Ultrastructural changes in paravertebral muscles associated with degenerative spondylolisthesis

Study Design. The paravertebral muscle of 30 patients with spondylolisthesi s and 30 control patients were investigated histologically. Objective. To propose myopathologic paravertebral muscle changes in cases o f degenerative lumbar spondylolisthesis. Summary of Background Data. The stability of the vertebral column is based on both active and passive systems. The passive system is composed of the v ertebrae, the intervertebral discs, and the ligaments. Surrounding muscles and tendons constitute the active system. The autochthonous back muscles ta ke over support functions if the passive system is ineffective. In some cas es, muscles are overstrained for a long period, ultimately leading to muscu lar changes. This study was performed to determine the histopathologic corr elates of this permanent strain. Methods. Between July 1998 and July 1999, paravertebral muscle biopsies wer e performed for 30 patients with monosegmental degenerative spondylolisthes is undergoing posterior lumbar interbody fusion. The tissue samples were su bmitted to histologic analysis including immune and enzyme histochemistry a nd electron microscopy. In addition, the muscle fibers were submitted to mo rphometry. Results. Severe pathologic alterations were found. The findings showed that 22 patients (73.3%) had ragged red fibers with evident ultrastructural mit ochondrial anomalies. The cristae appeared irregular in 12 patients (40%) T ype 1 paracrystalline inclusions were detected in five samples (16.6%) and dense bodies in eight (26.6%). Fibers with ubiquitin-positive inclusions we re detected by immunohistochemistry in 13 patients (43.3%). As shown by the electron microscope, these corresponded to granulofilamentous inclusions a nd polyglucosan bodies. The samples were submitted to genetical analysis be cause biochemical studies showed reduced activity of the respiratory chain enzymes. Normal mitochondrial deoxyribonucleic acids of unchanged length we re detected. Conclusions. Apart from nonspecific myopathic changes such as those observe d in rimmed vacuoles and rods, increased numbers of polyglucosan bodies wer e detected. This increase in polyglucosan bodies currently has not been des cribed in patients with otherwise normal muscles.