Cross-Reference to Related Applications

[0001] This application claims the benefit of United States Provisional Application

Number 61/373,599 filed August 13, 2010, the disclosure of which is hereby incorporated by reference in its entirety.

Background

[0002] Hip replacement surgery often involves placement of a metal shell or cup in a patient's acetabulum and placement of a metal implant into the patient's femur. Prior to placement of the implants, the acetabulum and the proximal end of the femur are prepared to accommodate the implant. Preparation of the femur may include cutting, resurfacing or drilling through the femoral head and neck to prepare the bone to receive the implant component. Proper alignment of the tools used to prepare the femur is needed to ensure that the resulting bone and subsequent implant maintain proper alignment with the acetabulum or acetabular implant.

[0003] Tools used to prepare the femur are typically inserted and controlled freehand by a surgeon. Freehand alignment of tools around the femoral head and neck can be inconsistent and lead to implant complications. Current approaches to address this problem include using references such as pins and guide wires placed into the femoral head to provide a reference point for the alignment of preparation tools. While placement of a reference point ensures that subsequent tools will be aligned in a like manner, the reference or pin is also placed freehand. This can lead to complications as the freehand placement of the pin for reference relies on a surgeon's skill. If a surgeon places a reference improperly, all tools used with that reference will be aligned improperly and the subsequent implant may suffer. [0004] Some current approaches utilize guide blocks to improve the placement of a reference pin into the femur. A guide block including a channel through its center is placed by a surgeon onto the femoral head such that the channel is roughly aligned with an axis that passes through the femur roughly at an angle that the surgeon wishes to use as a reference. Current guide blocks do not secure adequately with the femoral head and neck and allow for wobbling or rotational movements that lead to inaccuracies in the alignment of the guide block channel. While the guide blocks give the surgeon a steady channel through which to drill a hole, the wobbling and rotational movement of the blocks can still lead to

complications from misaligned reference points and misaligned drill holes.

[0005] Cartilage and soft tissue surrounding the femur, especially surrounding the femoral head and femoral neck, can limit access to the femoral head and neck and lead to difficulty for placing a guide block on the femur. A surgeon can cut and remove the cartilage and soft tissue to gain clear access to the femur, but this approach does not preserve any of the native cartilage after implantation and can place a greater stress on implanted components. In addition, cartilage and bone are often difficult to differentiate from an MRI or other image taken of the hip joint. If there is more or less cartilage on the bone than is apparent from an MRI, a guide block that is designed to mate closely with the femur is unable to accommodate the cartilage and does not achieve the desired close mating interaction.

Summary

[0006] Disclosed herein are systems, devices, and methods for positioning a guide block on a femur for proper alignment by aligning a guide passage of a guide block with an axis that extends through a femoral head. Two portions of a guide block are coupled to align the guide passage and secure the guide block to the femoral head. Also included are systems, devices and methods for installing a guide block on a femur so that a knife or other cutting tip is pointed toward the cartilage or other soft tissue surrounding the femoral neck, to help provide a mating interface with the femoral neck without requiring extensive damage to or removal of the cartilage or soft tissue.

[0007] In some embodiments, a guide block that is securable to a femur includes a first portion configured to mate with a femoral head and having a guide passage and a second portion that is configured to mate with a femoral neck and couples to the first portion. Coupling of the first and second portions aligns the guide passage with an axis extending through the femoral head and secures the guide block to the femur.

[0008] In certain implementations, the guide block includes a coupling member that couples the second portion to the first portion. In certain implementations, the coupling member is a sleeve that mates with a first boss on the first portion and a second boss on the second portion. The first and second bosses may include threaded surfaces, and the sleeve may include an interior threading that is complementary to the threaded surfaces. The first and second bosses may include tapered surfaces, and the sleeve may include an interior tapering that is complementary to the tapered surfaces. The first and second bosses may include a groove, and the sleeve may include an interior rib that mates with the groove. In certain implementations, the guide block includes a pin that couples the second portion to the first portion.

[0009] In certain implementations, a surface of the first portion is contoured to match a surface feature of a patient's femoral head, and a surface of the second portion is contoured to match a surface feature of a patient's femoral neck. The axis extending through the femoral head is a desired patient-matched axis. The axis and the contoured surfaces of the first and second portions are defined based on a model of a patient's anatomy, and the axis may correspond to a natural axis of hip rotation. The model of the patient's anatomy is created using data from at least one of an X-ray, M I, and CT scan.

[0010] In some embodiments, a method of securing a guide block to a femur includes providing a first portion having a guide passage and coupling a second portion to the first portion. Coupling of the first and second portions aligns the guide passage with an axis extending through a femoral head and secures the guide block to the femur and secures the guide block to the femur.

[0011] In certain implementations, the method includes obtaining data from at least one of an X-ray, MRI, and CT scan and using the data to determine an appropriate axis. A computerized model of a patient's anatomy is created, and the axis is a desired patient- matched axis defined based on the computerized model. A pilot hole is drilled along the axis through the guide passage.

[0012] In some embodiments, a method of manufacturing a guide block includes receiving data associated with at least one of an X-ray, MRI, and CT scan, determining an axis extending through a femoral head based on the received data, defining a configuration of first and second portions of the guide block based on the received data and the axis, and producing the first and second portions according to the defined configuration.

[0013] In certain implementations, the method includes creating a model of a patient's anatomy and defining the axis based on the computerized model. A surface of the first portion is contoured to match a surface feature of a patient's femoral head, and a surface of the second portion is contoured to match a surface feature of a patient's femoral neck.

[0014] In some embodiments, a kit for a guide block includes a first portion that is configured to mate with a femoral head and has a guide passage and a second portion that is configured to mate with a femoral neck and couples to the first portion. Coupling of the first and second portions aligns the guide passage with an axis extending through the femoral head and secures the guide block to the femur.

[0015] In certain implementations, a surface of the first portion is contoured to match a surface feature of a patient's femoral head, and a surface of the second portion is contoured to match a surface feature of a patient's femoral neck. The axis extending through the femoral head is a desired patient-matched axis.

[0016] In some embodiments, a guide block that is securable to a femur includes a first portion contoured to match a surface feature on a femoral head and having a guide passage and a second portion that couples to the first portion and has a surface contoured to match a surface feature on a femoral neck. The second portion has a cutting element that extends radially from an interior surface of the second portion, and coupling of the first and second portions aligns the guide passage along an axis extending through the femoral head and disposes the cutting element toward the femur's femoral neck.

[0017] In certain implementations, the cutting element comprises a knife edge. In certain implementations, the cutting element comprises a plurality of spikes. The cutting element extends along an arcuate interior surface of the second portion, and the cutting element has a sharp tip to cut through cartilage surrounding the femoral neck. The cutting element extends in a direction substantially perpendicular to the axis when the first and second portions are coupled. In certain implementations, a coupling member couples the second portion to the first portion. [0018] In certain implementations, the contoured surfaces of the first and second portions are created based on data obtained from at least one of an X-ray, MRI, and CT scan. The data is used to create a computerized anatomical model, and the axis is a desired patient- matched axis defined based on the computerized anatomical model.

[0019] In some embodiments, an orthopedic surgical kit includes a first block portion having a first surface contoured to match a surface feature on a femoral head, a second block portion having a second surface and a cutting element that extends radially from the second surface, and an attachment mechanism that couples the first and second portions and, upon such coupling, couples the first portion to the femoral head and the cutting element to the femoral neck.

[0020] In certain implementations, the kit includes a pin that fits within receiving holes on the first and second portion. The kit includes a knife edge or spike, and a latch mechanism that adjustably couples the cutting element to the second portion. The kit also includes a user instruction that describes a process for installing the first and second block portions on a femur.

[0021] In some embodiments, a method of securing a guide block to a femur having a head and neck includes providing a first portion having a guide passage and matching the first surface configuration to a feature on the head, and coupling the first portion to a second portion having a cutting element. Coupling of the first and second portions aligns the guide passage with the head and points the cutting element toward the neck.

[0022] In certain implementations, the method includes positioning the second portion such that the cutting element passes through cartilage surrounding the femoral neck. The method includes positioning a pin in receiving holes on the first and second portions, thereby securing the first portion to the femoral head. The cutting element comprises one of a knife edge and a plurality of spikes.

[0023] In some embodiments, a method of manufacturing a guide block includes receiving data associated with at least one of an X-ray, MRI, and CT scan, identifying bone and cartilage portions of a patient's anatomy based on the received data, defining a configuration of first and second portions of the guide block, and producing the first and second portions according to the defined configuration. The configuration includes a cutting element on the second portion that is configured to pass through cartilage surrounding the patient's femoral neck.

[0024] In certain implementations, the cutting element comprises a knife edge, and the method includes defining a contour of the knife edge. In certain implementations, the cutting element comprises a plurality of spikes, and the method includes defining locations and sizes of the plurality of spikes.

[0025] 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.

A Brief Description of the Drawing

[0026] The foregoing and other objects and advantages will be appreciated more fully from the following further description thereof with reference to the accompanying drawings.

These depicted embodiments are to be understood as illustrative and not as limiting in any way:

[0027] Figure 1 shows an illustrative pelvic anatomy with an axis of hip rotation;

[0028] Figure 2 shows an illustrative cross-section of a femur with a reference channel drilled therethrough;

[0029] Figure 3 shows an illustrative two-piece guide block with a coupling member;

[0030] Figure 4 shows an illustrative cross-section of the guide block of Figure 3 coupled to a femur;

[0031] Figure 5 shows an illustrative cross-section of a two-piece guide block coupled to a femur;

[0032] Figures 6A-6C show illustrative mechanisms for attaching two portions of a two- piece guide block using a coupling member; [0033] Figure 7 shows an illustrative two-piece guide block having two portions;

[0034] Figure 8 shows an illustrative cross-section of the guide block of Figure 7 coupled to a femur;

[0035] Figure 9 shows an illustrative cross-section of a two-piece guide block coupled to a femur;

[0036] Figure 10 shows an illustrative cross-section of a two-piece guide block coupled to a femur;

[0037] Figure 11 shows an illustrative cross-section of a two-piece guide block including a direct connection interface coupled to a femur;

[0038] Figure 12 shows an illustrative cross-section of a two-piece guide block including a direct connection interface coupled to a femur;

[0039] Figure 13 shows an illustrative cross-section of a femur including cartilage around the femoral neck;

[0040] Figure 14 shows an illustrative portion of a two-piece guide block including a knife- edge for coupling with a femoral neck;

[0041] Figure 15 shows an illustrative cross-section of a two-piece guide block including the component show in Figure 14 coupled to a femur;

[0042] Figure 16 shows an illustrative component for a two-piece guide block including sharp protruding spikes for coupling with a femoral neck;

[0043] Figure 17 shows an illustrative cross-section of a two-piece guide block including the component shown in Figure 16 coupled to a femur;

[0044] Figure 18 shows an illustrative femur with articular cartilage;

[0045] Figure 19 shows an illustrative femoral knee cutting block including a sharp knife edge;

[0046] Figure 20 shows the illustrative cutting block of Figure 19 secured to the femur of Figure 18; and [0047] Figure 21 shows an illustrative femoral knee cutting block including a plurality of protruding spikes.

Detailed Description

[0048] To provide an overall understanding of the systems, devices and methods described herein, certain illustrative embodiments will now be described. For the purpose of clarity and illustration, the systems, devices and methods will be described with respect to orthopedic hip implants and resurfacing of a femoral head and neck prior to replacement. It will be understood by one of ordinary skill in the art that the systems, devices and methods described herein may be adapted and modified as is appropriate and may be employed in other suitable applications, such as for other types of joints and orthopedic implants. Such other additions and modifications will not depart from the scope hereof.

[0049] Figure 1 shows a patient's native pelvic anatomy with hip joints formed by the interaction of femoral head 100 and acetabulum 102. The ball-and-socket interface between the femoral head 100 and acetabulum 102 creates a rotating hip joint. During hip

replacement, it is often desirable to maintain the natural motion and rotation of a patient's hip after an artificial hip is implanted. This natural rotation is illustrated in Figure 1 by the axis 101 that extends outward from the cup of the acetabulum 102 through femoral head 100 and along femoral neck 104.

[0050] Prior to placement of a hip implant, portions of the femoral head 100 or femoral neck 104 may be prepared using one or more tools. Preparation tools may include drills, resurfacing tools, cutting tools or any other suitable tools. Accurate and consistent alignment of these tools relative to the femoral head 100 and the femoral neck 104 reduces

complications and leads to an improved implant. Alignment approaches described herein involve using a pre-identified axis or other aspect of the femur (or other bone) as a reference point, so as to orient the alignment tool relative to the bone in a proper alignment. In certain implementations, the operator uses the natural axis of rotation of the hip, shown by axis 101 in Figure 1. That axis 101 can be used as a reference point to orient tools and ensure consistent location and orientation for the tools with respect to the femoral head and neck. For some surgeries, portions of the femur 106, such as the bone mass 108, are removed to accommodate an implant. If multiple tools are needed to prepare the bone, for example to remove the bone mass 108, the axis 101 helps consistently align the tools and enhance the accuracy of cuts performed using those tools.

[0051] Placing the reference though the femoral head 100 helps align the tools with a desired axis, such as the axis 101. Figure 2 shows an illustrative cross-section of the femur 106 with a channel 110 drilled through the bone. The channel 110 is aligned along the axis 101 and thus serves as a reference for aligning tools consistently with the femur 106. A reference pin or other alignment component is placed in the channel 110 and used as a central axis to orient any subsequent tools. To help align any subsequent tools, the channel 110 is drilled through the femur 106 such that it aligns with the desired axis 101. A guide block may be utilized to accurately drill the channel 110 by coupling the block to the femoral head 100. The guide block is coupled to the femoral head 100 such that a guide passage of the guide block aligns substantially with the axis 101, thus providing a channel for drill placement to drill the channel 110 through the femur 106 along the axis 101. While the channel 110 in Figure 2 is a through hole passing through the bone, a blind hole that does not pass through the bone may also be drilled and used as an alignment channel.

[0052] The axis 101 is a desired patient-matched axis that is determined as a suitable reference point for the patient's anatomy. A surgeon obtains images of a patient's anatomy, for example by taking an MRI, and uses the image to define a reference point and reference axis relative to the anatomy that is a suitable guide for aligning tools with the femur. The surgeon may select the axis 101 as the desired reference based on the contours of the patients femoral neck and femoral head, the tools that are aligned with the axis and used to prepare the femur, the patient's natural axis of hip rotation, or any other suitable criteria. Once the surgeon defines the desired reference points and axis, the channel 110 is drilled along the axis 101.

[0053] A guide block can be patient-matched to specific contours of the femoral head 100 and the femoral neck 104 for a particular patient to facilitate a close mating and accurate alignment of the guide block for drilling the channel 110. To create a patient-matched guide block, a user obtains images or data for the patient's anatomy, such as the pelvic anatomy shown in Figure 1 , and uses the data or images to customize a guide block for a particular patient. For example, a surgeon may obtain an X-ray, MRI or CT scan of a patient's anatomy in order to identify features of the femoral head and femoral neck specific to that patient. In the anatomy shown in Figure 1 , the image is used to identify one or more contours on the surface of the femoral head 100 or the femoral neck 104 that are unique to a patient. The image data may also be used to identify the desired axis 101 relative to the femoral neck 104 and the femoral head 100. The data obtained from the image can then be used to create a customized guide block that will attach to the femur 106. The guide block will be formed with one or more surface characteristics that mate with and match, in a patient-matched specific configuration, with the one or more contours on the surface of the head or neck. The block contours to the one or more unique features of the femoral head 100 and femoral neck 104 such that when the block is fixed to the femur 106 it aligns a guide passage for drilling along the desired axis 101.

[0054] Figure 3 illustrates a patient-matched guide block configured to couple to a femoral head. The guide block 112 consists of a first portion 114 and a second portion 116 that are connected together by a coupling member 118. When the first and second portions 114 and 116 are placed on a femur and connected together by coupling member 118, the guide block 112 is secured to the femur such that it cannot be removed without first removing the coupling member 118. The guide block 112 is secured to a femur by the interaction of a number of arms, including arm 120 and arm 122, with a femoral head and a femoral neck of the femur onto which the guide block 112 is secured. When the two portions 114 and 116 are attached, the interior of boss 126 on the first portion 114 and boss 128 on the second portion 116 create a guide passage 124 that passes through the center of the guide block 112. The guide block 112 is designed and configured such that this guide passage 124 is aligned with a desired axis relative to the femoral head and femoral neck. Thus, the guide block 112 provides a reference through the guide passage 124 for accurately drilling along the desired axis.

[0055] The guide block 112 is coupled to a femur through interactions of multiple arms including arms 120 and 122 with the femoral head and femoral neck onto which the guide block 112 is placed. In particular, the arm 120 is configured to contour with and mate to a substantial portion of a femoral head and the arm 122 is configured to mate with and contour to a substantial portion of the femoral head and the femoral neck. The shape, orientation and interior surface of the arms is patient-matched to a specific patient's anatomy obtained from imaging data. For example, the interior bone-facing surfaces of arms 120 and 122 may include divots or protrusions to accommodate any unique features of the patient's bone anatomy. [0056] When the guide block 112 is used in surgery, the two portions 114 and 116 are placed in their respective positions on a femoral head and attached by coupling member 118 to secure the guide block 112 to the bone. Figure 4 shows the guide block 112 coupled to the femur 106 from Figures 1 and 2. The first portion 114 and second portion 116 of the guide block 112 are placed on the femur 106 and connected together by coupling member 118. As is shown in Figure 4, the arm 120 of the first portion 114 contours to and mates with a significant portion of the femoral head 100. Likewise, the arm 122 couples with a significant portion of the femoral head 100 and the femoral neck 104. Because of the patient-matched design of the guide block 112, the guide channel 124 is aligned relative to the femoral head 100 along axis 101 when the two portions 114 and 116 are coupled together. Notably, the coverage of a significant portion of the femoral head 100 and the contacts between arm 122 and the femoral neck 104 at contact point 130 couple the block 112 to the femur 106 such that removal of the block 112 is prevented while the two portions are connected by coupling member 118. This connection allows the block 112 to be coupled to the femur 106 and held tightly in place aligned with the desired axis 101 without requiring any extra pins or securement mechanisms to be drilled into the femoral head 100 or the femoral neck 104.

[0057] The patient-matched contours of the first portion 114 and the second portion 116 of the guide block 112 stabilizes the block against wobbling or rotation to maintain the guide passage 124 aligned with the axis 101. For example, protrusions or divots in the femoral head 100 or femoral neck 104 may be matched with corresponding divots or protrusions in the arms of the guide block 112 to provide adequate stability for the guide block 112. Thus, coupling of the first portion 114 and the second portion 116 with the coupling member 118 aligns the guide block 112 in proper orientation with the femur 106.

[0058] Contact of a guide block with a femoral neck may be increased to provide further stability when a guide block is coupled with a femur. Figure 5 shows a guide block 212 that provides an increased contact surface with the femoral neck 104 when coupled with the femur 106. The guide block 212 includes a first portion 214 and a second portion 216 connected by a coupling member 218. The first portion 214 includes an arm 220 that mates with a significant portion of the femoral head 100. The second portion 216 includes an arm 222 that mates with a portion with the femoral head 100 and the femoral neck 104. When the first portion 214 and the second portion 216 are attached by coupling member 218, a guide passage 224 is created by the boss 226 of the first portion 214 and the boss 228 of the second portion 216. The guide passage 224 is aligned along the desired axis 101 and thus provides a suitable guide for drilling through the femoral head 100. The arm 222 includes an extension 234 that mates with the femoral neckl04 along contact surface 232 to provide stability to the guide block 212. The contact between guide block 212 and the femoral 100 and the femoral neck 104 rotationally stabilizes the guide block 212 and decreases wobbling on the femur 106 to improve accurate and consistent alignment of the guide passage 224 with the axis 101.

[0059] The two-piece guide blocks shown in Figures 4 and 5 are held together by the interaction between a coupling member and bosses of two portions of the guide member. The interaction and connection between the bosses and the coupling member may include any suitable connection mechanism, including those shown in Figures 6A-6C. In Figure 6 A, bosses 326 and 328 of two portions of a guide block are held together by coupling member 318. The coupling member 318 includes a rib 336 that extends around an interior surface of the sleeve-shaped coupling member. Each of the bosses 326 and 328 has a corresponding groove 338 to receive the rib 336. When the two bosses 326 and 328 are placed together and the coupling member 318 slides over the bosses, the two bosses move slightly inward as the rib 336 moves down over the bosses. When the rib 336 reaches the groove 338, boss 326 and boss 328 snap outward and lock the coupling member 318 in place. The interaction between the rib 336 and the groove 338 thus maintains the bosses 326 and 328 in a tight configuration with the guide block.

[0060] Figure 6B shows another mechanism that connects portions of a guide block. Two bosses 426 and 428 include threads 438 on an exterior surface. The interior through-hole of the coupling member 418 has a complimentary threading 436 that mates with the threads 438 on the bosses 426 and 428. When the guide block shown in Figure 6B is attached to a femoral head, the bosses 426 and 428 are placed together and the coupling member 418 is rotated to screw on to the guide block. The interaction between the complimentary threading 436 and threads 438 connects the coupling member 418 and the bosses 426 and 428.

[0061] Figure 6C shows another mechanism that may be used to connect a guide block as two bosses 526 and 528 held together by a coupling member 518. Each of the bosses 526 and 528 includes a tapered exterior surface 536 and the coupling member 518 includes a complementary tapered surface 538 on the interior of the coupling member 518. When the guide block shown in Figure 6C is placed on a femur and the two bosses 526 and 528 are together, the coupling member 518 is placed onto the bosses 526 and 528. A downward force on a coupling member 518 pushes the coupling member down onto the bosses 526 and 528. Because of the complementary shapes of tapered surfaces 536 on the bosses and the tapered surface 538 of the coupling member, this downward force holds the two bosses 526 and 528 and the whole guide block together, thus orienting the guide block and the guide passage through the block with the femoral head onto which the guide block is coupled.

[0062] The guide blocks shown in Figures 4 and 5 include two portions that directly contact each other to create a substantially continuous guide block. In certain implementations, a two-piece guide block may be composed of two pieces that do not contact each other at all, such as the guide block 612 shown in Figure 7. The guide block 612 is a two-piece guide block that includes a first portion 614 and a second portion 616. The first portion 614 has a neck 640 that includes an interior guide passage 624. When the guide block 612 is coupled to a femur, the guide passage 624 provides a channel for placement of a drill into the femoral head on which the guide block 612 is placed. The first portion 614 also includes an interior surface 650 that mates with and contours to a significant portion of the femoral head onto which the guide block 612 is placed. The interior surface 640 includes patient-matched contoured portions 642 that correspond with unique contours of a particular patient's femoral head. The second portion 616 includes an interior surface 646 for mating with a portion of a femoral head and an interior surface 648 for mating with a portion of a femoral neck when the guide block 612 is coupled to a femur. The interior surfaces 646 and 648 include contoured portions 643 that correspond to unique areas of the patient's femoral head and femoral neck. When the first portion 614 and second portion 616 are placed in their designed location on the patient's femur, the receiving hole 644 on the first portion 614 aligns with the receiving hole 645 on the second portion 616. The two receiving holes 644 and 645 receive a connecting member, such as a pin, that couples the first portion 614 to the second portion 616.

[0063] Figure 8 shows the guide block 612 coupled with the femur 106 shown in Figures 1 and 2. The first portion 614 and second portion 616 are connected by a pin 652 which is placed into the receiving hole 644 of the first portion and the receiving hole 645 of the second portion. When the two portions 614 and 616 are coupled together, the interior surface 650 of the mating umbrella 620 of the first portion 614 mates with a substantial portion of the femoral head 100. Likewise, the interior surfaces 646 and 648 of the second portion 616 mate with the femoral head 100 and the femoral neck 104 at their designed location. In this orientation, the neck 640 and guide passage 624 are substantially aligned along axis 101, thus providing a passage for drilling through the femur 106 along the desired axis 101. In this implementation, the guide block 612 mates with the femoral head 100 and femoral neck 104 in a patient-specific configuration, with substantial contact that secures them together, such that the guide block 612 cannot be removed from the femur 106 without decoupling the first portion 614 and the second portion 616. Additionally, the substantial contact with the femoral head 100 and femoral neck 104 reduces wobbling and provides rotational stability that aligns the guide passage 624 with the desired axis 101.

[0064] While the second portion 616 of guide block 612 shown in Figure 8 mates with the femoral neck 104 along a lateral side of the femoral neck 104, similar guide blocks may also be utilized in which a portion of the guide block mates with a femoral neck 104 along a medial side. Figure 9 shows a guide block 712 coupled to femur 106and mating with a medial part of the femoral neck 104. The guide block 712 includes a first portion 714 that mates with a substantial portion of the femoral head 100 and a second portion 716 that mates with the femoral head 100 and femoral neck 104. The second portion 716 includes interior surfaces 746 and 748 that mate with medial surfaces on the femoral head 100 and femoral neck 104. The first portion 714 and second portion 716 are connected by a pin 752 that is coupled to receiving holes on the two portions. The interaction between the first portion 714 and second portion 716 with the femoral head 100 and femoral neck 104 maintain the guide block 712 with rotational stability such that the guide passage 724 is substantially aligned with the desired axis 101 extending through the femoral head 100. Thus, the guide block 712 provides a two-piece block that contacts a significant portion of the femoral head 100 and medial portions of femoral head 100 and femoral neck 104 to provide accurate and consistent alignment of a guide passage with the femur 106.

[0065] The two-piece guide blocks described above with respect to Figures 7-9 include a first portion that mates with the femoral head and a second portion that mates with both the femoral head and the femoral neck. In certain other implementations, a two-piece guide block includes a first portion that mates with only a femoral head and a second portion that mates with only a femoral neck. The guide block 812 shown in Figure 10 includes a first portion 814 and a second portion 816 connected by a pin 852. When the two portions are connected, an interior surface 850 of the first portion 814 mates with a significant portion of the femoral head 100. An interior surface 848 of the second portion 816 contours to and mates with a portion of the femoral neck 104. Notably, the second portion 816 does not couple with a substantial surface of the femoral head 100. When the guide block 812 is assembled in Figure 10, a neck 840 and interior guide passage 824 of the first portion 814 are substantially aligned along the desired axis 101 that passes through the femoral head 100. Additionally, the contacts between the interior surfaces 848 and 850 reduce wobbling and provide rotational stability for the guide block 812 while also preventing removal of the guide block 812 from the femur 106 without decoupling the first portion 814 and the second portion 816.

[0066] In certain implementations, two-piece guide blocks mate by direct interaction between two portions of the guide block without requiring a third component, such as a coupling member or a pin. Figure 11 shows a guide block 912 coupled to femur 106. The guide block 912 includes a first portion 914 and a second portion 916 that are connected together by an interaction between tapered points 954 on the second portion 916 and channels 956 on the first portion 914. The guide block 912 may be coupled to the femur 106 by positioning the second portion 916 along corresponding surfaces of the femoral head 100 and the femoral neck 104. The first portion 914 may then be lowered onto the second portion 916 such that the tapered points 954 pass through the channels 956. The tapered points 954 are designed such that they are able to compress radially inward as they pass through the channels 956 and then return to their original shape after the tapered points 954 are passed completely through the channels 956. Once the tapered points 954 are through the channels 956, the bottom shoulders 958 of the tapered points 954 resist movement of the second portion 916 back down through the channels 956. In this orientation, the guide block 912 is coupled to the femur 106 and cannot be removed until substantial force is applied either to the first portion 914 or the second portion 916 to force the tapered points 954 and shoulders 958 back through the channels 956. When the first portion 914 is coupled to the second portion 916, a guide passage 924 on the first portion 914 is aligned along the desired axis 101 that extends through the femoral head 100. Thus, the guide block 912 provides a direct connection mechanism that requires only the two pieces of the guide block 912 and not a third coupling component to maintain the guide block 912 along the desired axis 101.

[0067] Figure 12 shows another guide block 1012 including a direct coupling mechanism that allows for placement of a first portion 1014 on a femoral head 100 prior to placement of a second portion 1016. The first portion 1014 includes a channel 1056 that is configured to receive a tapered point 1054 from the second portion 1016. The tapered point 1054 is pliable to allow for radial compression of the tapered point 1054 to advance the tapered point 1054 into the channel 1056. Once the tapered point 1054 is advanced to the end of the channel 1056, the shoulders 1058 on the tapered point resist removal of the tapered point 1054 from the channel 1056, similar in function to the tapered points 954 discussed above with respect to Figure 11. When the first portion 1014 and second portion 1016 are coupled together, the guide passage 1024 on the first portion 1014 is maintained in substantial alignment with the desired axis 101 that extends through the femoral head 100. Accordingly, the guide block 1012 is maintained in a desired orientation with respect to the femur 106 until adequate force is applied to the second portion 1016 to remove the tapered point 1054 from the channel 1056.

[0068] Direct contact between guide blocks and a femur may be desirable. However, in certain implementations for a particular patient, cartilage around the femur, mainly around the femoral head and femoral neck, may make direct contact between a guide block and bone difficult to achieve. The presence of cartilage around a femoral head or neck may cause complications for guide blocks that are designed to couple specifically to a patient's bone. In addition, for image scans such as MRIs, the difference between bone and cartilage may be difficult to discern as the contrast of the two components on a scan may not be significantly different. In some approaches, any cartilage surrounding a femur may be cut away completely to provide access to the bone underneath. This approach, however, may not be desirable as maintaining the integrity of all or some of the surrounding cartilage is advantageous. Accordingly, guide blocks can be built and customized for a patient to include mechanisms for accommodating any cartilage surrounding the patient's bone anatomy.

[0069] Figure 13 shows a femur 206 with surrounding cartilage 205 that may cause problems for placement of a guide block. The femur 206 includes femoral head 200 and femoral neck 204. A significant amount of cartilage 205 is shown in Figure 13 surrounding the femoral neck 204. The cartilage 205 may be difficult to differentiate from the femur 206 in an MRI or other image scan. To reduce the amount of damage done to the cartilage 205 and to avoid the need to completely remove the cartilage 205 during surgery, a guide block can be designed to accommodate the cartilage 205 while still maintaining proper orientation with respect to the femoral head 200 and the femoral neck 204. [0070] Figure 14 shows a portion 1116 of a guide block that may be used to accommodate cartilage around a femur, such as the cartilage 205 shown in Figure 13. The portion 1116 includes an interior surface 1146 contoured to mate with a patient's femoral head and an interior surface 1148 contoured to mate with the patient's femoral neck. The interior surface 1148 includes a cutting element 1160, shown in Figure 14 as a sharp knife edge, which can be used to accommodate and pass through any cartilage that may be surrounding the femoral neck to which interior surface 1148 is designed to mate. The portion 1116 also includes a receiving hole 1145 for receiving a coupling member, such as a pin, and connecting the portion 1116 to a second portion of a two-piece guide block. Figure 15 shows a guide block 1112, which includes the portion 1116 shown in Figure 14, coupled to the femur 206. The guide block 1112 includes a first portion 1114 coupled to the second portion 1116 by a pin 1152. The interior surfaces of the first portion 1114 and second portion 1116 are configured to reduce wobbling and provide rotational stability while maintaining the neck 1140 and guide passage 1124 of first portion 1114 along the desired axis 201 that extends through the femoral head 200.

[0071] As shown in Figure 15, the cutting element 1160 of the second portion 1116 is able to pass through the cartilage 205 and contact the femoral neck 204 at a contact point 207. Thus, the cutting element 1160 enables the cutting block 1112 to contact the femoral neck 204 without requiring complete removal or extensive damage to the surrounding cartilage 205.

[0072] In certain implementations, the cutting element 1160 is integrally formed with the second portion 1116. In other implementations, the cutting element 1160 is removable, and the second portion 1116 provides a modular cutting block that can be used with or without the cutting elements 1160, at the surgeon's discretion. For a modular block, the cutting element 1 160 is adjustably fastened to the interior surface 1148 by a connection interface between the cutting element 1160 and interior surface 1148. The connection interface may be, for example, a latch mechanism, snap-fit interaction, or any other suitable connection between the cutting element 1160 and interior surface 1148. The surgeon presses or latches the cutting element 1160 onto the interior surface 1148 prior to placement of the guide block 1112 onto the femur. In certain implementations, a variety of cutting elements having different sizes and shapes are provided, and the surgeon selects a cutting element that suits particular needs of a certain application or patient. [0073] Other suitable guide blocks and cutting element arrangements may be used to accommodate cartilage surrounding a femur. Figure 16 shows a portion 1216 of a two-piece cutting block that includes a series of sharp spikes 1262 that extend inward from the interior of the portion 1216. The portion 1216 includes an interior surface 1246 connects to a femoral head and an interior surface 1248 connects to a femoral neck. In certain implementations, one or both of the interior surfaces 1246 and 1248 are contoured and configured to mate specifically, in a patient-matched configuration, to the patient's femoral head and femoral neck. The spikes 1262 that protrude from the interior surface 1248 enable the portion 1216 to contact the femoral neck through surrounding cartilage without require extensive damage or removal of the cartilage. Figure 17 shows a guide block 1212, which includes the portion 1216 shown in Figure 16, attached to the femur 206. The guide block 1212 includes a first portion 1214 coupled to the second portion 1216 by a pin 1252. When the first portion 1214 and second portion 1216 are coupled, the neck 1240 of the first portion 1214 and the guide passage 1224 are maintained substantially aligned with the axis 201 that extends through the femoral head 200. The sharp spikes 1262 of the second portion 1216 extend through the cartilage 205 without requiring complete removal or extensive damage to the cartilage 205 to contact the femoral neck 204. The sharp spikes 1262 contact the femoral neck 204 at a plurality of contact points 209. Thus, the guide block 1212 is able to maintain contact with a substantial of the femoral head 200 and the femoral neck 204 while maintaining some or most of the cartilage 205.

[0074] Joint cartilage can also cause complications for securing cutting guide blocks to the distal end of the femur or to the proximal end of the tibia during knee replacement surgeries. Similar to the cartilage around the femoral head and neck, the distal end of the femur is surrounded by cartilage that facilitates the rotating interaction between the femur and the tibia. Figure 18 shows a femur 1300 with articular cartilage 1302 on the distal end of the femur 1300. A patient-matched cutting block is used to provide a guide for cutting the femur 1300 during knee replacement surgery. The patient-matched block is contoured to match features of the femur 1300 and mate closely with the bone to hold a secure alignment of the block relative to the bone. A surgeon takes a scan, for example an X-ray, CT scan, MRI, or other scan, of the knee joint shown in Figure 18 prior to replacement to determine the design and orientation of the patient-matched block. The cartilage 1302 can be difficult to distinguish from the bone of the femur 1300 in the bone scan image. The cartilage 1302 also has a texture that is much more slippery than the bone and can make it difficult to accurately align and secure a block to the femur 1300. To reduce interference from the cartilage 1302 with a patient-matched block, the block is designed to accommodate the cartilage 1302 and maintain a secure interface with the bone of the femur 1300.

[0075] Figure 19 shows an illustrative cutting block 1310 designed to mate with the femur 1300. A slot 1312 passes through the block 1310 and serves as a guide for a cutting tool used to prepare the femur 1300 prior to placement of a femoral implant onto the bone. The block 1310 is designed such that the slot 1312 aligns with a desired cut plane through the femur 1300 when the block 1310 is secured to the femur 1300 by pins that pass through holes 1318 and into the bone. The desired orientation of the slot 1312 and the contours of the block 1310 are determined based on scans taken of the femur 1300, for example from X-ray, CT scan, or M I data.

[0076] The block 1310 includes an upper surface 1314 and a lower surface 1316 that are contoured to match the femur 1300. The upper surface 1314 has a sharp knife edge 1311 that passes through the cartilage 1302 and contacts the bone when the block 1310 is secured to the femur 1300. The block 1310 is shown secured to the femur 1300 in Figure 20. The interface between the knife edge 1311 and the bone provides a secure mating interface between the block 1310 and the femur 1300. By passing through the cartilage 1302 to reach the bone, the knife edge 1311 reduces complications that can arise when a block only contacts the slipper cartilage. In other implementations, the block 1310 includes a second knife edge on the upper surface 1314, or includes a knife edge on only the lower surface 1316, or includes knife edges on both of the surface 1314 and 1316.

[0077] In some implementations, cutting blocks incorporating cutting elements other than knife edges are utilized to guide a tool used to cut the femur or tibia at the knee. Figure 21 shows a cutting block 1320 that has a plurality of spikes 1321 protruding from bone-facing surfaces 1324 and 1326. The surfaces are designed to contour to a patient's bone such that the spikes 1321 pass through the cartilage 1302 and provide a secure mating interface between the block 1320 and femur 1300. The surfaces 1324 and 1326 are designed based on imaging data so that a slot 1322 in the block 1320 aligns with a desired cutting plane when the block 1320 is placed on the femur 1300 and secured by pins that pass through the holes 1328. [0078] It is to be understood that the foregoing description is merely illustrative and is not to be limited to the details given herein. While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems, devices and methods as well as their components may be embodied in many other specific forms without departing from the scope of the disclosure.

[0079] Variations and modifications will occur to those with skill in the art after reviewing this disclosure. The disclosed features may be implemented in any combination and subcombination (including multiple dependent combinations and sub-combinations) 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.

[0080] Examples of changes, substitutions and alterations are ascertainable by ones 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.