The efficacy of conservative management of micro-traumatic posterior shoulder instability

Microtraumatic posterior shoulder instability (PSI) is characterized by symptomatic posterior translation of the glenohumeral joint. A common etiology is a gradual overload of glenohumeral joint structures. The recommend initial treatment for microtraumatic PSI is rehabilitation; however, the evidence to support this recommendation is limited. The aim of this study is to investigate the patient- reported outcome measures and return to sport success of participants with microtraumatic PSI who participate in a posterior instability rehabilitation program.

In the single-group study design, 24 shoulders in 22 sporting participants (17 male, 5 females; mean age, 21.1 years, standard deviation 10.1 years) diagnosed with microtraumatic PSI undertook the Watson Posterior Instability Program (WIP-p) over 24 weeks. Outcome measures included the Melbourne Instability Shoulder Score and Western Ontario Shoulder Instability Index at baseline, 6, 12, and 24 weeks. Failure of conservative management and time to return to sport was measured. Treatment effects were determined using linear mixed models, with 95% confidence intervals. Significance was set at 0.05.

After 24 weeks of the WIP-p, participants had significant improvements at 12 (effect size or standardized mean difference (SMD): 1.1, P < .001) and 24 weeks (SMD: 1.8, P < .001) on the Western Ontario Shoulder Instability Index and significant improvements at 6 (SMD; 0.74, P = .036), 12 (SMD: 0.41, P = .007) and 24 weeks (SMD: 1.7, P < .001) on the Melbourne Instability Shoulder Score. For return to sport, 20 of the 22 (90.1%) participants returned to full activity at the 24-week time point, while two went on to have reconstructive surgery.

The WIP-p resulted in a high level of return to sport and significantly improved functional outcomes in patients with microtraumatic PSI. A small proportion of sporting participations with microtraumatic PSI may fail conservative rehabilitation and require surgical consideration.