Ultrasound Evaluation and Surgical Excision of a Fabella Causing Peroneal Neuropathy in a Track Athlete

Common fibular nerve palsy due to the Fabella: A review

One of the most common nerve palsies - common fibular nerve palsy - can be caused by the variant small sesamoid bone in the posterolateral compartment of the knee joint known as the fabella. We compared and reviewed all reported cases of common fibular nerve palsy due to fabellae in the English literature. Compression can develop spontaneously or post-surgically (total knee arthroplasty). Symptoms progress rapidly to complete foot drop. Among all the cases reviewed, 68.42% were males with a median age of 39.39 years. Fabella compression was more common in the left common fibular nerve (CFN) (63.16%). Both big (23 × 20 × 16 mm) and small (5 × 5 mm) fabellae can be responsible for compression. While diagnosis can be problematic, the treatment (either surgical fabellectomy or conservative) is relatively easy and brings quick improvement.

Common fibular nerve palsy due to fabella compression: An illustrative case report

BACKGROUND

The fabella is a sesamoid bone situated in the tendon of the lateral head of the gastrocnemius muscle behind the lateral femoral condyle. Common fibular nerve injury may occur anywhere on its course and the most common etiology remains compression at the level of the head of the fibula. Compression by a fabella is a very unusual cause of common fibular nerve palsy and only few case reports are described in the literature. We present here an illustrative case.

CASE DESCRIPTION

A 50-year-old female patient presented with a left drop-foot evolving for two weeks without pain or sensory deficit. Clinical examination revealed a paresis of the left foot dorsiflexors muscles (3/5). A compressive neuropathy of the common fibular nerve at the level of the fibula head was demonstrated by nerve conduction studies. Ultrasound of the left knee revealed nerve compression by a fabella. Early decompressive surgery was performed and the fabella was excised. We noticed an almost complete recovery probably due to early treatment (4+/5 two months after surgery).

CONCLUSIONS

Common fibular nerve palsy related to fabella compression is very uncommon. Good clinical outcome has been described at 1-2 years with an early work-up and a prompt surgical decompression.