Recovery of chronic painful drop foot following common peroneal nerve neurolysis: A Case Series
Introduction
Drop foot, characterized by the inability to lift the front part of the foot, is a condition often caused by muscular dystrophies, central nervous system disorders, or peripheral nerve injuries. One of the most common causes of drop foot is compression or traction of the common peroneal nerve (CPN), which is susceptible to damage due to its proximity to the mobile knee joint and fibular head. This condition is frequently associated with a poor prognosis, especially when it occurs following trauma such as knee dislocation, direct blows, or severe ankle inversion injuries.
CPN neurolysis has been proposed as a treatment option for patients with drop foot due to CPN compression. This procedure aims to relieve pressure on the nerve, thereby restoring its normal function. However, the success of this intervention is highly variable, and the optimal timing of the procedure is a subject of debate. Some studies suggest that the best time for CPN decompression is around 5.5 months after the initial trauma, while others indicate that surgery beyond 9.5 months may be ineffective.
Methods
The study involved three patients with chronic drop foot who underwent peroneal nerve neurolysis at the Maxima Medical Centre in Veldhoven between 2013 and 2023. These cases were selected to evaluate the results of the procedure.
The Cases
Each patient's medical history, physical examination findings, and diagnostic test results are detailed in the following sections.
Case 1
A 22-year-old female with no significant medical history was referred due to increasingly painful left lower leg. Her drop foot had developed 12 months earlier after prolonged kneeling while installing a wooden floor. The neurologist confirmed a left-sided drop foot. Imaging, including MRI of the brain and vertebral column, and CPN ultrasound, were normal. An EMG showed peroneal muscle reinnervation. Physical therapy did not improve the condition.
The patient reported severe lower leg pain and loss of lower leg power, with tingling sensations during rest and at night. Despite the pain, she chose to undergo surgery after extensive counseling and provided verbal and written consent.
Fourteen months after the onset of the drop foot, she underwent CPN decompression via a curvilinear 2-inch incision just distal to the fibular head. The nerve appeared normal post-operatively, and she reported total pain relief and gradual foot movement recovery. An intensive physical therapy program was implemented, and six months post-operatively, there was a 5 mm smaller lower leg diameter in the affected leg compared to the other side. Skin sensation was still slightly less compared to the other side, but her gait had normalized.
Case 2
A 58-year-old female with a history of hernia at the L5-S1 level treated with laminectomy and multiple knee surgeries for severe arthrosis, including a total joint replacement, developed a painful drop foot immediately following knee surgery in 2015. The neurologist confirmed chronic CPN damage likely due to traction during the knee operations. Despite extensive counseling, the patient opted for CPN decompression.
The procedure was uneventful, and two weeks later, she reported lower leg pain disappearance and the ability to extend all her toes. However, five months post-operatively, her painful drop foot returned, and she was back to using a wheelchair due to knee instability.
Case 3
A 65-year-old healthy male with a history of brisk walking to lose weight developed a spontaneous painful right drop foot over four months. X-ray and MRI of the lower leg were normal. The neurologist suggested right-sided CPN damage, possibly due to chronic exertional compartment syndrome (CECS) associated with intense brisk walking.
The patient underwent CPN decompression with fasciotomy of the anterior and peroneal compartments. The procedure was successful, and two weeks later, the lower leg pain disappeared, with complete normalization of foot function after three months. Ten years later, the patient's function and skin sensation of the leg are normal.
Discussion
This case series highlights the effectiveness of surgical decompression for chronic painful drop foot, even when symptoms have been present for years. Neurolysis should be considered in such cases, especially when drop foot is accompanied by severe neuropathic pain.
However, the study also emphasizes the importance of detailed history taking and accurate physical examination in diagnosing CPN entrapment and distinguishing it from other conditions like anterior CECS. The timing of surgery is crucial, with the optimal window for decompression surgery around 5.5 months after symptom onset, but ideally within 12 months.
Conclusion
Surgical decompression of the CPN for drop foot can be effective, even with chronic symptoms. Neurolysis may be a viable option for patients with long-standing chronic foot drop, and further research is needed to optimize treatment for patients with chronic drop foot and neuropathic pain.
