An 8-year-old girl presents to the orthopedic clinic 3 days after a supracondylar fracture of the humerus was reduced and immobilized in a posterior slab. On examination, she has weakness of wrist and finger extension with intact sensation in the dorsal first web space. The radial pulse is normal. Plain radiographs show the fracture in acceptable position. What is the most likely nerve injury and the recommended management?

Explanation

## Nerve Injuries in Supracondylar Fracture: Clinical Diagnosis and Management ### Clinical Presentation Analysis **Key Point:** The clinical findings point to radial nerve injury: - **Weakness of wrist and finger extension** = extensor carpi radialis, extensor carpi ulnaris, extensor digitorum (all innervated by radial nerve) - **Intact sensation in dorsal first web space** = radial nerve sensory territory is preserved - **Normal radial pulse** = vascular status is not compromised ### Differential Diagnosis of Nerve Injuries in Supracondylar Fractures | Nerve | Motor Loss | Sensory Loss | Mechanism | Frequency | |-------|-----------|--------------|-----------|----------| | **Anterior Interosseous (AIN)** | Thumb IP flexion, index finger DIP flexion (OK sign loss) | None (pure motor) | Traction/stretch | 5–10% | | **Posterior Interosseous (PIN)** | Wrist/finger extension, thumb extension | None (pure motor) | Traction/stretch | 10–15% | | **Radial Nerve** | Wrist/finger extension, thumb extension | Dorsal first web space | Traction/stretch or direct trauma | 5–10% | | **Median Nerve** | Thumb opposition, index finger DIP flexion | Lateral palm/radial digits | Compression/kinking | 10–15% | | **Ulnar Nerve** | Intrinsic hand muscles | Medial 1.5 digits | Rare; usually iatrogenic | <5% | ### Why Radial Nerve Injury Here? 1. **Motor deficit matches radial distribution:** Wrist and finger extension are radial nerve functions 2. **Sensory testing confirms:** Dorsal first web space sensation is intact (radial sensory branch) 3. **Mechanism:** Radial nerve is vulnerable to traction injury as the fracture displaces posteriorly ### Management of Radial Nerve Injury ```mermaid flowchart TD A[Radial nerve injury post-supracondylar fracture]:::outcome --> B{Timing of injury detection}:::decision B -->|At reduction| C{Nerve function returns after reduction?}:::decision B -->|Days later| D[Observe for spontaneous recovery]:::action C -->|Yes| E[Continue immobilization]:::action C -->|No| F[Observe for 8-12 weeks]:::action D --> G{Recovery by 12 weeks?}:::decision G -->|Yes| H[Full recovery expected]:::outcome G -->|No| I[EMG/NCS at 12 weeks]:::action I --> J{Denervation present?}:::decision J -->|Yes| K[Surgical exploration + repair]:::urgent J -->|No| L[Continue observation]:::action ``` **High-Yield:** Most nerve injuries in supracondylar fractures are **neurapraxias** (stretch injuries) that recover spontaneously within 8–12 weeks. Surgical exploration is NOT indicated unless: - Nerve injury occurs at the time of reduction (suggests direct trauma or entrapment) - No recovery by 12 weeks (suggests axonotmesis or neurotmesis) - EMG/NCS shows active denervation **Clinical Pearl:** The radial nerve is the most common nerve injured in supracondylar fractures (5–10% of cases), usually as a neurapraxia from traction. The prognosis is excellent, with >95% spontaneous recovery within 8–12 weeks. Reassure the family and avoid unnecessary surgery. ### Why NOT Immediate Surgery? - Nerve injury is a neurapraxia (stretch) in >90% of cases - Immediate surgical exploration has high morbidity and no proven benefit - Waiting 12 weeks allows time for spontaneous recovery - If no recovery by 12 weeks, EMG/NCS will guide further management [cite:Canale & Beaty Operative Orthopaedics 13e Ch 54; Rockwood & Green's Fractures in Adults 9e Ch 11]