A feasibility study of computer-assisted bone graft implantation for tissue-engineered replacement of the human ankle joint.

Objective: Computer-assisted graft implantation may contribute to achieving biological joint replacement in the future. The purpose of this experimental study was to evaluate the feasibility and accuracy of a series of computer-assisted graft implantations into human cadaver ankle joints.

Methods: Three-dimensional graft models of virtually planned corresponding tibial and talar defects were created from bovine cancellous bone. A platform for computer-assisted surgery (CAS) was set up to implant the grafts. Registration was performed by pair-point matching with anatomical landmarks. In the case of insufficient registration accuracy, artificial landmarks were used for registration. Eight grafts (four tibial, four talar) were implanted in four human cadaver ankle joints. Postoperative CT was used for outcome analysis. The following criteria of accuracy were defined: macroscopic quality of implant fit; quality of the sagittal and coronar joint surface; and quality of the undersurface of the graft in relation to the base of the defect.

Results: No technical complications were observed during computer-assisted graft implantation. Clinically acceptable accuracy was achieved in 6 of 8 graft implantations, with implant failure occurring at the tibial and talar location in one ankle joint. In total, 25 of 32 criteria of accuracy were achieved: 6/8 for macroscopic implant fit; 5/8 for quality of the sagittal joint surface; 7/8 for quality of the coronar joint surface; and 7/8 for quality of the undersurface of the graft. Registration with anatomical landmarks did not achieve sufficient accuracy in 4 of 8 cases, whereas registration with artificial landmarks was successful in all these cases.

Conclusions: We demonstrated the feasibility and accuracy of computer-assisted graft implantation for tissue-engineered replacement of the human ankle joint. However, we cannot recommend the present type of registration by pair-point matching with anatomical landmarks due to the considerable inaccuracies. The focus should be on the improvement of non-invasive registration techniques and methods for evaluating postoperative outcome.