Superficial peroneal nerve neuroma after syndesmotic stabilisation surgery

Abstract

The ankle is a region crowded with multiple neurovascular and musculotendinous structures. We describe a case of a rare neurological complication following ankle surgery.

Background

Lower limb peripheral nerve neuromas are a rare occurrence. Ankle surgery, whether in trauma or an elective setting, is quite common. A patient underwent a syndesmosis stabilisation with a suture button device for instability and later presented with superficial nerve neuroma.

Case presentation

A 58-year-old man who sustained a twisted ankle injury presented with moderate swelling and tenderness in the injured ankle.

Imaging excluded any fracture, but he had increased tibiofubular clear space. On clinical examination, we noted that the dorsiflexion external rotation stress test and squeeze tests were both positive. The diagnosis of ligamentous syndesmotic injury was made. Once swelling settled, the patient was taken to the operating theatre, and he underwent suture button device syndesmotic stabilisation surgery.

Approximately 6 months after the surgery, the patient was clinically doing quite well with full weight bearing, and he was functionally active. However he reported concerns of a 'pins and needles' feeling over the dorsum of the foot. Three months after reporting pins and needles, his symptoms increased in intensity and became persistent. A new round of imaging found no apparent causes. We decided to remove the suture button device as a day patient case.

Investigations

When the symptoms did not settle after removal of suture button device, an MRI was done subsequently, which showed the neuroma at the anterolateral aspect of the ankle (figures 1 and 2).

Figure 1.

Sagittal MRI showing superficial peroneal nerve neuroma (yellow arrows).

Figure 2.

Axial plane MRI showing superficial nerve neuroma (yellow arrow).

Differential diagnosis

The differential diagnosis with this clinical picture and imaging were muscle herniation, intraneural ganglion, nerve neuroma and idiopathic neuritis.

Treatment

Three months following the removal of the suture button device, the patient’s symptoms did not improve. New MRI revealed a small, bulbous structure over the lateral distal fibula. We surgically explored it and found a 1.5 cm neuroma (figures 3 and 4). Therefore, we performed a surgical neurectomy and transposition.

Figure 3.

Picture of superficial nerve neuroma.

Figure 4.

Picture showing measurement of neuroma.

Outcome and follow-up

The patient started to have some relief from his symptoms, especially in intensity. He is being monitored via follow-up in the clinic as of this writing.

Discussion

Syndesmotic injuries comprise approximately 10% of all ankle fractures and 11% of ankle sprains.¹ While syndesmotic injuries are associated with ankle fractures (especially Weber C), they can also be limited to ligamentous injuries. The superficial peroneal nerve (SPN) is a branch of the common peroneal nerve which bifurcates into a deep peroneal branch and a superficial peroneal branch at the level of the fibular head.^{2 3} The sensory branch of the SPN supplies the lateral ankle and dorsum of the foot.

Patient’s perspective.

I thought initially that it was usual pain after a big surgery, but its persistence and different nature from usual pain make me present to clinic again. The pain was not a discomfort but like pins and needles.

Learning points.

• Peripheral lower limb neuromas are debilitating.

• Conservative treatment can only decrease symptom intensity—it cannot cure neuromas.

• Dissection should be performed carefully, and neurovascular structures must be identified and protected when implanting devices, even and especially when minimal approach devices are used.