Effect Of Anterior Cervical Plate Position On Postoperative Adjacent Segment Degeneration

Objective To investigate the effect of plate position on adjacent segment degeneration after anterior cervical decompression and fusion.In order to guide the accurate placement of the cervical plate and reduce the occurrence of adjacent segment disease.Methods From January 2010 to December 2012,a total of 35 patients with degenerative cervical myelopathy,who received anterior cervical decompression and fusion,were retrospectively viewed.There were 23 males and 12 females in the group,with an average age of 51 years old(range 30-82 years old).Each patient was followed up at least 12 months,the average follow up time was 28 months.Four indices of cervical plate position were measured on postoperative radiographs, including lateralization,rotation,plate to disc distance(PDD) and plate coverage of the vertebral body(PCVB).The changes about degree of bone hyperplasia,R value and α angle of the adjacent segment at postoperative and the latest follow-up, were compared respectively.Results In cephalad PDD groups,there were twelve cases grade 0,seven cases grade 1,three cases grade 2 at group A and group B all six cases were grade 0 about degree of bone hyperplasia. It had a significant difference between the two groups(P<0.05).In plate rotation groups,the degree of bone hyperplasia about cephalad adjacent segment were one case grade 0,four cases grade 1,two cases grade 2 at non-rotation group,all eleven cases were grade 0 at rotation to the lighter symptom side group,and six cases grade 0,three cases grade 1,one case grade 2 at rotation to the severer symptom side group.It had a significant difference between the three groups(P<0.05).In plate lateralization groups,the degree of bone hyperplasia about caudal adjacent segment were three cases grade 0,one case grade 1,two cases grade 2 at non-lateralization group,six cases grade 0,three cases grade 1 at lateralization to the lighter symptom side group,and one case grade 0,seven cases grade 1 at lateralization to the severer symptom side group.It had a significant difference between the three groups(P<0.05).About the change of α2 angle of caudal adjacent segment,there were 5.96±3.02° at non-lateralization group,3.39±3.16° at lateralization to the lighter symptom side group and 0.52±3.50° at lateralization to the severer symptom side group.It had a significant difference between the three groups(P<0.05).We didn’t found the significant difference in the PCVB groups.Conclusion The inappropriate placement of cervical plate will influence the occurrence of postoperative adjacent segment disease.When cephalad PDD <5mm,the degree of bone hyperplasia of adjacent segment is severer.There is an effect on the degree of bone hyperplasia of cephalad adjacent segment in cervical plate’s rotation.It has difference on the degree of bone hyperplasia of caudal adjacent segment in cervical plate’s lateralization.At the same time,non-lateralization group has better effect on maintain the physiological curvature of cervical spine.