Objective: This prospective investigation is designed to determine the prognostic factors associated with the response to conservative therapy of subacromial impingement syndrome.
Materials and methods: We treated 102 patients with subacromial impingement syndrome, diagnosed by physical examination and a subacromial lidocaine injection test, with a standardized conservative protocol. We followed the patients for a period of 12 months. Outcome was evaluated with Constant score and effects of 8 variables: Age, sex, pretreatment symptom duration, dominant shoulder, initial Constant score, active range of motion, acromion morphology, and acromial spur on patient outcomes were evaluated with univariate and multivariate analyses.
Results: Among 89 patients (44 men; mean age, 56.4 years) who finished the study, the mean difference between initial and final scores was 15.9 (95% confidence interval [CI]: 13.9-17.8). Three variables, the initial Constant score (b = .52, 95% CI: .28-.76), the duration of disease before treatment (b = -4.4, 95% CI: from -7.2 to -1.6), and acromial morphology (b = -5.3, 95% CI: from -9.8 to -.8) were found to be independent predictors of outcome (model R2 = .68).
Conclusion: Patients with more severe disease, a long duration of symptoms, and type II or III acromion may require more invasive therapeutic options as the first intervention.