Surgical management of functional hallux limitus using cotton osteotomy/posterior muscle group lengthening and its effect on cuneiform articular angle, Medial Arch Sag Angle, and Meary's angle

Functional hallux limitus (FnHL) can arise from medial column instability caused by pathological compensation within the closed kinetic chain. This report presents a surgical case of FnHL attributed to instability at the naviculocuneiform joint (NCJ) following failed conservative management. Medial column stability was addressed with a Cotton osteotomy, using the cuneiform articular angle (CAA) to determine appropriate graft size. An Austin osteotomy and proximal Akin were performed to correct a bunion deformity, while posterior muscle group lengthening was added to reduce rearfoot-driven strain on the medial column. Medial column integrity was evaluated preoperatively and at one year postoperatively via weight-bearing lateral radiographs, assessing the medial arch sag angle (MASA), CAA, medial cuneiform height (MCH), and Meary’s angle. Confirmation bias was reduced by using radiographic angles to support subjective outcomes of procedure. Postoperative imaging demonstrated notable improvement in CAA, Meary’s angle, and MCH, confirming correction of medial column instability. MASA remained unchanged. The bunion deformity was also corrected radiographically. Clinically, the patient showed improved 1st metatarsophalangeal joint (MPJ) function, with the metatarsophalangeal-interphalangeal (MTP-IP) score increasing from 62 to 90 at one year. This appears to be the first report describing the combined use of a first metatarsal distal shaft osteotomy, Cotton osteotomy, and posterior muscle group lengthening to improve both 1st MPJ function and medial column stability during gait. A novel NC fault classification system is introduced to guide preoperative planning for medial column instability.