Experimental And Clinical Studies Of Anterior Cervical Plate Fixation

Anterior cervical decompression, interbody fusion and plate fixation has come to be a common surgical procedure for cervical disorders. So, anterior cervical plate system has become an implant full of prospects. However, there isn't a national product of the plate stepped with international standards at present. Thus, we were devoted to design a fixation system named anterior cervical low-profile plate system and performed its experimental and clinical tests to make it a national cervical implant. And in order to learn if it is necessary to plate after single-level anterior cervical decompression and fusion, an international controversy in the academic circle, we were engaged in a series of biomechanical tests and long-term follow-up studies. As a result, we found it's of no necessity to plate after anterior cervical decompression and fusion to the cases of mono-segmental cervical disc herniation and cervical spondylosis without obvious kyphotic deformity or segmental lability. Furthermore, we sprayed the anterior cervical low-profile plate system with bioactive glass to further proof against loosening. Some related experiments and clinical application were carried out to make it a new product of anterior cervical fixation for the near future.Part 1. Design, biomechanical evaluation and clinical application of anterior cervical low-profile plate systemObjective To evaluate the biomechanical stability and the clinical efficacy of self-designed anterior cervical low-profile plate system (ACLPS) . Methods The anterior cervical plate system is composed of one plate, two locking caps and two types of screws. All of the components are made of medical titanium alloy on the basis of low profile, instant locking, varied types, and unicortical screw fixation. 16 cervical spine specimens(C2-T1) were divided into two groups, A and B. The displacements under the normal load of all intact specimens had been recorded before their fifth vertebral bodies and adjacent discs were removed and iliac bones were implanted. The samples of A group were fixed by ACLPS while the ones of B, Orion.Then, their load-displacement, axostiffness, torque, twisting stiffness and ultimate mechanical performance were tested and compared. And furthermore, two sets of ACLPS were subjected to pull-out test, strength test and fatigue test. At last, three dimensional finite method was employed to analyze the variation and distribution of the stress of the ACLPS. 18 patients with cervical disorders were stabilized with ACLPS. The diagnosis included spondylosis in 4 cases, cervical intervertebral disk protrusion 6,fracture and (or) dislocation with paraplegia 7 and metastatic tumor 1. Results There is no difference between the groups of ACLPS and Orion, not only in the ranges of displacement decrease, but in all longitudinal displacements after fixation (P>0.05). The axostiffness, torque, twisting stiffness and ultimate mechanical performance of ACLPS were similar to those of Orion (P>0.05). The maximum pull-out force and its relative displacement and energy absorption of ACLPS were almost the same to those of Orion (P>0.05). And its fatigue strength was 473.27Mpa. The systems could bear 5.5.05 times of loading on average before they appeared fissures external to screw holes, which was sufficient for safe and long-time fixation. Although it was predicted that stress concentration were locationally circumferential to the holes of ACLPS, the diameter of holes and the distance of edges were still in the margin of safety. Of 18 cases received the fixation of ACLPS after anterior cervical decompression and interbody fusion, all were followed-up and 15 showed solid interbody fusion while the other 3 were still within half past a month after the operation. No complications such as implant loosening or failure related to the plate fixation system were noted. Conclusion ACLPS can provide sufficient biomechanical stability and is suitable for clinical application.Part 2. An investigation of the comparison between single-level anterior decompression an...