Dial Test: Unrecognized Predictor of Anterior Cruciate Ligament Deficiency

Diagnosing popliteofibular ligament injuries in anterior cruciate ligament-injured knees: A prospective magnetic resonance imaging study investigating the inter- and intraobserver reliability of identification of the popliteofibular ligament

Purpose

The aim of our study was to investigate the intra- and interobserver reliability for the identification of the popliteofibular ligament (PFL) in magnetic resonance imaging (MRI) scans in patients with an anterior cruciate ligament (ACL) injury and ascertain the prevalence of PFL tears in ACL-injured knees without clinically high-grade posterolateral corner injury.

Methods

MRI readings were performed retrospectively by two surgeons on 84 patients who underwent ACL reconstruction in our department. The presence of the PFL on both sagittal and coronal images as well as the presence of PFL tears was noted. Readings were repeated 6 weeks later for one observer. The κ value was calculated to determine the intra- and interobserver reliability for identification of the PFL and the prevalence of PFL tears was ascertained.

Results

The PFL was visualized in 90.5%-91.7% of MRI scans. The intra- and interobserver reliability of visualizing the PFL on MRI had an κ value of 0.63 and 0.66 (substantially reliable), respectively. The intraobserver reliability for identification of PFL tears had an κ value of 0.26 (fair reliability). We found a 4.8% prevalence of PFL tears in ACL-injured knees.

Conclusions

There is substantially reliable intra- and interobserver reliability for the identification of the PFL on MRI scans but only fair reliability for the identification of PFL tears. A 4.8% prevalence of PFL tears in ACL-injured knees without clinically confirmed high-grade posterolateral corner injury can be observed in our series.

Level of Evidence

Level IV.

Clinically Reliable Knee Flexion Angle Measured on Stress Radiography for Quantifying Posterior Instability in Posterior Cruciate Ligament Injury

Background

After posterior cruciate ligament injury, stress radiography is a common method of quantifying posterior instability, defined as the side-to-side difference in posterior tibial displacement (PTD) between the injured knee and contralateral noninjured knee. However, no study has evaluated the reliability of PTD according to knee flexion angle (KFA) measurements on stress radiographs.

Purpose

To evaluate the test-retest reliability of stress radiographic measurements of the KFA in the noninjured knee. In addition, we established a reliable range of KFAs to indicate posterior instability by comparing results with the instability measured at 90° KFA, which is considered the gold standard.

Study Design

Cohort study (diagnosis); Level of evidence, 3.

Methods

We evaluated patients who had undergone bilateral stress radiographic examinations at least 5 times for ligament injuries between January 2013 and November 2019. All examinations were performed on a Telos device with a 150-N posterior load. A total of 120 knees and 644 stress radiographs were enrolled. We measured the KFA and PTD on stress radiographs and evaluated the reliability of repeated PTD measurement and the correlation between KFA and PTD.

Results

The distribution of the actual noninjured knee KFA ranged from 56.9° to 106.7°. Among the 644 radiographs, 155 (24.1%) showed KFAs between 85° and 95°, and 287 (44.6%) showed KFAs between 80° and 85°. A significant correlation was found between KFA and PTD (P < .001), and the intrapatient intraclass correlation coefficient (ICC) was 0.788. A KFA range of 85° to 92° satisfied the criteria of high ICC (0.885) and nonsignificant correlation between KFA and PTD (P = .055) and thus was considered a reliable range of KFAs for quantifying posterior instability. We found no significant risk factors for measurement error, including age (P = .674), sex (P = .328), height (P = .957), weight (P = .248), or body mass index (P = .257).

Conclusion

We found high reproducibility of posterior displacement measurements on Telos stress radiography at a KFA of 85° to 92° in noninjured knees.

Diagnostic Value of Stress Radiography and Arthrometer Measurement for Anterior Instability in Anterior Cruciate Ligament Injured Knees at Different Knee Flexion Position

PURPOSE

To evaluate diagnostic value of stress radiography and arthrometer measurements for anterior instability at different knee flexion angle positions.

METHODS

Forty-three patients with complete anterior cruciate ligament (ACL) rupture (group 1) and 37 normal subjects (group 2) were enrolled prospectively. Arthrometer (KT-1000) measurements and stress radiography by Telos were used to evaluate side-to-side differences. Results were recorded according to the knee position (30°, 45°, 60°, and 90°). Areas under the receiver operating characteristic curves (AUCs) were used to evaluate the diagnostic accuracy of each evaluation method. The calculated cutoff values at 30° position were used to evaluate the sensitivity and specificity of combined evaluation with stress radiography and arthrometer measurements.

RESULTS

The side-to-side differences on stress radiography and arthrometer measurements were significantly different between groups (P < .05), except for the values at the 90° position in arthrometer measurements (P = .844). The amount of anterior translation decreased in both arthrometer measurements and stress radiography between 30° and 45° positions (P < .000); however, no further decrease was observed beyond 45°. The AUC of stress radiography at the 30° position was significantly higher than other values (AUC = 0.955; P = .000). Moreover, the clinical cutoff value of 3 mm showed 86.0% sensitivity and 89.2% specificity in stress radiography at 30°, which were higher than those in arthrometer measurements. Combined use of stress radiography and arthrometer measurements at the 30° position showed 100% sensitivity and 59.5% specificity as a screening test.

CONCLUSIONS

Evaluation at the 30° knee position was significantly superior to that at other positions for both stress radiography and arthrometer measurements, whereas the 90° knee flexion position was not meaningful for any measurements. Evaluation needs to be performed with a 3-mm cutoff value for stress radiography at the 30° knee position; however, combined use of stress radiography and arthrometer measurements at the 30° knee flexion can have a higher diagnostic value.

LEVEL OF EVIDENCE

Level I, diagnostic study of established criteria.

Rater agreement reliability of the dial test in the ACL-deficient knee

Background

Posterolateral rotatory instability (PLRI) of the knee can easily be missed, because attention is paid to injury of the cruciate ligaments. If left untreated this clinical instability may persist after reconstruction of the cruciate ligaments and may put the graft at risk of failure. Even though the dial test is widely used to diagnose PLRI, no validity and reliability studies of the manual dial test are yet performed in patients. This study focuses on the reliability of the manual dial test by determining the rater agreement.

Methods

Two independent examiners performed the dial test in knees of 52 patients after knee distorsion with a suspicion on ACL rupture. The dial test was performed in prone position in 30°, 60° and 90° of flexion of the knees. ≥10° side-to-side difference was considered a positive dial test. For quantification of the amount of rotation in degrees, a measuring device was used with a standardized 6 Nm force, using a digital torque adapter on a booth. The intra-rater, inter-rater and rater-device agreement were determined by calculating kappa (κ) for the dial test.

Results

A positive dial test was found in 21.2% and 18.0% of the patients as assessed by a blinded examiner and orthopaedic surgeon respectively. Fair inter-rater agreement was found in 30° of flexion, κ_F = 0.29 (95% CI: 0.01 to 0.56), p = 0.044 and 90° of flexion, κ_F = 0.38 (95% CI: 0.10 to 0.66), p = 0.007. Almost perfect rater-device agreement was found in 30° of flexion, κ_C = 0.84 (95% CI: 0.52 to 1.15), p < 0.001. Moderate rater-device agreement was found in 30° and 90° combined, κ_C = 0.50 (95% CI: 0.13 to 0.86), p = 0.008. No significant intra-rater agreement was found.

Conclusions

Rater agreement reliability of the manual dial test is questionable. It has a fair inter-rater agreement in 30° and 90° of flexion.

Editorial Commentary: A Positive "Half Dial Test" Is Seen in Anterior Cruciate Ligament Injury, so Get Out Your Goniometer

Isolated anterior cruciate ligament (ACL)-deficient knees have roughly 7° of increased external rotation at both 30° and 90° of flexion compared with both the contralateral knee and the ACL reconstructed knee. This positive "Half Dial test" may be a new approach to confirming ACL injury but requires confirmation that the posterolateral corner itself is not injured. In the ACL-deficient knee, it is suggested that a greater cutoff (>15°) for the true Dial test be used to confirm posterolateral corner injuries. Goniometer measurements are reproducible and necessary for confirmation.