In Brief: Classifications in Brief: Brooker Classification of Heterotopic Ossification After Total Hip Arthroplasty

THA is a frequently performed surgery for the treatment of patients with osteoarthritis, rheumatoid arthritis, avascular necrosis, developmental dysplasia, and many other forms of hip pathology. Heterotopic ossification (HO) is a common complication after THA with a frequency of 26% to 41% reported in recent studies [2, 20, 21]. The majority of HO is not clinically important, but severe HO may lead to decreased hip ROM [12] and increased pain [7]. Multiple different classification schemes have been proposed to describe the degree of HO after THA, including those by Brooker et al. [3], Hamblen et al. [9], DeLee et al. [5], and Kjaersgaard-Andersen et al. [11] as well as by Arcq [1] within the German literature. All of the classification systems use plain radiographs in at least the AP plane, but some make use of other radiographic views as well. The Brooker classification system was one of the earliest systems described and remains very widely used in contemporary literature. Some groups have suggested modifications or additions to the Brooker system with the goal of improving consistency and predictability [6, 19, 23], whereas others have focused on simplifying the Brooker system to improve communication and reproducibility [22]. Although these authors have argued that their revisions demonstrate an improvement over the Brooker classification, the original Brooker classification remains a commonly used system for classifying HO after THA.