Epiphyseal scar of the femoral head: risk factor of osteonecrosis

Evolutionary course of the femoral head osteonecrosis: Histopathological - radiologic characteristics and clinical staging systems

Osteonecrosis of the femoral head (ONFH) is a recalcitrant ischemic disorder, which could be classified into two major categories: traumatic and nontraumatic. Regardless of different risk factors, it has been testified that ONFH results from primitive vascular problems, leading to temporary or permanent loss of blood supply to bone tissue. Histopathological and microarchitectural alterations ensues, which is a gradual evolutionary process involving bone marrow and osteocyte necrosis, progressive destruction of subchondral bone, unsuccessful reparative process, and eventual articular collapse and degenerative arthritis. Based on the imaging features of ONFH, different classification systems have been developed to evaluate the severity and prognosis of the disease, which is pivotal for implementation of treatment strategy, especially the joint-preserving surgery. However, patients classified with the same severity stage, especially in the peri-collapse stage, sometimes responded differently after similar joint-preserving surgery. The unusual phenomenon may be attributed to the limitation of the current imaging classification systems, which might underestimate the disease severity, especially when referring to the early stages. In this review, we briefly summarize the etiology and pathogenesis of ONFH. The imaging features and staging classification systems of ONFH are also described. More importantly, we focus on histopathological and microstructural alterations of the femoral head, and provide an overview of their essential contribution to ONFH progression. Given the observation of discordance between imaging characteristics and histopathological alterations, a substantial amount of research on the relationship between imaging and histopathological features is required to further modify and revise the current wide-accepted classification systems.

Progression of knee osteonecrosis on MRI

Magnetic resonance imaging (MRI) is regarded as the most specific and sensitive of imaging modalities for the detection and progression of osteonecrosis (ON). We present MRI progression of ON in the knee in a 40-year-old female patient with Sjogren disease-related interstitial nephritis recently initiated on corticosteroids for deteriorating renal function. This case report correlates the degree of surrounding marrow edema with the patient's symptoms.

From the radiologic pathology archives imaging of osteonecrosis: radiologic-pathologic correlation

Osteonecrosis is common and represents loss of blood supply to a region of bone. Common sites affected include the femoral head, humeral head, knee, femoral/tibial metadiaphysis, scaphoid, lunate, and talus. Symptomatic femoral head osteonecrosis accounts for 10,000-20,000 new cases annually in the United States. In contradistinction, metadiaphyseal osteonecrosis is often occult and asymptomatic. There are numerous causes of osteonecrosis most commonly related to trauma, corticosteroids, and idiopathic. Imaging of osteonecrosis is frequently diagnostic with a serpentine rim of sclerosis on radiographs, photopenia in early disease at bone scintigraphy, and maintained yellow marrow at MR imaging with a serpentine rim of high signal intensity (double-line sign) on images obtained with long repetition time sequences. These radiologic features correspond to the underlying pathology of osseous response to wall off the osteonecrotic process and attempts at repair with vascularized granulation tissue at the reactive interface. The long-term clinical importance of epiphyseal osteonecrosis is almost exclusively based on the likelihood of overlying articular collapse. MR imaging is generally considered the most sensitive and specific imaging modality both for early diagnosis and identifying features that increase the possibility of this complication. Treatment subsequent to articular collapse and development of secondary osteoarthritis typically requires reconstructive surgery. Malignant transformation of osteonecrosis is rare and almost exclusively associated with metadiaphyseal lesions. Imaging features of this dire sequela include aggressive bone destruction about the lesion margin, cortical involvement, and an associated soft-tissue mass. Recognizing the appearance of osteonecrosis, which reflects the underlying pathology, improves radiologic assessment and is important to guide optimal patient management.

Is there an association between epiphyseal scar and osteonecrosis of the femoral head?

PURPOSE

To investigate statistical association between epiphyseal scar and osteonecrosis of the femoral head (ONFH) with magnetic resonance (MR) imaging.

PATIENTS AND METHODS

We retrospectively reviewed 71 consecutive patients who underwent MR imaging of bilateral hips that showed nontraumatic ONFH. There were 110 hips with ONFH and 31 normal hips; one hip received bipolar arthroplasty before the MR studies. All cases of ONFH had typical MR findings. The epiphyseal scars in the femoral head were classified as type I (a sealed-off scar) or type II (a perforated scar). Bone marrow edema, if present, in the proximal femur was identified on coronal T2-weighted or STIR MR images.

RESULTS

The type of femoral epiphyseal scar was clearly delineated in 97 hips. In cases with ONFH, a type I scar occurred in 46 hips (64%), and a type II scar in 26 hips (36%). In cases of ONFH with bone marrow edema, 69% of hips (24/35) had a type I scar and 31% of hips (11/35) had a type II scar. There was no statistical association between the type of epiphyseal scar and ONFH, regardless of staging (P=0.29), or the type of scar and bone marrow edema (P=0.42).

CONCLUSION

There is not a significant statistical association between a sealed-off scar and ONFH.

MR Imaging of the Hip: Osseous Lesions

Because of the exquisite soft tissue contrast resolution of MR imaging combined with recent technologic developments, a variety of conditions involving the hip joint and adjacent bony structures can be well evaluated using MR imaging, with or without contrast material. Among the different conditions, hip trauma and avascular necrosis are the most frequent indications. Other entities for which MR imaging has proven its usefulness include subchondral fractures, osteochondritis dissecans, transient osteoporosis, bone tumors, inflammatory and infectious processes, and a variety of bone marrow disorders.

Avascular necrosis and bone marrow edema syndrome

MR imaging is the most accurate modality for the diagnosis of AVN, bone marrow edema syndrome, and femoral head insufficiency fractures. When the particular demographics of the patient are considered, the specificity of this examination is high. The reported success rates of joint-sparing operative intervention are variable. When compared with conservative management, the outcome of joint-sparing operative intervention in patients who have early (stage I, II) AVN lesions is improved. This is impetus for screening programs for patients who are known to be at high risk for AVN, such as patients who have undergone renal transplants and others who are on long-term, high-dose corticosteroid treatment. There is strong evidence that bone marrow edema syndrome (TO) is a distinct entity with demonstrable unique histopathology and well-defined demographics. Increased spatial resolution revealed typical subchondral findings of AVN in lesions that were once believed to represent irreversible TO. SIF of the femoral head is a new concept with a seemingly distinct population and with clinical presentation and imaging characteristics that should permit its differentiation from AVN.

Treatment of transient bone marrow oedema of the hip--a comparative study

Between 1990 and 2000, we treated 43 patients with transient bone marrow oedema of the hip. Five were treated with nonsteroidal antiinflammatory drugs (NSAIDs) and limited weight bearing, and 38 by core decompression followed by limited weight bearing. At follow-up 2-10 years later, all patients were assessed by a structured interview as well as the Harris hip score (HHS) and the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC). Both groups reached the same clinical outcome (HHS and WOMAC). Core decompression enabled a significantly faster recovery. There were no complications, but progression to avascular necrosis was seen in both groups. Core decompression induced fast pain relief, making it the preferable treatment.

Avascular osteonecrosis in patients treated for Hodgkin's disease

The aim of this study is to assess the risk of avascular osteonecrosis (AVN) of the femoral head in patients treated for Hodgkin's disease (HD), in relation to the type of treatment they have received. For this purpose, a cohort of 1391 patients treated for HD at University of Rome between 1972 and 1996 was divided into 2 groups according to their initial treatment. The first group contained 784 patients treated, at the onset of HD, either with chemotherapy (CT) containing steroids, combined in some cases with subdiaphragmatic radiotherapy (RT), or with subdiaphragmatic RT combined with CT without steroids. The second group was made up of 607 patients who had received, initially, supradiaphragmatic RT alone or supradiaphragmatic RT combined with CT without steroids. For the purpose of this study, only the 784 patients belonging to the first group were observed for the appearance of AVN, which occurred in 9 cases. The period of time which elapsed between the end of treatment and the radiological evidence of AVN ranged from 23 to 97 months, with an average of 35 months. Because the number of cases of AVN was so small, the pathogenesis of this complication could not be identified.

Current concepts in imaging of the pelvis and hip

Over the past decade, imaging evaluation of orthopedic conditions of the pelvis and hips has become increasingly complex. Although the conventional radiograph remains the initial examination of choice, the decision between secondary tests, such as computed tomography, MR imaging, or scintigraphy is far from clear. A thorough understanding of current imaging technology is necessary for the clinician to choose the most appropriate examination for a given situation. This article reviews the current status of orthopedic imaging in the areas of acute trauma, stress injuries, osteonecrosis, arthropathies, tumors, and interventional imaging.