Posterior Cruciate Ligament and Posterolateral Corner Deficiency Results in a Reverse Pivot Shift

Abstract

Background As measured via static stability tests, the PCL is the dominant restraint to posterior tibial translation while the posterolateral corner is the dominant restraint to external tibial rotation. However, these uniplanar static tests may not predict multiplanar instability. The reverse pivot shift is a dynamic examination maneuver that may identify complex knee instability. Questions/purposes In this cadaver study, we asked whether (1) isolated sectioning or (2) combined sectioning of the PCL and posterolateral corner increased the magnitude of the reverse pivot shift and (3) the magnitude of the reverse pivot shift correlated with static external rotation or posterior drawer testing. Methods In Group I, we sectioned the PCL followed by structures of the posterolateral corner. In Group II, we sectioned the posterolateral corner structures before sectioning the PCL. We performed posterior drawer, external rotation tests, and mechanized reverse pivot shift for each specimen under each condition and measured translations via navigation. Results Isolated sectioning of the PCL or posterolateral corner had no effect on the reverse pivot shift. Conversely, combined sectioning of the PCL and posterolateral corner structures increased the magnitude of the reverse pivot shift. The magnitude of the reverse pivot shift correlated with the posterior drawer and external rotation tests. Conclusions Combined sectioning of the PCL and posterolateral corner was required to cause an increase in the magnitude of the mechanized reverse pivot shift. The reverse pivot shift correlated with both static measures of stability. Clinical RelevanceCombined injury to the PCL and posterolateral corner should be considered in the presence of a positive reverse pivot shift.

The Effect of Proximal Tibial Slope on Dynamic Stability Testing of the Posterior Cruciate Ligament– and Posterolateral Corner–Deficient Knee

“…12 In a recent cadaveric experiment, our group utilized computer-assisted navigation to describe the effects of serial sectioning of the PCL and PLC structures on the magnitude of a mechanized RPS. 19 We demonstrated that combined sectioning of both the PCL and PLC structures was necessary to elicit a significant increase in magnitude of the RPS. Consequently, for the purposes of this study, we chose to section the PCL and PLC structures to induce a mechanized RPS and determine if alterations in tibial slope could influence the magnitude of this dynamic test.…”

“…14 Our laboratory has developed a mechanized pivot-shift device, which in combination with computer navigation can be used to quantify translations of the tibia relative to the femur during the pivot-shift and RPS maneuver. 16,19 In a previous cadaveric study, we demonstrated that the combined sectioning of both the PCL and the structures of the PLC was necessary to generate a significant increase in the magnitude of the RPS relative to the intact state. 19 Furthermore, the magnitude of the RPS appeared to demonstrate a strong correlation to the magnitude of the posterior drawer and external rotation tests.…”

“…19 This correlation can likely be attributed to both rotational and translational vectors that each contribute to the RPS. In the current investigation, alterations of tibial slope had a significant effect on the magnitude of posterior translation but did not affect the rotational stability as measured by the dial test.…”

The use of a robotic tibial rotation device and an electromagnetic tracking system to accurately reproduce the clinical dial test

“…There are many ways in which this test has been reproduced with the main focus on increased external rotation on the injured side as the key measure of potential PLC injury. Pearle and others have abandoned the use of rotation alone and have incorporated lateral compartment translation as the key measure [ 12 , 25 ]. The use of the electromagnetic tracking system during the dial test allows for a measure of proximal tibial translation.…”

“…In fact, isolated increased external tibial axial rotation may not identify the patient with a PLC injury without additional manoeuvres during the examination [ 13 , 14 ]. A description of rotatory instability by measuring the relative translation of the lateral compartment of the knee with respect to the medial compartment appears to provide better accuracy in the diagnosis of a PLC injury [ 7 , 25 ].…”