Reliability and Accuracy of the Outerbridge Classification in Staging of Cartilage Defects

Orthopaedic Surgery, vol. 16, pp. 1187–1195

Abstract

OBJECTIVE: The decision on whether or not and how to treat a local cartilage defect is still made intraoperatively based on the visual presentation of the cartilage and findings from indentations with an arthroscopic probe. The treatment decision is then usually based on grading according to established classifications systems, which, therefore, need to have high reliability and accuracy. The aim of the present study was to evaluate the reliability and accuracy of the Outerbridge classification in staging cartilage defects. METHODS: We performed an observer arthroscopic study using the Outerbridge classification on seven fresh-frozen human cadaveric knees, which collectively exhibited nine cartilage defects. To evaluate accuracy, defect severity was verified through histological examination. Interrater and intrarater reliabilites were calculated using Cohen's kappa and the intra-class correlation coefficient (ICC 3.1). RESULTS: The interrater and intrarater reliability for the Outerbridge classification ranged from poor to substantial, with 0.24 ≤ κ ≤ 0.70 and κ = 0.55 to κ = 0.66, respectively. The accuracy evaluated by comparison with the histological examination was 63% overall. The erroneous evaluations were, however, still often at the discrimination of grade 2 and 3. We did not find any relationship between higher experience and accuracy or intraobserver reliability. Taken together, these results encourage surgeons to further use diagnostic arthroscopy for evaluating cartilage lesions. Nevertheless, especially in grade 2 and 3, deviations from the histology were observed. This is, however, the point where a decision is made on whether to surgically address the defect or not. CONCLUSION: Diagnostic arthroscopy is the standard for cartilage lesion assessment, yet interobserver reliability is fair to substantial. Caution is warranted in interpreting varied observer results. The accuracy of the "simpler" Outerbridge classification is insufficient compared to histological examinations, highlighting the need for improved techniques in guideline-based intraoperative decision-making.

Authors 6

1. Moritz Mederake

   University of Tübingen · BG Klinik Tübingen

   Affiliation as printed

   Department of Trauma and Reconstructive Surgery, BG Klinik University of Tübingen Tübingen Germany

2. Vivien Scheibe

   University of Tübingen · Universitätsklinikum Tübingen

   Affiliation as printed

   Department Orthopedic Surgery University of Tübingen Tübingen Germany

   Laboratory of Cell Biology, Department of Orthopaedic Surgery University Hospital of Tübingen Tübingen Germany

   Medical Faculty of the University of Tübingen Tübingen Germany

3. Philipp Dalheimer
   Affiliation as printed

   Orthopaedic Practice Nagold‐Riedt, Chan, Dalheimer Nagold Germany

   Orthopaedic Practice Nagold-Riedt, Chan, Dalheimer, Nagold, Germany

4. Daniel Schüll

   University of Tübingen · BG Klinik Tübingen

   Affiliation as printed

   Department of Trauma and Reconstructive Surgery, BG Klinik University of Tübingen Tübingen Germany

5. Marina Danalache corresponding

   University of Tübingen · Universitätsklinikum Tübingen

   Affiliation as printed

   Department Orthopedic Surgery University of Tübingen Tübingen Germany

   Laboratory of Cell Biology, Department of Orthopaedic Surgery University Hospital of Tübingen Tübingen Germany

   Medical Faculty of the University of Tübingen Tübingen Germany

6. Ulf Krister Hofmann Aachen Department of Orthopaedic, Trauma, and Reconstructive Surgery

   RWTH Aachen University · Universitätsklinikum Aachen · University of Tübingen

   Affiliation as printed

   Department Orthopedic Surgery University of Tübingen Tübingen Germany

   Department of Orthopaedic, Trauma, and Reconstructive Surgery RWTH Aachen University Hospital Aachen Germany

   Medical Faculty of the University of Tübingen Tübingen Germany

   Department of Orthopaedic, Trauma, and Reconstructive Surgery, RWTH Aachen University Hospital, Aachen, Germany