Is there a correlation between callus formation and radial nerve lesion?

Radial Nerve Entrapment in Fracture Callus

Yes, there is a well-documented correlation between callus formation and radial nerve lesions, specifically when the radial nerve becomes entrapped within or compressed by fracture callus during bone healing, most commonly following humeral shaft fractures. 1, 2, 3

Mechanism of Injury

The radial nerve is particularly vulnerable to callus-related injury because it courses around the posterior aspect of the humerus in the spiral groove before traveling anteriorly at the forearm level. 4 This anatomical relationship places it at risk for:

• Direct entrapment within the callus during fracture healing, where the nerve becomes physically encased in the newly formed bone 1, 3
• Compression by exuberant callus formation that narrows the space available for the nerve 2
• Secondary nerve injury that develops weeks to months after the initial fracture, even when no nerve palsy was present initially 1, 3

Clinical Presentation Patterns

Delayed Presentation

The most clinically significant pattern is delayed radial nerve palsy that appears after fracture healing has begun:

• Patients may have no neurological symptoms at the time of initial injury 1, 2
• Nerve palsy becomes apparent 4-9 months post-fracture as callus forms and entraps the nerve 1, 3
• Critical pitfall: Long-arm plaster casts can mask wrist extension weakness, delaying diagnosis until cast removal 1

Silent Entrapment

• Nerve entrapment in callus can occur without any clinical neurological deficit 2
• Radiographic clues include small (3-4 mm) diameter holes in the callus where the nerve passes through 2
• This asymptomatic entrapment becomes a surgical hazard if operating on the same site for other reasons (e.g., deformity correction) 2

Anatomical Locations at Risk

Distal third humeral shaft fractures pose the highest risk for radial nerve-callus complications:

• The radial nerve is most vulnerable in the spiral groove of the humerus 5, 4
• Supracondylar humerus fractures with callus formation can create osseous tunnels that trap the nerve 2
• Prolonged pressure on the radial nerve in this location should be avoided during positioning and immobilization 5

Diagnostic Approach

When evaluating for potential radial nerve-callus correlation:

• Carefully examine radiographs for small holes or channels in the callus that may indicate nerve passage 2
• Ultrasound examination can identify nerve transection or entrapment within callus 3
• Electromyography and nerve conduction studies help confirm the diagnosis and localize the lesion 4
• Maintain high suspicion for delayed nerve palsy in any patient with healing humeral fractures, even if initial examination was normal 1, 3

Management Implications

Surgical Considerations

• Nerve exploration and release is indicated when entrapment is confirmed 1, 2, 3
• Nerve grafting may be required if the nerve is transected or severely damaged, with good functional recovery possible even in delayed repairs (average 7 months to recovery) 6
• Surgery should address both the entrapment and any associated nerve transection, as combined primary and secondary lesions can occur 3

Prevention Strategies

• Avoid long-arm plaster casts for distal third humeral shaft fractures to enable early detection of wrist extension weakness 1
• Perform serial neurological examinations during fracture healing to detect delayed nerve palsies 1, 3
• Review radiographs for callus characteristics that suggest nerve proximity or entrapment before any surgical intervention 2

Key Clinical Pitfall

The most dangerous scenario is asymptomatic nerve entrapment discovered intraoperatively during surgery for another indication (e.g., malunion correction). 2 Preoperative awareness of radiographic signs (small holes in callus) is essential to prevent iatrogenic nerve injury during these procedures.