Factors influencing postoperative residual diastasis after the operative treatment of acute Lisfranc fracture dislocation.

INTRODUCTION: Clinically, surgeons may frequently encounter residual diastasis between the medial cuneiform and 2nd metatarsal base after the operative treatment of acute Lisfranc fracture dislocations. The purpose of this study was to identify factors influencing postoperative residual diastasis. We specifically focused on the preoperative fracture pattern using 3-dimensional computed tomography (3D-CT). MATERIALS AND METHODS: Radiographic and clinical findings of 66 patients who underwent operative treatment for acute Lisfranc fracture dislocation were reviewed. Patients were grouped according to residual diastasis evaluated by weight-bearing anteroposterior radiograph of the foot at the final follow-up. Residual diastasis was defined as distance between the medial cuneiform and 2nd metatarsal base greater than the distance on the contralateral side by 2 mm or more. Demographic parameters and fracture patterns based on preoperative foot 3D-CT were compared. A paired t test was used to compare continuous numeric parameters, while a Chi-square test was used for the proportional parameters. Statistical significance was set at P value less than 0.05 for all analyses. RESULTS: The mean age at operation, sex, body mass index, and the rate of underlying diabetes were not significantly different between the two groups (P > 0.05 each). Preoperative foot 3D-CT evaluation showed that the rate of large (> 25% of 2nd tarsometatarsal joint involvement), displaced (> 2 mm) fracture fragments on the plantar side of the 2nd metatarsal base was more pronounced in the group with residual diastasis (P = 0.001), while medial wall avulsion of the 2nd metatarsal base was more frequent in the group without residual diastasis (P = 0.001). CONCLUSIONS: While treating acute Lisfranc injuries, surgeons should be aware of the presence of a 2nd metatarsal base plantar fracture. A dorsoplantar inter-fragmentary fixation can be considered if the fragment is large and displaced.