Hip fracture commonly affects the frailest patients, of whom many are care-dependent, with a disproportionate risk of contracting COVID-19. We examined the impact of COVID-19 infection on hip fracture mortality in England. We conducted a cohort study of patients with hip fracture recorded in the National Hip Fracture Database between 1 February 2019 and 31 October 2020 in England. Data were linked to Hospital Episode Statistics to quantify patient characteristics and comorbidities, Office for National Statistics mortality data, and Public Health England’s SARS-CoV-2 testing results. Multivariable Cox regression examined determinants of 90-day mortality. Excess mortality attributable to COVID-19 was quantified using Quasi-Poisson models.Aims
Methods
To identify the responsiveness, minimal clinically important difference (MCID), minimal clinical important change (MIC), and patient-acceptable symptom state (PASS) thresholds in the 36-item Short Form Health Survey questionnaire (SF-36) (v2) for each of the eight dimensions and the total score following total knee arthroplasty (TKA). There were 3,321 patients undergoing primary TKA with preoperative and one-year postoperative SF-36 scores. At one-year patients were asked how satisfied they were and “How much did the knee arthroplasty surgery improve the quality of your life?”, which was graded as: great, moderate, little (n = 277), none (n = 98), or worse.Aims
Methods
There are limited published data detailing the volumetric material loss from tapers of conventional metal-on-polyethylene (MoP) total hip arthroplasties (THAs). Our aim was to address this by comparing the taper wear rates measured in an explanted cohort of the widely used Exeter THA with those measured in a group of metal-on-metal (MoM) THAs. We examined an existing retrieval database to identify all Exeter V40 and Universal MoP THAs. Volumetric wear analysis of the taper surfaces was conducted using previously validated methodology. These values were compared with those obtained from a series of MoM THAs using non-parametric statistical methodology. A number of patient and device variables were accounted for using multiple regression modelling.Aims
Patients and Methods
We have encountered patients who developed large joint fluid collections with massive elevations in chromium (Cr) and cobalt (Co) concentrations following metal-on-metal (MoM) hip arthroplasties. In some cases, retrieval analysis determined that these ion concentrations could not be explained simply by the wear rates of the components. We hypothesized that these effects may be associated with aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). We examined the influence of the ALVAL grade on synovial fluid Co and Cr concentrations following adjustment for patient and device variables, including volumetric wear rates. Initially restricting the analysis to include only patients with one MoM hip resurfacing device, we performed multiple regression analyses of prospectively collected data. We then repeated the same statistical approach using results from a larger cohort with different MoM designs, including total hip arthroplasties.Objectives
Patients and Methods
We sought to determine whether cobalt-chromium alloy (CoCr) femoral
stem tapers (trunnions) wear more than titanium (Ti) alloy stem
tapers (trunnions) when used in a large diameter (LD) metal-on-metal
(MoM) hip arthroplasty system. We performed explant analysis using validated methodology to
determine the volumetric material loss at the taper surfaces of
explanted LD CoCr MoM hip arthroplasties used with either a Ti alloy
(n = 28) or CoCr femoral stem (n = 21). Only 12/14 taper constructs
with a rough male taper surface and a nominal included angle close
to 5.666° were included. Multiple regression modelling was undertaken
using taper angle, taper roughness, bearing diameter (horizontal
lever arm) as independent variables. Material loss was mapped using
a coordinate measuring machine, profilometry and scanning electron
microscopy.Aims
Patients and Methods
Concerns have been raised that deformation of
acetabular shells may disrupt the assembly process of modular prostheses.
In this study we aimed to examine the effect that the strength of
bone has on the amount of deformation of the acetabular shell. The
hypothesis was that stronger bone would result in greater deformation.
A total of 17 acetabular shells were inserted into the acetabula
of eight cadavers, and deformation was measured using an optical
measuring system. Cores of bone from the femoral head were taken
from each cadaver and compressed using a materials testing machine.
The highest peak modulus and yield stress for each cadaver were used
to represent the strength of the bone and compared with the values
for the deformation and the surgeon’s subjective assessment of the
hardness of the bone. The mean deformation of the shell was 129
µm (3 to 340). No correlation was found between deformation and
either the maximum peak modulus (r² = 0.011, t = 0.426, p = 0.676) or
the yield stress (r² = 0.024, t = 0.614, p = 0.549) of the bone.
Although no correlation was found between the strength of the bone
and deformation, the values for the deformation observed could be
sufficient to disrupt the assembly process of modular acetabular
components. Cite this article:
Abnormal wear of cobalt-containing metal-on-metal
joints is associated with inflammatory pseudotumours. Cobalt ions
activate human toll-like receptor 4 (TLR4), which normally responds
to bacterial lipopolysaccharide (LPS) in sepsis. Activation of TLR4
by LPS increases the expression of chemokines IL-8 and CXCL10, which
recruit leukocytes and activated T-cells, respectively. This study
was designed to determine whether cobalt induces a similar inflammatory
response to LPS by promoting the expression of IL-8 and CXCL10.
A human monocytic cell line, derived from acute monocytic leukaemia,
was treated with cobalt ions and expression of IL-8 and CXCL10 measured at
mRNA and protein levels. Cobalt-treated macrophages showed a 60-fold
increase in IL-8 mRNA, and an eightfold increase in production of
the mature chemokine (both p <
0.001); expression of the CXCL10
gene and protein was also significantly increased by cobalt (both
p <
0.001). Experiments were also performed in the presence of
CLI-095, a TLR4-specific antagonist which abrogated the cobalt-mediated
increase in IL-8 and CXCL10 expression. These findings suggest that cobalt ions induce inflammation similar
to that observed during sepsis by the simultaneous activation of
two TLR4-mediated signalling pathways. These pathways result in
increased production of IL-8 and CXCL10, and may be implicated in
pseudotumour formation following metal-on-metal replacement. Cite this article:
Wear debris released from bearing surfaces has been shown to
provoke negative immune responses in the recipient. Excessive wear
has been linked to early failure of prostheses. Analysis using coordinate
measuring machines (CMMs) can provide estimates of total volumetric
material loss of explanted prostheses and can help to understand
device failure. The accuracy of volumetric testing has been debated,
with some investigators stating that only protocols involving hundreds
of thousands of measurement points are sufficient. We looked to
examine this assumption and to apply the findings to the clinical
arena. We examined the effects on the calculated material loss from
a ceramic femoral head when different CMM scanning parameters were
used. Calculated wear volumes were compared with gold standard gravimetric
tests in a blinded study. Objectives
Methods
We describe a cohort of patients with a high rate of mid-term failure following Kinemax Plus total knee replacement inserted between 1998 and 2001. This implant has been recorded as having a survival rate of 96% at ten years. However, in our series the survival rate was 75% at nine years. This was also significantly lower than that of subsequent consecutive series of PFC Sigma knee replacements performed by the same surgeon. No differences were found in the clinical and radiological parameters between the two groups. At revision the most striking finding was polyethylene wear. An independent analysis of the polyethylene components was therefore undertaken. Scanning electron microscopy revealed type 2 fusion defects in the ultra-high molecular weight polyethylene (UHMWPE), which indicated incomplete boundary fusion. Other abnormalities consistent with weak UHMWPE particle interface strength were present in both the explanted inserts and in unused inserts from the same period. We consider that these type 2 fusion defects are the cause of the early failure of the Kinemax implants. This may represent a manufacturing defect resulting in a form of programmed polyethylene failure.
