[Scapulohumeral arthrodesis by combined external and internal fixation. A biomechanical, technical and clinical study].

The indications for arthrodesis of the shoulder are controversial and limited and fusion is difficult to achieve, as is shown by the number of methods described in the literature. Since 1970, the authors have used combined internal and external fixation for arthrodesis of the shoulder. From a biomechanical study of arthrodesed shoulders, an attempt has been made to define the best combination of fixation. Three progressively more complex methods combining intra-articular fixation with a Hoffmann external fixator in compression have been tested. The ideal method combines transverse double scapulo-humeral screws with a vertical acromio-humeral screw. The addition of a bony subacromial strut controls the shearing effects arising from the application of the fixator in compression and also provides an upper site of fusion. In 14 arthrodeses using combined internal and external fixation analysed with a two to sixteen year follow-up, acromio-humeral fixation has been used in 11 cases with 10 primary successes and in 3 cases triple screw fixation has given very rapid fusion without the need for spica immobilisation.