Comparison between Radiological and Clinical Outcomes of Laminoplasties with Titanium Miniplates for Cervical Myelopathy

Abstract

Background: Laminoplasty is a surgical procedure frequently performed for cervical myelopathy. We investigated correlations between changes in the anteroposterior diameter (APD) of the spinal canal, spinal canal area (SCA), and laminar angle (LA) and clinical outcomes of laminoplasty.

Methods: Of the 204 cervical myelopathy patients who underwent laminoplasty from July 2010 to May 2015, 49 patients who were evaluated with pre- and postoperative computed tomography of the cervical vertebrae were included. The average age of the patients was 60.4 years (range, 31 to 82 years), and the average duration of follow-up was 31.6 months (range, 9 to 68 months). Changes in the APD and SCA were measured at the middle of the vertebral body. Changes in LA were measured where both pedicles were clearly visible. Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) score and visual analog scale score for pain preoperatively (1 day before surgery) and postoperatively (last outpatient visit) and examining postoperative complications.

Results: The APD showed an average of 54.7% increase from 11.5 to 17.8 mm. The SCA showed an average of 57.7% increase from 225.9 to 356.3 mm². The LA increased from 34.2° preoperatively to 71.9° postoperatively. The JOA score increased from an average of 9.1 preoperatively to 13.4 postoperatively. Three patients were found to have hinge fractures during surgery. Postoperative complications, including two cases of C5 palsy, were recorded. The correlation coefficient between the LA change and JOA score improvement was -0.449 (p < 0.05). Patients with a < 33° (25%) increase in the LA showed the most significant clinical improvement.

Conclusions: Patients with a < 33° (25%) change in the LA after laminoplasty with a titanium miniplate showed the most significant clinical improvement. Thus, LA changes can be useful in predicting the clinical outcome of laminoplasty.

Keywords: Laminar angle; Laminoplasty; Myelopathy.

Fig. 1. Postoperative computed tomography (CT) of a 61-year-old male patient who underwent cervical laminoplasty. Each cross-section of the CT image is parallel to the lower surface of the corresponding vertebral body.

Fig. 2. The anteroposterior diameter (APD) of the spinal canal and the spinal canal area (SCA) were measured in the axial plane at the middle of the vertebral body on the sagittal computed tomography (CT) scan using the polygonal region of interest (ROI) tool of Picture Archiving and Communication System (PACS) preoperatively (A-C) and postoperatively (D-F).

Fig. 3. Measurements of the laminar angle created by one line passing posterior to the transverse foramen and the other line traversing along the inside edge of the lamina on the preoperative (A, B) and postoperative (C, D) computed tomography scans. The difference between the preoperative angle (a) and the postoperative angle (b) was recorded.

Fig. 4. One way ANOVA analysis of Japanese Orthopedic Association (JOA) recovery rate and ΔLA (changes in laminar angle). The patients were divided into 4 groups based on the ΔLA percentile (group A, < 25%; B, ≥ 25% & < 50%; C, ≥ 50% & < 75%; D, ≥ 75%). Group A showed a significant improvement in JOA score compared to the other groups (^*p < 0.05) (N = 49, F = 11.622).