The Effect of Laminectomy with Instrumented Fusion Carried into the Thoracic Spine on the Sagittal Imbalance in Patients with Multilevel Ossification of the Posterior Longitudinal Ligament

Abstract

Objective To determine if there is a difference in either the cervical alignment or the clinical outcomes in cervical ossification of the posterior longitudinal ligament (OPLL) patients who underwent laminectomy with instrumented fusion (LIF) ending at C6, C7, or proximal thoracic spine for the treatment of multilevel OPLL, and to find out the appropriate distal fusion level. Methods This was a single‐center retrospective study. In total, 36 patients with cervical OPLL who underwent three or more level LIF in our institution between January 2015 and January 2017 were enrolled. They were divided into three groups according to their distal ends: C6 (nine females and 11 males, 60.45 ± 9.68 years old), C7 (four females and six males, 61.60 ± 10.29 years old), and T‐group (two females and four males, 64.33 ± 8.12 years old). Radiographic (compression level, classification of OPLL, occupying rate, C2‐7 cobb angle, C2‐7 sagittal vertical axis, and fusion level) and clinical outcomes (NDI score, operative time, and blood loss) were compared. Predictors of postoperative sagittal imbalance were also identified according to if the postoperative C2‐7 SVA was greater than 40 mm. The sensitivity and specificity of preoperative parameters predicting postoperative cervical stability were evaluated via the receiver operating characteristic (ROC) curve. Results All patients were followed up at least 1 year. The blood loss in T group was significantly more than C6 or C7 group. The length of fusion level became significantly longer when the caudal level extended to the thoracic spine. The age, preoperative SVA, and NDI score at follow‐up were significantly greater in the imbalance group. At the final follow‐up, the cervical lordosis tended to be straight and the C2‐7 SVA tended to be greater when the caudal level of fusion was extended to upper thoracic segment. Further ROC curve analysis suggested that patients’ age had a sensitivity of 75.00%, specificity of 79.17% for cervical stability, and the AUC was 0.844 (P 67 years) with great preoperative SVA (>30 mm), terminating at C6 was recommended to limit the invasion of cervical extensor muscles, provided the decompression was adequate.

Keywords

• Cervical sagittal imbalance
• Cervicothoracic junction
• Laminectomy with instrumented fusion
• Ossification of the posterior longitudinal ligament