Objective: Using 4-dimensional computed tomographic scanner to determine the motion pattern of the acromioclavicular (AC) joint during adduction of the arm, with and without resisted superior elevation.
Methods: Sixteen healthy volunteers (5 women and 11 men; mean ± SD age, 42 ± 11 years). Four different motions were measured: AC joint width, anteroposterior translation, superoinferior translation, and opening of the superior aspect of the joint. Measurements between arm positions of neutral, adduction, and loaded were compared.
Results: Predominant movement is posterior translation (1.1 ± 0.9 mm, P = 0.001); in the coronal plane, superior translation of the clavicle (0.6 ± 0.5 mm, P = 0.001) and some opening of the superior joint space. Changes in the AC joint width and anteroposterior translation were significantly related to age (P = 0.016 and P = 0.006).
Conclusions: Four-dimensional computed tomographic scans record the motion pattern of an asymptomatic AC joint and demonstrated that in adduction plus resisted elevation of the arm, the main movement of the AC joint is posterior and superior translation of the clavicle.
From the *Melbourne Shoulder and Elbow Centre, Melbourne, Australia; †Department of Orthopaedic Surgery and Traumatology, Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands; ‡Department of Surgery, Monash University, Melbourne, Australia; and §Department of Diagnostic Imaging, Monash Medical Centre, Melbourne, Australia.
Received for publication March 14, 2012; accepted August 6, 2012.
Reprints: Simon N. Bell, PhD, FRCS, FRACS, FAOrthA, Melbourne Shoulder and Elbow Centre, 31 Normanby St, Brighton, Victoria 3186, Australia (e-mail: email@example.com).
No funding was received from the National Institutes of Health (NIH), Wellcome Trust, Howard Hughes Medical Institute (HHMI), or any other source.
Ethical Board Review statement: Research Directorate, Southern Health, Monash Medical Centre, Melbourne, Australia Approval number 09247B; approved October 20, 2009.