Scaphometacarpal arthroplasty with a TOUCH® prosthesis: feasibility and biomechanical impact in a cadaver model.

In this cadaveric study, we compared the performance of the TOUCH® dual mobility trapeziometacarpal prosthesis implanted sequentially in the trapeziometacarpal joint and scaphometacarpal joint. Intraprosthetic mobility, implant dislocation, intraprosthetic impingement and the effect on scaphoid position were evaluated in six hands using radiographic measurements. The standard necks of 6-10 mm were used for trapeziometacarpal arthroplasty. Scaphometacarpal arthroplasty after trapeziectomy was technically feasible but required specially designed prosthetic necks 12-26 mm in length. Compared to trapeziometacarpal arthroplasty, scaphometacarpal arthroplasty increased the intraprosthetic mobility by 7%-39%. While no complications occurred with trapeziometacarpal arthroplasty, there were two instances of implant dislocation and seven instances of intraprosthetic impingement with scaphometacarpal arthroplasty. Unlike trapeziometacarpal arthroplasty, scaphometacarpal arthroplasty altered scaphoid position by translating it in an ulnar and proximal direction relative to the radius.