Bae JH, Choi IC, Suh SW, Lim HC, Bae Nha KW, Wang JH. Arthroscopy: The Journal of Arthroscopic and Related Surgery. 2008;24(5):593-598. Abstracted by Tanya Smith PT ScD, COMT from Anchorage, Alaska
The purpose of this study was to assess the reliability of the Dial Test in identifying Posterolateral rotatory instability (PLRI) of the knee. The severity of the PLRI was correlated to the amount of external rotation of the tibia when compared to the uninjured knee. Left undiagnosed and untreated PLRI can result in significant impairment of the knee.
Fourteen paired fresh-frozen cadaveric lower extremities without evidence of injury or instability were used in this study. Lower extremities were fixed into a custom made isotonic rotation machine with knee flexed at 30 degrees. In Group I the lateral collateral ligament, popliteofibular ligament (PFL), popliteus tendon and the Posterior cruciate ligament (PCL) were cut serially. Group II the knee was at 30 degrees of knee flexion; the PCL, Lateral collateral ligament, popliteofibular ligament, and the popliteus tendon were cut. External rotation of the tibia was than measured using a 6-Nm rotational torque.
There was a significant increase in external rotation of Group I after cutting of the 3 posterolateral structures and in group II after cutting of the PCL and 2 of the posterolateral structures. The dial test was determined as a valuable tool in clinical diagnosis when all three posterolateral structures of the LCL, PFL and popliteus tendon or the PCL combined with two other posterolateral structures are compromised. Increased external rotation that was statistically significant was not found in this study without a combination of all three structures or PCL with two structures compromise.
Some limitations of the study include: small sample size of 14 cadaveric specimens, no randomization of cutting order, and the authors did not take into account the posterolateral capsule.
The dial test compares external rotation of the tibia in 30 degrees and 90 degrees of knee flexion. If external rotation increases at 30 degrees compared with 90 degrees an isolated PLRI is suspected. If both at 30 and 90 degrees of flexion there is increased external rotation compared to uninvolved side this suggests a PCL injury combined with PLRI.
The dial test should be carried out on both involved and uninvolved sides, as there were large individual variations of tibial external rotation (33.6 + 10.6 degrees). When comparing left and right of the same specimen variation was much less (3.6 + 3.0 degrees).
The dial test alone cannot be used in the diagnosis of PLRI. It should be used in combination of clinical history, other clinical diagnostic tests and MRI. The failure to diagnose a PLRI can result in failed surgical outcomes, graft failure, pain and/or disability.
IAOM-US COMMENT
The academy advocates the use of a complete clinical history and thorough examination in the diagnosis of musculoskeletal injuries including PLRI. The mechanism of injury is thought to be a direct blow to the anteromedial tibia directed posterolaterally with knee extension or a non-contact hyperextension external rotation force. There is a high incidence of PFL, Popliteus, and biceps femoris lesions associated with concomitant ACL/PCL tears. The basic functional examination of the knee includes external rotation of the tibia at 90 degrees, AP drawer testing, Lachman’s test, anterolateral testing, varus testing as well as contractile testing of the hamstrings with external rotation or internal rotation emphasis. The dial test is a special test used in conjunction with the basic functional examination to diagnosis PLRI. The increase in tibial external rotation with the uninvolved side in the dial test has been correlated to the increase in severity of PLRI (2). Anterior tibial repositioning can also increase sensitivity of the dial test in detecting PLRI (1). The mean tibial external rotation increased 5.31 +/- 2.86 degrees at 30 degrees and 6.87 +/-3.59 at 90 degrees of knee flexion with an anterior relocation of the tibia when performing the dial test (1). Although MRI has been used as a gold standard in evaluation of knee injuries, there are no precise criteria required to diagnose PLRI of the knee. However, there is a high incidence of PLRI when at least two of the posterolateral structures are torn (3). In conclusion, multiple factors remain relevant in the diagnosis of PLRI of the knee and beginning with a though history and physical examination with proper performance of special tests can lead to improved diagnosis of PLRI.
REFERENCES
Jung YB, Nam CH, Jung HJ, Lee YS, Ko YB. The influence of tibial positioning on the diagnostic accuracy of combined posterior cruciate ligament and posterolateral rotatory instability of the knee. Clin Orthop Surg.2009;1(2):68-73.
Kim JG, Lee YS, Kim YJ, Shim JC, Ha JK, Park HA, Yang SJ, Oh SJ. Correlation between the rotational degree of the dial test and arthroscopic and physical findings in posterolateral rotatory instability. Knee Surg Sports Traumatol Arthrosc. 2010;18(1);123-9.
Vinson EN, Major NM, Helms CA. The Posterolateral Corner of the Knee. AJR. 2008;190(2):449-58.