Original articleEvaluation of the lag sign tests for external rotator function of the shoulder☆
Section snippets
Specimen preparation and mounting
Seven radiographically normal human shoulders (mean patient weight, 84 ± 15 kg; mean age, 60 ± 21 years, with three patients of unknown age) were harvested and frozen before testing. The specimens were thawed at room temperature for 12 hours before dissection of all muscles except for the rotator cuff and deltoid. The muscle bellies of the rotator cuff were bluntly dissected away from the scapula, and particular care was taken to preserve the integrity of the joint capsule and ligaments as well
Results
The results of the lag sign simulations are tabulated according to the number of positive tests versus the number of specimens tested at each elevation angle and combination of SSP and ISP-TM force tested (Table II). One of the seven specimens tested was removed from the series because it exhibited unusual laxity and an extreme external rotation of 104° at 90° elevation, and thus almost no SSP and ISP-TM force was required to hold the test position. The SSP tendon insertion of another specimen
Discussion
The results of this study suggest that it is difficult to distinguish between deficiencies of the SSP and ISP-TM muscles by use of the lag sign tests based on biomechanical considerations alone. Whereas complete loss of ISP-TM force would result in 100% sensitivity at all elevations tested (Table I, 100% SSP force), complete loss of SSP force would be more difficult to detect, especially at lower elevations. Although increasing with elevation, sensitivity for the isolated SSP rupture was still
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This study was funded by the German Research Foundation (DFG).