Shoulder Dysfunction in Parkinson's Disease: Implications of Motor Subtypes, Disease Severity, and Spinopelvic Alignment.

Objective: To investigate shoulder function and muscle alterations in patients with Parkinson's disease (PD) and determine their associations with spinopelvic parameters and clinical status.

Methods: This prospective cohort study included 62 PD patients, divided into postural instability and gait difficulty (PIGD) (n=30) and non-PIGD (n=32) groups, as well as 35 controls. The American Shoulder and Elbow Surgeons (ASES) score, shoulder range of motion (ROM), and shoulder muscle stiffness were assessed for each group. Clinical demographics, PD severity, and shoulder-related parameters were extracted and analyzed.

Results: Compared with the control group, the PIGD group had significantly lower total and subscored ASESs (all p<0.05). Compared with the controls, both the PIGD and non-PIGD groups demonstrated reduced abduction and forward flexion (all p<0.05). Compared with the non-PIGD group and the control group, the PIGD group also presented decreased external rotation (all p<0.05). Infraspinatus muscle stiffness was greater in the PIGD group than in the control group (p=0.012). Correlation analysis revealed that shoulder condition was significantly associated with PD severity and the PIGD score, whereas muscle stiffness was linked to spinopelvic alignment and the PIGD score. Various clinical factors, including PD severity, the PIGD score, the tremor score, and spinopelvic alignment, were significantly correlated with shoulder ROM.

Conclusion: PD patients experience shoulder dysfunction in various ways, including decreased ASES scores, limited ROM, and increased shoulder muscle stiffness. Our study highlighted the impact of PD motor subtype, disease severity, and spinopelvic alignment on the development of shoulder dysfunction, offering deeper insights into the pathophysiological basis of shoulder disorders in PD.