Review Question - QID 4665

The patient has suffered from a peroneal nerve injury most likely from errant retractor placement during the hip replacement resulting in a foot drop. The most appropriate next treatment is an ankle-foot orthosis.

The ankle joint of an ankle-foot orthoses (AFOs) should restrict plantarflexion to prevent foot drop during the swing phase. In a patient who can not actively dorsiflex the foot the AFO keeps the foot in a neutral position during gait allowing for uninterrupted swing during ambulation.

Park et al reviewed common peroneal nerve injury after THA. Only one-half of the patients in the study who developed common peroneal nerve palsy following total hip arthroplasty recovered fully. The mean time to recovery was approximately one year for partial peroneal palsy and one and one-half years for complete palsy. Obesity adversely influenced the nerve recovery. Thus, at 3 months, the nerve should continue to be monitored and the use of an AFO would assist in ambulation.

Yokoyama et al. developed an AFO with an oil damper to adjust the plantarflexion resistive moment as excessive plantarflexion resistance will cause excessive knee flexion during the stance phase. They found the AFO with the oil damper achieved sufficient plantarflexion of the ankle and mild flexion of the knee by adjusting a proper plantarflexion resistive moment during initial stance phase, and provided a more comfortable gait than did the traditional AFOs.

Illustration A shows the location of the sciatic nerve relative to the short external rotators when performing a posterior approach to the hip.

Incorrect Answers:
Answer 1: Immediate foot drop following a total hip replacement is likely related to the procedure, not the spine.
Answer 2: Although an ankle fusion would eliminate the need for dorsiflexion while ambulating, it is more invasive than an AFO and does not consider the potential for nerve recovery over time.
Answer 4: Revising the hip would increase the risk of peroneal palsy.
Answer 5: It is too early to consider nerve grafting.