Locking Plate Arthrodesis Compares Favorably with LRTI for Thumb Trapeziometacarpal Arthrosis: Early Outcomes from a Longitudinal Cohort Study.

BACKGROUND: Trapeziometacarpal arthrodesis (TMA) has been complicated by nonunion and hardware failure.

QUESTIONS/PURPOSES: We hypothesized that modification of the TMA technique with a locking cage plate construct would afford reliable bony union while producing greater hand function than trapeziectomy with ligament reconstruction and tendon interposition (LRTI) at early follow-up.

METHODS: We enrolled 36 consecutive patients with trapeziometacapal osteoarthritis (14 TMA patients (15 thumbs), 22 LRTI patients (22 thumbs)). The study was powered to detect a minimal clinically important difference on the QuickDASH questionnaire between groups. Secondary outcomes included Michigan Hand Questionnaire (MHQ), VAS-pain, and EQ-5D-3L scores. Patients were examined to evaluate thumb motion and strength. TMA patients were evaluated clinically and radiographically for union.

RESULTS: Mean follow-up was 15.6 months, and the mean age was 59.2 years. Union was achieved in 14/15 (93%) of TMA thumbs. Improvement in QuickDASH scores was similar after TMA and LRTI (49 to 28 and 50 to 18, respectively). Postoperative patient-rated upper extremity function, health status, and pain were similar between groups. Pinch strength was significantly greater after TMA (5.9 vs 4.7 kg). No differences in thumb or wrist range of motion were observed postoperatively with the exception of greater total metacarpophalangeal joint motion after TMA. Complications after TMA included nonunion (7%), development of symptomatic scaphotrapezotrapezoidal (STT) arthrosis (7%), symptomatic hardware (7%), and superficial branch of the radial nerve (SBRN) paresthesia (7%). Complications after LRTI included subsidence (5%), MP hyperextension deformity (5%), and SBRN paresthesias (5%).

CONCLUSIONS: At early follow-up, patient-rated function was similar among patients undergoing TMA and LRTI. TMA produced 25% greater pinch strength compared with LRTI. Despite historical concerns regarding global loss of ROM with arthrodesis, motion was similar between groups. Our observed TMA nonunion rate of 7% is low relative to historically reported nonunion rates (7-16%). Locking cage plate technology affords rigid fixation for TMA with promising early results noting reliable bony union while minimizing complications.