Computed tomography compared to magnetic resonance imaging in occult or suspect hip fractures. A retrospective study in 44 patients

Background

Computed tomography (CT) for evaluation of occult and suspect hip fractures has been proposed as a good second-line investigation. The diagnostic precision compared to magnetic resonance imaging (MRI) is unclear.

Purpose

To compare the diagnostic performance of CT and MRI in a retrospective study on patients with suspect and occult hip fractures.

Material and methods

Forty-four elderly consecutive patients with low-energy trauma to the hip were identified where negative or suspect CT was followed by MRI. Primary reporting and review by two observers as well as the diagnostic performance of the two modalities were compared. Surgical treatment and clinical course were used as outcomes.

Results

Compared to the primary reports, the CT reviewers found fewer normal and no suspect cases. MRI changed the primary diagnoses in 27 cases, and in 14 and 15 cases, respectively, at review. There was no disagreement on MRI diagnoses.

Conclusion

In our patient population, MRI was deemed a more reliable modality for hip fracture diagnosis in comparison to CT. For clinical decision making, MRI seems to have a higher accuracy than CT. A negative CT finding cannot completely rule out a hip fracture in patients where clinical findings of hip fracture persevere.

Key Points

? Experience is highly influential in diagnosing occult or suspect hip fractures at CT ? Inconclusive hip CT shows high inter-rater reliability at experienced review ? There was low diagnostic accuracy via CT compared to MRI for all interpreters ? Hip fractures can readily be diagnosed at MRI regardless of radiological experience

     

High clinical utility of computed tomography compared to radiography in elderly patients with occult hip fracture after low-energy trauma

To evaluate the clinical utility of computed tomography (CT) compared to radiography in evaluating suspect or missed hip fractures in elderly after low-energy trauma. One hundred ninety-three hip CT examinations performed in two trauma centers during 3 years of evaluation of clinically suspect or occult hip fracture within 24 h of negative or suspect radiography were retrospectively reviewed. Consensus CT diagnosis by three observers was compared to clinical outcome and in some cases also further imaging. All patients were elderly and had sustained a low-energy trauma. Eighty-four examinations revealed no fracture. Follow-up was uneventful but for two patients who had been operated. Thirty-nine of 41 cervical hip fractures were surgically or otherwise confirmed, two cases were not operated due to week-old trauma and moderate symptoms. Twenty-nine of 68 trochanteric fractures or avulsions were confirmed surgically. Computed tomography has a high clinical utility as it can detect nearly all clinically suspect but radiographically negative cervical hip fractures as well as most trochanteric fractures and avulsions. A negative CT is near-perfect in ruling out a hip fracture requiring surgery.     

质子脂肪抑制序列在四肢隐性骨折中的诊断价值

目的探讨质子脂肪抑制序列(PDFASAT)在四肢隐性骨折中的诊断价值。方法31例四肢关节外伤患者在伤后45d内均行X线平片及多序列高场强(1．5T)MR检查，检查序列包括快速SE T1WI、T2WI，PDF ASAT等。受伤部位为膝关节21例，髋关节6例，肘关节1例，肩关节2例，踝关节1例。结果31例X线平片均未见明显骨折征象。MR检查发现：21例(21／31)膝关节受伤病例中腓骨近端隐性骨折10例，胫骨近端4例，股骨髁7例；6例(6／31)髋关节受伤病例中粗隆问隐性骨折2例，股骨颈隐性骨折2例，髋臼隐性骨折2例；1例(1／31)肘关节受伤病例显示肱骨远端隐性骨折；2例(2／31)肩关节受伤病例显示肱骨近端隐性骨折；1例(1／31)踝关节受伤病例显示腓骨远端隐性骨折；MR信号主要表现为T1WI、T1WI呈细线状、条带状低信号影，PDFASAT呈更清晰锐利的细线状、条带状高信号影，PDFASAT序列更易认识辨别。结论MRI能发现早期至慢性期隐性骨折的存在，如临床强烈提示骨折可能而X线检查阴性者，MR检查的PDFASAT序列是明确诊断的最佳序列。     

CT对髋关节与膝关节隐匿性骨折的诊断价值

目的 评价CT对髋、膝关节隐匿性骨折的诊断价值。方法 30例临床上疑有髋、膝关节隐匿性骨折患均经CT检查。对全部患者的CT表现进行了回顾性分析，并与X线平片相对照。结果 30例患者X线平片检查均为阴性，而CT横断面图像均明确地显示了骨折。30例中，髋关节骨折14例（髋臼骨折8例，股骨头骨折4例，股骨颈骨折2例），膝关节骨折16例（胫骨平台骨折8例，胫骨髁间隆起基底部骨折3例，股骨外髁骨折2例，股骨内髁骨折1例，髌骨骨折2例）。结论 CT对髋、膝关节隐匿性骨折的诊断具有很高的准确性，且明显优于X线平片。当临床怀疑骨折而X线未显示或显示不清者，应进行CT检查。     

Prevalence and patterns of occult hip fractures and mimics revealed by MRI

OBJECTIVE: The diagnosis of hip fractures can be difficult on radiography alone. MRI is frequently used to confirm or deny the presence of a minimally displaced hip fracture. This study evaluates the patterns of injury seen on MRI that are difficult to diagnose on radiography. MATERIALS AND METHODS: MRIs of 73 patients who were examined for possible hip fractures and whose radiographic findings were negative or equivocal for hip fracture were reviewed. Seventy-six studies were performed in 73 patients who were between 24 and 102 years old. MRIs were evaluated for the presence and location of bone or soft-tissue injury. Muscle injuries were categorized on the basis of location and type of injury. RESULTS: Forty-six percent (35/76) of the studies showed subtle fractures. Seventeen fractures were in the proximal femur and 18 in the innominate bone. Soft-tissue abnormalities were common, found in 65% of the studies. Twenty percent of the MRI findings were considered normal because there was no apparent finding on the images to explain the patients' symptoms. CONCLUSION: Soft-tissue abnormalities are commonly seen alone or in association with subtle fractures on MRI in the evaluation of patients with a clinical suspicion of hip fracture. MRI is recommended for all symptomatic patients whose radiographic findings are negative for hip fracture.     

隐性骨折的MRI分析

目的 探讨隐性骨折的MRI诊断价值。方法 16例急性外伤患者均行X线平片检查及MRI检查,3例同时行CT检查,受伤部位分别为股骨髁3例,胫骨近端8例,胸腰段椎体5例。结果 本组16例X线平片均未见骨折征像;11例（11／16）股骨髁及胫骨近端受伤病例中3例（3／16）T1WI见骨皮质下线状信信号带改变,8例（8／16）显示由关节面下向骨干走行的不规则条状、紊乱低信号改变;在T2WI上对应于T1WI低信号区仍表现为相应形状的低信号,且在低信号周围可见高信号水肿改变;T1脂肪抑制序列扫描显示水肿带信号明显增强、增宽。2例股骨髁和1例胫骨近端病例同时行CT检查,示周围软组织肿胀,未见确切骨折征像。5例（5／16）胸腰段椎体MR T1WI、T2WI示椎体中央有水平方向走行的线状低信号带,在T2WI低信号周围可见高信号水肿。结论 MRI能够早期确诊隐性骨折,若患者临床症状、体征不能除外隐性骨折,X线检查后行MRI应为最佳的检查手段。     

The advantages of MRI in the detection of occult hip fractures

While the displaced hip fracture can be visualized easily by plain radiography, the non-displaced fracture may be radiographically occult and require different imaging modalities, e.g., MRI for proper visualization. The accuracy of readers and cost advantages of utilizing MRI have not been assessed. Therefore, we undertook a study of these factors. The medical records of all patients who had visited the emergency room from June 2002 until May 2003 with a clinically suspected hip fracture, negative or equivocal plain film and subsequent MRI examination were retrospectively reviewed. Two senior and two junior radiologists independently evaluated both the MR images and radiographs of all 33 patients in a blinded study. One of three possible evaluations was described for the images of each modality: absence, presence or possibility of fracture. The economic consequences of using MRI in the detection of occult hip fractures were calculated. For all four doctors participating in this study, MRI proved to be far more sensitive and specific in the detection of occult hip fractures than radiography. Using the MR images, the senior radiologists identified the occult hip fracture patients with 100% accuracy and were in complete agreement. The agreement between junior and senior radiologists was high (average =0.75). MRI also detected soft tissue injuries in 39% of the patients that could not be identified with radiography. Adoption of the new protocol using MRI saves hospitals from €242 to 627 per patient. By shortening the time to diagnosis and permitting a superior visualization of both bone and soft tissue injuries, MR imaging prevents unnecessary hospitalization and delays in definitive treatment. MR images should be assessed by senior radiologists.     

MRI of pediatric growth plate injury: correlation with plain film radiographs and clinical outcome

Purpose. To evaluate pediatric growth plate injuries with conventional radiographs and magnetic resonance imaging (MRI). To review potential clinical impact of MRI on subsequent patient management and outcome. Methods. Fourteen patients with known or suspected growth plate injury were studied. Each patient underwent imaging by conventional radiography and MRI within 2 weeks of injury. Findings on conventional radiographs and on MR images were compared and then correlated with subsequent management and outcome at a mean of 12 months. Results. Direct visualization of cartilage afforded by MRI improved evaluation of growth plate injury in each case. MRI changed Salter Harris classification or staging in 2 of 9 patients with fractures visualized on conventional radiographs, allowed the detection of radiographically occult fractures in 5 of 14 cases, and resulted in a physical change in management in 5 of the 14 patients studied. Conclusion. MRI has an important role in the evaluation of acute pediatric growth plate injury, particularly when diagnostic uncertainty persists following the evaluation of conventional radiographs. MRI allows detection of occult fractures, may alter Salter Harris staging, and in the reported study it frequently resulted in a change in patient management.     

低场MRI在膝关节隐匿性骨折中的实验研究

目的:探讨低场MRI对膝关节隐匿性骨折的诊断价值。方法:实验羊膝关节3对,使每对中一只人工用钝器横向适度砸伤,且于受伤后6～12 h将羊宰杀后取出双膝关节,行DR摄片及低场MRI常规序列检查,然后送病理切片行常规HE染色检测观察。结果:3例实验羊膝关节隐匿性骨折患者T1WI呈低信号,或内见高信号,T2*OWI呈低或高信号,T2WI呈等或高信号,在WFT2*水像或STIR序列上病变较正常的骨组织信号更高,呈高信号。病理切片HE显示羊膝关节镜下可见明显骨小梁断裂,周围软组织高度水肿、渗出及出血,骨板结构正常。结论:低场MRI能清楚显示膝关节隐匿性骨折的病变特点及严重程度,可作为膝关节隐匿性骨折的重要检查方法。     

Fractures easily missed by conventional radiographic diagnosis]

Although conventional radiography is the mainstay for diagnosing fractures, there are multiple conditions in which a fracture can be overlooked by the radiologist. This report focuses on the radiographic findings of various presentations of fractures including (1) minimally displaced fractures, (2) avulsion fractures, (3) stress fractures, (4) incomplete fractures and physeal injuries in children, and (5) occult fractures complicated with overt injury. Radiologists need to be familiar with these relatively common entities and aware of the limitations of radiography for fracture diagnosis; there are cases that can be diagnosed clinically without radiographic findings of cortical disruption. Repeated radiographic examination, CT, or MRI may be indicated depending on the clinical situation. The involvement of radiologists in the routine interpretation of conventional radiographs in trauma settings is encouraged to improve the detection of subtle fractures.     

T2加权预饱和脂肪抑制在椎体隐性骨折中的诊断价值

目的:探讨T2加权预饱和脂肪抑制(T2WI-FS)在椎体隐性骨折中的诊断价值。方法:106例脊柱外伤患者在伤后60天内均行X线平片及多序列高场强(1.5T)MR检查,检查序列包括SE T1WI、快速SE T2WI,T2WI-FS等。受伤部位为颈椎6例,胸椎37例,腰椎63例。结果:106例X线平片均未见明显骨折征象。MR检查发现:6例颈椎受伤病例中隐性骨折7个椎体,37例胸椎受伤病例中隐性骨折51个椎体,63例腰椎受伤病例中隐性骨折69个椎体;MR信号主要表现为T1WI呈水平方向椎体中央条带状低信号影;T2WI呈条带状稍低信号影或等信号影;T2WI-FS呈清晰的更大范围的条带状高信号影,T2WI-FS序列醒目易认识辨别。结论:MRI能发现脊柱椎体早期至慢性期隐性骨折的存在,如临床强烈提示骨折可能而X线检查阴性者,MR检查的T2WI-FS序列是明确诊断的最佳序列。应作为脊柱创伤MR检查的常规序列。     

Prevalence of exclusively and concomitant pelvic fractures at magnetic resonance imaging of suspect and occult hip fractures

Pelvic fractures may occur together with hip fractures as a result of low energy trauma. It is unclear whether they do require special attention. There are conflicting results in the literature about the prevalence of both concomitant hip and pelvic fractures as well as exclusive pelvic fractures. It has been reported that hip fractures and obturator ring fractures are mutually exclusive. To retrospectively analyze the prevalence of exclusively pelvic as well as concomitant hip and pelvic fractures in patients examined with MRI after low-energy trauma in elderly. During 9 years, 316 elderly patients had been examined with MRI for suspected or occult hip fracture after a fall. A fracture was diagnosed when MRI showed focal signal abnormalities in the subcortical bone marrow, with or without disruption of adjacent cortices. One observer reviewed all studies. A second observer verified all studies with hip fractures. Follow-up was available for all but two patients that died prior to hip surgery. The prevalence of concomitant pelvic and femoral neck or trochanteric fractures was statistically compared using chi-squared test for categorical variables. Hip fractures were found in 161 (51 %) patients of which 29 (9 %) had concomitant pelvic fractures. There were exclusively pelvic fractures in 82 (26 %) patients of which 65 (79 %) were on the traumatized side only. In 73 patients, there were no fractures. Occult or suspected hip fractures are not infrequently associated with pelvic fractures. Exclusively pelvic fractures are not uncommon.     

Distinction of long bone stress fractures from pathologic fractures on cross-sectional imaging: how successful are we?

OBJECTIVE: The objectives of our study were to define CT and MRI features that distinguish pathologic fractures from stress fractures and to compare the performance of CT and MRI with radiography. MATERIALS AND METHODS: Two reviewers retrospectively reviewed 45 MR images, 37 CT scans, and 43 radiographs in 59 patients (30 biopsy-proven pathologic fractures and 29 stress fractures followed to resolution). The features observed on MRI were abnormal bone marrow (well-defined, ill-defined); intracortical, periosteal, or muscle T1 or T2 signal; endosteal scalloping; and a soft-tissue mass. The features seen on CT were marrow abnormality and character (well-defined, ill-defined, permeative, moth-eaten), endosteal scalloping, periosteal reaction (benign, aggressive), and a soft-tissue mass. Reviewers rated their confidence for diagnosing a pathologic fracture on a 1-3 scale (< 50%, 50-95%, > 95% sure, respectively) with each technique. Performance of each technique was defined by reviewer accuracy and area under the receiver operating characteristic curve (Az); the frequency with which the MRI and CT features were associated with pathologic and stress fractures was calculated. RESULTS: For both reviewers, accuracy for differentiating pathologic from stress fractures was highest on MRI (accuracy/Az: reviewer 1, 98%/0.97; reviewer 2, 93%/0.99); CT (reviewer 1, 88%/0.83; reviewer 2, 82%/0.90) was less accurate than radiography (reviewer 1, 94%/0.98; reviewer 2, 88%/0.96). On MRI, pathologic fractures compared with stress fractures exhibited well-defined T1 marrow signal (83% vs 7%, respectively; p < 0.001), endosteal scalloping (58% vs 0%, p < 0.001), muscle signal (83% vs 48%, p = 0.026), and a soft-tissue mass (67% vs 0%, p < 0.001). On CT, pathologic fractures compared with stress fractures exhibited marrow abnormality (84% vs 17%, respectively; p = 0.001), endosteal scalloping (44% vs 0%, p = 0.006), and aggressive periosteal reaction (36% vs 0%, p = 0.04). CONCLUSION: MRI is useful for distinguishing pathologic from stress fractures, especially after inconclusive radiographic findings. Specifically, pathologic fractures exhibit well-defined T1 marrow alterations, endosteal scalloping, and adjacent soft-tissue abnormalities.     

Radiographically occult femoral and pelvic fractures are not mutually exclusive: a review of fractures detected by MRI following low-energy trauma

Objectives

The purpose of this study was to review the MRI examinations of a large group of low-energy trauma patients in whom pelvic MRI had detected radiographically occult fractures, in order to characterize prevailing fracture patterns and determine how often co-existing proximal femoral and pelvic fractures were observed.

Methods

All patients having pelvic MRI over 5?years were identified. Word-search software selected 269 MRI reports containing the term ‘fracture’. Further scrutiny identified 168 with diagnosis of fracture. MRI request and imaging record review identified 102 low-energy trauma cases that had MRI for clinical suspicion of fracture despite normal radiographs. Sixty-six cases were excluded for the following reasons: no expressed clinical suspicion of occult fracture; history suggesting high-energy trauma; skeletal co-morbidity hindering acute fracture identification; interval more than 2?weeks between radiographs and MRI. The 102 study MRI examinations, which employed a limited two-sequence protocol, were reviewed. Any fracture that had not been appreciated on radiographs was recorded and characterized as femoral, pelvic, or co-existing femoral and pelvic fractures.

Results

The 102 study cases had a median age of 82?years. The median interval between pelvic radiographs and MRI was 3?days. MRI showed undiagnosed femoral fracture in 48/102 cases (47.1%), sacral fracture in 41/102 (40.2%), and pubic fracture in 55/102 (53.9%). In 11/102 cases (10.8%), MRI showed undiagnosed fractures of both proximal femur and pelvic ring (seven sacral, six pubic bone, two other site fractures). In 10/11 cases with co-existing femoral and pelvic fractures, the femoral fracture was incomplete.

Conclusions

Limited pelvic MRI found a high prevalence of radiographically occult femoral and pelvic fractures in low-energy trauma patients, with clinical suspicion of fracture despite normal radiographs. Co-existing occult femoral and pelvic ring fractures were commonly observed, and in such cases, the femoral fracture was likely to be incomplete and multiple pelvic fractures were typically present.     

MRI对腰椎隐匿性骨折的诊断价值

目的:探讨MRI对腰椎隐匿性骨折的诊断价值。方法:32例急性腰椎外伤患者均行X线检查及MRI检查。结果:本组32例X线平片均未见骨折征像;腰椎受伤椎体分别为L1椎体4例,L2椎体3例,L3椎体7例,L4椎体10例,L5椎体8例;32例病例MR T1WI、T2WI示椎体有水平方向走行的线状低信号带,在T2WI低信号周围可见高信号水肿影S,TIR病灶呈边缘较清的高信号。结论:MRI能清晰显示隐匿性骨折的骨折、水肿,早期准确诊断隐匿性骨折,若患者临床症状、体征明显,X线诊断阴性,不能除外隐性骨折,MRI应为首选最佳的检查手段。     

多层螺旋CT与磁共振成像在细微及隐匿性骨折诊断中的应用

目的探讨多层螺旋CT(MSCT)与磁共振成像(MRI)在细微及隐匿性骨折中的诊断价值。方法对69例车祸伤后,常规X线、普通CT检查阴性,但怀疑有骨折或临床症状明显者行MSCT和MRI检查。结果 MSCT检查发现52例细微骨折,其中鼻骨骨折8例,颅底骨折9例,脊柱骨折6例,肋骨骨折10例、骨关节骨折19例;另17例MSCT检查未见骨折征象,再行MRI检查并诊断为隐匿性骨折,其中脊柱骨折5例,骨关节骨折12例。结论 MSCT检查能发现常规X线与普通CT未能发现的细微骨折,对特殊部位,如颅底、肋骨骨折诊断有明显优势,对骨折的类型、骨折线涉及范围有较准确的诊断;而MRI检查可显示不能被MSCT所发现的骨挫伤及隐匿性骨折。MSCT与MRI联合应用,可为骨折患者的临床治疗及交通事故的医疗鉴定提供可靠的依据。     

Bone SPECT is more sensitive than MRI in the detection of early osteonecrosis of the femoral head after renal transplantation.

We compared the diagnostic sensitivity of (99m)Tc-methylene diphosphonate bone SPECT and MRI in the early detection of femoral head osteonecrosis after renal transplantation. METHODS: The patients were 24 renal allograft recipients who underwent both bone SPECT and MRI within 1 mo of each other because of hip pain but normal findings on plain radiography. SPECT was considered positive for osteonecrosis when a cold defect was detected in the femoral head, and the defect was further classified according to the presence of adjacent increased uptake: type 1 = a cold defect with no adjacent increased uptake; type 2 = a cold defect with adjacent increased uptake. MRI was considered positive for osteonecrosis when a focal region with low signal intensity on T1 images was detected in the femoral head. Final diagnoses were made by surgical pathology or clinical and radiologic follow-up of >1 y. RESULTS: A total of 32 femoral heads, including 24 of 29 painful hips and 8 of 19 asymptomatic contralateral hips, were confirmed as having osteonecrosis. SPECT detected osteonecrosis in all 32 of the femoral heads, resulting in a sensitivity of 100% (32/32), whereas MRI detected osteonecrosis in 21 femoral heads, for a sensitivity of 66% (21/32, P < 0.005). SPECT showed the type 1 pattern in 13 and the type 2 in 19. Ten of the 13 femoral heads with the type 1 pattern were false-negative on MRI, whereas only 1 of 19 with the type 2 pattern was normal on MRI (P < 0.001). There were 6 femoral heads with normal MRI findings and abnormal SPECT findings (type 1 pattern) in 3 patients, for whom hip pain decreased and radiographic findings were normal during follow-up. Follow-up bone SPECT showed a decreasing area of cold defect in 4 femoral heads. CONCLUSION: (99m)Tc-methylene diphosphonate SPECT is more sensitive than MRI for the detection of femoral head osteonecrosis in renal transplant recipients. Bone scintigraphy with SPECT is needed to diagnose osteonecrosis in patients with hip pain despite normal radiography results after renal transplantation. The significance of a transient SPECT abnormality needs to be clarified by further natural history studies.     

关节积脂血征的影像学表现

目的：分析外伤所致关节积脂血征的X线、CT和MRI表现,总结其影像学特征表现。方法：回顾性分析46例关节积脂血征的X线、CT和MRI特点,其中膝关节32例、髋关节4例、肩关节4例、踝关节5例及肘关节1例。结果：仅4例在X线上有特征性表现,CT或MRI上46例关节积脂血征患者均有关节内骨折,关节积脂血征CT和MRI表现为关节囊内单液-液平面或双液-液平面,单液-液平面及双液-液平面的不同成份在CT和MRI上密度和信号不同,但上层均为脂肪。结论：关节积脂血征在CT和MRI上具有特征性表现,可做出明确诊断,关节积脂血征均与关节内骨折并存,可作为关节内骨折的可靠间接征象。     

Radiology of the resurfaced hip

Hip resurfacing arthroplasty is an increasingly common procedure for osteoarthritis. Conventional radiographs are used routinely for follow-up assessment, however they only provide limited information on the radiological outcome. Various complications have been reported in the scientific literature although not all are fully understood. In an effort to investigate problematic or failing hip resurfacings, various radiological methods have been utilized. These methods can be used to help make a diagnosis and guide management. This paper aims to review and illustrate the radiographic findings in the form of radiography, computerized tomography (CT), magnetic resonance imaging (MRI), and ultrasound of both normal and abnormal findings in hip resurfacing arthroplasty. However, imaging around a metal prosthesis with CT and MRI is particularly challenging and therefore the potential techniques used to overcome this are discussed.     

Magnetic resonance imaging of para-acetabular insufficiency fractures in patients with malignancy

AIM: To describe the characteristic magnetic resonance imaging (MRI) findings of para-acetabular insufficiency fractures in patients with malignancy, and compare the MRI appearance of these fractures with that of metastatic bone disease. MATERIALS AND METHODS: MRI examinations were reviewed in 16 patients with a known malignant tumour and severe hip pain that raised the possibility of local recurrence or metastatic disease. Six patients had received pelvic irradiation, and three patients were receiving steroid medication. RESULTS: The total number of fractures detected was 21: a solitary fracture was present in 11 patients and five patients had bilateral para-acetabular fractures. Two patients had associated sacral insufficiency fractures, and one of them had stress fractures involving both acetabular columns. Conventional radiography allowed the diagnosis of 14 (67%) fractures; six (28%) radiographic examinations were negative; and one (5%) examination was equivocal for fracture. Available scintigraphic and computed tomography (CT) studies revealed typical findings of fracture. Using MRI, insufficiency fractures appeared as linear regions of low signal intensity on T1- and T2-weighted images. Marked marrow oedema was evident in all cases. Fractures characteristically were parallel to the superior acetabulum in a curvilinear fashion in 18 (86%) instances, and were oblique in three (14%) instances. The fractures demonstrated considerable enhancement after intravenous gadolinium administration. No associated soft tissue masses were documented. CONCLUSION: Para-acetabular insufficiency fractures are a cause of hip pain, which may mimic skeletal metastasis in the patient with malignancy and pelvic irradiation. Recognition of the characteristic MRI findings of these fractures can preclude misdiagnosis and unnecessary bone biopsy.