Introduction: Recently, cervical sagittal balance has received increased attention as an important determinant of radiological and clinical outcomes after surgery. However, little is known about the precise impact of cervical sagittal balance on surgical outcomes, especially for patients with cervical myelopathy caused by ossification of the posterior longitudinal ligament (OPLL). We retrospectively investigated the surgical outcomes of cervical myelopathy caused by OPLL with special attention to the concept of the cervical sagittal balance.
Materials and Methods: The study included a total of 97 consecutive patients (78 male, 19 female; mean age 64.3 years) who underwent surgery for cervical myelopathy caused by OPLL at our hospital from 2008 and completed at least 1‐year of follow‐up. The average follow‐up period was 3.1 years. We selected surgical procedures as follows: (1) For patients with massive OPLL or preoperative kyphotic cervical alignment, we performed anterior decompression and fusion with floating method (ADF) as the 1st choice, and posterior decompression and fusion (PDF) as the 2nd choice. (2) For patients with slight OPLL and normal cervical alignment, we performed laminoplasty (LAMP). ADF was performed in 39 cases, PDF in 18 cases and LAMP in 40 cases. Cervical lateral x‐ray images taken in the neutral standing position were evaluated preoperatively and at the final follow‐up visit. Radiographic measurements included the following: (1) CSVA, which was measured as the distance between a plumb line dropped from the anterior margin of the external auditory canal and the posterior‐cranial corner of the C7 vertebral body, (2) CL (C2–7 lordotic angle) and (3) C7 slope. Clinical results were evaluated using the Japanese Orthopedic Association scoring system for cervical myelopathy (C‐JOA score). We divided patients into two groups based on the preoperative CSVA: the Balance (CSVA <40 mm) and Imbalance (CSVA ≥40 mm) groups.
Results: Sixty‐nine patients were in the Balance group, and 28 patients were in the Imbalance group. In the Balance group, none of the three operations had an effect on the CL. In contrast, in the Imbalance group, while ADF and PDF had no effect on the CL, LAMP worsened the CL postoperatively (Figure 1). None of three operations had an effect on the C7 slope in either group. The recovery rates of the C‐JOA scores in the Balance group showed no significant differences among the three operations; however in the Imbalance group, LAMP resulted in worse recovery rate of the C‐JOA score than ADF or PDF (Figure 2). In 7 cases where LAMP was performed in the Imbalance group, postoperative cervical kyphosis was observed in 4 cases (57.1%), and recurrence of myelopathy was observed in 3 cases (42.9%).
Conclusion: LAMP is not suitable for patients with cervical myelopathy caused by OPLL who have cervical sagittal imbalance, even in cases with normal preoperative alignment and slight OPLL.