Reliability of the Oswestry-Bristol Classification for trochlear dysplasia expanded characteristics

Abstract

Aims The Oswestry-Bristol Classification (OBC) was recently described as an MRI-based classification tool for the femoral trochlear. The authors demonstrated better inter-and intraobserver agreement compared to the Dejour classification. As the OBC could potentially provide a very useful MRI-based grading system for trochlear dysplasia, it was the aim to determine the inter-and intraobserver reliability of the classification system from the perspective of the non-founder. Methods Two orthopaedic surgeons independently assessed 50 MRI scans for trochlear dysplasia and classified each according to the OBC. Both observers repeated the assessments after six weeks. The inter-and intraobserver agreement was determined using Cohen’s kappa statistic and S-statistic nominal and linear weights. Results The OBC with grading into four different trochlear forms showed excellent inter-and intra-observer agreement with a mean kappa of 0.78. Conclusion The OBC is a simple MRI-based classification system with high inter-and intraobserver reli-ability. It could present a useful tool for grading the severity of trochlear dysplasia in daily practice.