- Email: [email protected]
Multiple vertebral osteonecrosis
Available online at www.sciencedirect.com
Joint Bone Spine 75 (2008) 341e344 http://france.elsevier.com/direct/BONSOI/
Case report
Multiple vertebral osteonecrosis Rose-Marie Javier a,*, Thomas Moser b, Jean-Louis Dietemann b, Laetitia Sparsa a, Shanti Natarajan-Ame c, Marie-Pierrette Chenard d, Jean-Louis Kuntz a a
Department of Rheumatology, Hoˆpital de Hautepierre, 67000 Strasbourg, France b Department of Radiology, Hoˆpital de Hautepierre, 67000 Strasbourg, France c Department of Hematology and Oncology, Hoˆpital de Hautepierre, 67000 Strasbourg, France d Department of Pathology, Hoˆpital de Hautepierre, 67000 Strasbourg, France Accepted 16 May 2007 Available online 31 August 2007
Abstract Vertebral osteonecrosis classically presents with an intravertebral vacuum cleft phenomenon or a fluid-filled cleft on MR images. These clefts are usually found in older patients presenting with more severe fractures, more significant collapse and instability. Therefore, although considered for a long time as pathognomonic for vertebral osteonecrosis, vertebral clefts are now considered to represent fracture non-union. The double-line sign is classically described for osteonecrosis of long bones, but has been reported in one case of concurrent spinal cord and vertebral bone marrow radionecrosis. We present a case of a histologically confirmed multilevel vertebral osteonecrosis manifesting as a double-line sign in the absence of an associated vertebral collapse and unrelated to radiotherapy. Ó 2007 Elsevier Masson SAS. All rights reserved. Keywords: Vertebral osteonecrosis; Intravertebral vacuum cleft phenomenon; Double; Line sign; Fracture non-union
1. Introduction Vertebral osteonecrosis classically presents with an intravertebral vacuum cleft phenomenon. The intravertebral vacuum cleft on plain radiography was first described by Maldague et al. [1] in 1978, in 10 patients mostly on chronic corticosteroid therapy, as ‘‘a gas-density cleft within a transverse separation of the vertebral body, appearing in extension and disappearing in flexion’’, and ‘‘thought to represent ischemic vertebral collapse’’. While the pathogenesis of this process is not completely understood, the authors suggested that it resulted from the release of gas within distracted cracks in the sub-chondral bone. Bone ischemia was histologically confirmed in one patient. They suggested that the intravertebral cleft sign represented a reliable sign of vertebral osteonecrosis. Resnick et al. [2] compared this image to the ‘‘crescent’’ sign which accompanies osteonecrosis of the femoral or humeral heads. The presence of gas within the vertebral body * Corresponding author. Tel.: þ33 03 8812 7953; fax: þ33 03 8812 7951. E-mail address: [email protected] (R.-M. Javier).
has rarely been reported in vertebral malignancy and several authors consider this radiological aspect pathognomonic of vertebral osteonecrosis avoiding further investigation [3]. More recently, the presence of a fluid collection at magnetic resonance imaging (MRI) has been described in rare cases of avascular necrosis [4] and identification of this fluid sign with MRI in a vertebral collapse favors an osteoporotic rather than metastatic etiology [5]. To our knowledge, the double-line sign, inconstant but highly specific for epiphyseal or metaphyseal osteonecrosis [6], has never been reported in vertebral osteonecrosis associated with osteoporosis. We present a histologically confirmed-case of multiple vertebral osteonecrosis demonstrating a prominent double-line sign, and discuss current concepts about this uncommon disease. 2. Case report A 73-year-old woman presented in August of 2005 with spontaneous thoracolumbar back pain, incompletely relieved
1297-319X/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.jbspin.2007.05.010
342
R.-M. Javier et al. / Joint Bone Spine 75 (2008) 341e344
by analgesics. Her past medical history was significant for osteoporosis treated by raloxifene, and a stage IV Burkitt-like nonHodgkin lymphoma (with bone marrow involvement) diagnosed in July 2003 and treated by chemotherapy (CHOP regimen comprising Cyclophosphamide, Adriamycine, Vincristine and Prednisone in association with rituximab) until December 2003 with a complete remission confirmed on bone marrow biopsy. Physical examination revealed diffused tenderness predominantly at the L5 and S1 vertebral levels, without fever or alteration of her general status. Blood counts and biochemistry were unremarkable with no evidence of an inflammatory syndrome. Radiographs of the spine demonstrated diffused osteopenia, with mild compression fractures of T7, T12, L1 and L2 (Figs. S1a, b; see the supplementary material associated with this article online). These fractures were confirmed on CT scanning which also excluded underlying osteolytic lesions (Fig. 1). Bone scanning with 99Tc-MNDP showed no increase in tracer uptake along the spine or anywhere else. Positron emission tomography (PET) failed to reveal any focus of increased metabolism. A spinal MRI was performed on a 1.5 T Magneton scanner (Siemens Medical Systems) including the following sequences (sagittal T1W (TR/TE, 406/12), sagittal T2W (TR/TE, 3500/120), sagittal STIR (TR/TE/TI, 2500/70/160), and sagittal fat suppressed T1W (TR/TE, 423/7,5) after intravenous administration of 0.01 mmol/kg DOTA-gadolinium (Laboratoires Guerbet) (Figs. S1c and 2). Previously described wedge fractures (T7, T12, L1 and L2) were associated with diffuse signal anomalies of the bone marrow at thoracic, lumbar and sacral
Fig. 2. Sagittal T2 weighted (a, b) (TR/TE, 3500/120), sagittal STIR (c) (TR/ TE/TI, 2500/70/160). This images demonstrate multifocal bone marrow anomalies (hypointense T1 and hyperintense T2) in most thoracic and lumbar vertebral bodies as well as sacrum. In numerous vertebral bodies, a double-lign sign is clearly demonstrated suggesting as in long bones the diagnosis of osteonecrosis.
levels. Signal anomalies presented as well limited geographic areas appearing mostly hypointense on T1WI and hyperintense on T2WI together with faint contrast enhancement in the vicinity of endplate fractures. Signal anomalies were predominant in the central aspect of vertebral bodies and under vertebral endplates. A double-line sign was conspicuous at most vertebral levels from T4 to L5 and also in the sacrum, suggesting the diagnosis of multiple vertebral osteonecrosis in the absence of vertebral collapse (Figs. S1c and 2). Biopsies of 2 vertebrae (L1 collapsed and L5 with no vertebral collapse) presenting the double-line sign was performed under CT guidance to clearly exclude lymphomatous involvement of the spinal bone marrow. At pathological examination, specimens demonstrated necrosis of hematopoietic and fatty cells of the bone marrow as well as reactive lymphocytes, but no evidence of lymphoma or any other neoplastic process (Fig. S2). In the absence of other osteoarticular symptoms, no other investigations were done. Complete pain relief was obtained with analgesics and persists at 18 months of follow up. All images remain unchanged on spinal MRI. 3. Discussion
Fig. 1. Sagittal image of spinal CT confirms compression fractures of L1, L2 with central non-union at L2 level.
Vertebral osteonecrosis is usually suspected in the presence of an intravertebral vacuum cleft sign [3]. The cleft sign corresponds to fluid or gas trapped within a fractured vertebral body and was initially described and histologically confirmed by Maldague [1] in patients on steroids. Since then, several cases of vertebral osteonecrosis have been described occurring mainly in middle aged and elderly women [7]. They are usually
R.-M. Javier et al. / Joint Bone Spine 75 (2008) 341e344
unique and involve essentially the lower thoracic and upper lumbar spine [8]. Like peripheral osteonecrosis, they are related to steroid therapy, diabetes, radiation therapy, and alcohol intoxication [7]. Neurological complications are more frequently associated with vertebral collapse due to osteonecrosis than to osteoporotic fractures [7,9]. Osteonecrosis of the vertebral body is recognized as a relatively uncommon disease [10] but the intravertebral vacuum cleft sign is sometimes only observed on conventional hyperextension radiographs. Performance of hyperextension radiographs in patients with osteoporotic fractures can reveal a large number cases of vertebral necrosis, 10% [8] to 37% of osteoporotic vertebral fractures presenting with an air-filled vacuum cleft sign [11]. MR images also allow detection of clefts filled with fluid [12]. The clefts are usually found in older patients with more severe fractures, significant collapse and angulation [13] and generally corresponds to unstable fractures [11,14]. This explains why vertebral clefts which were considered for a long time as pathognomonic for vertebral osteonecrosis [3] are now thought to represent fracture non-union [8,13]. In our observation, the cleft sign was absent whereas vertebral necrosis was histologically proven in two sites including a non-fractured vertebra. Involvement of 13 vertebrae was rather similar to other observations of vertebral body infarcts associated with spinal cord ischemia [15e17] or radionecrosis [18]. Signal abnormalities of vertebral bodies such as bone marrow oedema have been observed during the early phase signal of spinal cord ischemia. Depending on the radiculomedullary artery involved [19], these anomalies involve either the anterior or posterior parts of the vertebral body. In their study, Yuh et al. [15] observed bone marrow anomalies in 3 of 12 cases of spinal cord infarction. For many authors, these vertebral anomalies are strongly suggestive of spinal cord infarction [15,16]. In our patient, in addition to the diffuse anomalies of multiple vertebral bodies (a total of 13 vertebral bodies), we observed a double-line sign at most vertebral levels and in the sacrum. The double-line sign is seen with osteonecrosis (AVN) on T2weighted MRI images of medullary bones as a high-signalintensity line within a parallel rim of decreased signal intensity often with serpentine borders [6]. The high-signal-intensity inner zone is thought to represent hyperemic granulation tissue whereas the low-signal-intensity outer zone represents reactive sclerotic bone [6]. Chemical shift misregistration may also accentuate the low signal intensity of the outer rim in some cases [6]. AVN may be initiated by a traumatic disruption of a vessel or by other factors that cause ischemia, such as thromboembolism or venous stasis. After an initial traumatic insult, hematopoietic cells die within 6e12 h; marrow fat/adipose cells die in 2e5 days. Ischemic bone eventually undergoes repair from its periphery to its infarcted center. Healing begins with hyperemia at the ischemic periphery; this is subsequently replaced by reactive tissue and sclerosis. Microfractures and bony collapse may occur as trabeculae are reabsorbed. It is the reparative process that is best depicted on MRI images and on conventional radiographs. This sign usually described in osteonecrosis of the long tubular bones [20] occurs later in the disease process, after the onset of bone repair [6].
343
To our knowledge, this typical double-line sign has been reported in only one case of concurrent spinal cord and vertebral bone marrow radionecrosis 8 years after radiotherapy for a nonHodgkin’s lymphoma [18]. In this case, the initial MRI taken at the time of paraparesis revealed a diffuse fatty appearance of the vertebral bone marrow. The last MRI 8 months later showed the typical double-line sign within the T9eT11 vertebral bodies without vertebral collapse confirming the delayed appearance of this sign. In the early stages of bone marrow necrosis (BMN), a rare clinicopathologic entity occurring before the diagnosis of malignancy, after chemotherapy or at tumour recurrence, MRI appearances can be indistinguishable from avascular necrosis but trephine biopsy confirms necrosis of the myeloid tissue [21,22]. Bone marrow necrosis usually presents with bone pain (80% of cases), fever (70%), and fatigue. The prognosis is generally considered poor, death occurring within weeks or months [21,22]. In our case, a normal PET and radionuclear bone scan and the presence of the spinal double-line sign at several levels was useful in differentiating multiple vertebral osteonecrosis from other malignant conditions, and in particular with lymphomatous bone marrow involvement. Biopsy didn’t revealed malignancy or bone marrow necrosis but only aseptic osteonecrosis. In combination with multiple vertebral involvements, this sign suggested a systemic cause. The pathogenesis of multiple osteonecrosis is not well understood. Because of the normal radionuclear bone scan at the time of diagnosis and a favourable evolution 18 months later, we believe that osteonecrosis occurred during chemotherapy favoured by steroids (total dose of prednisone: 3774 mg from July 2003 to December 2003). Osteoporosis preceding the diagnosis of lymphoma must be emphasised, but we cannot exclude the role of the underlying hematologic malignancy as suspected in some cases of bone marrow necrosis [21]. As MRI is increasingly used in the evaluation and follow-up of bone marrow diseases, these MRI features will be encountered more often and perhaps become better understood. 4. Conclusion In conclusion, our observation of vertebral osteonecrosis offers several interesting aspects. Multifocal involvement without vertebral collapse, presence of a double-line sign and absence of a cleft sign on MRI is strongly in favour of a systemic origin for the osteonecrosis. This has rarely been described in the spine. Our unusual presentation of histologically proven osteonecrosis is also consistent with recent data [8,13] suggesting that the vertebral cleft, considered as pathognomonic of vertebral osteonecrosis, results from vertebral non-union rather than vertebral osteonecrosis.
Supplementary material Supplementary material (Figs. S1aec and S2) associated with this article can be found at http://www.sciencedirect.com, at doi:10.1016/j.jbspin.2007.05.010.
344
R.-M. Javier et al. / Joint Bone Spine 75 (2008) 341e344
References [1] Maldague BE, Noel HM, Malghem JJ. The intravertebral vacuum cleft: a sign of ischemic vertebral collapse. Radiology 1978;129:23e9. [2] Resnick D, Niwayama G, Guerra J, et al. Spinal vacuum phenomena: anatomical study and review. Radiology 1981;139:341e8. [3] Theodorou DJ. The intravertebral vacuum cleft sign. Radiology 2001;221:787e8. [4] Dupuy DE, Palmer WE, Rosenthal DI. Vertebral fluid collection associated with vertebral collapse. AJR Am J Roentgenol 1996;167: 1535e8. [5] Baur A, Sta¨bler A, Arbogast S, et al. Acute osteoporotic and neoplastic vertebral compression fractures: fluid sign at MR imaging. Radiology 2002;225:730e5. [6] Zurlo JV. The double-line sign. Radiology 1999;212:541e2. [7] Queinnec JY, de Bray JM, Audran M, et al. Vertebral osteonecrosis. Concerning 3 cases, 1 complicated by spinal cord compression and 2 associated with another necrotic localization. Rev Rhum Mal Osteoartic 1985;52:1e5 (French). [8] Kim DY, Lee SH, Jang JS, et al. Intravertebral vacuum phenomenon in osteoporotic compression fracture: report of 67 cases with quantitative evaluation of intravertebral instability. J Neurosurg (Spine1) 2004;100: 24e31. [9] Chevalier X, Wrona N, Avouac B, et al. Thigh pain and multiple vertebral osteonecrosis: value of magnetic resonance imaging. J Rheumatol 1991;18:1627e30. [10] Chou LH, Knight RQ. Idiopathic avascular necrosis of a vertebral body. Case report and literature review. Spine 1997;22:1928e32. [11] Mc Kiernan F, Faciszewski T. Intervertebral clefts in osteoporotic vertebral compression fractures. Arthritis Rheum 2003;48:1414e9.
[12] Lane JI, Maus TP, Wald JT, et al. Intravertebral clefts opacified during vertebroplasty: pathogenesis, technical implications, and prognostic significance. Am J Neuroradiol 2002;23:1642e6. [13] Mirovsky Y, Anekstein Y, Shalmon E, et al. Vacuum clefts of the vertebral bodies. Am J Neuroradiol 2005;26:1634e40. [14] Jang JS, Kim DY, Lee SH. Efficacy of percutaneous vertebroplasty in the treatment of intravertebral pseudarthrosis associated with noninfected avascular necrosis of the vertebral body. Spine 2003;28:1588e892. [15] Yuh WT, Marsh EE, Wang AK, et al. MR imaging of spinal cord and vertebral body infarction. Am J Neuroradiol 1992;13:145e54. [16] Faig J, Busse O, Salbeck R. Vertebral body infarction as a confirmatory sign of spinal cord ischemic stroke: report of three cases and review of the literature. Stroke 1998;29:239e43. [17] Suzuki T, Kawaguchi S, Takebayashi T, et al. Vertebral body ischemia in the posterior spinal artery syndrome: case report and review of the literature. Spine 2003;28:E260e4. [18] Warscotte L, Duprez T, Lonneux M, et al. Concurrent spinal cord and vertebral bone marrow radionecrosis 8 years after therapeutic irradiation. Neuroradiology 2002;44:245e8. [19] Sliwa JA, Maclean IC. Ischemic myelopathy: a review of spinal vasculature and related clinical syndromes. Arch Phys Med Rehabil 1992;73: 365e72. [20] Vande Berg BE, Malghem JJ, Labaisse MA, et al. MR imaging of avascular necrosis and transient marrow edema of the femoral head. Radiographics 1993;13:501e20. [21] Tang YM, Jeavons S, Stuckey S, et al. MRI features of bone marrow necrosis. AJR Am J Roentgenol 2007;188:509e14. [22] Paydas S, Ergin M, Baslamisli F, et al. Bone marrow necrosis: clinicopathologic analysis of 20 cases and review of the literature. Am J Hematol 2002;70:300e5.
Joint Bone Spine 75 (2008) 341e344 http://france.elsevier.com/direct/BONSOI/
Case report
Multiple vertebral osteonecrosis Rose-Marie Javier a,*, Thomas Moser b, Jean-Louis Dietemann b, Laetitia Sparsa a, Shanti Natarajan-Ame c, Marie-Pierrette Chenard d, Jean-Louis Kuntz a a
Department of Rheumatology, Hoˆpital de Hautepierre, 67000 Strasbourg, France b Department of Radiology, Hoˆpital de Hautepierre, 67000 Strasbourg, France c Department of Hematology and Oncology, Hoˆpital de Hautepierre, 67000 Strasbourg, France d Department of Pathology, Hoˆpital de Hautepierre, 67000 Strasbourg, France Accepted 16 May 2007 Available online 31 August 2007
Abstract Vertebral osteonecrosis classically presents with an intravertebral vacuum cleft phenomenon or a fluid-filled cleft on MR images. These clefts are usually found in older patients presenting with more severe fractures, more significant collapse and instability. Therefore, although considered for a long time as pathognomonic for vertebral osteonecrosis, vertebral clefts are now considered to represent fracture non-union. The double-line sign is classically described for osteonecrosis of long bones, but has been reported in one case of concurrent spinal cord and vertebral bone marrow radionecrosis. We present a case of a histologically confirmed multilevel vertebral osteonecrosis manifesting as a double-line sign in the absence of an associated vertebral collapse and unrelated to radiotherapy. Ó 2007 Elsevier Masson SAS. All rights reserved. Keywords: Vertebral osteonecrosis; Intravertebral vacuum cleft phenomenon; Double; Line sign; Fracture non-union
1. Introduction Vertebral osteonecrosis classically presents with an intravertebral vacuum cleft phenomenon. The intravertebral vacuum cleft on plain radiography was first described by Maldague et al. [1] in 1978, in 10 patients mostly on chronic corticosteroid therapy, as ‘‘a gas-density cleft within a transverse separation of the vertebral body, appearing in extension and disappearing in flexion’’, and ‘‘thought to represent ischemic vertebral collapse’’. While the pathogenesis of this process is not completely understood, the authors suggested that it resulted from the release of gas within distracted cracks in the sub-chondral bone. Bone ischemia was histologically confirmed in one patient. They suggested that the intravertebral cleft sign represented a reliable sign of vertebral osteonecrosis. Resnick et al. [2] compared this image to the ‘‘crescent’’ sign which accompanies osteonecrosis of the femoral or humeral heads. The presence of gas within the vertebral body * Corresponding author. Tel.: þ33 03 8812 7953; fax: þ33 03 8812 7951. E-mail address: [email protected] (R.-M. Javier).
has rarely been reported in vertebral malignancy and several authors consider this radiological aspect pathognomonic of vertebral osteonecrosis avoiding further investigation [3]. More recently, the presence of a fluid collection at magnetic resonance imaging (MRI) has been described in rare cases of avascular necrosis [4] and identification of this fluid sign with MRI in a vertebral collapse favors an osteoporotic rather than metastatic etiology [5]. To our knowledge, the double-line sign, inconstant but highly specific for epiphyseal or metaphyseal osteonecrosis [6], has never been reported in vertebral osteonecrosis associated with osteoporosis. We present a histologically confirmed-case of multiple vertebral osteonecrosis demonstrating a prominent double-line sign, and discuss current concepts about this uncommon disease. 2. Case report A 73-year-old woman presented in August of 2005 with spontaneous thoracolumbar back pain, incompletely relieved
1297-319X/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.jbspin.2007.05.010
342
R.-M. Javier et al. / Joint Bone Spine 75 (2008) 341e344
by analgesics. Her past medical history was significant for osteoporosis treated by raloxifene, and a stage IV Burkitt-like nonHodgkin lymphoma (with bone marrow involvement) diagnosed in July 2003 and treated by chemotherapy (CHOP regimen comprising Cyclophosphamide, Adriamycine, Vincristine and Prednisone in association with rituximab) until December 2003 with a complete remission confirmed on bone marrow biopsy. Physical examination revealed diffused tenderness predominantly at the L5 and S1 vertebral levels, without fever or alteration of her general status. Blood counts and biochemistry were unremarkable with no evidence of an inflammatory syndrome. Radiographs of the spine demonstrated diffused osteopenia, with mild compression fractures of T7, T12, L1 and L2 (Figs. S1a, b; see the supplementary material associated with this article online). These fractures were confirmed on CT scanning which also excluded underlying osteolytic lesions (Fig. 1). Bone scanning with 99Tc-MNDP showed no increase in tracer uptake along the spine or anywhere else. Positron emission tomography (PET) failed to reveal any focus of increased metabolism. A spinal MRI was performed on a 1.5 T Magneton scanner (Siemens Medical Systems) including the following sequences (sagittal T1W (TR/TE, 406/12), sagittal T2W (TR/TE, 3500/120), sagittal STIR (TR/TE/TI, 2500/70/160), and sagittal fat suppressed T1W (TR/TE, 423/7,5) after intravenous administration of 0.01 mmol/kg DOTA-gadolinium (Laboratoires Guerbet) (Figs. S1c and 2). Previously described wedge fractures (T7, T12, L1 and L2) were associated with diffuse signal anomalies of the bone marrow at thoracic, lumbar and sacral
Fig. 2. Sagittal T2 weighted (a, b) (TR/TE, 3500/120), sagittal STIR (c) (TR/ TE/TI, 2500/70/160). This images demonstrate multifocal bone marrow anomalies (hypointense T1 and hyperintense T2) in most thoracic and lumbar vertebral bodies as well as sacrum. In numerous vertebral bodies, a double-lign sign is clearly demonstrated suggesting as in long bones the diagnosis of osteonecrosis.
levels. Signal anomalies presented as well limited geographic areas appearing mostly hypointense on T1WI and hyperintense on T2WI together with faint contrast enhancement in the vicinity of endplate fractures. Signal anomalies were predominant in the central aspect of vertebral bodies and under vertebral endplates. A double-line sign was conspicuous at most vertebral levels from T4 to L5 and also in the sacrum, suggesting the diagnosis of multiple vertebral osteonecrosis in the absence of vertebral collapse (Figs. S1c and 2). Biopsies of 2 vertebrae (L1 collapsed and L5 with no vertebral collapse) presenting the double-line sign was performed under CT guidance to clearly exclude lymphomatous involvement of the spinal bone marrow. At pathological examination, specimens demonstrated necrosis of hematopoietic and fatty cells of the bone marrow as well as reactive lymphocytes, but no evidence of lymphoma or any other neoplastic process (Fig. S2). In the absence of other osteoarticular symptoms, no other investigations were done. Complete pain relief was obtained with analgesics and persists at 18 months of follow up. All images remain unchanged on spinal MRI. 3. Discussion
Fig. 1. Sagittal image of spinal CT confirms compression fractures of L1, L2 with central non-union at L2 level.
Vertebral osteonecrosis is usually suspected in the presence of an intravertebral vacuum cleft sign [3]. The cleft sign corresponds to fluid or gas trapped within a fractured vertebral body and was initially described and histologically confirmed by Maldague [1] in patients on steroids. Since then, several cases of vertebral osteonecrosis have been described occurring mainly in middle aged and elderly women [7]. They are usually
R.-M. Javier et al. / Joint Bone Spine 75 (2008) 341e344
unique and involve essentially the lower thoracic and upper lumbar spine [8]. Like peripheral osteonecrosis, they are related to steroid therapy, diabetes, radiation therapy, and alcohol intoxication [7]. Neurological complications are more frequently associated with vertebral collapse due to osteonecrosis than to osteoporotic fractures [7,9]. Osteonecrosis of the vertebral body is recognized as a relatively uncommon disease [10] but the intravertebral vacuum cleft sign is sometimes only observed on conventional hyperextension radiographs. Performance of hyperextension radiographs in patients with osteoporotic fractures can reveal a large number cases of vertebral necrosis, 10% [8] to 37% of osteoporotic vertebral fractures presenting with an air-filled vacuum cleft sign [11]. MR images also allow detection of clefts filled with fluid [12]. The clefts are usually found in older patients with more severe fractures, significant collapse and angulation [13] and generally corresponds to unstable fractures [11,14]. This explains why vertebral clefts which were considered for a long time as pathognomonic for vertebral osteonecrosis [3] are now thought to represent fracture non-union [8,13]. In our observation, the cleft sign was absent whereas vertebral necrosis was histologically proven in two sites including a non-fractured vertebra. Involvement of 13 vertebrae was rather similar to other observations of vertebral body infarcts associated with spinal cord ischemia [15e17] or radionecrosis [18]. Signal abnormalities of vertebral bodies such as bone marrow oedema have been observed during the early phase signal of spinal cord ischemia. Depending on the radiculomedullary artery involved [19], these anomalies involve either the anterior or posterior parts of the vertebral body. In their study, Yuh et al. [15] observed bone marrow anomalies in 3 of 12 cases of spinal cord infarction. For many authors, these vertebral anomalies are strongly suggestive of spinal cord infarction [15,16]. In our patient, in addition to the diffuse anomalies of multiple vertebral bodies (a total of 13 vertebral bodies), we observed a double-line sign at most vertebral levels and in the sacrum. The double-line sign is seen with osteonecrosis (AVN) on T2weighted MRI images of medullary bones as a high-signalintensity line within a parallel rim of decreased signal intensity often with serpentine borders [6]. The high-signal-intensity inner zone is thought to represent hyperemic granulation tissue whereas the low-signal-intensity outer zone represents reactive sclerotic bone [6]. Chemical shift misregistration may also accentuate the low signal intensity of the outer rim in some cases [6]. AVN may be initiated by a traumatic disruption of a vessel or by other factors that cause ischemia, such as thromboembolism or venous stasis. After an initial traumatic insult, hematopoietic cells die within 6e12 h; marrow fat/adipose cells die in 2e5 days. Ischemic bone eventually undergoes repair from its periphery to its infarcted center. Healing begins with hyperemia at the ischemic periphery; this is subsequently replaced by reactive tissue and sclerosis. Microfractures and bony collapse may occur as trabeculae are reabsorbed. It is the reparative process that is best depicted on MRI images and on conventional radiographs. This sign usually described in osteonecrosis of the long tubular bones [20] occurs later in the disease process, after the onset of bone repair [6].
343
To our knowledge, this typical double-line sign has been reported in only one case of concurrent spinal cord and vertebral bone marrow radionecrosis 8 years after radiotherapy for a nonHodgkin’s lymphoma [18]. In this case, the initial MRI taken at the time of paraparesis revealed a diffuse fatty appearance of the vertebral bone marrow. The last MRI 8 months later showed the typical double-line sign within the T9eT11 vertebral bodies without vertebral collapse confirming the delayed appearance of this sign. In the early stages of bone marrow necrosis (BMN), a rare clinicopathologic entity occurring before the diagnosis of malignancy, after chemotherapy or at tumour recurrence, MRI appearances can be indistinguishable from avascular necrosis but trephine biopsy confirms necrosis of the myeloid tissue [21,22]. Bone marrow necrosis usually presents with bone pain (80% of cases), fever (70%), and fatigue. The prognosis is generally considered poor, death occurring within weeks or months [21,22]. In our case, a normal PET and radionuclear bone scan and the presence of the spinal double-line sign at several levels was useful in differentiating multiple vertebral osteonecrosis from other malignant conditions, and in particular with lymphomatous bone marrow involvement. Biopsy didn’t revealed malignancy or bone marrow necrosis but only aseptic osteonecrosis. In combination with multiple vertebral involvements, this sign suggested a systemic cause. The pathogenesis of multiple osteonecrosis is not well understood. Because of the normal radionuclear bone scan at the time of diagnosis and a favourable evolution 18 months later, we believe that osteonecrosis occurred during chemotherapy favoured by steroids (total dose of prednisone: 3774 mg from July 2003 to December 2003). Osteoporosis preceding the diagnosis of lymphoma must be emphasised, but we cannot exclude the role of the underlying hematologic malignancy as suspected in some cases of bone marrow necrosis [21]. As MRI is increasingly used in the evaluation and follow-up of bone marrow diseases, these MRI features will be encountered more often and perhaps become better understood. 4. Conclusion In conclusion, our observation of vertebral osteonecrosis offers several interesting aspects. Multifocal involvement without vertebral collapse, presence of a double-line sign and absence of a cleft sign on MRI is strongly in favour of a systemic origin for the osteonecrosis. This has rarely been described in the spine. Our unusual presentation of histologically proven osteonecrosis is also consistent with recent data [8,13] suggesting that the vertebral cleft, considered as pathognomonic of vertebral osteonecrosis, results from vertebral non-union rather than vertebral osteonecrosis.
Supplementary material Supplementary material (Figs. S1aec and S2) associated with this article can be found at http://www.sciencedirect.com, at doi:10.1016/j.jbspin.2007.05.010.
344
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References [1] Maldague BE, Noel HM, Malghem JJ. The intravertebral vacuum cleft: a sign of ischemic vertebral collapse. Radiology 1978;129:23e9. [2] Resnick D, Niwayama G, Guerra J, et al. Spinal vacuum phenomena: anatomical study and review. Radiology 1981;139:341e8. [3] Theodorou DJ. The intravertebral vacuum cleft sign. Radiology 2001;221:787e8. [4] Dupuy DE, Palmer WE, Rosenthal DI. Vertebral fluid collection associated with vertebral collapse. AJR Am J Roentgenol 1996;167: 1535e8. [5] Baur A, Sta¨bler A, Arbogast S, et al. Acute osteoporotic and neoplastic vertebral compression fractures: fluid sign at MR imaging. Radiology 2002;225:730e5. [6] Zurlo JV. The double-line sign. Radiology 1999;212:541e2. [7] Queinnec JY, de Bray JM, Audran M, et al. Vertebral osteonecrosis. Concerning 3 cases, 1 complicated by spinal cord compression and 2 associated with another necrotic localization. Rev Rhum Mal Osteoartic 1985;52:1e5 (French). [8] Kim DY, Lee SH, Jang JS, et al. Intravertebral vacuum phenomenon in osteoporotic compression fracture: report of 67 cases with quantitative evaluation of intravertebral instability. J Neurosurg (Spine1) 2004;100: 24e31. [9] Chevalier X, Wrona N, Avouac B, et al. Thigh pain and multiple vertebral osteonecrosis: value of magnetic resonance imaging. J Rheumatol 1991;18:1627e30. [10] Chou LH, Knight RQ. Idiopathic avascular necrosis of a vertebral body. Case report and literature review. Spine 1997;22:1928e32. [11] Mc Kiernan F, Faciszewski T. Intervertebral clefts in osteoporotic vertebral compression fractures. Arthritis Rheum 2003;48:1414e9.
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