Factors influencing treatment outcome of physical therapy in frozen shoulder patients: a systematic review

Purpose: To summarise factors that might influence treatment outcomes of physical therapy in patients with frozen shoulder. Methods: A systematic literature study was performed by searching electronic bibliographies PubMed and Web of Science. Original full text research articles about human adults with frozen shoulder, assessing influencing factors of treatment outcome of physical therapy were included in the review. Results: Sixteen studies were included in this systematic review. Methodological quality of the included studies was low to moderate and most studies had level of evidence B. Duration of symptoms and affected shoulder were found not to influence range of motion. Preliminary evidence was found for shoulder kinematics, pain, functionality, therapy compliance, and interactive rehabilitation as possible influencing factors. Conflicting evidence was found for co-morbidities, gender, and age. Most frequent used interventions were exercises, stretching, and mobilisation. Conclusions: Level of conclusion 2 was found for duration of symptoms and affected shoulder for not influencing range of motion. Some limitations are that only few studies specifically investigated influencing factors and there is a difference in research and physical therapy protocols and outcome measures used. Therefore, more high-quality research with standardised protocols is needed to confirm preliminary evidence and elucidate conflicting results.