UTILITY OF MRI IN THE EARLY AND ACCURATE DIAGNOSIS OF AVASCULAR NECROSIS OF HIP JOINT

Abstract

Introduction: Avascular necrosis (also referred to as osteonecrosis, bone infarction, aseptic necrosis, ischemic bone necrosis, and AVN) is a disease where there is cellular death (necrosis) of bone components due to interruption of the blood supply. The term “avascular necrosis” is used to refer to these changes when they occur in epiphyseal region or subchondral bone¹. In clinical practice, AVN is most commonly encountered in the femoral head. It has also been called “the coronary disease of the hip” by Chandler as the disease simulates the ischemic condition in the heart.² 

Aims: 1) To evaluate Avascular Necrosis of Femoral Head by Plain radiograph and correlate by Magnetic Resonance Imaging (MRI). 2) To assess the importance of MRI in radiographically negative cases and those with high level of clinical suspicion. 3) To assess the importance of MRI in determination of clinically occult contralateral disease.

Materials and method: This prospective study was conducted in the Department of Radiodiagnosis at J.L.N. Hospital & Research Centre, Bhilai (C.G.). Sixty-one hips (40 patients) that underwent preliminary conventional radiography followed by MRI study of the hip were studied.

Result: A total of 40 patients (61 hip joints) were evaluated by Plain Radiographs and MRI. Of the 61 hips, plain radiographs could identify avascular necrosis in 44 hips (72%) and could not detect it in 17 hips (28%). In our study of 40 patients with AVN of femoral head, 40% of the patients (n=16) were suffering from sickle cell disease; 22.5% of the patients (n=9) had history of trauma/fracture of neck of femur; 20% (n=8) were on steroids for various reasons which included asthma, connective tissue disorders, skin disorders, immunological disorders, ITP and IgA nephropathy; 10% (n=4) suffered from infectious and inflammatory conditions. The other causes in our study were idiopathic (n=2) and chronic alcoholic (n=1).

Conclusion: The evaluation of an osteonecrosis lesion based only on plain radiographs could miss important information in stages II and III according to the Ficat and Arlet classification system. Magnetic Resonance Imaging (MRI) with its multi-planar capability and good tissue characterization property is very sensitive in early detection of radiographically negative as well as clinically unsuspected cases of avascular necrosis of femoral head.

Keywords: Avascular necrosis, Femoral head, Magnetic Resonance Imaging, Hip joint, Osteonecrosis, AVN, Computed Tomography, X rays, Joint effusion, Crescent sign.