case report

Paradoxical Presentation of an Acute Vertebral Compression Fracture

Authors
Timothy R Niedzielak, OMS-II (1); John P Malloy, IV, DO (2)

Affiliations
Nova Southeastern University College of Osteopathic Medicine, Davie, FL  (1); East Coast Orthopedics, Pompano Beach, FL (2)

Abstract
Osteoporotic vertebral compression fractures (VCF) are a common public health concern and the guidelines for imaging and subsequent diagnosis are fairly well accepted. Radiographs are typically obtained upon initial presentation of a patient complaining of acute back pain. While they are able to detect the morphological changes associated with a VCF, radiographs are insufficient in detecting the acuity of the injury. Both MRI and bone scintigraphy can aid in determining the acuity of a VCF. MRI is highly sensitive(≥98%) to water content on STIR and T2 weighted images. The high signal intensity associated with fracture edema, acute blood products, and inflammation makes MRI highly accurate in the detection of acute fractures. Fractures which do not have high signal intensity due to the absence of bone edema are considered chronic and read as “negative for acute fracture.” Bone scans may require up to 72 hours for osteoblastic activity to become detectable in the early phase of fracture healing and therefore may be falsely interpreted as negative in the hyperacute phase (<72hrs). This creates a scenario where an acute VCF may present as positive on MRI and negative on bone scan. To our knowledge the converse presentation has not been reported in the literature. We present a case of a patient presenting with an acute VCF which was initially negative on MRI and positive on bone scan.

Introduction
Osteoporosis is one of the most common public health concerns in the United States today, which increases the prevalence of vertebral compression fractures (VCF) in the elderly population. In fact, there are nearly 1.4 million new diagnoses of osteoporotic VCF worldwide, which if misdiagnosed leads to higher rates of morbidity and mortality. (6) It is important that an osteoporotic patient presenting with sudden onset back pain of idiopathic nature or from a traumatic event have VCF included in the differential diagnoses.

Many imaging modalities are available, however plain radiographs are typically obtained during a patient’s initial visit presenting with symptoms of an acute vertebral compression fracture, especially in the emergency setting. However, radiographs often are not sufficient to determine the acuity of the injury. Radiographs can miss an occult VCF without deformity of the vertebral body, while chronic VCFs can be misinterpreted as acute. For that reason, magnetic resonance imaging (MRI) and nuclear medicine bone scintigraphy can be used to assess the acuity and healing stage of these fractures. It is widely known that a bone scan will often require greater than 72 hours to demonstrate increased uptake on imaging as this represents osteoblastic activity during the reparative phase of the fracture. (11) MRI is highly sensitive to edema and high water content, especially with the use of STIR sequences. (12) Bone edema and inflammation occurs rapidly after a fracture and persists during the reparative process over the course of months. (5) The literature suggests that MRI used to diagnose and differentiate acute compression fractures due to osteoporosis or malignancy has sensitivity of ≥98%. (1, 7) This makes MRI highly sensitive in detecting fractures and in determining the acuity or chronicity of fractures, including osteoporotic VCF. It is therefore commonly accepted that within the hyperacute phase of a fracture, a bone scan may be cold, while a MRI would be hyperintense in the area of the fracture.

We present a unique case of the converse in which MRI findings did not demonstrate increased signal intensity, yet the bone scan showed significant uptake in a patient with a strong history and physical exam consistent with an acute L3 VCF. To our knowledge this presentation has not yet been reported in the literature.

Case Report
The patient is an 83-year-old female, with no prior history of low back pain, who presented to the ER 2 weeks after sustaining a ground-level fall and complained of intractable back pain and ambulatory dysfunction. Radiographs revealed an L3 compression fracture (Fig. 1). She was admitted to the hospital with a tentative plan for kyphoplasty. MRI was obtained to determine acuity of the fracture and unexpectedly revealed the compression fracture to be chronic with no increased signal intensity on STIR or T2-weighted images (Fig. 2). She was subsequently discharged to home.

Fig 1 A-B

Figure 1A. Anteroposterior radiograph of an L3 VCF demonstrated by vertebral body loss of height.
B.
Sagittal radiograph showing an L3 VCF demonstrated by anterior vertebral wedging.

Fig. 2

Figures 2A-B. Sagittal STIR sequence (A) and T2-weighted (B) magnetic resonance images demonstrating lack of increased signal intensity at the L3 segment, indicative of a chronic VCF.

Over the next two weeks, the severe pain persisted and she presented to the office by wheelchair. Physical examination revealed the patient to be neurovascularly intact with marked paraspinal tenderness in the lumbar region. Range of motion was diminished with lumbar flexion and extension. The patient had difficulty standing upright and required family assistance in using a walker to ambulate short distances. Office radiographs again demonstrated a L3 compression fracture. The patient’s history, physical exam, radiographic and diagnostic findings appeared consistent with an acute compression fracture. However, her MRI from the emergency room suggested otherwise. Therefore, a whole body bone scintigraphy study was ordered and obtained the next day.

The bone scintigraphy demonstrated diffuse increased uptake at the level of L3 consistent with an acute fracture (Fig. 3). After discussing the treatment options with the patient and given the failure of nonoperative treatment along with the failure of pain control with medication, the patient underwent a balloon kyphoplasty (Fig. 4). Intraoperatively, a core biopsy was obtained from the vertebral body through both pedicles. The pathology report came back negative for primary neoplasm or metastasis and was consistent with osteoporosis. On post-operative day 1, the patient’s pain improved and she was discharged to home ambulating independently.

Fig. 3

Figure 3. Bone scintigraphy demonstrating diffuse radiotracer uptake at the level of L3 consistent with an acute VCF.

Fig. 4

Figure 4. Intraoperative fluoroscopy images demonstrating balloon kyphoplasty at the level of L3.

Discussion
Marcus et. al. suggested that pain may precede an impending VCF and that MRI may be the study of choice as follow-up to negative plain radiographs despite increasing suspicion of acute fracture. (9) Our case, although an isolated event, shows that MRI alone may not be successful at picking up an acute VCF, despite its high sensitivity. (1, 7) Patients that are found to have clinical findings suggestive of an acute fracture despite negative radiographic findings should undergo further physiologic studies such as technetium-99 bone scintigraphy. However, it is important to keep in mind that different anatomical sites will respond at different rates on bone scintigraphy studies after fracture. Fractures of the pelvis and radius may show a higher initial intensity of radiotracer uptake as well as a steeper increase in accumulation compared to spine fractures, with spine fractures typically reaching a peak near 15-17 days after insult. (13) In general, fractures in the acute phase under 4 weeks will show diffuse increased uptake, whereas those in subacute phase, up to three months, will show more localized uptake. It is also important to keep in mind that scintigraphic findings may remain abnormal for up to 2 years, slowly losing intensity over that period. (11) Nevertheless, it can be stated that all acute fractures regardless of site will reach peak radiotracer accumulation within 2-5 weeks after trauma as the vascular proliferation reaches its peak as well.

We propose that clinical suspicion based on physical exam by a physician should be weighed heavily despite negative findings on imaging studies. Masala et. al. suggested the necessity of a patient with a VCF under 3 weeks to undergo both pre-operative MRI-STIR imaging and 99mTc MDP scintigraphy prior to kyphoplasty. (10) Research has shown that increased uptake in bone scintigraphy studies at one vertebral segment are confidently confirmed as acute fractures on MRI. The concordance between bone scintigraphy and MRI at two or more vertebral segments as an acute fracture is however not significant and should not be trusted. (8) That is to say, when one vertebral segment is suspected for VCF, MRI and bone scintigraphy findings should be consistent. Despite these suggestions and research, to our knowledge, there have been no prior guidelines that demonstrate the clinical course to determine the candidacy of a patient for kyphoplasty after negative findings on MRI, with persistent clinical suspicion for an acute benign vertebral compression fracture.

We therefore recommend that upon initial patient presentation in a suspected acute VCF, MRI imaging be ordered and obtained. Although many MRI pulse sequences are available, T1-weighted sagittal images with fat suppression will show stronger enhancement in patients with metastatic or acute benign VCF versus patients with chronic VCF. (3-4) Furthermore, acute and subacute fractures, those less than 90 days can be diagnosed using MRI, where the VCF will have hypointense signal on T1 weighted imaging and have a hyperintense signal on T2 weighted and short T1 inverted recovery (STIR) sequences. (2, 4, 10, 12) The healing process of bone fracture, in which vascular proliferation can last up to 3-10 weeks, is consistent with increasing contrast enhancement on T1-weighted sagittal imaging after gadolinium administration with fat suppression. (3) However, if MRI findings are inconsistent with physical exam findings of acute VCF as was the case with our patient, the physician should order a bone scintigraphy study using technetium-99 for confirmation. Patients with radiographic evidence of fracture but no scintigraphic activity can be assumed to have a chronic fracture, whereas those with increased diffuse activity are suggested to have an acute fracture. (5)

Once confirmation of an acute/subacute VCF or metastatic lesion is obtained, the operating physician can plan for surgery. Intraoperatively, the surgeon should plan on retrieving a intravertebral biopsy for pathology sample to rule out metastasis. (4)

References

  1. Abdel-Wanis M, Solyman M, Hasan N. Sensitivity, specificity and accuracy of magnetic resonance imaging for differentiating vertebral compression fractures caused by malignancy, osteoporosis, and infections. Journal Of Orthopaedic Surgery (Hong Kong).
  2. Baur A, Stäbler A, Arbogast S, Duerr H, Bartl R, Reiser M. Acute osteoporotic and neoplastic vertebral compression fractures: fluid sign at MR imaging. Radiology. (2002, Dec); 225(3): 730-735.
  3. Chen W, Shih T, Chen R, Lo H, Chou C, Tu H, et al. Blood perfusion of vertebral lesions evaluated with gadolinium-enhanced dynamic MRI: in comparison with compression fracture and metastasis. Journal Of Magnetic Resonance Imaging: JMRI. (2002, Mar); 15(3): 308-314.
  4. Cicala D, Briganti F, Casale L, Rossi C, Cagini L, Giganti M, et al. Atraumatic vertebral compression fractures: differential diagnosis between benign osteoporotic and malignant fractures by MRI. Musculoskeletal Surgery. (2013, Aug); 97 Suppl 2S169-S179.
  5. Cook G, Hannaford E, See M, Clarke S, Fogelman I. The value of bone scintigraphy in the evaluation of osteoporotic patients with back pain. Scandinavian Journal Of Rheumatology. (2002); 31(4): 245-248.
  6. Johnell O, Kanis J. An estimate of the worldwide prevalence and disability associated with osteoporotic fractures. Osteoporosis International: A Journal Established As Result Of Cooperation Between The European Foundation For Osteoporosis And The National Osteoporosis Foundation Of The USA. (2006, Dec); 17(12): 1726-1733.
  7. Jung H, Jee W, McCauley T, Ha K, Choi K. Discrimination of metastatic from acute osteoporotic compression spinal fractures with MR imaging. Radiographics: A Review Publication Of The Radiological Society Of North America, Inc. (2003, Jan); 23(1): 179-187.
  8. Kim J, Kim J, Jang B, Seo J, Kim J. The comparison of bone scan and MRI in osteoporotic compression fractures. Asian Spine Journal. (2010, Dec); 4(2): 89-95.
  9. Marcus D, Lee P, Fish D. Pain precedes computer axial tomography and scintigraphic findings in an osteoporotic vertebral compression fracture: a case report. Pain Medicine (Malden, Mass.). (2008, Oct); 9(7): 866-870.
  10. Masala S, Schillaci O, Massari F, Danieli R, Ursone A, Simonetti G, et al. MRI and bone scan imaging in the preoperative evaluation of painful vertebral fractures treated with vertebroplasty and kyphoplasty. In Vivo (Athens, Greece). (2005, Nov); 19(6): 1055-1060.
  11. Matin P. The appearance of bone scans following fractures, including immediate and long-term studies. Journal Of Nuclear Medicine: Official Publication, Society Of Nuclear Medicine. (1979, Dec); 20(12): 1227-1231.
  12. Ogura A, Hayakawa K, Maeda F, Saeki F, Syukutani A, Kuroda E, et al. Differential diagnosis of vertebral compression fracture using in-phase/opposed-phase and short TI inversion recovery imaging. Acta Radiologica (Stockholm, Sweden: 1987). (2012, May 1); 53(4): 450-455.
  13. Spitz J, Lauer I, Tittel K, Wiegand H. Scintimetric evaluation of remodeling after bone fractures in man. Journal Of Nuclear Medicine: Official Publication, Society Of Nuclear Medicine. (1993, Sep); 34(9): 1403-1409.

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