Advances in the role of ultrasound in the diagnosis of adhesive capsulitis (frozen shoulder)

Abstract

Adhesive capsulitis (AC), also called frozen shoulder (FS), is a debilitating condition characterised by a gradual onset of shoulder pain followed by a loss of range of motion (ROM). Diagnosis is currently based on clinical assessment, which can be challenging due to similarities in symptoms with other shoulder problems. To assist in the diagnosis, ultrasound studies have shown a thickened inferior glenohumeral capsule (IGHC) as one of the characteristics of patients with AC. However, a systematic review conducted for this thesis demonstrated inconsistencies in the methods and results of prior studies. The accuracy of this diagnostic marker also had not been established, without which its clinical utility was limited. The aim of this thesis was to explore the role of this ultrasound marker in the diagnosis of AC by analysing the IGHC thicknesses in various shoulder pathologies including AC. This was achieved through three phases of an experimental study. An analysis of the asymptomatic shoulders in the first phase confirmed that males have thicker IGHC, and showed that the normal IGHC thickness reduces similarly in both sexes as the shoulder is abducted. To overcome variability in the IGHC thickness, IGHC ratios, obtained by side to side comparison between symptomatic and asymptomatic sides, were investigated in the second phase. The IGHC ratios were found to be significantly larger in the FS group compared to the group with other shoulder pathologies when measured at 90° shoulder abduction. The ratio ≥ 1.8 was 92% specific to the FS group. To elaborate on the clinical utility of this marker, participants whose IGHC ratios did not correlate with their clinical status of FS at the first visit, and those who had not improved in their clinical impairment at their first follow-up visit were followed at six,12 and 24 months. With no clear evidence found to explain the discrepancies, limitations of this study and directions for future studies are provided.