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.

Comparison of simulated key pinch after three surgical procedures for trapeziometacarpal osteoarthritis: a cadaver study.

We performed a cadaver study using 18 fresh-frozen adult forearms and hands to compare the tendon loads required to generate progressively greater key pinch (0.5 kg to 2 kg) after three different surgical procedures to treat trapeziometacarpal osteoarthritis: isolated trapeziectomy, trapeziectomy followed by ligament reconstruction with tendon interposition and total joint arthroplasty using a Touch® implant. Thumb pinch was simulated by loading the main actuator tendons involved in the key pinch. Six specimens were randomly assigned to each of the three surgical procedure groups. Measurements were made before and after the joint surgery. Specimens that underwent trapeziectomy with or without ligament reconstruction with tendon interposition required significantly higher tendon loads than those with the implant to achieve the same pinch force. There was no significant difference between the isolated trapeziectomy and ligament reconstruction groups. Using the implant resulted in similar median tendon loads compared with those of the intact sample. Total joint arthroplasty with a Touch® prosthesis may yield a superior biomechanical profile in which the tendon loads needed to achieve a certain key pinch force are lower and better distributed between the actuator muscles compared with trapeziectomy with or without ligament reconstruction.