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AAOS 2022 - Scapulohumeral Rhythm of Shoulders with adhesive Capsulitis

April 6, 2022
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X-Ray Technology

P0762 — 2022 Using Dynamic Digital Radiography to Measure Variations in Scapulohumeral Rhythm of Shoulders with adhesive Capsulitis.

Author(s): Angel Xiong Xiao, MSc, BS, Atlanta, GA; Beau McGinley, MBA, BA, Atlanta, GA; Michael Brandon Gottschalk, MD, FAAOS, Atlanta, GA; Eric R Wagner, MD, FAAOS, Atlanta, GA.

INTRODUCTION:

Scapulohumeral rhythm (SHR), defined as the ratio of glenohumeral (GH) and scapulothoracic (ST) motion during arm elevation, is an important but not well-defined parameter in assessing shoulder pathology. Particularly in adhesive capsulitis, where patients have known diminished GH motion, a quantitative assessment of SHR has profound implications. Currently, adhesive capsulitis is a clinical diagnosis, and, with no radiographic or quantitative standard of diagnosis, SHR has the potential to become the reference standard. Unfortunately, it has been previously difficult to measure SHR in a clinical setting without purchasing specialized and expensive equipment in a 3-dimensional motion analysis laboratory. The purpose of this study was to measure the SHR of patients with adhesive capsulitis compared to normal controls using a novel safe and cost-effective imaging technique known as Dynamic Digital Radiography (DDR). METHODS: Shoulders were prospectively analyzed using DDR which obtains a series of pulsed radiographs at up to 15 Hz of the joint in motion. The dynamic images were taken under the supervision of one of three radiology technicians who coached patients on the timing and cadence of the requisite shoulder motions. Scapulothoracic motion and glenohumeral motion were quantified based on the DDR images(figure 1). Measurements were taken in humeral abduction at 0-30°, 30-60°, 60-90°, and full abduction using the Grashey view. SHR at different points were calculated by dividing the humeral arc of motion by the scapular arc of motion in each of those motion ranges. Pairwise tests were performed on the obtained data to compare differences between groups at an α level of 0.05.

RESULTS:

Forty-eight patients were analyzed, including 16 patients with adhesive capsulitis compared with 32 normal controls, matching for age and BMI (Table 1). The final angle calculations are displayed in table 2. Patients with adhesive capsulitis had a significantly lower SHR of1.55 ± 0.37 compared to the control group's SHR of 3.47 ± 0.80 (p<0.001). When analyzed across 30-degree intervals of humeral abduction(figure 2), there was a statistically significant lower SHR found at 0-30° (1.67 vs. 3.97, p<0.001), 30-60° (1.64 vs. 3.17, p<0.001), and 60-90°(1.45 vs. 3.43, p<0.001) of humeral abduction in adhesive capsulitis patients compared to controls. No significant difference was found when comparing the SHR at 0-30°, 30-60°, 60-90° of humeral abduction in adhesive capsulitis patients.

DISCUSSION AND CONCLUSION:

A dynamic measurement of SHR demonstrates that patients with adhesive capsulitis have a significantly increased contribution of scapulothoracic joint motion in order to compensate for a loss of glenohumeral motion, resulting in a more than 2x lower SHR compared to normal controls. Furthermore, the SHR differences vary throughout the arc of abduction but remain drastically different. Dynamic measurement of SHR represents a novel method for diagnosing adhesive capsulitis, a pathology that currently remains a clinical diagnosis. Further study and validation of the dynamic assessment of SHR has the potential to contribute to the diagnostic algorithm for adhesive capsulitis and other shoulder pathologies.