Objective : This study aimed to reveal the factors associated between low back pain (LBP) and cervical spondylotic myelopathy (CSM) by analyzing preoperative clinical characteristics and surgical outcomes.
Methods : We retrospectively analyzed 67 patients with LBP among 285 patients with CSM who underwent cervical laminoplasty treated in 2014-2020. Of them, 67 patients with a visual analog scale (VAS, 0-100) score for LBP of ≥30 were included. Data including age, sex, Japanese Orthopaedic Association (JOA) Cervical Myelopathy Evaluation Questionnaire (CMEQ) scores, JOA Back Pain Evaluation Questionnaire (BPEQ) scores, VAS, Neck Disability Index (NDI) scores, and Oswestry Disability Index (ODI) were analyzed. Statistical analyses were performed of surgical outcomes using the Kruskal-Wallis test and Dunnett test. A forward stepwise logistic regression was used to identify possible predictors of the rate of improvement of LBP of the candidate variables at 1 month and 1 year after the cervical laminoplasty. The variables with values of p<0.001 were identified after the multivariable logistic regression for the chosen variables using the stepwise method.
Results : Cervical JOA score significantly improved from 12.2±4.0 preoperative to 13.6±3.4 (p=0.03) at 1 month postoperative and to 14.4±3.0 (p<0.001) at 1 year postoperative. Clinical improvements were seen in JOA BPEQ scores and ODI but not in JOA CMEQ scores or NDI. VAS of LBP showed significant improvement from 56.8±18.9 preoperative to 34.0±30.6 (p<0.001) at 1 month postoperative and 42.2±26.5 (p=0.002) at 1 year postoperative.
Multivariable logistic regression analysis following a forward stepwise logistic regression revealed the factors for the improvement rate of VAS scores for LBP after cervical laminoplasty. The factors at 1 month postoperative were preoperative JOA BPEQ score for walking ability (B=1.2, t=4.5), no lumbar spondylosis (B=51.7, t=4.0), and VAS scores for LBP (B=1.4, t=3.7). The factors at 1 year postoperative were preoperative no lumbar spondylosis (B=79.3, t=6.8), JOA CMEQ QOL scores (B=2.0, t=4.1), JOA BPEQ social life function scores (B=−1.6, t=−3.9), pain or numbness from chest to toe (B=−0.74, t=−3.8), and cervical JOA III scores (B=−25.7, t=−3.6).
Conclusions : Preoperative clinical factors that improve LBP after cervical laminoplasty were : at 1 month postoperative, the patient has severe LBP but is ambulatory ; at 1 year postoperative, the patient’s LBP inhibits social function and reduces bladder function, but the psychological quality of life is maintained and there is less pain and numbness from chest to legs ; and factors that improve LBP throughout the year were no complications of lumbar spine lesions.
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