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Osteoarthritis Cartilage. 2014 Mar;22(3):431-9. doi: 10.1016/j.joca.2013.12.018. Epub 2014 Jan 11.

Body mass index is not a clinically meaningful predictor of patient reported outcomes of primary hip replacement surgery: prospective cohort study.

Author information

1
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK. Electronic address: andrew.judge@ndorms.ox.ac.uk.
2
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK. Electronic address: rajbir.batra@ndorms.ox.ac.uk.
3
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK. Electronic address: geraint.thomas@ndorms.ox.ac.uk.
4
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK. Electronic address: david.beard@ndorms.ox.ac.uk.
5
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK. Electronic address: kassim.javaid@ndorms.ox.ac.uk.
6
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK. Electronic address: david.murray@ndorms.ox.ac.uk.
7
Peninsula College of Medicine and Dentistry, C420, Portland Square, University of Plymouth Campus, Drake Circus, Plymouth PL4 8AA, UK. Electronic address: p.dieppe@exeter.ac.uk.
8
Institute for Muskuloskeletal Rehabilitation, Prevention and Health Service Research, Center for Sport Science and Sport Medicine (CSSB), Center for Musculoskeletal Surgery (CMSC), Charité Universitätsmedizin Berlin, Philippstraße 13, 10115 Berlin, Germany; Department of Orthopaedics, Traumatology and Sports Medicine, Medical Park Berlin Humboldtmühle, An der Mühle 2-9, D-13507 Berlin, Germany. Electronic address: karsten.dreinhoefer@charite.de.
9
Department of Orthopaedic Surgery, University Hospital Carl Gustav Carus, Medical Faculty of the Technical University of Dresden, Germany. Electronic address: klaus-peter.guenther@uniklinikum-dresden.de.
10
Elective Orthopaedic Centre, Dorking Road, Epsom, Surrey KT18 7EG, UK. Electronic address: richard.field@eoc.nhs.uk.
11
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK. Electronic address: cc@mrc.soton.ac.uk.
12
Oxford NIHR Musculoskeletal Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford OX3 7LD, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK. Electronic address: nigel.arden@ndorms.ox.ac.uk.

Abstract

OBJECTIVES:

To describe whether body mass index (BMI) is a clinically meaningful predictor of patient reported outcomes following primary total hip replacement (THR) surgery.

DESIGN:

Combined data from prospective cohort studies. We obtained information from four cohorts of patients receiving primary THR for osteoarthritis: Exeter Primary Outcomes Study (EPOS) (n = 1431); EUROHIP (n = 1327); Elective Orthopaedic Centre (n = 2832); and St. Helier (n = 787). The exposure of interest was pre-operative BMI. Confounding variables included: age, sex, SF-36 mental health, comorbidities, fixed flexion, analgesic use, college education, OA in other joints, expectation of less pain, radiographic K&L grade, ASA grade, years of hip pain. The primary outcome was the Oxford Hip Score (OHS). Regression models describe the association of BMI on outcome adjusting for all confounders.

RESULTS:

For a 5-unit increase in BMI, the attained 12-month OHS decreases by 0.78 points 95%CI (0.27-1.28), P-value 0.001. Compared to people of normal BMI (20-25), those in the obese class II (BMI 35-40) would have a 12-month OHS that is 2.34 points lower. Although statistically significant this effect is small and not clinically meaningful in contrast to the substantial change in OHS seen across all BMI groupings. In obese class II patients achieved a 22.2 point change in OHS following surgery.

CONCLUSIONS:

Patients achieved substantial change in OHS after THR across all BMI categories, which greatly outweighs the small difference in attained post-operative score. The findings suggest BMI should not present a barrier to access THR in terms of PROMs.

KEYWORDS:

Body mass index; Decision making; Epidemiology; Hip replacement; Osteoarthritis; Patient reported outcome

PMID:
24418679
PMCID:
PMC4147658
DOI:
10.1016/j.joca.2013.12.018
[Indexed for MEDLINE]
Free PMC Article

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