When the Nerve Lies Between the Fragments: A Mid-Shaft Humeral Fracture Mimicking a Holstein-Lewis Injury.

Introduction: Radial nerve palsy is a recognized complication of humeral shaft fractures, often associated with distal-third spiral patterns described by Holstein and Lewis. However, authentic mechanical entrapment of the nerve at the mid-shaft level is rather rare. These events test the limits of normal anatomy and show how important it is to look into things right once when fracture geometry suggests possible nerve entrapment. Case Report: A 28-year-old right-handed female sustained a humeral fracture at the mid-shaft (AO 12-A3) following a collision with a two-wheeled vehicle. She showed early signs of radial nerve palsy, which meant that her wrist and finger extensors were weak, but her triceps were still working. Radiographs confirmed a transverse fracture/very short oblique configuration. An open reduction and internal fixation within 6 h of injury through the posterior revealed that the radial nerve was stuck between broken pieces of bone and was being compressed by sharp cortical edges. During fixation, the nerve was carefully released and secured. Further dissection proximally revealed an auxiliary branch originating from the radial cord, an anatomical variant. After surgery, rehabilitation included early range-of-motion exercises and wrist splinting. The patient achieved 50% recovery of wrist extension at 12 weeks and complete neurological recovery with full bony union by 24 weeks. Discussion: This case elucidates that entrapment of the radial nerve can occur at the mid-shaft level when fracture morphology and varied nerve anatomy overlap. Cadaveric studies confirm the variations in radial nerve branching and its proximity to the humeral cortex. Early surgical exploration and decompression are crucial to avoid chronic palsy, particularly when the clinical presentation or fracture morphology is atypical. Conclusion: Atypical mid-shaft humeral fractures with radial-nerve palsy require prompt surgical evaluation. It is vital to know about high-level radial-nerve branching variants because locating and releasing them early helps the patient fully recover and helps us learn more about the Holstein-Lewis mechanism outside its usual distal zone.