Intra-articular Pressure Profiles of Painful Stiff Shoulders Compared With Those of Other Conditions

ObjectiveTo test two questions raised by a previous study: whether high and steeply rising intra-articular (IA) pressure achieved by controlled fluid infusion would be specific to the painful stiff shoulder (PSS) and whether rupture occurs immediately after the appearance of the third phase so that it could be considered as a preruptural sign.DesignCase series.SettingUniversity Outpatient Clinic of Physical Medicine and Rehabilitation.ParticipantsFourteen PSS patients who had limited range of motion of the shoulder in at least 2 directions for more than a month were participants, and 6 shoulders of 5 people with other conditions including 2 healthy shoulders served as controls.Intervention and Main Outcome MeasuresReal-time pressure monitoring was done with fluid infusion in a constant-volume rate. For PSS patients, fluid was infused until rupture occurred. More than 25 mL of fluid was instilled in the shoulders of the control group. The pressure-volume (P-V) profiles, number of phases, maximal volume (Vmax) and pressure (Pv_max) at Vmax, stiffness of the capsule (Kph2), and the fluid volume (Vph3) infused from the appearance of the triphasic curve to the rupture were evaluated.ResultsAmong the 14 PSS patients, 12 demonstrated steeply increasing pressure (8 triphasic, 4 biphasic), but 2 showed flat and low-pressure profiles. In contrast, the entire control group revealed flat pressure profiles. The PSS subjects showed far higher Pv_max at lower Vmax than the control subjects. The Kph2 was significantly higher in the PSS group. The Vph3 was 5.03 ± 3.18 mL ranging from 2.33 to 10.99 mL.ConclusionsThe steeply rising, high IA pressure can be considered as a predominant characteristic of the PSS compared with other conditions that showed flat, low-pressure profiles, suggesting the P-V profiles might be used in evaluation of the capsular tightness of various shoulder problems. The triphasic curve appears to be a preruptural sign; however, there are several practical limitations to terminating hydraulic distension before rupture occurs.