Does a radial nerve injury in the deltoid region with preserved hand function but lack of wrist power imply a complete nerve damage?

Radial Nerve Injury at Deltoid Level: Interpretation of Preserved Hand Function with Wrist Weakness

A radial nerve injury at the deltoid level (proximal arm) does NOT mean the entire nerve course is affected—your clinical findings of preserved finger extension and pinch with isolated wrist extensor weakness indicate a partial or incomplete nerve injury, most likely affecting only the nerve fascicles supplying wrist extensors while sparing those to finger/thumb extensors.

Understanding the Clinical Pattern

Your examination findings are actually inconsistent with a complete radial nerve injury at any level:

• Preserved finger extension ("no more dropping of the hand against gravity") indicates the posterior interosseous nerve (PIN) branch is functioning 1
• Excellent pinching confirms thumb extension via extensor pollicis longus is intact 2
• Absent wrist extension power suggests selective involvement of extensor carpi radialis brevis/longus nerve branches 1

This pattern suggests either:

1. A partial/incomplete nerve injury with selective fascicular damage at the proximal level 1
2. A neuropraxic injury (nerve bruising without axonal disruption) affecting specific fascicles 3

Why Location Doesn't Equal Complete Injury

The radial nerve is organized in fascicles—bundles of nerve fibers destined for different muscles travel together but can be injured independently 1. An injury "at the deltoid level" (proximal humerus) can damage some fascicles while sparing others, explaining your mixed clinical picture 1.

• If the entire nerve were affected at the deltoid level, you would see complete loss of wrist AND finger/thumb extension 2, 1
• The fact that finger extension recovered first suggests the injury was never complete, or involved preferential damage to wrist extensor fascicles 1

Prognosis and Timeline

Your patient has an excellent prognosis given the preserved distal function:

• By 7 months post-injury: If wrist extension hasn't recovered, there's still a 56% probability of recovery by 18 months 3
• By 12 months post-injury: Probability drops to 17% for subsequent recovery 3
• Level of injury does NOT predict recovery timing—no association was found between proximal versus distal injuries and time to recovery 3
• Wrist extension recovers in at least 80% of patients regardless of injury level, though finger/thumb extension has better outcomes with more distal injuries 1

Critical Management Points

Immediate actions:

• Document the exact motor grades for wrist extensors (ECRB/ECRL), finger extensors (EDC), and thumb extensors (EPL/EPB) separately 1
• Avoid assuming complete injury based solely on anatomic location—the clinical exam is more reliable 1
• Consider electrodiagnostic testing if complete paralysis were present (which it's not in your case), but this is less useful for partial injuries 4

Watchful waiting is appropriate for at least 7 months given the high probability of continued recovery 3:

• Maintain passive wrist extension range of motion to prevent contractures 5
• Consider a tenodesis wrist splint that allows functional hand use while protecting the weak wrist extensors 5
• Avoid early surgical exploration as the probability of spontaneous recovery remains high 3

When to Consider Surgical Intervention

Surgical options become relevant if:

• No wrist extensor recovery by 12 months (when probability drops to 17%) 3
• Progressive loss of function or new symptoms suggesting nerve compression 4, 6
• Patient requires earlier functional restoration for occupational reasons 2

Surgical options include nerve transfers (median to radial nerve transfer for wrist extension) or tendon transfers, with nerve transfers potentially restoring more normal function 2.

Common Pitfall to Avoid

Do not assume that a proximal injury location automatically means worse prognosis or complete nerve involvement 3, 1. The clinical examination pattern—not the anatomic injury site—determines the extent of nerve damage and guides prognosis 1.