Bone histomorphometric evaluation of a clinically fused titanium tumour cage in a child.

An intervertebral titanium tumour cage was implanted in a 2-year-old-girl after T11 spondylectomy due to Ewing sarcoma. After 2-years' follow-up without evidence of recurrence, the titanium cage was explanted to correct spinal deformity and to allow normal spinal growth development. Radiological follow-up and surgical exploration at the time of retrieval suggested fusion of the segment. Histologic evaluation, however, demonstrated ingrowth of trabecular bone, but without bridging trabecular bone. The distance between the opposing bone fronts measured 1.5 mm and the viable bone volume (BV/TV) within the cage was 36%. Histologic evaluation demonstrated that bone formation was still an ongoing process in the fusion zone 2 years after implantation.