RESUMO
Objective To investigate the effect of bisphosphonate medication (zoledronic acid,aclasta) on spinal fusion for osteoporotic patients through radiographic,clinical,and biological assessments.Methods A total of 79 patients with osteoporosis who were candidates for single-level posterior lumbar interbody fusion was randomly assigned to the experimental group (zoledronic acid injection,5mg,on the third day after surgery) or the control group (the same amount of saline injection,on the third day after surgery).Functional radiography and CT scans were used to evaluate fusion status.Bridging bone formation was graded into 3 categories:Grade A (bridging bone through bilateral vertebral),Grade B (bridging bone through a unilateral vertebral),or Grade C (incomplete bony bridging).The incidence of vertebral compression fractures occurring after surgery was assessed by means of MR imaging.A solid fusion was defined as less than 5° of angular motion in flexion-extension radiographs and the presence of Grade A or B bridging bone.Bone metabolic markers (β-C-terminal telopeptide of type Ⅰ collagen,β-CTX; and N-terminal propeptide of type Ⅰ collagen,PINP) were measured to investigate the biological effects of zoledronic acid on spinal fusion.Bone mineral density of femoral neck was measured by the dual X-ray absorptiometry.Clinical outcome was evaluated by means of the Oswestry Disability Index (ODI).Results Grade A or B bridging bone was more frequently observed in the experimental group at 3,6,and 9 months postoperatively (all P ＜ 0.05,respectively,Mann-Whitney U-test).At 12-months postoperative follow-up,bridging bone and solid fusion were not significantly different.No vertebral fractures were observed in the experimental group,whereas 6 patients in the control group showed vertebral compression fractures(P ＜ 0.05,Mann-Whitney U-test).Biochemical analysis of bone turnover demonstrated that zoledronic acid inhibited bone resorption from the early phase of the fusion process and also suppressed bone formation.Poor clinical results in the control group were demonstrated by ODI.Conclusions Osteoporosis patients undergoing spinal fusion who take bisphosphonates throughout the postoperative period was recommended.