Humeral Shaft Fracture - Radial Nerve Palsy

Key Points

• Document radial nerve motor and sensory function before and after any manipulation or splinting.
• Primary radial nerve palsy with a closed humeral shaft fracture usually recovers spontaneously and does not automatically require immediate exploration.
• Open fracture, penetrating injury, vascular injury, or evidence of nerve transection lowers the threshold for surgical exploration.
• Most isolated closed humeral shaft fractures can be managed initially with splinting followed by functional bracing.
• Include the shoulder and elbow on imaging because associated injuries can change management.
• Use a wrist extension splint and therapy for radial palsy to preserve hand position while recovery occurs.
• Persistent nonunion, unacceptable alignment, or delayed neurologic recovery requires orthopedic reassessment.
• Consider pathologic fracture when mechanism is low energy and imaging shows abnormal underlying bone.

Algorithm

1. Assess skin, deformity, pulses, and complete motor and sensory function with explicit radial nerve documentation.
2. Obtain AP and lateral humerus radiographs including adjacent joints.
3. Identify open fracture, vascular injury, pathologic lesion, polytrauma, or other operative indications.
4. Provide analgesia, restore gross alignment if needed, and apply an appropriate initial splint.
5. For closed injury with primary radial palsy and no operative indication, arrange expectant nerve management with wrist support and serial examination.
6. Transition to functional bracing and early joint motion when swelling and stability permit.
7. Escalate to operative fixation or nerve evaluation when alignment fails, nonunion develops, or high-risk neurologic features are present.

Clinical Synopsis & Reasoning

Humeral shaft fractures follow falls, direct blows, motor vehicle trauma, sports injuries, or twisting forces. Evaluate the entire upper extremity rather than focusing only on the x-ray. Inspect for an open wound, severe swelling, skin tenting, and associated shoulder or elbow injury. Palpate pulses and document median, ulnar, musculocutaneous, and especially radial nerve function before and after splinting or reduction. Radial nerve motor testing includes wrist extension, finger metacarpophalangeal extension, and thumb extension; sensory testing includes the dorsal first web space.

Primary radial nerve palsy at presentation is a well-known complication because the nerve courses close to the humeral shaft. In a closed fracture without another indication for surgery, immediate nerve exploration is usually not required because most neuropraxic injuries recover spontaneously over weeks to months. The pattern of recovery and serial examination matter. A new radial palsy that appears after manipulation, a penetrating or open injury, vascular injury, or clinical concern for nerve transection changes the threshold for exploration.

Obtain AP and lateral radiographs including the shoulder and elbow. CT is not routine for an isolated diaphyseal fracture but can clarify complex proximal or distal extension. Assess mechanism and bone quality. Low-energy fractures in patients with known malignancy, metabolic bone disease, or a suspicious lytic lesion may be pathologic and require a different workup. Multiple trauma and high-energy injury warrant broader evaluation for chest, shoulder girdle, or vascular injuries.

Treatment Strategy & Disposition

Provide analgesia, gently correct gross deformity when necessary, and immobilize the arm. A coaptation splint or hanging arm splint is commonly used initially, followed after swelling decreases by a functional humeral brace when alignment is acceptable. Most isolated closed shaft fractures heal without surgery if alignment remains within acceptable limits and the patient can participate in follow-up. Early shoulder and elbow motion is encouraged once safe to reduce stiffness.

Operative fixation is considered for open fractures, associated vascular injury, floating elbow, segmental fractures, inability to maintain acceptable alignment, polytrauma requiring early mobilization, bilateral injury, selected pathologic fractures, or failure of nonoperative healing. Plate fixation and intramedullary nailing are common options. Radial nerve exploration is clearly indicated when there is open injury with likely nerve laceration, penetrating trauma, vascular repair requiring exposure, or other evidence of nerve discontinuity. Management of secondary palsy after reduction or fixation depends on timing, mechanism, and surgical context.

For primary radial nerve palsy in a closed fracture managed nonoperatively, use wrist splinting to prevent flexion contracture and preserve hand function, with hand therapy when available. Serial clinical examinations should document the return of brachioradialis, wrist extension, finger extension, and sensation. Electrodiagnostic testing or ultrasound can be used when recovery is delayed or the injury pattern is uncertain, but testing is not required immediately in every patient. Failure of fracture union or persistent nerve deficit warrants orthopedic reassessment.

Epidemiology / Risk Factors

• Humeral shaft fractures occur across age groups, with higher-energy mechanisms in younger adults and falls or fragility mechanisms in older adults.
• Radial nerve palsy accompanies a meaningful minority of shaft fractures because of the nerve’s close relationship to the bone.
• Spiral fractures of the distal third are classically associated with radial nerve injury but fracture pattern alone does not dictate exploration.
• Nonunion risk increases with smoking, poor biology, distraction at the fracture site, and certain transverse or proximal patterns.

Investigations

Surgical Indications

Pharmacology

Prognosis / Complications

• Most uncomplicated closed humeral shaft fractures unite with nonoperative treatment.
• Most primary radial nerve palsies associated with closed fractures show spontaneous recovery, although full recovery may take months.
• Nonunion can cause persistent pain and disability and may require operative fixation and bone-grafting strategies.
• Shoulder or elbow stiffness is reduced by early motion once fracture stability permits.

Patient Education / Counseling

• Explain that radial nerve weakness often improves without nerve surgery when the fracture is closed and the nerve was injured by stretch or bruising.
• Review splint care, swelling precautions, and the importance of maintaining wrist and finger position.
• Advise return for increasing pain, numbness, new weakness, coolness, color change, or splint-related skin pressure.
• Emphasize smoking cessation and follow-up radiographs because healing is assessed over time.
• Patients with wrist drop should understand the role of hand therapy and assistive splints during nerve recovery.

Notes

Radial nerve palsy is one of the most important examination findings in humeral shaft fracture because it changes follow-up but often does not change immediate treatment. The critical distinction is between a closed injury in which the nerve is likely bruised or stretched and an injury in which the nerve may have been cut, trapped, or exposed.

Serial examination is more informative than a single snapshot. Early return of brachioradialis or wrist extension is reassuring, and recovery typically progresses distally. Persistent complete palsy without any recovery over the expected interval should trigger specialist reassessment and may lead to ultrasound, electrodiagnostic testing, or exploration.

Nonoperative fracture care is active treatment, not benign neglect. Brace fit, skin checks, alignment radiographs, shoulder and elbow motion, and smoking cessation all affect outcome. Patients who cannot tolerate a brace or cannot reliably attend follow-up may need a different treatment strategy.

References

1. AAOS OrthoInfo: Humeral Shaft Fractures — Link
2. AO Surgery Reference: Humeral Shaft Fractures — Link
3. American Society for Surgery of the Hand: Radial Nerve Injury — Link