Incidence and Fracture Morphology of Posterolateral Fragments in Lateral and Bicondylar Tibial Plateau Fractures

Abstract

Objectives: This study aimed to evaluate the incidence and morphologic features of posterolateral fragments in lateral and bicondylar tibial plateau fractures. Design: This study used retrospective chart and computed tomography (CT) reviews. Setting: The study was conducted in a university hospital. Patients: All patients in whom lateral and bicondylar tibial plateau fractures had been diagnosed from May 2005 to December 2011 were reviewed. Main Outcome Measurements: Two hundred seventy-eight OTA type B and type C tibial plateau fractures were identified using a retrospective chart review. Of the 197 patients who underwent CTs before surgery, 7 CTs were excluded because they had no sagittal or axial view, and the remaining 190 cases were enrolled to determine the incidence and morphologic characteristics of posterolateral fragments. The parameters for the morphologic evaluation included the lateral major articular fracture angle, posterior major articular fracture angle, diagonal distance, lateral anteroposterior distance (LAPD), posterior horizontal distances, posterior cortical height, sagittal fracture angle, and articular surface area. The displacement of posterolateral fragment was measured on axial image and classified as none, minor, or major by a gap of 5 mm. Results: The incidence of posterolateral fragments included 84 cases (44.2%). Based on the OTA fracture classification system, 37 type B (35.9%) and 47 type C (54%) posterolateral fragments were identified. The mean lateral major articular fracture angle was 12.69 degrees (range, -56.02 to 72.44 degrees), and the mean posterior major articular fracture angle was 19.13 degrees (range, -39.47 to 61.10 degrees). The average diagonal distance was 32.75 mm (range, 15.03-59.14 mm). The LAPD averaged 10.22 mm (range, -11.18 to 31.17 mm), and the mean posterior horizontal distance was 22.93 mm (range, 4.1 to 49.95 mm). The average posterior cortical height was 31.12 mm (range, 10.84-63.93 mm), and the average sagittal fracture angle was 78.48 degrees (range, 41.69-105.12 degrees). The mean articular surface area was 522.18 mm(2) (14.5%) of the total tibial articular surface. Conclusions: Posterolateral fragments are not uncommon in lateral and bicondylar tibial plateaus. This fragment has an inverted conical shape that is in a vertically oriented pattern and occupied nearly one-third of the surface area of the lateral tibial plateau. The preoperative CT measurement, especially for the LAPD, can be used for determining the best fixation strategy for the posterolateral fragment.