Relationship between the histological findings of spondylolytic tissue, instability of the loose lamina, and low back pain.

STUDY DESIGN

We investigated the histomorphological features of the tissue occupying the spondylolytic defect (spondylolytic tissue), which was similar to ligament, and then graded the complete enthesis structure and the density of the fibrous portion. The relationships between the features, instability of the loose lamina against the affected vertebra, and the severity of low back pain were studied.

OBJECTIVE

To elucidate the histomorphological features of spondylolytic tissue and the associations between the features, instability of the loose lamina, and low back pain.

SUMMARY OF BACKGROUND DATA

Spondylolysis is thought to be caused primarily by a fatigue fracture and spondylolytic tissue has been recognized as being a fibrocartilaginous mass. Recently, innervation of the spondylolytic tissue was reported to be one of the sources of low back pain.

METHODS

The spondylolytic tissue from 17 patients who underwent microscopic decompression of the pars defect was observed for histology including hematoxylin and eosin, elastica van Gieson, and immunohistochemical staining for S100 protein. Instability of the loose lamina against the affected vertebra was evaluated by flexion/extension radiographs.

RESULTS

The spondylolytic tissue had a ligamentous structure without innervation. The histomorphological findings, instability of the loose lamina, and low back pain had no relationship to one another.

CONCLUSION

Spondylolysis is a pseudarthorosis of the pars interarticularis and the spondylolytic tissue tends to develop noninnervated ligament-like tissue with an enthesis structure. The histomorphological features, instability of the loose lamina, and low back pain have no relationship to one another.