Effect Of Different Intervertebral Bone Graft Area Ratio On Lumbar Intervertebral Fusion

Objective:To explore the effect of the area ratio of intervertebral bone graft on the fusion effect and clinical efficacy of patients undergoing lumbar interbody fusion.Methods:The clinical data of patients who underwent lumbar interbody fusion in our hospital from January 2016 to December 2016 were retrospectively analyzed.The patients who underwent L4-5 or L5-S1 single segment surgery with complete follow-up data for nearly 3 years after surgery were selected,among which 51patients were eligible for the study.According to the bone graft area ratio,the patients were divided into three groups:group A(≥20%,<30%,17 cases),group B(≥30%,<40%,17 cases),and group C(≥40%,17 cases).Bone graft area ratio(%)=(bone graft area)/(average endplate area).The age,gender,bone mineral density,body mass index(BMI)and operative segment were recorded.Regular follow-up was conducted at 1 week,3 months,6 months,12 months and once a year after operation,and X-ray,CT and functional score of patients were detected.Brantigan-Steffee-Fraser(BSF)score was used to evaluate the interbody fusion,and the fusion rates at6 months,12 months and the last follow-up were recorded.Oswestry disability index(ODI)and visual analog scale(VAS)were used to evaluate the improvement of clinical symptoms.The height of intervertebral space was measured before operation,1 week and the last follow-up after operation.Results:There were no significant differences in age,gender,BMI,BMD,intervertebral height,ODI and VAS scores and operation segment among the three groups(P>0.05).The follow-up time of the three groups was 36-42 months,with an average of 38 months.The ODI and VAS scores at 1 week and at the last follow-up after operation in each group were significantly improved compared with those before operation(P<0.05),but there was no significant difference between the groups(P>0.05).The height of fusion cage among three groups had no significant difference(P>0.05).The height of intervertebral space at 1 week and at the last follow-up after operation in each group was significantly improved compared with that before operation(P<0.05);The height of intervertebral space at the last follow-up in group A,B and C were(9.87±2.64)mm,(11.94±2.32)mm and(11.94±2.09)mm,respectively,and the difference was statistically significant(P<0.05).The height of intervertebral space in group A was significantly lower than that in group B and C(P<0.05),but there was no significant difference between group B and group C(P>0.05);There was no significant difference in the fusion rate at 6 months and final follow-up after operationin among three groups(P>0.05).The fusion rates of group A,B and C were 29.4%,70.6%and 82.4%respectively at 1 year after operation(χ~2=11.023,P=0.004),the fusion rate of group A was significantly lower than that in group B and C(P<0.05).but there was no significant difference between group B and group C in 1-year fusion rate.Conclusion:Compared with the three groups of patients with different bone graft area ratio,the clinical symptoms were significantly improved,and the fusion rate of the last follow-up was relatively high,but there was no significant difference among groups.With the increase of bone graft area ratio,postoperative imaging evaluation showed that the larger the bone graft area ratio,the higher the early fusion rate,and reduced the loss of intervertebral space height.Long term follow-up showed that when the born graft area ratio was less than 30%,there was a hidden danger of bone graft non fusion.Therefore,it is suggested that the bone graft area ratio should be more than 30%.