Restoration of Pinch Strength After Traumatic Ulnar Nerve Injury: Outcomes of Transfer of the Opponens Pollicis Branch to the Terminal Division of the Deep Branch of the Ulnar Nerve.

PURPOSE: Ulnar nerve injury causes weak pinch strength through paralysis of the first dorsal interosseus and adductor pollicis muscles. Current reconstructive strategies provide variable reanimation of these muscles. It has been suggested that nerve transfer of the opponens pollicis (OPB) motor branch to the terminal division of the deep branch of the ulnar nerve (TDDBUN) may successfully restore pinch strength. The true effectiveness of this intervention remains unknown as there are few cases in the literature with all originating from a single author.

METHODS

We retrospectively identified patients who underwent transfer of OPB to TDDBUN at a single institution between 2019 and 2025 with at least 1-year clinical follow-up. Patients were excluded if they were unavailable to return for in-office strength testing. Key and subterminal key pinch, pinch-to-zoom, and grip strength (kg) were measured using dynamometers and compared with the contralateral side. First web space bulk (mm), Kapandji score, Froment's sign, and patient-reported outcomes (Disability of the Shoulder and Hand and Visual Analog Pain Scale) were assessed.

RESULTS

Twelve patients underwent transfer of OPB to TDDBUN and were available for in-office strength testing at greater than 1 year follow-up. The median patient age was 42 years (range, 19-66 years). Mean key pinch and subterminal key pinch strength were 48% (SD 17) and 43% (SD 23) of the uninjured side, respectively. Average pinch-to-zoom strength was 58% (SD 31) of the uninjured side. Average grip strength was 56% (SD 36) of the uninjured side. Mean first web space bulk was 81% (SD 15) of the contralateral. Interestingly, at final follow-up, 10 of 12 patients retained a positive Froment sign, despite pinch strength recovery. All patients retained thumb opposition with a Kapandji score ≥5.

CONCLUSIONS

Transfer of OPB to TDDBUN may reliably reinnervate the first dorsal interosseous and adductor pollicis, restoring approximately half of the pinch strength observed in the uninjured hand.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.