Developing a new CT-based bone defect classification in revision knee arthroplasty : a Delphi consensus study.

Aims: To seek consensus on the principles and criteria necessary to develop a CT-based bone defect classification (BDC) for revision knee arthroplasty. Methods: A three-round structured Delphi study was conducted. First, five interviews were held with international knee revision experts to support the development of 29 statements. Two consecutive rounds of Delphi survey statements were distributed among 56 international knee revision experts in the first round, and to 37 in the second round. Consensus (≥ 80% agreement) was sought on the statements covering bone defect definitions, imaging, and zonal assessment. Results: A total of 37 experts responded to the first survey round, and 34 also completed the second round. Consensus was reached on 93% of the statements after both survey rounds. Experts agreed that a BDC should guide both surgical planning and implant selection, and that CT imaging improves knee revision bone defect assessment. Consensus was also reached on the definition of a bone defect. While anatomical zones (epiphysis, metaphysis, diaphysis) were considered important for inclusion in a BDC, the results showed no consensus on which landmarks define these anatomical zones. Conclusion: The expert panel indicated that CT evaluation and distinct assessment of anatomical zones are essential in a (new) BDC, although no consensus was reached on the definition of those anatomical zones. Moreover, a CT-based BDC should be useful for guiding surgical planning and implant selection.