Transfer of the supinator nerve to the posterior interosseous nerve for hand opening in tetraplegia through an anterior approach

Supinator to Anterior Interosseous Nerve Transfer to Restore Digital Flexion in Spinal Cord and Peripheral Nerve Injury

PURPOSE

Restoration of pinch and grasp is a chief concern of patients with cervical spinal cord injury or peripheral nerve injury involving the anterior interosseous nerve (AIN). We hypothesize that supinator nerve-to-AIN (Sup-AIN) nerve transfer is a viable option for AIN neurotization.

METHODS

We performed a retrospective review of patients who received Sup-AIN. Reported outcomes included Medical Research Council strength of the flexor digitorum profundus and flexor pollicis longus and passive range of digit motion. Patients with <12 months of follow-up were excluded.

RESULTS

Eleven patients underwent Sup-AIN, eight with peripheral nerve injury, and three with spinal cord injury. Three patients were excluded because of insufficient follow-up. Average follow-up was 17 months (range: 12-25 months). Six patients had M4 recovery (75%), one patient had M3 recovery (12.5%), and one did not recover function because of severe stiffness (12.5%). We observed no complications or donor site morbidity in our patients.

CONCLUSIONS

The Sup-AIN nerve transfer is an effective option to restore digital flexion in patients with peripheral nerve injury or spinal cord injury involving the AIN motor distribution. In comparison to previously described extensor carpi radialis brevis to AIN and brachialis to AIN nerve transfers, Sup-AIN offers the benefits of a more expendable donor nerve and shorter regenerative distance, respectively. The one failed Sup-AIN in our series highlights the importance of patient selection.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic V.

Supinator to Posterior Interosseous Nerve Transfer for Recovery of Hand Opening in the Tetraplegic Patient: A Case Series

BACKGROUND AND OBJECTIVES

Cervical spinal cord injury results in devastating loss of function. Nerve transfers can restore functional use of the hand, the highest priority function in this population to gain independence. Transfer of radial nerve branches innervating the supinator to the posterior interosseous nerve (SUP-PIN) has become a primary intervention for the recovery of hand opening, but few outcome reports exist to date. We report single-surgeon outcomes for this procedure.

METHODS

The SUP-PIN transfer was performed on adults with traumatic spinal cord injury resulting in hand paralysis. Outcome measures include Medical Research Council strength grade for extension of each digit, and angles representing critical apertures: the first web space opening of the thumb, and metacarpophalangeal angle of the remaining fingers. Factors affecting these measurements, including preserved tone and spasticity of related muscles, were also assessed.

RESULTS

Twenty-three adult patients with a C5-7 motor level underwent SUP-PIN transfers on 36 limbs (median age 31 years, interquartile range [21.5, 41]). The median interval from injury to surgery was 10.5 (8.2, 6.5) months, with 9 (7.5, 11) months for the acute injuries and 50 (32, 66) months for the chronic (>18 months) injuries. Outcomes were observed at a mean follow-up of 22 (14, 32.5) months. 30 (83.3%) hands recovered at least antigravity extension of the thumb and 34 (94.4%) demonstrated successful antigravity strength for the finger extensors, providing adequate opening for a functional grasp. Chronic patients (>18 months after injury) showed similar outcomes to those who had earlier surgery. Supination remained strong (at least M4) in all but a single patient and no complications were observed.

CONCLUSION

SUP-PIN is a reliable procedure for recovery of finger extension. Chronic patients remain good candidates, provided innervation of target muscles is preserved. Higher C5 injuries were more likely to have poor outcomes.

Volar versus dorsal approach for supinator to posterior interosseous nerve transfer: An anatomical study in cadavers

INTRODUCTION

Supinator to posterior interosseous nerve (SPIN) transfer allows reconstruction of finger/thumb extension and thumb abduction for low radial nerve palsy, incomplete C6 tetraplegia, and brachial plexus injury affecting C7-T1. No study has compared dorsal versus volar approach to perform SPIN transfer. This comparison is studied in the present work, assessing supinator motor branch length and ability to achieve nerve transfer from either approach.

METHODS

Ten fresh frozen cadavers were randomly allocated to receive either a dorsal or volar approach to PIN and supinator radial and ulnar branches (RB = radial, UB = ulnar). Supinator head innervation patterns were documented. RB and UB lengths, forearm lengths measured from ulnar styloid to olecranon, visualization of extensor carpi radialis brevis (ECRB) motor nerve without additional dissection, and ability to perform tension-free nerve transfer were assessed.

RESULTS

Nine of 10 specimens had supinator branches innervating both heads. The ECRB nerve was visualized in all volar but only one dorsal approach. No significant differences in forearm length were found. Volar with elbow extended: mean RB length was 35 ± 7.8 mm and UB was 37.8 ± 9.3 mm. Dorsal with elbow extended: mean RB length was 30 ± 4.1 mm and UB was 38.8 ± 7.3 mm. Dorsal with elbow flexed 90°: RB was 25.6 ± 3.8 mm and UB was 34.8 ± 4.8 mm. No significant differences were found in branch lengths between approaches (dorsal vs. volar UB, p = .339; dorsal vs. volar RB, p = .117). All limbs achieved tension-free coaptation.

CONCLUSION

Neither approach demonstrated superiority in achieving tension-free nerve transfer. Volar permitted immediate identification of ECRB nerve whereas this was only visualized in one dorsal specimen without additional dissection. Overall, the volar approach allows direct coaptation in elbow extension, mimicking maximal physiologic tension for neurorrhaphy. It simultaneously permits additional procedures for pinch reconstruction via single exposure, circumventing limb/microscope maneuvering, dorsal dissection, and increased operative time. Ultimate choice of approach should depend on surgeon familiarity and potential need for additional simultaneous transfers.