Adjacent Segment Degeneration After Cervical Artificial Disc Replacement Vs ACDF

ObjectiveAnterior cervical discectomy and fusion(ACDF) may be considered to be the gold standard for treatment of symptomatic degenerative disc disease within the cervical spine.Many published series in the past have reported satisfactory clinical outcomes.ACDF is a safe and effective technique in providing symptomatic relief to the patients and excellent fusion rate. However, there are clues that ACDF may result in progressive degeneration of the adjacent segments. To avoid this,there have been numerous attempts to develop unfuson technology, artificial cervical disc replacement.It.a brand-new technology,has already been applied in cilinic.In earlier period clinic reoorts had shown that artificial cervical disc replacement is a effective technique in alleviateing the symptoms and preserving segmental motion.Accompany the follow-up time progression,many surgeons pay their attentions to the adjacent segment degeneration.Further investigation should be taken to compare the difference between artificial cervical disc replacement group and ACDF group in adjacent segment degeneration.This study compared the difference between artificial cervical disc replacement and ACDF in adjacent segment degeneration according to the clinical follow-up results of the patients taken artificial cervical disc replacement or ACDF. Finite element analyses was used to analyze the outcomes of adjacent segment degeneration and compare the adjacent level discs loads artificial cervical disc replacement or ACDF system.Methods 1.39cases (male:20, female:19, average age:47.15±7.72, ranging from32to65)of cervical spondylosis admitted to our department since2008were analyzed in this study.9patients(single-level:7,double-level:2) were performed with Prestige disc prosthesis,4patients(single-level:3,double-level:1)with Prodisc-C,and26patients (single-level:17,double-level:9) with Discover disc prosthesis.Neurological functional recovery was assessed after operation.Movement extention of adjacent segments was measured, and X-ray was used to evaluate the degree of adjacent segment degeneration.2.94cases (male:60, female:34, average age:50.93±9.17, ranging from28to70)of cervical spondylosis admitted to our department since2008were analyzed in this study.33patients were performed with single-level ACDF,35patients with double-level ACDF,and26patients with three-level ACDF. The cervical anterior-posterior and lateral X-ray and MRI examination were performed before the operation.Neurological functional recovery was assessed after operation. X-ray was used to evaluate the degree of adjacent segment degeneration according to the Kellgren’s standard.3. Japanese Orthopaedic Association (JOA) Scores and the adjacent segment degeneration status were compared between the group of39patients taken artificial cervical disc replacement and the group of90patients taken ACDF.4. Finite element analyses was used to analyze the outcomes of adjacent segment degeneration and compare the adjacent level discs loads after artificial cervical disc replacement with ACDF system.Results1. All39patients taken artificial cervical disc were followed up from16to42months with average of27.38±7.11months.Postoperative neurological function in patients was significantly improved, JOA score increased by5.21points on average, and the average improvement rate was57.44%, the efficiency rate was100%.Measurement results of replaced level and adjacent segment movement extention showed no difference in the pre-operation and post-operation (P>0.05).X-ray evaluation results showed that the occurrence rate of adjacent segment degeneration was12.80%,with5 cases of the39patients,but no significant differencewas found in degeneration when compared with pre-operation (P=0.269)2. All patients were followed up from16to45months with average of28.59±8.53months.Postoperative neurological function in patients was significantly improved, JOA score increased by5.8points on average, and the average improvement rate was64.3%, the efficiency rate was100%. X-ray evaluation results showed that the occurrence rate of adjacent segment degeneration was20.21%,with7cases of degeneration from grade0to grade2,1from grade0to grade3,1from grade0to grade4,3from grade1to grade2,4from grade1to grade3,3from grade2to grade4. Significant difference was found in degeneration when compared with pre-operation (P=0.001)3. The follow-up period in both groups was16to45months, with an average of27.38±7.11months of the TDR group and28.59±8.53months of the ACDF group.Postoperative neurological function in patients was significantly improved, JOA scores of the TDR group increased by5.21points on average,from9.08±0.93to be14.28±0.72. JOA scores of the ACDF group increased by5.41points on average,from9.16±0.98to be14.57±0.86.and the efficiency rate was100%.No statistical difference was found between both groups (P=0.074).According to Kellgren X-ray evaluation standard,there was no adjacent segment degeneration was obseverd in the replacement group.However,in the24.4th month there were5cases appeared adjacent segment degeneration on average follow-up time,with3cases discs degeneration changed from0grade to2grade,1case from1grade to2grade,1case from2grade to3grade,and the average degeneration rate was12.8%.In the ACDF group,there were17cases appeared adjacent segment degeneration, with6cases of degeneration from grade0to grade2,1from grade0to grade3,1from grade0to grade4,2from grade1to grade2,4from grade1to grade3,3from grade2to grade4. X-ray evaluation results showed that the occurrence rate of adjacent segment degeneration were not significantly difference between both group(P=0.488).4. Based on the finite element analysis,we analized adjacent segment discs loads after artificial cervical disc replacement or ACDF.The study compared discs loads in the normal situation and fusion state(single-level and double-level).The discs loads were significantly higher in the fusion group compared with the normal situation. There was no difference of the loads between the normal and the replacement situation in antexion、extension and lateroflexion status. The discs loads were higher in the fusion group compared with the replacement group, raise10.3%～51.6%.ConclusionsBoth artificial cervical disc replacement and ACDF are highly effective in treatment of symptomatic degenerative disc disease.During the Early metaphase follow-up, no significantly difference of the adjacent segment discs degeneration is found in the ACDF group than the replacement group,and the degeneration time of the ACDF group is trend to be earlier than the replacement group. This study demonstrates that the loads of adjacent segment discs after ACDF are higher than artificial cervical disc replacement.Compared with the traditional ACDF, artificial cervical disc replacement may have a good efficacy against cervical spondylosis and cervical disc herniation, and have a better protective effect on adjacent segment discs during longer period follow-up.