No difference in outcomes for posterior shoulder instability surgery in patients with a normal vs. pathological radiologist reported magnetic resonance arthrogram study.

BACKGROUND: Despite improvement in diagnostic imaging techniques, there remain patients with clinical posterior shoulder instability (PSI) with so called normal or nonpathologic findings on magnetic resonance arthrogram (MRA). This diagnostic dilemma creates challenges for clinicians and patients who fail conservative treatment when determining treatment options due to the incongruent findings on physical exam and MRA. We hypothesized that patients undergoing capsulolabral repair with a clinical exam consistent with PSI but normal radiologist reported MRA findings would experience similar clinical improvement compared to patients with PSI and pathological radiologist reported MRA findings.

METHODS: A database of prospectively enrolled patients was reviewed to identify patients who underwent surgery for PSI between 2016 and 2022. Inclusion criteria were a positive posterior load and shift test on examination under anesthesia, a preoperative MRA with an accessible radiologist report, and minimum 2-year follow-up. Patients with anterior or multidirectional instability on examination under anesthesia, rotator cuff lesions, a Beighton score greater than 6, glenoid bone loss or fracture, or history of prior shoulder surgery on the affected side were excluded. The interpreting radiologist's MRA impression of the posterior labrum and capsule was used to classify patients into the normal MRA (N = 16) or pathologic MRA (N = 18) cohort. Patient-reported outcome measures compared between groups included visual analog scale (VAS) pain, Single Assessment Numeric Evaluation (SANE), and Western Ontario Shoulder Instability Index.

RESULTS: Thirty-four patients with a mean age of 34.7 and body mass index of 27.7 were included in the study. Patient sex was the only significantly different demographic variable between normal MRA and pathological MRA groups (75.0% female vs. 16.7% female, P < .001). At the final follow-up (mean: 41.7 vs. 36.1; P = .361), both the normal MRA and pathological MRA groups demonstrated significant improvements in SANE (mean: 29.8, P < .001; mean: 41.6, P < .001) and reductions in VAS Pain (mean: -2.1, P = .005; mean: -3.2, P < .001). When compared between groups, there were no statistically significant differences in mean VAS Pain, SANE, or Western Ontario Shoulder Instability Index. Three patients (18.8%) in the normal MRA group required an arthroscopic capsular release for adhesive capsulitis vs. 1 patient (5.6%) in the pathological MRA group (P = .233).

CONCLUSION: A careful clinical exam is the most important factor when determining indication for PSI surgery. Regardless of the radiologist interpretation, patients with symptomatic PSI can benefit from arthroscopic stabilization surgery.