Anatomical variations of peroneus tertius and its clinical implications: case report with systematic literature...

Peroneus tertius (PT) or Fibularis tertius, a muscle of the anterior compartment of the leg is very distinctive to the Homo sapiens. This is because of the evolutionary acquisition of bipedal gait along with the eversion of the foot, which are unique to humans. It is considered as the fifth tendon of the extensor digitorum longus. Variations in the attachments of PT can cause stress fractures like the Jones fracture. PT has been extensively used in tendoplasty, tendon transfer and resection of the foot. The study aims to transpose the knowledge in variations of the morphology of PT from bench to bedside.

Routine dissection of a 64-year-old male cadaver revealed bilateral variations in the insertion of PT. This was documented photographically. The findings prompted a systematic literature review on the morphological variations of PT. An exhaustive search was undertaken through PubMed and Google Scholar databases to identify the published literature related to variations in the morphology of PT. Related anatomical studies of the variations in peroneus tertius were identified and a review of the literature was performed.

Variations in the insertion of PT were observed bilaterally in the cadaver dissected by us. Statistical analysis revealed the absence of PT in 7.03% of lower limbs. 10% of studies showed accessory and duplicated PT each. Out of 20 articles reviewed, 51 lower limbs showed variation in origin, 230 lower limbs showed variations in insertion and 161 lower limbs showed other variations.

PT muscle flap and tendon grafts are used in correcting the laxity of the ankle joint and foot drop. Absence of PT plays a crucial role in altering the mechanics of stress fractures of the 5th metatarsal. Thus, knowledge of the morphology of PT is crucial for plastic surgeons and orthopedic surgeons.