ABSTRACT
BACKGROUND:Along with the widespread application of biodegradable materials in the field of medicine and the in-depth research of biomechanics,the drawbacks of traditional medical metal materials are increasingly appearing.In recent years,researchers at home and abroad focus on biodegradable materials that are represented by high molecular polymer to seek new breakthroughs in the field of spinal instability.OBJECTIVE:To investigate biomechanical changes of polylactic acid-polyglycolic acid (PLGA) lumbar interbody fusion cage in the body and discusses its feasibility for treating segmental instability of the spine.METHODS:Forty-two healthy pigs (9 months old) were randomly divided into two groups (n=21),and L4/5 intervertebral disc nucleus pulposus was removed in all animals.In experimental group,PLGA lumbar interbody fusion cage filled with broken bone was implanted;and in control group,autologous bone was implanted.X-ray was performed to observe the fusion of operation segments at 4,12 and 72 weeks postoperatively.Feasibility of fibrous fusion was measured by biomechanical test.Histologically,bone graft fusion at the surgical site and material degradation were detected.RESULTS AND CONCLUSION:(1) Imaging examination:Bone graft fusion in two groups was not visible at 4 weeks after operation.Evidence of increasing fusion was found in the experimental group at 12 weeks after operation;a visible part of the bone bridge was found in the control group,in which there was one case of fusion.Degradation of the fusion cage with one case of fusion in experimental group was found after 72 weeks after operation,and two cases of fusion in the control group.(2) Biomechanical test:There was no difference in the spinal range of motion between the two groups in different states at 4 weeks after operation (P ＞ 0.05).The spinal range values of motion at most of the states at 72 weeks after operation were significantly lower than those at 4 weeks after operation.(3) Cell histology observation:With the passage of time,the materials in the experimental group degraded gradually;new bone grew slowly and then fast,with bone fusion step by step.Fusion results were similar in the two groups.Our experimental findings indicate that the PLGA lumbar fusion cage has good biocompatibility.In addition to the individual state (left flexion),the mechanical properties of the fusion cage are similar to that of autogenous bone,and the fusion cage enables the segmental reconstruction of the pig spine to the maximum extent.