Aneurysmal Bone Cyst in a 21-Year-Old Woman Presenting with Chronic Low Back Pain in a Chiropractic Office: A Case Report

Introduction

L ow back pain (LBP) in children, adolescents, and young adults is often caused by a serious underlying pathologic condition. The investigation should begin with a careful patient history, complete physical examination, laboratory testing, and imaging studies. ¹ Because pain is a very nonspecific symptom, the physician should be aware that pain associated with tumor tends to be progressive and severe and is not closely related to activity. ²

The term aneurysmal bone cyst (ABC) was introduced in 1942 by Jaffe and Lichtenstein. ^{3 –11} They described the lesion as a blood-filled cavity, equivalent to a cyst, that has a blowout radiographic appearance, analogous to a saccular aneurysm. ^4,5 Although the terminology has been accepted, an ABC is neither an aneurysm nor a cyst. The current theory characterizes the ABC as a nonneoplastic reactive condition that aggressively expands the bone and affects the adjacent structures. ^5,6 Generally, ABCs involve long bones, although about 20% occur at the vertebral column. ¹² The cause and pathogenesis of this rare, benign, vascular, and multicystic lesion remain unclear. ^5,8

We report a case of ABC occurring at the lumbar spine. A 21-year-old female student presented to the chiropractic office with chronic low back pain (LBP). This case was managed by a multidisciplinary team composed by a doctor of chiropractic, an orthopedic specialist, and a spine surgeon. The treatment of choice was en bloc surgery followed by bone grafting reconstruction; afterward, LBP was relieved and the lesion did not recur.

Case Report

A 21-year-old female student presented to the chiropractic office with a 2-year history of progressive LBP and intermittent pain in both hips. The patient reported having experienced LBP since she was 12 years old, but the pain in the last 2 years was more severe and was now continuous. The patient described the LBP as an aching type of pain that was more pronounced during activity and exercises. In addition, she reported weight loss and increased fatigue. The patient's medical history was remarkable only for an abdominal hernia repair at 10 years of age.

Physical examination showed that the vital signs were within normal limits. Regional physical assessment of the head, neck, chest, lung, and abdomen was also performed. Physical examination showed tenderness to palpation of paravertebral muscles on the left side from approximately L1 to L5, with slightly greater severity on the left side of L3. Orthopedic examination revealed normal range of motion of the cervical and the dorsolumbar spine during flexion, extension, lateral flexion, and rotation. However, the patient reported LBP while performing all the dorsolumbar movements. Additional findings demonstrated positive results for the bilateral straight-leg-raise sign, Lasègue's sign, and Bechterew test and negative findings on the Valsalva maneuver. Neurologic examination revealed no paresthesias, numbness, or loss of muscle strength. Therefore, the sensory and motor examination was normal, cranial nerves were intact, and deep-tendon reflexes were preserved and symmetric (+2). The Babinski sign was absent. A radiograph of the lumbar spine showed a well-defined lesion, characterized as expansile and lytic, with markedly thinned cortex involving the left inferior half and posterior portion of the vertebral body of L3, with the appearance of an ABC. However, two previous radiographs of the lumbar spine taken when the patient was 14 and 19 years of age were reviewed, and no indication of the present lesion was found.

Therefore, an orthopedist confirmed the patient's status and referred her to a spine surgeon. On the basis of preview imaging studies, the spine surgeon requested further evaluation with whole-body bone scintigraphy, with 99mTc-methylene diphosphonate as the contrast agent, and computed tomography (CT). Scintigraphy revealed a focal increase in radiotracer uptake at the lateral aspect of L3. The CT scan showed a sharply marginated and expansile lesion involving the left side of the vertebral body of L3. The spinal canal was not compromised, and the lesion only minimally extended into the left third pedicle. The left lateral recess width of L3 was preserved. The remaining vertebral bodies, posterior elements, and spinal canal appeared normal. Further views of the head, axial skeleton, and femurs showed no abnormalities that would be consistent with metastatic disease.

At this point, on the basis of the patient's history, clinical presentation, physical examination, and imaging findings, the clinicians confirmed the focal lesion, at the left inferior half and posterolateral aspect of the vertebral body of L3, to be most consistent with ABC. Thus, treatment involved L3 hemivertebrectomy resection en bloc and a vertebral fusion from L2 to L4 with a tricortical iliac crest graft. During hospitalization, the patient did physical therapy, remained afebrile, and recovered without complications. CT performed 2 weeks after surgery showed the resection of the left half of the vertebral body of L3 and the superior and inferior graft ends placed in the lateral aspect of L2 and L4, respectively. After surgery and recovery, LBP was relieved and the bone lesion did not recur.

Discussion

We describe a case of ABC in a 21-year-old female patient with a 2-year history of progressive LBP and local symptoms. The symptoms consisted of tenderness, pain, and restricted dorsolumbar range of motion due to an extensive bone lesion at the level of L3. ABCs predominantly affect children and young adults. The peak incidence is during the second decade of life. There is a slight preponderance for females over males. ^5,6,13 Patients may present with an insidious onset of back pain, with an average duration of 2 years. ^9,13 The clinical presentation varies; however, the most common symptoms are pain, swelling, tenderness, and restriction of movement in affected areas. These symptoms depend on the location and size of the tumor. ^6,14 In addition, vertebral lesions often are accompanied by pathologic fracture, invasion of paravertebral soft tissues, and spinal cord compression, resulting in such symptoms as sensory disturbances, motor weakness, and bowel and bladder dysfunction. ^7,15,16

A classic ABC is an expansile, benign, osteolytic lesion that poses an aggressive vascular disorder in the bones; it is eccentrically blown-out, like a saccular aneurysm, with the strands of bone forming a “soap bubble” appearance on radiographs. The multiple blood-filled cavities undergo pressure, with marked ballooning of a thinned cortex, and exhibit hypervascularity. ^5,6,16,17 The cause of ABC is unclear. In about 70% of the cases ABC may present as a primary bone lesion; the remaining 30% of cases present as a secondary lesion when a preexisting osseous condition can be identified, ⁸ such as giant cell tumors, hemangiomas, osteosarcoma, osteoblastoma, chondroid myxoma, chondroblastoma, or fibrous dysplasia. ^8,12,14 Theories about pathogenesis include hemodynamic disturbances, post-traumatic cause, reactive vascular malformations, or genetically predisposed bone tumors. The most widely accepted mechanism involves a local hemodynamic disturbance, such as arteriovenous shunts or malformations, leading to markedly increased venous pressure and subsequent bony resorption and destruction of the vascular bed. ^{8,12,14 –16}

ABCs make up approximately 10% of all primary spine tumors; however, it is difficult to establish the accurate incidence because some lesions remain occult or may regress spontaneously. ⁹ Of all ABCs located at the vertebral column, approximately 60% are situated in the posterior elements of the vertebra, such as pedicles, laminae, and spinous process; however, the lesions may extend to the vertebral body. ^5,6,9,15 In this particular case, a very definite lesion was found involving the left inferior half and posterior portion of the vertebral body of L3, only minimally extended into the left pedicle.

Regarding the diagnosis of ABCs, imaging studies are crucial. ¹⁴ The diagnostic evaluation of ABCs begins with plain radiography. However, the complex anatomy of the spine requires cross-sectional imaging with CT (which is especially valuable to define the lesions), along with bone scintigraphy (which accurately reflects the extent of osseous involvement) or contrast-enhanced magnetic resonance imaging. ^9,10 In this report, the diagnosis was based on radiography, bone scintigraphy, and CT findings. According to Salunke and colleagues, ¹⁷ the preoperative diagnosis of an ABC is typically made on radiography.

The treatment of an ABC in the spine depends on regional location of the lesion, anatomic location of the tumor, evidence of spinal cord compression, structural integrity of the spinal segment, growth pattern, patient age, vascularity, size, and extension of the lesion. ^8,9,14,16 Various methods of therapy for spinal ABCs have been described, including intralesional curettage with or without bone grafting, en bloc resection, selective arterial embolization, cryotherapy, radiation therapy, and a wait-and-see strategy. ^8,11 Our patient was treated with surgical resection en bloc, consistent with hemivertebrectomy of L3, and a vertebral fusion from L2 to L4 with bone grafting, without history of lesion reoccurrence. According to Berven and Burch, ⁹ the only recurrence-free surgical option is the en bloc resection. Reinforced by Gasbarrini and colleagues, ¹⁵ the treatment of choice in the management of benign tumors of the spine is en bloc excision.

Conclusion

Numerous conditions can cause LBP, and a vast group of practitioners, such as chiropractors, physiotherapists, physicians, neurosurgeons, and orthopedic specialists, can diagnose the condition and either provide care or refer the patient. Relatively uncommon, ABC is an important condition that can affect the spine. For that reason, we emphasize the importance of recognition, appropriate investigation, early detection, accurate diagnosis, and multidisciplinary management of the patient. We reported this case because, as conservative and complementary providers, we must be aware that the cause of LBP may extend beyond musculoskeletal dysfunction. We conclude that it is important to identify and diagnose the ABC and to refer these patients for appropriate treatment.