Orthopedics

Feature Article 

Surgical Outcomes in Selective Laminectomy and Conventional Double-Door Laminoplasty for Cervical Spondylotic Myelopathy

Toshitaka Yoshii, MD, PhD; Shoji Tomizawa, MD, PhD; Takashi Hirai, MD, PhD; Hiroyuki Inose, MD, PhD; Tsuyoshi Yamada, MD; Kenichiro Sakai, MD, PhD; Shuta Ushio, MD; Satoru Egawa, MD; Masato Yuasa, MD, PhD; Tsuyoshi Kato, MD, PhD; Shigenori Kawabata, MD, PhD; Yoshiyasu Arai, MD, PhD; Atsushi Okawa, MD, PhD

Abstract

Several postoperative problems have been reported in conventional cervical laminoplasty (C-LAMP), such as loss of cervical curvature, sagittal imbalance, and loss of range of motion (ROM). Selective laminectomy (S-LAM) is a less invasive procedure that may prevent the problems associated with conventional C-LAMP. In this study, the authors prospectively compared neurological outcomes and radiological parameters in C-LAMP and S-LAM for the treatment of cervical spondylotic myelopathy. Fifty-three patients were enrolled, with 25 patients receiving conventional double-door C-LAMP and 28 patients receiving S-LAM. Measured outcomes included operative time, intraoperative blood loss, Japanese Orthopaedic Association score for neurological recovery, cervical sagittal alignment at C2-7, cervical sagittal vertical axis from occiput to C7, C7 slope, and cervical ROM at C2-7. No difference was found in operative time, whereas intraoperative blood loss was significantly less in the S-LAM group (P<.05). No significant difference in neurological recovery was found between the 2 groups. The postoperative C2-7 angle was significantly smaller (P<.05) and cervical sagittal vertical axis greater (P<.01) in the C-LAMP group. Postoperative ROM at C2-7 was greater (P<.01) in the S-LAM group. In the CLAMP group, postoperative kyphotic change was greater in patients with high C7 slope. However, in the S-LAM group, postoperative sagittal alignment was preserved even in patients with high C7 slope. Postoperative cervical alignment, sagittal balance, and cervical ROM were better preserved in the S-LAM group compared with the C-LAMP group. Selective laminectomy is an effective, minimally invasive method for cervical spondylotic myelopathy with spinal cord compression at limited levels. [Orthopedics. 2020;43(4);e311–e315.]

Abstract

Several postoperative problems have been reported in conventional cervical laminoplasty (C-LAMP), such as loss of cervical curvature, sagittal imbalance, and loss of range of motion (ROM). Selective laminectomy (S-LAM) is a less invasive procedure that may prevent the problems associated with conventional C-LAMP. In this study, the authors prospectively compared neurological outcomes and radiological parameters in C-LAMP and S-LAM for the treatment of cervical spondylotic myelopathy. Fifty-three patients were enrolled, with 25 patients receiving conventional double-door C-LAMP and 28 patients receiving S-LAM. Measured outcomes included operative time, intraoperative blood loss, Japanese Orthopaedic Association score for neurological recovery, cervical sagittal alignment at C2-7, cervical sagittal vertical axis from occiput to C7, C7 slope, and cervical ROM at C2-7. No difference was found in operative time, whereas intraoperative blood loss was significantly less in the S-LAM group (P<.05). No significant difference in neurological recovery was found between the 2 groups. The postoperative C2-7 angle was significantly smaller (P<.05) and cervical sagittal vertical axis greater (P<.01) in the C-LAMP group. Postoperative ROM at C2-7 was greater (P<.01) in the S-LAM group. In the CLAMP group, postoperative kyphotic change was greater in patients with high C7 slope. However, in the S-LAM group, postoperative sagittal alignment was preserved even in patients with high C7 slope. Postoperative cervical alignment, sagittal balance, and cervical ROM were better preserved in the S-LAM group compared with the C-LAMP group. Selective laminectomy is an effective, minimally invasive method for cervical spondylotic myelopathy with spinal cord compression at limited levels. [Orthopedics. 2020;43(4);e311–e315.]

Cervical laminoplasty (C-LAMP) has been commonly performed for the treatment of patients with cervical spondylotic myelopathy (CSM). Previous studies have reported that CLAMP generally provides sufficient decompression and satisfactory outcomes to patients with CSM.1 However, despite its favorable effect on neurological recovery, there are several postoperative problems, such as loss of cervical curvature and loss of range of motion (ROM),2,3 because of operative damage to the posterior neck extensor muscles.4,5 To avoid these complications, several studies have investigated the effectiveness of procedures that are less invasive to the posterior neck muscles.6–8

Posterior C-LAMP has been traditionally applied for patients with CSM with a long range of decompression (ie, C3-6, C3-7),1 whereas selective laminectomy (S-LAM) only decompresses compressive lesions of the spinal cord.8–10 Selective laminectomy is reported to be less invasive to the posterior extensor muscles, which may prevent the problems associated with conventional C-LAMP. However, to the current authors' knowledge, there have been no prospective studies comparing these 2 procedures. Therefore, they conducted a prospective comparative study evaluating surgical outcomes in conventional C-LAMP and S-LAM at an average follow-up of 5 years.

Materials and Methods

Patients

This was a prospective, single-institution study comparing 2 surgical procedures for the treatment of CSM. The study was approved by the institutional ethics committee. Since 2007, 53 patients were prospectively enrolled in this study. The selection of surgical procedure was quasi-randomized based on patient identification number (odd: S-LAM, even: CLAMP): 28 patients received S-LAM and 25 patients received conventional double-door C-LAMP (Figure 1). In the S-LAM group, single laminectomy was performed in 22 patients and double laminectomy was performed in 6 patients. In the CLAMP group, 10 patients received C3-6 laminoplasty and 15 patients received C3-7 laminoplasty. The inclusion criteria were patients with CSM who required surgical decompression. Patients with myelopathy caused by cervical disk herniation, ossification of the posterior longitudinal ligament and apparent spinal cord compression at 3 levels or more, radiculopathy, and a history of previous cervical spine surgery or injury were excluded. Patients who had kyphotic alignment (C2-7 angle less than −5°) were excluded.

Postoperative magnetic resonance images of selective laminectomy (A) and conventional cervical laminoplasty (B).

Figure 1:

Postoperative magnetic resonance images of selective laminectomy (A) and conventional cervical laminoplasty (B).

Operative Procedure

Selective laminectomy was performed only for the levels where the spinal cord was clearly compressed and deformed and the compressed legion caused neurological symptoms. After making a skin incision and longitudinally dividing the nuchal ligament, the spinous process was split and gently retracted to the lateral sides with the attached paravertebral muscles. Then, decompression was performed using a diamond burr under microscope. The authors usually decompressed the upper laminae and cephalad and half of the lower laminae for 1-level stenosis. For example, for a C4/5 one-level spinal cord compression, they fenestrated the C4 laminae and the upper part of the C5 laminae. In the case of a C4/5 and 5/6 two-level spinal cord compression, they fenestrated the C4 and C5 laminae and the upper part of the C6 laminae. The muscles attached to the spinous processes where they did not decompress were completely preserved.

Double-door C-LAMP without lamina spacers was performed as described by Miyazaki and Kirita.11 The current authors decompressed all the levels at C3-6 or C3-7, including the levels with mild stenosis. In C3-7 C-LAMP, the inferior lamina at C3 and superior lamina at C7 were fenestrated, the laminae at C4-6 were split at the mid-line, and bilateral gutters were fashioned using a high-speed air-burr drill. The bilateral laminae were kept open by anchor sutures to the capsule of the facet joint. The C2 and C7 spinous processes and the paravertebral muscles that were attached to these spinous processes were generally preserved to the extent possible.

Evaluation

Clinical Outcomes. The patients were followed for an average of 5.1 years. The Japanese Orthopaedic Association (JOA) scoring system was used to evaluate cervical myelopathy before and after surgery. The recovery rate was calculated using the method of Hirabayashi et al.12

Radiological Evaluation. Cervical sagittal alignment (C2-7 lordotic angle) was measured by the Cobb method using a lateral radiograph in a neutral position. The cervical spine ROM at C2-7 was calculated from a radiograph in flexion and extension. Because the T1 slope was sometimes difficult to visualize on the lateral radiograph, the C7 slope was measured. As an index of cervical sagittal balance, the authors used the center of gravity of the head (CGH)-C7 sagittal vertical axis (SVA), which is the distance between the anterior margins of the external auditory canal plumb line and the posterior-cranial corner of the C7 vertebra body, as a cervical SVA.

Statistical Analysis

Chi-square test was used for categorical data, and unpaired t test was used for continuous data to compare the C-LAMP and S-LAM groups. SPSS Statistics version 22 software (IBM, Armonk, New York) was used. The power analysis of the change in cervical alignment in the 10 early cases revealed that a sample size of 25 per group was needed to achieve a power of 80% (alpha=0.05). P<.05 was considered significant.

Results

There were no differences between the 2 groups regarding age, sex, preoperative JOA score, cervical sagittal alignment, cervical SVA, C7 slope, cervical ROM, and follow-up period (Table 1). No difference was found in operative time between the 2 groups. However, intraoperative blood loss was significantly less in the SLAM group compared with the C-LAMP group (P<.05) (Figure 2).

Baseline Characteristicsa

Table 1:

Baseline Characteristics

Pre- and postoperative Japanese Orthopaedic Association (JOA) scores in selective laminectomy (S-LAM) and conventional cervical laminoplasty (C-LAMP) (A). Improvement rates of JOA scores in S-LAM and C-LAMP. Abbreviation: N.S., no significant difference (B).

Figure 2:

Pre- and postoperative Japanese Orthopaedic Association (JOA) scores in selective laminectomy (S-LAM) and conventional cervical laminoplasty (C-LAMP) (A). Improvement rates of JOA scores in S-LAM and C-LAMP. Abbreviation: N.S., no significant difference (B).

Both groups demonstrated a favorable improvement in JOA scores after surgery (Figure 3A). There was no significant difference in the neurological recovery rate between the 2 groups (Figure 3B). Regarding radiographic measurements, the postoperative C2-7 angle was significantly smaller in the C-LAMP group at final follow-up (P<.05) compared with the S-LAM group (Figure 4A). Similarly, the postoperative ROM at C2-7 was greater in the S-LAM group (P<.01) at final follow-up (Figure 4B). Interestingly, in the C-LAMP group, the postoperative kyphotic change at C2-7 was correlated with the preoperative C7 slope. The postoperative kyphotic change was greater in the high C7 slope group (≥25°) than in the low C7 slope group (<25°). However, in the S-LAM group, sagittal alignment was well preserved even in patients with high preoperative C7 slope (Figure 4C). There were no differences in C7 slope postoperatively between the 2 groups (Figure 5A). However, the postoperative cervical SVA was significantly greater in the C-LAMP group than in the S-LAM group (P<.01) (Figure 5B).

Operative time (A) and intraoperative blood loss (B) in selective laminectomy (S-LAM) and conventional cervical laminoplasty (C-LAMP). Abbreviation: N.S., no significant difference. *P<.05.

Figure 3:

Operative time (A) and intraoperative blood loss (B) in selective laminectomy (S-LAM) and conventional cervical laminoplasty (C-LAMP). Abbreviation: N.S., no significant difference. *P<.05.

Pre- and postoperative C2-7 angle (A) and range of motion (ROM) (B) in selective laminectomy (S-LAM) and conventional cervical laminoplasty (CLAMP). Postoperative decrease in C2-7 angle in patients with high C7 slope (≥25°) and low C7 slope (<25°) (C). *P<.05. **P<.01.

Figure 4:

Pre- and postoperative C2-7 angle (A) and range of motion (ROM) (B) in selective laminectomy (S-LAM) and conventional cervical laminoplasty (CLAMP). Postoperative decrease in C2-7 angle in patients with high C7 slope (≥25°) and low C7 slope (<25°) (C). *P<.05. **P<.01.

Pre- and postoperative C7 slope (A) and cervical sagittal vertical axis (B) in selective laminectomy (S-LAM) and conventional cervical laminoplasty (C-LAMP). **P<.01. ***P<.001.

Figure 5:

Pre- and postoperative C7 slope (A) and cervical sagittal vertical axis (B) in selective laminectomy (S-LAM) and conventional cervical laminoplasty (C-LAMP). **P<.01. ***P<.001.

Postoperatively, there was 1 C5 palsy and 1 colonic diverticulitis observed in the C-LAMP group and 1 cholecystitis observed in the S-LAM group. During follow-up, neurological deterioration was observed in 1 patient in the C-LAMP group and 1 patient in the S-LAM group. However, no patient underwent revision surgery during the follow-up period.

Discussion

Conventional C-LAMP uniformly decompresses the consecutive laminae in a long range. The procedure is effective for multilevel cervical stenosis, but the surgical damage to the paraspinal muscles is relatively high. Several adverse outcomes after laminoplasty are recognized, such as kyphotic deformity, loss of ROM, and segmental motor paralysis. These complications are partly caused by the damage to the muscles by the surgical procedure, and thus may be avoided by reducing the surgical invasion to the paraspinal muscles.9

Decompression at the selective levels may lead to less surgical damage to the muscle, resulting in fewer complications compared with conventional laminoplasty. To provide support for this hypothesis, the authors prospectively compared surgical outcomes of C-LAMP and S-LAM in patients with CSM.

From the results of this study, the postoperative kyphotic change was reduced in the S-LAM procedure compared with the C-LAMP procedure. Previous studies showed that kyphosis can develop after C-LAMP in 6% to 35% of patients.13–15 Several authors reported that invasion to the extensor muscles, especially the muscles attached to C2 and C7, was associated with postoperative kyphosis.16 Other studies showed that not only the muscles attached to the C2 and C7 but also other extensor muscles are important for maintaining cervical alignment.17 Consistent with previous reports, the current study demonstrated the importance of reducing the damage to the extensor muscles to reduce the loss of lordosis after posterior decompression.

A previous study reported that T1 slope is a risk factor for kyphotic alignment changes after laminoplasty.18 Those authors concluded that patients with high T1 slope require great energy expenditure to maintain horizontal gaze and that these patients are more likely to show loss of lordosis after laminoplasty because of the damage to the extensor muscle. Similarly, the current study showed that patients with high C7 slope tended to lose lordosis of the cervical spine after C-LAMP. However, S-LAM did not cause postoperative kyphotic change, even in patients with high C7 slope. Nori et al10 also reported that patients with high C7 slope did not show postoperative kyphosis after SLAM. In addition to the alignment of the cervical spine, postoperative cervical sagittal balance evaluated by occipito (Oc)-C7 SVA was better in the S-LAM group. Because cervical balance is reported to be associated with patients' quality of life,19 maintaining it is key to improving the results of posterior cervical surgery for CSM.

Another problem related to C-LAMP is the decrease in ROM after surgery.20,21 This decrease is reported to range from 17% to 80% of preoperative ROM.13 Some authors have reported a relationship between postoperative ROM and muscle condition after C-LAMP.22 Further, Takeuchi et al21 reported that modified surgical techniques preserving paraspinal muscles in C-LAMP maintained cervical ROM after surgery. The current study also showed that the S-LAM procedure reduced surgical invasion to the deep extensor muscles and reduced loss of ROM after surgery. Other techniques using decompression for selective laminae have also showed favorable results in neck ROM postoperatively.23 Another possible factor that can cause loss of ROM after C-LAMP is spontaneous fusion of opened laminae.20 Selective laminectomy also has merit at this point because the laminae are usually removed in this procedure. Because cervical ROM is associated with patients' quality of life,24 reducing damage to the muscles using S-LAM is important for improving postoperative outcomes.

This study had the following limitations: (1) The selection of surgical method was not completely randomized; (2) the number of patients included was relatively limited; (3) the authors did not include patients with kyphotic alignment; (4) the authors evaluated neurofunctional scores but not patients' reported outcomes; and (5) the authors compared 1-2–level S-LAM with 3-4–level C-LAMP. Because the 2 procedures are different in size/scope, the results of this study should be carefully interpreted. Comparing S-LAM with conventional wide-range laminoplasty would be more appropriate to show the efficacy of selective decompression. However, laminoplasty generally needs to detach more muscles compared with the microscopic laminectomy technique. Because the purpose of selective decompression is to reduce the invasion to the paravertebral muscles, the authors applied S-LAM while preserving muscles as much as possible. Despite these limitations, to the authors' knowledge this is the first study to prospectively compare the surgical outcomes of S-LAM and C-LAMP, finding that S-LAM reduces complications related to conventional C-LAMP, such as postoperative kyphotic change, sagittal imbalance, and loss of ROM, without decreasing neurological improvement.

Conclusion

In this study, S-LAM showed neurological recovery equivalent to that of conventional C-LAMP with reduced intraoperative blood loss. Importantly, postoperative cervical alignment, sagittal balance, and cervical ROM were better preserved in the S-LAM group compared with the C-LAMP group. On the basis of the results of this study, S-LAM is an effective, minimally invasive procedure for patients with spinal cord compression at limited levels.

References

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Baseline Characteristicsa

CharacteristicCervical Laminoplasty (n=25)Selective Laminectomy (n=28)
Age, mean±SD, y67.7±9.563.9±10.8
Sex, male/female, No.17/820/8
Preoperative JOA score, mean±SD9.8±3.110.2±2.7
Preoperative C2-7 angle, mean±SD17.2°±9.4°26.4°±10.3°
Preoperative C2-7 flexion, mean±SD−10.9°±15.0°−8.0°±13.1°
Preoperative C2-7 extension, mean±SD24.7°±10.4°26.4°±10.3°
Preoperative C2-7 ROM, mean±SD35.6°±12.4°34.3°±12.5°
Cervical SVA, mean±SD, mm16.2±14.610.7±21.9
Preoperative C7 slope, mean±SD, mm5.1±2.35.0±2.3
Follow-up, mean±SD, y5.1±2.35.0±2.3
Authors

The authors are from the Department of Orthopaedic Surgery, Graduate School, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Toshitaka Yoshii, MD, PhD, Department of Orthopaedic Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyoku, Tokyo, 113-8519, Japan ( yoshii.orth@tmd.ac.jp).

Received: January 24, 2019
Accepted: May 06, 2019
Posted Online: June 05, 2020

10.3928/01477447-20200521-06

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