記住我
Click on image for details.
ORIGINAL ARTICLE
Year : 2023 | Volume
: 71
| Issue : 4 | Page : 689-692
Comparison of the Degree of Expanded Spinal Canal Area between the Hinge-Side Area and the Open-Side Area in Cervical Open-Door Laminoplasty
Kazuma Doi1, Junichi Mizuno1, Yukoh Ohara2, Satoshi Tani1
1 Center for Minimally Invasive Spinal Surgery, Shin Yurigaoka General Hospital, Kawasaki, Kanagawa, Japan
2 Center for Minimally Invasive Spinal Surgery, Shin Yurigaoka General Hospital, Kawasaki, Kanagawa; Department of Neurosurgery, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan
Correspondence Address:
Kazuma Doi
255 Furusawatsuko, Asao, Kawasaki, Kanagawa, 215-0026
Japan
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/0028-3886.383874
Background: There have been reports on the significant canal cross-sectional area (CSA) expansion difference between pre- and post-operation, but no comparison of CSA expansion between the hinge-side area (Area H) and the open-side area (Area O) has been reported. This study aimed to measure the spinal CSA expansion between Area H and Area O retrospectively after open-door laminoplasty using new titanium spacers and evaluated this common decompression procedure's effectiveness.
Materials and Methods: This study included 27 patients diagnosed with cervical spondylotic radiculopathy or myelopathy, ossification of the posterior longitudinal ligament, and developmental canal stenosis from February 2021 to October 2022. The CSA difference between pre- and post-cervical laminoplasty (C4–C6 levels) was measured with cervical transverse computed tomography scan images. The CSA difference in Area H and Area O between pre- and post-laminoplasty was similarly calculated.
Results: The spinal canal areas of each segment after open-door laminoplasty were significantly enlarged (P < 0.05). Area O was also significantly enlarged compared to that of Area H (P < 0.05).
Conclusion: Area O was more enlarged than Area H, and both sides were statistically enlarged after open-door laminoplasty.
Keywords: Hinge, laminoplasty, open door, spinal canal area, titanium spacer
Key Message: There have been reports on the significant cross-sectional areas (CSA) expansion difference between pre-and post-operation, but no comparison of CSA expansion comparison between the hinge-side area (Area H) and the open-side area (Area O) has been reported. CSA of each segment was significantly enlarged after open-door laminoplasty with new titanium spacers. Moreover, Area O was significantly more enlarged than Area H.
A single open-door cervical laminoplasty with internal fixation was proposed by Hirabayashi et al.[1] in 1983. Since then, this procedure has been developed with some modifications for cervical spondylotic myelopathy (CSM), disk herniation, and ossification of the posterior longitudinal ligament (OPLL). A new titanium spacer (Laminoplasty Basket; Ammtec Co., Suginami-ku, Tokyo, Japan) was designed by Tani et al.[2] in 2010. This implant had the advantage of obtaining bone fusion and achieved good clinical outcomes and safety.[3] This titanium spacer was modified twice in the last 10 years, and a newly designed spacer (Laminoplasty Basket 3; Ammtec Co., Japan) was applied. Basket 3 allowed it to keep the distance from the dura mater and enlarge the spinal canal area wider by bending the middle of the spacer 140°, unlike the previous spacers.
There have been several studies reporting that there was a significant difference in the spinal canal cross-sectional area (CSA) between pre- and post-operation for open-door laminoplasty, but there was no comparison of CSA expansion between the hinge-side area (Area H) and the open-side area (Area O). This study aimed to measure CSA expansion between the hinge-side area (Area H) and the open-side area (Area O) retrospectively in patients who underwent open-door laminoplasty using new titanium spacers and evaluate this common decompression procedure's effectiveness.
Materials and Methods
Study population
This is a retrospective review of 33 adult patients who underwent open-door cervical laminoplasty for CSM, OPLL, cervical spondylotic radiculopathy (CSR), and developmental canal stenosis in our institution from February 2021 to October 2022. The new titanium spacer (Laminoplasty Basket 3) was applied in all patients. Infection, tumor, demyelinating disease, trauma accompanied by cervical fracture, great instability, and revision surgery cases were excluded. Finally, 27 patients (19 males and eight females) were enrolled in this study. These patients were aged between 36 and 85 years, with a mean age of 66.63 ± 12.85 years. This study included 18 CSM cases, six OPLL cases, two CSR cases, and one developmental canal stenosis case. The levels that caused perioperative hinge fracture and were repaired with the titanium devices (Lamina-aid; Ammtec Co., Japan) were excluded. Each procedure was performed between the C3 and C7 levels, but the operation levels were different individually based on the clinical and radiographical findings. The C3 and C7 levels were not analyzed because of the small number. Thus, only the C4 laminas (22 cases), C5 laminas (24 cases), and C6 laminas (23 cases) with radiologically well-performed laminoplasty were included in this study. The requirement for informed consent from individual patients was waived due to the retrospective design and minimal risk to participants in this study.
Surgical technique
The surgical procedures were performed similarly by several operators as follows. Under general anesthesia, the patient was prepped in the prone position with motor-evoked potential monitoring. The nuchal fascia and paravertebral muscles were dissected, and the spinal processes were partially removed or amputated horizontally after a midline skin incision. Bilateral laminae were exposed according to the levels that were scheduled to perform laminoplasty, and the gutter was made just medial to the lateral mass in the open side by drilling with a 3-mm diamond burr. Ligamentum flavum was partially resected to the elevated lamina. In our institution, the left side is the open side, except in patients whose symptoms are more intense on the right side. The outer cortical bone of the contralateral lamina (hinge side) was drilled out. After laminar elevation, an appropriate-sized spacer with cages (Basket 3; 8, 10, or 12 mm) [Figure 1] filled with bone grafts was applied between the elevated lamina and the lateral mass. This spacer was fixed with one 5-mm-long mini-screw into the lateral mass and one or two 4-mm-long mini-screws into the elevated lamina through the plate. Additional dome-shaped laminectomy was done if needed. Only one case was simultaneously performed with unilateral foraminoplasty in addition to the laminoplasty procedure because the patient presented with CSM and radiculopathy. The amplitude of motor-evoked potential used as the intraoperative monitoring was checked to ensure that it had not dropped at the last of an operation compared to preoperative values. A drainage tube was placed over the spacers after completing homeostasis. A layer-by-layer reconstruction for each muscle and subcutaneous tissue was done. The spinal processes were amputated horizontally and reapproximated in the midline. All patients received a soft cervical collar during the first week postoperatively. Most patients improved with more than “fair outcomes” postoperatively using the Odom criteria. There were no implant-related complications. No serious complications happened, except for one case of postoperative C5 palsy, and the symptom recovered 1 month later.
Figure 1: Basket 3 system images. (a) Basket 3 implant (b) Model of open-door laminoplasty using the new titanium spacerRadiographic data measurements
Computed tomography (CT) images acquired with Picture Archiving and Communication System (ShadeQuest/Serv; FUJIFILM Medical Solutions Corporation, Minato-ku, Tokyo, Japan) were used to perform radiographic measurements in each level retrospectively. Preoperative and postoperative CT images were used with 3-mm transverse slices parallel to the vertebral body endplates. Postoperative CT was examined the next day after laminoplasty in the same condition. Each CSA was measured using the same slices between pre- and post-operation. Spondylotic spur, OPLL, and calcified disks were excluded in these areas. The inner cortex midline of the bilateral transverse foramens was defined as the vertebral body center. The “open-side” area (＊) and the “hinge-side” area (※) were determined by the midline defined above as the boundary line [Figure 2]. The hinge-sided area is called “Area H” and the open-sided area “Area O.” The overall CSA difference between pre- and post-operation in the C4–C6 levels was calculated as the primary endpoint. The increased CSA difference in Area H and Area O between pre- and post-operation was calculated in the same fashion as the secondary endpoint.
Figure 2: (a) Preoperative CT images. Overall CSA was measured as the dimension inside surrounded by a black line. The midline of the inner cortex of the bilateral transverse foramens was defined as the center of the vertebral bodies. The open-side CSA (＊) and the hinge-side CSA (※) were measured using this midline as a boundary. (b) Postoperative CT images. Measurements were similarly done. CSA = cross-sectional area, CT = computed tomographyStatistical analysis
The R version 4.1.2 software was used to perform statistical analysis of measurement data. Data was represented as the mean ± standard deviation about the mean (X ± SD). The test was evaluated with paired t-test or Wilcoxon rank sum exact test for continuous variables. A P value below 0.05 was considered statistically significant.
ResultsDifference in CSA at each level between pre- and post-operation
The preoperative overall CSA within the spinal canal for each of the C4, C5, and C6 levels was 198.38 ± 21.20, 213.19 ± 31.64, and 205.47 ± 25.97 mm2, respectively. The postoperative overall CSA was similarly found to be 310.13 ± 37.33, 331.34 ± 50.16, and 329.26 ± 41.33 mm2, respectively. The postoperative CSA was significantly enlarged (P < 0.001, respectively) in each level [Table 1].
The preoperative CSA in Area H for C4, C5, and C6 levels was found to be 96.17 ± 14.84, 105.24 ± 17.34, and 102.19 ± 16.30 mm2, respectively. The postoperative CSA in Area H was similarly found to be 136.36 ± 22.11, 152.00 ± 28.06, and 146.73 ± 26.16 mm2, respectively. The postoperative CSA in Area H was also significantly enlarged (P < 0.001, respectively) in each level [Table 2].
Difference in the expanded CSA in Area H and Area O between pre- and post-operation
The ΔH-CSA was defined as the ΔCSA in Area H, that is, [(postoperative CSA in Area H) − (preoperative CSA in Area H)]. Similarly, ΔO-CSA was defined as the ΔCSA in Area O. The ΔH-CSA for the C4, C5, and C6 levels was found to be 40.16 ± 20.24, 46.76 ± 20.82, and 44.55 ± 18.29 mm2, respectively. On the other hand, the ΔO-CSA was found as 71.58 ± 18.23, 71.39 ± 20.81, and 79.24 ± 21.04 mm2, respectively. The ΔO-CSA was significantly enlarged compared to ΔH-CSA (P < 0.001, respectively) in each level [Table 3].
Table 3: The expanded CSA difference in Area H and Area O between pre- and post-operation Discussion A meta-analysis showed that CSM open-door and double-door methods could achieve good postoperative outcomes, but the incidence of intraoperative bleeding and the postoperative axial symptom was found to be lower in the double-door group.[4] Another study found that there were almost equivalent surgical outcomes between open-door and double-door laminoplasties for cervical OPLL at 2 years postoperatively.[5] The open-door method was adopted in all cases based on these results.
The Basket system allows for the bone graft to be held in the cage, which can facilitate bone fusion.[6] It provided a high bone fusion rate in the hinge and open sides.[3],[7] Fixation with the Basket system provided higher structural properties when compared to the plate-alone fixation in an in vitro biomechanical study.[8] Thus, it has been reported that laminoplasty using the conventional Basket has good clinical outcomes and safety.[2] However, there was concern among clinicians about the conventional Basket's proximity to the dura mater. Therefore, the newly modified Basket 3 was modified to keep the distance from the dura mater and enlarge the spinal canal area more widely by bending the middle of the spacer 140°, unlike the previous spacers. Long-term results are still unknown because of the limited Basket 3 experience.
The mean overall ΔCSA was a 57.7% increase and the greatest ΔCSA was a 66.05% increase at the C6 level.[9] In our study, the increased rates were 56.9% (C4), 56.5% (C5), and 60.9% (C6), which were almost consistent with the previous study. There has been no study on whether ΔH-CSA was significantly larger than ΔO-CSA between pre- and post-operation, although it has been reported in many other devices that CSA is enlarged with a significant difference between pre- and post-operation.[9],[10],[11] Our current study demonstrated a significant CSA increase in Area O than in Area H. Moreover, postoperative CSA was significantly enlarged even in Area H.
As a limitation, the sample size in this study was small enough to make definitive results. Therefore, further clinical studies with Basket 3 will be needed to consider the association between radiologic and clinical outcomes and safety.
In conclusion, this study proved that open-door laminoplasty with Basket 3 is a radiologically effective and safe procedure.
ConclusionsThe CSA of each segment after open-door laminoplasty was significantly enlarged, and the open-side area was larger than the hinge side in open-door laminoplasty with the new titanium spacer.
Acknowledgements
The authors express their sincere gratitude to Ammtec Co. for the support in preparing [Figure 1].
Financial support and sponsorship
Nil.
Conflicts of interest
Junichi Mizuno and Satoshi Tani have “Study Investigator Funded by Sponsor” with this implant. Other authors have nothing to disclose.
References
留言 (0)