Lag Sign of the Shoulder

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Purpose

The external rotation lag sign (ERLS) was originally described by Hertel et al in 1996¹. The purpose of this clinical diagnostic test is to assess the presence of a full-thickness rotator cuff tear. In particular the ERLS is designed to test the integrity of the supraspinatus and infraspinatus tendons.

Technique

The ERLS is performed with the patient seated. The elbow is passively flexed to 90° and the shoulder elevated 20° (in the plane of the scapula) and held 5° off maximal external rotation (to avoid elastic recoil of the joint capsule and the scapulothoracic joint). The patient is then asked to maintain the position actively while the examiner releases the wrist while maintaining support through the elbow. An inability to maintain the position (lag) would suggest a full-thickness tear of the rotator cuff². The magnitude of the lag is recorded in degrees to the nearest 5°. The contralateral side serves as a control, especially to evaluate small lags that could be related to hyperlaxity or to overzealous external rotation by the examiner³.

Testing and interpretation can be complicated by pathologic changes in passive range of motion (PROM) at the glenohumeral joint. When PROM is reduced because of capsular contracture or increased because of a subscapularis rupture, for instance, false-negative and false-positive results, respectively, can be expected¹.

File:Lag.jpg

Evidence

Study	Subjects (n)	Inclusion Criteria	Exclusion Criteria	Reference Standard	Sens.	Spec.	+LR	-LR
Hertel et al1	100	Patients who subsequently underwent open or arthroscopic surgery were included.	Patients with any impairment of PROM at glenohumeral joint were excluded.	Arthroscopy or open surgery	0.91 (ss+is)	1.0 (ss+is)	infinite	0.09
Miller et al2	37	Patients with shoulder pain (pain in the C5-6 dermatome), full passive movement of the involved shoulder, and age over 18 years.	Patients with previous surgery to the symptomatic upper limb and any symptoms of neurologic origin.	Diagnostic ultrasound	.46 (ss+is)	.94 (ss+is)	7.2	0.55
Castoldi et al3	401	Retrospective review of 401 consecutive patient cases with painful shoulder conditions who subsequently underwent open or arthroscopic surgery.	Patients with acute traumatic conditions, acute postoperative conditions, fractures, frozen shoulder with great deficit of range of motion and neurologic disorders.	Arthroscopy or open surgery	.56 (ss only)	.98 (ss only)	28.0	0.45

_{Abbreviations for full-thickness tear locations: ss=supraspinatus, is=infraspinatus, ss+is=supraspinatus and infraspinatus}

The ERLS has been shown to be a highly specific clinical test for ruling in the diagnosis of a full-thickness tear of the supraspinatus and/or infraspinatus tendon(s) ^1-3. Evidenced by the less than optimal negative likelihood ratios and sensitivity values, a negative test result is less useful at ruling out the same diagnosis^2-3.

References

1. Hertel R, Ballmer FT, Lambert SM, Gerber C. Lag signs in the diagnosis of rotator cuff rupture. J Shoulder Elbow Surg 1996;5:307-13.

2. Miller CA, Forrester GA, Lewis JS. The validity of the lag signs in diagnosing full-thickness tears of the rotator cuff: a preliminary investigation. Arch Phys Med Rehabil 2008;89:1162-8.

3. Hertel R, Ballmer FT, Lambert SM, Gerber C. Lag signs in the diagnosis of rotator cuff rupture J Shoulder Elbow Surg 1996;5:307-13.