A histologic study of soft-tissue reactions to spinal implants

Objectives. The biologic reactions to orthopedic spinal implants were determined. Methods. Biopsies of soft tissue immediately adjacent to spinal implants were done in 36 consecutive patients undergoing elective lumbar spinal hardware removal and was studied histologically. Results. A fibrous tissue matrix was noted in all specimens. In 11 of 36 specimens, a discrete layer of cells with epithelial characteristics was noted on the surface immediately opposed to the metal implant. Results of immunohistochemical staining were negative using antibodies to markers, which suggests that these unique cell layers are probably of histiocytic origin. Black amorphous metallic debris was seen in nine of the specimens. In seven of these specimens, this material was associated with an inflammatory foreign-body reaction. Refractile non-biorefringent crystalline bodies were noted in five specimens. These crystalline deposits provoked a local foreign-body reaction in all cases. Conclusion. The role of soft-tissue inflammatory reactions in the production of clinical symptoms of pain is discussed.