The Incidence,Grading,and Treatment of Spinal Epidural Hematoma After Cervical Laminoplasty: A Retrospective Study Based on Postoperative MRI of 207 Patients

Abstract

Study Design

Retrospective cohort study.

Objective

To determine the incidence, grading, management, and clinical impact of postoperative spinal epidural hematoma (SEH) following cervical laminoplasty (LAMP) for degenerative cervical myelopathy (DCM).

Methods

This study analyzed 207 DCM patients who underwent LAMP between August 2022 and February 2024. Postoperative magnetic resonance imaging (MRI) within 48 h was used to assess SEH, graded based on radiological compression and clinical symptoms. A 3-month MRI evaluated epidural scar formation. Patient demographics, laboratory and operative variables, and clinical outcomes were compared between the SEH and non-SEH groups, and multivariable logistic regression analysis was performed to identify independent risk factors for SEH.

Results

SEH was identified in 72 patients (34.8%), of whom 71 (98.6%) were Grades 1-3 and managed conservatively. One patient (0.48%) developed neurological symptoms (Grade 4) requiring percutaneous drainage and achieved full recovery. No patients developed Grade 5 SEH. At the 3-month follow-up, epidural scar formation was observed in 5 (7.7%) patients in the SEH group and 3 (2.6%) in the non-SEH group (P = .141). Clinical outcomes, including Japanese Orthopaedic Association (JOA) scores, and neck Numerical Rating Scale (NRS) scores were comparable between groups at the 3-month follow-up. No independent predictors of SEH were identified.

Conclusions

MRI-detectable postoperative SEH was observed in more than one-third of patients after LAMP, and most cases were asymptomatic. The proposed grading system may support stratified management. Clinical outcomes were comparable between groups, and epidural scar formation was more frequent in the SEH group, but not statistically significant.

Keywords

degenerative cervical myelopathy laminoplasty postoperative spinal epidural hematoma grading system management

Introduction

Degenerative cervical myelopathy (DCM) is a progressive degenerative disease and the most common cause of cervical spinal cord dysfunction.^1,2 Surgical intervention should be performed in patients with moderate and severe DCM and in those with progressive disease.² Laminoplasty (LAMP) has been well established as an effective treatment for multilevel DCM.³ However, its associated complications should not be overlooked. Postoperative spinal epidural hematoma (SEH) is a potentially serious complication.

Previous studies have primarily focused on postoperative symptomatic spinal epidural hematomas (SSEH), which are defined as postoperative SEH requiring reoperation. A meta-analysis showed that the incidence of SSEH in cervical spine surgery was approximately 0.32%, with a higher incidence observed following posterior surgery.⁴ In our hospital, the overall incidence of SSEH was 0.24% following cervical spine surgery between 2009 and 2019.⁵ However, the true incidence of postoperative SEH may be underestimated, as asymptomatic cases are often detected only on imaging.^6,7 Therefore, a stratified management strategy based on the severity of SEH may be necessary. Chang et al⁸ emphasized the importance of timely decompression within 6 h for patients with motor deficits and proposed a flowchart to guide the management of postoperative SSEH. Nevertheless, evidence regarding the clinical and radiological characteristics of postoperative SEH, especially asymptomatic and mild cases, remains limited.

Therefore, the primary objective of this study was to determine the incidence of SEH following LAMP and to establish a grading system based on clinical and radiological findings. In addition, we aimed to evaluate the clinical outcomes and potential risk factors associated with postoperative SEH.

Methods

Study Cohort

This study was approved by the Medical Research Ethics Committee of Peking University Third Hospital (IRB No. IRB00006761-M2023296). We retrospectively reviewed consecutive patients with DCM, who underwent LAMP performed by a single senior surgeon at our hospital between August 2022 and February 2024.

The inclusion criteria were as follows: (1) diagnosis of DCM affecting 3 or more spinal levels confirmed by relevant clinical and imaging findings, (2) completion of magnetic resonance imaging (MRI) examinations both preoperatively and within 48 h postoperatively, and (3) age 18 years or older. The exclusion criteria included posterior fusion with fixation, previous history of spinal fractures, tumors, infections, spinal deformities, metabolic bone diseases, and previous spine surgery.

LAMP was performed as described by Hirabayashi and Satomi.³ All patients retained postoperative drainage for approximately 24 h, which was removed if the volume was less than 50 mL within 24 h. The patients were instructed to wear a Philadelphia cervical collar for 2 weeks postoperatively. Complete perioperative documentation was available. Patients were followed up at 3 months and 1 year postoperatively, with a scheduled follow-up MRI 3 months postoperatively.

Grading of SEH

MRI scans were obtained preoperatively and within 48 hours postoperatively. Postoperative MRI findings were used to determine the presence and severity of SEH. SEH was defined as a posterior epidural collection demonstrating MRI signal characteristics consistent with acute or early subacute hematoma on T1- and T2-weighted images. These characteristics included internal signal heterogeneity and time-dependent changes in signal intensity, with acute lesions typically appearing iso- to hypointense on T1-weighted images and hyperintense on T2-weighted images, and subacute lesions demonstrating hyperintensity on both T1- and T2-weighted images.⁹ Homogeneous fluid collections without internal signal heterogeneity were considered seroma and were not classified as SEH. Two independent surgeons reviewed all postoperative MRI scans to evaluate the SEH. Interobserver agreement was assessed using Cohen’s κ coefficient. In cases of disagreement, a third senior reviewer was consulted to reach a consensus. Classification of postoperative SEH was modified from the MRI-based grading system proposed by Takeuchi et al.⁶

SEH was classified as follows (Figure 1):

• Grade 1: No dural sac compression

• Grade 2: Compression with visible posterior cerebrospinal fluid (CSF)

• Grade 3: Posterior CSF effaced without neurological deterioration

• Grade 4: Progressive neurological symptoms without motor weakness

• Grade 5: Neurological deficit with ≥1-grade reduction in manual muscle testing (MMT).

Figure 1.

Grading system of spinal epidural hematoma (SEH) after laminoplasty. (A) No evidence of SEH on MRI. (B-F) Grade 1 to Grade 5 SEH

Grading of Epidural Scar Formation

Epidural scar formation was assessed using MRI 3 months postoperatively. Scar grading was aligned with the SEH classification (Figure 2).

• Grade 1: No dural sac compression

• Grade 2: Compression With Visible Posterior CSF

• Grade 3: Posterior CSF effaced

Figure 2.

Grading system of Scar formation after laminoplasty. (A) No evidence of Scar formation. (B-D) Grade 1 to Grade 3 Scar formation

Data Extraction

Patient demographics (age, sex, body mass index (BMI)) and clinical characteristics (number of operated laminae, comorbidities, antiplatelet use) were recorded. Neck pain intensity was measured using an 11-point Numerical Rating Scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain).¹⁰ Neurological function was evaluated using the Japanese Orthopaedic Association (JOA) score.¹¹ The JOA recovery rate (JOARR) was calculated as: (postoperative JOA − preoperative JOA)/(17 − preoperative JOA) × 100, according to the method described by Hirabayashi et al.¹²

To explore the risk factors for SEH, laboratory examinations including blood platelet count, activated partial thromboplastin time (APTT), partial thromboplastin time (PT), and international normalized ratio (INR) were performed. Clinical data including operating time, intraoperative blood loss, and drainage duration or volume were extracted.

Management of the SEH

For asymptomatic patients (Grades 1, 2, and 3), no neurological symptoms were observed, and patients were closely monitored for any further deterioration of neurological symptoms and deficits. For Grade 4 patients, the drainage tube was checked. If drainage cannot be performed, percutaneous puncture drainage was performed (Figure 4). Emergency hematoma evacuation surgery was indicated for patients with Grade 5 hematoma.

Statistical Analysis

Continuous variables were assessed for normality. BMI was normally distributed and is presented as mean ± standard deviation (SD) and compared using the independent t-test. Other continuous variables were non-normally distributed and are presented as medians with interquartile ranges (IQRs) and compared using the Mann–Whitney U test. Categorical variables were compared using the chi-square test, with Fisher’s exact test applied when one or more expected cell counts were <5.

To further explore independent risk factors for postoperative SEH, a multivariable logistic regression model was constructed. The following clinically relevant variables were entered into the model: age, sex, antiplatelet drug use, INR, operating time, and total postoperative drainage volume. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Comparisons of epidural scar formation between groups were performed using Fisher’s exact test due to the small number of events. Logistic regression analysis was not conducted for scar formation because complete separation (zero events in one group) precluded reliable estimation of effect sizes. A two-sided P value <.05 was considered statistically significant.

Results

Participant Characteristics

A total of 239 consecutive patients who underwent LAMP for DCM were reviewed, and 207 were included in the analysis (Table 1). Our cohort consisted of 147 males (71.3%) and 60 females (28.7%) with a median age of 57 years (interquartile range, IQR: 49-65 years). The median preoperative neck NRS score was 2 (0-4), and the median JOA score was 12.5 (11.0-14.0). Follow-up data were available for 179 patients (86.5%) at 3 months and for 170 (82.1%) patients at 1 year postoperatively (Figure 3).

Table 1.

Demographic and Baseline Clinical Characteristics of Patients With and Without SEH

	Non- SEH Group(n = 135)	SEH Group (n = 72)	P
Age (yrs), median (IQR)	57 (50-66)	55 (48-64)	.260
Sex (n, female/male)	36/99	24/48	.314
BMI (mean ± SD) (kg/m²)	24.7 ± 2.8	25.0±.3.8	.529
Number of operated laminae (n), median (IQR)	5 (5-5)	5 (5-5)	.928
Comorbidities (n, %)
Hypertension	37 (27.4%)	24 (33.3%)	.373
Diabetes mellitus	16 (11.9%)	7 (9.7%)	.642
Ischemic heart disease	10 (7.4%)	2 (2.8%)	.175
Renal failure	0	0	#NA
Smoke history	10 (7.4%)	10 (13.9%)	.133
Antiplatelet drugs use	8 (5.9%)	3 (4.2%)	.591

Abbreviations: IQR: Interquartile Range; n: Number of patients; SD: Standard deviation; #NA = Not available; SEH: Spinal epidural hematoma; BMI: Body mass index.

Figure 3.

Patient selection flow chart

Incidence and Clinical Manifestations of SEH

Interobserver agreement for SEH grading between the 2 reviewers was almost perfect (Cohen’s κ = 0.871). Postoperative MRI revealed SEH in 72 patients (34.8%). Among these 72 patients, 48 (66.7%) were classified as Grade 1, 11 (15.3%) were Grade 2, and 12 (16.7%) were Grade 3. None of the patients with Grades 1-3 experienced neurological deterioration.

One patient (1/207, 0.48%) initially showed SEH on MRI 2 days after surgery without neurological symptoms. On postoperative day 9, the patient developed arm pain, and a repeat MRI revealed a posterior epidural fluid collection with signal characteristics consistent with seroma, causing progression of spinal cord compression. Percutaneous puncture drainage was performed, resulting in symptom relief (Figure 4). No patients developed Grade 5 SEH.

Figure 4.

Representative case of postoperative Grade 4 spinal epidural hematoma (SEH). (A and B) Percutaneous puncture drainage performed for a Grade 4 SEH. (C) Preoperative MRI of the patient, (D) Postoperative MRI, (E) MRI on postoperative day 9. (F) MRI at the 3-month follow-up

At the 3-month follow-up, epidural scar formation was observed in 5 patients (7.7%) in the SEH group and in 3 (2.6%) in the non-SEH group. Due to the small number of events, the difference between groups did not reach statistical significance (P = .141) (Table 2).

Table 2.

Grade of Epidural Scar Formation at the 3-Month Follow-Up

		Non-SEH (n = 114)	SEH (n = 65)	P
Grade of scar formation (n, %)	1	3 (2.6%)	1 (1.5%)	1.000
	2	0 (0%)	3 (4.6%)	.046^a
	3	0 (0%)	1 (1.5%)	.363
	Total	3 (2.6%)	5 (7.7%)	.141

^aSignificant.

Abbreviation: SEH, spinal epidural hematoma.

Clinical Outcomes

Patients were divided into non-SEH (n = 135) and SEH (n = 72) groups to evaluate clinical outcomes. Preoperative neck NRS (median [IQR], 2 [0-3] vs 1 [0-4], P = .960) and JOA scores (12.5 [11.0-14.0] vs 12.5 [10.5-14.0], P = .612) were comparable between groups. Clinical outcomes were comparable between the 2 groups at both the 3-month and 1-year follow-ups (Table 3). Among the 5 patients with epidural scar formation in the SEH group, neurological recovery remained favorable, with a median JOA score of 15.5 and a median JOARR of 66.7% at the 3-month follow-up.

Table 3.

Comparison of Neck Pain (NRS) and Neurological Function Between the Non-SEH and SEH Group

	Non-SEH (n = 135)	SEH (n = 72)	P
Preoperative neck NRS	2 (0-3)	1 (0-4)	.960
Neck NRS at 3 months	0 (0-2)	0 (0-2)	.370
Neck NRS at 1 year	0 (0-0)	0 (0-0)	.994
Preoperative JOA	12.5 (11.0-14.0)	12.5 (10.5-14.0)	.612
JOA at 3 months	15.5 (14.0-16.5)	15 (13.5-16.0)	.184
JOA at 1 year	16 (15.5-16.5)	16 (15.5-16.5)	.654
JOARR at 3 months (%)	62.5 (25.0-77.0)	62.5 (47.5-75.0)	.723
JOARR at 1 year (%)	75.0 (58.8-84.6)	75.0 (66.7-85.7)	.748

Values are presented as median (IQR).

Abbreviations: IQR, interquartile range; NRS, numerical rating scale; JOA, Japanese Orthopaedic Association score; JOARR, JOA recovery rate; SEH, spinal epidural hematoma.

Risk Factors for Postoperative SEH

To explore potential risk factors for postoperative SEH, baseline demographic, laboratory, and operative variables were compared between groups in univariate analyses. No significant differences were observed in demographic data, comorbidities, antiplatelet drug use, or coagulation laboratory parameters between the non-SEH and SEH groups (Tables 1 and Table 4). Operative variables, including surgery duration, intraoperative blood loss, and postoperative drainage volume or duration, were also similar between the 2 groups. In multivariable logistic regression analysis, no independent predictors of SEH were identified (Table 5).

Table 4.

Comparison of Laboratory Parameters, Operative Variables, and Drainage Characteristics Between the Non-SEH and SEH Group

	Non-SEH group (n = 135)	SEH group (n = 72)	P
Platelet count (×10⁹/L)	224.0 (118-252)	220 (179.0-250.0)	.767
PT (s)	10.8 (10.4-11.3)	10.8 (10.2-11.1)	.474
APTT (s)	31.0 (29.0-33.0)	31.0 (29.4-32.8)	.971
INR	1.00 (0.96-1.05)	1.00 (0.95-1.00)	.275
Operating time (min)	93.0 (85.0-105.0)	94.0 (87.0-104.8)	.830
Intraoperative blood loss (m)	100.0 (50.0-100.0)	100.0 (50.0-100.0)	.736
Total volume of drainage (ml)	90.0 (40.0-175.0)	60.0 (30.0-135.0)	.084
Duration of drainage (days)	2.0 (1.0-2.0)	1.0 (1.0-2.0)	.227

Abbreviations: PT, prothrombin time; APTT, activated partial thromboplastin time; INR, international normalized ratio; IQR, interquartile range; SEH, spinal epidural hematoma.

Table 5.

Multivariable Logistic Regression Analysis for Postoperative SEH

	OR	95% CI	P
Age	0.979	0.954-1.004	.099
Sex	1.449	0.756-2.779	.264
Antiplatelet drug use	0.927	0.227-3.777	.916
INR	0.187	0.002-15.338	.456
Operating time (min)	0.999	0.983-1.016	.903
Total volume of drainage (ml)	0.999	0.996-1.002	.713

Abbreviations: OR, odds ratio; CI, confidence interval; INR, international normalized ratio; SEH, spinal epidural hematoma.

Discussion

Postoperative SEH is a potentially serious but frequently under-recognized complication of cervical spine surgery. In this retrospective cohort of 207 patients who underwent LAMP for DCM, we performed early postoperative MRI to detect SEH and a combined radiological-clinical grading system was applied. Among the 72 patients (34.8%) with MRI-detected SEH, 71 (98.6 %) were classified as Grades 1-3 and successfully managed with close observation; only one patient (1.4 %) progressed to Grade 4 requiring percutaneous drainage, and no patients reached Grade 5. These findings enhance our understanding of postoperative management and prognostication in patients with DCM undergoing LAMP.

The incidence of postoperative SEH detectable on MRI was 34.8% in our study. Shin et al⁷ reported an SEH incidence of 46.6% (27/58) on MRI before hospital discharge after LAMP. Takeuchi et al⁶ observed a 69.6% (48/69) incidence of SEH 24 hours after LAMP. These results demonstrate a high incidence of postoperative SEH, with most SEHs being asymptomatic, which is substantially higher than the incidence of SSEH, ranging from 0.1% to 1.5% in cervical spine surgery.^5,13-15 Anatomically, the posterior epidural space created after LAMP provides a sufficient reserve volume to accommodate small hematomas without causing significant cord compression, which may explain the high rate of asymptomatic cases.

Our findings also suggest that a stratified management strategy based on clinical severity may be useful. In our cohort, the patient who developed delayed epidural fluid collection consistent with seroma was managed successfully with percutaneous puncture drainage. Similarly, Shin et al⁷ reported that 9 patients (4.9%, 9/185) underwent ultrasonography-guided hematoma aspiration because of no change in numbness and prolonged pain for more than a week, and 3 (1.6%, 3/185) patients underwent emergency hematoma evacuation surgery with neurological symptoms such as motor deficits. Chang et al⁸ have suggested timely decompression for patients with motor defects and monitoring for patients without motor defects. Our findings indicated that percutaneous drainage may be effective for Grade 4 SEH when neurological symptoms are present, whereas emergency decompression surgery is warranted for patients with motor deficits (Grade 5). Therefore, a grading system incorporating radiological compression and clinical progression of SEH after LAMP may provide a structured framework to assist clinical decision-making.

Epidural scar formation is a late complication that might be associated with postoperative SEH. In our cohort, 8 patients had epidural scar formation at the 3-month follow-up. Takeuchi et al⁶ reported that 10% of the patients remained in the severe scar formation group at the final follow-up after LAMP, with a trend toward worse outcomes. Our results showed that more epidural scar formation was observed in the SEH group (7.7% vs 2.6%, P = .141). However, this difference did not reach statistical significance, likely due to the limited number of events. SEH may act as both a physical substrate and a biochemical environment that can promote granulation tissue maturation and collagen deposition, leading to scar formation.¹⁶ Stringent hemostasis and reduction of unnecessary epidural dead space may be strategies to decrease epidural scar formation.¹⁷ The potential relationship between postoperative SEH and subsequent epidural scar formation should be interpreted cautiously and requires further investigation in larger cohorts.

Previous studies have identified factors such as the number of operated levels, ossification of the posterior longitudinal ligament (OPLL), higher comorbidity burden, and use of nonsteroidal anti-inflammatory drugs (NSAIDs) as potential risk factors for SSEH.^5,14 However, in the present study, there were no significant differences in demographics, comorbidities,or antiplatelet use, or intraoperative variables (e.g., blood loss and operative time) between patients with and without SEH. Furthermore, postoperative drainage duration and volume were also comparable between groups. Previous studies suggested that perioperative antiplatelet therapy does not increase the risk of SSEH.^18,19 Otsuki et al²⁰ also found no difference in SSEH incidence between patients using closed-suction and non-suction drains after LAMP, although the drainage volumes were higher in non-suction systems. Overall, these findings suggest that commonly evaluated perioperative variables may have limited predictive value for SEH development, and that maintaining drainage for over 24 h postoperatively does not appear to influence its incidence.

This study had some limitations. First, this was a retrospective single-center study, which may have introduced a selection bias and limited the generalizability of the findings. Second, although the proposed SEH grading system is potentially clinically useful, the small number of symptomatic cases limits the strength of the management implications derived from this study. Further validation in prospective or multicenter studies is therefore warranted. Third, the relatively small number of symptomatic SEH cases limited the ability to identify significant predictors through multivariable analysis.

Conclusions

MRI-detectable postoperative SEH was observed in more than one-third of patients after LAMP, but most cases are asymptomatic. The proposed radiological-clinical grading system may provide a structured framework for stratified postoperative management. Most cases can be safely managed, leading to favorable neurological recovery and overall prognosis. Although epidural scar formation occurred more frequently in patients with SEH, the difference was not statistically significant and should be interpreted cautiously.

Footnotes

ORCID iDs

Zexiang Liu

Ben Wang

Ruomu Qu

Ethical Considerations

The study protocol was approved by the institutional research ethics committee (IRB00006761-M2023296), according to the principles of the Declaration of Helsinki. The institutional review board granted a waiver of informed consent because of the retrospective nature of the study.

Author Contributions

Zexiang Liu, Ben Wang and Ruomu Qu were responsible for data acquisition, data analysis, and drafting and revising the manuscript. Long Wang was responsible for data acquisition. Liang Jiang, as the corresponding author, was responsible for the study conception and design, supervision of the research process, critical revision of the manuscript, and overall quality assurance. All authors have read and approved the final version of the manuscript.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by Peking University Third Hospital (JT-0019).

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

Research data supporting this publication are available from the Peking University Third Hospital, but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly.*

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