Ottawa classification for symptomatic acetabular dysplasia assessment of interobserver and intraobserver reliability

K Bali; K Smit; M Ibrahim; S Poitras; G Wilkin; R Galmiche; E Belzile; P E Beaulé

doi:10.1302/2046-3758.95.BJR-2019-0155.R1

Ottawa classification for symptomatic acetabular dysplasia assessment of interobserver and intraobserver reliability

Bone Joint Res. 2020 Jun 8;9(5):242-249. doi: 10.1302/2046-3758.95.BJR-2019-0155.R1. eCollection 2020 May.

Authors

K Bali¹, K Smit², M Ibrahim¹, S Poitras³, G Wilkin¹, R Galmiche¹, E Belzile⁴, P E Beaulé⁵

Affiliations

¹ Division of Orthopaedic Surgery, Faculty of Medicine, University of Ottawa, The Ottawa Hospital, Ottawa, Canada.
² Division of Orthopaedic Surgery, Children's Hospital of Eastern Ontario (CHEO), Ottawa, Canada.
³ Physiotherapy Program, School of Rehabilitation, Faculty of Health Sciences, University of Ottawa, Ottawa, Canada.
⁴ Division of Orthopaedic Surgery, University of Laval, Québec, Canada.
⁵ University of Ottawa, Ottawa, Canada; Head, Division of Orthopaedic Surgery, The Ottawa Hospital, Ottawa, Canada.

PMID: 32566146
PMCID: PMC7284290
DOI: 10.1302/2046-3758.95.BJR-2019-0155.R1

Abstract

Aims: The aim of the current study was to assess the reliability of the Ottawa classification for symptomatic acetabular dysplasia.

Methods: In all, 134 consecutive hips that underwent periacetabular osteotomy were categorized using a validated software (Hip2Norm) into four categories of normal, lateral/global, anterior, or posterior. A total of 74 cases were selected for reliability analysis, and these included 44 dysplastic and 30 normal hips. A group of six blinded fellowship-trained raters, provided with the classification system, looked at these radiographs at two separate timepoints to classify the hips using standard radiological measurements. Thereafter, a consensus meeting was held where a modified flow diagram was devised, before a third reading by four raters using a separate set of 74 radiographs took place.

Results: Intrarater results per surgeon between Time 1 and Time 2 showed substantial to almost perfect agreement among the raters (κappa = 0.416 to 0.873). With respect to inter-rater reliability, at Time 1 and Time 2 there was substantial agreement overall between all surgeons (Time 1 κappa = 0.619; Time 2 κappa = 0.623). Posterior and anterior rating categories had moderate and fair agreement at Time 1 (posterior κappa = 0.557; anterior κappa = 0.438) and Time 2 (posterior κappa = 0.506; anterior κappa = 0.250), respectively. At Time 3, overall reliability (κappa = 0.687) and posterior and anterior reliability (posterior κappa = 0.579; anterior κappa = 0.521) improved from Time 1 and Time 2.

Conclusion: The Ottawa classification system provides a reliable way to identify three categories of acetabular dysplasia that are well-aligned with surgical management. The term 'borderline dysplasia' should no longer be used.Cite this article: Bone Joint Res. 2020;9(5):242-249.

Keywords: Classification; Hip dysplasia; Lateral centre edge angle; Periacetabular osteotomy; Retroversion.