title: Heterotopic ossification after total hip arthroplasty: a critical analysis of the Brooker classification and proposal of a simplified rating system.
abstract: We evaluated the reproducibility of the Brooker classification for heterotopic ossification (HO) and, based on the results and weaknesses observed, proposed a simplified system with addition of objective criteria. Six observers classified radiographs of 169 total hip arthroplasties, using the Brooker classification and a modified system consisting of i) absence of HO or islands measuring <1 cm in length, ii) islands >1 cm or spurs leaving at least 1 cm between femur and pelvis, and iii) spurs leaving <1 cm between opposing surfaces or bony ankylosis. Reproducibility was calculated using kappa statistics. For the Brooker classification, interobserver kappa averaged 0.43 (range, 0.74-0.18) (poor). Intraobserver kappa averaged 0.74 (fair). For the modified classification, interobserver kappa averaged 0.59 (range, 0.51-0.76) (fair). Intraobserver kappa averaged 0.78 (good). Interobserver differences were significant (P=.0085). Interobserver consistency to detect severe HO (Brooker 3 and 4, or grade C) improved from 52% to 76% with the modified system. The new classification showed adequate interobserver reproducibility, less variability, and improved consistency for classification of significant HO.
authors.affiliation: Institute of Orthopaedics Carlos E Ottolenghi, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina. agdv@bigfoot.com
authors.forename: Alejandro González
authors.initials: AG
authors.lastname: Della Valle
authors.forename: Patricio Salonia
authors.initials: PS
authors.lastname: Ruzo
authors.forename: Vito
authors.initials: V
authors.lastname: Pavone
authors.forename: Eric
authors.initials: E
authors.lastname: Tolo
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Mintz
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Salvati
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005271:Femur Head Necrosis / Q000601:surgery; D006801:Humans; D009999:Ossification, Heterotopic / Q000145:classification* / Q000209:etiology; D015207:Osteoarthritis, Hip / Q000601:surgery; D015203:Reproducibility of Results; D012189:Retrospective Studies