Body-Mounted Robotic System for MRI-Guided Shoulder Arthrography: Cadaver and Clinical Workflow Studies

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 ± 1.22 mm 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.

Shoulder Arthrography

Chapter 98 describes indications, technique, and imaging findings of shoulder arthrography. Shoulder arthrography is commonly performed in routine clinical practice for MR arthrography (MRA), typically in younger patients. The main indications include evaluation of shoulder instability and postoperative rotator cuff. Other indications include fluoroscopic guidance for therapeutic injections or therapy for adhesive capsulitis. CT arthrography (CTA) may also be performed for evaluation of total shoulder arthroplasty (TSA) loosening and conversion from anatomic to reverse TSA. Contrast should be easy to inject and disperse throughout the joint. Abnormal communication between the glenohumeral joint and subacromial-subdeltoid and subcoracoid bursae is diagnostic of a full-thickness rotator cuff tear unless the contrast is accidentally injected into the bursa. However, in the setting of prior rotator cuff repair, contrast may extend into the bursa even in the absence of re-tear because the cuff is not watertight. Contrast extension into the glenoid labral substance is diagnostic of labral tear.