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

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.

Keywords

Arthroscopy / Articular Cartilage / Histology / Osteoarthritis / Outerbridge Classification

References

[1] HunterDJ, Bierma-Zeinstra S. Osteoarthritis. Lancet. 2019;393:1745–1759.

[2] Barber-WestinS, NoyesF. Articular Cartilage Rating Systems; 2010. p. e57–e73.

[3] BrunoF, Arrigoni F, PalumboP, NatellaR, Maggialetti N, ReginelliA, et al. New advances in MRI diagnosis of degenerative osteoarthropathy of the peripheral joints. Radiol Med. 2019;124:1121–1127.

[4] HafnerT, SchockJ, PostM, Abrar DB, SewerinP, LinkaK, et al. A serial multiparametric quantitative magnetic resonance imaging study to assess proteoglycan depletion of human articular cartilage and its effects on functionality. Sci Rep. 2020;10:15106.

[5] BrittbergM, Peterson L. Introduction of an articular cartilage classification. ICRS Newsletter. 1998;1:5–8.

[6] van den BorneMP, Raijmakers NJ, VanlauweJ, VictorJ, de Jong SN, BellemansJ, et al. International cartilage repair society (ICRS) and Oswestry macroscopic cartilage evaluation scores validated for use in autologous chondrocyte implantation (ACI) and microfracture. Osteoarthr Cartil. 2007;15:1397–1402.

[7] NoyesFR, Stabler CL. A system for grading articular cartilage lesions at arthroscopy. Am J Sports Med. 1989;17:505–513.

[8] OuterbridgeRE. The etiology of chondromalacia patellae. J Bone Jt Surg Br. 1961;43-B:752–757.

[9] OuterbridgeRE, DunlopJA. The problem of chondromalacia patellae. Clin Orthop Relat Res. 1975;110:177–196.

[10] SlatteryC, KweonCY. Classifications in brief: Outerbridge classification of chondral lesions. Clin Orthop Relat Res. 2018;476:2101–2104.

[11] SpahnG, Klinger HM, HofmannGO. How valid is the arthroscopic diagnosis of cartilage lesions? Results of an opinion survey among highly experienced arthroscopic surgeons. Arch Orthop Trauma Surg. 2009;129:1117–1121.

[12] BrittbergM, Winalski CS. Evaluation of cartilage injuries and repair. J Bone Jt Surg. 2003;85:58–69.

[13] CameronML, BriggsKK, SteadmanJR. Reproducibility and reliability of the outerbridge classification for grading chondral lesions of the knee arthroscopically. Am J Sports Med. 2003;31:83–86.

[14] BrismarBH, Wredmark T, MovinT, LeanderssonJ, Svensson O. Observer reliability in the arthroscopic classification of osteoarthritis of the knee. J Bone Jt Surg Br. 2002;84:42–47.

[15] LasmarNP, LasmarRC, VieiraRB, de Oliveira JR, ScarpaAC. Assessment of the reproducibility of the outerbridge and Fsa classifications for chondral lesions of the knee. Rev Bras Ortop. 2011;46:266–269.

[16] MarxRG, ConnorJ, LymanS, Amendola A, AndrishJT, KaedingC, et al. Multirater agreement of arthroscopic grading of knee articular cartilage. Am J Sports Med. 2005;33:1654–1657.

[17] AmenabarT, PirizJ, MellaC, Hetaimish BM, O'DonnellJ. Reliability of 3 different arthroscopic classifications for chondral damage of the acetabulum. Arthroscopy. 2015;31:1492–1496.

[18] DwyerT, MartinCR, KendraR, Sermer C, ChahalJ, Ogilvie-HarrisD, et al. Reliability and validity of the arthroscopic international cartilage repair society classification system: correlation with histological assessment of depth. Arthroscopy. 2017;33:1219–1224.

[19] FigueroaD, CalvoR, VaismanA, Carrasco MA, MoragaC, DelgadoI. Knee chondral lesions: incidence and correlation between arthroscopic and magnetic resonance findings. Arthroscopy. 2007;23:312–315.

[20] CurlWW, KromeJ, GordonES, Rushing J, SmithBP, PoehlingGG. Cartilage injuries: a review of 31,516 knee arthroscopies. Arthroscopy. 1997;13:456–460.

[21] Muller-GerblM, Schulte E, PutzR. The thickness of the calcified layer of articular cartilage: a function of the load supported? J Anat. 1987;154:103–111.

[22] HuntN, Sanchez-Ballester J, PanditR, ThomasR, Strachan R. Chondral lesions of the knee: a new localization method and correlation with associated pathology. Arthroscopy. 2001;17:481–490.

[23] JavedA, Siddique M, VaghelaM, HuiAC. Interobserver variations in intra-articular evaluation during arthroscopy of the knee. J Bone Jt Surg Br. 2002;84:48–49.

[24] HallFM, WyshakG. Thickness of articular cartilage in the normal knee. J Bone Jt Surg Am. 1980;62:408–413.

[25] SpahnG, Klinger HM, BaumsM, PinkepankU, Hofmann GO. Reliability in arthroscopic grading of cartilage lesions: results of a prospective blinded study for evaluation of inter-observer reliability. Arch Orthop Trauma Surg. 2011;131:377–381.

[26] HofmannUK, KellerRL, GesickiM, Walter C, MittagF. Interobserver reliability when classifying MR imaging of the lumbar spine: written instructions alone do not suffice. Magn Reson Med Sci. 2020;19:207–215.

[27] CykowskaA, Danalache M, BonnaireFC, FeierabendM, Hofmann UK. Detecting early osteoarthritis through changes in biomechanical properties – a review of recent advances in indentation technologies in a clinical arthroscopic setup. J Biomech. 2022;132:110955.

[28] ScheibeV. Arthroskopische Anwendung von Autofluoreszenz des Gelenkknorpels zur Quantifizierung von Knorpelschäden im Kniegelenk. Tübingen: Orthopädische Universitätsklinik Tübingen. Universitätsbibliothek Tübingen, Eberhard Karls University of Tuebingen; 2023.

[29] VogtS, BraunS, ImhoffAB. Stage oriented surgical cartilage therapy. Current situation. Z Rheumatol. 2007;66:493–503; quiz 504.

RIGHTS & PERMISSIONS

2024 The Authors. Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.