Incidence and morphology of the posteromedial fragment in bicondylar tibial plateau fractures.

OBJECTIVES

Bicondylar tibial plateau fractures featuring extensive articular involvement have a record of mixed clinical results. Recent discussion has focused on the significance of a posteromedial articular fragment in bicondylar injuries. This fragment has often gone unrecognized or has not been addressed. The posteromedial fragment is defined as any posteriorly based articular fracture of the medial plateau with the fracture line exiting the medial cortex. This study is designed to produce a detailed description of the incidence, size, and shape of this fracture, as this may be helpful in driving the choice of both approach and fixation for these injuries. Furthermore, a better understanding of this fracture's morphology may lead to a better ability to model the biomechanical reliability of laterally based locking fixation in securing the reduction of this fracture fragment.

DESIGN

Retrospective study of patient records and computed tomography scans.

SETTING

Level I university regional trauma center.

PATIENTS: All patients treated for bicondylar tibial plateau fracture from January 1, 2002, through August 31, 2007.

RESULTS

One hundred forty-eight patients were identified in the 5.5-year period, and 111 had complete computed tomography records (75%). Of 111 bicondylar tibial plateau fractures analyzed, this fragment occurred in 65 cases (59% incidence) and on average accounted for 25% of the total tibial plateau joint surface. There was greater than 5 mm of articular displacement in 55% of cases. The posteromedial fragment exhibits a vertical fracture pattern (average sagittal angle 73 degrees), suggestive of shear instability and vertical displacement.

CONCLUSIONS

Given the high frequency, significant portion of the joint involved, significant displacement, and pattern suggestive of instability, surgeons need to be cognizant of this pattern and may need to consider directly reducing and fixating this fragment through a posteromedially based approach. Overall morphologic findings of the posteromedial fragment are highly consistent with other recent data on this pattern. This information may also be useful in modeling fracture fixation for future study.