UC San Diego

Background

Posterolateral rotatory instability (PLRI) results from lateral ulnar collateral ligament (LCL) deficiency. The lateral pivot shift test is used to diagnose PLRI but can be difficult to perform and is poorly tolerated. We present a new maneuver, the Posterior Radiocapitellar Subluxation Test (PRST), that we believe is easier to perform. The purpose of this study was to compare the efficacy and reproducibility of the PRST with the lateral pivot shift test.

Methods

We obtained 10 cadaveric upper extremity specimens, performed a Kocher approach on each, released the LCL origin in 5, then closed. The specimens were randomized, and 3 attending orthopedic surgeons and 1 resident blindly performed the PRST then the lateral pivot shift test after re-randomization and assessed presence or absence of PLRI. This process was repeated the following day. The data for each test were analyzed for sensitivity, specificity, and accuracy.

Results

For the blinded testing when comparing PRST with the pivot shift test, overall accuracy was 77.5%, compared with 67.5% (P = .03), sensitivity was 75.0%, compared with 50.0% (P = .003), and specificity was 80.0%, compared with 85.0% (P = .55). Conclusions: The PRST appears to be at least as accurate as the lateral pivot shift test, with comparable intraobserver and interobserver reliability.