Complete rupture of the flexor hallucis longus tendon in an isolated closed injury. A systematic literature and qualitative analysis

Background. Complete rupture of the flexor hallucis longus tendon in an isolated closed injury is a rare event. The infrequent identification of this injury may be due to a low clinical suspicion of the flexor hallucis longus tendon being a source of pathology in closed foot and ankle injuries. This review will assess the current body of literature and analyse the clinical presentation and current concepts in management of this specific pattern of tendon injury. Method. A systematic literature search was conducted in MEDLINE and Embase to identify relevant publications. Two separate researchers independently reviewed the references identified in the literature search, with each article being assessed against published selection criteria specified in the study protocol registered with PROSPERO. Two reviewers individually examined the raw data presented in each paper that met final inclusion criteria. This data was then presented in the final analysis. Results. There were 10 documented case reports of complete rupture of the flexor hallucis longus tendon in an isolated closed injury reported in the literature. The majority of subjects were male (70%), with an average age of 38 years. The duration of prodromal symptoms ranged from 0-8 months. The most common mechanism of injury was running, seen in 30% of cases. Every documented case in the literature underwent surgical management. Common post-operative outcomes reported were individual joint range of motion and return to prior level of physical activity. Conclusion. Due to the occult nature of the injury and synergistic function of other structures in the foot, delayed presentation of closed flexor hallucis tendon rupture is common. It is unclear from the current body of literature if surgical management of this injury significantly improves patient outcomes. Current evidence from the management of open flexor hallucis longus tendon ruptures suggests that patients can achieve good functional outcomes with non-operative management. Our recommendation would be for initial non-operative treatment of closed flexor hallucis longus tendon ruptures given the potential for acceptable functional outcomes, and to avoid the potential complications associated with operative repair.