Area of the plateau depression and higher age predict post-operative subsidence in split-depression lateral tibial fracture

Introduction: The aim of this study was to determine factors that affect post-operative subsidence in split-depression lateral plateau tibial fracture (OTA/AO 41B3.1) which was treated with raft construct through a locking plate.

Patients and methods: The retrospective study evaluated all split-depression lateral plateau tibial fracture cases treated with raft construct through a locking plate between 01/2015 and 04/2020 with a minimum of 12-month follow-up. Data on the patients' age, sex, time from injury to surgery, type of plate, and use of subchondral bone defect filler were retrieved from the hospital database. The measurements of total plateau area (TPA), depressed lateral plateau area (DPA), and maximal plateau depression (MPD) were performed on the patients' pre-operative CT scans. The percentage of DPA to TPA (%DPA) was calculated. Post-operative radiographs were used for the evaluation of plateau subsidence. A subsidence greater than 2 mm was considered a failure.

Results: There were 41 consecutive cases of split-depression lateral plateau tibial fracture in the reviewed period. Five cases were excluded, three of them were lost to follow up, 1 patient had no pre-operative CT scan and 1 had a history of cancer. A failure was identified in 11 (31%) cases. Patients in the failure group were older (61.0 vs 50.7 years, p = 0.01), and had a higher incidence of fractures extending into intercondylar eminence (100% vs 56%, p = 0.02). Multiple logistic regression identified DPA (OR = 3.6; 95%CI 1.4-9.5, p < 0.01) and age (OR = 1.2; 95% CI 1.0-1.4, p = 0.02) as predictive factors for plateau subsidence. DPA cut-off value for predicting subsidence greater than 2 mm was 5.8 cm² [Area Under the ROC Curve 0.89 (95% CI 0.74-0.97), sensitivity 91%, specificity 80%, p < 0.01)].

Conclusion: Age and depressed lateral plateau area (DPA) in split-depression lateral plateau tibial fracture treated with raft construct through a locking plate are risk factors for post-operative subsidence greater than 2 mm.