Significance of Vertebral Body Sliding Osteotomy as a Surgical Strategy for the Treatment of Cervical Ossification of the Posterior Longitudinal Ligament

Abstract

Study design: Retrospective cohort study.

Objectives: Vertebral body sliding osteotomy (VBSO) has previously been reported as a technique to decompress ossification of the posterior longitudinal ligament (OPLL) by translating the vertebral body anteriorly. This study aimed to evaluate the radiological and clinical efficacies of VBSO and clarify the surgical indications of VBSO for treating myelopathy caused by OPLL.

Methods: Ninety-seven patients with symptomatic OPLL-induced cervical myelopathy treated with VBSO or laminoplasty who were followed up for more than 2 years were retrospectively reviewed. Cervical alignment, range of motion, fusion, modified K-line (mK-line) status, and minimum interval between ossified mass and mK-line (INT_(min)), and the Japanese Orthopaedic Association (JOA) score were assessed. Patients in the VBSO group were compared with those who underwent laminoplasty.

Results: Cervical lordosis and INT_(min) significantly increased in the VBSO group. All patients in the VBSO group assessed as mK-line (-) preoperatively were assessed as mK-line (+) postoperatively. However, in the LMP group, the mK-line status changed from (+) preoperatively to (-) postoperatively in 3 patients. Final JOA score (p = 0.02) and JOA score improvement (p = 0.01) were significantly higher in the VBSO group. JOA recovery ratio (p = 0.03) and proportion of patients with a recovery rate ≥50% were significantly higher in the VBSO group (p < 0.01).

Conclusions: VBSO is an effective surgical option for OPLL-induced myelopathy, demonstrating favorable neurological recovery and lordosis restoration with low complication rates. It is best indicated for kyphotic alignment, OPLL with a high space-occupying ratio, and OPLL involving ≤3 segments.

Keywords: K-line; anterior cervical corpectomy and fusion; cervical alignment; laminoplasty; ossification of posterior longitudinal ligament; vertebral body sliding osteotomy.

Figure 1.

Flow diagram of the patient selection process. OPLL, ossification of posterior longitudinal ligament; n. number; ACDF, anterior cervical discectomy and fusion; VBSO, vertebral body sliding osteotomy; mKline, modified K-line.

Figure 2.

Radiological measurements. (A) Measurement of the canal-occupying ratio. A, Thickness of ossified mass at the level of greatest canal narrowing. B, Anteroposterior diameter of the spinal canal. (B) Modified K-line (mK-line) was defined as the line connecting the midpoints of the spinal cord at C2 and C7.

Figure 3.

Technical description of vertebral body sliding osteotomy. (A) Two lateral slits are made using a high-speed burr at the base of the uncinate process. (B) Anterior translation of the vertebral body with ossification of the posterior longitudinal ligament mass with gentle traction. (C) While holding the vertebral body in an anteriorly translated position, interbody cages are inserted. A slight distraction force was applied with a Casper pin distractor to allow control of the vertebral body position. (D) A burr is used to remove the anterior part of the translated vertebral body. (E) The anterior plate is applied for additional stability.

Figure 4.

Transition of mK-line status in vertebral body sliding osteotomy and laminoplasty. (A) Vertebral body sliding osteotomy shifted mK-line (−) status into (+) by increasing cervical lordosis and shifting the ossified mass anteriorly. (B) mK-line (+) status changed into (−) after laminoplasty due to postoperative kyphosis.

Figure 5.

Illustrative case of a 60-year-old woman who underwent vertebral body sliding osteotomy, C4, C5. (A) Preoperative lateral radiograph demonstrating kyphotic alignment. (B) At 2 years after VBSO, alignment had changed to lordosis. Translation of the vertebral body of C4 and C5 were confirmed by comparing the location of the posterior cortex of the vertebral body. (C) The mK-line status was assessed as (-) preoperatively. (D) With restoration of lordosis and anterior translation of the ossified mass, the mK-line status was assessed as (+) at 1 year after VBSO. (E) Preoperative axial CT images demonstrating canal compromise caused by OPLL with a canal-occupying ratio of 61%. (F) Successful decompression identified on an axial CT image taken at 1 year postoperatively. Solid bone union identified on coronal (G) and sagittal (H) CT images taken at 1 year postoperatively. Japanese Orthopaedic Association score improved from 12 to 16.