The anatomical mechanism of C5 palsy after expansive open-door laminoplasty

BACKGROUND

Postoperative C5 palsy is not an uncommon complication in patients who undergo expansive open-door laminoplasty. However, the etiology is unclear and likely multifactorial. Nerve root lesions and spinal cord lesions have been previously proposed theories.

PURPOSE

To investigate the anatomical mechanism of postoperative C5 palsy after cervical expansive open-door laminoplasty.

STUDY DESIGN

A dissection-based study of eight embalmed human cadavers.

METHODS

The anatomy was studied in eight whole cervical cadavers (three females, five males), prepared with formaldehyde, whose ages at the time of death ranged from 54 to 78 years. Dissection was performed on the intervertebral foramen and spinal canal. In the C3-C7 of the cervical vertebra, the extraforaminal ligaments and the meningovertebral ligaments were observed. The length, width, and thickness of the ligaments were measured with a Vernier caliper. After an expansive open-door laminoplasty was performed, the shape of the dural sac was changed, and displacement of the nerve root was observed. In addition, the lengths of the anterior rootlets were measured. This study has been supported by grants from Science and Technology Planning Project of Guangdong Province (CN) (Grant No. 2017B020210010) without potential conflict of interest-associated biases in the text of the paper.

RESULTS

One hundred seventy-seven extraforaminal ligaments were found to connect the spinal nerve to the surrounding structures. After an expansive open-door laminoplasty was performed, posterior distension of the dural sac and movement of the spinal cord and nerve root were found. The spinal cord was closely attached to the ligamentum flavum by meningovertebral ligaments. In addition, the length of the C5 intradural rootlets (5.81-10.59 mm) was the shortest among the vulnerable segments.

CONCLUSION

Traction on and posterior movement of the extradural roots may be the main pathologic mechanism of postoperative C5 palsy when expansive open-door laminoplasty is performed. The meningovertebral ligaments and extraforaminal ligaments might play an important role in the occurrence of postoperative C5 palsy.

CLINICAL SIGNIFICANCE

This study provides clinicians with a more detailed understanding of the anatomic structure and potential mechanism of C5 palsy. Consideration of the meningovertebral ligaments and the intervertebral foramen may provide new directions for reducing the incidence of this complication.

Factors associated with postoperative axial symptom after expansive open-door laminoplasty: retrospective study using multivariable analysis

PURPOSE

The aim of the present study was to investigate the factors associated with axial symptom using multivariable analysis.

METHODS

The authors retrospectively assessed 249 patients treated by open-door laminoplasty. The patients were classified into two groups: axial symptom and no axial symptom group. The possible factors included demographic variables (age, sex, BMI, smoking, heart disease, diabetes, preoperative neck pain, preoperative JOA scores, preoperative NDI, course of disease and pathogenesis) and surgical and radiological variables [operation time, intraoperative blood loss, collar wear time, preoperative cervical curvature, postoperative cervical curvature, T1 slope, preoperative and postoperative C2 sagittal vertical axis (C2 SVA)].

RESULTS

The prevalence of axial symptom was 34.9% (89/249). The collar wear time, preoperative and postoperative C2 SVA were risk factors for axial symptom. A cutoff value of 22.6 mm for preoperative C2 SVA and 3.5 weeks for collar wear time predicted the development of axial symptom.

CONCLUSIONS

The longer collar wear time, larger preoperative and postoperative C2 SVA were positively correlated with the higher incidence of axial symptom.

Influence of extending expansive open-door laminoplasty to C1 and C2 on cervical sagittal parameters

Background

For patients with spinal canal stenosis in the upper cervical spine who undergo C3–7 laminoplasty alone, it remains impossible to achieve full decompression due to its limited range. This study explores the extension of expansive open-door laminoplasty (EODL) to C1 and C2 for the treatment of cervical spinal stenosis of the upper cervical spine and its effects on cervical sagittal parameters.

Methods

A retrospective analysis of 33 patients presenting with symptoms of cervical spondylosis myelopathy (CSM) and ossification in the posterior longitudinal ligament (OPLL) of the upper cervical spine from February 2013 to December 2015 was performed. Furthermore, the changes in the C0–2 Cobb angle, C1–2 Cobb angle, C2–7 Cobb angle, C2–7 SVA, and T1-Slope in lateral X-rays of the cervical spine were measured before, immediately after, and 1 year after the operation. JOA and NDI scores were used to evaluate spinal cord function.

Results

The C0–2 and C1–2 Cobb angles did not significantly increase (P = 0.190 and P = 0.081), but the C2–7 Cobb angle (P = 0.001), C2–7 SVA (P < 0.001), and T1-Slope (P < 0.001) significantly increased from preoperative to 1 year postoperative. In addition, C2–7 SVA was significantly correlated with the T1-Slope (Pearson = 0.376, P < 0.001) and C0–2 Cobb angle (Pearson = 0.287, P = 0.004), and the C2–7 SVA was negatively correlated with the C2–7 Cobb angle (Pearson = − 0.295, P < 0.001). The average preoperative and postoperative JOA scores were 8.3 ± 1.6 and 14.6 ± 1.4 points, respectively, indicating in a postoperative neurological improvement rate of approximately 91.6%. The average preoperative and final follow-up NDI scores were 12.62 ± 2.34 and 7.61 ± 1.23.

Conclusions

The sagittal parameters of patients who underwent EODL extended to C1 and C2 included loss of cervical curvature, increased cervical anteversion and compensatory posterior extension of the upper cervical spine to maintain visual balance in the field of vision. However, the changes in cervical spine parameters were far less substantial than the alarm thresholds reported in previous studies. We believe that EODL extended to C1 and C2 for the treatment of patients with spinal canal stenosis in the upper cervical spine is a feasible and safe procedure with excellent outcomes.

The Use of Preoperative and Intraoperative Pavlov Ratio to Predict the Risk of Postoperative C5 Palsy after Expansive Open-Door Laminoplasty for Cervical Myelopathy

BACKGROUND

No standard preoperative preventive measure has been established to decrease the occurrence of C5 palsy after expansive open-door laminoplasty. The aim of this study is to establish a reliable measured parameter in predicting the risk of the postoperative C5 palsy.

MATERIALS AND METHODS

A total of 276 patients receiving posterior open-door laminoplasty for cervical spinal stenotic myelopathy were studied. The patients were divided into two groups according to the preoperative Pavlov ratio (Group A: Pavlov ratio <0.65 and Group B: Pavlov ratio ≥0.65). Correlations between the occurrence of postoperative C5 palsy and Pavlov ratio were analyzed, and Group A was further tested. The surgical procedures, clinical symptoms, and Pavlov ratio were described.

RESULTS

The patients with Pavlov ratio <0.65 had a higher risk of developing postoperative C5 palsy (P < 0.05, odds ratio [OR] = 2.91). No significant difference was found in gender, age, etiology, type of operation, and pre- and postoperative Japanese Orthopaedic Association scores between patients with and without postoperative C5 palsy. The cutoff (1.01) of receiver operating characteristic curve of the postoperative Pavlov ratio of the Group A was calculated. The postoperative Pavlov ratio ≥1.01 of the patients in Group A was a significant risk factor of the development of postoperative C5 palsy (P < 0.01, OR = 10.83).

CONCLUSIONS

The preoperative Pavlov ratio <0.65 at the C5 level was more likely to develop the postoperative C5 palsy. When the preoperative Pavlov ratio is <0.65, the postoperative Pavlov ratio ≥1.01 at the C5 level is a reliable predictor for the development of postoperative C5 palsy. Pavlov ratio may be one of the reasons for postoperative C5 palsy.

Expansive open-door laminoplasty versus laminectomy and instrumented fusion for cases with cervical ossification of the posterior longitudinal ligament and straight lordosis

PURPOSE

To identify whether expansive open-door laminoplasty (Lam) is more appropriate than laminectomy and instrumented fusion (LIF) for cases with ossification of the posterior longitudinal ligament (OPLL) and straight cervical lordosis.

METHODS

A total of 67 cases were included and divided into Group Lam (n = 32) and Group LIF (n = 35), and the mean follow-up periods were 38 and 42 months, respectively. The cervical lordosis was elevated by C2-7 Cobb angle and cervical sagittal balance by C2-C7 sagittal vertical axis (SVA). Japanese Orthopedic Association (JOA), neurological recovery rate (RR) being calculated by the JOA, visual analog scale (VAS) and neck disability index (NDI) were used to assess clinical outcomes.

RESULTS

Differences in general data between two groups were not significant. Total blood loss and operation duration in Group Lam were both significantly less than that in the Group LIF. By the final follow-up, the cervical lordosis significantly decreased in Group Lam and increased in Group LIF, the SVA significantly increased in Group Lam and kept unchanged in Group LIF, and the JOA, VAS, NDI significantly improved in both groups. Although there was no significant difference in RR between the two groups, cases in Group Lam had significantly larger incidence of postoperative kyphosis and kyphotic change rate, and less VAS, NDI and incidence of axial pain than cases in Group LIF.

CONCLUSIONS

When compared with the LIF, the Lam is recommended for cases with OPLL and straight cervical lordosis when taking comparable neurological recovery, less axial pain and better neck function improvement into consideration.

Factors that regulate spinal cord position after expansive open-door laminoplasty

INTRODUCTION

Although appropriate dorsal migration of the spinal cord is a desired end point of cervical laminoplasty, it is difficult to predict in advance the spinal cord position after surgery and to control it during surgery. The aim of the present study was to investigate the factors that affect postoperative spinal cord position after cervical laminoplasty using multivariable analysis.

MATERIALS AND METHODS

We retrospectively assessed 56 consecutive patients with cervical spondylotic myelopathy treated by open-door laminoplasty. The postoperative anterior space of the spinal cord was measured at 204 levels, and its maximum value was measured at 56 levels within the decompressed area. To identify the factors that regulate the postoperative spinal cord position, we evaluated seven radiological parameters, including the C3-C7 lordosis angle (LA), LA of the decompressed area, C3-C7 spinal cord lordosis angle (SCLA), SCLA of the decompressed area, spinal canal sagittal diameter at C5, number of expanded lamina, and postoperative dural sac diameter.

RESULTS

The postoperative anterior space of the spinal cord was 5.5 ± 1.4 mm, and its maximum value was 6.4 ± 1.3 mm. A multiple linear regression analysis revealed that the number of expanded laminae (standardized partial regression coefficient: β = 0.17, p = 0.009) and dural sac diameter (β = 0.43, p < 0.001) was significantly associated with anterior space of the spinal cord. Although these parameters were also significantly associated with the maximum value, their relative contributions were reversed; β = 0.49 (p < 0.001) for the number of expanded laminae and 0.25 (p = 0.029) for the dural sac diameter.

CONCLUSIONS

The number of expanded laminae and dural sac diameter was significantly associated with the spinal cord position after laminoplasty. These factors could help to predict spinal cord position following laminoplasty and achieve adequate indirect decompression of the spinal cord.

Combined expansive open-door laminoplasty with short-segment lateral mass instrumented fusion for multilevel cervical spondylotic myelopathy with short segment instability

OBJECTIVES

Expansive open-door laminoplasty (EOLP) is an effective procedure for multilevel cervical spondylotic myelopathy (MCSM). It preserves a higher range of cervical motion than laminectomy with fusion and reserves more posterior elements than laminectomy alone. MCSM with short-segment instability or correctable local kyphosis often requires long-segment decompression and adequate segment fusion.

MATERIALS AND METHODS

We retrospectively reviewed 20 patients who received EOLP with short-segment posterior lateral mass instrumented fusion at our institution from 2008 to 2011. The follow-up period was at least 36 months. Postoperative functional and radiographic outcomes were collected and analyzed.

RESULTS

Japanese Orthopedic Association scores improved significantly 36 months after surgery and the average recovery ratio was 85.3 ± 14.7%. Nurick disability scores and neck pain visual analog scale scores considerably decreased 3 years after surgery. No patients had aggravated neck pain or C5 nerve palsy during follow-up. The preservation of range of motion was approximately 60% after 36 months. No implant loosening or laminar collapse was reported on radiographic follow-up.

CONCLUSION

EOLP with concomitant lateral mass instrumented fusion yields favorable short-term clinical results for MCSM with short segment instability.