The pitfalls of planar three-phase bone scintigraphy in nontraumatic hip avascular osteonecrosis

Purpose: This study documented the previously reported lower sensitivity of routine planar three-phase bone scintigraphy (BS) performed using a high-r esolution parallel-hole collimator compared with MRI to diagnose nontraumat ic avascular necrosis of the hip (AVN). Methods: Six observers reviewed 143 bone scintigrams obtained in patients w ith nontraumatic hip pain (n = 120) or a control group (n = 23). All patien ts had a standard radiograph and MRI within 2 months of the BS. Of 280 hips , 148 (53%) were painful on the day of the examination. The osteonecrosis g roup (AVN) consisted of 93 instances of AVN in 58 patients. Although it dep arts from the clinical situation, this method evaluated the intrinsic perfo rmance of the imaging method. The data were analyzed using a receiver opera ting characteristic method. Results: For the six observers, the A(z) values were 0.65, 0.67, 0.66, 0.67 , 0.73, and 0.79, respectively, and 0.66, 0.71, 0.75, 0.81, 0.81, 0.82, and 0.84 after removing hip diseases other than AVN through data manipulation. Bone marrow edema, as seen on MRI, was the most frequently reported mislea ding sign in false-positive diagnoses, especially in the early or late phas es of the disease. False-negative diagnoses misclassified the scans as "asy mptomatic hips" in 28 of 30 cases. Twenty-two of 30 scans appeared normal, but these AVN lesions were small (<25%) and were discovered by chance on MR Is that displayed bilateral involvement associated with radiographic eviden ce (stage 0 or 1). Thirteen of 20 patients were followed for 3 or more year s, and only one worsened. Conclusions: BS is not indicated to diagnose possible contralateral AVN if the hip is asymptomatic. This study emphasizes the results from the literat ure; if indicated, a radionuclide hip investigation requires the use of a p inhole collimator, a SPECT study with scatter correction and iterative reco nstruction algorithms, or both.