Correlation between preoperativemodified compression ratio/spinal cord rotation angle and prognosis of cervical spondylotic myelopathy

English Keywords:Cervical spondylotic myelopathy  Modified compression ratio  Spinal cord rotation angle  Spinal cord function recovery

English Abstract:

  【Abstract】 Objectives: The concepts of modified compression ratio(mCR) and spinal cord rotation angle (SCRA) were proposed to discuss the relationship between pre-operative morphological character of spinal cord in patients with cervical spondylotic myelopathy(CSM) and the post-operative recovery of the patients′ spinal cord function. Methods: 98 patients with CSM [62 males and 37 females, averaged 53.80±10.7 years(38-73 years)] who underwent surgery in our hospital from January 2017-June 2017 were retrospectively analyzed. According to the pre-operative axial T2* MRI, the compression ratio(CR) of spinal cord at the maximally compression level(MCL) was measured. At the same slice, the compressed spinal cord was fitted with an ellipse. The ratio of the spinal cord length along the short axis of the ellipse to the long axis of the ellipse is defined as mCR. The angle between the long axis of the fitted ellipse and the horizontal position is defined as SCRA. Using corresponding indexes at C2/3 as internal parameters, corrected morphologic indicators were obtained. The recovery rate(RR) was measured based on pre- and post-operative scores of modified Japanese Orthopedic Association(mJOA) score. Spearman correlation analysis and multivariate analysis were used to explore the relationship between morphologic indicators (e.g., corrected CR, corrected mCR, corrected SCRA)/clinical parameters（eg., age, symptom duration, and pre-operative mJOA） and prognostic indicators(post-operative mJOA score and RR). Results: The corrected CR was (58.31±16.71)%, corrected mCR was (49.11±16.17)%, corrected SCRA was 5.09%(2.29%-10.61%), symptom duration was 12.0(4.3, 36.0) months, the pre-operative mJOA score was 13.46±1.69. At 3-year follow-up post-operative mJOA score was 16.00(14.50-16.50), RR was 62.50%(33.33%-90.40%). Multivariate analysis suggested that corrected SCRA was an independent predictor for post-operative mJOA score at 3-year follow-up[standardized coefficient(std.coef)=0.25, P=0.015] and corrected mCR was independent predictor for RR(std.coef=0.21, P=0.038). Corrected CR did not correlate to post-operative mJOA scoreand RR(P>0.05). Clinical parameters wre not independent predictors for post-operative mJOA nor RR at 3-year follow-up(P>0.05). Conclusions: Corrected mCR and corrected SCRA can predicting post-operative recovery of spinal cord function in CSM. Corrected SCRA positive correlated to 3-year follow-up post-operative mJOA and corrected mCR positive correlated to RR. Corrected CR does not significantly correlate to the post-operative recovery of spinal cord function.