Surgical Outcomes after Simple Coalition Bar Excision in Naviculo-Medial Cuneiform Coalition in Adults

CATEGORY: Midfoot/Forefoot; Other INTRODUCTION/PURPOSE: Coalition of the naviculo-medial cuneiform joint (NCJ) is a relatively rare condition among the tarsal bone coalitions. Thus, optimal treatment is still largely unknown. There is a paucity of literature, with few cases documenting arthrodesis of the NCJ in adults with varied outcomes. As the NCJ contributes to the majority of motion along the medial column of the foot, arthrodesis of the joint may cause excessive stress on adjacent joints. Furthermore, the nonunion rate of NCJ is reportedly high, ranging from 3 to 15%. The purpose of this study was to report the outcomes of simple coalition bar excision in patients with NCJ coalition. Additionally, we investigated preoperative abnormal conditions around the NCJ using weight bearing computed tomography (WBCT). METHODS: We retrospectively identified 21 feet in 18 prospectively followed patients from 2010 to 2018 who underwent simple coalition bar excision of NCJ in our institution. Chart review was performed to retrieve demographic data of the patients, clinical presentation findings, and concomitant procedures with coalition bar excision. Radiographically, the location and morphological pattern of the coalition were analyzed. Several angular parameters including medial arch sag angle (MASA) were measured on weightbearing x-rays to see if there are any angular collapse at NCJ after coalition bar excision (Figure 1). The existence of abnormal conditions adjacent to the NCJ such as arthritis of the first and second tarsometatarsal joint (TMTJ) and talonavicular joint (TNJ) were assessed using WBCT (n=17). Clinically, pre- and postoperative visual analogue scale (VAS) and foot function index (FFI) were compared to assess for improvement in patient-reported outcomes. RESULTS: The mean age of the patients was 30.9 years (range, 16-62) and the follow-up was 15.9 months (range, 12-24). Majority of the patient had fibrous coalition at the plantar-medial aspect and only one patient had bony coalition. The morphology of fibrous coalition was classified as irregular (n=8), cystic (n=1), and combined (n=11) based on CT findings. Intraoperatively, the motion of the NCJ was identified in every patient after coalition bar excision. WBCT revealed 15 feet (71.4%) having at least one abnormal finding around the NCJ (First TMTJ plantar gap; n=10, second TMTJ narrowing; n=9, first TMTJ spur & irregularity; n=2, TNJ spur; n=1). Pre- and postoperative MASA did not change significantly (p=0.932). There was significant improvement in VAS and FFI at final follow-up (p<0.001) CONCLUSION: A considerable proportion of patients with NCJ coalition had at least one radiographically arthritic feature at adjacent joints preoperatively, which may be caused by the restriction in motion associated with NJC coalition. Simple coalition bar excision in adults resulted in satisfactory outcomes without NC joint angular deterioration, while restoring motion at the joint.