Rare Huge Epidural Hematoma Associated with Refracture of Kummell Disease: A Case Report and Literature Review

Background Kummell disease combined with huge spinal epidural hematoma is a very rare phenomenon, and its potential pathogenesis and natural course remain unclear. Case description We describe a rare case of Kummell disease with huge spinal epidural hematoma. A 75-year-old male was diagnosed with osteoporotic vertebral compression fractures and was treated conservatively. After suffering minor trauma again 8 days ago, he presented unbearable low back pain and activity restriction. Lumbar MRI showed that L1 vertebral had re-fracture and intervertebral vacuum cleft, and a huge spinal epidural hematoma extending from T12- L1. Due to the patient had no neurological decits and unbearable low back pain, percutaneous vertebroplasty was performed, and pain was relieved signicantly. The follow-up MRI showed that the hematoma almost disappeared 7 days after the operation. Conclusion Although extremely rare, there is a possibility of spinal epidural hematoma after re-fracture of Kummell disease, and it could be further conrmed via MRI and pathological examination. Timely operation is recommended, and the results are usually favorable.


Introduction
With the advent of the global population's aging, more osteoporotic vertebral compression fracture occurs, often accompanied by severe acute low back pain and activity restriction 1 . Clinically, the symptoms of most patients can be relieved gradually after several weeks of conservative treatment 2 , but Kummell disease is a rare type of osteoporotic vertebral compression fracture, which gradually appears vertebral collapse and kyphosis, and its occurrence may be related to vertebral ischemic necrosis 3 . Huge spinal epidural hematoma (SEH) combined with Kummell Disease is extremely rare. The pathogenesis and natural course of SEH combined with Kummell Disease remain unclear. In this case study, we describe a Kummell patient with huge SEH and review the literature to explore its potential pathogenesis, natural course, and treatment.

Case Description
A 75-year-old male patient experienced a persistent low back pain and movement restriction after a slight fall 3 months ago. He was transferred from a traditional oriental hospital to the emergency room of our hospital. Here, X-ray examination showed that osteoporotic compression fracture of L1 (Fig. 1A). He was treated conservatively such as bed rest, analgesics, and oral calcium supplements. However, he was admitted to our hospital with suffered minor trauma again 8 days ago and complained of severe and unbearable pain in the lower back and impaired mobility. On examination, the patient presented with signi cant tenderness and percussion in the L1 spinous process and paraspinal, especially during exion and extension. Neurological examination was negative and laboratory examination results were within the normal range. The patient reported no history of heart disease, cerebrovascular disease, or hypertension. X-ray examination showed compression fracture of L1 vertebra and the compression degree was more than 50% (Fig. 1B), CT demonstrated that fracture of L1 characterized by vertebral vacuum cleft ( Fig. 1C-D), MRI of the thoracolumbar spine revealed that collapse of L1 vertebra, vacuum cleft lled with uid, and a huge soft tissue of ventral epidural of spinal cord extended from T12 to L1 on T1-weighted images showed low signal intensity, while T2-weighted images showed high signal intensity ( Fig. 1E-F). The patient had severe osteoporosis with a T-score on the bone marrow densitometry of -3.80.
So, he was considered as re-fracture of Kummell Disease. Since the intractable pain unrelieved by conservative treatment, a unilateral percutaneous vertebroplasty and intraoperative biopsy were performed, and then approximately 5 ml of bone cement carefully injected into the vacuum space of the vertebral body under X-ray examination. After the operation, the pain was relieved immediately, and the patient could walk independently with a lumbar brace. Postoperative X-ray showed that the bone cement diffused and lled well in the L1 vertebral body (Fig. 1G-H), and pathological examination demonstrated bone marrow tissue (Fig. 2). Postoperative MRI revealed that the hematoma almost completely disappeared on at 7 days follow-up ( Fig. 1L-K).

Discussion
SEH usually occurs immediately after spinal trauma or surgery 4 . However, Kummell disease with huge SEH is a unique complication, which has been rarely reported since it was rst reported in 2008 5 . It occurs more commonly in the conservative treatment of thoracolumbar osteoporotic vertebral compression fracture with or without neurological de cits 6 .
The pathogenesis and natural course of Kummell disease associated with SEH is still unclear. Several hypotheses have been used to explain it. One hypothesis 7 is that there is a connection between the intravertebral cleft and epidural space in Kummell disease, so that during weight bearing by nonunion or re-fracture with dynamic mobility, the uid including hemorrhage may be under pressure and pushed into the epidural space, resulting in SEH. Another theory 8 is that local pooling of thin-walled epidural venous plexus may be ruptured due to a brief increase in venous pressure caused by nonunion or dynamic refracture. In our case, the patient suffered from the aggravation of low back pain caused by minor trauma again and MRI suggested evidence of re-fracture, so we believe that the formation of SEH may be caused by re-fracture.
Whether the patients of Kummell disease with SEH have neurological de cits remains to be elucidated.
Kummell disease is a nonunion of fractures characterized by pseudoarthrosis and vacuum cleft 9 . We believe that whether the patient has neurological de cits may be related to the segment of Kummell disease, the size of the hematoma and the relative position of the hematoma to the conus medulla.
The treatment of Kummell disease with SEH depends on the following factors: the patient's general ability to withstand surgery, the presence of severe back pain, kyphosis, and the presence of neurological de cits. For patients of Kummell disease with huge SEH when their neurological intact, or the whole body is unable to tolerate surgery such as hematoma removal, percutaneous vertebroplasty, as a minimally invasive treatment, not only can effectively alleviate pain, restore vertebral body height, reconstruction of spinal stability 10 , but also ll the vacuum cleft with bone cement, thus blocking the connection between the vacuum cleft and the epidural space, helps to spontaneous absorption of the hematoma. For patients with neurological de cits, the prognosis is related to the degree of preoperative neurological impairment and the time to operation 11 . Therefore, timely and adequate decompression is the key to achieve great surgical results. Kim et al 12 adopted anterior thoracolumbar vertebrae resection and bone grafting, and posterior bone cement enhanced screw xation to increase spinal stability. Oda et al 5 performed vertebroplasty combined with posterior decompression, which provided satisfactory vertebral reconstruction and posterior decompression through a single posterior approach. In this case, the patient had no neurological de cits, and we performed percutaneous vertebroplasty. The patient recovered well immediately and the reexamination 1 week after operation showed that the hematoma almost completely subsided.

Conclusions
Although extremely rare, there is a possibility of SEH related to re-fracture of Kummell disease, and it could be further con rmed via MRI and pathological examination. Timely operation is recommended, and results are usually favorable. Abbreviations SEH, spinal epidural hematoma; MRI, magnetic resonance imaging; CT, computed tomography Declarations Ethics approval and consent to participate This study was approved by the ethics committee of Xi'an Honghui Hospital, and written informed consent was obtained from the patient to publish the details of his case.

Consent for publication
A written, signed informed consent to publish all data and any accompanying images was obtained from the study participant.