Paper #20 Lag signs in acute complete tears of the supraspinatus tendon. Does a subacromial lidocaine injection help in the clinical diagnosis? A prospective study

Abstract

Compared to other tendon injuries, tears of the rotator cuff tendons may be difficult to diagnose in the acute stage. This may delay treatment and influence the prognosis of surgical repair. Most previous studies on this diagnostic dilemma are retrospective and deal mainly with chronic cuff tears. Hertel et al. showed that simple tests examining the inability to maintain certain positions of the arm, the lag signs, were sensitive for complete tears of the rotator cuff tendons. We hypothesized, that complete tears were indifferent to subacromial lidocaine injection due to loss of tendon integrity, and that this could be a valuable additional diagnostic test in the Emergency Ward. The study was designed to evaluate the value of clinical examination with and without subacromial lidocaine within the first weeks after an acute injury to the shoulder. From February 1998 till March 2000, a total of 104 patients with an acute injury to a previous healthy shoulder were included in a prospective diagnostic project comparing clinical findings with ultrasound. Only persons who were unable to active abduct the shoulder above 90 degrees, and whose radiographs showed no signs of fracture or joint dislocation were included. Of these, 29 (9 female, 20 male, median age 55) had a complete tear of the supraspinatus tendon diagnosed by arthroscopy. The patients were evaluated at median 12 (3–49) days after the injury with the classic drop arm test (DAT) and Hertel’s external rotation lag sign (ERls) specific for supra- and infraspinatus tears with and without subacromial lidocaine injection as well as with ultrasound. The control group consisted of the remaining 75 patients where the combined clinical and ultrasound examination revealed an intact cuff (=IC). The sensitivity and specificity was 41% and 80% for the DAT and 45% and 77% for the ERls. After subacromial lidocaine injection the similar figures for the DAT were 19% and 95%, and 19% and 92% for the ERls. The active abduction at median 12 (3–49) days after the injury improved from median 80 (0–180) degrees to median 110 (20–180) degrees after subacromial lidocaine injection. The lag signs specific for supraspinatus tears have a low sensitivity and an acceptable specificity in acute cases. After effective pain relief, the sensitivity for both tests was reduced to 19%, whereas the specificity increased. Pain seems to be the limiting factor in maintaining the arm position rather than loss of tendon integrity in an acute rotator cuff tear. Acute complete tears of the supraspinatus tendon cannot be detected by the clinical tests alone.