Study design: A retrospective study.
Objective: The aim of this study was to determine the incidence of increased segmental range of motion (ROM) after laminoplasty and to clarify whether increased ROM is associated with spondylolisthesis. Finally, we explored the effect of increased segmental ROM on clinical results.
Summary of background data: Cervical laminoplasty for cervical spondylotic myelopathy causes reduced ROM, possibly due to the unintended contracture of the facet joint or a bony union. Although it is rarely studied, ROM may also increase following laminoplasty. Thus far, there are no reports describing the correlation between increased segmental ROM and segmental spondylolisthesis after laminoplasty.
Methods: We evaluated 187 segments from 39 cervical spondylotic myelopathy patients who underwent bilateral open door laminoplasty from C2 to C7. The segmental ROM and spondylolisthesis were measured using dynamic radiographs that were obtained preoperatively and 2 years postoperatively. The Japanese Orthopedic Association (JOA) score was used for clinical evaluation. To compare the clinical results, we compared the cases with increased ROM in at least one segment with the remaining cases.
Results: Increased segmental ROM (i.e., ≥5° increase) was observed in 25 of 187 segments (13.4%) from 14 cases. There was a strong correlation between increased ROM and spondylolisthesis. A high preoperative disc height was associated with increased segmental ROM 2 years postoperation. Regardless of the correlation with spondylolisthesis, there was no statistically significant correlation between increased segmental ROM and JOA score.
Conclusion: The decrease in segmental ROM after laminoplasty was not uniform. Approximately 13.4% of all segments showed increased ROM. The preoperative disc height might influence the risk for increased segmental ROM. Furthermore, increased ROM was correlated with spondylolisthesis in the segment, though it was not correlated with clinical results.
Level of evidence: 4.