Immature bone infarcts: findings on plain radiographs and MR scans

Sclerotic bone lesions caused by non-infectious and non-neoplastic diseases: a review of the imaging and clinicopathologic findings

Bone sclerosis is a focal, multifocal, or diffuse increase in the density of the bone matrix on radiographs or computed tomography (CT) imaging. This radiological finding can be caused by a broad spectrum of diseases, such as congenital and developmental disorders, depositional disorders, and metabolic diseases. The differential diagnosis can be effectively narrowed by an astute radiologist in the light of the clinical picture and typical findings on imaging. Some of these lesions are rare and have been described as case reports and series in the literature. This article aims to collate the clinical-radiologic findings of non-infectious and non-neoplastic causes of bone sclerosis with relevant imaging illustrations.

The "birth of death": MRI step-by-step reveals the early appearance of a bone marrow infarct

The magnetic resonance imaging (MRI) appearance of an “established” bone marrow infarct is well-known, consisting of an area of preserved bone marrow signal surrounded by a serpiginous line. We report the uncommon observation of the very early phases of appearance of a bone marrow infarct, showing its progressive de novo appearance on MR images paralleling clinical symptoms and high-dose systemic steroid administration in a young female patient, presenting with acute knee pain. The initial knee MR examination performed one week after pain onset showed no abnormality. One week later, a second examination showed subtle ill-defined dotted signal abnormalities of the bone marrow of uncertain significance, of high signal on PDFS sequences. A third MR study obtained again one week later showed more evident findings with confluence of the high signal “dots” into a serpiginous line with a geographical appearance of the lesion, corresponding to the typical MRI presentation of bone marrow infarcts. Follow-up MRI at seven weeks showed definitive stability of this bone marrow infarct. A whole-body MRI performed for whole skeleton screening revealed multiple bone marrow infarcts typical for systemic avascular necrosis. This case represents a novel observation of the “birth” of a bone marrow infarct, from early intriguing changes to its typical ring-shaped appearance on MR images. It also reminds of the key role of MRI for early diagnosis of bone marrow infarcts and illustrates the emerging role of whole-body MRI for the detection of multifocal, asymptomatic skeletal involvement by ischemic lesions in systemic osteonecrosis.

Orthopaedic Manifestations of Sickle Cell Disease

Sickle cell disease (SCD) is an autosomal recessive disorder that results in hemolytic anemia related to abnormal hemoglobin and erythrocyte levels. SCD is characterized by vascular occlusive episodes, visceral sequestration, and aplastic or hemolytic crises. These crises most commonly occur in bone. The orthopaedic manifestations of SCD comprise much of the morbidity associated with this disorder. Osteonecrosis and osteomyelitis are among the most disabling and serious musculoskeletal complications in patients with SCD. Effective management of the bone and joint sequelae requires an accurate diagnosis, an understanding of the pathophysiology of the disease, and knowledge of available medical and surgical treatment alternatives. The major orthopaedic manifestations of SCD are osteonecrosis, osteomyelitis, septic arthritis, and bone infarction. Patients with SCD require close monitoring in the perioperative period because of the risk for vasoocclusive crisis.

Mr Imaging of Pediatric Hematologic Disorders

The present report illustrates the efficiency of MR imaging in evaluating children with hematologic disorders.

Acute bone infarction: a rare complication in thalassemia

Acute bone infarction is a well-described complication in sickle cell hemoglobinopathy but it is rarely reported in patients with thalassemia. This report describes an 18-year-old man with homozygous β-thalassemia presenting with a fever and severe acute bilateral ankle pain. The acute onset of severe pain and fever were clinical mimics of infectious arthritis and osteomyelitis. Magnetic resonance imaging revealed acute bone infarction in the meta-diaphysis of bilateral tibias presenting as central unenhanced devitalized bone with T1-high signal intensity fluid in the subperiosteum and soft tissue. Characteristic imaging features are discussed, emphasizing the benefit of fat suppression pre-and post-intravenous gadolinium T1-weighted images. The etiologies of bone infarction in thalassemia are reviewed.

Bone infarcts: Unsuspected gray areas?

There is agreement to label as bone infarcts avascular necrosis (AVN) occurring in the metaphyses or diaphyses of long bones, the terms AVN or osteonecrosis being used at the epiphyses. One might expect bone infarction to hold no mysteries. Oddly enough, however, scientific evidence about bone infarcts is extraordinarily scant. The prevalence of bone infarcts is unknown. The main sites of involvement are the distal femur, proximal tibia, and distal tibia. In patients without sickle cell disease or Gaucher's disease, involvement of the upper limbs and lesions confined to the diaphysis are so rare as to warrant a reappraisal of the diagnosis. Although widely viewed as a generally silent event, bone infarcts causes symptoms in half the cases. Standard radiographs are normal initially then show typical high-density lesions in the center of the marrow cavity. A periosteal reaction is common and may be the first and only radiographic change. Magnetic resonance imaging consistently shows typical features and therefore, in principle, obviates the need for other investigations. Bone infarcts are multifocal in over half the cases and, when multifocal, are usually accompanied with multiple foci of epiphyseal avascular necrosis. Thus, bone infarcts, whose prognosis is good per se (with the exception of the very low risk of malignant transformation), are usually a marker for systemic avascular necrosis. Consequently, patients with bone infarcts must be investigated both for known risk factors and for other foci of avascular necrosis, which may, in contrast, have function-threatening effects.

Infarct-Associated Bone Sarcomas: Multimodality Imaging Findings

OBJECTIVE

The objective of our study was to characterize infarct-associated bone sarcoma and its imaging features.

MATERIALS AND METHODS

Our databases were searched for instances of sarcoma arising in association with osteonecrosis. Demographic and imaging data were recorded. The imaging studies of 258 patients with sarcomas were reviewed to determine whether underlying osteonecrosis was present. Radiographic and MRI studies of patients with bone infarction were reviewed to categorize the various appearances of infarction and to determine if sarcomas tended to arise in a particular pattern. A literature review was performed.

RESULTS

Nine infarct-associated bone sarcomas were found in eight patients: seven malignant fibrous histiocytomas (MFHs) and two osteosarcomas. All occurred in the femur or tibia; multifocal infarction was documented in all patients except one. Sarcomas were commonly associated with a so-called "mature"-type pattern of osteonecrosis-that is, with well-defined calcified margins. Osteolysis of infarct-associated MFHs was often overlooked at initial presentation and was often detected only after pathologic fracture. CT and MRI revealed cortical penetration in all cases; infarct margin disruption was evident, but preservation of fat within the infarct was typical. Increased radiotracer activity with relative central photopenia was characteristic of large infarct-associated bone sarcomas on scintigraphy. All lesions, including those treated at our institution and those found in the literature, were metaphyseal or diaphyseal, and although epiphyseal extension of sarcoma from a metadiaphyseal infarct was common, no purely epiphyseal lesions were encountered.

CONCLUSION

Radiologists must remain vigilant for this rare occurrence, especially in patients with new pain in an area of known bone infarction.

Suspected intramedullary bone infarct subsequent to tibial plateau levelling osteotomy in a dog

BACKGROUND

Bone infarction is a syndrome associated with disruption to the medullary blood supply of a long bone and may present as either a cause of lameness or, more commonly, an incidental finding. Bone infarction is a known complication of total hip replacement in the dog and may be associated with several other systemic diseases.

CASE REPORT

A 3-year-old female desexed Labrador Retriever presented for acute lameness 4 weeks following tibial plateau levelling osteotomy (TPLO). Subsequent radiographs revealed an increase in medullary bone opacity, radiographically consistent with a medullary bone infarction. The lesion was followed with serial radiographs and appeared to spontaneously resolve.

CONCLUSION

This is the first reported case of bone infarction following TPLO in the dog. Bone infarction should be considered as an unlikely but potential complication of TPLO.

Deferoxamine-induced dysplasia-like skeletal abnormalities at radiography and MRI

BACKGROUND

Current thalassemia major treatment includes blood transfusion and iron chelation, which is associated with growth disturbances and radiographic changes in the long bone metaphyses.

OBJECTIVE

To explore and discuss the spectrum of deferoxamine-induced bone-dysplasia-like changes in children with thalassemia major in Egypt.

MATERIALS AND METHODS

We studied 59 Egyptian children with thalassemia major and generalized arthralgia. All started deferoxamine treatment at 3 years of age. We conducted skeletal survey and MRI of both knees in radiographically positive children. Each child's age, serum ferritin, age of onset and duration of therapy were compared with the radiologic findings.

RESULTS

Twenty-two (37.3%) children had variable degrees of skeletal dysplasia-like changes similar to those described with deferoxamine intake, mostly around the knees. Mild dysplasia-like changes were seen in 4 (18%) children; moderate changes were seen in 11 (50%) children and severe changes were seen in 7 (31.8%) children. No statistically significant relationships were detected between bone changes and the children's age, age of starting deferoxamine, duration of therapy, or serum ferritin level.

CONCLUSION

A wider spectrum of deferoxamine-induced bone-dysplasia-like changes was recognized despite delayed onset and small doses of therapy. These changes should be considered as a possible cause of arthropathy in children with thalassemia major, especially symptomatic children.

Osteonecrosis of the distal tibia metaphysis after a Salter-Harris I injury: a case report

Posttraumatic osteonecrosis has been well described as a common phenomenon seen in fractures of the femoral neck, talus, and scaphoid. In the following case, we describe posttraumatic osteonecrosis in a rare location: the distal tibia. Our report details a child who sustained a distal tibia physeal injury and subsequently developed radiographic findings consistent with aseptic necrosis. Besides a traumatic incident, the patient did not have any of the risk factors known to cause osteonecrosis. Awareness of this complication after Salter-Harris I fractures will help reduce time to diagnosis and optimize treatment.

Imaging diagnosis--Medullary tibial infarction in a horse

An Andalusian Stallion with left hind limb lameness had a radiolucent lesion in the medullary cavity of distal tibial metaphysis. After euthanasia for other disease, the tibia was examined with magnetic resonance (MR). The MR imaging sequences were characterized by a double line sign, although showing quite different lesion area intensities. Histologically, the lesion was compatible with medullary infarction being characterized by normal spongy bone, areas of abundant fibrous tissue and numerous necrotic adipocytes in various stages of destruction.

Simultaneous osteonecrosis and osteomyelitis in a patient with cancer of the breast

Breast cancer is generally managed surgically with adjuvant agents which include hormone therapy, chemotherapy, radiotherapy and bisphosphonate therapy. However, some of these adjuvant therapies may cause adverse events, including wound infection, neutropenia, bone marrow suppression and fever. The simultaneous presentation of osteonecrosis and osteomyelitis has not previously been described in patients with breast cancer undergoing hormone therapy and chemotherapy. We report a patient with breast cancer who developed bone infarcts in both legs as well as osteomyelitis in the right distal tibia after treatment which included a modified radical mastectomy, hormone therapy and chemotherapy. Simultaneous osteonecrosis and osteomyelitis should be considered in patients with breast cancer who are receiving chemotherapy and hormone therapy who present with severe bone pain, especially if there have been infective episodes during treatment.

Magnetic resonance imaging of medullary bone infarction in the early stage

Medullary bone infarctions, which are believed to arise due to arterial obstructions in the bone, are usually asymptomatic and are noted incidentally in roentgenograms or bone scans performed for other reasons. We present two cases of acute bone infarctions that were found accidentally by magnetic resonance imaging (MRI). In both cases, conventional radiographs could not demonstrate any findings and the cases were clinically asymptomatic. The current two cases suggest that MRI shows various findings in bone infarctions.

Pitfalls in MR Image Interpretation Prompting Referrals to an Orthopedic Oncology Clinic

Patients referred to the authors' hospital for evaluation on suspicion of a bone or soft-tissue malignancy frequently present to the Orthopaedic Oncology Clinic with magnetic resonance (MR) images that show typical features of nonmalignant or nonneoplastic entities. The purpose of this article is to review the benign entities that may be mistaken by the radiologist for a malignancy and thus lead to needless referral to an orthopedic oncologist. Normal hematopoietic marrow and marrow edema due to a stress reaction may mimic a neoplasm at MR imaging, but knowledge of the typical patterns and locations of these features allows an accurate radiologic interpretation. The MR imaging appearance of osteonecrosis, Paget disease, benign bone lesions, and rheumatologic conditions may be confusing; in such circumstances, radiographic findings may help formulate a correct diagnosis. Knowledge of the common locations and appearances of bursae and ganglia is necessary so that radiologists do not misinterpret these benign entities as soft-tissue sarcomas. Soft-tissue trauma and inflammation also may mimic tumors at MR imaging, but a familiarity with the imaging patterns of nonneoplastic change in muscle allows the avoidance of misinterpretation. The clinical history, as always, is an important component of proper diagnosis. The radiologist can be especially useful to both the clinician and the patient by recognizing entities that are highly unlikely to represent malignancy and by confidently reporting those entities as benign, thereby sparing the patient an unnecessary trip to the orthopedic oncologist.

MR imaging of therapy-induced changes of bone marrow

MR imaging of bone marrow infiltration by hematologic malignancies provides non-invasive assays of bone marrow cellularity and vascularity to supplement the information provided by bone marrow biopsies. This article will review the MR imaging findings of bone marrow infiltration by hematologic malignancies with special focus on treatment effects. MR imaging findings of the bone marrow after radiation therapy and chemotherapy will be described. In addition, changes in bone marrow microcirculation and metabolism after anti-angiogenesis treatment will be reviewed. Finally, new specific imaging techniques for the depiction of regulatory events that control blood vessel growth and cell proliferation will be discussed. Future developments are directed to yield comprehensive information about bone marrow structure, function and microenvironment.

Osteonecrosis of the patella: diagnostic imaging perspective

Disability from knee dysfunction has important implications on a patient's performance of simple day-to-day tasks, work-related duties, and leisure activities, including sports. Diagnostic imaging is of fundamental importance in the clinical evaluation of the patient with knee pain. The use of magnetic resonance imaging (MRI) for the assessment of knee pain and dysfunction has increased over the past few years as orthopedic surgeons and radiologists have familiarized themselves with the unique advantages of this modality. Magnetic resonance imaging provides a comprehensive evaluation of a wide spectrum of intra-articular and extra-articular pathologic conditions involving the knee. One of the most common indications for MRI of the knee is osteonecrosis. Osteonecrosis of the patella is unusual, and it is a well-documented cause of knee pain. After a brief overview of the anatomy of the patella, the diagnosis of osteonecrosis at this site by conventional radiography, MRI, and other imaging methods is focused on in this review.

MRI of osteonecrosis

Osteonecrosis is a relatively common condition, which may be idiopathic or secondary to a variety of clinical situations. It may involve the subarticular region of a joint, when it is commonly referred to as ischaemic necrosis, or the metaphyseal regions of long bones, when it is referred to as bone infarction. In both situations, early lesions may be radiographically occult. However, magnetic resonance imaging (MRI) is very sensitive in identifying and characterizing osteonecrosis. This review illustrates the varied MRI features of osteonecrosis that enable a confident diagnosis to be made. Complications and differential diagnosis are also considered.

MR imaging of the diabetic foot

Diabetes is a common disease with potentially devastating complications affecting the foot and ankle. Ischemia and infarction, neuropathic osteoarthropathy, callus, ulceration, and infection result from the underlying neurologic and vascular disease. The MR imaging appearance of these complications is discussed. Recognition of these MR imaging patterns is important for formulation of an appropriate treatment plan.

Work-up of the diabetic foot

Diabetes is a common disease with potentially devastating complications affecting the foot and ankle. A combination of vascular disease, peripheral neuropathy, and immunopathy results in a cascade of conditions including ischemia and infarction, tendinopathy, atrophy, edema, deformity, neuropathic osteoarthropathy, callus, ulceration, and infection. MRI is useful for evaluation of these complications, and assists the clinician in medical or surgical planning.

Deferoxamine-induced bone dysplasia in the distal femur and patella of pediatric patients and young adults: MR imaging appearance

OBJECTIVE

We investigated the MR imaging appearance of deferoxamine-induced bone dysplasia in the distal femur and patella in patients with thalassemia major.

MATERIALS AND METHODS

Thirty-five patients with homozygous ss-thalassemia major who were undergoing regular transfusions and chelation therapy underwent coronal T1-weighted MR imaging of the femur, including the femoral head and the distal femoral epiphysis. Additional coronal fat-saturated dual-echo and sagittal T1-weighted images of the distal femur and patella were obtained in 11 patients who were suspected of having distal femoral lesions on the basis of the coronal T1-weighted images of the entire femur.

RESULTS

No dysplastic change was detected in the proximal femur on coronal T1-weighted images. In 22 distal femurs of 11 patients, the following abnormalities were detected on MR imaging: blurred physeal-metaphyseal junction (n = 22), distal metaphyseal areas of hyperintensity (n = 21), physeal widening (n = 18), metadiaphyseal lesions (n = 11), epiphyseal lesions (n = 10), and patellar lesions (n = 2). Physeal widening and distal metaphyseal hyperintense areas were all more pronounced peripherally. Of the 21 distal metaphyseal hyperintensities, lateral abnormalities were larger than medial abnormalities in 16. Of the 18 distal femurs in which physeal widening was detected, the lateral widening was more marked than the medial widening in 12. Patients with MR imaging evidence of bone dysplasia have a significantly (p = 0.003) greater height reduction than patients without such evidence of bone dysplasia.

CONCLUSION

Deferoxamine-induced bone dysplasia in the distal femur and patella is represented by a spectrum of morphologic changes in the epiphysis, physis, metaphysis, and metadiaphysis on MR imaging.

Femoral medullary infarction secondary to canine total hip arthroplasty

OBJECTIVE

To evaluate the prevalence of femoral intramedullary infarction after total hip arthroplasty (THA) and to determine whether any specific femoral morphology predisposes to bone infarction.

STUDY DESIGN

Retrospective clinical study.

SAMPLE POPULATION

All dogs from our hospital population undergoing THA between 1984 and 1997 with radiographic follow-up available at 1 year or more postoperatively.

METHODS

A case control study was conducted within the THA group to determine risk factors predisposing to femoral infarction after THA. Medical records and radiographs were reviewed. Data were collected on clinical parameters, femoral morphology, prosthesis, and bone changes. Radiographic diagnosis was confirmed using histopathology in 11 femora. Radiographs of 50 age-matched control dogs weighing more than 20 kg with coxofemoral degenerative joint disease were randomly chosen to determine the prevalence of bone infarction in nonoperated dogs.

RESULTS

Ninety-one dogs with 110 THA were included in the study. Fifteen of the 110 femora with THA had radiographic evidence of infarction (14%). Infarction was not present in any femora in the control group. There was no significant difference in the prevalence of infarction between dogs that received cemented or uncemented prostheses. Clinical signs were not reported in any patient that developed femoral infarction. Young age (P = .03) and a distance between the greater trochanter and nutrient foramen greater than 79 mm (P = .008) predisposed dogs to femoral infarction. Over time, three infarcts decreased in size radiographically, five remained unchanged, and three expanded. An osteosarcoma developed at the site of a bone infarct in one dog.

CONCLUSION

Femoral intramedullary infarction occurred in 15 of 110 THA. Young age at the time of THA and a greater distance between the greater trochanter and the nutrient foramen predisposed to infarction.

CLINICAL RELEVANCE

Intramedullary infarction occurs after canine THA. These bone infarcts do not appear to cause clinical signs; however, they may present a diagnostic challenge. Malignant transformation could potentially result from medullary infarction.

The diagnostic role of gadolinium enhanced MRI in distinguishing between acute medullary bone infarct and osteomyelitis

The objective of the study was to evaluate the diagnostic utility of contrast enhanced magnetic resonance imaging (MRI) for distinguishing between acute medullary bone infarct and osteomyelitis. There were 11 patients (age 6-34 years) presented to our institution between December 1994 and February 1998 with a clinical differential diagnosis of acute bone infarct versus osteomyelitis and inconclusive radiographs were imaged using MRI. All but one received i.v. gadolinium. Nine of the patients had homozygous Sickle Cell disease (SCD) and two had Systemic Lupus Erythematosus (SLE), the latter requiring chronic methylprednisolone. Osteomyelitis was confirmed either by biopsy alone or by the combination of Gallium(67) scan in conjunction with positive blood cultures and clinical resolution following antibiotics. Infarcts without osteomyelitis were confirmed either by biopsy or resolution of symptoms without antibiotic therapy. All patients had at least six months clinical follow-up. The results found that seven of nine patients with SCD had acute infarct only. One patient with SCD had osteomyelitis only. Three patients (two SLE and one SCD) had both acute-on-chronic infarcts and superimposed osteomyelitis, one with an adjacent soft tissue abscess. Accurate distinction between infarct and osteomyelitis was impossible for one patient with SLE who did not receive contrast. All other cases were correctly diagnosed prospectively based on distinct patterns of MRI contrast enhancement. In all adult patients, acute infarcts demonstrated thin, linear rim enhancement on MRI while osteomyelitis revealed more geographic and irregular marrow enhancement. Two of four cases of osteomyelitis also demonstrated subtle cortical defects with abnormal signal traversing marrow and soft tissue. The single pediatric patient demonstrated elongated, serpiginous central medullary enhancement with periostitis. We concluded that the pattern of MR contrast enhancement may allow accurate distinction between acute infarct and osteomyelitis, or recognition of osteomyelitis superimposed on bone infarction.

Enostosis-like lesions in the long bones of 10 horses: scintigraphic and radiographic features

Ten horses admitted for lameness evaluation including bone scintigraphy had enostosis-like lesions, described scintigraphically as focal or multifocal areas of intense increased radioisotope uptake within the medullary cavity of one or more long bones, and radiographically as one or multiple round to irregularly shaped radiopacities within the medullary cavity, often in close proximity to the nutrient foramen. There were 6 Thoroughbreds, one male, one female and 4 geldings, 3 Standardbreds, all geldings and one Appaloosa gelding; age 3-10 years. Enostosis-like lesions were seen in the tibia (5 horses), radius (3 horses), humerus (one horse) and third metatarsal bone (MT-III) (4 horses). The number of affected bones in each horse was 1-3. Of 16 affected limbs, there were 9 hindlimbs and 7 forelimbs. Enostosis-like lesions were considered a possible cause of lameness in 5 horses, but were considered incidental findings in the other horses. Lesions thought to cause lameness were seen in the tibia (2 horses), MT-III (one horse) and in the radius (4 horses). Lameness resolved after horses were rested (2-6 months) and given nonsteroidal anti-inflammatory drugs (4 horses). Follow-up scintigraphic examination in 3 horses (2, 6 and 9 months later, respectively) revealed normal radioisotope uptake in the affected areas.

Femoral infarction following intraarterial chemotherapy for osteosarcoma of the leg: a possible pitfall in magnetic resonance imaging

Bone infarction of the distal femur is reported in two patients with osteosarcoma of the leg (1 tibia, 1 fibula) treated by preoperative chemotherapy including intraarterial chemotherapy (IAC) by Cis-platinum. Both patients were examined by magnetic resonance imaging before chemotherapy and again prior to limb salvage surgery. The location of these lesions in the distal femur must suggest bone infarction especially if the tumor has decreased in size under treatment.