Glenohumeral Joint Volume Measurement in Patients with Shoulder Instability: A 3D Volumetric Magnetic Resonance Arthrographic Study

<i>Background and Objectives:</i> This study aimed to compare capsular volume in patients with shoulder instability to that in control subjects without instability using magnetic resonance (MR) arthrography. The objective was to develop a reliable screening method with which to assess shoulder volume. <i>Materials and Methods:</i> In 21 patients with atraumatic shoulder instability and 21 controls, thin-slice 3D volumetric MR arthrography sequences were obtained. MR arthrography images were uploaded to 3D reconstruction, and 3D images were generated. From the 3D reconstructed images, volumetric measurements of rotator interval (RI), anterior and posterior capsular (AC, PC) recesses, biceps tendon sheath (BS), axillary recess (AR), and total glenohumeral joint (TGJ) were performed. Individuals with any extra-articular contrast leakage were also recorded. <i>Results:</i> A retrospective study analyzed a patient group of 21 individuals with shoulder instability (mean age 29.52 ± 12.83 years) and a control group of 21 individuals without instability (mean age 35.71 ± 12.77 years). No statistically significant differences were identified between the groups with regard to age, gender, or side distribution. The mean total joint volume was significantly higher in the instability group (29.85 ± 6.40 cm³) compared to the control group (23.15 ± 3.48 cm³, <i>p</i> = 0.0001). Additionally, the mean volumes of the RI, AC, PC, BS, and AR were all significantly greater in the patient group compared to the control group. <i>Conclusions:</i> 3D volumetric MR arthrographic measurements of the shoulder joint capacity can provide valuable insights for clinical follow-up and guide surgical treatment decisions in cases of atraumatic shoulder instability.