Scintigraphic diagnosis of sacral fractures

The H- or butterfly-pattern of uptake in the sacrum on Tc-99m-methylene diphosphonate bone scintigraphy is typical of fractures of the body of the sacrum that involve the sacral alae. This report describes four patients with a focal linear or curvilinear pattern of uptake in sacral fractures without alae involvement. This pattern differs from that associated with metastases in the sacrum, which typically has a random pattern. Recognition of this scintigraphic linear dot pattern of uptake in horizontal fractures in the inferior body of the sacrum is useful for detecting fractures without alae involvement that are not readily apparent on radiographs.     

MRI of occult sacral insufficiency fractures following radiotherapy

Following radiation therapy, marrow abnormalities noted on magnetic resonance imaging (MRI) are frequent and may mimic metastases. Specific radiotherapy changes are usually easily identifiable; however, traumatic lesions cause more interpretive difficulties. We assessed the incidence and MRI characteristics of insufficiency fractures in this population. During a 5-year span (1987–1991), 546 patients received pelvic radiotherapy for primary malignancies. MRI was performed in 25 of these patients at least 3 months after treatment. The mean dose in this group was 53 Gy. These MRI scans were retrospectively reviewed for the appearance of the sacrum with particular attention to the presence of insufficiency fractures. This was correlated with clinical course and scintigraphic findings. Presumed insufficiency fractures on MRI paralleled the sacral side of the sacroiliac joint, enhanced with Gd-DTPA, were most prominent or initially seen anteriorly, and had ill-defined margins on all imaging sequences. The incidence of occult sacral insufficiency fractures was at least 20%. Insufficiency fractures of the sacrum in the post-radiotherapy patient are a relatively frequent occurrence which can mimic metastases. Consideration of this phenomenon and knowledge of differential features may avoid overdiagnosis of osseous metastases.     

Honda sign and variants in patients suspected of having a sacral insufficiency fracture

PURPOSE: The purpose of this study was to reassess whether the Honda sign (HS) and its variants on bone scans can be used to differentiate an insufficiency fracture (IF) of the sacrum from a metastasis and to evaluate extrapelvic tracer accumulation in patients suspected of having a sacral IF. METHODS AND MATERIALS: We retrospectively reviewed 34 bone scans of 26 patients suspected of having a sacral IF between January 1998 and June 2003. RESULTS: Twenty-four of the patients had a sacral IF and 1 had a sacral metastasis from prostate cancer and another from lung cancer. The bone scans of only 15 (63%) of the 24 patients with a sacral IF exhibited the HS, 8 (33%) scans exhibited variants, and 4 (4%) scans showed whole-sacrum uptake. One of the 2 patients with metastasis exhibited the HS and the other exhibited a variant. The sensitivity and positive predictive value of HS plus its variants as diagnostic criteria for sacral IF were 96% and 92%, respectively. Seventeen patients (71%) had extrasacral accumulation. The most common site was the pubic bone (50%, 12 of 24), and the second most common site was the spine (46%, 11 of 24), where the accumulation was the result of a compression fracture or degenerative joint disease of the spine. CONCLUSIONS: A "Honda sign or variation" with evidence of fractures elsewhere or no evidence of other metastatic disease should be strong evidence for a sacral insufficiency fracture. The likelihood of having a solitary metastasis to the sacrum is small.     

Pubic and sacral insufficiency fractures: clinical course and radiologic findings

Distinctive vertical insufficiency fractures of the pelvis were found in nine osteopenic patients. Each patient had subacute pelvic pain without antecedent trauma. The sacral fractures healed fairly quickly, but the pubic fractures often had a protracted course. Eight patients had combined sacral and pubic fractures; one had only sacral alar fractures. In three patients the sacral fractures preceded the pubic fractures by 3-4 months. All nine patients had skeletal demineralization due to metabolic bone disease, radiation therapy, or multiple myeloma. Recognition of the association between pubic and sacral insufficiency fractures should aid in recognizing the diffuse nature of the skeletal disease so that unnecessary biopsy of the fracture sites can be avoided.     

Vacuum phenomena in insufficiency fractures of the sacrum

Objective. Insufficiency fractures of the sacrum are found in women who have undergone radiation therapy to the lower abdomen as well as those suffering from osteoporosis of postmenopausal, steroid-induced, or primary biliary cirrhosis-related origin. Increased up-take in bone scintigraphy and osteolytic changes in these fractures can be misinterpreted as bone metastases, leading to unnecessary biopsies and other procedures in the ensuing search for non-existent primary tumor.Patients. In eight female patients averaging 69.4 years of age, insufficiency fracture of the sacrum was diagnosed by computed tomography (CT) and bone scintigraphy. Three underwent a total of five MRI examinations. Malignancy was excluded by histology in two patients and follow-up of at least 6 months in the remainder. Retrospective analysis of CT scans of 13 patients with metastases in the sacrum revealed no vacuum phenomena.Results. In seven of eight patients with insufficiency fracture of the sacrum, vacuum phenomena were shown on CT examination. The gas was localized centrally within the ventral part of the fracture in three patients; gas was located in ten adjacent sacro-iliac joints of six patients.Conclusions. The vacuum phenomenon may be an incidental finding in osteoarthritis of the sacro-iliac joint, but it has not been previously recognized in IFS. The presence of intra-articular vacuum phenomena in the sacro-iliac joints in combination with a sacral fracture and vacuum phenomena located within the sacral fracture supports a diagnosis of insufficiency fracture or may indeed be the clue by which this diagnosis is established. Insufficiency fractures of the sacrum are a well-known complication in women who have undergone radiation therapy of the pelvis or are suffering from postmenopausal, steroid-induced, or primary biliary cirrhosis-related osteoporosis [1–11]. These fractures are characterized by increased activity on radionuclide bone scans. The lateral masses of the sacrum contain large amounts of hematopoetic bone marrow and are therefore often the site of bone metastasis. Increased uptake in bone scintigraphy in lateral masses of the sacrum and osteolytic destructions on radiographs and computed tomography (CT), especially in patients with a history of a tumor elsewhere, are suggestive of skeletal metastasis, prompting biopsies and additional diagnostic procedures to find a primary tumor [2]. We present seven out of eight patients with insufficiency fractures of the sacrum, in whom we observed vacuum phenomena within the fracture or in the adjacent sacroiliac joints, indicating the benignity of the lesion. This phenomenon has not been recognized previously.     

Magnetic resonance appearance of sacral insufficiency fractures

Insufficiency fractures of the sacrum are a commonly recognized form of stress fracture typically occurring in elderly patients. As such patients usually present with low back pain, MR imaging is often performed initially as a means of evaluation. We present 5 patients with sacral insufficiency fractures imaged with MR. Metastatic disease was a leading clinical suspicion as all patients were elderly and three had known primary neoplasms. T₁-weighted sequences demonstrated bands of decreased signal intensity, usually paralleling the sacral aspect of the sacroiliac joints and occasionally occurring as a horizontal band across the sacral body. Four of five patients underwent further evaluation with computed tomography (CT) or nuclear bone scanning, which confirmed the diagnosis of sacral insufficiency fracture. We conclude that MRI is sensitive but not specific in detecting sacral insufficiency fractures. As MR imaging is rapidly becoming the method of choice for evaluating back pain, it is important to consider this diagnosis in elderly persons.     

Fatigue fractures of the sacrum in children: two case reports and a review of the literature

We present the clinical and radiological features of two children with fatigue fractures of the sacrum. Both patients were active, had no underlying bone disease and presented with insidious onset of low back pain. Plain radiography was non-contributory to the diagnosis. In both patients a focal area of increased activity was present in the lateral aspect of the sacrum on bone scintigraphy, which corresponded to linear medullary sclerosis in the sacral ala demonstrated by computed tomography. Magnetic resonance imaging in one patient revealed a linear signal void in the sacral ala on T1- and T2-weighted images. This was surrounded by diffuse low marrow signal on T1-weighted images, and increased marrow signal on T2-weighted images. Fatigue fractures of the sacrum should be considered in the differential diagnosis of low back pain in children. An awareness of their appearance on magnetic resonance imaging is important as this modality is increasingly utilised, particularly in children.     

Solitary hot spots in the ribs on bone scan: value of thin-section reformatted computed tomography to exclude radiography-negative fractures

PURPOSE: The purpose of this study was to classify solitary, scintigraphy-positive and radiography-negative rib lesions and to clarify the features of rib fractures by using thin-section reformatted helical computed tomography (CT). METHODS: Forty-seven patients whose whole-body bone scans showed a solitary hot spot in a rib as their first abnormal scintigraphic finding and whose plain radiograph showed negative or indeterminate results were examined by thin-section reformatted CT. Final diagnosis was based on follow-up over a 20-month period. RESULTS: The final diagnosis included 17 cases of fractures where CT findings were fracture line, focal sclerosis, and callus formation. Fourteen ribs demonstrated intramedullary, focal osteosclerosis, and 8 ribs did not demonstrate any abnormalities. Four metastatic lesions appeared as intramedullary mixture of osteolysis and osteosclerosis, or bone destruction. Four intramedullary lesions with cystic appearance remained unchanged. CONCLUSIONS: Thin-section reformatted helical CT delineated minute, radiographically occult fractures of the rib. Excluding fractures, helical CT can avoid further unnecessary examinations.     

Radiation-induced insufficiency fractures of the pelvis: evaluation with 99mTc-methylene diphosphonate scintigraphy.

99mTc-methylene diphosphonate (99mTc-MDP) bone scans in 80 patients, 30-80 years old (average, 62 years old) with uterine cancer who received high doses of radiation (10-60 Gy; average, 46 Gy) were reviewed retrospectively to evaluate the frequency of pelvic insufficiency fractures caused by radiotherapy and to study the appearance of the fractures on bone scans. Bone scans in 29 of 80 patients showed abnormalities in the pelvis: insufficiency fractures were identified in 27 patients (34%) and osseous metastases were found in two patients (3%). The fractures and metastases were diagnosed by CT and were confirmed by observing the patients' clinical courses. Fractures were identified in 27 (39%) of 69 postmenopausal women and in none of 11 premenopausal patients (p greater than .05). Fractures were found in 21 (84%) of 25 patients who had pelvic pain and in six (11%) of 55 patients who were asymptomatic (p greater than .001). Scintigrams in patients with fractures showed more than one fracture in most patients (85%), and fractures were often symmetric (67%). Scintigrams in two patients with osseous metastases showed increased activity in an iliac wing that was outside the radiation field. Our results suggest that a marked increase in insufficiency fractures occurs after radiation therapy, especially in postmenopausal patients. A symmetric area of increased uptake of radionuclide is a characteristic scintigraphic appearance of an insufficiency fracture.     

Cauda equina syndrome presentation of sacral insufficiency fractures

Introduction Sacral insufficiency fractures are a well recognised cause for low back, buttock and groin pain in the elderly. However, over a 4 year period, four patients have presented with symptoms of cauda equina syndrome, who were found on investigation to have acute sacral insufficiency fracture without any other aetiological spinal abnormality. Patients and method Four patients who presented to the spinal surgeons of our institution with symptoms of cauda equina syndrome were referred for spinal MR. Sagittal and axial T1 and T2 weighted turbo spin echo sequences of the lower thoracic and lumbar spine were performed on all patients. Subsequent studies included MR of the sacrum supplemented where appropriate by CT and technetium MDP bone scintigraphy. Results No evidence of a compressive lesion of the lower thoracic or lumbar spine was present in any of the four patients. Dedicated MR examination of the sacrum in these patients revealed unilateral acute insufficiency fractures involving zone 1 from S1 to S3 extending from the sacro-iliac joint to the lateral margin of the sacral foramen. There was no evidence of compression of the sacral nerve roots. The possible mechanism for the symptomatic presentation is discussed. Conclusion Sacral insufficiency fractures should be excluded in elderly or osteoporotic patients presenting with cauda equina syndrome who have no evidence of compression in the thoraco-lumbar MR studies.     

Osteoradionekrose nach Strahlentherapie gynäkologischer Tumoren

AIM: Insufficiency fractures of the pelvis are a well known but rare and frequently misinterpreted radiation sequela. The clinical features and possible risk factors were investigated. PATIENTS AND METHODS: 71 of living 82 patients, who were treated 1986-1994 for gynecologic tumors were clinically examined. 47 patients underwent also bone scan, CT of the pelvis and 13 patients had osteodensitometry. All patients had been treated with adjuvant (n = 29) or curative intent (n = 18) by d.v. fields with 18-MV photons, with 46 Gy in 23 fractions plus brachytherapy (15-39 Gy). Median follow-up was 36 months. RESULTS: Seven patients developed pelvic insufficiency fractures 11 months (median, minimum 2 months) after treatment. All patients complained of moderate to severe pelvic pain, which resolved after 5-28 months without specific therapy in five of seven patients. At first examination all but one bone scan showed extremely increased uptake in the os sacrum and/or iliosacral joints, correlating CT scans demonstrated small fractures and bony destruction. Four of the asymptomatic 40 patients with complete radiologic examinations had medium uptake in bone scan (CT normal). Three of four examined patients with insufficiency fractures and seven of nine patients without insufficiency fractures had osteoporosis. CONCLUSION: In women who present with pelvic pain after radiotherapy for gynecologic tumors bony destruction and fractures may be indicative of a late radiation effect rather than osseous metastasis, even after early onset of symptoms.     

Clinical and scintigraphic evaluation of insufficiency fractures in the elderly

BACKGROUND: We have undertaken a retrospective review of 1017 Tc-methylene diphosphonate (Tc-MDP) skeletal scintigrams performed in patients over 70 years of age in order to identify those with insufficiency fractures. METHOD: Patients with the diagnosis of insufficiency fracture then underwent clinical follow-up of 2 years for mortality, which was compared to the national aged-matched population. RESULTS: One hundred and ninety-four patients were found to have scintigraphic evidence of fractures categorized as insufficiency fractures. Typical H-shaped sacral fractures were present in only 17 (4%) patients. Multiple sites of fracture were observed in 114 patients; the commonest being in the vertebrae. Radiological corroboration was available in 161 patients (83%) and bone scintigraphic findings were concordant with at least one of plain radiograph, computed tomography or magnetic resonance imaging in 107 (55%) patients. Of the 48 patients with insufficiency fracture who had undergone measurement for bone mineral density (BMD), 38 were found to have osteoporosis/osteopenia. Eighty-six patients died during the follow-up period, which was markedly higher than expected in the age-matched population. There was no definite relationship between the mortality in insufficiency fracture and BMD or the number of fractures. CONCLUSIONS: Our findings demonstrate that insufficiency fractures are common in the elderly and generally occur at multiple sites. The typical H-shaped fractures are rare and their absence should not lead to any mistaken diagnosis. The patients with insufficiency fractures appear to have poor survival but this does not appear to have any significant relationship with either BMD or the number of fractures. Finally, insufficiency fracture is an important diagnosis to make because survival may be improved if specific management is used.     

The sacrum: pathologic spectrum, multimodality imaging, and subspecialty approach.

The sacrum is a structure that is imaged by both general and subspecialty radiologists. A wide variety of disease processes can involve the sacrum either focally or as part of a systemic process. Plain radiographs, although limited in evaluation of the sacrum, should be carefully examined when abnormalities of the sacrum are suspected. Cross-sectional imaging, particularly computed tomography and magnetic resonance (MR) imaging, plays a crucial role in identification, localization, and characterization of sacral lesions. Congenital lesions of the sacrum, including sacral agenesis and meningocele, are optimally imaged with MR. The most common sacral neoplasm is metastatic disease. Primary neoplasms of the sacrum, which include giant cell tumor, chordoma, and teratoma, are infrequent. Infection of the sacrum or sacroiliac joint is most often due to contiguous spread from a suppurative focus. A wide variety of arthritic disorders such as ankylosing spondylitis and osteoarthritis can involve the sacroiliac joints as part of a localized or systemic process. Sacral fractures related to acute trauma or repetitive stress are difficult to diagnose and treat. Knowledge of these abnormalities and familiarity with the imaging of these processes will allow radiologists of all subspecialties to contribute to the diagnosis and management of sacral disorders.     

Bone stress lesions in ballet dancers: scintigraphic assessment

Ballet dancers are athletes susceptible to ligamentous and bony injury. We reviewed retrospectively the bone scans (technetium-99m methylene diphosphonate) of 23 ballet dancers with pain in the back and/or lower extremities to determine the usefulness of scintigraphy in the detection of stress lesions of bone. The scintigraphic studies in 19 dancers identified multiple areas of stress injury in both symptomatic and asymptomatic locations. Thirteen dancers had 22 stress fractures (microfractures of trabeculae with associated bone repair) manifested by an intense focus of increased uptake of radiopharmaceutical, and 19 dancers had stress reactions (areas of accelerated remodeling and resorption of bone) demonstrated by diffusely increased uptake of radiotracer. Ten of the 13 dancers with stress fractures were symptomatic and six of the 19 dancers with stress reactions were symptomatic. The radiographs of 10 dancers with positive bone scans were normal or showed no distinction between acute and chronic injuries. Stress fractures were most prevalent in the feet, and stress reactions were most prevalent in the tibiae. The study confirmed that ballet dancers sustain significant bone stress in their legs and feet. Our results show that scintigraphy can be used to detect stress fractures and stress reactions at both symptomatic and asymptomatic sites in this population.     

骶骨神经源性肿瘤的X线平片及CT分析（附6例报告）

目的：通过分析骶骨神经源性神经肿瘤的Ｘ线和ＣＴ表现，提高其诊断水平，材料与方法，６例骶骨神经源性肿瘤，其中神经鞘瘤４例，恶性肿瘤鞘瘤１例，神经纤维瘤１列，对其平片及ＣＴ表现进行分析，结果：平片表现，骶骨神经源性肿瘤多位于上部骶椎，偏侧性生长，骶孔或骶骨内奢望生扩大破坏或变形及多囊状膨胀溶骨性骨质破坏，边缘骨质硬化，ＣＴ表现，膨胀的溶骨破坏区被软组织肿块充填，骨壁变薄，肿块无钙化，肿瘤破坏骨壁或骶孔     

Role of MRI in the diagnosis of insufficiency fractures of the sacrum and acetabular roof

 Objective. To review the risk factors and the radiological appearance of insufficiency fractures of the sacrum and acetabular roof. Design and patients. Twenty patients with sacral and acetabular roof insufficiency fractures were reviewed retrospectively. There were 16 women (80%) and 4 males (age range 48–86 years, excluding an 8-year-old boy). Thirteen patients had a known tumour, and nine had received pelvic irradiation. All patients, except one who was asymptomatic, presented with low back or hip pain. In patients with a known tumor, metastases were suspected. Plain radiography (20), bone scintigrams (16), MR examinations (20), and bone densitometry (14) were performed. Nine patients also each had a CT scan. Results and conclusions. In three cases the CT scan performed 10–25 days after onset of symptoms was interpreted as normal. MR examination performed a few days after the CT scan showed in each of these three patients a fracture line with a band of edema. Scintigraphy was very sensitive, but the H-shaped pattern of sacral uptake, specific for an insufficiency fracture, was detected in only three of 16 cases. The earliest MR sign was medullary edema, seen as early as 18 days after the onset of symptoms. On spin echo (SE) T1-weighted images (T1WI), the hypointense signal of edema could mask a fracture line. On SE T2WI the fracture line could be detected within the hyperintense edema (10 of 17 patients with examinations including SE T2WI). However, in four patients a fracture of the sacrum was not seen on T2WI, these having been obtained in the axial plane. For this reason, intravenous gadolinium was injected, revealing a fracture line in 12 of 14 examinations, or fat suppression sequences were performed, revealing a fracture line in five of five cases. The total number of fractures detected was 17 [15 fractures of the sacrum (bilateral in 10 cases) and two of the acetabular roof]. At a later stage, the edema resolved and the fracture was clearly seen. The two cases of fracture of the acetabular roof were easily recognized at MRI, particularly in the sagittal plane.     

Bone scintigraphy in preschool children with lower extremity pain of unknown origin.

Small children often cannot describe the location of bone pain for parents or physicians. Bone scans were performed in 56 children under five years of age with lower extremity pain and/or gait abnormalities of unknown etiology. Patients with fever, and those known to have infection, child abuse, malignancy, and/or radiographic abnormalities were excluded. Thirty patients had abnormal bone scans. Abnormalities included evidence of hip synovitis (4), femoral head avascularity (2), various proximal femoral abnormalities (3), knee synovitis (3), toddler's fracture (1), various tibial or fibular abnormalities (4), and various abnormalities of the tarsal bones (16). Tarsal bone abnormalities included four with abnormal calcaneal uptake and nine with abnormal uptake in or adjacent to the cuboid bone. Correlative imaging studies were available for 26 sites, and focal bone findings were noted at only five locations. Tarsal bone abnormalities accounted for over half of the scintigraphic abnormalities in these preschool children with gait abnormalities. Abnormal uptake in/or adjacent to the cuboid bone was common and probably represented stress injury.     

Tc-99m HMDP bone scintigraphic findings in association with concurrent serum osteocalcin measurements

Osteocalcin is a noncollagenous bone protein produced by osteoblasts. Increase in serum osteocalcin level reflects osteoblast activity with acceleration of bone formation. To evaluate the correlation of Tc-HDP bone scintigraphic findings and concurrent serum osteocalcin, serum osteocalcin values of 40 consecutive patients were measured by radioimmunoassay at the time of initial referral for bone studies. These patients, all males aged 23-93, were studied for various disease entities, including prostate carcinoma. The results of the assay were categorized into three groups (gp) as follows: 17 at normal (1.8 to 6.6 ng/ml) level (gp 1), 21 low (gp 2), and two high (gp 3). Only one bronchogenic carcinoma patient with a high level had a right iliac lesion suggesting metastasis. The bone scans of nine patients with normal or low levels showed positive metastases. Two patients with stress fractures as shown on bone scans had normal levels. The images of patients with disparity between serum osteocalcin and positive bone lesions may be interpreted as follows: Instead of osteoblastic activity resulting in the synthesis and/or release of osteocalcin, area(s) of increased uptake in the bone scan may be predominantly reflecting increased regional blood flow and decreased sympathetic tone, resulting in an increase in bone-agent deposition.     

Sacral fractures: a potential pitfall of FDG positron emission tomography

OBJECTIVE: Positron emission tomography (PET) with FDG is useful for tumor imaging, but false-positive results can occur. The purpose of this study is to describe three oncology patients with sacral fractures in whom FDG uptake in the sacrum increased on PET. CONCLUSION: Sacral fractures can show increased uptake of FDG on PET. Therefore, correlative cross-sectional imaging is necessary to avoid the erroneous diagnosis of sacral metastases on PET and prevent inappropriate treatment of patients.