JLE

Médecine et chirurgie du pied

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Varus of the Hindfoot in Foot Drop: a Key for the Etiologic Diagnosis Volume 36, issue 2, Juin 2020

Tables


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Authors

Introduction

The differential diagnosis between an L5 root lesion and a fibular neuropathy in foot drop are delicate and rarely discussed in the literature. Our study aimed to highlight the hindfoot varus during the swing phase as an interesting clinical sign to make the difference between a fibular neuropathy and L5 radiculopathy as a cause of foot drop. We also demonstrated the importance of electromyographical study as a tool for the etiological diagnosis in our patients.

Methods

Patients included in the study had a foot drop due to a peripheral etiology. We have carried out a visual and video analysis of the walk, particularly in search of hindfoot varus during the swing phase. We have performed an assessment of global muscle strength and segmental lower limb testing using the Medical Research Council's (MRC) manual muscle testing scale. We have completed it with the electroneuromyographic study (ENMG) of the lower limbs. We used the neuroradiological explorations in five patients to refine the etiological diagnosis of foot drop.

Results

Six patients with foot drop were included in our study. We divided them into two groups according to the presence or absence of hindfoot varus during the swing phase of walking: the group “GF” contained three patients with varus, while the “GR” group included three patients without varus. All patients had a deficiency of the dorsal muscles of the foot. In contrast to GF patients, GR patients had a deficit in the gluteal and posterior tibial muscles. The medial hamstring reflex (L5 root) was abolished. The ENMG revealed neurogenic trace of the gluteus medius and posterior tibial muscles in GR patients, these muscles were normal at detection in the GF group. An ultrasound of the knee showed fibular nerve compression by an expansive process in two of the GF patients. MRI of the lumbar spine revealed L5 root compression resulting from disc herniation in all GR patients. L5 radiculopathy was the cause of foot drop in GR patients who did not have hindfoot varus, whereas fibular neuropathy was retained in GF patients with hindfoot varus.

Conclusion

When dealing with foot drop peripheral etiologies, hindfoot varus is a diagnostic key for the differentiation between an L5 radiculopathy and a fibular neuropathy. The complement by electromyographic study, and in particular by the needle detection of the posterior tibial, allows to retain with certainty the nerve lesion incriminated in the foot drop.