We present a case of a 14 year old who sustained an isolated injury to her foot while horse riding. X-rays demonstrated a medial and plantar dislocation at the level of the talo-navicular and calcaneo-cuboid joint, with associated fractures of the cuboid and navicular. This was treated initially with open reduction and fixation with kirschner wires as the injury was grossly unstable and reduction difficult to maintain with casting alone. CT scan was then performed prior which confirmed satisfactory reduction of the dislocation and fixation with the k wires so these were left in situ and the navicular fracture reduced and fixed with a barouk screw.

The Chopart joint was first described by French surgeon Francois Chopart as the talo-navicular and calcaneo-cuboid joints were a practical level for amputation. Injury here is a rare but missed in 40% at presentation. Pure dislocation occurs in 10–25% with most having concomitant fractures. The Chopart joint has critical role in balance and stability in normal gait. Early recognition allows prompt reduction and fixation of these injuries which has been associated with a better outcome. However these are severe injuries and patients should be counselled on potential long term functional impairment even with optimal management.

The aim of this study is to assess the discrepancy between weight bearing long leg radiographs and supine MRI alignment. There is currently increasing interest in the use of MRI to assess knee alignment and develop custom made cutting blocks utilising this data. However in almost all units MRI scans are performed supine and it is recognised that knee alignment can alter with weight bearing. 46 patients underwent MRI scans as pre-operative planning for Biomet signature total knee replacement and the measure of varus or valgus deformity on MRI was obtained from the plan produced by Biomet Signature software system. 41 of these patients had long leg weight bearing radiographs performed. 33 of these radiographs were amenable to measuring the knee alignment on the picture archiving and communication system (PACS). These measurements were performed by two assessors and inter-observer reliability was satisfactory. There was a significant difference between the alignment as measured on supine MRI compared with weight bearing long leg films. In knee arthroplasty one of the aims is to correct the biomechanical axis of the knee and one of the appeals of custom made cutting blocks is that this can be achieved more easily. However it is important to realise that alignment is not a static value and thus correcting supine alignment may not necessarily result in correction of weight bearing alignment.