THE LUMBAR MULTIFIDUS MUSCLE 5 YEARS AFTER SURGERY FOR A LUMBAR INTERVERTEBRAL DISC HERNIATION

Biopsy specimens of the lumbar multifidus were obtained from 18 patien ts with lumbar disc herniation at operation and after a postoperative follow-up period of 5 years. The structure and morphometry of the musc le fibers were analyzed and these data were compared with intraoperati ve biopsy results and the clinical outcome of the operation. The main findings were: 1) on the basis of occupational handicap score 10 patie nts belonged in the ''positive'' and 8 in the ''negative'' outcome gro up; 2) the intraoperatively recorded selective type 2 muscle fiber atr ophy and the extent of pathologic inner structure changes both decreas ed in the ''positive'' outcome group, whereas they persisted in the '' negative'' group; 3) grouping as a definite sign of reinnervation was seen in only two versus four patients of the ''positive'' versus ''neg ative'' outcome group; 4) the relative amount of adipose tissue within the muscle decreased more markedly in the ''positive'' outcome group. The authors propose that both inactivity and axonal injury (mainly of neurapraxia type) contribute to the selective type 2 atrophy and inne r structure changes in disc patients' multifidus muscle. These patholo gic structural changes correlated well with the clinical outcome, and most importantly they are reversible and can be diminished by adequate therapy.