ORIGINAL PAPER Reliability and validity of the Hartofilakidis classification system of congenital hip disease in adults C. K. Yiannakopoulos & T. Xenakis & T. Karachalios & G. C. Babis & G. Hartofilakidis Received: 29 August 2007 / Revised: 9 September 2007 / Accepted: 18 September 2007 / Published online: 6 November 2007 # Springer-Verlag 2007 Abstract The reliability and validity of the Hartofilakidis et al. classification system in adults with congenital hip disease (CHD) were examined. The radiographs of 102 adult patients (158 hips) with CHD were independently assessed by three senior surgeons. Interobserver variability was assessed by examining the agreement between the three raters while validity of the classification system was assessed by examining the agreement between the assess- ment by either one of the three raters and the intraoperative finding (reference standard). The interobserver agreement between the three observers was high ranging from 0.720 to 0.854 (substantial to excellent) while the agreement of the preoperative prediction with the intraoperative findings was 87.4% (K=0.823, excellent agreement). The Hartofilakidis et al. classification system reliably predicts from preoper- ative pelvis radiographs the bone deficiencies encountered during the operation. Résumé Nous avons voulu tester dans ce travail la fiabilité et la viabilité de la classification d’Hartofilakidis dans les séquelles des affections congénitales de la hanche. Les radios de 102 adultes (158 hanches) avec lésions con- génitales ont été analysées, de façon indépendante par trois chirurgiens seniors avec validation inter observateur et intra observateur. Les résultats de cette analyse inter observateur sont hautement significatifs de 0.720 à 0.854 et les prévisions pré opératoires confirmées par les constatations per opératoires sont excellentes 87.4% (k=0.823). La classification d’Hartofilakidis est un système parfaitement viable qui permet de prévoir un pré opératoire les lésions que l’on pourra constater en per opératoire. Introduction For the classification of congenital hip disease (CHD) in adults various systems have been proposed [1, 12, 16, 17]. The Hartofilakidis et al. classification system, initially published in 1988, relies on intraoperative findings to describe the hip pathology encountered during the oper- ation [1, 2]. The major distinguishing feature is the description of acetabular deformity (Table 1). This classi- fication system encompasses three types of deformity in the adult hip, i.e. dysplasia, low dislocation and high disloca- tion (Fig. 1). The demographics and clinical presentation vary between the various CHD types [13]. Patients with dysplasia become symptomatic later in adult life, the anatomical distortion of the femur and the acetabulum is milder, the operation is simpler and the results of total hip replacement (THR) are generally better compared to the more severe forms of the disease [14]. In 20–50% of adults with hip osteoarthritis the underlying problem is hip dysplasia [9]. International Orthopaedics (SICOT) (2009) 33:353–358 DOI 10.1007/s00264-007-0472-0 C. K. Yiannakopoulos : G. C. Babis : G. Hartofilakidis First Orthopaedic Department, University of Athens Medical School, Athens, Greece T. Xenakis Department of Orthopaedic Surgery, School of Medicine, University of Ioannina, Ioannina, Greece T. Karachalios Orthopaedic Department, School of Medicine, Faculty of Health Sciences, University of Thessaly, Papakyriazi 22, Larissa 41222, Greece C. K. Yiannakopoulos (*) Byzantiou 2, Nea Smyrni, Athens 17121, Greece e-mail: cky@ath.forthnet.gr