Biocompatibility studies of titanium-based alloy pedicle screw and rod system: histological aspects.

BACKGROUND CONTEXT: Few histological studies of pedicle screw and rod systems have been done, and spinal surgery with pedicle screw and rod system is increasing.

PURPOSE: To know the biocompatibility of pedicle screw and rod systems histologically.

STUDY DESIGN/

SETTING

Titanium-based alloy pedicle screws were removed from 20 patients. Histological studies of the tissue response to the screws were performed by light microscopy.

PATIENT SAMPLE: Twenty patients, who were diagnosed with burst type spinal fracture, spondylolysis, spondylolisthesis, and lumbar disc herniation.

OUTCOME MEASURES: All slides were observed by light microscopy, and inflammation, fibrous tissue formation, and wear debris were evaluated using a subjective scale.

METHODS

Before the surgery, plain radiographs were taken to confirm the solid arthrodesis. Histological analysis was divided into four areas and studied using light microscopy.

RESULTS

Inflammation and fibrous tissue formation were the main tissue reactions to the implants. No tissue surrounding the implants showed irreversible changes. Fibrous tissue was often observed at the bone-screw interface without direct contact of screw and bone at the muscle-screw interface histologically. Although some titanium debris was observed in both interfaces, no debris of inflammatory cells were seen at 1 cm distance from the screws. The inflammatory response to the screw debris was localized.

CONCLUSIONS

Titanium-based alloy pedicle screws produced some metal debris and caused localized inflammation. No adverse tissue reaction was observed around the screws and rods. Direct contact without any fibrous tissue formation at the bone-screw interface was observed in some patients. A titanium-based alloy pedicle screw and rod system is considered biocompatible histologically.