Abstract:
A method for repairing defects in bones that may be used to remove a surface defect from the articulating surface of a bone. In one embodiment, a passage is formed in the bone and extending to an articulating surface of the bone, resulting in the removal of bone stock from the bone. By aligning the passage to intersect with the defect in the bone, the creation of the passage itself results in the removal of the defect from the articulating surface of the bone. A biocompatible material may then be inserted through the passage to replace the removed bone stock and may be formed to substantially replicate the shape of the articulating surface of the bone.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to methods for repairing defects in bones. 
         [0003]    2. Description of the Related Art 
         [0004]    Articular joints, such as the hip and knee joints, are comprised of two, opposing bones that articulate relative to one another. If one of the bones of an articulating joint becomes damaged, a person may experience pain during joint articulation. For example, a surface defect, such as a focal defect, may occur in the articulating surface of one of the bones forming the joint. The surface defect may be severe enough that the resulting pain requires the person to undergo a total joint arthoplasty. 
         [0005]    As an alternative to performing a total joint arthoplasty, the exterior of the damaged bone may be resurfaced. In order to resurface a bone forming an articulating joint, the joint is exposed and the bones forming the joint are separated. For example, to repair a defect on the surface of a head of a femur, the hip joint is exposed and the head of the femur removed from the joint capsule. The defective portion of the femur may then be removed and a cap, such as a metallic cover, secured to the femur. The femur is then returned to the joint capsule and repositioned adjacent to the acetabulum. 
       SUMMARY 
       [0006]    The present invention relates to methods for repairing defects in bones. In one exemplary embodiment, the present invention may be used to remove a surface defect from an articulating surface of a bone. In this embodiment, a passage is formed in the bone and extending to an articulating surface of the bone, resulting in the removal of bone stock from the bone. By aligning the passage to intersect with the defect in the bone, the creation of the passage itself results in the removal of the defect from the articulating surface of the bone. A biocompatible material may then be inserted through the passage to replace the removed bone stock and may be formed to substantially replicate the shape of the articulating surface of the bone. In one exemplary embodiment, the bone is positioned directly adjacent to the opposing bone of the joint prior to insertion of the biocompatible material. This allows for the opposing bone to act as a form, which shapes the biocompatible material to match the articulating surface of the opposing bone. In this manner, the defective portion of the bone is removed and an articulating surface substantially replicating the natural anatomical surface of the bone is created. 
         [0007]    Advantageously, forming the passage through the bone, the need to remove the bone from the joint capsule is eliminated. As a result, the surrounding muscle or other ligamentous structures do not have to be resected to repair the defect. Further, by utilizing a passage formed within the bone itself, the need to expose the joint is eliminated. As a result, the procedure may be performed in a minimally invasive manner, allowing arthroscopes and other minimally invasive instruments to be utilized. This may reduce the recovery time of the patient and allow the surgeon to more easily and efficiently performance the underlying procedure. Furthermore, by utilizing the procedures of the present invention, a defect formed on the articulating surface of a bone of an articulating joint may be readily repaired without the need to undergo total joint arthoplasty. 
         [0008]    In one form thereof, the present invention provides a method for resurfacing a defect in a bone, including the steps of: forming a passage in the bone extending from a non-articular surface of the bone through the bone to an articular surface of the bone, the passage providing access into a joint space between the articular surface of the bone and an opposing bone; and inserting a biocompatible material through the passage from the non-articular surface of the bone to the articular surface of the bone, the biocompatible material substantially replicating a portion of the articular surface of the bone. 
         [0009]    In another form thereof, the present invention provides a method for resurfacing a defect in a bone, including the steps of forming a passage extending from a non-articular surface of the bone through the bone to an articular surface of the bone; positioning the articular surface of the bone in contact with an opposing bone; inserting a biocompatible material into the passage; and forming the biocompatible material against the opposing bone to shape the biocompatible material, wherein the shape of the biocompatible material substantially replicates the anatomical shape of a portion of the articular surface of the head of the bone. 
         [0010]    In yet another form thereof, the present invention provides a method for resurfacing a defect in a bone, including the steps of: forming a passage extending from a lateral aspect of the bone to an articular surface of the bone, the passage providing access to a joint space between the articular surface of the bone and an opposing bone; and inserting a biocompatible material through the passage from the lateral aspect of the bone to the articular surface of the bone, the biocompatible material substantially replicating at least a portion of the articular surface of the bone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a fragmentary, perspective view of a femur including a focal defect and a cross-section of an acetabulum cooperating with the femur to form a hip joint; 
           [0013]      FIG. 2  is a fragmentary cross-section of the hip joint of  FIG. 1  depicting a passage formed in the femur; 
           [0014]      FIG. 3  is a fragmentary cross-section of the hip joint of  FIG. 1  depicting a balloon and cannula positioned within the passage of the femur of  FIG. 2 ; 
           [0015]      FIG. 4  is a fragmentary cross-section of the hip joint of  FIG. 1  depicting the balloon of  FIG. 3  in an expanded position and a rod positioned adjacent thereto within the passage of the femur of  FIG. 2 ; 
           [0016]      FIG. 5  is a fragmentary cross-section of the hip joint of  FIG. 1  depicting a dehydrated hydrogel and a rod positioned within the passage of the femur of  FIG. 2 ; 
           [0017]      FIG. 6  is a fragmentary cross-section of the hip joint of  FIG. 1  depicting the hydrogel and rod of  FIG. 5  with the hydrogel in a rehydrated state; 
           [0018]      FIG. 7  is a fragmentary cross-section of the hip joint of  FIG. 1  depicting a passage according to another exemplary embodiment formed within the femur of  FIG. 1 ; 
           [0019]      FIG. 8  is a fragmentary cross-section of the hip joint of  FIG. 1  depicting articular cartilage and a rod positioned within the passage of the femur of  FIG. 7 ; 
           [0020]      FIG. 9  is a fragmentary, cross-sectional view of a hip joint depicting the passage of  FIG. 7  formed in the femur and a void formed in the acetabulum; and 
           [0021]      FIG. 10  is a fragmentary cross-sectional view of the hip joint according to  FIG. 9 , depicting biocompatible material positioned within the void in the acetabulum and within the passage in the femur. 
       
    
    
       [0022]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION 
       [0023]    Referring to  FIGS. 1-10 , an articulating joint is depicted in the form of hip joint  10 . While described and depicted herein with specific reference to a hip joint, the present invention may be utilized in conjunction with any articulating joint, such as a shoulder joint formed by a humerus and scapula where the head of the humerus articulates against the glenoid of the scapula, for example. Referring to  FIG. 1 , hip joint  10  includes femur  12  having shaft  14 , neck  16 , and head  18 . Head  18  includes articulating surface  20  configured for articulation with corresponding articulating surface  22  of acetabulum  24 . In a healthy hip joint, head  18  of femur  12  rotates within acetabulum  24  allowing for articulating surfaces  20 ,  22  to slide past one another. However, articulating surfaces  20 ,  22  may become damaged, causing a person to experience pain within hip joint  10 . For example, as shown in  FIG. 1 , defect  26 , such as a focal defect, may be formed in articulating surface  20  of head  18  of femur  12 . 
         [0024]    Referring to  FIG. 2 , defect  26  may be removed by forming passage  28  which is aligned to intersect with defect  26  ( FIG. 1 ). By aligning passage  28  to intersect with defect  26 , defect  26  is substantially removed during the formation of passage  28 . In one exemplary embodiment, a computer assisted surgery (CAS) system, for example, a robotic surgical system or haptic device, such as described in U.S. patent application Ser. No. 11/610,728, entitled AN IMAGELESS ROBOTIZED DEVICE AND METHOD FOR SURGICAL TOOL GUIDANCE, filed Dec. 14, 2006, the disclosure of which is hereby expressly incorporated herein by reference, is utilized to facilitate the alignment of passage  28  with defect  26 . 
         [0025]    In one exemplary embodiment, shown in  FIG. 2 , passage  28  includes expanded portion  30  formed within head  18  of femur  12 . The formation of expanded portion  30  allows for substantially all of defect  26  to be removed during the formation of passage  28  by enlarging the size of only a small portion of passage  28 , i.e., the portion of passage  28  near articulating surface  20 . As a result, more of the bone stock of femur  12  may be preserved. Passage  28  may be formed using a reamer, such as the reamers disclosed in U.S. patent application Ser. No. 10/721,808, entitled EXPANDABLE REAMER, filed Nov. 25, 2003 and U.S. patent application Ser. No. 11/243,7898, entitled EXPANDABLE FIXATION DEVICES FOR MINIMALLY INVASIVE SURGERY, filed Oct. 5, 2005, the entire contents of which are expressly incorporated by reference herein. In one exemplary embodiment, passage  28  is also configured to extend from a lateral aspect of femur  12 , such as greater trochanter  32 , to articulating surface  20  of head  18  of femur  12 . By forming passage  28  extending from a lateral aspect of femur  12  through articulating surface  20  of head  18 , access to joint space  34  between articulating surfaces  20 ,  22  is provided through passage  28 . 
         [0026]    Referring to  FIG. 3 , cannula  36  having balloon  38  extending therefrom may be inserted within passage  28 . Specifically, cannula  36  may be advanced within passage  28  to position balloon  38  within expanded portion  30  of passage  28 . With cannula  36  positioned as shown in  FIG. 3 , femur  12  is positioned with articulating surface  20  of head  18  in direct contact with articulating surface  22  of acetabulum  24 . In one exemplary embodiment, direct contact between articulating surfaces  20 ,  22  is achieved by a surgeon pressing head  18  of femur  12  into acetabulum  24  through manipulation of femur  12 . 
         [0027]    Biocompatible material  42  ( FIG. 4 ), such as bone cement or an articular material, may then be injected in the direction of arrow A of  FIG. 3  through cannula  36  and into balloon  38 . In other exemplary embodiments, biocompatible material  42  may include or be formed of a hydrogel, saline, autograft bone, allograft bone, and/or a polymer. Additionally, biocompatible material  42  may be injected in the fluid state or be combined with a fluid prior to injection. By injecting biocompatible material  42  as a fluid, biocompatible material  42  easily passes through cannula  36  and into balloon  38 . As balloon  38  is expanded by the increasing pressure of biocompatible material  42  being injected into balloon  38 , articulating surface  22  acts as a form to shape balloon  38 . As a result, a portion of the exterior surface of balloon  38  is shaped to substantially replicate the natural anatomical dimensions of articulating surface  20 , as shown in  FIG. 4 . Referring to  FIG. 4 , after a sufficient amount of biocompatible material  42  is injected into balloon  38  to sufficiently expand balloon  38  to fill expanded portion  30 , biocompatible material  42  is allowed to cure and solidify. The passage of time, exposure to ultraviolet light, or other means may be utilized to cure biocompatible material  42 , rigidly securing biocompatible material  42  within expanded portion  30  of passage  28 . 
         [0028]    Further, as shown in  FIG. 4 , cannula  36  may be removed from balloon  38  prior to or after the curing of biocompatible material  42 . To further fill passage  28  and add additional strength to femur  12 , additional biocompatible material  42  may be inserted within passage  28  until passage  28  is substantially entirely filled with biocompatible material  42 . In one exemplary embodiment, rod  44  ( FIG. 4 ) may be inserted within passage  28 . In one exemplary embodiment, rod  44  is sized to extend from a lateral aspect, such as greater trochanter  32 , of femur  12  to end  46  of balloon  38 . Rod  44  may be made at least in part of, and may be made entirely of, a highly porous biomaterial useful as a bone substitute and/or cell and tissue receptive material. A highly porous biomaterial may have a porosity as low as 55, 65, or 75 percent and as high as 80, 85, or 90 percent. An example of such a material is produced using Trabecular Metal™ technology generally available from Zimmer, Inc., of Warsaw, Ind. Trabecular Metal™ is a trademark of Zimmer Technology, Inc. Such a material may be formed from a reticulated vitreous carbon foam substrate which is infiltrated and coated with a biocompatible metal, such as tantalum, etc., by a chemical vapor deposition (“CVD”) process in the manner disclosed in detail in U.S. Pat. No. 5,282,861, entitled OPEN CELL TANTALUM STRUCTURES FOR CANCELLOUS BONE IMPLANTS AND CELL AND TISSUE RECEPTORS, the entire disclosure of which is expressly incorporated by reference herein. In addition to tantalum, other metals such as niobium, or alloys of tantalum and niobium with one another or with other metals may also be used. 
         [0029]    Generally, the porous tantalum structure includes a large plurality of ligaments defining open spaces therebetween, with each ligament generally including a carbon core covered by a thin film of metal such as tantalum, for example. The open spaces between the ligaments form a matrix of continuous channels having no dead ends, such that growth of cancellous bone through the porous tantalum structure is uninhibited. The porous tantalum may include up to 75%-85% or more void space therein. Thus, porous tantalum is a lightweight, strong porous structure which is substantially uniform and consistent in composition, and closely resembles the structure of natural cancellous bone, thereby providing a matrix into which cancellous bone may grow to provide fixation of rod  44  in the surrounding bone of femur  12 . 
         [0030]    Referring to  FIG. 5 , another exemplary embodiment is depicted having another biocompatible material positioned within expanded portion  30 . As shown, hydrogel  48  is attached to an end of rod  44  and inserted within passage  28  to position hydrogel  48  within expanded portion  30 . In one exemplary embodiment, hydrogel  48  is produced using polymer material such as polyacrylates (e.g. polymethacrylate, polyhydroxyethylmethacrylate (polyHEMA), and polyhydroxypropylmethacrylate), polyvinylpyrollidone (PVP), polyvinyl alcohol (PVA), polyacrylamides, polyacrylonitriles, polysaccharides (e.g. carrageenans and hyaluronic acid), polyalginates, polyethylene oxides (e.g. polyethylene glycol (PEG) and polyoxyethylene), polyamines (e.g. chitosan), polyurethanes (e.g. diethylene glycol and polyoxyalkylene diols), and polymers of ring-opened cyclic esters. As shown in  FIG. 5 , hydrogel  48  has been dehydrated and, as a result, the volume of hydrogel  48  is substantially decreased. Referring to  FIG. 6 , hydrogel  48  is shown after rehydration within the body of a patient. Rehydration of hydrogel  48  may be facilitated by irrigating the joint or through natural absorption of fluid from the human body. Once rehydrated, hydrogel  48  expands, increasing its volume to substantially entirely fill expanded portion  30  of passage  28 . Additionally, by inserting hydrogel  48  in its dehydrated form, hydrogel  48  is able to pass through the smaller portion of passage  28  and into expanded portion  30 . 
         [0031]    In one exemplary embodiment, shown in  FIG. 6 , articulating surfaces  20 ,  22  of femur  12  and acetabulum  24 , respectively, are placed in contact during the rehydration of hydrogel  48 . Alternatively, in another exemplary embodiment, joint space  34  is allowed to remain, creating a space between articulating surfaces  20 ,  22 . In this embodiment, hydrogel  48  may expand beyond the natural anatomical shape of articulating surface  20  of femur  12 . However, the compression of the portion of hydrogel  48  extending beyond the natural anatomical shape of articulating surface  20  of femur  12  may cause hydrogel  48  to wear down until hydrogel  48  has a shape substantially similar to the natural anatomical shape of articulating surface  20 . Advantageously, the compression of hydrogel  48  may result in the release of lubricating liquid into the joint space to facilitate the articulation of femur  12  and acetabulum  24  along articulating surfaces  20 ,  22 , respectively. 
         [0032]    Referring to  FIGS. 7-10 , passage  28  is formed without expanded portion  30 . In such embodiments, expanded portion  30  may be unnecessary due to a smaller size of defect  26 . Alternatively, the size of passage  28  may be increased to accommodate the entirety of an enlarged defect  26  without the need for expanded portion  30 . Referring to  FIG. 8 , rod  44  is depicted including another biocompatible material in the form of articular cartilage  50  secured thereto. Articular cartilage  50  may be a synthetic, biologics component engineered to substantially replicate the material properties of articular cartilage, for example. Alternatively, articular cartilage  50  may be articular cartilage removed from another portion of the patient&#39;s body, i.e., autograph, or may be articular cartilage removed from the body of another, i.e., allograft. Irrespective of the nature of articular cartilage  50 , articular cartilage  50  may be shaped to substantially replicate the natural anatomical structure of articulating surface  20 . Thus, by inserting articular cartilage  50  and, correspondingly, rod  44  into passage  28  and extending the same from the lateral aspect, for example, such as greater trochanter  32 , of femur  12  to femoral head  18 , articular cartilage  50  may be positioned to align with articulating surface  20  of femoral head  18  and to substantially replicate the natural anatomical shape of articulating surface  20 . 
         [0033]    Referring to  FIGS. 9 and 10 , a passage may formed in one bone of a pair of articulating bones, such as passage  28  formed within femur  12 , as described in detail above. Utilizing this passage, a void may be formed in the opposing bone of the pair of articulating bone. For example, referring to passage  28  formed within femur  12 , void  52  may be created within acetabulum  24  to treat an acetabular defect. To form void  52  within acetabulum  24 , a reamer or other bone shaping instrument, such as those described above with specific reference to passage  28 , may be inserted through passage  28  to contact acetabulum  24  and form void  52 . Once void  52  is formed within acetabulum  24 , biocompatible material  54  may be inserted through passage  28 , joint space  34 , and into void  52 . Biocompatible material  54  may be any of the biocompatible materials described above with specific reference to passage  28  and femur  12 . For example, biocompatible material  54  may be an injectable fluid that cures to form a solid that is retained within void  52  of acetabulum  24 . In one exemplary embodiment, after filling void  52 , the surgeon may then rotate femur  12  to move passage  28  away from void  52  and press a portion of articulating surface  20  of femur  12  against biocompatible material  54 . By pressing articulating surface  20  against biocompatible material  54 , articulating surface  20  acts to shape biocompatible material  54  to substantially replicate the shape of articulating surface  22  of acetabulum  24 . 
         [0034]    Once void  52  has been filled with biocompatible material  54 , passage  28  may be filled using any of the methods described herein. For example, in one exemplary embodiment, shown in  FIG. 10 , another biocompatible material in the form of metallic cap  56  is connected to one end of rod  44 . In this embodiment, rod  44  is inserted into passage  28  and metallic cap  56  aligned with articulating surface  20 . Metallic cap  56  may be configured to substantially replicate the natural anatomical shape of articulating surface  20  of femur  12 . In one exemplary embodiment, metallic cap  56  is a highly polished metal, such as cobalt chrome or a titanium alloy. 
         [0035]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.