Diagnosis of shoulder instability by examination under anesthesia.

A systematic method of examining the shoulder in anesthetized patients was developed. Humeral translocation on the glenoid was assessed in five directions and in three positions of arm rotation for four of these directions. Fifty-five patients thought to have shoulder instability were evaluated by history taking, physical examination, standard and special roentgenograms, examination under anesthesia, and either shoulder arthroscopy or operation. The findings at examination under anesthesia were compared with the pathologic conditions identified at arthroscopy or operation. Twenty-five shoulders had pathologic evidence of continuing instability: Bankart lesions in 19 and clearly excessive capsular laxity in six. All 25 had abnormal results on examination under anesthesia (no false-negative results). Thirty shoulders had no demonstrable pathologic condition. The results of examination under anesthesia were normal for 28 shoulders and abnormal for two (two false-positive results). The sensitivity of examination under anesthesia in these patients was 100%. The specificity and predictive value were 93%. Examination under anesthesia has proven to be reasonably precise in assessing shoulder stability. If the results of the examination are normal, more complex and invasive diagnostic testing may not be necessary.