Incidence of Radial Nerve Palsy in Mid-Shaft Humerus Fractures
The incidence of radial nerve palsy in mid-shaft humerus fractures ranges from 11.8% to 19% overall, with primary (injury-related) palsy occurring in approximately 13% of cases and secondary (iatrogenic/postoperative) palsy in approximately 6% of cases. 1
Overall Incidence Data
- Primary radial nerve palsy (present at time of injury) occurs in 13% of humeral shaft fractures requiring surgical treatment 1
- Secondary radial nerve palsy (developing after surgical intervention) occurs in 6% of cases postoperatively 1
- The combined incidence is approximately 19% when both primary and secondary palsies are included in surgically treated humeral shaft fractures 1
- Literature reports a range of 2% to 17% across various studies, with an average of 11.8% 1, 2
Injury Mechanism Significantly Affects Incidence
The energy of trauma is a critical prognostic factor that directly impacts the incidence and severity of radial nerve involvement:
- High-energy injuries demonstrate a significantly higher incidence of radial nerve palsy compared to low-energy injuries 3, 4
- In one surgical series, 27 of 109 high-energy fractures (24.8%) had radial nerve palsy versus 4 of 53 low-energy fractures (7.5%) 3
- Logistic regression analysis confirms that injury mechanism is the most significant risk factor for primary radial nerve palsy 3
Open vs. Closed Fractures
- Open humeral shaft fractures have a substantially higher rate of nerve injury requiring exploration 5
- In open fractures with radial nerve palsy, 64% (9 of 14 patients) had either complete nerve laceration or nerve interposition between fracture fragments 5
- This high rate of structural nerve damage occurs equally across Gustilo types I, II, and III open fractures 5
Clinical Implications for Risk Stratification
Low-energy injuries:
- Lower overall incidence of nerve palsy 4
- When palsy occurs, nerves are typically intact or entrapped rather than lacerated 4
- Recovery is nearly universal with conservative management 4
High-energy injuries:
- Higher incidence of nerve palsy (approximately 25%) 3
- Greater likelihood of neurotmesis or severe contusion 4
- Oblique, transverse, wedge, and comminuted fracture patterns are more common but represent markers of high-energy trauma rather than independent risk factors 3
Important Caveats
- The 6% incidence of secondary (iatrogenic) palsy is predominantly associated with plate fixation rather than other fixation methods 1
- Mid-shaft location specifically places the radial nerve at highest risk due to its anatomic course in the spiral groove 1, 2
- These incidence figures represent surgically treated fractures; the true population-based incidence including conservatively managed fractures may differ 1