Imaging Instability in the Athlete

Creating a Three-Dimensional Reconstruction of the Glenohumeral Joint From Magnetic Resonance Imaging to Assist in Surgical Decision-Making

Understanding the anatomical structure of a patient's shoulder joint is essential in surgical decision-making, especially regarding glenohumeral bone loss. The use of various imaging techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT), bring certain advantages and disadvantages in assessing joint structure. Before a surgical procedure, bone loss can be observed and measured using these imaging techniques in both 2-dimensional and 3-dimensional (3D) views. The ability to visualize the shoulder joint in a 3D manner, as commonly done with CT scans, is helpful in assessing bone loss; however, CT involves exposure to radiation, additional time, and greater costs. The process of obtaining a 3D view of the shoulder joint from an MRI, although less common, can be completed effectively to assess bone loss while also solving some issues surrounding CT scans. By loading MRI datasets into an image-reformation program, such as 3D Slicer, the anatomical structures can be segmented to create realistic 3D models of the shoulder joint. Surgical direction can be determined after bone loss measurements and structural assessment of these models, without the need for CT scans. This technique can also be applied to other skeletal joints, in addition to the shoulder.

What can the Radiologist do to Help the Surgeon Manage Shoulder Instability?

Imaging of the shoulder forms an important adjunct in clinical decision making in patients with shoulder instability. The typical lesions related with classic anterior and anteroinferior shoulder dislocation are an anteroinferior labral avulsion with or without bony fragment of bone loss – a (bony) Bankart lesion – and a posterolateral humeral head impaction fracture – the Hill-Sachs lesions. These are relatively straightforward to identify on imaging, although normal variants of the inferior labrum and variants of labral damage may cause confusion. Other capsuloligamentous lesions, often associated with less typical types of instability, are much more difficult to identify correctly on imaging, as they occur in the anterosuperior part of the glenohumeral joint with its many normal variants or because they result in more subtle, and therefore easily overlooked, changes in morphology or signal intensity. This paper aims at describing the appearance of the normal and pathologic glenohumeral joint related to shoulder instability. Ample reference will be given as to why identification of abnormalities, whether normal or pathologic, is important to the surgeon facing a treatment decision.

Management of bone loss in glenohumeral instability

This review discusses the evaluation and management of bone loss in glenohumeral instability. The glenohumeral joint may experience a dislocation or subluxation associated with traumatic injury or through repetitive atraumatic events. Nearly 62% of cases with recurrent dislocation have both Hill-Sachs and bony Bankart defects. Treatment of unstable bone defects may require soft-tissue repair, bone grafting, or both, depending on the size and nature of the defects. The most common treatment is isolated soft-tissue repair, leaving the bone defects untreated, although emerging evidence supports directly addressing these bony defects.

Management of humeral and glenoid bone loss in recurrent glenohumeral instability

Recurrent shoulder instability and resultant glenoid and humeral head bone loss are not infrequently encountered in the population today, specifically in young, athletic patients. This review on the management of bone loss in recurrent glenohumeral instability discusses the relevant shoulder anatomy that provides stability to the shoulder joint, relevant history and physical examination findings pertinent to recurrent shoulder instability, and the proper radiological imaging choices in its workup. Operative treatments that can be used to treat both glenoid and humeral head bone loss are outlined. These include coracoid transfer procedures and allograft/autograft reconstruction at the glenoid, as well as humeral head disimpaction/humeroplasty, remplissage, humeral osseous allograft reconstruction, rotational osteotomy, partial humeral head arthroplasty, and hemiarthroplasty on the humeral side. Clinical outcomes studies reporting general results of these techniques are highlighted.