Assembled Cartilage Repair Graft

Abstract

Bifunctional and assembled implants are provided for osteochondral implantation.

Description

BACKGROUND OF THE INVENTION[0001]Focal articular cartilage defects of the knee are not uncommon consequences of injuries from sports, work or activities of daily living. Arthroscopic studies have estimated the occurrence of near full thickness lesions, full thickness lesions or full thickness with boney involvement lesions greater than 1 cm2 to be in the range of 6% of all surgical procedures in the knee. These types of articular cartilage defects may cause pain, swelling and / or knee locking and thus diminish the individual's overall quality of life. The size (area dimensions), depth (partial cartilage tissue to boney involvement), containment, co-morbidities (e.g., ACL tear, meniscal tear, and malalignment) and region of a defect will influence the procedure used by surgeons. Currently, for focal defects smaller than (<) 2.5 cm2, the subject and surgeon have few options: debridement (chondroplasty), marrow stimulation (micro-fracture, abrasionoplasty, or subchondral drilling), o...

AI Technical Summary

Benefits of technology

[0005]A bifunctional implant is particularly beneficial in the treatment of osteochondral defects in an articulating cartilage joint surface. An osteoconductive portion of the implant provides proper physical properties for implantation and anchoring of the implant while promoting the ingrowth and healing of the underlying subchondral bone tissue. An osteoconductive portion further provides the proper biomechanical properties to support and maintain the implant during remodeling, including sufficient porosity (or permeability), strength and stiffness approximating those of native subchondral bone. A chondroinductive portion provides the proper physical properties to support anatomical loads and maintain integrity of the joint while promoting the ingrowth and healing of native cartilaginous tissue. A chondroinductive portion further provides the proper biomechanical properties to support and maintain the implant during remodeling, including sufficient porosity (or permeability), strength and stiffness approximating those of native cartilaginous tissue.

[0008]In another aspect of the present invention an implant adapted for implantation at an articulating cartilage site is provided, having a perforated membrane of demineralized cortical bone. The membrane defines a plane by the membrane's length and width (its longer dimensions). The membrane includes natural Haversian canals oriented in the plane of the membrane. Natural Haversian canals oriented generally parallel to or at an oblique angle to the plane of the membrane may advantageously provide transport, signaling, and growth pathways between or in addition to any added perforation, canals or other features to support ingrowth, chondroinduction and chondroconduction.

[0015]The present implants have been shown to produce a particularly preferred embodiment with a combination of assembled elements including a substantially cylindrical chondroinductive portion, having at least one substantially flat, smooth or rounded end surface, assembled from two pieces of chondroinductive demineralized cortical bone, alternatively assembled from three or four pieces of chondroinductive demineralized cortical bone. The pieces of demineralized cortical bone are preferably substantially similar, mirrored, or radially symmetric with respect to each other. Alternatively, a single piece of substantially cylindrical chondroinductive demineralized cortical bone, preferably having at least one substantially flat, smooth or rounded end surface, may be used effectively, especially when producing smaller size implants, wherein the chondroinductive demineralized cortical bone piece is preferably radially symmetric or symmetric about a plane passing through its center axis, or both.

[0018]A further advantage of this embodiment, especially when an assembled chondroinductive portion is used, is that the negatively tapered shaft and bore fit provides solid and secure assembly wherein the at least two pieces of chondroinductive demineralized cortical bone are in direct contact with each other and are completely or partially surrounded over at least a part of their surface at the hydration controlled interference fit interface by a piece of osteoconductive cancellous bone.

[0019]An advantage of the assembly methods, and especially of the hydration controlled interference fit or hydration controlled shrink fit, is that the assembled implants are suitable for implantation at an osteochondral site in a human or other mammal without additional internal fasteners or connective elements such as press fit pins, bone pins, sutures, or adhesives. In addition to requiring excess material and additional processing steps, these other fasteners or connective elements add extra cost and complications to the design, manufacture and use of the implants. A preferred embodiment of the present invention provides an assembly that does not comprise separate fasteners or adhesive for holding together the implant.

[0020]Alternatively, certain embodiments of the present implants provide an assembly including additional internal fasteners or connective elements such as press fit pins, bone pins, sutures, or adhesives. These additional external fasteners may be employed either in conjunction with or in place of a hydration controlled interference fit to provide additional strength or reinforcement, or to provide additional elements such as growth factors, cells or specific scaffold materials to promote healing, chondroinduction, osteoinduction or osteoconduction.

Problems solved by technology

These types of articular cartilage defects may cause pain, swelling and / or knee locking and thus diminish the individual's overall quality of life.

While these procedures show significant rates of clinical success in the short and medium term, they each have limitations ranging from the quality of the cartilage repair to the cost and complexity of surgical procedures.

Additionally, some of the procedures themselves create defects (i.e. OATS) either as a direct result of the primary procedure or through second site morbidity caused by the recovery of the patient's own tissue.

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