Interclinician and intraclinician variability in the mechanics of the pivot shift test for posterolateral rotatory instability (PLRI) of the elbow

Abstract

Posterolateral rotatory instability (PLRI) of the elbow results from injury to the lateral collateral ligament complex from trauma or iatrogenic injury. The lateral pivot-shift test (PST) is standard for diagnosing PLRI, but its subjectivity affects diagnosis and makes it difficult to train young surgeons. A well-controlled investigation has not been done to quantify interclinician and intraclinician variability in PST mechanics in the intact and unstable elbow. The authors predict that there exist differences in PST mechanics between clinicians. Five unpaired elbow specimens underwent PST intact and after sequential sectioning of lateral stabilizing ligaments. Multiple PST trials were performed on each specimen by 3 clinicians (1 expert, 2 in-training) while 3-dimensional motion and loads were recorded. Intraclinician and interclinician variability were analyzed. Mean supination torque, valgus torque, and axial force were 3.6 ± 1.9 Nm, 5.6 ± 3.1 Nm, and -8.3 ± 15.7 N, respectively. Mean radial head displacement was 13.7 ± 4.6 mm. There were no significant differences in these measures after sequential ligament sectioning. One surgeon (in-training 2) applied significantly greater axial compressive forces across the elbow joint (5-9 N difference). Variability of axial force (380% ± 473%) was greater than that of supination torque (20% ± 11%), valgus torque (14% ± 4%), and radial head displacement (8% ± 6%; P < .05 for analysis of variance). The clinicians performed the PST consistently and with comparable loads, with the exception of axial compressive force across the radiohumeral joint, which varied across clinicians by 1 to 2 pounds (5-9 N). This study suggests that the PST is a mechanically reproducible clinical examination, despite differing levels of training in performing the maneuver. With the exception of axial force, PST mechanics are highly repeatable for a given surgeon applying the test on a single specimen.