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A new classification system for the adult dysplastic hip requiring total hip arthroplasty: a reliability study
Mark S Gaston1, Paul Gaston, Peter Donaldson
1Edinburgh Orthopaedics, Royal Infirmary of Edinburgh, UK. mark.gaston@ed.ac.uk
Insights
A new classification system for adult developmental dysplasia of the hip (DDH) separates acetabular and femoral components. This system demonstrates substantial agreement, offering improved planning for total hip arthroplasty.
Area of Science:
- Orthopedics
- Radiology
- Surgical Planning
Background:
- Current classification systems for adult developmental dysplasia of the hip (DDH) inadequately address femoral geometry and leg length reconstruction during total hip arthroplasty.
- Existing systems, such as Crowe and Hartofilakidis, may not accurately predict surgical complexities in total hip arthroplasty for DDH patients.
Purpose of the Study:
- To introduce and validate a novel classification system for adult DDH that independently assesses acetabular and femoral components.
- To evaluate the reliability and potential utility of this new system in predicting surgical difficulties and outcomes in total hip arthroplasty.
Main Methods:
- A new classification system was developed, categorizing the acetabulum (AI-AIII) and femur (FI-FIII) separately.
- Fifty pre-operative hip DDH radiographs were reviewed by orthopedic specialists, registrars, and medical students using the new system and established Crowe and Hartofilakidis systems.
- Interobserver and intraobserver reliability were assessed using Fleiss' kappa coefficient.
Main Results:
- The new DDH classification system achieved substantial agreement, with interobserver reliability kappa scores of 0.69 and intraobserver reliability kappa scores of 0.67.
- The system demonstrated reliability comparable to the established Crowe and Hartofilakidis classification systems.
- The classification's reproducibility was confirmed in the adult DDH population.
Conclusions:
- The proposed classification system for adult DDH is reproducible and reliable.
- This novel system offers valuable insights for planning total hip arthroplasty, potentially predicting technical challenges and patient outcomes.
- Independent assessment of acetabular and femoral components enhances surgical planning for adult DDH patients.
Abstract:
Current classification systems used for developmental dysplasia of the hip (DDH) in adult patients about to undergo total hip arthroplasty use a combined assessment of the acetabulum and femur which ignores femoral geometry and problems related to reconstruction of leg length. Currently accepted systems are those of Crowe and Hartofilakidis; it is our opinion that they do not predict surgical difficulties encountered at total hip arthroplasty. We describe a new classification system for adult DDH that divides the acetabulum and femur into separate components. The acetabular classification comprises: AI: Dysplastic acetabulum; AII: The acetabulum associated with a low femoral dislocation; AIII: The post-surgical acetabulum, with (AIIIa) or without retained metalwork (AIIIb). The femoral classification consists of: FI: Dysplastic femur but contained within true or low acetabulum; FII: The high femur; FIII: Post-surgical femur, again with or without metalwork (FIIIa and FIIIb). 50 pre-operative radiographs of hips with DDH about to undergo total hip replacement were assessed by orthopaedic consultants, registrars and medical students. They were classified using the new system, Crowe and Hartofilakidis systems. Interobserver and intraobserever reliability was assessed using Fleiss' kappa coefficient with combined (acetabulum and femur) kappa scores for the new system of 0.69 for interobserver and 0.67 for intraobserver reliability. This equated to 'substantial agreement' according to Landis and Koch and the new system showed at least comparable levels of reliability to the Hartofilakidis and Crowe systems. We have demonstrated reproducibility of our new classification system for DDH in the adult population and believe it could provide useful information when planning arthroplasty and be used to predict technical difficulties and outcome.
