Radiographic assessment of uncemented total hip arthroplasty: reliability of the Engh Grading Scale.

BACKGROUND Radiographic evaluation has a prominent place in the follow-up of long-term results of uncemented total hip arthroplasty (THA). The most prominent scale reported in studies is the Engh Grading Scale, but there is a lack of literature on the reliability of the scale. METHODS We evaluated intra- and interrater reliability of the Engh Grading System for uncemented THA using 26 follow-up radiographs of patients who had primary uncemented THAs. Four evaluators with different skill levels and specialties participated: 2 arthroplasty surgeons, an orthopedic resident and a radiologist. Reliability was measured using a weighted κ coefficient for paired comparisons among the evaluators. RESULTS Intrarater reliability was dependent on the skill and specialty of the evaluator, with the highest values achieved for the arthroplasty surgeons (κ = 0.52 and κ = 0.68) and the lowest values for the radiologist (κ = 0.14). Interrater reliability was comparable among participants, regardless of skill or specialty, and rated a moderate level of reliability (κ = 0.29-0.41) for all pairings. CONCLUSION The Engh Grading Scale appears to be reliable when used by a single, experienced arthroplasty surgeon. Caution must be exercised when multiple raters are used, regardless of experience, as the interrater reliability achieved lower ratings.