Computed tomography (CT) arthrography of the shoulder is an imaging modality of great diagnostic accuracy with regard to glenohumeral instability and in particular labral lesions. Interpretation of the scans is made difficult by the frequent occurrence of normal anatomic variants and the complexity of injuries to the bone and soft tissues. We selected a continuous sample of 50 CT arthrograms of the shoulder and they were reported by two consultant musculoskeletal radiologists. The results were collated and analysed for the level of agreement. Hill¿Sachs showed Kappa (K) statistic to be 0.37 (fair agreement), soft tissue Bankart 0.32 (fair agreement), bony Bankart 0.61 (substantial agreement), anterior capsular laxity 0.41 (moderate agreement) and glenohumeral osteoarthritis 0.20 (slight agreement). All the results were significant with a p value of <0.05. Nine (18%) of the 50 scans were in complete agreement. The results demonstrate that there can be considerable interobserver variation (IOV) in the reports of a CT arthrogram of a shoulder. They highlight the potential difficulties in reporting such images and suggests ways in which the report could be more focussed to provide a clinically reliable report and one which matches the surgical findings accurately.

This paper presents an intraoperative MRI-guided, patient-mounted robotic system for shoulder arthrography procedures in pediatric patients. The robot is designed to be compact and lightweight and is constructed with nonmagnetic materials for MRI safety. Our goal is to transform the current two-step arthrography procedure (CT/x-ray-guided needle insertion followed by diagnostic MRI) into a streamlined single-step ionizing radiation-free procedure under MRI guidance. The MR-conditional robot was evaluated in a Thiel embalmed cadaver study and healthy volunteer studies. The robot was attached to the shoulder using straps and ten locations in the shoulder joint space were selected as targets. For the first target, contrast agent (saline) was injected to complete the clinical workflow. After each targeting attempt, a confirmation scan was acquired to analyze the needle placement accuracy. During the volunteer studies, a more comfortable and ergonomic shoulder brace was used, and the complete clinical workflow was followed to measure the total procedure time. In the cadaver study, the needle was successfully placed in the shoulder joint space in all the targeting attempts with translational and rotational accuracy of 2.07 ± 1.22mm and 1.46 ± 1.06 degrees, respectively. The total time for the entire procedure was 94 min and the average time for each targeting attempt was 20 min in the cadaver study, while the average time for the entire workflow for the volunteer studies was 36 min. No image quality degradation due to the presence of the robot was detected. This Thiel-embalmed cadaver study along with the clinical workflow studies on human volunteers demonstrated the feasibility of using an MR-conditional, patient-mounted robotic system for MRI-guided shoulder arthrography procedure. Future work will be focused on moving the technology to clinical practice.