INTEROBSERVER AND INTRAOBSERVER STUDY OF RADIOGRAPHIC ASSESSMENT OF CEMENTED TOTAL HIP ARTHROPLASTIES

Radiographs are commonly used to identify loosened total hip prosthese s. Interobserver and intraobserver variation was studied in an attempt to interpret 60 random pairs of radiographs with a time interval of 6 months to 12 years between the radiographs. Each of the four observer s evaluated all pairs of radiographs independently, and the evaluation s were repeated after 2 to 4 weeks. Each observer classified the femor al stem and the acetabular cup separately as stable or loose. Radioluc ent lines of more than 2 mm were recorded. For the acetabular componen ts, any change in inclination or migration was noted, and for the femo ral components, subsidence or any change in varus or valgus of the ste m was noted. There was considerable disagreement in observations of th e acetabular component; agreement by all four observers was obtained i n only 34 of 60 cases (57%). For the femoral component, agreement was obtained in 37 cases (62%). The observers agreed two and two (pairwise ) on the acetabular component in 70 to 83% of cases and on the femoral component, in 72 to 82% of cases. Intraobserver variation was great w ith regard to the acetabular component, with kappa values ranging from 0.489 to 0.633. As to the femoral component, kappa values ranged from 0.737 to 0.800. Interpretation of radiographs of artificial hip arthr oplasty is difficult, and comparisons between different series of impl ants should be made by the same person.