Abstract
1st MTP arthrodesis often alleviates pain in osteoarthritis of hallux, long term outcomes vary, yet there is little known about potentially modifiable changes in the small muscles of the foot and hallux. This study was performed to determine the changes in the size of the Intrinsic Foot Muscles (IFMs) after the arthrodesis of the 1st metatarsophalangeal (MTP) joint by comparing the cross-sectional area (CSA) and muscle thickness (MT) of Abductor Hallucis (AbH), Flexor Digitorum Brevis (FDB) and Flexor Hallucis Brevis (FHB) between surgical and non-surgical feet. A convenience sample of 18 feet of 9 subjects (age: 57.56±9.07, weight: 81.33±1.32kg, height: 163.26±11.03cm) with a unilateral history of 1st MTP arthrodesis was recruited. B-mode ultrasound images were collected during sitting and standing positions with a wireless 8-MHz transducer. Hand-held dynamometer was used to measure toe flexion strength. CSA and MT of the surgical feet were significantly lower (P<0.05) for AbH and FHB in both positions. For FDB, the significant difference (P<0.05) was smaller MT in standing. Significantly lower (P<0.05) toe strength was observed in involved toe compared to uninvolved. Greater correlations were seen between toe strength and CSA of FHB and AbH in uninvolved toes compared with involved toes. IFMs in the surgical foot exhibited reduced CSA and MT. Weak core muscles of the foot may result in transmission of shock and forces to the foot skeleton which can lead to skeletal problems such as metatarsalgia, IP joint arthritis etc. that are seen as post-surgical complications. There is nothing in literature that delineates the rehabilitation of foot in this group of patients after surgery. This directs surgeons and clinicians to integrate IFM training in the rehabilitation programs after surgery. Developing appropriate rehabilitation protocols for these patients may help in preventions of post-surgical complications.