Analysis Of Related Factors Affecting Prognosis After Indirect Decompression For Long Segmental Ossification Of Cervical Posterior Longitudinal Ligament

Objective: To discuss and explore the related factors affecting prognosisafter posterior operative procedures for long segmental ossification of cervicalposterior longitudinal ligament, and to compare the related factors affectingprognosis and postoperative complications after posterior approach betweencervical laminoplasty and laminectomy combined with lateral mass screw totreat cervical ossification of the posterior longitudinal ligament (OPLL).Methods: From February2009to January2012,42cervical longsegmental OPLL patients treated with posterior decompression wereretrospectively analyzed. Twenty patients underwent cervical laminoplastyand twenty-two patients underwent laminectomy combined with lateral massscrew. The preoperative and postoperative neurological status was evaluatedby JOA scoring system and the improvement rate was calculated．Continuousvariable including age, course of disease, occupying rate of OPLL, spinalcanal diameter, extent of OPLL, preoperative JOA score, preoperative cervicalcurvature and classified variable including sex, type of OPLL, diabetesmellitus, MRI hyperintense signal, type of operation were put into analysis.Bivariate linear regression analysis, t-test and analysis of variance were usedto find the most correlative factors affecting the improvement rate ofneurological function and multiple linear regression analysis was used to findthe predominant correlative factors.Results: All patients were followed up for12~39months，average(23.2±6.5) months. The mean improvement rate of JOA score was(58.50±15.01)%. Univariate analysis showed that the course of disease,occupying rate of OPLL, preoperative JOA score, preoperative cervicalcurvature, MRI hyperintense signal were the variable associated with the improvement rate (P<0.05). In contrast, there was no significantly correlationbetween other factors and the improvement rate (P>0.05). Coefficient ofproduct-moment correlation of the course of disease, occupying rate of OPLL,preoperative JOA score, preoperative cervical curvature was-0.385,-0.695,0.351,-0.612respectively. At final follow-up the improvement rate ofhyperintensity signal and no signal intensity on MRI was (50.62±11.75)%and(71.31±10.14)%, and the difference was significant (t=5.829, P＜0.001).Multiple linear regression analysis showed that the occupying rate of OPLL,MRI hyperintense signal and preoperative cervical curvature were thepredominant correlative factors affecting the improvement rate. Thestandardized partial regression coefficient was-0.377,-0.354,-0.335respectively. After further analysis of the degree of OPLL oppression andpreoperative cervical curvature, the result of showed that the improvement ratein severe oppression group (occupying rate of OPLL≥50%) was worse thanthat in mild oppression group (occupying rate of OPLL<50%) and theimprovement rate of cervical kyphosis was worse than that of cervical lordosis(t=4.499, P<0.001; t=2.744, P=0.009）. The improvement rate of laminoplastyand laminectomy with fusion group was (55.15±14.65)%,(61.55±15.01)%respectively, and the difference was not significant (t=1.395, P=0.171). Therewas no significant difference in the course of disease (t=0.022, P=0.982),preoperative JOA score (t=0.525, P=0.603), occupying rate of OPLL (t=0.133,P=0.895), rate of hyperintense signal (χ2=0.423, P=0.516), preoperativecervical curvature (t=0.274, P=0.786) and postoperative curvature (t=1.104，P=0.276) between laminoplasty and laminectomy with fusion group. Thedifference was significant in the loss of cervical curvature between the twogroups (t=3.827，P=0.001). Complications after laminoplasty included C5palsy in1patient and axial symptoms in10patients, and complications afterlaminectomy with fusion included C5palsy in1patient and axial symptoms in4patients. The difference was significant in the rate of postoperative axialsymptoms between the two groups (χ2=4.773，P=0.029).Conclusion: Preoperative occupying rate of OPLL, MRI hyperintense signal and cervical curvature are the predominant correlative factors affectingthe improvement rate of neurological status of long segmental OPLL. Theimprovement rate was not significant between laminoplasty group andlaminectomy with fusion group, but postoperative loss of cervical curvature ishigher in laminoplasty group than that in laminectomy with fusion group. Therate of postoperative axial symptoms is higher in laminoplasty group than thatin laminectomy and fusion group.