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Background
The basal joint of the thumb is one of the most common joints in the hand to be affected by osteoarthritis (OA), a close second behind the distal interphalangeal joints of the fingers. Arthritides of the basal thumb joint can become symptomatic with loss of normal joint range of motion, function, and pain. Imaging plays a critical role in the initial evaluation, clinical management, and follow-up of patients with symptomatic OA. Given both the prevalence of OA at the basal joint of the thumb, as well as the frequency with which patients are treated for this condition, a solid base of knowledge is crucial for radiology learners encountering these patients in their training and future practice.

Educational Goals / Teaching Points
Goals and teaching points of the exhibit include: improving anatomic knowledge pertaining to the basal joint of the thumb, understanding the Eaton Classification system for radiographic assessment of basal thumb OA severity, increasing familiarity with both common nonsurgical and surgical options for contemporary management of symptomatic thumb OA, identifying normal postoperative appearances to common surgical techniques, and recognizing potential complications of common surgical techniques.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Basic anatomy of the basal thumb joint with descriptions of articulating surfaces spanning the trapezium, first metacarpal (MC), second MC, and scaphoid, as well as the main supporting ligaments and adjacent tendons will be reviewed. The radiographic assessment of basal thumb OA with the Eaton Classification and imaging examples of Eaton grades will be presented. Descriptions of nonsurgical management techniques for symptomatic OA will be included. Description of common surgical techniques currently in use for symptomatic OA will be described including: ligament reconstruction with tendon interposition, suspensionplasty, implant arthroplasty, and first CMC arthrodesis. Imaging examples of these common surgical techniques will be spotlighted. In addition, imaging examples of possible complications encountered following common surgical techniques will be presented.

Conclusion
The basal joint of the thumb is one of the most commonly symptomatic and surgically intervened upon joints in the hand. A core understanding of the pathophysiology, imaging appearance, and common surgical procedures for symptomatic thumb base OA along with potential postoperative complications allows radiologists to best serve these patients and their referring clinicians.