Role of MRI in hip fractures, including stress fractures, occult fractures, avulsion fractures

MRI in suspected chest wall fractures: diagnostic value in work-related chest blunt trauma

OBJECTIVE

To describe and analyze MRI findings in suspected early fractures of the chest (ribs and sternum) and assess if this technique can add value in occupational medicine.

MATERIALS AND METHODS

In this retrospective study, we reviewed 112 consecutive patients with work-related mild closed chest trauma who underwent early thoracic MRI, when there was not a clear fracture on radiograph or when the symptoms were intense and not explained by radiographic findings. MRI was evaluated by two experienced radiologists independently. The number and location of fractures and extraosseous findings were recorded. A multivariate analysis was performed to correlate the fracture characteristics and time to RTW (return-to-work). Interobserver agreement and image quality were assessed.

RESULTS

100 patients (82 men, mean age 46 years, range 22-64 years) were included. MRI revealed thoracic wall injuries in 88%: rib and/or sternal fractures in 86% and muscle contusion in the remaining patients. Most patients had multiple ribs fractured, mostly at the chondrocostal junction (n=38). The interobserver agreement was excellent, with minor discrepancies in the total number of ribs fractured. The mean time to return-to-work was 41 days, with statistically significant correlation with the number of fractures. Time to return-to-work increased in displaced fractures, sternal fractures, extraosseous complications, and with age.

CONCLUSION

Early MRI after work-related chest trauma identifies the source of pain in most patients, mainly radiographically occult rib fractures. In some cases, MRI may also provide prognostic information about return-to-work.

Reporting of Full-Length Femur Imaging to Detect Incomplete Atypical Femur Fractures: 2023 Official Positions of the International Society for Clinical Densitometry

Incomplete atypical femur fractures (iAFFs) are associated with the long-term use of anti-resorptive therapies. Although X-rays are typically used to screen for iAFFs, images from dual-energy X-ray absorptiometry (DXA) offer an alternate method for detecting iAFFs. Although a previous 2019 ISCD Official Position on this subject exists, our task force aimed to update the literature review and to propose recommendations on reporting findings related to iAFFs that may be observed on DXA images. The task force recommended that full-length femur imaging (FFI) from DXA can be used as a screening tool for iAFFs. The presence of focal lateral cortical thickening and transverse lucencies should be reported, if identified on the FFI. This task force proposed a classification system to determine the likelihood of an iAFF, based on radiographic features seen on the FFI. Lastly, the task force recommended that the clinical assessment of prodromal symptoms (pain) is not required for the assessment of FFI.

Imaging of common hip pathologies in runners

Running is an increasingly popular sport and form of exercise. Because of the importance of the hip in the biomechanics involved with running, forming the primary connection between the axial and appendicular skeleton of the lower extremities, accurate diagnosis and reporting of hip pathology are vital for appropriate management. This review provides an overview of the most common hip pathologies and injuries encountered in runners. Radiologic studies, primarily conventional radiography and magnetic resonance imaging (MRI) provide useful diagnostic information and should be used in combination with clinical findings to help guide therapeutic management.

Imaging features of spinal fractures in ankylosing spondylitis and the diagnostic value of different imaging methods

Background

Our study aimed to characterize the imaging appearance of spinal fractures in ankylosing spondylitis (AS) and identify situations in which the use of magnetic resonance imaging (MRI) is necessary.

Methods

A total of 70 cases of spinal fractures associated with AS were retrospectively enrolled. Two radiologists independently reviewed the preoperative images. The location, type, ligament injury, neurological injury, and epidural hematoma following spinal fractures were assessed.

Results

Only one patient had a vertebral compression fracture, and 69 patients had 77 transverse fractures involving three columns. The most frequent injuries in AS patients were type B3 (N=32, 43.8%) spine fractures, followed by type C (N= 20, 27.4%) spine fractures. There were significant differences in fracture types of the different spine regions (H=14.1, P<0.0001). Most type C spine fractures were located in the lower cervical spine, while most of the type B2 spine fractures were located in the thoracic spine. Transverse fractures were classified as shear or stress type fractures. In total, there were 62 shear fractures and 15 stress fractures. All of the transverse fractures were detected by computed tomography (CT). The accuracy of CT in the diagnosis of the exact anatomic involvement of transverse fractures was significantly higher than that of MRI (χ²=8.36, P=0.014). The anterior longitudinal ligament (ALL) was the most frequently torn ligament. Tears of ossified ligaments were best visualized by sagittal reformatted CT. Lower cervical fractures were more likely to be associated with neurological injury compared with fractures to other regions of the spine (χ²=7.24, P=0.025). There were six epidural hematoma cases, which were only detected by MRI, were found to have fractures of the lower cervical spine.

Conclusions

We recommend a whole-spine CT examination with three-dimensional reconstruction for detecting a suspected fracture in AS patients. In cases with neurological injury, MRI examinations are always mandatory. AS patients with lower cervical spine fractures require further investigation by MRI. Patients with non-lower cervical spine fractures without any neurological deficits do not need to undergo an immediate MRI.

Detection and management of atypical femur fractures

PURPOSE OF REVIEW

This article summarizes the risk factors for atypical femur fractures (AFF), discusses current and emerging imaging modalities for early identification of AFF, and offers recommendations for prevention and management of AFFs based on the current concepts.

RECENT FINDINGS

Antiresorptive therapies are widely recommended for prevention and treatment of osteoporosis. Despite their well established effectiveness to reduce fracture risk, emerging concerns related to potential adverse effects have led to a substantial decline in the use of bisphosphonates. Although, the pathogenesis of AFF has not yet been elucidated, the bulk of evidence supports that the well known therapeutic benefits of bisphosphonate far outweigh the relatively low risk of AFFs. Recommendations for early identification of patients at risk for AFF using radiographic imaging have been established. Consensus on the management of AFF and osteoporosis in patients with AFF needs to be formulated.

SUMMARY

AFF is a rare event associated with long-term bisphosphonate therapy, which represents an apparent paradox in the management of osteoporosis. Improved understanding of pathogenetic mechanisms will be helpful in further refining of screening guidelines and standardization of management and treatment strategies.

Case of atypical femoral fractures that mimicked the typical imaging findings of prostate cancer-induced bone metastasis

INTRODUCTION

Atypical femoral fractures are atraumatic or minimally traumatic fractures and rare side effects of bone resorption inhibitors. Bone resorption inhibitors are frequently used in the treatment of prostate cancer.

CASE PRESENTATION

A 62-year-old man complained of difficulty in walking and left lower limb pain. Androgen deprivation and denosumab therapy for prostate cancer-induced bone metastasis was initiated 27 months ago. Even though the prostate-specific antigen level did not increase, imaging studies indicated the possibility of bone metastasis. The patient underwent bone biopsy; however, no malignancy was detected. Afterward, he had a fall, causing a complete fracture in his left femur.

CONCLUSION

Atypical femoral fractures occasionally mimic typical imaging findings and outcomes of bone metastasis. This case is important for recognizing such cases.

Imaging Features and Management of Stress, Atypical, and Pathologic Fractures

Traumatic and atraumatic fractures are entities with distinct but often overlapping clinical manifestations, imaging findings, and management protocols. This article is a review of terminology, etiology, and key imaging features that affect management of atraumatic fractures including stress fractures, atypical femoral fractures, and pathologic fractures. The terminology of atraumatic fractures is reviewed, with an emphasis on the distinctions and similarities of stress, atypical, and pathologic fractures. The basic biomechanics of normal bone is described, with an emphasis on the bone remodeling pathway. This framework is used to better convey the shared etiologies, key differences, and important imaging findings of these types of fractures. Next, the characteristic imaging findings of this diverse family of fractures is discussed. For each type of fracture, the most clinically relevant imaging features that guide management by the multidisciplinary treatment team, including orthopedic surgeons, are reviewed. In addition, imaging features are reviewed to help discriminate stress fractures from pathologic fractures in patients with challenging cases. Finally, imaging criteria to risk stratify an impending pathologic fracture at the site of an osseous neoplasm are discussed. Special attention is paid to fractures occurring in the proximal femur because the osseous macrostructure and mix of trabecular and cortical bone of the proximal femur can function as a convenient framework to understanding atraumatic fractures throughout the skeleton. Atraumatic fractures elsewhere in the body also are used to illustrate key imaging features and treatment concepts. ^©RSNA, 2018.

Atypical Femur Fractures: Review of Epidemiology, Relationship to Bisphosphonates, Prevention, and Clinical Management

Bisphosphonates (BPs) are highly effective in treating osteoporosis and reducing hip, vertebral, and other fractures by as much as 50% to 70%. However, since 2006, atypical femur fractures (AFFs) emerged as potential side effects of BPs and other treatments. These fractures have unusual radiologic features and occur with little trauma. Public concern has led to a >50% decrease in BP usage. AFFs are rare: for each AFF, >1200 fractures, including 135 hip fractures, are prevented. Case definition criteria were updated by the American Society of Bone and Mineral Research in 2014. Many epidemiologic studies have been reported, and although methodologically challenging, generally support a BP-AFF association. However, the magnitude of the association between BPs and AFFs is uncertain: estimates of relative risk for AFFs among BP users vs nonusers range from 1 to 65 with a meta-analysis estimate of 1.7. Although mechanistic studies have proposed several hypotheses explaining how BPs might decrease bone strength, AFF pathogenesis remains uncertain and cannot explain the paradox of efficacy of reduction of common fractures while increasing risk for rare fractures at one site. There are several consistent risk factors, including Asian race (in North America), femoral bowing, and glucocorticoid use, whereas others remain unclear. Consensus is emerging about strategies to prevent AFFs in BP users (including drug holidays after 5 years' use in some patients). In conclusion, AFFs can be devastating, but even under the most pessimistic assumptions, the benefit/risk ratio is highly positive for BPs, particularly during 3 to 5 years of use. As understanding of AFFs increases, it is becoming increasingly possible to maximize BP benefits while minimizing AFF risk.

Surgical Management of Atypical Femur Fractures Associated With Bisphosphonate Therapy

Atypical femur fractures associated with long-term bisphosphonate use can be challenging injuries to manage. Not only do they have a prolonged healing time and increased rate of nonunion as compared to typical femur fractures, intraoperative complications are not infrequent and can be catastrophic. Given the pathologic nature of these fractures, a multidisciplinary approach to the patient's care is necessary. Treatment begins with medical optimization and careful surgical planning. Radiographic characteristics of the fracture and femoral osteology dictate reduction strategy, adjunctive surgical techniques, and implant choice. Intraoperative complications including malreduction, iatrogenic fracture, and fracture propagation can be avoided with thoughtful planning. The purpose of this article is to discuss the technical aspects of surgical management of atypical femur fractures. We also discuss management of intraoperative complications and treatment failure. Finally, we provide an update on recommendations for postoperative medical treatment and management of the contralateral femur.

ACR Appropriateness Criteria® Stress (Fatigue/Insufficiency) Fracture, Including Sacrum, Excluding Other Vertebrae

Stress fractures, including both fatigue and insufficiency types, are frequently encountered in clinical practice as a source of pain in both athletes and patients with predisposing conditions. Radiography is the imaging modality of choice for baseline diagnosis. MRI has greatly improved our ability to diagnose radiographically occult stress fractures. Tc-99m bone scan and CT may also be useful as diagnostic tools. Although fatigue and insufficiency fractures can be self-limited and go onto healing even without diagnosis, there is usually value in initiating prompt therapeutic measures as incomplete stress fractures have the potential of progressing to completion and requiring more invasive treatment or delay in return to activity. This is particularly important in the setting of stress fractures of the femoral neck. Accuracy in the identification of these injuries is also relevant because the differential diagnosis includes entities that would otherwise be treated significantly different (ie, osteoid osteoma, osteomyelitis, and metastasis). The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

MRI of the hip: current concepts on bone marrow oedema

Bone marrow oedema (BME) is commonly found in hip MR imaging. BME is a nonspecific finding which can be related to a wide variety of diseases. However, there are cases where its existence or its pattern can narrow the differential or even point to a specific diagnosis. Therefore, deep understanding of its pathophysiology is of utmost importance for clinicians and radiologists in order to avoid diagnostic pitfalls. We hereby present currently established knowledge on BME related to adult hip pathology, aiming to raise physicians' suspicion and to highlight that it is mandatory to combine specific imaging patterns with the history, clinical and laboratory findings in order to achieve accurate diagnosis.

Hip Imaging in Athletes: Sports Imaging Series

Hip or groin pain in athletes is common and clinical presentation is often nonspecific. Imaging is a very important diagnostic step in the work-up of athletes with hip pain. This review article provides an overview on hip biomechanics and discusses strategies for hip imaging modalities such as radiography, ultrasonography, computed tomography, and magnetic resonance (MR) imaging (MR arthrography and traction MR arthrography). The authors explain current concepts of femoroacetabular impingement and the problem of high prevalence of cam- and pincer-type morphology in asymptomatic persons. With the main focus on MR imaging, the authors present abnormalities of the hip joint and the surrounding soft tissues that can occur in athletes: intraarticular and extraarticular hip impingement syndromes, labral and cartilage disease, microinstability of the hip, myotendinous injuries, and athletic pubalgia. (©) RSNA, 2016.

Acetabular roof stress fracture: a rare cause of hip pain in children

Stress fracture of acetabular roof is an unusual cause of hip pain. It is considered as an underdiagnosed entity. People who are more susceptible to experience this fracture are athletes, soldiers and dancers. We present the case of an 11 year old girl with a roof acetabular stress fracture for which the diagnosis and follow-ups were possible by the means of MRI. The treatment was keeping the child at a complete rest. Failure to abide with this treatment can cause the stress fracture to evaluate into a complete fracture.

The sensitivity of ct scans in diagnosing occult femoral neck fractures

Non-displaced hip fractures can be difficult to diagnose on plain film radiographs. When there is ongoing clinical suspicion of an occult fracture, further imaging is obtained. We investigated the sensitivity of computed tomography (CT) scans in detecting these fractures and the delays to surgery that three-dimensional imaging causes. We identified 78 CT scans performed for possible hip fractures over the past 3 years with the presence and absence of a fracture recorded. Based on subsequent imaging, the accuracy of CT scans was determined. CT scanning yielded sensitivity was 86% and specificity 98% for occult hip fracture (OHF). The median delay to definitive diagnosis was 37h. Our results demonstrate that CT scan does not bear sufficient sensitivity to detect all OHFs. We therefore recommend that MRI should be offered when a fracture is suspected. CT scans should be reserved for when MRI is not available, but a negative scan should be confirmed with subsequent MRI.

Taking a holistic approach to managing difficult stress fractures

Stress fractures and other bony stress injuries occur along a spectrum of severity which can impact treatment and prognosis. When treating these injuries, it should be borne in mind that no two stress fractures behave exactly alike. Given that they are not a consistent injury, standardized treatment protocols can be challenging to develop. Treatment should be individualized to the patient or athlete, the causative activity, the anatomical site, and the severity of the injury. A holistic approach to the treatment of the most difficult stress fractures should be taken by orthopedists and sports medicine specialists. This approach is necessary to obtain optimal outcomes, minimize loss of fitness and time away from sports participation, and decrease the risk of recurrence.

Manubrial stress fractures diagnosed on MRI: report of two cases and review of the literature

In contrast to widely-reported sternal insufficiency fractures, stress fractures of the sternum from overuse are extremely rare. Of the 5 cases of sternal stress fracture published in the English-language medical literature, 3 were in the sternal body and only 2 were in the manubrium. We describe two cases of manubrial stress fracture related to golf and weightlifting, and present the first report of the MR findings of this injury. In each of these cases, the onset of pain was atraumatic, insidious, and associated with increased frequency of athletic activity. Imaging was obtained because of clinical diagnostic uncertainty. On MRI, each patient had a sagittally oriented stress fracture of the lateral manubrium adjacent to the first rib synchondrosis. Both patients had resolution of pain after a period of rest, with subsequent successful return to their respective activities. One patient had a follow-up MRI, which showed resolution of the manubrial marrow edema and fracture line. Based on the sternal anatomy and MR findings, we hypothesize that this rare injury might be caused by repetitive torque of the muscle forces on the first costal cartilage and manubrium, and propose that MRI might be an effective means of diagnosing manubrial stress fracture.

Subradiographic Foot and Ankle Fractures and Bone Contusions Detected by MRI in Elite Ice Hockey Players

BACKGROUND

In ice hockey players, serious bone injuries in the foot and ankle, especially those attributed to impact from the moving puck, may be radiographically occult and underrecognized.

PURPOSE/HYPOTHESIS

The purpose of this research was to study foot and ankle bone injuries detected with magnetic resonance imaging (MRI) that occurred in elite hockey players. The hypothesis was that these injuries predominate medially, especially when caused by the impact from the puck, and are associated with prolonged lost playing time.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Three independent observers, blinded to the mechanism of injury, retrospectively reviewed foot and ankle MRI examinations acquired after 31 acute injuries that occurred in 27 elite ice hockey players who had no radiographically visible fractures. Bone abnormalities were classified as fractures or varying degrees of contusion based on predetermined definitions. Interobserver agreement was analyzed with kappa statistics. The association between the injury mechanism and the bones involved was examined with the Fisher exact test. A t test was applied to determine if MRI evidence of a severe bone injury (defined as either a fracture or a high-grade bone contusion) was associated with longer recovery times, when return-to-play information was available.

RESULTS

The observers identified at least 1 bone injury in 27 of the 31 MRI examinations, including 10 with radiographically occult fractures. Agreement among the 3 observers for injury categorization was substantial (κ = 0.76). Seventeen injuries were caused by a direct blow (15 from a moving puck, 2 from an uncertain source), resulting in 6 fractures and 6 high-grade bone contusions, with 14 of the 17 involving a medial bone (medial malleolus, navicular, or first metatarsal base). Compared with other mechanisms, direct impaction was statistically more likely to result in a severe bone injury and to involve the medial foot and ankle. In 20 injuries where return-to-play information was available, players with severe bone injuries missed a mean of 10.6 games compared with 2.4 games for other players (P = .05).

CONCLUSION

MRI can show severe bone injuries that are not visible radiographically in ice hockey players. Most fractures and high-grade contusions involve the medial ankle and midfoot bones, can be caused by direct blows from the puck, and are associated with prolonged recovery times.

Atypical femur fractures in patients receiving bisphosphonate therapy: etiology and management

Osteoporosis is a growing problem that is projected to affect more than 50% of American adults by 2020. Bisphosphonate therapy is currently the primary mode of treating osteoporosis in this population. While bisphosphonate therapy has been successful in increasing bone mineral density, data has shown an increased risk of atypical femur fractures with prolonged therapy. Atypical femur fractures are characterized by low-energy or atraumatic injuries that occur in the subtrochanteric region. They originate on the medial cortex, travel transversely, and typically have little or no comminution. Conservative therapy is indicated for patients with incomplete fractures without prodromal symptoms. Patients with incomplete fractures and significant prodromal symptoms or visible fracture line on radiographs, those who have failed conservative management, and those with complete fractures should be treated with intramedullary nail fixation. Evaluation should involve imaging of the contralateral femur. Teriparatide therapy may be considered for patients without contraindications. While the incidence of these fractures is low, it is likely that these rates will increase with the aging population and increased prevalence of patients being treated with bisphosphonate therapy.

Occult fractures of the proximal femur: imaging diagnosis and management of 82 cases in a regional trauma center

BACKGROUND

Occult hip fractures are often difficult to identify in busy trauma units. We aimed to present our institutions experience in the diagnosis and treatment of occult fractures around the hip and to help define a clinical and radiological management algorithm.

METHOD

We conducted a seven-year retrospective hospital medical record analysis. The electronic database was searched for ICD-10 CM codes S72.0 and S72.1 used for proximal femoral fractures upon patient discharge. We identified 34 (4.83 %) femoral neck fractures and 48 (4.42 %) trochanteric fractures labeled as occult.

RESULTS

The majority of the cases were diagnosed by primary MRI scan (57.4 %) and 12 were diagnosed by emergency CT scan (14.6 %). For the remaining cases the final diagnosis was confirmed by 72 h CT scan in 9 patients (representing 39 % of the false negative cases) or by MRI in the rest of 14 patients. MRI was best at detecting incomplete pertrochanteric fracture patterns (13.45 % of total) and incomplete fractures of the greater trochanter (3.65 % of total) respectively. It also detected the majority of Garden I femoral neck fractures (20.7 % of total). CT scanning accurately detected 100 % of Garden 2 fractures (2.44 %) and 25 % (3.65 %) of the complete pertrochanteric fractures (false negative 25 %).

CONCLUSION

Occult fractures should be suspected in all patients with traumatic onset of hip pain that is inconsistent with normal radiographic findings. MRI is the golden standard but not as readily available not as cheap and not quite as quick to perform as as a CT scan. The latter which in turn can provide falsely negative results in the first 24 h. Improved imaging protocols could expedite management and improve treatment.

Stress fracture of the pelvis and lower limbs including atypical femoral fractures-a review

Stress fractures, that is fatigue and insufficiency fractures, of the pelvis and lower limb come in many guises. Most doctors are familiar with typical sacral, tibial or metatarsal stress fractures. However, even common and typical presentations can pose diagnostic difficulties especially early after the onset of clinical symptoms. This article reviews the aetiology and pathophysiology of stress fractures and their reflection in the imaging appearances. The role of varying imaging modalities is laid out and typical findings are demonstrated. Emphasis is given to sometimes less well-appreciated fractures, which might be missed and can have devastating consequences for longer term patient outcomes. In particular, atypical femoral shaft fractures and their relationship to bisphosphonates are discussed. Migrating bone marrow oedema syndrome, transient osteoporosis and spontaneous osteonecrosis are reviewed as manifestations of stress fractures. Radiotherapy-related stress fractures are examined in more detail. An overview of typical sites of stress fractures in the pelvis and lower limbs and their particular clinical relevance concludes this review.

Teaching Points

• Stress fractures indicate bone fatigue or insufficiency or a combination of these.

• Radiographic visibility of stress fractures is delayed by 2 to 3 weeks.

• MRI is the most sensitive and specific modality for stress fractures.

• Stress fractures are often multiple; the underlying cause should be evaluated.

• Infratrochanteric lateral femoral fractures suggest an atypical femoral fracture (AFF); endocrinologist referral is advisable.

What's new in the use of MRI in the orthopaedic trauma patient?

MRI has been established as an essential tool for accurate diagnosis in patients with musculoskeletal trauma. Its major advantages include excellent soft tissue contrast, high spatial resolution and lack of ionizing radiation. Although plain radiographs remain the basic tool for diagnosis and treatment planning in bone fractures assisted by CT in pelvic, spine and large joints injuries, there are specific circumstances that require MRI. For instance, tendinous, ligamentous, intraarticular structures such as the cartilage and menisci, and intramedullary injury are seen mostly with MRI. Volumetric 3D techniques are now commercially available and provide higher spatial resolution which improves anatomic detail, allows multiplanar reformations and reduces the acquisition time. Newer applications on quantitative rather than morphologic imaging, such as relaxometry and diffusion tensor imaging, may be of paramount importance in treatment planning in the near future. Software improvements reduce metal induced artefacts, allowing thus imaging of the postoperative patient with metallic implants. A tendency towards a structured reporting pattern and standardised medical communication needs to be further explored for the benefit of orthopaedic surgeons, radiologists and patients.

Bilateral Pseudarthrosis of the Femoral Neck in a 25-Year-Old Male with Hereditary Hypophosphatemic Rickets

Hereditary hypophosphatemic rickets (HHR) is a rare disorder of renal phosphate wasting and the most common form of heritable rickets. Here, we report a case of an active 25-year-old male with HHR showing atraumatic bilateral femoral neck pseudarthrosis after 4 years of consecutive knee pain. A conservative therapy was administered, taking into account both the risks of surgical treatment and the little impairment even in the sport activities which the patient experienced.