an end of a bone using a cutting guide with anterior and posterior cutting slots that can be adjusted by the surgeon. In certain implementations, the systems, devices, and methods apply to a secondary cutting guide that is used to make a second cut or finishing cut to a bone surface that has already been resected with a conventional cutting guide. In certain implementations, the systems, devices, and methods apply to primary cutting guides used to make any of the anterior, posterior, distal, or chamfer cuts to a bone surface.

[0009] In certain embodiments, the systems, devices, and methods include a cutting guide comprising a base and a first guide block containing a cutting slot, the base having a first fixation feature designed to engage a guide block and a first guide block that includes two fixation features, both of which are designed to engage with the first fixation feature of the base such that the cutting guide could be assembled in either of two orientations with each orientation providing a different distance between the base and the cutting slot.

[0010] In certain embodiments, surgical systems and devices include a cutting guide having a first guide block with an angled surface and a base with an angled surface, the block and base intended to be in contact along their angled surfaces and able to adjust the anterior- posterior dimension of the cutting guide. The guide block and base are adjustably positionable with respect to each other, for example, in the medial-lateral direction which affects a change in the anterior-posterior dimension of the cutting guide to allow for a more precise finishing cut along a previously resected surface to provide a more ideally shaped bone end to receive the implant.

[0011] In certain implementations, the guide block and base are intended to allow for adjustment in discrete increments. In certain implementations, the adjustment in discrete increments is accomplished using a base that includes a plurality of receptacles disposed on the first angled mating surface, where the receptacles are spaced at a predetermined distance from one another to allow discrete incremental adjustable engagement between the first guide block and the base in the medial-lateral direction which affects a discrete incremental change in the anterior-posterior dimension of the cutting guide. The guide block may have mating protrusions. Alternatively, or additionally, the base may have protrusions and the guide block may have receptacles. The base includes a top surface shaped to align with an end of the femur.

[0012] In certain implementations, the guide block and base are designed to allow for continuous adjustment over a range. In certain implementations, the continuous adjustment over a range is accomplished using a base that includes a first angled mating surface and a first guide block that includes an angled mating surface, where the angled mating surfaces of the base and the first guide block are in contact in such a way as to allow continuous adjustment over a range in the medial-lateral direction which affects a continuous adjustment over a range in the anterior-posterior dimension of the cutting guide. The cutting guide may also include a mechanism to temporarily fix the position of the guide block with respect to the base, thereby also fixing the anterior posterior dimension of the cutting guide.

[0013] Some devices and systems include a first guide block having a first cutting slot that accommodates a blade, a second guide block having a second cutting slot that accommodates a blade, and a base releasably and adjustably disposed between the first and second guide blocks. The base includes a first side surface, a second side surface, and a top surface that fits against the surface of a bone. The base may also include an angled mating surface extending between the first and the second side surfaces, where the angled mating surface includes a plurality of connector points for adjustably positioning at least one of the guide blocks. In certain implementations, both first and second guide blocks include a protrusion having a connecting mechanism adapted to releasably engage corresponding receptacles of the base. In certain implementations, the protrusion includes a sliding dove tail.

[0014] In certain embodiments, an adjustable cutting guide is provided for resecting an end of a bone that has already been resected with posterior and anterior chamfer cuts using a conventional cutting guide. The adjustable cutting guide may include a first guide block having a cutting slot of a first height and a second guide block having a cutting slot of a second height, where the second height is shorter than the first height. The differential heights allow the two cutting slots to extend beyond the distal cut surface to within the resected chamfer cut areas, thereby positioning the cutting blade closer to the anterior and posterior regions of bone to be resected. The adjustable cutting guide may also include a base releasably disposed between the first and second guide blocks. The base, if used, includes, in certain implementations, an anterior surface structured to releasably engage the first guide block, a posterior surface structured to releasably engage the second guide block, and a top surface which conforms to already resected surfaces of the bone. Thus, the region below the distal surface of the bone may be thinner than the region below the chamfer surfaces of the bone.

[0015] The base of any of the systems and devices described above may include a position indicator disposed on a bottom surface, or any other suitable surface, of the base. The guide blocks may include complementary indicators adapted to align with the position indicator of the base.

[0016] Further disclosed herein are systems, devices, and methods for providing custom cutting block components, such as cutting blocks that are matched to a particular implant. In certain embodiments, a method for providing a custom cutting block component includes measuring an implant for an implant dimension, evaluating the implant dimension against press-fit criteria, and providing a cutting block component based on the evaluation, wherein the cutting block component has a cutting dimension based on the measured implant dimension and the press-fit criteria. The implant dimension may be a distance along an anterior bone-facing surface of the implant and a posterior bone-facing surface of the implant. The press-fit criteria include a desired press-fit and patient bone quality data. In certain embodiments, the evaluating comprises determining, based on the patient bone quality data, the cutting dimension that provides the desired press-fit. The method can further include inputting measurement data into a processor, the measurement data corresponding to relative locations and orientations of bone-facing surfaces on the implant, analyzing the measurement data against manufacturing tolerance data and the press-fit criteria to determine a cutting dimension, and producing the cutting block component based on the determined cutting dimension.

[0017] In certain embodiments, the measuring step further includes placing a gage in contact with the implant, the gage having a first contact surface and a second contact surface, and reading an output from the gage, the output indicating the implant dimension. The gage may be an expandable anterior-posterior gage, and at least one of the first and second contact surfaces can be expanded in an anterior or posterior direction. In certain embodiments, the gage is expanded using a screw adjustment with pressure feedback or pneumatic or hydraulic pressure. At least one of the first and second contact surfaces may have a compliant surface to allow interdigitation with a texture of the implant. In certain embodiments, the measuring step further includes obtaining a plurality of positional data points on bone-facing surfaces of the implant. For example, each surface of the implant may be contacted with an array of sliding measurement pins to provide the plurality of positional data points. The plurality of positional data points may also be obtained using a CMM-type instrument or a laser or white light scanning.

[0018] In certain embodiments, the press-fit criteria is met by producing the cutting block with a cutting dimension between approximately 0.1 mm to 2.0 mm greater than the measured implant dimension. In certain embodiments, the cutting dimension is

approximately 0.5 mm to 1.0 mm greater than the measured implant dimension.

[0019] In some embodiments, the cutting block component may be a cutting block insert having a cutting slot, the cutting block insert configured to mate with a cutting block. In some embodiments, the cutting block component is a finishing cutting block used to make any of an anterior, posterior, chamfer, and distal cut. In some embodiments, the cutting block component is a primary cutting block used to make any of an anterior, posterior, chamfer, and distal cut.

[0020] In certain embodiments, a method for resecting a patient's bone using a custom cutting block component includes selecting an implant from a kit of a plurality of implants, selecting a cutting block component having cutting dimensions matched to a measured implant dimension of the implant and a press-fit criteria, resecting a patient's bone using the cutting block component, and installing the implant on the patient's resected bone, wherein the installed implant has a press-fit with the patient's resected bone within the press-fit criteria.

[0021] In certain embodiments, a kit with orthopedic surgery components is provided that includes an implant having an implant dimension and a cutting block matched to the implant, the cutting block having a cutting dimension based on the implant dimension, wherein the cutting block guides resection of the patient's bone and has a plurality of configurations that provide pre-determined levels of press-fit between the patient's bone and the implant. In certain embodiments, the kit further includes a gage for measuring the implant and providing an output that corresponds to the implant dimension

[0022] In certain embodiments, the orthopedic blocks or guides described herein are patient-matched to the particular anatomy of a patient. Patient-matched instruments help the surgeon achieve more optimal implant alignment, custom to the patient's unique knee anatomy. With patient-matched instruments and guides, a patient's anatomy including the knee system may be imaged using a standard imaging technology such as X-ray, Magnetic Resonance Imaging (MRI), CT scanning, or any other suitable imaging technology. This imaging data can then be imported into a computer-aided design (CAD) or similar system and used as the basis for developing a multi-dimensional digital model of the patient's anatomy of interest through segmentation and other processing procedures. Surgical instruments and guides can then designed and built, mapping out specific bone cuts to accurately align the implants that will be placed into the patient's knee.

[0023] Variations and modifications of these embodiments will occur to those of skill in the art after reviewing this disclosure. The foregoing features and aspects may be implemented, in any combination and subcombinations (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented. Brief Description of the Drawings

[0024] The foregoing and other objects and advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:

[0025] Figure 1 A shows a perspective view of an illustrative adjustable cutting guide;

[0026] Figure IB shows a top plan view of an illustrative reversible guide block;

[0027] Figure 2 shows a bottom plan view of an illustrative adjustable cutting guide;

[0028] Figure 3 shows an exploded view of the adjustable cutting guide of Figure 2;

[0029] Figure 4 shows an exploded and cross-sectional view of a first guide block and a base of the adjustable cutting guide of Figure 3;

[0030] Figure 5 shows a perspective view of a base of the adjustable cutting guide of Figures 3 and 4;

[0031] Figures 6A-6C show bottom views of illustrative first and second guide blocks mated to a base in various adjustable positions;

[0032] Figure 7A shows a side elevation view of a resected femur and an illustrative adjustable cutting guide mounted onto the end of the resected femur;

[0033] Figure 7B shows a top plan view of the adjustable cutting guide of Figure 7A;

[0034] Figure 8 shows a side elevation view of a resected femur and an illustrative adjustable cutting guide mounted onto the end of the resected femur;

[0035] Figure 9 shows a side elevation view of an illustrative femoral implant;

[0036] Figure 10 shows a schematic view of an illustrative interface between the femoral implant of Figure 9 and a patient's femur;

[0037] Figure 11 shows an illustrative flow chart for providing a cutting block component;

[0038] Figures 12 and 13 show side elevation views of various illustrative gages for measuring an implant dimension;

[0039] Figure 14 shows a side elevation view of an illustrative implant and finishing cutting block that is matched to the implant; and

[0040] Figure 15 shows a side elevation view of an illustrative implant and cutting block that is matched to the implant.

Detailed Description

[0041] To provide an overall understanding of the systems, devices, and methods described herein, certain illustrative embodiments will be described. Although the embodiments and features described herein are specifically described for use in connection with orthopedic knee replacement systems, it will be understood that all the components, connection mechanisms, adjustable systems, manufacturing methods, and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to medical devices and implants to be used in other surgical procedures, including, but not limited to acetabular procedures, spine arthroplasty, cranio-maxillofacial surgical procedures, hip arthroplasty, shoulder arthroplasty, as well as foot, ankle, hand, and other extremity procedures.

[0042] The figures illustrate certain implementations of adjustable cutting guides used to resect an end of a femur to allow a surgeon to provide a more accurate press-fit between a femoral implant and the resected bone. The adjustable cutting guides are used after the surgeon uses the conventional cutting block to make the distal and chamfer cuts and the preliminary anterior and posterior cuts. The adjustable guides allow a surgeon to "fine tune" the dimension between the anterior and the posterior cuts. In certain implementations, the devices include a base and at least one guide block that is adjustable with respect to the base.

[0043] Figure 1A shows a perspective view of an adjustable cutting guide 100 having a base 102 and a guide block 104 that is disposed along the base 102 and adjustably

positionable with respect to the base 102. The guide 100 fits under the distal end of a resected femur. The base 102 is defined by a proximal surface 124 that is structured to fit against the distal bone surface of the resected femur. The base 102 is further defined by a first side surface 116, a second side surface 118, and a mating surface 122 that extends between the first and the second side surfaces 116 and 118 and abuts the guide block 104. The guide block 104 includes a cutting slot housing 108 and an angled spacer 112. As shown, the mating surface 122 of the base 102 is sized and shaped to engage the mating surface 150 on the angled spacer 112 of the guide block 104.

[0044] The cutting slot housing 108 contains a cutting slot 126 that accommodates a cutting instrument (e.g., a saw or blade). As shown, the cutting slot 126 extends through a distal surface 128 and a proximal surface 130 of the cutting slot housing 108. The cutting slot 126 also extends substantially lengthwise across the cutting slot housing 108. The thickness and length of the cutting slot 126 may be of any dimension that accommodates an appropriate cutting instrument for resecting the anterior or posterior end of the femur. In use, the cutting slot 126 is aligned with the anterior or posterior side of the femur, so that advancing a blade through the cutting slot 126 along the direction of arrows A will bring the blade into contact and resect the anterior or posterior side of the distal end of the femur. [0045] The cutting slot housing 108 is engaged with the angled spacer 112. In certain implementations, the two parts are manufactured such that they are co-molded or are affixed so as to not move with respect to one another. Alternatively, the cutting slot housing 108 may be adjustably engaged to the angled spacer 112 by latch, clip, lever lock, any other suitable mechanisms, or any combination thereof.

[0046] The guide block 104 can be adjusted relative to the base in a direction di that is perpendicular to the AP axis 120 (the anterior to posterior axis through the femur). The mating surfaces 122 and 150 are angled with respect to the cutting slot 126 in the transverse plane by the angle a in Figure 1 A. As shown in Figure 1 A, the first leg 112 has a first end 112a that is narrower than a second end 112b such that the guide mating surface 150 complements the angle a of the surface 122. Because of the angle a between the cutting slot 126 and the base 102, the guide block 104 can be adjustably moved along the surface 150 and thereby increase or decrease the anterior/posterior distance ("APd") of the cutting guide 100 along the AP axis 120. By varying this distance, the surgeon can adjustably position the guide block 104 in small increments with respect to the base 102 to cut smaller sections of the anterior or posterior bone portions, allowing the surgeon to provide more customized resection area for receiving a press-fit femoral implant. The surgeon is also able to take the quality of bone (e.g., soft vs. hard bone) into consideration when making these final and more refined cuts. Mechanisms allowing this adjustability are further explained below with respect to Figures 3-7.

[0047] In some embodiments, a guide block such as guide block 104 can be reversible. Figure IB shows a top plan view of an illustrative reversible guide block 104a. The reversible guide block 104a includes the cutting slot housing 108, having cutting slot 126, and the angled spacer 112 that were provided on guide block 104. The reversible guide block 104a further includes a second angled spacer 114 opposite the first angled spacer 112 and provided at a depth 14 from the cutting slot housing 108 that is relatively greater than the depth 12 of the first angled spacer 112. The mating surface of the base against which the reversible guide block 104a is positioned, such as mating surface 122 of base 102, is sized and shaped to engage the mating surface 150 on the angled spacer 112 and the mating surface 151 on the angled spacer 114 when the block is reversibly positioned. The depth of the angled spacers 112 and 114 increases the number of configurations in which the reversible guide block 104a can be positioned, thereby allowing a greater range of adjustments to the anterior/posterior distance of the cutting guide along an anterior/posterior axis of the cutting guide, such as AP axis 120 of Figure 1A. In some embodiments, the reversible guide block can include means other than angled spacers, or in addition to the angled spacers, to achieve fine adjustment of the distance of the cutting guide along an anterior/posterior axis. For example, this can include steps, shims of varying thickness, and adjustment screws. In embodiments where more than one guide block is used, for example, as described below, one or both of the guide blocks can have multiple assembly orientations.

[0048] In certain implementations, the adjustable cutting guide 100 includes a second guide block 106. As shown in Figure 2, the base 102 is releasably disposed between the first and second guide blocks 104 and 106, further enhancing the surgeon's ability to adjust the distance between the cutting slots 110 and 126 of the cutting guide along the AP axis 120. Figure 2 shows a bottom plan view of the adjustable cutting guide 100, showing the surface viewed by the surgeon when the guide 100 is mounted on the bone. The second guide block 106 includes a second cutting slot 110 that accommodates a cutting instrument. The second guide block 106 is also slidable with respect to the base 102. More specifically, the second guide block 106 is slidable in a direction that displaces the cutting slot 110 perpendicular to the AP axis 120 as depicted by the double headed arrow d₂, similar to the first guide block 104. By adjusting the position of the guide blocks 104 and 106 along the arrows di and d₂, respectively, a surgeon can increase or decrease the distance between the cutting slots 110 and 126 along the AP axis 120 (AP dimension 160).

[0049] Figure 3 shows an exploded view of the adjustable cutting guide 100 shown in Figure 2. The base 102 includes a proximal surface 124 having a flat face portion 132 and a chamfer face portion 134 positioned at angle β with respect to the flat face portion 132. The flat face portion 132 and chamfer face portion 134 of the proximal surface 124 are adapted so that they match the shape of the end of the resected femur. Therefore, the angle between the chamfer face portion 134 and the flat face portion 132 is determined at the time of manufacturing to match the shape of the final implant.

[0050] As shown, the width ("W") of the angled spacer 112 on the first guide block 104 increases gradually from a first side 162 towards a second side 164. First protrusions 146a and 146b protrude from the first guide block mating surface 150 and operatively engage with the base 102, such that the first guide block 104 is adjustably positionable with respect to the base 102. Similarly, second protrusions 148a and 148b protrude from the second guide block mating surface 152 and operatively engage with the base 102. More particularly, the base 102 includes sets of receptacles 156a-156e and 158a-158e for adjustably mating with respective protrusions 146a/146b and 148a/148b on the guide blocks. The first set of receptacles includes first receptacles 156a-156e, and the second set of receptacles includes second receptacles 158a-158e, each set of receptacles being disposed within the base 102. These receptacles 156a-156e and 158a-158e extend within the mating surface 122 and 154, respectively, toward the center of the base 102. In the illustrative drawings, the first protrusions 146a and 146b and the first receptacles 156a-156e are complimentary in shape, being square. These components may be of any other suitable complimentary shape.

[0051] When the first guide block 104 engages the base 102, the first protrusions 146a and 146b releasably engage two of the first receptacles 156a-156e by fitting into the receptacles. Similarly, when the second guide block 106 engages the base 102 the second protrusions 148a and 148b releasably engage two of the second receptacles 158a-158e by fitting into the receptacles. Other mechanisms for releasably securing the guide blocks 104 and 106 to the base 102 could also be used (e.g., snap-fitted or threaded).

[0052] Figure 4 shows a cross-sectional view of the first set of receptacles 156a-156e and the guide block 104 using a ball-detent connection mechanism. As illustrated, the ball-detent connection mechanism includes a pair of protrusions 146a and 146b, having spring-loaded tips 174a and 174b located near ends 113 and extending perpendicular to the protrusions 146a and 146b.

[0053] In use, the first protrusions 146a and 146b of the first guide block 104 are first aligned with a pair of the first receptacles 156 in the base 102 (it being understood that the protrusions could be located on the base and the receptacles on the guide block 104). The particular positioning of the guide blocks 104 and 106 relative to the base 102 is later explained in detail with respect to Figures 6A-6C. The first guide block 104 is then displaced along the direction noted by arrow A until the first protrusions 146a and 146b are received within a pair of the first receptacles, (e.g., 156a and 156c, 156b and 156d, or 156c and 156e). The protruding tips 174a and 174b are compressed into the first protrusions 146a and 146b (against the force of springs 178a and 178b) and remain in that compressed state as the protrusions 146a and 146b slide within the receptacles 156a and 156c along arrow A. Upon reaching the mating detents 176 disposed inside the receptacles 156a and 156c, the tips 174a and 174b click into mating detents 176, thereby temporarily locking the position of the guide block 104 relative to the base 102. When the surgeon desires to disengage the first guide block 104, he or she may manually pull the first guide block 104 in the direction opposite to the direction noted by arrow A, which compresses the spring-loaded protruding tips 174a and 174b into the protrusions 146a and 146b, and thereby disengages the tips 174a and 174b from the detents 176. [0054] The position of the first guide block 104 can be adjusted along the mating surface 122 of the base 102 by aligning the protrusions 146a/ 146b with a different pair of receptacles 156, then engaging the tips 174a and 174b with the detents 176 of those receptacles. That engagement adjusts the position of the first guide block 104 from one position to another position.

[0055] Figure 5 illustrates discrete positions PI, P2, and P3 defined in the mating surface 122 of the base 102. Each position corresponds to a unique pair of receptacles 156a-156e. The position of the second guide block 106 is also adjustable between discrete positions defined by the second receptacles 158a-158e (Figure 3) disposed on the base 102. By adjusting the position of the first guide block 104 between positions P1-P3 (i.e., between pairs of the receptacles 156a-156e) or the second guide block 106 between positions determined by the unique pairs of the second receptacles 158a-158e, the surgeon can increase or decrease the distance between the cutting slots 110 and 126 along the AP axis, which determines the amount of bone to be removed in the anterior and posterior portions of the patient's femur.

[0056] In certain embodiments, the three positions P1-P3 help the surgeon achieve a better press-fit between the implant and bone, which can be adjusted according to the differences in bone quality. More specifically, the press-fit between bone and implant depends on the frictional resistance between them. Greater frictional resistance between the implant and the bone (i.e., more press-fit) is needed if the patient has a soft bone (e.g., osteoporotic bone), and less resistance (i.e., less press-fit) is required for hard bone (e.g., sclerotic bone). On a patient having an osteoporotic bone, less bone in the anterior and posterior end is removed to ensure that when the final implant is fitted against the resected end of the femur, the implant tightly packs the soft bone to achieve good press-fit between the implant and the bone. If a patient has a sclerotic bone, less press-fit may be needed compared to a patient having a soft bone, generally, to prevent excessive force being applied to the patient's hard bone.

[0057] The positions P1-P3 provide a sizing guide for addressing different bone qualities. The position PI, as illustrated in Figure 5, corresponds to the line marked "+1" (e.g., for soft bone) noted by a position indicator line 180. Position P2 corresponds to the line marked "0" (e.g., no further adjustment) noted by a position indicator line 182. Position P3 corresponds to the line marked "-1" (e.g., for hard bone) noted by a position indicator line 184. Figure 5 shows the "+1," "0," and "-1" position indicator lines 180, 182, and 184 disposed on a bottom surface 166 of the base 102. Although the base 102 includes three positions P1-P3, the number of positions may vary by including any number of receptacles and defining any number of positions for adjusting the position of the guide blocks 104 and 106, as desired. Furthermore, each guide block may be adjusted independently to give an increased combination of incremental changes in the A-P distance between the cutting slots.

[0058] The first guide block 104 and the second guide block 106 also include position indicators that correspond to the position indicator lines 180, 182, and 184 to help the surgeon align the guide blocks with the appropriate receptacles on the base to achieve the desired sizing. As shown in Figure 6A, the guide blocks 104 and 106 have position indicators 186 and 188, respectively, disposed on the distal surfaces 128 and 170. The indicators 186 and 188 align with the "+1," "0," and "-1" position indicator lines 180, 182, and 184 on the base 102.

[0059] Figure 6A shows the position indicators 186 and 188 of the guide blocks 104 and 106 aligned with the "0" position indicator line 182 of the base 102. In this position, the first protrusions 146a and 146b of the first guide block 104 are engaged to the receptacles 156b and 156d of the base, respectively (position "P2"shown in Figure 5). In this case, the patient's bone quality is normal or otherwise acceptable and the surgeon only wants to modify the finish cuts to match a specific type of femoral implant and does not need to account for bone that is, for example, osteoporotic or sclerotic. For example, the finish cuts needed for an implant with a porous sintered bead coating may differ from an implant having a rough porous plasma spray coating. The coating thickness and roughness can vary between the components, which can interfere with the quality of the press-fit engagement between the implant and the bone. The adjustable cutting guide 100 provides the surgeon the flexibility to account for such variations.

[0060] Figure 6B shows the position indicators 186 and 188 of the guide blocks 104 and 106 aligned with the position indicator line 180 of the base 102. In this position, less bone would be removed from the anterior and the posterior surfaces of the bone. Therefore, the first guide block 104 and the second guide block 106 are positioned with respect to the base 102 to remove less bone in this example by positioning the guide blocks 104 and 106 so they are further away from the center of the base 102, along the direction noted by arrows Bi and B₂, respectively. In this position position), the first protrusions 146a and 146b of the first guide block 104 are engaged in the first receptacles 156a and 156c of the base 102, respectively (position "PI" shown in Figure 5). The second protrusions 148a and 148b of the second guide block 106 are engaged in the second receptacles 158a and 158c of the base 102, respectively. Compared to the "0" position, the guide blocks 104 and 106 are positioned closer to the first side surface 116 of the base 102 and are spaced more outwardly in the direction denoted by arrows Bi and B₂. This is due to the angled interface between the mating surfaces 122 and 154 of the base 102 and the guide mating surfaces 150 and 152 of the guide blocks 104 and 106, as explained above. Both of the guide blocks need not be moved together to adjust the position of the cutting slots or be positioned at the same position line indicator. For example, one of the guide blocks could be positioned at the "0" position and the other guide block could be positioned at the position.

[0061] Because the base 102 has a greater width W₂ (Figure 6B) near the first side surface 116 compared to width Wi near the second side 118, the base positions the first guide block 104 outwardly along the angled mating surface 122 in the direction noted by Arrow Bi. The cutting guide 100 therefore has a greater AP dimension (APi) in the position compared to the "0" position. To further increase the AP dimension, the surgeon could move the first guide block 104 along the medial-lateral axis of the femur toward the first side surface 116, which is the direction of Arrow A_ls and then join the guide block 104 to the mating surface 122, as explained above. Movement in the direction of Arrow Ai positions the first guide block 104 outwardly in the direction of Arrow Bi. Similarly, moving the second guide block 106 with respect to the base 102 along Arrow A₂ positions the guide block 106 outwardly in the direction along Arrow B₂. By moving one or both of the first and second guide blocks 104 and 106 along the direction of Arrows Ai and A₂ (also along the medial-lateral axis of the femur) the surgeon can finely adjust the anterior-posterior distance (APi) between the two cutting slots 126 and 110. By thus positioning the guide blocks 104 and 106 closer to the first side surface 116 of the base 102 the surgeon increases the AP dimension between the two cutting slots and thereby resects less bone. In certain implementations, only one of the guide blocks may be configured to be releasably adjusted, and the other fixed to the base.

[0062] Figure 6C illustrates an embodiment of the adjustable cutting guide 100 where the cutting slots 126 and 110 of the guide blocks 104 and 106, respectively, are positioned closer to one another compared to the embodiments shown in Figures 6A and 6B, resulting in the cutting guide 100 having a smaller AP dimension (AP₂). The guide blocks 104 and 106 are engaged in the position, where the position indicators 186 and 188 are aligned with the position indicator line 184 of the base 102. The guide blocks 104 and 106 are locked in place by the first protrusions 146a and 146b engaged within the receptacles 156c and 156e (position "P3" shown in Figure 5), and the second protrusions 148a and 148b are engaged within the receptacles 158c and 158e. Compared to the or "0" positions, the guide blocks 104 and 106 are placed closer to the second side 118 of the base 102, along the direction noted by Arrow C, which positions the guide blocks closer to one another along the narrowing mating surfaces 122 and 154 of the base 102. AP dimension (AP₂) is thus less than APi of Figure 6B, thereby positioning the two cutting slots 126 and 110 closer together such that the resulting cuts resect more bone along the anterior and posterior bone surfaces.

[0063] As further illustrated in Figure 6C, the mating surfaces 122 and 154 extend along a continuous angle from a first side surface 116 to a second side surface 118 of the base 102. Alternatively, the mating surfaces 122 and 154 may include a terraced slope, step-like configuration or any other configuration as long as the mating surfaces accommodate the first and/or second guide blocks 102 and 104 and allow for a general tapering or narrowing that permits adjusting the AP dimension between the cutting slots 126 and 110 disposed on the cutting guide 100.

[0064] Various mechanisms are also contemplated to connect the base and at least one guide block. In certain implementations, a dove-tail or a T-slot mechanism is used to incrementally adjust the position of at least one guide block with respect to the base. Figures 7A and 7B show side and top views, respectively, of an exemplary adjustable cutting guide 200 having a base 202 and a first guide block 204 and a second guide block 206 that are slidably positionable with respect to the base 202. Figure 7A depicts the adjustable cutting guide 200 (a cross-sectional view of the guide) mounted on the end of a femur 224.

[0065] As shown, the guide blocks 204 and 206 include cutting slots 208 and 210, respectively, for receiving a cutting instrument such as a cutting blade or saw. The first guide block 204 fits with the base 202 by a first protrusion 212 that is slidably engageable with a first trough 216 of the base 202 along the length of the base 202 (along the double-headed Arrow A as shown in Figure 7B). The trough 216 is shaped such that it accommodates the shape of the first protrusion 212. As shown, the trough 216 includes sides 216a-216c that are structured to interface with sides 212a-212c of the first protrusion 212. Similarly, the second guide block 206 includes a second protrusion 214 that is slidably engageable with a second trough 218 of the base 202. The second trough 218 also includes sides 218a-218c sized and shaped to interface with sides 214a-214c of the second protrusion 214. The first and second protrusions 212 and 214 and troughs 216 and 218 form a dove-tail mechanism between the guide blocks 204 and 206 and the base 202 to allow the surgeon to adjust the AP distance ("AP_d") between the cutting slots 208 and 210.

[0066] As shown in Figure 7B, the base 202 includes a first side 230, a second side 232, and first and second mating surfaces 234 and 236 that extend between the first and second sides 230 and 232, respectively. The first and second mating surfaces 234 and 236 are angled such that width "W₂" near the first side 230 is relatively greater than width "Wi" near the second side 232. The first guide block 204 includes a first mating surface 238 and the second guide block 206 includes a second mating surface 240. The first mating surfaces 238 is angled with respect to the cutting slot 208 of the first guide block 204 by the angle θι as shown in Figure 7B. Similarly, the second mating surface 240 is angled with respect to the cutting slot 210 of the second guide block 206 by the angle θ₂. The mating surfaces 238 and 240 of the guide blocks 204 and 206 are structured such that they abut and slide against the mating surfaces 234 and 236 of the base 202.

[0067] Adjusting the position of the guide blocks 204 and 206 with respect to the base 202 allows a surgeon to resect a variable amount of bone in the anterior and posterior end of the femur. The surgeon slides the guide blocks 204 and 206 (having cutting slots 208 and 210, respectively) along the medial-lateral axis of the femur in the direction denoted by the double-headed arrows A in Figure 7B. As the surgeon slides the guide blocks 204 and 206 toward the first side 230, because the base 202 has a greater width "W₂" near the first side 230 compared to the width "Wi" near the second side 232, the base 202 positions the guide blocks 204 and 206 outwardly along the sloping mating surfaces 234 and 236, respectively, in the direction noted by arrows Bi and B₂. When this happens, sides 212a-212c of the first guide block 204 may interface with the corresponding sides 216a-216c of the first trough 216, which guides and holds the first guide block 204 within the first trough 216. Similarly, sides 214a-214c of the second guide block 206 may engage the corresponding sides 218a- 218c of the second trough 218. As shown in Figure 7B, the sides 212b and 214b of the first and second protrusions 212 and 214 extend substantially parallel to the first and second mating surfaces 238 and 240, respectively. Sides 212a and 212c of the first protrusion 212 and sides 214a and 214c of the second protrusion 214 similarly extend substantially parallel to the respective sides 216a and 216c of the trough 216 and sides 218a and 218c of the trough 218.

[0068] The protrusions 212 and 214 are structured to fit snugly yet securely within the troughs 216 and 218 to allow the surgeon to easily slide the guide blocks 204 and 206 with respect to the base 202. Once the surgeon adjusts the position of the guide blocks 204 and 206 to an appropriate position for achieving an ideal AP distance between the cutting slots 208 and 210, a locking mechanism (e.g., a locking screw) may be used to secure the position of the guide blocks with respect to the base.

[0069] In addition to illustrating various connection mechanisms, the implementation of Figure 7A illustrates how the cutting guide 200 fits with respect to a previously resected bone and provides for a more refined secondary cut. As shown, the first guide block 204 includes an outer cutting slot housing 220 and an inner cutting slot housing 222, and the cutting slot 208 is a channel formed within the cutting slot housings. The outer housing 220 extends past the anterior chamfer cut region (R) of the femur and therefore is relatively taller in height compared to the inner housing 222. In that configuration, the outer housing 220 extends past a portion (F) of the anterior cut 140a at the distal end of the femur, located above the anterior chamfer cut region (R), which allows the outer housing 220 to provide more guidance for the cutting blade as it passes between the outer housing 220 and the inner housing 222. The outer cutting slot housing 226 of the second guide block 206 extends similarly along a portion (F') of the posterior cut 142a at the distal end of the femur, located above the posterior chamfer cut region (R'). The added length of the outer housings 220 and 226 allow them to continue to guide the cutting blades while passing through the initial regions F and F', to help reduce deflection of the blade, particularly a fast moving cutting blade, which helps the surgeon make more accurate cuts. As also shown, the inner housing 222 on the anterior side is taller (height hi) than an inner cutting slot housing 228 on the posterior side (height h₂). Those heights are tailored so that the respective guide blocks 204 and 206 fit directly under the anterior and posterior regions of the bone within the previously made chamfer cut regions, which also improves cutting accuracy.

[0070] Figure 8 further illustrates guide blocks with different relative heights to align with anterior and posterior cut surfaces and with chamfer cut regions. As shown in a side view, the adjustable cutting guide 800 is mounted onto the end of a femur that has previously had an anterior surface cut 840, posterior surface cut 842, distal surface cut 844, anterior chamfer cut 836, and posterior chamfer cut 838. As illustrated, the chamfer face portion 834 of the base 802 abuts against the anterior chamfer cut 836 of the femur. The flat face portion 832 of the base 802 abuts against the distal cut 844 of the femur.

[0071] Similar to the guide blocks of Figures 7A and 7B, the guide blocks 804 and 806 of Figure 8 are sized at differing heights to more closely correspond with the differently sized preliminary chamfer cuts to the femur. The first guide block 804 includes a height hi that extends from a distal surface 828 to a proximal surface 830 of a cutting slot housing 890. The proximal surface 830 of the first guide block 804 is positioned near the distal portion 840a of the anterior cut 840. The cutting blade received within the cutting slot 826 is guided through height hi. In certain implementations, the first guide block 804 may be structured such that the cutting slot housing 890 extends past the distal portion 840a of the anterior cut 840, similar to the outer cutting slot housing 220 as shown in Figure 7A. The cutting slot housing 890 provides additional guidance to a moving blade, resulting in a more accurate bone cut.

[0072] The second guide block 806 includes a height h₂ that extends from a distal surface 868 to a proximal surface 872 of a cutting slot housing 892. The height h₂ is relatively smaller than hi, so the posterior guide block 806 is shorter than the anterior guide block 804. The different height of the two guide blocks 804 and 806 allows them to fit so that the cutting blades are positioned near the femoral area above the respective chamfer cuts 836 and 838, thereby producing more finely sculpted surfaces for interfacing with the femoral implant, to improve the press-fit between the implant and the bone. A cutting blade received within the cutting slot 810 is guided through height h₂. In certain implementations, the heights hi and h₂ are selected such that a minimal gap exists between the proximal surfaces 830 and 872 of the first and second guide blocks 804 and 806, respectively. In certain implementations, the heights hi and h₂ are substantially equal, depending on the desired shape of the implant.

[0073] As illustrated in Figure 8, the heights hi and h₂ of the guide blocks 804 and 806 allow the adjustable cutting block 800 to be positioned adjacent the femur after the chamfer cuts 836 and 838 have already been made. The first and second guide blocks 804 and 806 (and the cutting slots 826 and 810) are positioned directly under the anterior cut surface 840 and the posterior cut surface 842, respectively. The cutting slots 826 and 810 act as physical guides for the cutting blades, keeping the blades in line with the bone longer and thereby producing more accurate cuts. In particular, the cutting slots 826 and 810 are positioned under the offset anterior and posterior surfaces 840 and 842, so the cutting blade needs only to travel through those surfaces and not through extraneous bone material that does not interface with the implant. The slot thus provides more guidance and better control of the blade, reducing deflection during cutting.

[0074] As noted above, cutting guides such as cutting guides 100, 200, 800 allow removal of the bone in small, adjustable, increments to better sculpt the bone to improve the fit between the implant and the bone. The use of a secondary cutting guide may also allow the surgeon more flexibility in cutting blade choice. In certain implementations, where only a small portion of the bone is to be removed, a thicker, more rigid saw blade can be used to further improve the accuracy of the finish bone cuts. A thick blade provides more accurate bone cut because it deflects less during use compared to a thinner blade, but when cutting a full-thickness kerf, it tends to generate more heat compared to a thinner blade, potentially contributing to thermal necrosis of the adjacent bone. For a finishing cut application, the amount of bone removed is less than the thickness of the blade which means less heat would be generated as a result of the cut. Furthermore, the cut surfaces are accessible to irrigation which can more effectively keep heat from building up in the adjacent bone, improving its viability.

[0075] An exemplary use of an adjustable cutting guide, such as guides 100, 200, or 800, will now be described. As noted earlier, the adjustable cutting guides described herein may be used to make more refined secondary cuts to improve the fit between the implant and the resected bone after a surgeon makes a set of preliminary cuts using a conventional cutting guide. After the preliminary cuts are made, a trial component is placed on the resected bone. When the surgeon is satisfied with the fit of the trial component, the implant is selected and the corresponding adjustable cutting guide, such as cutting guide 100, is assembled. In certain implementations, the size of the base, such as base 102, corresponds to the specific size of the final implant selected. In certain implementations, the specific guide blocks used are based on the size of the base selected (i.e. certain guide blocks are designed to be used with a certain range of base sizes). Speed pins may be used to secure the base to the end of the femur. In certain embodiments, the spacing of the pins to secure the base matches the spacing of the pins on previous instruments used to make the primary cuts, so that the pins for the finishing block can be positioned in the same holes that were drilled for the previous instruments.

[0076] The surgeon adjusts the position of the first and/or second guide blocks 104 and/or 106 to various positions (e.g., PI, P2, P3 as shown in Figure 6A-6C) as desired to cut an appropriate amount of the anterior/posterior portions of the bone. With reference to cutting guide 100, the position of the first and/or second guide blocks 104 and/or 106 may be adjusted in the direction noted by arrows A and C and Figures 6B-6C by moving the guide blocks 104 and 106 along the medial-lateral axis of the femur. After the positions of the guide blocks 104 and 106 are finalized, a cutting saw is inserted through the cutting slots 126 and 110 for cutting the anterior surface cut 140 and the posterior surface cut 142,

respectively. The adjustable cutting block 100 is removed and the final femoral component is implanted. If the fit is too tight, a surgeon can remove the final femoral component and remount the adjustable cutting block 100 to remove slightly more bone, further refining the shape of the bone to improve the press-fit between the implant and the bone. After the surgeon achieves a desired press-fit, the adjustable cutting block is disassembled. In certain implementations, the base 102 is discarded and the first and second guide blocks 104 and 106 are retained for sterilization and re-use. A similar method may be used with the cutting guides 200 and 800. [0077] A kit for use in a knee surgery may be provided which includes, for example, reusable first and/or second guide blocks (e.g., 104 and/or 106 as shown in Figure 2) and a disposable base (e.g., base 102 as shown in Figure 2). The kit may also include one or more of a conventional femoral cutting guide, a cutting blade, and a femoral trial and implant.

[0078] In certain implementations, the kit includes more than one base 102 of the adjustable cutting block 100 and each base 102 is sized and shaped to match an individual implant size. For example, if there are nine different femoral implant sizes, nine bases 102 (sizes 1-9), sized according to respective femoral implant sizes, would be provided. These bases 102 may be disposable or reusable. Once the final implant size and the matching base 102 are selected, the first and the second guide blocks 104 and 106 are assembled to the base 102 as shown in Figure 3. In certain implementations, the guide blocks 104 and 106 are constructed such that they are compatible with multiple base 102 sizes, thereby reducing the inventory of bases required. At least one of the guide blocks 104 and 106 is modular. As an example, three different pairs of the guide blocks 104 and 106 (sized small, medium, and large) may be provided to accommodate nine differently sized bases 102. In that example, the small set of guide blocks 104 and 106 are used with the smallest three bases 102 (sizes 1-3), the medium set of guide blocks are used with the middle three bases 102 (sizes 4-6), and the large set of guide blocks are used with the bases 102 sized from 7-9. In certain implementations, the set of guide blocks 104 and 106 overlap such that small set of guide blocks 104 and 106 are used with bases 102 (sizes 1-4), the medium guide blocks 104 and 106 are used on bases 102 (sizes 3-7), and the large guide blocks 104 and 106 are used on bases 102 (sizes 6-9).

[0079] In certain implementations, the guide blocks 104 and 106 are used interchangeably between different knee systems. For example, the same guide blocks 104 and 106 could be used with the appropriate base 102 to make the finish cuts for both a size 3 Legion PS (Smith & Nephew, Inc.) component and a size 8 Profix C (Smith & Nephew, Inc.) component, thereby minimizing the amount of added inventory required and added cost of implementing such a system. In certain implementations, depending on the condition to be treated or surgeon preference, the base 102 may be used with only one of the guide blocks. The base 102 may also be adapted to receive two differently sized guide blocks. More specifically, on the anterior side, the base 102 may receive a small sized guide block 104 and on the posterior side, the base 102 may receive a medium sized guide block 106, or vice versa. The configurations described herein are merely illustrative; the systems may include any number of bases and guide blocks for providing an ideal press-fit between the implant and the femur. For extreme soft and hard bone cases, modified bases having a larger AP dimension (for soft bone) and a smaller AP dimension (for hard bone) may be provided. This modified base may be used when the guide block is positioned too close to the end surfaces of a base (e.g., first and second surfaces 116 and 118 of base 102) such that the engagement between the guide block and the base is unstable.

[0080] As discussed above, knee implants may be cemented or cementless depending on the type of fixation used to hold the implant in place. Cementless designs rely on bone growth into the surface of the implant for fixation. Most implant surfaces are textured or coated so that the new bone actually grows into the surface of the implant. For example, the bone-contacting surface of the implant may be modified by coating the surface with hydroxyapatite, a bioactive surfacing agent that will ultimately bond as the bone grows into it. Screws or pegs may also be used to stabilize the implant until bone ingrowth occurs. The advantage of a press-fit implant is that over time, the bone holds solidly to the implant, lessening the chance of the implant becoming loose. The press-fit between an implant and the bone varies greatly with relatively minor changes in the offset between the bone and the implant.

[0081] Figure 9 shows a side elevation view of an illustrative femoral implant 300. As shown in Figure 9, for example, the femoral implant 300 includes an anterior portion 302, a posterior portion 304, and a distal portion 306. The femoral implant 300 is placed onto a prepared (i.e., resected) patient's femur with the anterior portion 302 mating with the anterior cut of the femur, and the posterior portion 304 mating with the posterior cut of the femur and proximate to the condyles of the femur. The distal portion 306 mates with the distal and chamfer cuts of the femur. In certain embodiments, the inner bone-contacting surface of the femoral implant 300 include a porous coating 308. The porous coating 308 can be provided on substantially the entire inner bone-contacting surface or on any portion thereof. The porous coating 308 can provide a relatively greater surface area for receiving cement in embodiments where the implant is cemented to the bone. In other embodiments, and as will be described below, the porous coating 308 is preferably provided to allow for bone ingrowth, for example, in implementations where the femoral implant is press-fit onto the bone.

[0082] Figure 10 shows a schematic cross-sectional view of an illustrative interface between the femoral implant 300 of Figure 9 and a patient's femur. In particular, the schematic cross-section 310 includes a metallic region 312 having a porous coating 314 applied thereto. The porous coating 314 interfaces with the bone 316 and allows for ingrowth of the bone 316 into the spaces and voids disposed in the porous coating 314. The ingrowth of the bone 316 into the porous coating 314 strengthens the fit between the implant and the bone.

[0083] Figure 11 shows an illustrative flow chart for providing a cutting block component according to certain embodiments. At step 320 an implant may be provided. The implant may be any suitable type of orthopedic implant and may be a patient-matched implant or may be a conventional implant sized to fit some standard. Although the embodiments described herein relate primarily to orthopedic knee implants, it will be understood that any suitable type of implant, including hip, shoulder, or any other implant, may be used. Orthopedic implants are typically composed of a metal made of Titanium and Titanium-based or Cobalt Chromium-based alloys. However, the implant provided at step 320 can be composed of any suitable material, including stainless steel, Cobalt Chromium alloys, Titanium and Titanium alloys, Tantalum, polyethylene, Zirconium, Oxinium oxidized Zirconium, or other material or combinations thereof. The manufacturing processes for each implant will depend on the type of material or materials used. For example, the manufacturing processes will be limited by manufacturing tolerances of each material.

[0084] At step 330 a dimension of the implant is measured. The implant dimension is used to determine a cutting dimension for a patient's bone that provides a desired press-fit with the measured implant. In certain embodiments, the cutting dimension, based on the implant dimension, may be the distance between the anterior and posterior cuts on the end of the femur. The implant can be measured using a mechanical gage or various three-dimensional scanning technologies. One method of measuring the implant includes using an expandable anterior/posterior box gage, or "AP" box gage, in which the anterior and/or posterior surfaces are adjustable. The measuring device includes a mechanism for expanding the anterior and/or posterior surfaces and produces at least one output that can be used to create a cutting block component customized to the measured implant.

[0085] In certain embodiments, the expandable AP box gage is expanded using a screw adjustment like a vice with pressure feedback. For example, the screw can be manually or automatically adjusted until a particular pressure is obtained. Alternatively, or additionally, the gage can be expanded by pneumatic or hydraulic pressure. In certain embodiments, the anterior and posterior surfaces of the expandable AP box gage are provided at a fixed angle (e.g., matching the angle between the two surfaces on the implant) that provides information about the anterior/posterior dimension ("AP dimension") only. Alternatively, or additionally, there may be output measurements at multiple points that provide information about the AP dimension and any angular deviation between the two surfaces. In certain embodiments, the contacting surface of the expandable AP box gage is compliant to allow some interdigitation with the texture of a coating applied to the implant surface such as the porous coating 308 of Figure 9. In certain embodiments, the contacting surface of the expandable AP box gage can be rigid, thereby contacting only the outer peaks of the coating surface.

[0086] In certain embodiments, a method of measuring the implant consists of contacting each implant surface with an array of sliding measurement pins that provide multiple positional data points simultaneously on the surfaces of interest. Other ways to measure the implant include obtaining multiple positional data points sequentially on the surfaces of interest using, for example, a coordinate-measuring machine (CMM) instrument. Another similar alternative includes obtaining relative positional measurements of the implant surfaces of interest using laser, white light, or other contact or noncontact three-dimensional scanning technologies. In any of the above cases, the data could be used to calculate the relative location and orientation of the surfaces of interest.

[0087] At step 340 the measured implant dimension is evaluated against press-fit criteria. The press-fit criteria used may be standardized or may be customizable to a particular surgeon's preference either generally or for a specific surgical case. For example, a surgeon may prefer that an implant has a desired press-fit (measured, for example, in pounds force). The surgeon may provide press-fit criteria, which includes the desired press-fit (in pounds force or any other suitable metric), as well as patient bone quality data, or any other suitable data relevant to providing the desired press-fit such as a patient's age and weight. The bone quality data can include information on the relative hardness or softness of the patient's bone. The bone quality data can be used, for example, to determine a cutting dimension that provides the desired press-fit for the measured implant. In certain embodiments, the surgeon may have a preferred level of press-fit between the implant and the bone cuts such that, for example, the implant is 1 mm smaller than the corresponding bone cuts, and may include that information in the press-fit criteria. Based on the measured size of the implant and the press- fit criteria, a cutting dimension may be determined that provides the desired press-fit for the measured implant. The output of the evaluation step 340 is a cutting dimension that is larger than the corresponding implant dimension on the specific measured implant, such that the implant has the desired press-fit.

[0088] The press-fit criteria, for example, provided by the surgeon or determined by using standardized press-fit criteria, can be provided to a manufacturing facility that produces a cutting block component matched to each measured implant. If the press-fit criteria are standardized (i.e., not specific to a particular surgeon's preferences), a cutting block component can be packaged along with the implant among regular undesignated inventory. In certain embodiments, the same manufacturer that produced the implants can also manufacture the cutting block components that are matched (or sometimes referred to herein as "box-matched") to the respective implants, although this is not always the case. The press- fit criteria can be provided to the manufacturing facility, or any other third party, for example, by telephone or over the Internet, or by any other suitable means. In certain embodiments, the manufacturing facility can save the preferences of various surgeons on file and can access this information to provide a cutting block component matched to a particular implant.

[0089] At step 350 a cutting block component can be provided based on the evaluation. As defined herein, a "cutting block component" includes finishing blocks, primary blocks, or other components or sub-components of cutting blocks such as, for example, the guide blocks described above. The cutting block component is provided based on the evaluation and the cutting block is matched to the measured implant. The cutting block component has a cutting dimension that is based on the measured implant dimension and the press-fit criteria.

[0090] Figure 12 shows side elevation views of various illustrative gages for measuring an implant dimension. As discussed above at step 330 of Figure 11, a mechanical gage can be used to measure an implant dimension. The measuring system 360 of Figure 12 includes a gage 362 having an expanding portion 366 into which a screw 364 is positioned and then adjusted in order to expand the gage 362 along an anterior/posterior dimension of the femoral implant 368. The femoral implant 368 includes a porous coating 369. In certain

embodiments, the gage 362 includes implant-contacting surfaces, such as first and second surfaces 361 and 363, that have a compliant surface to allow interdigitation with a texture of the porous coating 369 of the femoral implant 368. This can prevent damaging or otherwise causing wear to the surface of the porous coating 369.

[0091] Measuring system 370 of Figure 12 includes a gage having a first gage portion 372 and a second gage portion 374. The first and second gage portions 372 and 374 mate along an angled interface 376. The second gage portion 374 is displaced along the direction shown by the arrow of Figure 12 until the second gage portion 374 is stopped against an inner surface of the femoral implant 378. Similar to the implant 368 described above, the implant 378 can include a porous coating 379. Either the first gage portion 372 or the second gage portion 374, or both, can include an implant-contacting surface that is compliant to the surfaces of the implant to allow interdigitation with the texture of the implant.

[0092] Figure 13 shows a side elevation view of an illustrative gage for measuring an implant dimension. The measuring system 380 of Figure 13 includes a first gage portion 382 and a second gage portion 384 coupled by a mechanical expanding linkage 383. An insert 386 is provided that, when positioned between the first and second gage portions 382 and 384, expands the gage portions relative to one another until the gages stop against surfaces of the femoral implant 388 which, as described above, can include a porous coating 389 to which surfaces of the first gage portion 382 or the second gage portion 384, or both, are matched. It will be understood that any suitable mechanical gage can be used to measure an implant dimension. For example, in some embodiments, calipers can be used and may be expanded until contacting any dimension of the implant.

[0093] Figure 14 shows a side elevation view of an illustrative implant and finishing cutting block that is matched to the implant. As shown in Figure 14, for example, a femoral implant 440 having a porous coating 442 may be provided. A finishing cutting block 410 has a cutting dimension that is matched to the femoral implant 440. In certain embodiments, the femoral implant 440 and the finishing cutting block 410 are provided together in a kit. The finishing cutting block 410 includes a first guide block 412 and a second guide block 414, each having respective cutting slots 416 and 418. The guide blocks 412 and 414 are coupled to a base 41 1. The finishing cutting block 410 can be used to make further cuts when a patient's femur has already been resected by a primary cutting block. The finishing cutting block 410 is placed against a resected surface of the femur 402. In certain embodiments, the finishing cutting block 410 includes bone contacting surfaces 420, 422 and 424 that match the resected portions, respectively, of the anterior chamfer cut, the distal cut, and the posterior chamfer cut of the femur 402.

[0094] The finishing cutting block 410 is matched to the femoral implant 440 by having a cutting dimension of length Li that provides a desired press-fit of the femoral implant 440, which has an implant dimension of length Li ', which may be relatively smaller than the length Li in order to provide the desired press-fit. The press-fit can be provided by producing a cutting block with a cutting dimension Li between approximately 0.1 mm to 2 mm greater than the measured implant dimension Li', although the cutting dimension is preferably between 0.5 mm to 1.0 mm greater than the measured implant dimension. The relative difference in size between the cutting dimension and the implant dimension can make a substantial difference on the press-fit of the implant. For example, where the offset is greater than approximately 2.0 mm, the press-fit can be more than 2,000 pounds.

[0095] The finishing cutting block 410 can be similar to the adjustable cutting guides described above. That is, first guide block 412 and second guide block 414 can be adjusted relative to the base 41 1 in order to vary the cutting dimension (length Li) of the finishing cutting block 410. For example, in some embodiments, the finishing cutting block 410 may have a plurality of positions at which the guide blocks 412 and 414 may be positioned.

Depending on the position of the guide blocks 412 and 414, the press-fit of the implant 440 can be adjusted in real time intra-operatively. For example, a surgeon might plan on having a certain press-fit prior to the operation. However, during the procedure, after the femur is resected, the surgeon may discover that parts of the bone are softer or harder than originally anticipated. If the cutting block 410 is provided with adjustable guide blocks, the press-fit of the implant can be adjusted in real time. This allows the surgeon to have multiple predetermined press-fits based on the adjustability of the cutting dimension.

[0096] The cutting blocks that are matched to the various implants do not have to be finishing cutting blocks. For example, Figure 15 shows a side elevation view of an illustrative implant and cutting block that is matched to the implant. The cutting block 510 of Figure 15 is a primary cutting block and can be used to make any suitable cut or combination of cuts. For example, the cutting block 510 includes a distal cutting slot 512, an anterior cutting slot 514, a posterior cutting slot 516, a posterior chamfer cutting slot 518, and an anterior chamfer cutting slot 520. Any combination of the cutting slots can be provided. The cutting block 510 may be patient-matched to the femur 502. In other embodiments, the cutting block may be a cutting block having a standard size. The cutting dimensions of one or more of the cutting slots may be determined in order to match the femoral implant 540. After the anterior, posterior, distal, and chamfer cuts are made, the femur is shaped to mate with the femoral implant 540. As shown in Figure 15, for example, the cutting block 510 has a cutting dimension along length L₂ that is matched to an implant dimension of length L₂' of the femoral implant 540, as measured in the anterior-posterior direction. Although the embodiments thus described refer an implant dimension along an anterior-posterior axis, it will be understood that any suitable implant dimension may be used. For example, in some embodiments, a dimension may be used along the posterior chamfer cut and the anterior chamfer cut, or any other suitable dimensions may be used.

[0097] As discussed above, an implant can be provided in a kit together with a cutting block. For example, a kit can include an implant having an implant dimension and a cutting block matched to the implant, the cutting block having a cutting dimension based on the implant dimension, where the cutting block is used to resect the patient's bone and provide a predetermined press-fit between the patient's bone and the implant. In certain embodiments, the kit can also include a gage for measuring the implant and providing an output that corresponds to the implant dimension. In certain embodiments, the kit may indicate the measured implant dimension for each implant. For example, packaging included in the kit may include the measured implant dimensions, or the implant dimension may be indicated on the implant itself. A method for resecting a patient's bone using a custom cutting block can include selecting an implant from a kit of a plurality of implants, selecting a cutting block component having cutting dimensions matched to a measured implant dimension of the implant and to press-fit criteria, and resecting a patient's bone using the cutting block component. In some embodiments, the surgeon may further adjust the press-fit by using an adjustable cutting guide rather than, or in addition to, the cutting block component matched to the implant. An implant can then be installed on the patient's resected bone, where the installed implant has a press-fit with the patient's resected bone within the press-fit criteria. In certain implementations measurement data is provided that corresponds to relative locations and orientations of the bone facing surfaces of an implant. The measurement data may be provided, for example, to a computer having processing means for analyzing the data. The measurement data can be analyzed against manufacturing tolerance data and press-fit criteria to determine a cutting dimension. This can be used to produce a cutting block component based on the determined cutting dimension.

[0098] The foregoing is merely illustrative of the principles of the disclosure, and the systems, devices, and methods can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation. It is to be understood that the systems, devices, and methods disclosed herein, while shown for use in knee systems, may be applied to systems, devices, and methods to be used in other surgical procedures including, but not limited to, spine arthroplasty, cranio-maxillofacial surgical procedures, hip arthroplasty, shoulder arthroplasty, as well as foot, ankle, hand, and extremities procedures.

[0099] Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems.

Moreover, certain features may be omitted or not implemented.

[0100] Examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made part of this application.

Claims

What is Claimed is:

1. A method for providing a custom cutting block component, the method comprising:

measuring an implant for an implant dimension;

evaluating the implant dimension against press-fit criteria; and

providing a cutting block component based on the evaluation, wherein the cutting block component has a cutting dimension based on the measured implant dimension and the press-fit criteria.

2. The method of claim 1, wherein the press-fit criteria comprises a desired press-fit and patient bone quality data.

3. The method of claim 2, wherein the evaluating comprises determining, based on the patient bone quality data, the cutting dimension that provides the desired press-fit.

4. The method of claim 1, further comprising:

inputting measurement data into a processor, the measurement data corresponding to relative locations and orientations of bone-facing surfaces on the implant;

analyzing the measurement data against manufacturing tolerance data and the press-fit criteria to determine a cutting dimension; and

producing the cutting block component based on the determined cutting dimension.

5. The method of claim 4, wherein the measuring further comprises:

placing a gage in contact with the implant, the gage having a first contact surface and a second contact surface; and

reading an output from the gage, the output indicating the implant dimension.

6. The method of claim 5, wherein the gage is an expandable anterior-posterior gage, the method further comprising expanding at least one of the first and second contact surfaces in an anterior or posterior direction.

7. The method of claim 6, wherein the gage is expanded using a screw

adjustment with pressure feedback.

8. The method of claim 6, wherein the gage is expanded using pneumatic or hydraulic pressure.

9. The method of any of claims 5-8, wherein at least one of the first and second contact surfaces has a compliant surface to allow interdigitation with a texture of the implant.

10. The method of any of claims 1-8, wherein the measuring further comprises obtaining a plurality of positional data points on bone-facing surfaces of the implant.

11. The method of claim 10, further comprising contacting each surface of the implant with an array of sliding measurement pins to provide the plurality of positional data points.

12. The method of claim 10, further comprising obtaining the plurality of positional data points using a CMM-type instrument.

13. The method of claim 10, further comprising obtaining the plurality of positional data points using laser or white light scanning.

14. The method of any of claims 1-8, wherein the press-fit criteria is met by producing the cutting block with a cutting dimension between approximately 0.1 mm to 2.0 mm greater than the measured implant dimension.

15. The method of claim 14, wherein the cutting dimension is approximately 0.5 mm to 1.0 mm greater than the measured implant dimension.

16. The method of any of claims 1-8, wherein the cutting block component is a cutting block insert having a cutting slot, the cutting block insert configured to mate with a cutting block.

17. The method of any of claims 1-8, wherein the cutting block component is a finishing cutting block used to make any of an anterior, posterior, chamfer, and distal cut.

18. The method of any of claims 1-8, wherein the cutting block component is a primary cutting block used to make any of an anterior, posterior, chamfer, and distal cut.

19. The method of any of claims 1-8, wherein the implant dimension is a distance along an anterior bone-facing surface of the implant and a posterior bone-facing surface of the implant.

20. A method for resecting a patient's bone using a custom cutting block component, the method comprising:

selecting an implant from a kit of a plurality of implants;

selecting a cutting block component having cutting dimensions matched to a measured implant dimension of the implant and a press-fit criteria;

resecting a patient's bone using the cutting block component; and

installing the implant on the patient's resected bone, wherein the installed implant has a press-fit with the patient's resected bone within the press-fit criteria.

21. A kit with orthopedic surgery components, comprising:

an implant having an implant dimension; and

a cutting block matched to the implant, the cutting block having a cutting dimension based on the implant dimension, wherein the cutting block guides resection of the patient's bone and has a plurality of configurations that provide pre-determined levels of press-fit between the patient's bone and the implant.

22. The kit of claim 21, further comprising:

a gage for measuring the implant and providing an output that corresponds to the implant dimension.