From the Research
Wrist drop in midshaft humerus fractures is primarily caused by injury to the radial nerve, which can occur due to direct trauma, stretching, or compression by bone fragments. This injury leads to paralysis of the wrist and finger extensors, resulting in the characteristic "wrist drop" where patients cannot extend their wrist or fingers. The radial nerve innervates the extensor muscles of the forearm, so damage prevents active extension of the wrist, thumb, and metacarpophalangeal joints.
Pathophysiology and Treatment
The pathophysiology of radial nerve injury in humeral shaft fractures involves the nerve's close proximity to the bone in the spiral groove of the humerus, making it susceptible to injury during fractures at the midshaft [(1,2,3,4,5)]. Treatment involves stabilizing the fracture, which often allows the nerve to recover spontaneously over 3-4 months in most cases of neurapraxia (nerve bruising) 1.
Management Approach
The most recent and highest quality study recommends expectant management for 16-18 weeks, followed by surgical intervention if there is no improvement 1. During recovery, a wrist splint should be used to maintain proper positioning and prevent contractures. If no improvement occurs after the specified period, electromyography and nerve conduction studies are recommended to assess nerve function, and surgical exploration may be necessary if the nerve is found to be transected or entrapped in callus 5.
Key Considerations
- The overall prevalence of radial nerve palsy in humeral shaft fractures is approximately 12.3% 5.
- Patients with radial nerve palsy treated nonsurgically have a rate of spontaneous radial nerve recovery of 77.2% 5.
- Early surgical exploration and fracture repair within 3 weeks of injury may offer a higher likelihood of regaining radial nerve function 5.
Clinical Decision Making
In clinical practice, the management of wrist drop due to radial nerve injury in midshaft humerus fractures should prioritize spontaneous recovery through expectant management, with a clear timeline for reassessment and potential surgical intervention based on the absence of improvement [(1,5)]. This approach balances the potential benefits of early intervention with the risks of unnecessary surgery, aiming to optimize outcomes in terms of morbidity, mortality, and quality of life.