Anomalous tibialis posterior muscle as an etiologic factor of hallux valgus

Abstract

The role of an anomalous tibialis posterior (TP) tendon in the etiology of hallux valgus (HV) deformity was investigated in four stages: clinical, anatomical, neurological, and operative. In the clinical stage, the patients were instructed to planter flex and invert the foot to contract the TP tendon. Attempts to correct the deformity passively were not possible and resulted in moderate pain in all patients (197 feet). When the foot was in dorsiflexion and everted (TP tendon was relaxed) the deformity was easily corrected without any pain in 196 feet (99.5%). In the second stage (anatomical), 10 cadavers (20 feet) with HV deformity and 10 cadavers (20 feet) without any foot deformity were dissected. An abnormal expansion of TP tendon into the oblique part of adductor hallucis was found consistently in all HV feet. The tendinous expansion was absent in all normal feet studied. Also when traction was applied to TP tendon, an increase in the metatarsophalangeal (MP) angle of the big toe was observed in all HV feet, but not in the control group. In the third group (neurological), faradic stimulation was applied to the TP muscle in 7 patients with HV deformity and 7 without deformity. The MP angle was increased in HV patients, but no change was observed in the control group. In the fourth stage, 11 patients (18 feet) surgically operated for HV deformity by proximal metatarsal osteotomy and excision of the band anchoring TP tendon to the oblique part of adductor hallucis. The results were excellent in 10 patients (17 feet) even after a minimum 2.5 year follow-up. Also, in two patients who were operated by different procedures with poor results, the TP tendon was lengthened by Z-plasty and they were completely pain free.Our data show the dynamic role of anomalous expansions of the TP tendon into the oblique part of adductor hallucis muscle in HV patients. We suggest this expansion be excised in addition to other operative procedures selected for the surgical treatment of HV patients.

High Heritability of Hallux Valgus and Lesser Toe Deformities in Adult Men and Women

“…It is also possible that anomalous muscle insertions may predispose to hallux valgus. An analysis of cadaver feet by Gunal et al () revealed that an abnormal tendinous expansion of the tibialis posterior tendon onto the oblique head of adductor hallucis was present in all feet with hallux valgus and none without. Theoretically, this anatomic variation would provide a mechanical advantage of adductor hallucis over abductor hallucis, thereby pulling the hallux laterally.…”

Ultrasonic evaluation of the abductor hallucis muscle in hallux valgus: a cross-sectional observational study

“…Bony abnormalities (round-shaped first metatarsal head [14], long first metatarsal [15], bipartite medial sesamoids [16]) and muscular abnormalities (accessory extensor hallucis longus tendon [17], accessory tibialis posterior tendon [18]) have also been linked to the deformity. It is likely that a combination of factors contribute to the development of hallux valgus.…”