Injection of PMMA bone cement into fractured vertebral bodies has been used clinically and proved to be effective. However, there are concerns about thermal injury to the cord and interferece of bone remodling .The purpose of this study is to use the biodegradable bone substitute as an alternative for augumentation of fractured vertebral bodies .

Material and Methods: From April 1998 to January 2000, 10 patients(Nine females and one male, age from 55 to 74 years) with osteoporotic compression fractures were retrospectively reviewed. The level of compression fracture mostly occurred at T12-L1 (Nine of ten cases). Eight of the ten cases were osteonecrosis of vertebral body with vaccum phenomenon. While other two cases had gross kyphotic deformity. Surgical indications for these ten patients include back pain, progressive kyphosis and failure of conservative medical treatment. (No neurological deficits were noted in all ten cases.) All ten cases underwent posterior instrumentation with vertebroplasty (Bipedicle impaction of osteoset and iliac bone autograft). The anterior body height and the kyphotic angle were measured preoperatively and postoperatively. The fusion mass was observed and followed up with T-L spine AP and Lateral X-ray regularly.

Result: The anterior body height increased over 50% in all cases in this series. The average correction of kyphosis angle is 10 degree. Stable arthrodesis with obvious fusion mass occurred in all patients under X-ray image. Postoperative pain relief were noted in all ten patients. No major complications were related to this procedure.

Conclusion: This preliminary study shows that vertebroplasty using osteoconductive biodegradable bone substitute and osteoinductive iliac bone autograft in osteoporotic compression fracture with osteonecrosis is feasable and effective. The technique might also provide an alternative for treatment of osteoporotic compression fractures instead of PMMA bone cement.

Background Data: Postoperative spondylothesis had been noted for many years, first reported by White in 1977. Biomechanic effect of the facetectomy was reported by Abumi in 1992. There were few reports about the results of surgical treatment for postoperative spondylolisthesis.

Purpose: To assess the outcome of surgical treatment for postoperastive spondylolisthesis and examine the factors that might correlate with postoperative spondylolisthesis.

Materials and Methods: This study retrospectively reviewed twenty seven patients (eleven male and sixteen female), from 1979 to 1996, who received pedicle screws instrumentation and posterolateral fusion for postoperative spondylolisthesis. Average age was 57.3 years old (from 36.6 to 79.5 years old). Average follow-up time was 40.0 months (from 24 months to 72 months). The grade of fcetectomy, percentage of vertebral slipping, and disc narrowing was checked by plain X-ray. End results were assessed using the modified Stauffer-Coventry’s evaluation criteria.

Results: The mean period of postoperative instability was 49.3 months (from 6 months to 141 months) in whole group, 43.7 months (from 6 months to 129 months) in laminectomy group, 43.4 months (from 17months to 82 months) in laminectomy and disectomy groups, and 74.6 months (13 months to 141 months) in disectomy group. After an average follow-up period of 40 months, 29.6 % of patients had excellent results, 44.5% had good results, and 25.9 % had fair result. No complication was found in this study.

Conclusions: Pedicle screw instrumentation with posterolateral fusion can get satisfactory result for postoperative spondylolisthesis.