We wished to investigate the influence of metal debris exposure
on the subsequent immune response and resulting soft-tissue injury
following metal-on-metal (MoM) hip arthroplasty. Some reports have
suggested that debris generated from the head-neck taper junction
is more destructive than equivalent doses from metal bearing surfaces. We investigated the influence of the source and volume of metal
debris on chromium (Cr) and cobalt (Co) concentrations in corresponding
blood and hip synovial fluid samples and the observed agglomerated
particle sizes in excised tissues using multiple regression analysis
of prospectively collected data. A total of 199 explanted MoM hips
(177 patients; 132 hips female) were analysed to determine rates
of volumetric wear at the bearing surfaces and taper junctions. Aims
Patients and Methods
Patient-reported outcome measures (PROMs) are
increasingly being used to assess functional outcome and patient satisfaction.
They provide a framework for comparisons between surgical units,
and individual surgeons for benchmarking and financial remuneration.
Better performance may bring the reward of more customers as patients and
commissioners seek out high performers for their elective procedures.
Using National Joint Registry (NJR) data linked to PROMs we identified
22 691 primary total knee replacements (TKRs) undertaken for osteoarthritis
in England and Wales between August 2008 and February 2011, and
identified the surgical factors that influenced the improvements
in the Oxford knee score (OKS) and EuroQol-5D (EQ-5D) assessment
using multiple regression analysis. After correction for patient
factors the only surgical factors that influenced PROMs were implant
brand and hospital type (both p <
0.001). However, the effects
of surgical factors upon the PROMs were modest compared with patient
factors. For both the OKS and the EQ-5D the most important factors
influencing the improvement in PROMs were the corresponding pre-operative
score and the patient’s general health status. Despite having only
a small effect on PROMs, this study has shown that both implant
brand and hospital type do influence reported subjective functional
scores following TKR. In the current climate of financial austerity,
proposed performance-based remuneration and wider patient choice,
it would seem unwise to ignore these effects and the influence of
a range of additional patient factors.
Following arthroplasty of the knee, the patient’s
perception of improvement in symptoms is fundamental to the assessment
of outcome. Better clinical outcome may offset the inferior survival
observed for some types of implant. By examining linked National
Joint Registry (NJR) and patient-reported outcome measures (PROMs)
data, we aimed to compare PROMs collected at a minimum of six months
post-operatively for total (TKR: n = 23 393) and unicondylar knee
replacements (UKR: n = 505). Improvements in knee-specific (Oxford
knee score, OKS) and generic (EuroQol, EQ-5D) scores were compared
and adjusted for case-mix differences using multiple regression.
Whereas the improvements in the OKS and EQ-5D were significantly
greater for TKR than for UKR, once adjustments were made for case-mix
differences and pre-operative score, the improvements in the two
scores were not significantly different. The adjusted mean differences
in the improvement of OKS and EQ-5D were 0.0 (95% confidence interval (CI)
-0.9 to 0.9; p = 0.96) and 0.009 (95% CI -0.034 to 0.015; p = 0.37),
respectively. We found no difference in the improvement of either knee-specific
or general health outcomes between TKR and UKR in a large cohort
of registry patients. With concerns about significantly higher revision
rates for UKR observed in worldwide registries, we question the
widespread use of an arthroplasty that does not confer a significant
benefit in clinical outcome.