Tendon reattachment to a metallic implant using an allogenic bone plate augmented with rhOP-1 vs. autogenous cancellous bone and marrow in a canine model.

Functionality of endoprosthetic reconstruction may be improved through secure and lasting soft tissue reattachment directly to the metallic implant surface. Tendon reattachment to the metallic surface of a titanium implant (enhanced tendon anchor, ETA) using autogenous bone plate as an interpositional structure between the tendon and metal, augmented with autogenous bone chips and marrow, provided successful mechanical and functional outcome. However, preparation of the autogenous bone plate is not practical in a clinical setting, but application of an allogenic bone plate could be an alternative. The autogenous cancellous bone and marrow may also be substituted by bone growth factors so that no autogenous bone graft is required. We hypothesized that the reconstitution of the direct tendon-bone insertion morphology in tendon reattachment to metallic implant could be achieved using allogenic cancellous bone plate augmented with autogenous cancellous bone and marrow, and that the autogenous bone grafts could be replaced by recombinant human osteogenic protein-1 (rhOP-1). In two canine groups the supraspinatus tendon was reattached unilaterally to a modified ETA implant with a highly porous metallic surface known as Tritanium Dimensionalized Metal. Allogenic bone plates saturated with rhOP-1-collagen putty were used in the OP-1 (OP) group, while plates saturated with autogenous cancellous bone and marrow were used in the bone marrow (BM) group. Functional, radiographical, mechanical and histomorphological analysis results were compared between both groups. At 15 weeks, gait analysis showed 78% and 81% recovery of preoperative weight-bearing in OP and BM groups, respectively. The calcified area around the tendon in OP group was 5.2 times larger than that in BM group (p<0.001). The ultimate tensile strength of the reattachment was 24% and 38% of the intact contralateral side in OP and BM groups, respectively, without significant difference between them. There was evidence of tendon-bone insertion transitional zones, tissue ingrowth and adhesion to the metallic surface in both groups. In conclusion, the use of the allograft combined with rhOP-1 had a similar effect as combined with autogenous cancellous bone and marrow in the tendon reattachment to the metallic surface.