The aims of this piece of work were to: 1) record the background
concentrations of blood chromium (Cr) and cobalt (Co) concentrations
in a large group of subjects; 2) to compare blood/serum Cr and Co
concentrations with retrieved metal-on-metal (MoM) hip resurfacings;
3) to examine the distribution of Co and Cr in the serum and whole
blood of patients with MoM hip arthroplasties; and 4) to further
understand the partitioning of metal ions between the serum and
whole blood fractions. A total of 3042 blood samples donated to the local transfusion
centre were analysed to record Co and Cr concentrations. Also, 91
hip resurfacing devices from patients who had given pre-revision
blood/serum samples for metal ion analysis underwent volumetric
wear assessment using a coordinate measuring machine. Linear regression analysis
was carried out and receiver operating characteristic curves were
constructed to assess the reliability of metal ions to identify
abnormally wearing implants. The relationship between serum and
whole blood concentrations of Cr and Co in 1048 patients was analysed
using Bland-Altman charts. This relationship was further investigated
in an Objectives
Methods
The aims of this study were to compare the diagnostic test characteristics
of ultrasound alone, metal artefact reduction sequence MRI (MARS-MRI)
alone, and ultrasound combined with MARS-MRI for identifying intra-operative
pseudotumours in metal-on-metal hip resurfacing (MoMHR) patients
undergoing revision surgery. This retrospective diagnostic accuracy study involved 39 patients
(40 MoMHRs). The time between imaging modalities was a mean of 14.6
days (0 to 90), with imaging performed at a mean of 5.3 months (0.06
to 12) before revision. The prevalence of intra-operative pseudotumours
was 82.5% (n = 33).Aims
Methods
Despite the worldwide usage of the cemented Contemporary
acetabular component (Stryker), no published data are available
regarding its use in patients aged <
50 years. We undertook a
mid- to long-term follow-up study, including all consecutive patients
aged
<
50 years who underwent a primary total hip replacement using
the Contemporary acetabular component with the Exeter cemented stem
between January 1999 and January 2006. There were 152 hips in 126
patients, 61 men and 65 women, mean age at surgery 37.6 years (16
to 49 yrs). One patient was lost to follow-up. Mean clinical follow-up of all implants was 7.6 years (0.9 to
12.0). All clinical questionnaire scores, including Harris hip score,
Oxford hip score and several visual analogue scales, were found
to have improved. The eight year survivorship of all acetabular
components for the endpoints revision for any reason or revision
for aseptic loosening was 94.4% (95% confidence interval (CI) 89.2
to 97.2) and 96.4% (95% CI 91.6 to 98.5), respectively. Radiological follow-up
was complete for 146 implants. The eight year survival for the endpoint
radiological loosening was 93.1% (95% CI 86.2 to 96.6). Three surviving
implants were considered radiologically loose but were asymptomatic.
The presence of acetabular osteolysis (n = 17, 11.8%) and radiolucent
lines (n = 20, 13.9%) in the 144 surviving cups indicates a need
for continued observation in the second decade of follow-up in order
to observe their influence on long-term survival. The clinical and radiological data resulting in a ten-year survival
rate >
90% in young patients support the use of the Contemporary
acetabular component in this specific patient group. Cite this article:
The purpose of this study was twofold: first,
to determine whether the five-year results of hip resurfacing arthroplasty
(HRA) in Canada justified the continued use of HRA; and second,
to identify whether greater refinement of patient selection was
warranted. This was a retrospective cohort study that involved a review
of 2773 HRAs performed between January 2001 and December 2008 at
11 Canadian centres. Cox’s proportional hazards models were used
to analyse the predictors of failure of HRA. Kaplan–Meier survival
analysis was performed to predict the cumulative survival rate at
five years. The factors analysed included age, gender, body mass
index, pre-operative hip pathology, surgeon’s experience, surgical
approach, implant sizes and implant types. The most common modes
of failure were also analysed. The 2773 HRAs were undertaken in 2450 patients: 2127 in men and
646 in women. The mean age at operation was 50.5 years ( The failure rates of HRA at five years justify the ongoing use
of this technique in men. Female gender is an independent predictor
of failure, and a higher failure rate at five years in women leads
the authors to recommend this technique only in exceptional circumstances
for women. Cite this article:
Fracture of the neck of the femur after resurfacing arthroplasty usually leads to failure and conversion to a total hip replacement. We describe an intracapsular fracture of the femoral neck sustained after hip resurfacing which was treated by cannulated screws, resulting in union and retention of the resurfacing implant. The result at follow-up three years later was very satisfactory with a Harris hip score of 99.
The aim of this study was to evaluate the ten-year
clinical and functional outcome of hip resurfacing and to compare it
with that of cementless hip arthroplasty in patients under the age
of 55 years. Between 1999 and 2002, 80 patients were enrolled into the study:
24 were randomised (11 to hip resurfacing, 13 to total hip arthroplasty),
18 refused hip resurfacing and chose cementless total hip arthroplasty
with a 32 mm bearing, and 38 insisted on resurfacing. The mean follow-up
for all patients was 12.1 years (10 to 14). Patients were assessed clinically and radiologically at one year,
five years and ten years. Outcome measures included EuroQol EQ5D,
Oxford, Harris hip, University of California Los Angeles and University
College Hospital functional scores. No differences were seen between the two groups in the Oxford
or Harris hip scores or in the quality of life scores. Despite a
similar aspiration to activity pre-operatively, a higher proportion
of patients with a hip resurfacing were running and involved in
sport and heavy manual labour after ten years. We found significantly higher function scores in patients who
had undergone hip resurfacing than in those with a cementless hip
arthroplasty at ten years. This suggests a functional advantage
for hip resurfacing. There were no other attendant problems. Cite this article:
We retrospectively analysed concentrations of chromium and cobalt ions in samples of synovial fluid and whole blood taken from a group of 92 patients with failed current-generation metal-on-metal hip replacements. We applied acid oxidative digestion to our trace metal analysis protocol, which found significantly higher levels of metal ion concentrations in blood and synovial fluid than a non-digestive method. Patients were subcategorised by mode of failure as either ‘unexplained pain’ or ‘defined causes’. Using this classification, chromium and cobalt ion levels were present over a wider range in synovial fluid and not as strongly correlated with blood ion levels as previously reported. There was no significant difference between metal ion concentrations and manufacturer of the implant, nor femoral head size below or above 50 mm. There was a moderately positive correlation between metal ion levels and acetabular component inclination angle as measured on three-dimensional CT imaging. Our results suggest that acid digestion of samples of synovial fluid samples is necessary to determine metal ion concentrations accurately so that meaningful comparisons can be made between studies.
Pseudotumours are a rare complication of hip resurfacing. They are thought to be a response to metal debris which may be caused by edge loading due to poor orientation of the acetabular component. Our aim was to determine the optimal acetabular orientation to minimise the risk of pseudotumour formation. We matched 31 hip resurfacings revised for pseudotumour formation with 58 controls who had a satisfactory outcome from this procedure. The radiographic inclination and anteversion angles of the acetabular component were measured on anteroposterior radiographs of the pelvis using Einzel-Bild-Roentgen-Analyse software. The mean inclination angle (47°, 10° to 81°) and anteversion angle (14°, 4° to 34°) of the pseudotumour cases were the same (p = 0.8, p = 0.2) as the controls, 46° (29° to 60°) and 16° (4° to 30°) respectively, but the variation was greater. Assuming an accuracy of implantation of ± 10° about a target position, the optimal radiographic position was found to be approximately 45° of inclination and 20° of anteversion. The incidence of pseudotumours inside the zone was four times lower (p = 0.007) than outside the zone. In order to minimise the risk of pseudotumour formation we recommend that surgeons implant the acetabular component at an inclination of 45° (± 10) and anteversion of 20° (± 10) on post-operative radiographs. Because of differences between the radiographic and the operative angles, this may be best achieved by aiming for an inclination of 40° and an anteversion of 25°.
Pseudotumours (abnormal peri-prosthetic soft-tissue reactions)
following metal-on-metal hip resurfacing arthroplasty (MoMHRA) have
been associated with elevated metal ion levels, suggesting that
excessive wear may occur due to edge-loading of these MoM implants.
This study aimed to quantify The duration and magnitude of edge-loading Objectives
Methods
This review examines the future of total hip arthroplasty, aiming to avoid past mistakes
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:
The aim of this study was to evaluate the functional
and oncological outcome of extracorporeally irradiated autografts
used to reconstruct the pelvis after a P1/2 internal hemipelvectomy. The study included 18 patients with a primary malignant bone
tumour of the pelvis. There were 13 males and five females with
a mean age of 24.8 years (8 to 62). Of these, seven had an osteogenic
sarcoma, six a Ewing’s sarcoma, and five a chondrosarcoma. At a
mean follow-up of 51.6 months (4 to 185), nine patients had died
with metastatic disease while nine were free from disease. Local
recurrence occurred in three patients all of whom eventually died of
their disease. Deep infection occurred in three patients and required
removal of their graft in two while the third underwent a hindquarter
amputation for extensive flap necrosis. The mean Musculoskeletal Tumor Society functional score of the
16 patients who could be followed-up for at least 12 months was
77% (50 to 90). Those 15 patients who completed the Toronto Extremity
Salvage Score questionnaire had a mean score of 71% (53 to 85). Extracorporeal irradiation and re-implantation of bone is a valid
method of reconstruction after an internal hemipelvectomy. It has
an acceptable morbidity and a functional outcome that compares favourably
with other available reconstructive techniques. Cite this article:
Blood metal ions have been widely used to investigate
metal-on-metal hip replacements, but their ability to discriminate
between well-functioning and failed hips is not known. The Medicines
and Healthcare products Regulatory Agency (MHRA) has suggested a
cut-off level of 7 parts per billion (ppb). We performed a pair-matched, case-control study to investigate
the sensitivity and specificity of blood metal ion levels for diagnosing
failure in 176 patients with a unilateral metal-on-metal hip replacement.
We recruited 88 cases with a pre-revision, unexplained failed hip
and an equal number of matching controls with a well-functioning
hip. We investigated the 7 ppb cut-off level for the maximum of
cobalt or chromium and determined optimal mathematical cut-off levels
from receiver-operating characteristic curves. The 7 ppb cut-off level for the maximum of cobalt or chromium
had a specificity of 89% and sensitivity 52% for detecting a pre-operative
unexplained failed metal on metal hip replacement. The optimal cut-off
level for the maximum of cobalt or chromium was 4.97 ppb and had
sensitivity 63% and specificity 86%. Blood metal ions had good discriminant ability to separate failed
from well-functioning hip replacements. The MHRA cut-off level of
7 ppb provides a specific test but has poor sensitivity.
We report a retrospective review of the incidence of venous thromboembolism in 463 consecutive patients who underwent primary total hip arthroplasty (487 procedures). Treatment included both total hip replacement and hip resurfacing, and the patients were managed without anticoagulants. The thromboprophylaxis regimen included an antiplatelet agent, generally aspirin, hypotensive epidural anaesthesia, elastic compression stockings and early mobilisation. In 258 of these procedures (244 patients) performed in 2005 (cohort A) mechanical compression devices were not used, whereas in 229 (219 patients) performed during 2006 (cohort B) bilateral intermittent pneumatic calf compression was used. All operations were performed through a posterior mini-incision approach. Patients who required anticoagulation for pre-existing medical problems and those undergoing revision arthroplasty were excluded. Doppler ultrasonographic screening for deep-vein thrombosis was performed in all patients between the fourth and sixth post-operative days. All patients were reviewed at a follow-up clinic six to ten weeks after the operation. In addition, reponse to a questionnaire was obtained at the end of 12 weeks post-operatively. No symptomatic calf or above-knee deep-vein thrombosis or pulmonary embolism occurred. In 25 patients in cohort A (10.2%) and in ten patients in cohort B (4.6%) asymptomatic calf deep-vein thromboses were detected ultrasonographically. This difference was statistically significant (p = 0.03). The regimen followed by cohort B offers the prospect of a low incidence of venous thromboembolism without subjecting patients to the higher risk of bleeding associated with anticoagulant use.
Lately, concerns have arisen following the use of large metal-on-metal bearings in hip replacements owing to reports of catastrophic soft-tissue reactions resulting in implant failure and associated complications. This review examines the literature and contemporary presentations on current clinical dilemmas in metal-on-metal hip replacement.
The presence of pseudotumours, which are soft-tissue masses relating to the hip, after metal-on-metal hip resurfacing arthroplasty has been associated with elevated levels of metal ions in serum, suggesting that pseudotumours occur when there is increased wear. We aimed to quantify the wear in vivo of implants revised for pseudotumours (eight) and of a control group of implants (22) revised for other reasons of failure. We found that the implant group with pseudotumours had a significantly higher rate of median linear wear of the femoral component at 8.1 μm/year (2.75 to 25.4) than the 1.79 μm/year (0.82 to 4.15; p = 0.002) of the non-pseudotumour group. For the acetabular component a significantly higher rate of median linear wear of 7.36 μm/year (1.61 to 24.9) was observed in the pseudotumour group compared with 1.28 μm/year (0.81 to 3.33, p = 0.001) in the other group. Wear of the acetabular component in the pseudotumour group always involved the edge of the implant, indicating that edge-loading had occurred. Our findings are the first direct evidence that pseudotumour is associated with increased wear at the metal-on-metal articulation. Furthermore, edge-loading with the loss of fluid-film lubrication may be an important mechanism of generation of wear in patients with a pseudotumour.
We report the clinical and radiological outcomes
of a series of contemporary cementless ceramic-on-ceramic total hip
replacements (THRs) at ten years in patients aged ≤ 55 years of
age. Pre- and post-operative activity levels are described. A total
of 120 consecutive ceramic cementless THRs were performed at a single
centre in 110 patients from 1997 to 1999. The mean age of the patients
at operation was 45 years (20 to 55). At ten years, four patients
had died and six were lost to follow-up, comprising ten hips. The
mean post-operative Harris hip score was 94.7 (55 to 100). Radiological
analysis was undertaken in 90 available THRs of the surviving 106
hips at final review: all had evidence of stable bony ingrowth,
with no cases of osteolysis. Wear was undetectable. There were four
revisions. The survival for both components with revision for any
cause as an endpoint was 96.5% (95% confidence interval 94.5 to
98.7). The mean modified University of California, Los Angeles activity
level rose from a mean of 6.4 (4 to 10) pre-operatively to 9.0 (6
to 10) at the ten-year post-operative period. Alumina ceramic-on-ceramic bearings in cementless primary THR
in this series have resulted in good clinical and radiological outcomes
with undetectable rates of wear and excellent function in the demanding
younger patient group at ten years. Cite this article:
We report 17 patients (20 hips) in whom metal-on-metal resurfacing had been performed and who presented with various symptoms and a soft-tissue mass which we termed a pseudotumour. Each patient underwent plain radiography and in some, CT, MRI and ultrasonography were also performed. In addition, histological examination of available samples was undertaken. All the patients were women and their presentation was variable. The most common symptom was discomfort in the region of the hip. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. To date, 13 of the 20 hips have required revision to a conventional hip replacement. Two are awaiting revision. We estimate that approximately 1% of patients who have a metal-on-metal resurfacing develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. We are concerned that with time the incidence of these pseudotumours may increase. Further investigation is required to define their cause.