This new data provides an important benchmark for patients with shoulder instability and rotator cuff tears because they have increased shifts inside the shoulder that may need surgical intervention. Our results indicate that during arm raises the humeral head shifts approximately 1.0mm upwards when raising the arm from the side until just above shoulder height and then drops back down. The images were analyzed and rotations and translations of the joints were described. Measurement of these ranges of motion are important because these are common motions for activities of daily living, they represent common motions assessed clinically for shoulder pathology, and they are often used as the benchmark motions for the design of new surgical techniques and implants that must be reached to restore normal function. To understand how a healthy shoulder functions, 10 healthy subjects were recruited to perform four basic motions inside the dual-plane fluoroscopy system: raising the arm at the side and in front of the body as high as possible, as well as rotating the arm in and out as far as possible with the arm at the side and with the arm raised 90 degrees (as in throwing a ball). Traditional methods of measuring shoulder motion in patients include palpation and attaching markers or sensors to the skin. Previously, it was impossible to measure how these four joints move with the accuracy needed to influence clinical diagnosis, understanding, and treatment of injuries to these joints.

The shoulder complex consists of four joints that move in concert to accomplish the largest range of motion of any joint complex in the human body.

Normal shoulder range of motion