Neglected posterior interosseous nerve injury

Abstract

Posterior interosseous nerve (PIN) injury is uncommon due to its anatomically deep location. We report a neglected, rare case of PIN injury presenting the loss of extension of thumb, index, and small fingers with weakness of thumb abduction in a 49-year-old male patient. The patient sustained a penetrating injury to his right forearm caused by a kitchen knife that was repaired primarily through an emergency surgery under general anesthesia. During the regular follow-up on the 52nd postoperative day, the patient presented 20° of extension lags in the right thumb and index finger and 30° in the small finger. Wrist extension was intact, and there was no sensory deficit. We explored the wound and traced the PIN completely, identifying a club-shaped neuroma formation at the proximal cut end of the PIN. Delayed nerve repair was performed with a double-strip cable graft. Hand surgeons should be aware of the probable PIN injury in certain situations of forearm-penetrating injury and perform proper preoperative physical examination to rule out neurovascular deficits. Careful exploration and immediate repair of severe PIN are mandatory, even in emergency situations.

Keywords: Cable graft; Posterior antebrachial cutaneous nerve; Posterior interosseous nerve; Upper extremity.

Fig. 1

A 49-year-old man sustained a severe penetrating injury to his right forearm caused by a kitchen knife. Dorsal-ulnar laceration wound was 10 cm long, and volar-radial laceration wound was 5 cm long. Physical examination in the emergency room revealed right thumb's flexion and extension loss, with extension loss of other four fingers.

Fig. 2

Immediate myorrhapy was performed during emergency surgery. Extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum communis, extensor digiti minimi, and extensor carpi ulnaris were repaired at the superficial layer. Abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus were repaired at the deep layer.

Fig. 3

On the 52nd postoperative day during outpatient follow-up, the patient presented delayed symptoms of the right thumb drop with weakness, index finger's extension lag of 20°, and little finger's extension lag of 30°. Extensions of the middle and ring fingers were intact. Wrist extension was intact and there was no sensory deficit.

Fig. 4

Illustration of the posterior interosseous nerve (PIN) anatomy and innervation with injury level at the forearm (red line). ECRB, Extensor carpi radialis brevis; ED, extensor digitorum; EDC, extensor digitorum communis; EDM, extensor digiti minimi; EIP, extensor indicis proprius; ECU, extensor carpi ulnaris; APL, abductor pollicis longus; EPB, extensor pollicis brevis; EPL, extensor pollicis longus.

Fig. 5

(A) Assuming a possible neurovascular bundle injury, we performed delayed exploration and found transected posterior interosseous nerve (PIN) in the wound. There was a neuroma formation at the proximal end of PIN. After resection of the neuroma, nerve gap between the proximal and distal end was 2.5 cm. (B) Posterior antebrachial cutaneous nerve was harvested for delayed nerve repair. (C) Cable grafting was performed using the harvested posterior antebrachial cutaneous nerve.