Preoperative Radial Nerve Examination in Humeral Fractures
A thorough preoperative radial nerve examination must document motor function (wrist extension, thumb extension, finger extension at MCPs), sensory function (first dorsal web space), and should be performed by an attending surgeon when possible to ensure reliability and avoid falsely attributing preoperative injuries as iatrogenic.
Essential Components of the Examination
The radial nerve examination should systematically assess:
Motor Function
- Wrist extension (extensor carpi radialis longus/brevis)
- Thumb extension (extensor pollicis longus)
- Finger extension at metacarpophalangeal joints (extensor digitorum communis)
- Thumb abduction (abductor pollicis longus)
Sensory Function
- First dorsal web space sensation (superficial radial nerve distribution)
Documentation Requirements
Document the examination as "reliable" or "unreliable" based on patient cooperation, particularly critical in pediatric patients or those in significant pain 1. In a prospective study of 100 supracondylar fractures, 16% had preoperative nerve injuries when examined by an attending pediatric orthopedic surgeon who only included patients where a reliable examination could be obtained 1.
Clinical Context and Pitfalls
Common Mistake: Attributing Preoperative Injuries as Iatrogenic
The true rate of iatrogenic radial nerve injury after humeral fracture surgery is approximately 3% when adequate preoperative examination is performed 1. Many "iatrogenic" injuries are actually missed preoperative injuries discovered postoperatively when the patient is more cooperative and less painful.
Examination Reliability Factors
- Patient age and cooperation - particularly challenging in young children
- Pain level - may prevent adequate motor testing
- Timing - examination should be performed before analgesics cloud assessment
- Examiner experience - attending-level examination is preferable 1
Adjunctive Diagnostic Tools
Ultrasound Evaluation
Preoperative ultrasound can differentiate nerve contusion/stretch from laceration/entrapment, guiding operative versus nonoperative decisions 2. In one study, ultrasound showed 92% concordance with intraoperative findings regarding radial nerve condition and location 2.
Ultrasound-guided preoperative nerve localization in distal humeral shaft fractures can reduce:
- Operative time (113 vs 136 minutes)
- Nerve exposure time (21 vs 33 minutes)
- Intraoperative bleeding (247 vs 336 mL) 3
When Ultrasound is Most Useful
- Suspected nerve laceration or entrapment
- Planning surgical approach for distal shaft fractures
- Differentiating neurapraxia from structural injury 2
EMG and Doppler Studies
Preoperative EMG and Doppler ultrasound are NOT routine examinations before surgery for humeral fractures 4. Reserve these for specific indications when clinical examination suggests vascular compromise or when nerve recovery monitoring is needed postoperatively.
Fracture-Specific Considerations
Humeral Shaft Fractures
Radial nerve injury occurs commonly with humeral shaft fractures 5. The examination findings directly influence the decision for early exploration versus expectant management.
Supracondylar Fractures (Pediatric)
Nerve injury rates correlate with fracture severity 1:
- Gartland Type II: 7%
- Gartland Type III: 19%
- Gartland Type IV: 36%
Median nerve injuries (12%) are more common than radial nerve injuries (8%) in supracondylar fractures 1.
Documentation Strategy
Document specifically:
- Each motor component tested (not just "radial nerve intact")
- Sensory distribution assessed
- Patient cooperation level and examination reliability
- Comparison to contralateral side when possible
- Any limitations preventing complete assessment
This detailed documentation protects against medicolegal issues and provides baseline for postoperative comparison, distinguishing true iatrogenic injuries from missed preoperative deficits.