Functional hallux limitus (FHL) as a potential predisposing factor for anterior knee pain syndrome (AKPS). Results after endoscopic tenolysis of the flexor hallucis longus tendon: A prospective cohort study

Abstract

Anterior knee pain syndrome (AKPS) is one of the most common musculoskeletal disorders. Functional hallux limitus (FHL) is a loss of metatarsophalangeal joint extension during the second half of the single-support phase. It constitutes a “sagittal plane blockade” attributed to a tendon glide limitation, namely the flexor hallucis longus (FHL) at the level of its retrotalar pulley (tenodesis effect). The aim of our study was to establish a causative relationship between FHL and AKPS and present a new treatment strategy for the AKPS. We prospectively studied a group of patients with AKPS and FHL treated with endoscopic tenolysis of the flexor hallucis longus (FHL) tendon. Inclusion criteria were failed conservative treatment for the AKPS and positive Stretch test for the diagnosis of FHL. Patients with known posture and gait pathology were excluded. Gait analysis performed before and after the operation focused on static, postural and dynamic parameters. Clinical questionnaires were used prospectively pre- and postoperatively. Statistical analysis was performed with SPPS for Mac (P < 0.05). Thirty-five patients were included in our study group (m/f - 39/61%). The mean age was 39-years-old (range 18–69). The patients underwent a posterior hindfoot arthroscopic release of the FHL tendon at the level of its retrotalar pulley, which was dissected. There were no complications encountered postoperatively. All patients did weight bear from day 1. Patellofemoral pain was found in 20% of patients postoperatively as compared to 100% preoperatively (P < 0.05). The area of pressure under the first metatarsal head was statistically significantly increased after the operation (P < 0.05). The average pressure under the tip of the hallux was statistically significantly lower in all patients after the FHL tenolysis. The time of support under the head of the first metatarsal head in dynamic conditions did significantly increase following the operation. (P < 0.05). Based on the Euroqol scores 85% of patients reported very good and excellent results postoperatively (P < 0.05). FHL disrupts the foot stability mechanisms leading to an asynchronous mistimed gait that alters the biomechanics of the lower limb. The substantial static and postural gait favorable changes, highlight the biomechanical importance of the FHL in the etiology of AKPS and also the safety and efficacy of our endoscopic technique pertaining to its treatment. FHL can be considered as a factor implicated in the pathogenesis of AKPS. Arthroscopic release can be considered as an efficacious and safe treatment providing satisfactory results. Additional research studies with larger population groups are warranted.