Correlation Between Vertebral Canal Occupying Ration Of Severe Cervical Ossification Of Posterior Longitudinal Ligament And Postoperative C₅ Palsy

Objective:To investigate the relationship between the incidence of C5 palsy and the vertebral canal occupying ratio after posterior cervical double open-door laminoplasty in severe cervical ossification of the posterior longitudinal ligament(OPLL).Method:From January 2014 to January 2017,a total of 44 patients with severe OPLL(vertebral canal occupying rate>50%)were divided into 2 groups according to whether has postoperative C5 palsy :11 in palsy group and 33 in non-palsy group.This series included 23 males and 21 females,and their age ranged 34-72 years old,with an average of 56.5 years.All the patients underwent imaging examination.The vertebral canal occupying ration,the number of vertebral involved,OPLL classification,preoperative and postoperative Cobb's angles and Japanese Orthopaedic Association(JOA)scores for neurological function were measured and recorded.And the Improvement rate of Cobb's angle and JOA scores were calculated.The t test was used to analysis whether the differences in above factors between the 2 groups were statistically VII significant.Spearman correlation analysis and Logistic regression analysis were used to evaluate the correlation between statistically differences factors and postoperative C5 palsy.Result:T test results show that canal occupying rate in the paralysis group(62.22±5.15)was higher than Canal occupying rate in non-paralysis group(57.11±4.95),the difference was statistically significant(T=-2.919,P= 0.006);preoperative JOA score in paralysis group(9.41±1.72)is lower than preoperative JOA score in non-paralysis group(10.70±1.63),the difference was statistically significant(T= 2.246,P= 0.030);postoperative JOA score in paralysis group(12.41±1.93)is lower than postoperative JOA score in non-paralysis group(14.00±1.70),the difference was statistically significant(T= 2.598,P= 0.013);The improvement rate of JOA score in paralysis group(40.05±17.95)is lower than the improvement rate of JOA score in non-paralysis group(54.49±18.86),the difference was statistically significant(T= 2.224,P= 0.032);There were no significant differences in the age,the number of vertebral bodies,the change rate of Cobb angle,preoperative and postoperative Cobb angle,and the type of ossification of posterior longitudinal ligament between the two groups.Spearman correlation analysis showed that there is a positive correlation between canal occupying rate and C5 palsy(?= 0.355,P= 0.018);There is a negative correlation between preoperative JOA score and C5 palsy(?=-0.327,P= 0.030);There is a negative correlation between postoperative JOA score and C5 palsy(?=-0.368,P= 0.014);There is a negative correlation between improvement rate of JOA score and C5 palsy(?=-0.318,P= 0.036);Logistic regression analysis demonstrated that only OPLL occupying rate was into the equation,there is correlation between the canal occupying rate and C5 nerve root palsy(OR= 1.382,P= 0.021).Conclusion:The incidence of postoperative C5 nerve root palsy is is higher in patients with severe cervical OPLL.The vertebral canal occupying ratio is positively correlated with postoperative C5 palsy.The higher the vertebral canal occupying ratio,the higher the incidence of postoperative C5 palsy.