Posterior Interosseous Nerve Palsy Following Non-Anatomic Distal Biceps Repair.

Distal biceps tendon repair carries a recognised risk of posterior interosseous nerve (PIN) injury, particularly when anatomical planes and tuberosity landmarks are not precisely identified. This case report describes an acute PIN palsy in a young labourer following single-incision cortical button fixation for a distal biceps rupture. Postoperative imaging revealed proximal malposition of the Endobutton, prompting urgent re-exploration. Intraoperatively, the biceps tendon was found to have been passed radially over the PIN, resulting in stretch and compression, and fixation was non-anatomical. The tendon was re-routed ulnar to the nerve and secured to the correct radial tuberosity footprint, with full neurological recovery achieved by 3 months. This case highlights the critical importance of full forearm supination, accurate development of the brachioradialis-pronator teres interval and precise identification of the tuberosity to avoid iatrogenic nerve injury during distal biceps repair. Level of Evidence: Level V (Therapeutic).