Dynamic MR imaging and stress testing in glenohumeral instability: Comparison with normal shoulders and clinical/surgical findings

Our objectives were to test the hypotheses that: 1) during shoulder motion, glenohumeral alignment differs between asymptomatic shoulders and those wi th symptomatic instability; 2) during magnetic resonance (MR)-monitored phy sical exam or stress testing, glenohumeral alignment differs between asympt omatic shoulders and those with instability; and 3) glenohumeral translatio n during MR stress testing correlates with findings of shoulder instability by clinical exam and exam under anesthesia (EUA). Using an open-configurat ion 0.5 T MR imaging (MRI) system, we studied symptomatic shoulders in I I subjects and compared them to their contralateral asymptomatic shoulders. E ach shoulder was studied during abduction/adduction and internal/external r otation to determine the humeral head position on the glenoid. An examiner also performed the MR stress test on each shoulder by applying manual force on the humeral head during imaging. Ali shoulders were assigned an Instabi lity grade from the MR stress test, and this grade was correlated with: 1) clinical exam grade assigned during preoperative assessment by an orthopedi c surgeon and 2) intraoperative instability grade by EUA immediately preced ing arthroscopy. With dynamic abduction and internal/external rotation, the humeral head remained centered on the glenoid in 9 of 11 shoulders, but in two subjects there were dramatic demonstrations of subluxation. With stres s testing, a trend toward more joint laxity was demonstrated in symptomatic than In asymptomatic joints (P = 0.11). MR grading of instability correlat ed directly with clinical grading in six cases and underestimated the degre e of instability relative to clinical exam in the other cases. MR instabili ty grading systematically underestimated instability compared with EUA in 7 of the 10 cases that underwent surgical repair. We concluded that dynamic MR evaluation of glenohumeral alignment did not demonstrate abnormalities i n symptomatic shoulders in 8 of 10 patients, whereas 2 patients showed dram atic findings of subluxation. Manual stress testing during dynamic MR exami nation showed a strong correlation with clinical instability grading. Dynam ic shoulder MR examination during stress testing could, with further valida tion, become a useful adjunct to shoulder instability evaluations. (C) 2001 Wiley-Liss, Inc.