Abstract des Autors

Magnetic resonance imaging (MRI) has become an important part in orthopedic diagnostics of the shoulder. Its application has, however, so far been confined to the description of morphological alterations. Quantitative data have been obtained with conventional radiographic techniques or in cadaver specimens in vitro, but this implies important limitations. Open MRI systems in combination with three-dimensional digital post-processing methods open new possibilities for studying biomechanical questions in vivo and performing functional diagnostics in the shoulder. An open MR imaging system (Magnetom Open, Siemens) was used for examining the shoulders of twelve healthy volunteers and ten patients (with complete rotator cuff tear or early stage impingement syndrome) in different abduction positions of the arm (30ø-150ø) - with and without muscle activity. After three-dimensional reconstruction the minimal spatial distance between the humerus and the acromion was calculated. In healthy volunteers, the sub-acromial space became narrower during abduction from 30ø to 120ø. Under abductor muscle activity there was a significant reduction of the space at 60ø, and a widening at 120ø of abduction. In patients with early impingement syndrome, a reduction of the acromiohumeral distance was only apparent under muscular activation (relative to the healthy contralateral side), but not at the state of muscular relaxation. With open MRI it has become possible to investigate joints in functionally important positions with and without muscle activity. Using three-dimensional digital postprocessing methods (rather than earlier 2D MRI or CT based techniques) quantitative data can be obtained independent of the specific section position and orientation. The technique presented can help to clarify the pathogenesis and functional implications of joint diseases. In the future, it may be applied for improving the diagnostics and evaluating the outcome of therapeutic interventions. Verf.-Referat