Greater cervical kyphosis during flexion increases the risk of kyphotic deformity after laminoplasty in patients with cervical spondylotic myelopathy.

Kyphotic deformity following the loss of cervical lordosis can lead to unfavourable neurological recovery after cervical laminoplasty (CLP); therefore, it is essential to identify its risk factors. Recent studies have demonstrated that the dynamic parameters of the cervical spine, based on baseline flexion/extension radiographs, are highly useful to estimate the loss of cervical lordosis after CLP. However, it remains unclear whether such dynamic parameters can predict kyphotic deformity development after CLP. Hence, the present study aimed to investigate whether the dynamic parameters could predict kyphotic deformity in patients with cervical spondylotic myelopathy (CSM) after CLP. This retrospective study included 165 patients, consisting of 10 and 155 patients with and without cervical kyphosis of C2-C7 angle ≤ -10° at the final follow-up period, respectively. Among the static and dynamic parameters of the cervical spine, greater cervical kyphosis during flexion (fC2-C7 angle) demonstrated the best discrimination between these two cohorts, with an optimal cutoff value of -27.5°. Meanwhile, greater gap range of motion (gROM = flexion ROM - extension ROM ) had the highest ability to predict a loss of ≥ 10° in C2-C7 angle after CLP, with an optimal cutoff value of 28.5°. This study suggests that in patients with CSM, fC2-C7 angle ≤ -25° on baseline radiographs is a potential risk for kyphotic deformity after CLP. In clinical practice, the patients with this criterion (fC2-C7 angle ≤ -25°) along with gROM ≥ 30° are at high risk of developing significant kyphotic deformity after CLP.

Comparison of Cervical Pedicle Screw Placement Accuracy With Robotic Guidance System Versus Image Guidance System Using Propensity Score Matching.

STUDY DESIGN: A retrospective study. OBJECTIVE: To compare the accuracy of cervical pedicle screw (CPS) placement using a robotic guidance system (RGS) with that of using an image guidance system (IGS; navigation system) through propensity score matching. BACKGROUND: The RGS may provide accurate CPS placement, which may outperform IGS. However, no study has directly compared the accuracy of CPS placement with the RGS to that with the IGS. PATIENTS AND METHODS: We retrospectively reviewed the data of patients who had undergone cervical fusion surgery using CPS with the RGS or IGS. To adjust for potential confounders (patient demographic characteristics, disease etiology, and registration material), propensity score matching was performed, creating robotic guidance (RG) and matched image guidance (IG) groups. The accuracy of CPS placement from C2 to C6, where the vertebral artery runs, was evaluated on postoperative computed tomography images according to the Neo classification (grade 0 to grade 3). Furthermore, the intraoperative CPS revisions and related complications were examined. RESULTS: Using propensity score matching, 22 patients were included in the RG and matched groups each, and a total of 95 and 105 CPSs, respectively, were included in the analysis. In both the axial and sagittal planes, the clinically acceptable rate (grades 0 + 1) of CPS placement did not differ between the RG and matched IG groups (97.9% vs 94.3% and 95.8% vs 96.2%, respectively). The incidence of CPS revision was similar between the groups (2.1% vs 2.9%), and no CPS-related complications were documented. Meanwhile, the incidence of lateral breach (grades 1 + 2 + 3) was significantly lower in the RG group than in the matched IG group (1.1% vs 7.7%, P= 0.037). CONCLUSION: The RGS and IGS can equally aid in accurate and safe CPS placement in clinical settings. Nonetheless, RGS can further reduce the lateral breach, compared with IGS.

Clinical outcome of surgical management of mild cervical compressive myelopathy based on minimum clinically important difference.

BACKGROUND CONTEXT: Cervical compressive myelopathy (CCM), caused by cervical spondylosis (cervical spondylotic myelopathy [CSM]) or ossification of the posterior longitudinal ligament (OPLL), is a common neurological disorder in the elderly. For moderate/severe CCM, surgical management has been the first-line therapeutic option. Recently, surgical management is also recommended for mild CCM, and a few studies have reported the surgical outcome for this clinical population. Nonetheless, the present knowledge is insufficient to determine the specific surgical outcome of mild CCM. PURPOSE: To examine the surgical outcomes of mild CCM while considering the minimum clinically important difference (MCID). STUDY DESIGN: Retrospective study. PATIENT SAMPLE: Patients who underwent subaxial cervical surgery for CCM caused by CSM and OPLL between 2013 and 2022 were enrolled. OUTCOME MEASURES: The Japanese Orthopedic Association score (JOA score) was employed as the clinical outcomes. Based on previous reports, the JOA score threshold to determine mild myelopathic symptoms was set at ≥14.5 points, and the MCID of the JOA score for mild CCM was set at 1 point. METHODS: The patients with a JOA score of ≥14.5 points at baseline were stratified into the mild CCM and were examined while considering the MCID. The mild CCM cohort was dichotomized into the improvement group, including the patients with an achieved MCID (JOA score ≥1 point) or with a JOA score of 17 points (full mark) at 1 year postoperatively, and the nonimprovement group, including the others. Demographics, symptomatology, radiographic findings, and surgical procedure were compared between the two groups and studied using the receiver operating characteristic (ROC) curve. RESULTS: Of 335 patients with CCM, 43 were stratified into the mild CCM cohort (mean age, 58.5 years; 62.8% male). Among them, 25 (58.1 %) patients were assigned to the improvement group and 18 (41.9 %) were assigned to the nonimprovement group. The improvement group was significantly younger than the nonimprovement group; however, other variables did not significantly differ. ROC curve analysis showed that the optimal cutoff point of the patient's age to discriminate between the improvement and nonimprovement groups was 58 years with an area under the curve of 0.702 (p=.015). CONCLUSIONS: In the present study, the majority of patients with mild CCM experienced improvement reaching the MCID of JOA score at 1 year postoperatively. The present study suggests that for younger patients with mild CCM, especially those aged below 58 years, subjective neurological recovery is more likely to be obtained. Meanwhile, the surgery takes on a more prophylactic significance to halt disease progression for older patients. The results of this study can help in the decision-making process for this clinical population.

Ultrasonographic Evaluation of Upper Esophageal Sphincter for Dysphagia During the Acute Postoperative Phase of Anterior Cervical Surgery.

STUDY DESIGN: A retrospective study. OBJECTIVE: To verify the pathophysiology of dysphagia during the acute postoperative phase of anterior cervical surgery and to identify its predictive features, using ultrasonographic (US) examination for upper esophageal sphincter (UES). SUMMARY OF BACKGROUND DATA: There are no clinical studies investigating dysphagia after anterior cervical surgery, using US examination for UES. MATERIALS AND METHODS: We enrolled patients who underwent anterior cervical spine surgery between August 2018 and March 2022. Dysphagia was evaluated using the Eating Assessment Tool-10 (EAT-10) questionnaires. The US examination was performed preoperatively and 2 weeks postoperatively. Three US parameters for morphologic measurements (outer diameter, inner diameter, and muscle thickness) and 4 for functional measurements (displacement, time to relax, passing duration, and time to contract) were assessed. To verify the pathophysiology of postoperative dysphagia, we examined the change in the ratios of US parameters (=US parameter 2 weeks postoperatively /US parameter at baseline ) and the existence of significant correlations with change in the EAT-10 score (=EAT-10 2 weeks postoperatively -EAT-10 at baseline ). To identify the predictive features, the baseline US parameters were compared between dysphagia (+) and dysphagia (-) groups. RESULTS: A total of 46 patients (mean age, 61.3 y; 78.3% male) were included for analysis. A greater increase of the EAT-10 score after surgery was positively correlated with change ratios of the muscle thickness and time to contract and negatively with change ratio of the inner diameter. The dysphagia (+) group exhibited significantly greater inner diameter and smaller muscle thickness at baseline than the dysphagia (-) group. CONCLUSION: Dysphagia during the acute postoperative phase of anterior cervical surgery is caused by the physical narrowing of the inner lumen due to muscle thickening of the UES and sphincter contractile dysfunction. In addition, a baseline UES morphology characterized by a greater inner diameter and a thinner muscle layer is predictive of postoperative dysphagia.

Studies in the Falls Efficacy Scale-International for patients with cervical compressive myelopathy: Reliability, validity, and minimum clinically important difference.

CONTEXT: Patients with cervical compressive myelopathy (CCM) often complain of body balance problems, such as fear of falling and bodily unsteadiness. However, no accepted patient-reported outcome measures (PROMs) for this symptomatology exist. The Falls Efficacy Scale-International (FES-I) is one of the most widely used PROMs for evaluating impaired body balance in various clinical fields. OBJECTIVE: To examine reliability, validity, and minimum clinically important difference (MCID) of the FES-I for the evaluation of impaired body balance in patients with CCM. METHODS: Patients who underwent surgery for CCM were retrospectively reviewed. The FES-I was administered preoperatively and at 1 year postoperatively. Further, cJOA-LE score (subscore for lower extremities in the Japanese Orthopaedic Association score for cervical myelopathy) and stabilometric data, obtained at the same time points of the FES-I administration, were analyzed. Reliability was examined through internal consistency with Cronbach's alpha. Convergent validity was studied using correlation analysis. The MCID was estimated using anchor- and distribution-based methods. RESULTS: Overall, 151 patients were included for analysis. Cronbach's alpha coefficient was the acceptable value of 0.97 at both baseline and 1 year postoperatively. As for convergent validity, the FES-I had significant correlations with the cJOA-LE score and stabilometric parameters both at baseline and 1 year postoperatively. The MCID calculated using anchor- and distribution-based methods was 5.5 and 10, respectively. CONCLUSION: FES-I is a reliable and valid PROM to evaluate body balance problems for the CCM population. The established thresholds of MCID can help clinicians recognize the clinical significance of changes in patient status.

Segmental cervical instability does not drive the loss of cervical lordosis after laminoplasty in patients with cervical spondylotic myelopathy.

BACKGROUND/CONTEXT: Kyphotic deformity after cervical laminoplasty (CLP) often leads to unfavorable neurological recovery due to insufficient indirect decompression of the spinal cord. Existing literature has described that segmental cervical instability is a contraindication for CLP because it is a potential risk factor for kyphotic changes after surgery; however, this has never been confirmed in any clinical studies. PURPOSE: To confirm whether segmental cervical instability was an independent risk factor for postoperative kyphotic change and to examine whether segmental cervical instability led to poor neurological outcomes after CLP for cervical spondylotic myelopathy (CSM). STUDY DESIGN/SETTING: A retrospective study PATIENT SAMPLE: Patients who underwent CLP for CSM between January 2013 and January 2021 with a follow-up period of ≥1 year were enrolled. OUTCOME MEASURES: Cervical radiographic measurements including C2-C7 lordosis (C2-7 angle), cervical sagittal vertical axis, C7 slope, flexion range of motion (fROM) and extension ROM (eROM) were assessed using neutral and flexion-extension views. Segmental cervical instability was classified into anterolisthesis (AL) of ≥2 mm displacement, retrolisthesis (RL) of ≥2 mm displacement, and translational instability (TI) of ≥3 mm translational motion. The amount of C2-7 angle loss at the follow-up period compared to the preoperative measurements was defined as cervical lordosis loss (CLL). Neurological outcomes were assessed using the recovery rate of the Japanese Orthopedic Association score (JOA-RR). METHODS: CLL was compared among patients with and without segmental cervical instability. Further, multiple linear regression model for CLL was built for the evaluation with adjustment of the reported risks, including cervical sagittal vertical axis, C7 slope, fROM, eROM, and patient age together with AL, RL, and TI, as independent variables. The JOA-RR was also compared between patients with and without segmental cervical instability. RESULTS: A total of 138 patients (mean age, 68.7 years; 65.9% male) were included in the analysis. AL, RL, and TI were found in 12 (8.7%), 33 (23.9%), and 16 (11.6%) patients, respectively. Comparisons among the groups showed that AL led to greater CLL; however, RL and TI did not. Multiple linear regression analysis revealed that greater CLL is significantly associated with greater fROM and smaller eROM (regression coefficient [ß]=0.328, 95% confidence interval: 0.178 to 0.478, p<.001; ß=-0.372, 95% confidence interval: -0.591 to -0.153, p=.001, respectively). However, there were no significant statistical associations in the AL, RL, and TI. Whereas, patients with AL tended to exhibit lower JOA-RR than those without AL (37.8% vs. 52.0%, p=.108). CONCLUSIONS: Segmental cervical instability is not the definitive driver for loss of cervical lordosis after CLP in patients with CSM; thus, is not a contraindication in and of itself. However, it is necessary to consider the indications for CLP, according to individual cases of patients with AL on baseline radiograph, which is a sign of poor neurological recovery.

Periodic quadriplegia during the acute postoperative phase of cervical laminoplasty: a case report and literature review.

The use of antibiotics can, in rare cases, induce neuromuscular blockade (NMB), resulting in paralytic symptoms. Although such antibiotic-induced NMB has been described in the anaesthesiology and infectious disease literature, it is an unfamiliar clinical entity in the fields of neurosurgery and spinal surgery. Herein, we report a case of periodic quadriplegia due to NMB induced by perioperative prophylactic antibiotic of cefazolin, resulting in highly confusing paralytic symptoms during the acute postoperative phase of cervical laminoplasty, together with a review of the relevant literature.

Usefulness of Percutaneous Ultrasonography for Deciding the Need of Surgical Evacuation of Epidural Hematoma After Cervical Double-door Laminoplasty.

STUDY DESIGN: This was a retrospective study. OBJECTIVE: The objective of this study was to investigate the diagnostic utility of percutaneous ultrasonography (PUS) for postoperative epidural hematoma (EH) as a postoperative complication. SUMMARY OF BACKGROUND DATA: We investigated the usefulness of PUS for determining the need of surgical evacuation of postoperative EH by comparing the postoperative magnetic resonance imaging (MRI) and PUS of the spinal cord. MATERIALS AND METHODS: This study included patients who underwent cervical laminoplasty using suture anchors. Regular MRI and PUS were performed 1 week postoperatively. Whenever the patients exhibited neurological deterioration, MRI and PUS were performed. The spinal cord decompression status was classified into 3 grades using MRI and PUS. The existence of spinal pulsation was determined by PUS. RESULTS: One hundred thirty-one patients were investigated. The decompression status by MRI and PUS, and the pulsation status by PUS showed a correlation with neurological deterioration (P<0.001). Four cases showed postoperative neurological deterioration and required revision surgery. The decompression status in these cases was classified as "poor" by both MRI and PUS, and as "no-pulsation" by PUS pulsation. The sensitivity and specificity for neurological deterioration was 100% and 95.1% in MRI decompression, 100% and 92.9% in PUS decompression, and 100% and 99.2% in PUS pulsation, respectively. CONCLUSIONS: This is the first report that the disappearance of spinal pulsation was associated with neurological deterioration. PUS was useful in determining the need of surgical evacuation for postoperative EH. PUS should be the first choice of examination in the event of postoperative neurological deterioration following a cervical laminoplasty. When the disappearance of pulsation is confirmed, an additional hematoma evacuation surgery should be considered immediately without undertaking MRI. LEVEL OF EVIDENCE: Level III.

Morphology of cervical periradicular fibrous sheath and nerve roots in relation to postoperative C5 palsy.

BACKGROUND CONTEXT: C5 palsy is a major complication of cervical spine surgery, however, its exact pathogenesis remains unclear. Some studies have shown that the superficial layer of the posterior longitudinal ligament extends laterally and forms the periradicular fibrous sheath (PFS), and envelopes the nerve roots. However, the anatomical relationship between the PFS and nerve root at each cervical level has not been fully revealed. PURPOSE: To examine the difference of the PFS that covers the nerve root at each cervical level, and to consider its potential in the onset of postoperative C5 palsy. STUDY DESIGN: Anatomical study of cervical dissection of 13 embalmed cadavers. METHODS: Thirteen human formalin-fixed cadavers were dissected from posterior approach, and were observed their cervical nerves bilaterally from C3 to C8 (the total number of nerves was 156). The bare area length (BAL), which is the distance between the medial posterior edge of the PFS and the bifurcation of the nerve and dura mater, was measured by using electronic calipers. Thus, BAL is the uncovered area of the nerve root by the PFS. We examined whether BAL significantly varied at each cervical level. RESULTS: We confirmed the PFS macro- and/or microanatomically in all cadavers. The average BAL gradually increased craniocaudally, and there was a significant step between that of C5 and C6 level. CONCLUSION: The average BAL of the C5 root was significantly shorter than that of C6, C7, and C8, suggesting that C5 root was more tightly anchored. This could be one reason for C5 palsy, making C5 nerve root vulnerable to the traction caused by the postoperative spinal cord shift. CLINICAL SIGNIFICANCE: This study provides clinicians an additional understanding of the anatomical factor of C5 palsy. Consideration of the anchoring effect of the PFS for nerve roots, release of the PFS could be a preventive procedure for C5 palsy.

An Experimental Rat Model of C5 Palsy Following Posterior Decompression Surgery of the Cervical Spine.

STUDY DESIGN: Basic in vivo research. OBJECTIVES: The aim of this study was to establish an animal model that is appropriate for analyzing the mechanisms of C5 palsy (C5P) and to clarify the structural and functional alterations of cervical roots following posterior decompression. SUMMARY OF BACKGROUND DATA: Although C5P is one of the major complications of cervical surgery, the exact pathogenesis of C5P remains unclear partly because of the lack of an appropriate animal model. Tethering of the cervical roots due to posterior cord shift following posterior decompression is thought to be one of the possible factors that cause C5P. METHODS: Twenty-eight Sprague-Dawley rats were divided into Group L (cervical laminectomy, N = 18) or Group S (sham surgery, N = 10) and examined up to postoperative day 14 (PO14). Posterior cord shift and the length of the anterior rootlets were quantified by computed tomography-myelogram images. Motor evoked potential (MEP) of the deltoid (C5, 6 innervated) and triceps brachii (C7-T1 innervated), mechanical allodynia, and grip strength of the forepaw (C7-T1 regulated) were measured. RESULTS: All anterior rootlets were elongated as the cord gradually shifted posteriorly postoperatively. The elongation rate of the C6 anterior rootlets was the highest (142% at PO14). The MEP latency of the deltoid was significantly delayed throughout all postoperative time points. However, significant delay in the latency of the triceps brachii was observed only on postoperative day 10. The withdrawal threshold of the forepaw did not change; grip strength of the forelimb decreased at PO14. CONCLUSION: This model was thought to be appropriate for analyzing the pathogenesis of C5P since our findings were comparable to the clinical course of C5P subsequent to posterior cervical decompression. Although a future study for clarifying histological and molecular alterations will be needed, tethering of the anterior rootlets due to posterior cord shift was suggested to be a probable mechanism causing C5P.Level of Evidence: 5.

Impact of morphological restoration of the spinal cord from the preoperative to early postoperative periods on C5 palsy development.

OBJECTIVE: C5 palsy (C5P) is a known complication of cervical decompression surgery. The tethering effect of the C5 nerve root following the posterior shift of the spinal cord is the most accepted pathologic mechanism for C5P development; however, this mechanism cannot fully explain C5P by itself in clinical practice. Separately, some studies have suggested that preoperative severe spinal cord compression and postoperative morphological changes in the spinal cord affect C5P development; however, no previous study has quantitatively addressed these possibilities. The aim of this study was to examine whether spinal cord morphology and morphological restoration after surgery affect C5P development. METHODS: The authors reviewed consecutive patients with degenerative cervical myelopathy who underwent laminoplasty including the C3-4 and C4-5 intervertebral disc levels. All participants underwent MRI both preoperatively and within 4 weeks postoperatively. To assess the severity of spinal cord compression, the compression ratio (CR; spinal cord sagittal diameter/transverse diameter) was calculated. As an index of morphological changes in the spinal cord during the early postoperative period, the change rate of CR (CrCR, %) was calculated as CRwithin 4 weeks postoperatively/CRpreoperatively × 100. These measurements were performed at both the C3-4 and C4-5 intervertebral disc levels. The study cohort was divided into C5P and non-C5P (NC5P) groups; then, CR and CrCR, in addition to other radiographic variables associated with C5P development, were compared between the groups. RESULTS: A total of 114 patients (mean age 67.6 years, 58.8% men) were included in the study, with 5 and 109 patients in the C5P and NC5P groups, respectively. Preoperative CR at both the C3-4 and C4-5 levels was significantly lower in the C5P group than in the NC5P group (0.35 vs 0.44, p = 0.042 and 0.27 vs 0.39, p = 0.021, respectively). Patients with C5P exhibited significantly higher CrCR at the C3-4 level than those without (139.3% vs 119.0%, p = 0.046), but the same finding was not noted for CrCR at the C4-5 level. There were no significant differences in other variables between the groups. CONCLUSIONS: This study reveals that severe compression of the spinal cord and its greater morphological restoration during the early postoperative period affect C5P development. These findings could support the involvement of segmental cord disorder theory, characterized as the reperfusion phenomenon, in the pathomechanism of C5P, in addition to the tethering effect.

Gap between flexion and extension ranges of motion: a novel indicator to predict the loss of cervical lordosis after laminoplasty in patients with cervical spondylotic myelopathy.

OBJECTIVE: Kyphotic deformity resulting from the loss of cervical lordosis (CL) is a rare but serious complication after cervical laminoplasty (CLP), and it is essential to recognize the risk factors. Previous studies have demonstrated that a greater flexion range of motion (fROM) and smaller extension ROM (eROM) in the cervical spine are associated with the loss of CL after CLP. Considering these facts together, one can hypothesize that an indicator representing the gap between fROM and eROM (gROM) is highly useful in predicting postoperative CL loss. In the present study, the authors aimed to investigate the risk factors of marked CL loss after CLP for cervical spondylotic myelopathy (CSM), including the gROM as a potential predictor. METHODS: Patients who had undergone CLP for CSM were divided into those with and those without a loss of more than 10° in the sagittal Cobb angle between C2 and C7 at the final follow-up period compared to preoperative measurements (CL loss [CLL] group and no CLL [NCLL] group, respectively). Demographic characteristics, surgical information, preoperative radiographic measurements, and posterior paraspinal muscle morphology evaluated with MRI were compared between the two groups. fROM and eROM were examined on neutral and flexion-extension views of lateral radiography, and gROM was calculated using the following formula: gROM (°) = fROM - eROM. The performance of variables in discriminating between the CLL and NCLL groups was assessed using the receiver operating characteristic (ROC) curve. RESULTS: This study included 111 patients (mean age at surgery 68.3 years, 61.3% male), with 10 and 101 patients in the CLL and NCLL groups, respectively. Univariate analyses showed that fROM and gROM were significantly greater in the CLL group than in the NCLL group (40.2° vs 26.6°, p < 0.001; 31.6° vs 14.3°, p < 0.001, respectively). ROC curve analyses revealed that both fROM and gROM had excellent discriminating capacities; gROM was likely to have a higher area under the ROC curve than fROM (0.906 vs 0.860, p = 0.094), with an optimal cutoff value of 27°. CONCLUSIONS: The gROM is a highly useful indicator for predicting a marked loss of CL after CLP. For CSM patients with a preoperative gROM exceeding 30°, CLP should be carefully considered, since kyphotic changes can develop postoperatively.

Significance of flexion range of motion as a risk factor for kyphotic change after cervical laminoplasty.

Kyphotic deformity is a rare but serious complication after cervical laminoplasty (CLP), and several studies have investigated its predictors. In these studies, a kyphotic Cobb angle of 0°-5° between C2 and C7 at a certain postoperative time-point was often used to detect kyphotic deformity. However, studies considering the amount of cervical lordosis loss compared to the preoperative measurement are scarce. This study aimed to elucidate risk factors for kyphotic change after CLP by comparing patients with and without marked loss of cervical lordosis postoperatively. The study population was divided into seven patients with and 92 patients without a loss of >10° of the C2-7 angle during the follow-up period compared to the preoperative measurements [cervical lordosis loss (CLL) group and no CLL (NCLL) group, respectively]; demographic characteristics, surgical information, preoperative radiographic sagittal parameters of the cervical spine, and posterior paravertebral muscle morphology evaluated by magnetic resonance imaging were compared between two groups. A univariate analysis revealed that the CLL group had significantly greater flexion range of motion (fROM) than the NCLL group (43.0° vs. 25.8°, P < 0.001); however, no statistical significance was identified for other parameters. The fROM had a high capacity to discriminate between the CLL and NCLL groups (area under the receiver-operating characteristic curve, 0.880; P < 0.001; 95% confidence interval, 0.589-0.974) with an optimal cutoff point of 37°. This study suggests that greater fROM is a risk factor for the development of kyphotic changes after CLP. For patients with preoperative fROM exceeding 40°, CLP should be carefully indicated.

Impact of Multifidus Muscle Swelling on C5 Palsy After Cervical Laminoplasty.

STUDY DESIGN: Retrospective radiological analysis OBJECTIVE.: The aim of this study was to identify the effects of posterior cervical muscle swelling on C5 palsy (C5P) by evaluating early postoperative magnetic resonance (MR) images. SUMMARY OF BACKGROUND DATA: Cervical laminoplasty is an established technique, but the risk of C5P after surgery has not been fully resolved. Studies have reported that lateral stretching and postoperative swelling of the multifidus muscle may cause stretching of the medial branches and cervical nerves. METHODS: A total of 214 C5 nerves of 107 consecutive patients who underwent laminoplasty were examined. We reviewed their demographic and surgical data and radiographic and MR images as parameters, including the axial cross-sectional area (CSA) of the posterior muscles. The patients and C5 nerves were divided into C5P and non-C5P groups. The parameters and changes were compared between the two groups to examine correlations with C5P. RESULTS: In demographic data, age, sex, history of smoking, diabetes mellitus, and preoperative Japanese Orthopedic Association scores were not significantly different between the groups. Only body mass index (BMI) was significantly higher in the C5P group. Regarding the surgical and imaging data, the number of laminoplasty, operative time, decompression trough width, cervical sagittal alignment, preoperative spinal cord rotation, and posterior shift of the spinal cord were not significantly different, but the multifidus CSA change ratio was significantly higher in the C5P group. Multiple logistic regression analyses revealed that the multifidus CSA change ratio and BMI were significant independent factors. CONCLUSION: Multifidus swelling is associated with C5P, possibly through traction of the C5 nerve via the medial branches of the cervical dorsal rami. The medial branch is the shortest of the dorsal rami and may have the largest effect by traction force. Therefore, a gentle maneuver of the deep posterior muscles during surgery is a potential countermeasure to prevent C5P. LEVEL OF EVIDENCE: 3.

The Evaluation of Indirect Neural Decompression After Lateral Lumbar Interbody Fusion Using Intraoperative Computed Tomography Myelogram.

BACKGROUND: The effect of indirect decompression after lateral lumbar interbody fusion (LLIF) is widely acknowledged; however, its details remain unclear. This study aimed to evaluate the immediate effects of indirect decompression just after LLIF cage placement but just before posterior instrumentation, using intraoperative computed tomography myelogram (iCTM). METHODS: Fifty-three levels from 28 patients undergoing LLIF with iCTM, were included in this retrospective study. Radiographic parameters were obtained from preoperative computed tomography myelogram and iCTM. Segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were compared preoperatively and intraoperatively to assess the neural decompression just after LLIF cage placement. Canal stenosis status during axial computed tomography myelogram was classified into 3 grades according to modified Schizas's grading to determine the necessity of additional posterior decompression procedures. The Oswestry Disability Index was obtained before and 3 months after the operation. RESULTS: Significant improvements in all radiological parameters of segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were observed just after LLIF cage placement. However, 11 (21%) levels had insufficient neural decompression status with iCTM grade (10 central canal and 1 lateral recess stenosis), requiring further direct posterior decompression. The difference in the improvement of Oswestry Disability Index between the decompression and nondecompression group was not significant, suggesting the validity of our decision. CONCLUSIONS: Detailed evaluation with iCTM revealed that adequate indirect decompression with LLIF was not always obtained, validating the intraoperative decision of further posterior decompression. This procedure, LLIF with iCTM, may reduce the risk of unnecessary direct decompression and reoperation after insufficient indirect decompression.