A radiographic zone-based approach to predict meniscus injury in lateral tibial plateau fracture

ObjectivesThere is limited data regarding meniscal injury and it's association to fracture location and articular impaction/displacement (AID) in tibial plateau fractures. The purpose of this study was to predict lateral meniscal injury in tibial plateau fractures, based on location and extent of AID as visualized on pre op CT images.DesignRetrospective review study.SettingLevel I academic trauma center.PatientsWe retrospectively reviewed lateral tibia plateau fracture patients that were treated operatively using CPT codes 27535 and 27536. Two hundred patients were identified. Inclusion criteria were lateral tibia plateau fracture, age of 18 years or older, and documented direct examination of lateral meniscus integrity intraoperatively. Seventy patients met inclusion criteria.InterventionThe injured lateral tibial plateau was divided into four quadrants on pre-operative CT and maximum AID was measured. The zone of fracture was defined as the location of largest AID (Image-1). All patients had an arthrotomy at the time of surgery to evaluate the integrity of the meniscus. Intra operative data regarding meniscal integrity and preoperative CT data were analyzed. Logistic regression was used to estimate what effect zone and amount of AID had on predicting the meniscal injury. Receiver operating characteristic (ROC) analysis was performed to determine cut off points for high sensitivity/specificity.Main outcome measurementsAmount and area of depression in the lateral tibial plateau as relates to meniscal injury.ResultsMean age was (45.1 ± 12.9) years. Twelve had Schatzker type I and 58 had type II fractures. Twenty-two patients had meniscus injury (MI) and forty-eight patients did not have a meniscus injury (NMI). Mean AID for MI was 12.48 mm ± 7.17 mm and 6.4 mm ± 4.3 mm for NMI (p<0.01). In MI group, largest AID was in Posterolateral (PL) zone(17.58 mm ± 8.9 mm) followed by Anteromedial (AM) zone (13.3 mm ± 7.2 mm) and Anterolateral (AL) zone (9.4 mm ± 5.8 mm). In NMI group largest AID was in AL zone (8.52 mm ± 2.6 mm) followed by AM zone (8.04 mm ± 5.4 mm) and PL zone (7.75 mm ± 2.35 mm). Patients with PL zone involvement had a lower meniscus tear rate compare to other zones. Logistic regression revealed that for every 1 mm increase in AID there is a 21% increase chance of meniscus tear (p<0.01). Comparison of the zones indicated that for the same AID, AL and AM zone fractures have 7.3 and 5.6 times increase risk of meniscus tear, respectively, as compared to PL zone (p<0.05). ROC analysis revealed that AID of 4.3 mm as a cut off point provides 100% sensitivity for diagnosis of meniscus tear.ConclusionWith 1 mm increase in AID there is a 21% increase in chance of meniscal tear. With the same AID, AL and AM zone fractures have a significantly higher chance of having a meniscal tear. AID of 4.3 mm provides 100% sensitivity to predict meniscal tear in lateral tibia plateau fracture. These values are useful in predicting pre op meniscal tear without MRI.