Ceramic substitutes, failure to achieve solid fusion in posterolateral instrumented fusion: a surgical and histological evaluation.

PURPOSE: As the number of instrumented fusions increases, so does the utilization of bone substitutes. However, controversies persist regarding the effectiveness of ceramics in promoting solid fusion. Few histological studies have been conducted on patients to address this issue. To contribute insights into this topic, we assessed bony fusion both intraoperatively and histologically in patients who underwent posterolateral instrumented fusions enhanced with a biphasic ceramic compound.

METHODS

We analyzed a series of 13 patients who underwent revision surgery due to adjacent segment disease following the initial use of ceramics as bone extenders in the index surgery. In each case, patients exhibited apparent radiological fusion in the instrumented posterolateral fusions. Follow-up exceeded 18 months. Bone fusion was assessed intraoperatively, and biopsies of the bone mass at the intertransverse area were examined under an optical microscope.

RESULTS

Surgical exploration of the fusion block at the intertransverse space did not indicate solid fusion. Moreover, histological analysis of the 13 biopsies revealed a lack of proper integration of the bone substitutes, incomplete resorption of hydroxyapatite granules, and substitution of ceramic particles by immature fibrous tissue lacking the structural competence to bear loads or add stability to spinal fusion.

CONCLUSION

The utilization of biphasic ceramics proved ineffective in attaining a proper fusion mass between the intertransverse space. Both surgical inspection and histological studies confirmed the absence of integration. Prudence should be exercised regarding the use of ceramics. While no clear instability was observed, neither was there any integration.