CHARACTERIZATION OF HUMAN DELTOID MUSCLE IN PATIENTS WITH IMPINGEMENTSYNDROME

Muscle biopsies from the anterior and medial parts of the deltoid of 1 1 male patients and six male controls were analysed with morphological and immunohistochemical methods. The distribution, area, and capillar ization of the muscle fibres were determined: and the amount of connec tive tissue was measured with staining for type-III collagen. Compared with the controls, the patients with impingement syndrome had more ty pe-I than type-II fibres, but the areas of the different types were al most the same. There was Ilo difference in capillarization per fibre t ype between patients and controls, but the patients had more connectiv e tissue. The results indicate that patients with impingement syndrome have morphological changes in the deltoid muscle, probably due to imm obilisation and pain. They support the hypothesis that the deltoid mus cle, the medial part in particular, is affected in patients with impin gement syndrome.