The effect of body mass index on the risk of post-operative complications during the 6 months following total hip replacement or total knee replacement surgery.
OBJECTIVE
To assess the effect of obesity on 6-month post-operative complications following total knee (TKR) or hip (THR) replacement.


METHODS
Data for patients undergoing first THR or TKR between 1995 and 2011 was taken from the Clinical Practice Research Datalink. Logistic regression was used to assess whether body mass index (BMI) was associated with 6-month post-operative complications [deep vein thrombosis or pulmonary embolism (DVT/PE), myocardial infarction (MI), stroke, respiratory infection, anaemia, wound infection, urinary tract infection or death] after controlling for the effects of age, gender, smoking, drinking, socio-economic status (SES), co-morbidities and medications.


RESULTS
31,817 THR patients and 32,485 TKR patients were identified for inclusion. Increasing BMI was associated with a significantly higher risk of wound infections, from 1.6% to 3.5% in THR patients (adjusted P < 0.01), and from 3% to 4.1% (adjusted P < 0.05) in TKR patients. DVT/PE risk also increased with obesity from 2.2% to 3.3% (adjusted P < 0.01) in THR patients and from 2.0% to 3.3% (adjusted P < 0.01) in TKR patients. Obesity was not associated with increased risk of other complications.


CONCLUSIONS
Whilst an increased risk of wound infection and DVT/PE was observed amongst obese patients, absolute risks remain low and no such association was observed for MI, stroke and mortality. However this is a selected cohort (eligible for surgery according to judgement of NHS GPs and surgeons) and as such these results do not advocate surgery be given without consideration of BMI, but indicate that universal denial of surgery based on BMI is unwarranted.
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: gemma.wallace@ndorms.ox.ac.uk.
G
G
Wallace
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.
A
A
Judge
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; GREMPAL Research Group, IDIAP Jordi Gol Universitat Autonoma de Barcelona, Spain. Electronic address: daniel.prietoalhambra@ndorms.ox.ac.uk.
D
D
Prieto-Alhambra
Utrecht Institute for Pharmaceutical Sciences, Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht University, The Netherlands; Department of Clinical Pharmacy and Toxicology, Maastricht University Medical Centre, Maastricht, The Netherlands. Electronic address: f.devries@uu.nl.
F
F
de Vries
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.
N K
NK
Arden
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.
C
C
Cooper
D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D015992:Body Mass Index; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000453:epidemiology; D009765:Obesity / Q000150:complications*; D011183:Postoperative Complications / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology; D013530:Surgical Wound Infection / Q000453:epidemiology; D013997:Time Factors; D020246:Venous Thrombosis / Q000453:epidemiology
Arthroplasty; Electronic health records; Epidemiology; Obesity; Post-operative complications