INTRODUCTION
Minimally invasive spinal surgery, particularly unilateral biportal endoscopy, has gained popularity due to advantages like reduced tissue disruption, shorter hospital stays, and faster recovery. While complications inherent to open surgery can still occur, their incidence is significantly lower. However, the increasing use of these techniques necessitates heightened clinician awareness, as rare complications can carry significant morbidity. Delay in prompt intervention can have serious medio-legal implications [1].
We present a rare and complex complication after unilateral biportal endoscopic (UBE) thoracic decompression: recurrent postoperative epidural hematoma (3 episodes). To our knowledge, this is the first report of delayed and recurrent hematoma following UBE surgery.
CASE REPORT
Figure 1 provides a summarized overview of the patient’s surgical course, including all four procedures. This may facilitate understanding of the case report presented below.
A 78-year-old female with no comorbidities and a normal coagulation profile presented with lower back pain, bilateral inguinal and anterior thigh pain (visual analogue score [VAS] 8/10), and neurogenic claudication after walking 10 m. She had a history of L3–5 interbody fusion surgery, which provided symptom relief for nearly 12 years.
Her imaging (Figure 2A) showed new stenosis at D11–12 and L1–2. She had UBE decompression surgery at both levels, which was uneventful. The patient was mobilized the next day without complications. Her thigh pain improved significantly, with the VAS score dropping from 8/10 to 2/10. Postoperative magnetic resonance imaging (MRI) (Figure 2B) confirmed excellent decompression.
On postoperative day 5, the patient reported progressive lower extremity weakness (less than grade 3/5 on the Medical Research Council [MRC] scale) and sensory loss at the L1 level. Emergency MRI (Figure 3A) showed a delayed postoperative spinal epidural hematoma (DPOSEH) compressing the spinal cord. The patient underwent urgent hematoma evacuation using UBE. Operative findings confirmed the hematoma, but no major bleeder or dural tear was found. Haemostatic matrix sealant (CollaStat, Dalim, Korea) was used, and all small bleeders were coagulated. After the second surgery, the patient improved, regaining bilateral lower limb power to MRC grade 5/5 and mobilizing well with walker support, without radiating pain. She was started on tranexamic acid. The follow-up MRI (Figure 3B) showed no residual compression of the thecal sac. Her coagulation profile and blood parameters remained normal throughout.
Despite successful hematoma removal, the patient developed recurrent symptoms on postoperative day (POD) 13. A fresh MRI (Figure 4A) showed a newly accumulated hematoma. She underwent another emergency re-exploration, and no major bleeder was found. Meticulous hemostasis was achieved to the best of our capability. Postoperatively, the patient improved neurologically and proper ambulation with a walker was possible by POD 14 and the check MRI was also satisfactory (Figure 4B).
Unfortunately, on POD 16 from index surgery, the patient developed right lower limb weakness and radiating thigh pain, worse during ambulation. The hematoma reaccumulated for a third time, requiring a fourth surgery (Figure 5). Pain reduction in the supine position suggested occult microinstability, possibly causing persistent microbleeding or preventing clot stabilization, leading to recurrent epidural hematomas without a diagnosable bleeding diathesis.
During the fourth surgery, in addition to hematoma evacuation, we performed UBE thoracic interbody fusion at the D11–12 level to address the potential instability. The postoperative course was uneventful (Figures 6 and 7), and the patient remained symptom-free at 12-month follow-up. Our protocol mandates drain removal on POD 2 or when output is <15 mL/6 hours, whichever is later. This was followed after the first 2 surgeries; however, the third recurrence occurred with the drain in situ. This study includes a retrospective technical analysis and a case report.
1. Surgical Technique: Thoracic Interbody Fusion With UBE Technique (Supplementary Video Clip 1)
1) Docking point for instruments and incisions
Dr JSH, the senior author being a right-handed surgeon preferred a left-sided approach. Using anteroposterior C-arm fluoroscopy, the inferior cranial lamina was identified as the docking point. Two incisions were made on the midline of the proximal and distal pedicles (Figure 8). After confirming correct portal placement, radiofrequency coagulator was used to expose the cranial lamina, spinous process base, and interlaminar space.
2) Decompressive lamino-flavectomy
A round diamond burr was used to carefully remove the cranial lamina down to the ligamentum flavum, avoiding compression. The base of the spinous process was resected to facilitate safe instrument manipulation and minimize spinal cord compression risk. The ligamentum flavum was detached with a 2-mm Kerrison rongeurs.
3) Extensive foraminotomy and interbody cage insertion
A liberal foraminotomy was performed on the ipsilateral side, involving extensive drilling and complete excision of the facet joints to create a trajectory for interbody cage insertion. The disc space was prepared using small pituitary rongeurs and curettes under endoscopic visualization. A polyetheretherketone cage was inserted obliquely under fluoroscopic guidance (Figures 9 and 10). Final stabilization was achieved with percutaneous screw fixation under C-arm guidance.
4) Perioperative management
Throughout this case, we took meticulous surgical precautions to identify and address bleeding sources. We collaborated with internal medicine to investigate underlying causes of the recurrent hematoma and utilized tranexamic acid, only to find no remedy. By the third recurrence, we suspected occult microinstability was not allowing clot stabilization, particularly given that D11–12 is a transitional zone. Spinal fusion was considered as a final recourse to stabilize epidural vasculature and mobile facets and potentially mitigate further bleeding. To minimize delayed intramuscular bleeding, we implemented a 3-day postoperative strict bed rest protocol.
5) Ethical approval and informed consent
The procedures were conducted in accordance with the ethical standards of the institutional research committee and the Declaration of Helsinki. Written informed consent was obtained from the patient for the use of clinical data and publication of this case report and any accompanying images.
DISCUSSION
Spinal epidural hematoma (SEH) presents with a wide spectrum of clinical manifestations, ranging from asymptomatic to severe neurological deficits with prevalence ranging from 33% to 100% on MRI. The overall incidence of symptomatic SEH (SSEH) is estimated to be 0.52% [2] and those requiring reoperation is 0.2% [3].
Minimally invasive spine surgery decreases the likelihood of postoperative SEH (PSEH) due to the limited creation of dead space, Ikuta et al. [4] found that 10 of 30 patients developed radiologic postoperative hematomas following microscopic discectomy, of those, 3 experienced mild, self-limiting symptoms.
UBE surgery reduces SSEH risk compared to microscopic/tubular surgeries due to its inherent advantages in minimizing blood loss and optimizing hemostasis. Continuous pressurized irrigation prevents clot formation and aids bleeding point identification. High-definition endoscopic visualization allows for precise dissection and coagulation using radiofrequency ablation. Additionally, diamond-tipped burrs minimize bone bleeding by creating smooth, cauterized surfaces.
Yet, UBE technique is not immune to occurrence of PSEH, Wang et al. [5] reported an incidence of 0.27% for PSEH for UBE for lumbar stenosis whereas in the study of Ahn et al. [6] of 158 UBE lumbar decompressions, 24.7% developed radiologic PSEH, of these, only 2 underwent revision surgery for SSEH.
While SSEH incidence varies by surgical site (thoracic, 0.84%; lumbar, 0.63%; cervical, 0.32%), the thoracic spine, with its limited cord space, is most commonly affected [7]. Domenicucci et al. [8] found C6 and T11 to be the most frequent SSEH locations, aligning with our case report.
1. Patient-Related Factors
• Age older than 60 years
• Male sex
• High body mass index [12]
• Rh-positive blood type
• Hypertension, especially large increase in blood pressure during extubation [12]
• Preoperative anemia (hemoglobin < 10 g/dL)
• Alcohol consumption: more than 10 units per week
2. Surgery-Related Factors
• Minimally invasive surgery
• Posterior approach
• Surgery at the thoracic spine
• Involvement of more than 5 operative levels
• Multilevel procedures: more than one intervertebral disc
• Prolonged surgical time
• Significant blood loss: blood loss > 1 L
• Intraoperative blood pressure fluctuations [13]
• Lumbar drains have not been demonstrated to be of any benefit in preventing hematoma formation in at least 4 studies [3,10,14,15]
• Zeng et al. [13] found 9 cases in this study developed SSEH before the drainage tube was removed. And 7 of them were found to have hematoma of uncoagulated blood. Obstruction of drainage tubes should be the primary reason for the SSEH. Blood clots/gel foam, infolding of tubing/necrotic debris could block the drainage tube.
3. Medication-Related Factors
• Use of preoperative nonsteroidal anti-inflammatory drugs
• Use of anticoagulants
4. Postoperative Factors
• International normalized ratio > 2.0 within the first 48 hours
Most descriptions of delayed epidural hematoma found in literature are described for cranial epidural hematomas [16-18]. Though not very rare, the understanding of delayed SEH comes from very few studies [19]. Lawton et al. [20] noted an average interval from symptom onset to surgery was 23.4 hours. Uribe et al. [19] defined DPOSEH as those occurring after POD 3.
DPOSEH is an exceedingly rare cause of delayed clinical deterioration following spinal surgery. One of the probable causes for DPOSEH can be that unlike arterial bleeds, venous bleeding, can be slow and insidious, delaying symptom onset. Rupture of valveless veins in the internal vertebral plexus, even by the slightest change of posture during sleep, turning or coughing, or due to Valsalva's maneuverer, can cause slow epidural bleeding [21].
The underlying mechanisms for the recurrence of the epidural hematoma in our case are not well-understood but it may be related to ongoing microbleeding or a failure of the normal hemostatic mechanisms. Spinal decompression surgeries, such as discectomy or laminectomy, can alter the structural integrity of the spine by removing bone or soft tissue, potentially leading to increased mobility or instability of the vertebral segments. This instability may result in abnormal micro motion, which can place mechanical stress on surrounding tissues, including blood vessels. The epidural venous plexus, which is a network of thin-walled veins in the epidural space, is particularly vulnerable to injury due to its delicate structure and proximity to the spinal canal. Vascular injury to the epidural venous plexus can occur due to mechanical disruption during surgery or postoperative instability, leading to hemorrhage and the accumulation of blood in the epidural space. While the exact relationship between postoperative spinal instability and epidural hematoma formation is not fully established, there is evidence to suggest that mechanical stress and vascular trauma play a role in this process. Our patient's hematoma recurrence, despite initial successful evacuation and hemostasis, may also raise the possibility of an underlying undiagnosed vascular or coagulation disorder [3]. Table 1 summarizes key papers on DPOSEH in literature.
While a single case report cannot definitively prove fusion's efficacy for recurrent SSEH with undetectable causes, it highlights fusion as a potential management option for consideration in such cases.
CONCLUSION
Spinal fusion can be considered for recurrent SSEH or DPOSEH, especially with intractable bleeding. The authors’ choice of a more extensive approach highlights the complexity of managing such rare complications. Conventional strategies may be insufficient for durable resolution. Their willingness to explore alternative treatments shows their commitment to optimizing patient care and adapting surgical plans to each unique case.
Given that all controllable factors for preventing bleeding were consistent across surgeries, except for the final instrumented stabilization, we believe the fusion surgery prevented further hematoma recurrence, with the patient serving as his own control.
The scarcity of literature on recurrent epidural hematoma makes defining predictive factors or standardized treatment difficult. This case highlights the potential for serious complications, including hematoma recurrence, even after minimally invasive spinal procedures.
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