Heterotopic ossification of the hip following total hip replacement - Brooker Classification

Brooker classification divides heterotopic ossifications that form following total hip replacement to four classes. It was published in 1973 by Brooker et al.

Class Description
Class I islands of bone within soft tissues around hip
Class II bone spurs in pelvis or proximal end of femur leaving ≥1 cm between the opposing bone surfaces
Class III bone spurs that extend from pelvis or the proximal end of femur, which reduce the space between the opposing bone surfaces to <1cm
Class IV ankylosis of the hip on x-ray


1. Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr. Ectopic ossification following total hip replacement. Incidence and a method of classification. J Bone Joint Surg Am. 1973 Dec;55(8):1629–32.
2. Søballe K, Christensen F, Kristensen SS. Ectopic bone formation after total hip arthroplasty. Clin. Orthop. Relat. Res. 1988 Mar;(228):57–62.