Use K Line For Making Decision Regarding The Sugical Strategy For Cervical Ossification Of Posterior Longitudinal Ligament

Objective:To verify the role of the line connecting the midpoints of spine canal at C2and C7on lateral radiograph (K-line) on determining surgical strategy for cerivalossification of posterior longitudinal ligament.Methods: In this study a retrospective review was performed on78patients (52malesand26females) with OPLL.including laminoplasty(40) and laminectomy andinstrumentation(38).The mean age at surgery was54.5years (range from42to77years).All patients were classified into2groups according to their K-line relating tothe range of OPLL,K-line positive (OPLL beyond K-line) and K-line negative (OPLLnot beyond K-line). The preoperative and postoperative,and1year after JOAscores,and improvement rate was recorded to analyze the influence of two approacheson the outcome.Results: All patients were followed up for more than1year (average15.3morths).The JOA score of K-line(+) group improved from pre-operative10.4to14.8at1yearafter operation,with an average improvement of4.4. The score of K-line (-)groupincreased from pre-operative10.4to13.4at1year after operation,with the meanimproved of3.0. The mean JOA improve rate was63%for the K-line(+) group and49%for the K-line group (P<0.05).In group K(+),the JOA improve rate forlaminoplasty was62%,and58%for laminectomy,which showed no significantdifference(P>0.05).In group K(-),the JOA improve rate for laminoplasty was42%,and67%for laminectomy,which showed significant difference(P<0.05).Conclusions: As a simple and practical index,thd K-line can effectively predict thesurgical outcome of posterior decompresion for cervical OPLL and therefor is usefulfor surgeous to determine the appropriate surgical strategy. Preoperative K(+)predicates a better JOA improve rate than K(-).laminectomy and instrumentationprovide a better JOA improve rate than laminoplasty.