International variation in distribution of ASA class in patients undergoing total hip arthroplasty and its influence on mortality: data from an international consortium of arthroplasty registries

Alan J Silman; Christophe Combescure; Rory J Ferguson; Stephen E Graves; Elizabeth W Paxton; Chris Frampton; Ove Furnes; Anne Marie  Fenstad; Gary Hooper; Anne Garland; Anneke Spekenbrink- Spooren; J Mark Wilkinson; Keijo Mäkelä; Anne Lübbeke; Ola Rolfson

doi:10.1080/17453674.2021.1892267

Authors

Alan J Silman Nuffield Department of Orthopaedics Rheumatology and Musculoskeletal Sciences, University of Oxford, UK
Christophe Combescure Division of Clinical Epidemiology, Geneva University Hospitals, Switzerland
Rory J Ferguson Nuffield Department of Orthopaedics Rheumatology and Musculoskeletal Sciences, University of Oxford, UK
Stephen E Graves Australian Orthopaedic Association National Joint Replacement Registry, Australia
Elizabeth W Paxton Surgical Outcomes and Analysis, Kaiser Permanente, San Diego, USA
Chris Frampton Department of Medicine, University of Otago, Christchurch, New Zealand
Ove Furnes The Norwegian Arthroplasty Register, Department of Orthopedic Surgery, Haukeland University Hospital, Bergen, Norway; Department of Clinical Medicine, University of Bergen, Norway
Anne Marie Fenstad The Norwegian Arthroplasty Register, Department of Orthopedic Surgery, Haukeland University Hospital, Bergen, Norway
Gary Hooper Orthopaedic Surgery and Musculoskeletal Medicine, University of Otago, Christchurch, New Zealand
Anne Garland Department of Orthopaedics, Visby lasarett Institute of Surgical Scienses, Uppsala Universitet, Uppsala, Sweden
Anneke Spekenbrink- Spooren Dutch Arthroplasty Register, ’s-Hertogenbosch, The Netherlands
J Mark Wilkinson Department of Oncology and Metabolism, University of Sheffield, Sheffield, UK; National Joint Registry for England, Wales, Northern Ireland, and Isle of Man, London, UK
Keijo Mäkelä Department of Orthopaedics and Traumatology, Turku University Hospital and University of Turku, Turku, Finland
Anne Lübbeke Nuffield Department of Orthopaedics Rheumatology and Musculoskeletal Sciences, University of Oxford, UK; Division of Orthopaedics and Trauma Surgery, Geneva University Hospitals, Switzerland
Ola Rolfson Department of Orthopaedics, Institute of Clinical Sciences Sahlgrenska Academy, University of Gothenburg, Sweden; The Swedish Hip Arthroplasty Register, Gothenburg, Sweden

DOI:

https://doi.org/10.1080/17453674.2021.1892267

Abstract

Background and purpose — A challenge comparing outcomes from total hip arthroplasty between countries is variation in preoperative characteristics, particularly comor- bidity. Therefore, we investigated between-country variation in comorbidity in patients based on ASA class distribution, and determined any variation of ASA class to mortality risk between countries.

Patients and methods — All arthroplasty registries col- lecting ASA class and mortality data in patients with elective primary THAs performed 2012–2016 were identified. Survival analyses of the influence of ASA class on 1-year mortality were performed by individual registries, followed by meta-analysis of aggregated data.

Results — 6 national registries and 1 US healthcare organization registry with 418,916 THAs were included. There was substantial variation in the proportion of ASA class III/ IV, ranging from 14% in the Netherlands to 39% in Finland. Overall, 1-year mortality was 0.93% (95% CI 0.87–1.01) and increased from 0.2% in ASA class I to 8.9% in class IV. The association between ASA class and mortality measured by hazard ratios (HR) was strong in all registries even after adjustment for age and sex, which reduced them by half in all registries. Combined adjusted HRs were 2.0, 6.1, and 22 for ASA class II–IV vs. I, respectively. Associations were moderately heterogeneous across registries.

Interpretation — We observed large variation in ASA class distribution between registries, possibly explained by differences in background morbidity and/or international variation in access to surgery. The similar, strong mortal- ity trends by ASA class between countries enhance the relevance of its use as an indicator of comorbidity in international registry studies.