Frequency and fracture morphology of the posteromedial fragment in bicondylar tibial plateau fracture patterns

Objectives: Bicondylar tibial plateau fracture management remains therapeutically challenging, partly because of multiplanar articular comminution. This study was performed to evaluate the frequency and morphologic characteristics of the posteromedial fragment in this injury pattern. Design: Retrospective chart and radiographic review. Setting: Urban Level 1 university trauma center. Patients: Fifty-seven patients sustaining 57 Orthopedic Trauma Association (OTA) C-Type bicondylar tibial plateau fractures formed the study group. Main Outcome Measure: Between May 2000 and March 2003, 170 OTA C-Type bicondylar tibial plateau fractures were identified using an orthopaedic database. One hundred and forty-six fractures had computed tomographic (CT) scans performed prior to definitive fixation and were reviewed using the Picture Archiving and Communication System (PACS). Sixty-six (45.2%) injuries had fractures that involved the medial articular surface. Nine with suboptimal CTs were excluded, leaving 57 injuries for review. Forty-two patients demonstrated coronal plane posteromedial fragments. Morphologic evaluation of the posteromedial fragment included articular surface area, maximum posterior cortical height (PCH), and sagittal fracture angle (SFA). Results: Forty-two of 57 injuries (74%) demonstrated a posteromedial fragment that comprised a mean of 58% of the articular surface of the medial tibial plateau (range, 19%-98%) and a mean of 23% of the entire tibial plateau articular surface (range, 80-47%). Mean posteromedial fragment height was 42 mm (range, 16-59 mm), and mean sagittal fracture angle was 81 degrees (range, 33 degrees to 112 degrees). Six patients demonstrated fracture patterns not accurately identified by the AO/OTA (Arbeitsgemeinschaft fur Osteosynthese-fragen/Orthopaedic Trauma Association) fracture classification system. Conclusions: A posteromedial fragment was observed in nearly one third of the bicondylar plateau fractures evaluated. The morphologic features of this fragment may have clinical implications when using currently available laterally applied fixed-angle screw/plate implants to stabilize these injuries. Alternate or supplementary fixation methods may be required when managing this injury pattern.