The relationship between preoperative cervical alignment and postoperative spinal cord drift after decompressive laminectomy and arthrodesis for cervical spondylotic myelopathy

Comparing Spinal Cord Drift, Clinical Outcomes and C5 Palsy in Degenerative Cervical Myelopathy: A Study of Cervical Laminoplasty Versus Laminectomy/Fusion

STUDY DESIGN

Retrospective comparative study.

OBJECTIVES

(i)to compare spinal cord drift between laminectomy and fusion(LF) and cervical laminoplasty(LP) for degenerative cervical myelopathy(DCM) treatment,(ii)to study relationship between preoperative cervical alignment, postoperative spinal cord drift, functional outcome, and C5 palsy.

METHODS

A cohort of 114 patients who underwent LP or LF for DCM were identified. After propensity-score matching, both groups included 30 patients each.Cobb angle(C2-C7) was used to assess pre-and postoperative cervical spine alignment(at 2-year follow-up).Based on alignment, there were lordotic(L) and straight(S) subgroups.Spinal cord position was measured on sagittal-and axial-T2W MRI of cervical spine pre-and postoperatively at 2-year follow-up and cord drift was measured by subtracting preoperative values from postoperative values.Functional recovery(mJOA score, mJOA recovery rate),and C5 palsy in patients were recorded and compared.

RESULTS

LF had higher mean spinal cord drift than LP(2.66 ± .77 vs 2.16 ± .80 mm, P = .049).Lordotic subgroups exhibited greater cord drift than straight subgroups within LP and LF groups.Both groups significantly improved mJOA scores at 2-year follow-up, with no LP-LF difference in mJOA recovery rate(mJOA-RR).Lordotic subgroups had significantly higher mJOA-RR(LP-L vs LP-S,P = .048; LF-L vs LF-S,P = .045).Preoperative cervical alignment, cord drift, and mJOA-RR correlated well(Spearman's ρ .7143 and .6053 respectively).Patients with >2.5 mm cord drift(n = 24) had significantly higher mJOA-RR as compared to <2.5 mm cord drift(n = 18). Substantial clinical difference was seen in C5 palsy risk between LP-S and LF-L, with the LF-L group having 3-fold higher risk.

CONCLUSION

LF had a biomechanical advantage in maximizing spinal cord drift in severe DCM cases, while both LP and LF showed significant improvements in neurological function. However, variability in C5 palsy rates highlights the need for individualized patient assessment.

Effectiveness of additional C2 decompression of the cervical spinal canal after cervical laminoplasty: a retrospective cohort study

PURPOSE

This study aimed to assess the effects of additional C2 decompression of the cervical spinal canal on the postoperative outcomes after cervical laminoplasty in patients with cervical stenosis caused by ossification of the posterior longitudinal ligament (OPLL).

MATERIALS AND METHODS

This retrospective cohort study included patients with cervical stenosis due to OPLL and treated between April 2014 and December 2015. The patients who underwent C2-7 (additional C2 decompression) and C3-7 posterior decompression were compared using the Japanese Orthopedic Association (JOA) scores, visual analog scale (VAS) scores, axial symptom scores, and intervals between the posterior margin of the vertebral body and the K-line.

RESULTS

There were 36 and 24 patients in the additional C2 decompression and control groups, respectively. The JOA scores were higher in the additional C2 decompression group than the controls at 1 and 3 years (p < 0.05). Upper extremity motor function after the operation and at 1 and 3 years and lower extremity motor function after operation were improved in the additional C2 decompression group (all p < 0.05 vs. controls). VAS scores were lower in the additional C2 decompression group than controls at 1 year (p < 0.05). Axial symptom scores in the additional C2 decompression group were decreased postoperatively but increased at 1 and 3 years (p < 0.05 vs. controls). Finally, the posterior shift of the K-line in the additional C2 decompression group was significant (from 0.98 to 1.68 cm, p < 0.05).

CONCLUSIONS

Additional C2 decompression might improve the effectiveness of cervical laminoplasty in patients with cervical stenosis caused by OPLL.

Association between pre-operative sagittal alignment and radiographic measures of decompression following cervical laminectomy: a retrospective cohort study

Background

The primary purpose of this study was to determine the association between pre-operative cervical sagittal alignment and the extent of cord decompression in the form of increased spinal cord width and cerebrospinal fluid (CSF) space in front of and behind the cord in patients undergoing laminectomy for cervical spondylotic myelopathy (CSM). Secondary objectives included an assessment of the correlation between increasing numbers of levels decompressed and the post-operative cervical spine sagittal alignment, the effect of laminectomy on the change in alignment, as well as effect of laminectomy on pre-existing spinal cord signal abnormality.

Methods

This retrospective cohort study included patients who underwent cervical laminectomies, without fusion, between 2015 and 2020. Chart review was used to collect baseline variables. Cervical sagittal alignment, width of the spinal cord, and the CSF space in-front and behind the cord was measured pre-operatively and post-operatively using magnetic resonance imaging (MRI) scans for each patient. The correlation between change in measured parameters and pre-operative cervical sagittal alignment was assessed using Spearman's correlation.

Results

Thirty-five patients were included. Average age was 65.29±10.98 years old. The majority of patients (80%) underwent laminectomies at 3-4 levels. Average pre-operative sagittal alignment determined by the Cobb angle was 6.05°±14.17°, while the average post-operative Cobb angle was 3.15°±16.64°. The change in Cobb angle was not statistically significant (P=0.998). Eleven patients (32%) had pre-operative kyphotic sagittal alignment. The average time from surgery to post-operative MRI scan was 20.44±13.18 months (range, 3-39; median, 18.5; IQR, 23.5). There was no statistically significant association between increasing levels of decompression and change in alignment (P=0.546). Cord signal abnormality persisted after decompression. There was a moderate correlation between lordotic pre-operative cervical sagittal alignment and change in space in-front of the cord (correlation coefficient 0.337, P=0.048) and change in cord width (correlation coefficient 0.388, P=0.021).

Conclusions

Severity of pre-operative kyphotic sagittal alignment is associated with decreased spinal cord drift and extent of decompression. The pre-operative sagittal alignment is not significantly associated with the change in post-operative alignment. Increasing number of levels decompressed does not worsen a kyphotic cervical spine sagittal alignment.

Spinal Cord Drift Following Laminoplasty Versus Laminectomy and Fusion for Cervical Spondylotic Myelopathy

BACKGROUND

Cervical laminoplasty and laminectomy and fusion (LF) are posterior-based surgical techniques for the surgical treatment of cervical spondylotic myelopathy (CSM). Interestingly, the comparative amount of spinal cord drift obtained from these procedures has not been extensively described. The purpose of this study is to compare spinal cord drift between cervical laminoplasty and LF in patients with CSM.

METHODS

The laminoplasty group consisted of 22 patients, and the LF group consisted of 44 patients. Preoperative and postoperative alignment was measured using the Cobb angle (C2-C7). Spinal cord position was measured on axial T2-magnetic resonance imaging of the cervical spine preoperatively and postoperatively. Spinal cord drift was quantified by subtracting preoperative values from postoperative values. Functional improvement was assessed using the modified Japanese Orthopaedic Association (mJOA) score.

RESULTS

Mean spinal cord drift was higher following LF compared to laminoplasty (2.70 vs 1.71 mm, P < .01). Using logistic regression analysis, there was no correlation between sagittal alignment and spinal cord drift. Both groups showed an improvement in mJOA scores postoperatively compared to their preoperative values (laminoplasty, +2.0, P = .012; LF, +2.4, P < .01). However, there was no difference in mJOA score improvement postoperatively between both groups (P = .482).

CONCLUSIONS

This study demonstrates that patients who had LF for CSM achieved more spinal cord drift postoperatively compared to those who had laminoplasty. However, the increased drift did not translate into superior functional outcome as measured by the mJOA score.

LEVEL OF EVIDENCE

3.

CLINICAL RELEVANCE

Spinal cord drift following LF may differ from laminoplasty in patients undergoing surgery for CSM. This finding should be considered when assessing CSM patients for surgical intervention.

The R-line: A New Imaging Index for Decision Making Regarding C2 Lamina Decompression in Cervical Ossification of the Posterior Longitudinal Ligament

Objective

The optimal treatment modality for cervical ossification of the posterior longitudinal ligament (OPLL) including the C2 level remains controversial. Cervical laminoplasty is a widely accepted considering of advantages such as development of few postoperative complications, including kyphosis or neck pain. We encountered seven patients with postoperative disabilities resulting from incomplete decompression after undercutting of the C2 lamina. Based on this experience, we developed a new index to determine the degree of decompression in cervical OPLL—the rostral line (R-line).

Methods

Total of 79 consecutive patients who underwent posterior decompression of cervical OPLL were included in this study. Mean age at the time of operation, the C2-C7 cervical lordotic angle and OPLL thickness at the most stenotic level of the spinal canal, and preoperative/postoperative Japanese Orthopedic Association score was checked in these group. We compared the correspondence between the degree of C2 lamina decompression using the R-line and actual degree of decompression.

Results

In all patients, the R-line touched the upper half of the C2 lamina on preoperative magnetic resonance imaging (MRI). The C2-C3 local segment lordotic angle and maximal degree of spinal cord compression by OPLL were independently correlated to postoperative C2 cord shifting. This result indicates that the R-line is a valid indicator to determine the degree of C2 lamina decompression in OPLL extending to the C2 level.

Conclusion

The results showed that undercutting the C2 lamina can result in incomplete spinal cord decompression and poor clinical outcome if the R-line touches the upper half of the C2 lamina on preoperative MRI.

Differential Analysis of the Spinal Cord Shift After Laminoplasty With Upper Extension to the C2 Segment and Conventional Surgery of the C3-C7 Segments

STUDY DESIGN

A retrospective controlled study.

OBJECTIVE

To clarify the differences of spinal cord shift between laminoplasty with extension to the C2 segment and conventional surgery of the C3-C7 segments.

SUMMARY OF BACKGROUND DATA

For patients of spinal cord compression at C2/C3 or C2, it is difficult to achieve decompression involving only the C3-C7 segments. Therefore, a laminoplasty with upper extension to C2 is needed. Nevertheless, there is not yet a definitive conclusion regarding whether laminoplasty with extension to C2 can achieve a better spinal cord shift than an extension of the C3-C7 segments.

MATERIALS AND METHODS

Preoperative and final follow-up Japanese Orthopedic Association scores were recorded. MRI T2 patient images before and after surgery were used for data collection. The anterior subarachnoid spaces, spinal cord diameters, posterior subarachnoid spaces, and dural sac diameters were measured. The distance of spinal cord shift in a single plane was represented by the differences in the sum of the anterior subarachnoid spaces and the spinal cord diameters before and after surgery. The overall distances and distances of each segment backward were compared between the C2-C7 group and the C3-C7 group. All planes were also classified as segments with compression or noncompression, and the differences in backward shift were compared.

RESULTS

There were no significant differences in Japanese Orthopedic Association score between the C2-C7 and C3-C7 groups at final follow-up and no significant differences in the overall backward shift between the 2 groups. The spinal cord shift of C1, C2, and C2/C3 segments and the segment of the largest shift distance were significantly different between the 2 groups; the spinal cord shift of the segments under compression was larger than that of noncompression.

CONCLUSIONS

Surgery with upper extension to the C2 segment did not increase the overall spinal cord shift; instead, a better effect was achieved by the effective decompression of local compressed segments, thus obtaining an effective expansion and shift of the spinal cord.

LEVELS OF EVIDENCE

Level II.

Outcomes of posterior cervical fusion and decompression: a systematic review and meta-analysis

BACKGROUND CONTEXT

Posterior cervical fusion (PCF) with decompression is a treatment option for patients with conditions such as spondylosis, spinal stenosis, and degenerative disc disorders that result in myelopathy or radiculopathy. The annual rate, number, and cost of PCF in the United States has increased. Far fewer studies have been published on PCF outcomes than on anterior cervical fusion (ACF) outcomes, most likely because far fewer PCFs than ACFs are performed.

PURPOSE

To evaluate the patient-reported and clinical outcomes of adult patients who underwent subaxial posterior cervical fusion with decompression.

STUDY DESIGN/SETTING

Systematic review and meta-analysis.

PATIENT SAMPLE

The total number of patients in the 31 articles reviewed and included in the meta-analysis was 1,238 (range 7-166).

OUTCOME MEASURES

Preoperative to postoperative change in patient-reported outcomes (visual analog scales for arm pain and neck pain, Neck Disability Index, Japanese Orthopaedic Association [JOA] score, modified JOA score, and Nurick pain scale) and rates of fusion, revision, and complications or adverse events.

METHODS

This study was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and a preapproved protocol. PubMed and Embase databases were searched for articles published from January 2001 through July 2018. Statistical analyses for patient-reported outcomes were performed on the outcomes' raw mean differences, calculated as postoperative value minus preoperative value from each study. Pooled rates of successful fusion, revision surgery, and complications or adverse events, and their 95% confidence intervals, were also calculated. Two subgroup analyses were performed: one for studies in which only myelopathy or radiculopathy (or both) were stated as surgical indications and the other for studies in which only myelopathy or ossification of the posterior longitudinal ligament (or both) were stated as surgical indications. This study was funded by Providence Medical Technology, Inc. ($32,000).

RESULTS

Thirty-three articles were included in the systematic review, and 31 articles were included in the meta-analysis. For all surgical indications and for the 2 subgroup analyses, every cumulative change in patient-reported outcome improved. Many of the reported changes in patient-reported outcome also exceeded the minimal clinically important differences. Pooled outcome rates with all surgical indications were 98.25% for successful fusion, 1.09% for revision, and 9.02% for complications or adverse events. Commonly reported complications or adverse events were axial pain, C5 palsy, transient neurological worsening, and wound infection.

CONCLUSIONS

Posterior cervical fusion with decompression resulted in significant clinical improvement, as indicated by the changes in patient-reported outcomes. Additionally, high fusion rates and low rates of revision and of complications and adverse events were found.

The effect of dural release on extended laminoplasty for the treatment of multi-level cervical myelopathy

Objective

The effects of dural release on extended laminoplasty for the treatment of multi-level cervical myelopathy were explored and discussed.

Method

Patients, who underwent extended laminoplasty combined with dural release for the treatment of multi-level cervical myelopathy (35 cases, group A), were compared with patients who underwent simple extended laminoplasty (38 cases, group B). The JOA score, improvement rate, VAS score, distance of retroposition of the spinal cord, cervical lordosis were compared between the two groups.

Results

Dural laceration occurred to five patients during surgery, three in group A and two in group B; cerebrospinal fluid leakage occurred to five patients, three in group A and two in group B. All patients were followed up for 10 to 48 months (mean 20.3 months). JOA scores and VAS scores in the last follow up period were significantly improved in the two groups than preoperative scores (p < 0.05). The improvement rate and JOA scores in group A were significantly higher than group B, while VAS scores in group A were significantly lower than group B (p < 0.05). There were no significant differences in cervical lordosis in the two groups in the last follow up (p > 0.05), and the distance of retroposition of the spinal cord in group A was higher than B (p < 0.05). No shut-up of the ‘door’ of vertebral lamina occurred in the period of follow-up.

Conclusion

Dural release on extended laminoplasty can achieve retroposition of the spinal cord for multi-level cervical myelopathy, which is more effective than simple extended laminoplasty.

Selective blocking laminoplasty in cervical laminectomy and fusion to prevent postoperative C5 palsy

BACKGROUND CONTEXT

Cervical laminectomy and fusion (CLF) is a common surgical option for multilevel cord compression. Postoperative C5 palsy occurrence after CLF has been a vexing problem for spine physicians. The posterior shift of the cord following laminectomy has been implicated as a major factor for postoperative C5 palsy, but attempts by spine surgeons to mitigate excessive shift while providing sufficient decompression have not been well reported.

PURPOSE

To compare the incidence of postoperative C5 palsy after performing selective blocking laminoplasty concurrently with CLF to those of conventional CLF.

STUDY DESIGN

A retrospective comparative study of prospectively collected data.

PATIENT SAMPLE

Of 116 cervical myelopathy patients with degenerative cervical myelopathy, ossification of the posterior longitudinal ligament, and multilevel disc herniation, 93 patients (69 in group A [CLF group] and 24 in group B [selective blocking laminoplasty with CLF, CLF-S group]) were included in the study.

OUTCOME MEASURES

The primary outcome measure was the occurrence of postoperative C5 palsy. Secondary end points included (1) clinical outcomes based on pain intensity, neck disability index (NDI), Japanese Orthopaedic Association (JOA) score, (2) radiologic outcomes including cervical alignment and fusion rate at 1 year and hardware complications, and (3) perioperative data (hospital stay, blood loss, and operative times).

METHODS

We compared the occurrence of postoperative C5 palsy, as well as clinical, radiologic, and surgical outcomes, between the two groups at 1-year follow-up.

RESULTS

The patients in both groups were statistically similar between the groups with respect to demographic characteristics such as age, sex, smoking status, body mass index, preoperative pathology, surgical segments, and the degree of the cervical lordosis. Postoperative C5 palsy developed in 9 of 61 patients (14%) in group A and in 0 of 24 patients (0%) in group B (CLF-S group) (p=.03). Postoperative neck pain, NDI, and JOA improvement were not significantly different between the two groups (p=.93, 0.90, and 0.79, respectively). Perioperative data did not differ significantly between the two groups.

CONCLUSIONS

This study showed that performing selective blocking laminoplasty might lead to reducing the incidence of postoperative C5 palsy in CLF surgery.

Narrow width of muscle-preserving selective laminectomy demonstrated sufficient surgical outcomes and reduced surgical invasiveness

Sufficient width of laminectomy or laminoplasty is considered a criterion for successful surgical outcomes following posterior cervical decompression. No previous study has focused on surgical outcomes achieved by wide versus narrow decompression. This study examined whether narrow laminectomy width (LW) affected surgical outcomes in cervical compressive myelopathy (CCM). Between 2005 and 2010, we performed muscle-preserving selective laminectomy (SL) with decompression between the bilateral medial margin of the facet joints (wide SL). After 2010, we began to perform narrow SL, in which the LW was no more than 2-3 mm wider than the spinal cord width (SW). Clinical features and radiological findings from 97 CCM patients in whom SL was performed at two consecutive levels, including the C4/5 level, were examined in this study. The relationship between LW and patients' functional outcomes was analyzed. Mean blood loss was lower in the narrow SL group than in the wide SL group. The length of hospital stay was also shorter in the narrow SL group. The wide SL group showed greater posterior spinal cord shift. The incidence of C5 palsy correlated with LW and LW minus SW (LW-SW). The recovery rate (RR) of Japanese Orthopaedic Association score was comparable between the two groups. The RR was not correlated with LW and LW-SW. Sufficient functional recovery can be achieved by narrow SL, and it offers advantages over wide posterior decompression, including reduced surgical invasiveness and complications. Wide decompression width is not always necessary for CCM patients.

Increased stress and strain on the spinal cord due to ossification of the posterior longitudinal ligament in the cervical spine under flexion after laminectomy

Myelopathy in the cervical spine due to cervical ossification of the posterior longitudinal ligament could be induced by static compression and/or dynamic factors. It has been suggested that dynamic factors need to be considered when planning and performing the decompression surgery on patients with the ossification of the posterior longitudinal ligament. A finite element model of the C2-C7 cervical spine in the neutral position was developed and used to generate flexion and extension of the cervical spine. The segmental ossification of the posterior longitudinal ligament on the C5 was assumed, and laminectomy was performed on C4-C6 according to a conventional surgical technique. For various occupying ratios of the ossified ligament between 20% and 60%, von-Mises stresses, maximum principal strains in the spinal cord, and cross-sectional area of the cord were investigated in the pre-operative and laminectomy models under flexion, neutral position, and extension. The results were consistent with previous experimental and computational studies in terms of stress, strain, and cross-sectional area. Flexion leads to higher stresses and strains in the cord than the neutral position and extension, even after decompression surgery. These higher stresses and strains might be generated by residual compression occurring at the segment with the ossification of the posterior longitudinal ligament. This study provides fundamental information under different neck positions regarding biomechanical characteristics of the spinal cord in cervical ossification of the posterior longitudinal ligament.

Regression of Anterior Disk-Osteophyte Complex Following Cervical Laminectomy and Fusion for Cervical Spondylotic Myelopathy

STUDY DESIGN

A retrospective case-control study.

OBJECTIVE

To investigate whether posterior cervical laminectomy and fusion modifies the natural course of anterior disk-osteophyte complex in patients with multilevel cervical spondylotic myelopathy.

SUMMARY OF BACKGROUND DATA

Dorsal migration of the spinal cord is the main purported mechanism of spinal cord decompression following cervical laminectomy and fusion but other potential mechanisms have received scant attention in the literature. This study was conducted to investigate whether cervical laminectomy and fusion affects the size of anterior disk-osteophyte complex.

METHODS

The medical records and radiographic imaging of 44 patients who underwent cervical laminectomy and fusion for cervical spondylotic myelopathy between 2006 and 2013 were analyzed. The size of the anterior disk-osteophyte complex was measured preoperatively and postoperatively on MR images taken at an interval of >3 months apart. A control group consisted of 20 nonoperatively treated advanced cervical spondylosis patients. Patients in the control met the same inclusion and exclusion criteria and also had sequential magnetic resonance imaging (MRI) taken at an interval of >3 months apart.

RESULTS

The nonoperative and operative groups were statistically similar in the pertinent patient demographics and characteristics including sex, age, time to second MRI, size of anterior disk-osteophyte complex on baseline MRI, mean number of levels affected, and percentage of patients with T2 signal change. As expected the mJOA scores were significantly lower in the operative versus nonoperative cohort (13.6 vs. 16.5, P<0.01). A significant decrease in the size of anterior disk osteophyte was observed in the operative group postoperatively (P<0.01). In comparison, there was no statistically significant change in the size of the anterior disk-osteophyte complex in the control group (P>0.05). The magnitude of the change in disk size between the 2 groups was statistically significant (P<0.01).

CONCLUSIONS

The findings of this study suggest that regression of anterior disk-osteophyte complex occurs following cervical laminectomy and fusion, and likely provides another mechanism of spinal cord decompression.

Expansive open-door laminoplasty secured with titanium miniplates is a good surgical method for multiple-level cervical stenosis

BACKGROUND

Laminoplasty is an effective procedure for treating cervical spondylotic myelopathy (CSM). Little information is available regarding the surgical outcomes of expansive open-door laminoplasty (EOLP) when securing with titanium miniplates without bone grafting. This study is aimed to elucidate the efficacy of and problems associated with EOLP secured with titanium miniplates without bone grafting, thereby enhancing future surgical outcomes.

METHODS

This is a retrospective study. The study participants comprised 104 patients who underwent cervical EOLP secured with titanium miniplates without bone graft for CSM treatment between August 2005 and March 2011. The clinical results were evaluated based on the Japanese Orthopedic Association (JOA) and Nurick scores. The radiographic outcomes were determined based on plain film and magnetic resonance imaging findings, which were assessed and compared.

RESULTS

Lateral cervical spine X-rays exhibited improvement in the Pavlov ratio of the spinal canal at 1 day postoperation, and this ratio did not change at 1 year postoperation. The mean cervical curvature from C2 to C7 decreased 0.21° ± 10.09° and the mean cervical range of motion was deteriorated by 35% at 12 months (P < 0.05). The Nurick score improved from 3.19 ± 1.06 to 0.92 ± 1.32 (P < 0.05). The mean JOA recovery rate was 75% ± 21.1% at 1 year. The mean level of postoperative neck pain at 3 months was 3.09 ± 2.31, as determined using the visual analogue scale (VAS). Increased age, concomitant thoracolumbar stenosis, depression disorder, and preexisting myelomalacia negatively affected the JOA recovery rate (P < 0.05). A decreased preoperative Nurick score and superior sensory function in the upper extremities were powerful predictors of an enhanced JOA recovery rate. The postoperative complications involved hematoma formation 0.9%, reversible C5 nerve palsy 2.8%, and moderate to severe neck pain (VAS ≥ 4) 42%. No cases of lamina closure or collapse were observed.

CONCLUSION

EOLP secured with titanium miniplates without bone grafting is a safe and effective surgical method for treating most patients with CSM.

Is cervical lordosis relevant in laminoplasty?

BACKGROUND CONTEXT

Laminoplasty aims to decompress the spinal cord and stabilize the cervical spine in patients with multilevel cervical lesions. Not every patient with cervical compressive myelopathy is a good candidate for laminoplasty. Most studies recommend that neutral or kyphotic alignments are contraindications for laminoplasty. However, cervical sagittal alignment does not have a strong and consistent effect on the clinical outcomes of laminoplasty. Moreover, many reports on the effect of cervical sagittal alignment did not designate the ideal definition of alignment and used different definitions of lordosis.

PURPOSE

To identify the effect of preoperative cervical alignment according to two different definitions after midline splitting double-door laminoplasty.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

From August 2008 to September 2010, 58 patients were diagnosed with cervical myelopathy and treated with midline splitting double-door laminoplasty.

OUTCOME MEASURES

The clinical results were assessed with the modified Japanese Orthopedic Association (JOA) score, neck disability index (NDI), and visual analog scale (VAS) and were compared to analyze the rate of change between preoperative and postoperative values. Postoperative radiological results at the final follow-up examinations were compared between groups to obtain the change in range of motion and sagittal alignment.

METHOD

The effect of cervical alignment on JOA, NDI, and VAS scales and also on change of alignment and change of range of motion (ROM) at the final follow-up examinations was analyzed statistically between two groups according to two different definitions such as Toyama classification and Cobb angle.

RESULTS

No difference was found between the two groups according to Toyama classification in terms of the postoperative improvement rate of the modified JOA score (p=.086), decreasing rate of the VAS (p=.940) or NDI (p=.211), postoperatively. Additionally, no difference was found for the decreasing rate of ROM (p=.427) or sagittal alignment (p=.864) based on the radiological evaluation results. Also, there was no difference between two groups according to Cobb angle in terms of the modified JOA score (p=.743), VAS (p=.548), or NDI (p=.32), postoperatively. Additionally, no difference was found for the ROM (p=1.000) or sagittal alignment (p=.440) based on the radiological evaluation results.

CONCLUSIONS

Despite nonlordosis cervical sagittal alignment, double-door laminoplasty would be effective for patients with cervical myelopathy because of cervical spondylotic myelopathy or ossification of the posterior longitudinal ligament. Furthermore, sagittal alignment is not the absolute and sole factor that surgeons should consider when determining the optimal treatment strategy.

Effect of the decompressive extent on the magnitude of the spinal cord shift after expansive open-door laminoplasty

STUDY DESIGN

A retrospective study to analyze the effect of decompressive extent on the posterior shift of spinal cord after expansive open-door laminoplasty (ELAP).

OBJECTIVE

To investigate the effect of decompressive extent on cord shift distance after ELAP, and determine the morphologic limitations of posterior approach when the cervical alignment is lordotic or straight.

SUMMARY OF BACKGROUND DATA

It is still controversial on the effect of space available for spinal cord at the level cephalad to the decompression with cord shift. Moreover, there is less understanding regarding the significance of decompressive extent of laminoplasty in relation to spinal cord shift and clinical outcome.

METHODS

Preoperative and postoperative MRIs of 76 patients with a straight or lordotic cervical spine who had undergone cervical laminoplasty were reviewed and evaluated retrospectively. Radiographic parameters including cervical sagittal alignment, space available at the level cephalad, the thickness of compressive mass, and the average anterior subarachnoid space were measured. Laminoplasty was performed from C1 to C7 in 11 cases (CI group), C2 to C7 in 30 cases (CII group), and C3 to C7 in 35 cases (CIII group). According to whether the anterior indirect decompression was adequate or not, CII and CIII groups were further divided into two subgroups, the noncontact group in which the spinal cord was completely separated from the anterior compressive mass after laminoplasty, and the contact group in which there was residual cord compression after laminoplasty. The recovery rate that based on the Japanese Orthopedic Association score was calculated for each patient.

RESULTS

There were statistically significant differences in the average anterior subarachnoid space among CI, CII, and CIII groups (P < 0.05);the average anterior subarachnoid space was the largest in CI group, and the smallest in CIII group. The space available at the level cephalad had strong sigmoidal correlation with cord postoperative shift in CIII group (R = 0.91). A higher neurologic recovery rate (69% ± 20% vs. 29% ± 11%; P < 0.05) in the noncontact group after surgery than in the contact group, with a similar follow-up period.

CONCLUSION

The posterior decompression extent is a main factor affecting cord shift distance after laminoplasty in the context of a straightened or lordotic cervical curvature. The space available at the levels cephalad is a key factor to predict cord shift distance in laminoplasty from C3 to C7. Neurologic recovery rate after ELAP is affected by whether the anterior indirect decompression was adequate or not.