The purpose of this study was to determine if the use of a new 4 Dimensional CT scan aids the clinician in defining the size and area of the scapular bone to be removed arthroscopically in patients with Snapping Scapular Syndrome.

From January 2009 – January 2011 nine consecutive patients with Snapping Scapular Syndrome were included. In six patients, (mean age 21±5 years, range 15–27) conservative treatment failed. These patients were positioned prone and demonstrated their snapping motion during the 7 seconds duration of the scan. The 4D CT machine scans 16 cm volumes in 0.3 seconds. It also scans motion, allowing a 3D reconstruction of the scapulothoracic joint, its’ movements and the dynamic area of impingement of the scapula on the surrounding structures. This scan has already improved arthroscopic removal of the supero-medial angle of the scapula.

The scan showed in one case not only snapping of the superior medial angle of the scapula on the 2nd rib, but also extra bone impinging on the 3rd rib. Another case showed no real impingement but movement of the 2nd and 3rd rib by a tethering structure and a third case demonstrated impingement of the lateral third of the clavicle on the 2nd rib.

The images provided by this new 4D CT scan offer greater pre-operative insight on the pathology in each individual patient with Snapping Scapular Syndrome. Therefore, we feel that it is a valuable addition to the assessment and treatment of these patients.

The purpose of this study was to determine the motion pattern of the Acromio-Clavicular (AC) joint in a normal shoulder with the use of the new 4 Dimensional CT scan.

From April 2010 till January 2011 fourteen healthy volunteers (4 female, 10 male)(mean age 42±11 years) with no previous history of shoulder complaints participated in this study. The 4D CT machine scans motion, allowing a 3D reconstruction of the shoulder joint and its movements. Patients were positioned supine with their arm elevated 90° in the sagittal plane. During the 7 seconds duration of the scan they adducted their arm at that level and then elevated their arm upwards resisted by the gantry for 4 seconds, in this way simulating the clinical Bell-van Riet test for AC pathology.

In the transverse plane the mean AC joint space measured in the neutral position is 1.8±0.5 mm. While adducting the arm the AC joint narrows 0.0±0.4 mm (with a positive value being narrowing and a negative value widening). On resisted elevation the joint space is narrowed 0.2±0.6 mm. The mean antero-posterior (AP) translation in this same plane is 0.2±2.2 mm on adduction (with a positive value being posterior translation of the clavicle and a negative value anterior translation) and 0.4±2.9 mm on resisted elevation.

The new 4D CT scan demonstrates that the AC joint in a normal shoulder mainly translates in an AP direction, rather than being narrowed or widened, when the arm is adducted (with or without resisted active elevation).