title: Classification of osteonecrosis of the femoral head. Reliability, reproducibility, and prognostic value.
abstract: The purpose of the current investigation was to determine interobserver and intraobserver reliability of the classification system of Steinberg et al for osteonecrosis of the femoral head. Sixty-five anteroposterior and lateral radiographs of hips were selected randomly from a pool of patients with confirmed osteonecrosis of the femoral head. Six fellowship-trained observers viewed the radiographs (Reading 1). The observers used six main stages of the classification excluding A, B, and C subgroups. The same observers viewed the radiographs 4 months later in reverse order (Reading 2). Reading 1 was used to calculate interobserver kappa values. Reading 2 was used to calculate intraobserver kappa values. Stage-specific kappa values for interobserver variation between all viewers were as follows: Stage I, k = 0.64; Stage II, k = 0.51; Stage III, k = 0.21; Stage IV, k = 0.49; Stage V, k = 0.36; and Stage VI, k = 0.80. Stage-specific kappa values for intraobserver variation between all viewers were as follows: Stage I, k = 0.74; Stage II, k = 0.60; Stage III, k = 0.46; Stage IV, k = 0.59; Stage V, k = 0.27; and Stage VI, k = 0.78. An average of 10 of 21 (48%) of these errors involved Stage III. An average of 6.3 of 21 (30%) intraobserver errors involved Stage V. The presence of the crescent sign in Stage III and joint space narrowing in Stage V markedly diminished the overall reliability of any four- to six-stage classification system. Based on the authors' experience and analysis of the current classifications of osteonecrosis of the femoral head, an easy and reproducible Pittsburgh classification system is proposed.
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, PA 15213, USA.
authors.forename: A Y
authors.initials: AY
authors.lastname: Plakseychuk
authors.forename: M
authors.initials: M
authors.lastname: Shah
authors.forename: S E
authors.initials: SE
authors.lastname: Varitimidis
authors.forename: H E
authors.initials: HE
authors.lastname: Rubash
authors.forename: D
authors.initials: D
authors.lastname: Sotereanos
mesh_terms: D005260:Female; D005271:Femur Head Necrosis / Q000145:classification* / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D015588:Observer Variation; D011379:Prognosis; D011446:Prospective Studies; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index