K-Line Tilt May Influence the Short-Term Surgical Outcomes After Laminoplasty in Patients With Degenerative Cervical Myelopathy

Abstract

Study DesignA retrospective study.ObjectivesTo explore the relationship between K-line tilt and short-term surgical outcomes following laminoplasty in patients with multilevel degenerative cervical myelopathy (DCM), and to evaluate the potential of K-line tilt as a reliable preoperative predictor.MethodsA retrospective analysis was performed for 125 consecutive patients who underwent laminoplasty for multilevel DCM. The radiographic parameters utilized in this study encompassed T1 slope (T1S), C2-C7 lordosis (CL), C2-C7 sagittal vertical axis (cSVA), T1 slope minus C2-C7 lordosis (T1S-CL), C2-C7 range of motion (ROM), and K-line tilt. The neurological recovery was evaluated using the Japanese Orthopaedic Association (JOA) score. Pearson correlation coefficients were calculated to assess the relationship between K-line tilt and other classical cervical parameters. Logistic regression analysis was employed to examine the association between K-line tilt and surgical outcomes.ResultsOf the 125 patients, 89 were men. The mean age of the patients was 61.74 ± 11.31 years. The results indicated a correlation between the K-line tilt and the cSVA (r = 0.628, P < 0.001), T1S (r = 0.259, P = 0.004), and T1S-CL (r = 0.307, P < 0.001). The K-line tilt showed an association with the failure of the JOA recovery rate (RR) to reach the minimal clinically important difference (MCID) and the occurrence of postoperative kyphotic deformity. We identified cutoff values for the K-line tilt which predict the failure of the JOA RR to reach the MCID and postoperative kyphotic deformity as 10.13° and 9.93°, respectively.ConclusionsThe K-line tilt is an independent preoperative risk factor associated with both the failure of the JOA RR to reach the MCID and the occurrence of postoperative kyphotic deformity in patients with multilevel DCM after laminoplasty.

Keywords: K-line tilt; laminoplasty; multilevel degenerative cervical myelopathy; short-term surgical outcomes.

Figure 1.

K-line tilt (A), cSVA (B), T1S (C), and CL (D) were measured in the neutral position. Flex CL (E) and Ext CL (F) were measured with the patient in maximal flexion and extension, respectively. cSVA, C2-C7 sagittal vertical axis; T1S, T1 slope; CL, C2-C7 cervical lordosis; Ext CL, CL in extension; Flex CL, CL in flexion.

Figure 2.

ROC curve analysis to predict postoperative kyphotic deformity. The cutoff value for K-line tilt was 10.13° (area under the curve = 0.768, P = 0.002), with a sensitivity of 75.0% and a specificity of 85.0%. ROC, receiver operating characteristic.

Figure 3.

ROC curve analysis to predict JOA RR < 52.8%. The cutoff value for K-line tilt was 9.93° (area under the curve = 0.813, P < 0.001), with a sensitivity of 56.8% and a specificity of 89.8%. The combined use of multiple preoperative indicators, including age, K-line tilt, and CL, demonstrated greater accuracy in predicting the likelihood of JOA RR<52.8%, compared to using the K-line tilt alone (AUC: 0.882 vs 0.813). ROC, receiver operating characteristic; JOA, Japanese Orthopaedic Association; RR, recovery rate; CL, C2-C7 lordosis.