EFFECTS OF VOLUME OF BONE-GRAFT ON FUSION EFFICACY IN POSTERIOR LUMBAR INTERBODY FUSION AND INTERNAL FIXATION OF SPONDYLOLISTHESIS

Objective To investigate the relationship between the volume of bone-graft and fusion efficacy in posterior lumbar interbody fusion and internal fixation of spondylolisthesis.Methods Between May 2004 and June 2007,79 patients with spondylolisthesis were treated with posterior lumbar interbody fusion and internal fixation.The patients were randomly divided into 3 groups according to the volume of bone-graft for interbody fusion: group A(n=27),5 bone granules/?cm3 on average;group B(n=26),11 bone granules/cm3 on average;and group C(n=26),25 bone granules/cm3 on average.There was no significant difference in gender,age,disease duration,affected segment,and the degree of vertebral slip among 3 groups(P? 0.05).The volume of bone-graft,the fusion rate,the loss of intervertebral height,and the incidence of internal fixation failure were compared among 3 groups.Results All cases were followed up 24-43 months(mean,35 months).There were significant differences in volume of bone-graft among 3 groups(P 0.05).There was no significant difference in total volume of bone-graft and Cage height among 3 groups(P 0.05).The Oswestry disability index(ODI) and visual analogue scale(VAS) scores of low back pain and leg pain at last follow-up were significantly decreased when compared with preoperative scores in 3 groups(P? 0.05);but no significant difference was found among 3 groups(P 0.05).The fusion rate was significantly higher in group B than in groups A and C,and in group A than in group C at 1 and 2 years after operation(P? 0.05).The change values of the intervertebral height were(2.2 ± 1.4),(0.8 ± 1.3),and(2.3 ± 1.6) mm respectively in groups A,B,and C;it was significantly lower in group B than in groups A and C(P 0.05).The degree of vertebral slip at immediately after operation and last follow-up was significantly improved when compared with preoperative one in 3 groups(P 0.05);the loss of vertebral slip in group B was significantly lower than that in groups A and C at last follow-up(P 0.05).After operation,nail breaking occurred in 1 case(3.7%) of group C at 1 year,depinning in 1 case(3.8%) of group A at 2 years,and no nail breaking or depinning in group B.There was no significant difference in the incidence of internal fixation failure among 3 groups(χ2=3.950,P=0.604).Conclusion The application of bone-graft with middle volume(11 bone granules/cm3 on average) in internal fixation and posterior lumbar interbody fusion has a good imageology outcome,which can increase the fusion rate and decrease the loss of intervertebral height.