the term “ tissue ” is used in the general sense herein to mean any transplantable or implantable tissue , the survivability of which is improved by the methods described herein upon implantation . in particular , the overall durability and longevity of the implant are improved , and host - immune system mediated responses , are substantially eliminated . the terms “ transplant ” and “ implant ” are used interchangeably to refer to tissue , material or cells ( xenogeneic or allogeneic ) which may be introduced into the body of a patient . the terms “ autologous ” and “ autograft ” refer to tissue or cells which originate with or are derived from the recipient , whereas the terms “ allogeneic ” and “ allograft ” refer to cells and tissue which originate with or are derived from a donor of the same species as the recipient . the terms “ xenogeneic ” and “ xenograft ” refer to cells or tissue which originates with or are derived from a species other than that of the recipient . the present invention is directed towards a cartilage repair construct constructed of two separate pieces of allograft cancellous bone . both pieces of the two - piece allograft construct are to be derived from dense cancellous bone that may originate from proximal or distal femur , proximal or distal tibia , proximal humerus , talus , calceneus , patella , or iliium . cancellous tissue is first processed into blocks and then milled into the desired shapes . the top piece or cap member is substantially demineralized in dilute acid until the bone contains less than 0 . 2 % wt / wt residual calcium . subsequently , the resultant tissue form is predominantly type i collagen , which is sponge - like in nature with an elastic quality . following decalcification , the tissue is further cleaned and may also be treated so that the cancellous tissue is non - osteoinductive . this inactivation of inherent osteoinductivity may be accomplished via chemical or thermal treatment or by high energy irradiation . in a preferred embodiment , the cancellous cap member is treated with an oxidizing agent such as hydrogen peroxide in order to achieve a non - osteoinductive material . the bottom piece will be formed from mineralized cancellous bone or partially demineralized cancellous bone . the two piece allograft cancellous construct 20 has a base member 22 with a cap member 30 which is held fixed in place in the base member 22 by a pin . 40 . the base member 22 is preferably constructed of mineralized cancellous bone and is shaped in the form of a cylinder for easy insertion into bores cut into the patient to cut away cartilage defect areas . however , the base member 22 may be surface or partially demineralized or contain a region of cortical bone so that it is cortical / cancellous . the body of the base member 22 defines a blind bore 23 which holds a stem 36 of the cap member 30 , as further described below . the bottom surface 24 of the blind bore , as seen in fig5 - 7 , has a plurality of longitudinal through going bores 25 extending through the base member 22 and ending on the distal end surface 26 of the base member , which is preferably planar . the top surface 27 of the base member 22 is also preferably planar , forming a seat for the cap member 30 . a first lateral bore 28 extends generally transversely from an exterior wall of the base member 22 , above the bottom surface 24 of the blind bore 23 , and intersects the blind bore 23 . a second lateral bore 29 extends generally transversely from the exterior wall of the base member 22 , above the bottom surface 24 of the blind bore 23 , and intersects the blind bore 23 so as to be opposite the first lateral bore 28 ( see fig4 , 5 and 7 ) and in coaxial alignment therewith . a second plurality of longitudinal through going bores 31 are circumferentially positioned around the blind bore 23 parallel to the central axis of the base member 22 and extend from the top surface 27 to the bottom surface 26 . the longitudinal through going bores 25 and 31 have a smaller diameter than the blind bore 23 , with a diameter ranging from 0 . 5 to 2 . 0 mm . the cap member 30 has a cylindrical top section 32 which has a thickness of about 3 mm with a top planar surface 33 , an outer curved wall 34 and a bottom planar surface 35 which is seated adjacent the top surface 27 of the base member 22 when the components are mounted together . the top surface 33 while preferably planar may be milled to a degree of curvature that matches the physiological curvature of the articular cartilage being repaired , i . e ., a surface of a knee joint . larger constructs may have a cap member that has multiple stem sections and a base with an inverse “ female ” pattern which receives the stem sections . the cap member 30 includes an integral cylindrical stem 36 that depends from the bottom planar surface 35 of the top section 32 . the stem 36 has a length which is not longer than the depth of the blind bore 23 and has a diameter which is equal to or less than the diameter of the blind bore 23 . the stem 36 includes a transverse radial bore 37 which is aligned with the first and second lateral bores 28 , 29 of the base member 22 to receive a cylindrical pin 40 . more particularly , the pin 40 is inserted radially through the construct 20 to hold the cap member 30 in place within the base member 22 ( see fig3 ). the cap member 30 is preferably formed of demineralized cancellous allograft bone with a calcium content of less than 0 . 2 % calcium . alternatively , the cap member 30 has a substantially demineralized region , such as the top section 32 , with a calcium content of less than 0 . 2 % calcium . the cylindrical pin 40 is preferably constructed of cortical bone and has a length equal to or less than the diameter of the base member 22 . the pin 40 can also be constructed of a synthetic material . the cap member 30 can be secured to the base member 22 by a staple , suture , press fit or an adhesive compound such as fibrin based glue . the construct 20 is placed in a defect area bore which has been cut in the lesion area of the bone of a patient with the upper surface 26 of the cap member 30 being slightly proud , slightly below , or substantially flush with the surface of the original cartilage remaining at the area being treated . the construct 20 has a length which can be the same as the depth of the defect or more or less than the depth of the bore . if the construct 20 is the same as the depth of the bore 60 , the base of the implant is supported by the bottom surface of the bore and the top surface 33 of cap 30 is substantially level with the articular cartilage . if the construct 20 is of a lesser length , the base of the construct is not supported but support is provided by the wall of the defect area bore or respective cut out area as the plug is interference fit within the bore or cut out area with the cap being slightly proud , slightly below , or flush with the surrounding articular cartilage depending on the surgeon &# 39 ; s preference . with such load bearing support the graft surface is not damaged by weight or bearing loads which can cause micromotion interfering with the graft interface producing fibrous tissue interfaces and subchondral cysts . including the pluralities of longitudinal through going bores 25 and 31 in the construct 20 facilitates cell migration throughout the construct 20 . such cell migration promotes cartilage growth in the cartilage area and bone growth in the adjacent bone region . in operation , the lesion or defect is removed by cutting a . bore removing a lesion in the implant area . if desired , the open cancellous structure of the cap member 30 may be loaded with a cartilage paste or gel as noted below and / or one or more additives namely recombinant or native growth factors ( fgf - 2 , fgf - 5 , fgf - 7 , igf - 1 , tgf - β , bmp - 2 , bmp - 4 , bmp - 7 , pdgf , vegf ), human allogenic or autologous chondrocytes , human allogenic cells , human allogenic or autologous bone marrow cells , human allogenic or autologous stem cells , demineralized bone matrix , insulin , insulin - like growth factor - 1 , interleukin - 1 receptor antagonist , hepatocyte growth factor , platelet - derived growth factor , indian hedgehog parathyroid hormone - related peptide , viral vectors for growth factor or dna delivery , nanoparticles , or platelet - rich plasma . the construct 20 is then placed in the bore or cut away area in an interference fit with the surrounding walls . if the construct is moveable within the bore , suitable organic glue material can be used to keep the implant fixed in place in the implant area . suitable organic glue material can be found commercially , such as for example ; usseel ® or tissucol .® ( fibrin based adhesive ; immuno ag , austria ), adhesive protein ( sigma chemical , usa ), dow corning medical adhesive b ( dow corning , usa ), fibrinogen thrombin , elastin , collagen , casein , albumin , keratin and the like . the base of the blind bore 23 of the construct 20 can alternatively be provided with a matrix of minced cartilage putty or gel consisting of minced or milled allograft cartilage which has been lyophilized so that its water content ranges from 0 . 1 % to 8 . 0 % ranging from 25 % to 50 % by weight , mixed with a carrier of sodium hyaluronate solution ( ha ) ( molecular weight ranging from 7 . 0 × 10 5 to 1 . 2 × 10 6 ) or any other bioabsorbable carrier such as hyaluronic acid and its derivatives , gelatin , collagen , chitosan , alginate , buffered pbs , dextran , or polymers , the carrier ranging from ranging from 75 % to 50 % by weight . the cartilage is milled to a size ranging up to 1 mm . in the gel form , the minced cartilage has been lyophilized so that its water content ranges from 0 . 1 % to 8 . 0 %, ranging from 15 % to 30 % by weight and the carrier ranges from 85 % to 70 % by weight . the particle size of the cartilage when milled is less than or equal to 1 mm dry . the cartilage pieces can be processed to varying particle sizes and the ha or other carrier can have different viscosities depending on the desired consistency of the putty or gel . this cartilage matrix can be deposited into the demineralized cap member . the putty or gel enhances the tissue integration between the plug and host tissue . it is also envisioned that demineralized bone matrix and / or growth factors such as ( fgf - 5 , fgf - 7 , igf - 1 , tgf - β , bmp - 2 , bmp - 4 , bmp - 7 , pdgf , vegf ) or soluble factors such as insulin , interleukin - 1 receptor antagonist , hepatocyte growth factor , indian hedgehog and parathyroid hormone - related peptide , viral vectors for growth factor or dna delivery , nanoparticles may be adsorbed or combined with the construct or the cartilage pieces . in another embodiment , platelet - rich . plasma may be added to the construct . it is also envisioned that cells which have been grown outside the patient can be inserted by syringe into the cancellous cap member 30 before , during or after deposit of the construct 20 into the defect area . such cells include allogenic or autologous , bone marrow cells , stem cells and chondrocyte cells . the cellular density of the cells preferably ranges from 1 . 0 × 10 8 to 5 . 0 × 10 8 or from about 100 million to about 500 million cells per cc of putty or gel mixture . the cap member 30 can support the previously mentioned chondrogenic stimulating factors . the principles , preferred embodiments and modes of operation of the present invention have been described in the foregoing specification . however , the invention should not be construed as limited to the particular embodiments which have been described above . instead , the embodiments described here should be regarded as illustrative rather than restrictive . variations and changes may be made by others without departing from the scope of the present invention as defined by the following claims :
the invention is directed toward a cartilage repair assembly comprising a shaped allograft two piece construct with a demineralized cancellous cap and a mineralized cylindrical base member defining a blind bore with a through going transverse bore intersecting the blind bore . the demineralized cancellous cap has a cylindrical top portion and a smaller diameter cylindrical stem extending away from the top portion which fits into the blind bore of the mineralized base member . the cap stem defines a transverse through going bore which is aligned with the through going bore of the base member to receive a cylindrical cortical pin holding the cap within the base member . the shaped structure is dimensioned to fit in a drilled bore in a cartilage defect area so that the assembly engages the side wall of the drilled bore in an interference fit .