Aims. The aim of this study was to assess the safety and clinical outcome of patients with a femoral shaft fracture and a previous complex post-traumatic femoral malunion who were treated with a clamshell osteotomy and fixation with an intramedullary nail (IMN). Methods. The study involved a retrospective analysis of 23 patients. All had a previous, operatively managed, femoral shaft fracture with malunion due to hardware failure. They were treated with a clamshell osteotomy between May 2015 and March 2020. The mean age was 42.6 years (26 to 62) and 15 (65.2%) were male. The mean follow-up was 2.3 years (1 to 5). Details from their medical records were analyzed. Clinical outcomes were assessed using the quality of correction of the deformity, functional recovery, the healing time of the fracture, and complications. Results. The mean length of time between the initial injury and surgery was 4.5 years (3 to 10). The mean operating time was 2.8 hours (2.05 to 4.4)), and the mean blood loss was 850 ml (650 to 1,020). Complications occurred in five patients (21.7%): two with wound necrosis, and three with deep vein thrombosis. The mean coronal deformity was significantly corrected from 17.78° (SD 4.62°) preoperatively to 1.35° (SD 1.72°) postoperatively (p < 0.001), and the mean sagittal deformity was significantly corrected from 20.65° (SD 5.88°) preoperatively to 1.61° (SD 1.95°; p < 0.001) postoperatively. The mean leg length discrepancy was significantly corrected from 3.57 cm (SD 1.27) preoperatively to 1.13 cm (SD 0.76) postoperatively (p < 0.001). All fractures healed at a mean of seven months (4 to 12) postoperatively. The mean Lower Extremity Functional Scale score improved significantly from 45.4 (SD 9.1) preoperatively to 66.2 (SD 5.5) postoperatively (p < 0.001). Partial cortical nonunion in the deformed segment occurred in eight patients (34.8%) and healed at a mean of 2.4 years (2 to 3) postoperatively. Conclusion. A clamshell osteotomy combined with IMN fixation in the treatment of patients with a femoral shaft fracture and a previous post-traumatic femoral malunion achieved excellent outcomes. Partial cortical nonunions in the deformed segment also healed satisfactorily. Cite this article: Bone Joint J 2023;105-B(4):449–454

Purpose: Treatment of complex diaphyseal malunions is challenging. It requires extensive preoperative planning and precise operative technique. A single technique has not been generalizable secondary to the limitations of each type of osteotomy. A simpler method was developed to manage these deformities. Method: Ten patients with complex diaphyseal mal-unions (4 femoral, 6 tibial) underwent a clamshell osteotomy. Indications for surgery included pain at adjacent joints and deformity. Preoperative evaluation included deformity characterization. The malunited segment was identified on biplanar radiographs. After exposure the malunited segment was transected perpendicular to the normal diaphysis proximally and distally. The transected segment was again osteotomized about its long axis and wedged open with a lamina spreader, similar to opening a clamshell. The surgical approach was sealed to retain the subsequent reamings. The proximal and distal segments of the diaphysis were aligned using the intramedullary nail as an anatomic axis template and the opposite extremity as a length and rotation template. Partial weight-bearing mobilization with crutches began immediately and progressed based on clinical and radiographic evaluation. Followup ranged from 6–52 months. Results: Radiographic angular corrections were complete in each case and ranged from 2–20 degrees in the coronal plane, 0–32 degrees in the sagittal plane, and 0–25 degrees in the axial plane (rotation). Correction of length ranged from 0–5 centimeters, restoring leg length to within 2 centimeters in all cases. All osteotomies were healed both clinically and radiographically by 6 months. All patients were ambulatory without assistive devices by the time of the most recent followup. Conclusion: The proposed osteotomy provides a generalizable way to correct many forms of diaphyseal mal-unions by acting as a bypass in realigning the anatomic axis of the long bone using a reamed intramedullary nail as a template