The Supine Internal Rotation Test: A Pilot Study Evaluating Tibial Internal Rotation in Grade III Posterior Cruciate Ligament Tears
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A Pilot Study Evaluating Tibial Internal Rotation in Grade III Posterior Cruciate Ligament Tears
Samuel G. Moulton 1 2 3
Tyler R. Cram 0 1 2
MA 1 2
ATC 1 2
OTC 1 2
Evan W. James 1 2 3
BS 1 2
Grant J. Dornan 1 2 3
MSc 1 2
Nicholas I. Kennedy 1 2 3
Robert F. LaPrade ) 0 1 2 3
Investigation performed at The Steadman Clinic 1 2
0 The Steadman Clinic , Vail, Colorado , USA. One or more of the authors has declared the following potential conflict of interest or source of funding: R.F.L. receives royalties from Arthrex and Smith & Nephew; is a paid consultant for Arthrex, Ossur, and Smith & Nephew; and receives research support from Arthrex, Smith & Nephew , Ossur, and Linvatec
1 Steadman Clinic , 181 West Meadow Drive, Suite 400, Vail, CO 81657
2 and the Steadman Philippon Research Institute , Vail, Colorado , USA
3 Steadman Philippon Research Institute , Vail, Colorado , USA
Background: Biomechanical studies have reported that the posterior cruciate ligament (PCL) functions as a restraint against excessive tibial internal rotation at higher degrees of knee flexion. Purpose: To investigate the use of a supine internal rotation (IR) test for the diagnosis of grade III PCL injuries. The hypothesis was that internal rotation would be greater in patients with grade III PCL injuries compared with other knee injuries and that the supine IR test would demonstrate excellent diagnostic accuracy. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A consecutive series of 309 patients underwent arthroscopic and/or open knee ligament reconstruction surgery. Seven patients were excluded based on the inability to perform a side-to-side comparison of internal rotation. Tibial internal rotation was assessed bilaterally on 302 patients during examination under anesthesia by a single orthopaedic surgeon measuring tibial tubercle excursion (mm) while applying internal rotation torque. Internal rotation was graded from 0 to 4 at 60 , 75 , 90 , 105 , and 120 of knee flexion. Data were collected and stored prospectively. The optimal threshold for the supine IR test was chosen based on maximization of the Youden index. Diagnostic accuracy parameters were calculated. Multiple logistic regression models were constructed to assess the influence of other knee pathologies on diagnostic accuracy. Results: Examination of the 22 PCL-deficient knees demonstrated an increase in tibial internal rotation at 60 , 75 , 90 , 105 , and 120 of knee flexion. The supine IR test had a sensitivity of 95.5%, a specificity of 97.1%, a positive predictive value of 72.4%, and a negative predictive value of 99.6% for the diagnosis of grade III PCL injuries. Posterolateral corner injury had a significant interaction with the supine IR test, increasing its sensitivity and decreasing its specificity. Conclusion: PCL-deficient knees demonstrated an increase in the side-to-side difference in tibial internal rotation compared with other knee pathologies. The supine IR test offers high sensitivity and specificity for grade III PCL injuries and may represent a useful adjunct for diagnosing PCL injuries.
posterior cruciate ligament; internal rotation; diagnostic accuracy; supine internal rotation test
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The posterior cruciate ligament (PCL) plays a pivotal role in
the knee as the primary restraint against posterior tibial
translation.2,8 The incidence of PCL tears has been reported
to vary widely from 1% to 44% of all acute knee injuries,
although the reported incidence in the general population
(3%) is lower than the 37% incidence in the traumatic setting
of patients presenting with knee hemarthroses.17,27,30
Injuries are often the result of acute sports trauma or motor
vehicle accidents.24 While the optimal reconstruction
technique is still debated, nonsurgical management of isolated
and combined grade III PCL injuries has been reported to
lead to decreased knee function and early development of
osteoarthritis.1,22 Additionally, isolated PCL tears have
been reported to alter gait patterns, which can lead to
degenerative changes and a decreased activity level in the
long term.5,20
Accurate assessment of PCL integrity is an essential
component of evaluating patients with acute or chronic
knee injury. A typical clinical evaluation requires synthesis
of data obtained on history, physical examination, and
imaging. On history, patients may report falling on a flexed
knee or the classic dashboard mechanism of injury.15
Physical examination tests for assessing PCL integrity
include the posterior drawer test, quadriceps active test,
and posterior sag sign. In a systematic review of PCL
physical examination maneuvers, Kopkow et al11 concluded that
no single test could be deemed the most useful due to the
lack of unbiased data on reported diagnostic accuracies.
However, the diagnostic accuracy of physical examination
for PCL injuries could be increased when examination
maneuvers were used in combinatio (...truncated)