The necessity of clinical application of tibial reduction for detection of underestimated posterolateral rotatory instability in combined posterior cruciate ligament and posterolateral corner deficient knee

The purpose of this study was to evaluate the usefulness of tibial reduction during dial test for clinical detection of underestimated posterolateral rotatory instability (PLRI) in combined posterior cruciate ligament (PCL)-posterolateral corner (PLC) deficient knee in terms of external rotation laxity and clinical outcomes. Twenty-one patients who classified as grade I PLRI using dial test with subluxated tibia, but classified as grade II with tibial reduction evaluated retrospectively. The mean follow-up was 39.3 months (range 24-61 months). Each patient was evaluated by the following variables: posterior translation and varus laxity on radiograph, KT-1000 arthrometer, dial test (reduced and subluxated position), International Knee Documentation Committee, Orthopadische Arbeitsgruppe Knie scoring system and Tegner activity scale. There were significant improvements in posterior tibial translation (8.6 +/- A 2.0 to 2.1 +/- A 1.0 mm; P < 0.001), varus laxity (3.3 +/- A 1.3 to 1.4 +/- A 0.5 mm; P < 0.001) and external rotation (13.2A degrees A A +/- A 0.8A degrees to 3.6A degrees A A +/- A 1.1A degrees at 30A degrees, 13.3A degrees A A +/- A 0.9A degrees to 3.6A degrees A A +/- A 0.9A degrees at 90A degrees; P < 0.001). The clinical scores were improved significantly at the last follow-up (P < 0.001). The external tibial rotation during dial test with tibial reduction increased from 6.8A degrees A A +/- A 0.9 to 13.2A degrees A A +/- A 0.8A degrees at 30A degrees of knee flexion, from 7.0A degrees A A +/- A 0.8A degrees to 13.3A degrees A A +/- A 0.9A degrees at 90A degrees (P < 0.001). The clinical application of reduction of posteriorly subluxated tibia during the dial test was essential for an appropriate treatment of underestimated PLRI in combined PCL-PLC deficient knee. Retrospective case series, Level IV.