First Carpometacarpal Joint Motion and Proximal Migration of the First Metacarpal After Tensioning of a Suture Device Suspensionplasty Compared With Trapeziectomy: A Biomechanical Cadaver Study.

PURPOSE: The purpose of this cadaveric biomechanical experiment was to evaluate the effects of suture button suspensionplasty of the first carpometacarpal joint on thumb biomechanics and thumb position compared with an intact, arthritic specimen.

METHODS

Six tendons in 8 cadaver hands were loaded to simulate 6 activities of daily living and passively moved through a circumduction motion. Proximal migration of the base of the first metacarpal was measured using optical motion sensors in the intact hand, after trapeziectomy, and following insertion of a suture button suspensionplasty with nominal tightening (approximately 4.5 N) and with firm tightening (approximately 44.5 N).

RESULTS

Removal of the trapezium caused a significant increase in the proximal migration of the first metacarpal during a simulated jar grasp, opposition, flexion, extension, and abduction (average, 9.5 mm) compared with its location with the thumb in the intact, neutral position (average, 3.8 mm). Firm tightening of the tightrope caused a near elimination of the proximal migration of the first metacarpal (average, 0.7 mm). In all 6 static loading cases with the trapezium removed, firm tightening caused a significantly smaller migration than in the absence of tightening.

CONCLUSIONS

This biomechanical cadaver study supports the hypothesis that trapeziectomy results in proximal migration of the first metacarpal. Suture suspensionplasty mitigates against this migration while maintaining normal motion of the first metacarpal compared with the intact state. Firm tightening of the suture does not adversely affect the first metacarpal's mobility and further decreases proximal migration. However, firm tightening may cause impingement between the first and second metacarpals.

CLINICAL RELEVANCE: Suture button suspensionplasty can be used in addition to trapeziectomy in the treatment of basal joint arthritis, and may diminish the need for ligament reconstruction or temporary K-wire insertion.