Abstract: Risk factors for inflammatory pseudotumour formation
following
hip resurfacing
Complete Study
http://www.jbjs.org.uk/cgi/content/abstract/91-B/12/1566
S. Glyn-Jones, MA, FRCS(Orth), DPhil, Senior
Lecturer, Consultant Orthopaedic Surgeon1; H.
Pandit, FRCS(Orth), Senior Clinical Fellow1;
Y.-M. Kwon, FRCS(Orth), FRACS(Orth), Research Fellow1;
H. Doll, MSc, DPhil, Senior Medical Statistician2;
H. S. Gill, BEng, DPhil, University Lecturer in
Orthopaedic Engineering1; and D. W. Murray,
MD, FRCS(Orth), Consultant Orthopaedic Surgeon,
Professor1
1 Department of
Orthopaedics, Nuffield Orthopaedic Centre Rheumatology
and Musculoskeletal Sciences
2 Department of Public Health University of
Oxford, Windmill Lane, Headington, Oxford OX3 7LD, UK.
Metal-on-metal hip resurfacing is
commonly performed for osteoarthritis in
young active patients. We have observed cystic or solid
masses, which we have called inflammatory
pseudotumours, arising around these devices.
They may cause soft-tissue destruction with severe
symptoms and a poor outcome after revision
surgery. The aim of this study was to
determine the incidence of and risk factors
for pseudotumours that are serious enough to require
revision surgery.
Since 1999, 1419 metal-on-metal hip resurfacings have
been implanted by our group in 1224 patients;
1.8% of the patients had a revision for
pseudotumour. In this series the Kaplan-Meier cumulative
revision rate for pseudotumour increased
progressively with time. At eight years, in
all patients, it was 4% (95% confidence
interval (CI) 2.2 to 5.8). Factors significantly
associated with an increase in revision rate
were female gender (p < 0.001), age under 40
(p = 0.003), small components (p = 0.003),
and dysplasia (p = 0.019), whereas implant type was not
(p = 0.156). These factors were
inter-related, however, and on fitting a Cox
proportional hazard model only gender (p = 0.002) and
age (p = 0.024) had a significant independent
influence on revision rate; size nearly
reached significance (p = 0.08). Subdividing
the cohort according to significant factors, we found
that the revision rate for pseudotumours in
men was 0.5% (95% CI 0 to 1.1) at eight years
whereas in women over 40 years old it was 6%
(95% CI 2.3 to 10.1) at eight years and in women under
40 years it was 13.1% at six years (95% CI 0
to 27) (p < 0.001).
We recommend that resurfacings are undertaken with
caution in women, particularly those under 40
years of age but they remain a good option in
young men. Further work is required to understand
the aetiology of pseudotumours so that this
complication can be avoided.
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