Metal-on-metal hip resurfacing (MoM-HR) has seen decreased usage due to safety and longevity concerns. Joint registries have highlighted the risks in females, smaller hips, and hip dysplasia. This study aimed to identify if reported risk factors are linked to revision in a long-term follow-up of MoM-HR performed by a non-designer surgeon. A retrospective review of consecutive MoM hip arthroplasties (MoM-HRAs) using Birmingham Hip Resurfacing was conducted. Data on procedure side, indication, implant sizes and orientation, highest blood cobalt and chromium ion concentrations, and all-cause revision were collected from local and UK National Joint Registry records.Aims
Methods
The primary outcome was investigating differences in wear, as measured by femoral head penetration, between cross-linked vitamin E-diffused polyethylene (vE-PE) and cross-linked polyethylene (XLPE) acetabular component liners and between 32 and 36 mm head sizes at the ten-year follow-up. Secondary outcomes included acetabular component migration and patient-reported outcome measures (PROMs) such as the EuroQol five-dimension questionnaire, 36-Item Short-Form Health Survey, Harris Hip Score, and University of California, Los Angeles Activity Scale (UCLA). A single-blinded, multi-arm, 2 × 2 factorial randomized controlled trial was undertaken. Patients were recruited between May 2009 and April 2011. Radiostereometric analyses (RSAs) were performed from baseline to ten years. Of the 220 eligible patients, 116 underwent randomization, and 82 remained at the ten-year follow-up. Eligible patients were randomized into one of four interventions: vE-PE acetabular liner with either 32 or 36 mm femoral head, and XLPE acetabular liner with either 32 or 36 mm femoral head. Parameters were otherwise identical except for acetabular liner material and femoral head size.Aims
Methods
The aims of this study were to determine if an increasing serum cobalt (Co) and/or chromium (Cr) concentration is correlated with a decreasing Harris Hip Score (HHS) and Hip disability and Osteoarthritis Outcome Score (HOOS) in patients who received the Articular Surface Replacement (ASR) hip resurfacing arthroplasty (HRA), and to evaluate the ten-year revision rate and show if sex, inclination angle, and Co level influenced the revision rate. A total of 62 patients with an ASR-HRA were included and monitored yearly postoperatively. At follow-up, serum Co and Cr levels were measured and the HHS and the HOOS were scored. In addition, preoperative patient and implant variables and the need for revision surgery were recorded. We used a linear mixed model to relate the serum Co and Cr levels to different patient-reported outcome measures (PROMs). For the survival analyses we used the Kaplan-Meier and Cox regression model.Aims
Methods
To establish the survivorship, function, and metal ion levels in an unselected series of metal-on-metal hip resurfacing arthroplasties (HRAs) performed by a non-designer surgeon. We reviewed 105 consecutive HRAs in 83 patients, performed by a single surgeon, at a mean follow-up of 14.9 years (9.3 to 19.1). The cohort included 45 male and 38 female patients, with a mean age of 49.5 years (SD 12.5)Aims
Methods
The aim of this study was to evaluate the accuracy of implant placement when using robotic assistance during total hip arthroplasty (THA). A total of 20 patients underwent a planned THA using preoperative CT scans and robotic-assisted software. There were nine men and 11 women (n = 20 hips) with a mean age of 60.8 years (Aims
Patients and Methods
We present the ten-year data of a cohort of patients, aged between
18 and 65 years (mean age 52.7 years; 19 to 64), who underwent total
hip arthroplasty. Patients were randomised to be treated with a
cobalt-chrome (CoCr) femoral head with an ultra-high molecular weight
polyethylene (UHMWPE), highly cross-linked polyethylene (XLPE) or
ceramic-on-ceramic (CoC) bearing surface. A total of 102 hips (91 patients) were randomised into the three
groups. At ten years, 97 hips were available for radiological and
functional follow-up. Two hips (two patients) had been revised (one
with deep infection and one for periprosthetic fracture) and three
were lost to follow-up. Radiological analysis was performed using
a validated digital assessment programme to give linear, directional
and volumetric wear of the two polyethylene groups.Aims
Patients and Methods
The high revision rates of the DePuy Articular Surface Replacement (ASR) and the DePuy ASR XL (the total hip arthroplasty (THA) version) have led to questions over the viability of metal-on-metal (MoM) hip joints. Some designs of MoM hip joint do, however, have reasonable mid-term performance when implanted in appropriate patients. Investigations into the reasons for implant failure are important to offer help with the choice of implants and direction for future implant designs. One way to assess the performance of explanted hip prostheses is to measure the wear (in terms of material loss) on the joint surfaces. In this study, a coordinate measuring machine (CMM) was used to measure the wear on five failed cementless Biomet Magnum/ReCap/ Taperloc large head MoM THAs, along with one Biomet ReCap resurfacing joint. Surface roughness measurements were also taken. The reason for revision of these implants was pain and/or adverse reaction to metal debris (ARMD) and/or elevated blood metal ion levels.Objectives
Methods
One goal of total hip arthroplasty is to restore normal hip anatomy.
The aim of this study was to compare displacement of the centre
of rotation (COR) using a standard reaming technique with a technique
in which the acetabulum was reamed immediately peripherally and
referenced off the rim. In the first cohort the acetabulum was reamed to the floor followed
by sequentially larger reamers. In the second cohort the acetabulum
was only reamed peripherally, starting with a reamer the same size
as the native femoral head. Anteroposterior pelvic radiographs were
analysed for acetabular floor depth and vertical and horizontal position
of the COR.Aims
Patients and Methods
In order to prevent dislocation of the hip after total hip arthroplasty
(THA), patients have to adhere to precautions in the early post-operative
period. The hypothesis of this study was that a protocol with minimal
precautions after primary THA using the posterolateral approach
would not increase the short-term (less than three months) risk
of dislocation. We prospectively monitored a group of unselected patients undergoing
primary THA managed with standard precautions (n = 109, median age
68.9 years; interquartile range (IQR) 61.2 to 77.3) and a group
who were managed with fewer precautions (n = 108, median age 67.2
years; IQR 59.8 to 73.2). There were no significant differences between
the groups in relation to predisposing risk factors. The diameter
of the femoral head ranged from 28 mm to 36 mm; meticulous soft-tissue
repair was undertaken in all patients. The medical records were
reviewed and all patients were contacted three months post-operatively
to confirm whether they had experienced a dislocation. Aims
Patients and Methods
Large-head metal-on-metal (MoM) total hip replacements
(THR) have given rise to concern. Comparative studies of small-head
MoM THRs over a longer follow-up period are lacking. Our objective
was to compare the incidence of complications such as infection,
dislocation, revision, adverse local tissue reactions, mortality
and radiological and clinical outcomes in small-head (28 mm) MoM
and ceramic-on-polyethylene (CoP) THRs up to 12 years post-operatively. A prospective cohort study included 3341 THRs in 2714 patients.
The mean age was 69.1 years (range 24 to 98) and 1848 (55.3%) were
performed in women, with a mean follow-up of 115 months (18 to 201).
There were 883 MoM and 2458 CoP bearings. Crude incidence rates
(cases/1000 person-years) were: infection 1.3 In conclusion, we found similar results for small-head MoM and
CoP bearings up to ten years post-operatively, but after ten years
MoM THRs had a higher risk of all-cause revision. Furthermore, the
presence of an adverse response to metal debris seen in the small-head
MOM group at revision is a cause for concern. Cite this article:
The issues surrounding raised levels of metal
ions in the blood following large head metal-on-metal total hip replacement
(THR), such as cobalt and chromium, have been well documented. Despite
the national popularity of uncemented metal-on-polyethylene (MoP)
THR using a large-diameter femoral head, few papers have reported
the levels of metal ions in the blood following this combination.
Following an isolated failure of a 44 mm Trident–Accolade uncemented
THR associated with severe wear between the femoral head and the
trunnion in the presence of markedly elevated levels of cobalt ions
in the blood, we investigated the relationship between modular femoral head
diameter and the levels of cobalt and chromium ions in the blood
following this THR. A total of 69 patients received an uncemented Trident–Accolade
MoP THR in 2009. Of these, 43 patients (23 men and 20 women, mean
age 67.0 years) were recruited and had levels of cobalt and chromium
ions in the blood measured between May and June 2012. The patients
were then divided into three groups according to the diameter of
the femoral head used: 12 patients in the 28 mm group (controls),
18 patients in the 36 mm group and 13 patients in the 40 mm group.
A total of four patients had identical bilateral prostheses in situ
at phlebotomy: one each in the 28 mm and 36 mm groups and two in
the 40 mm group. There was a significant increase in the mean levels of cobalt
ions in the blood in those with a 36 mm diameter femoral head compared
with those with a 28 mm diameter head (p = 0.013). The levels of
cobalt ions in the blood were raised in those with a 40 mm diameter
head but there was no statistically significant difference between
this group and the control group (p = 0.152). The levels of chromium
ions in the blood were normal in all patients. The clinical significance of this finding is unclear, but we
have stopped using femoral heads with a diameter of ≤ 36 mm, and
await further larger studies to clarify whether, for instance, this
issue particularly affects this combination of components. Cite this article:
A retrospective study was conducted to investigate
the changes in metal ion levels in a consecutive series of Birmingham
Hip Resurfacings (BHRs) at a minimum ten-year follow-up. We reviewed
250 BHRs implanted in 232 patients between 1998 and 2001. Implant
survival, clinical outcome (Harris hip score), radiographs and serum chromium
(Cr) and cobalt (Co) ion levels were assessed. Of 232 patients, 18 were dead (five bilateral BHRs), 15 lost
to follow-up and ten had been revised. The remaining 202 BHRs in
190 patients (136 men and 54 women; mean age at surgery 50.5 years
(17 to 76)) were evaluated at a minimum follow-up of ten years (mean
10.8 years (10 to 13.6)). The overall implant survival at 13.2 years
was 92.4% (95% confidence interval 90.8 to 94.0). The mean Harris
hip score was 97.7 (median 100; 65 to 100). Median and mean ion
levels were low for unilateral resurfacings (Cr: median 1.3 µg/l,
mean
1.95 µg/l (<
0.5 to 16.2); Co: median 1.0 µg/l, mean 1.62 µg/l
(<
0.5 to 17.3)) and bilateral resurfacings (Cr: median 3.2 µg/l,
mean 3.46 µg/l (<
0.5 to 10.0); Co: median 2.3 µg/l, mean 2.66
µg/l (<
0.5 to 9.5)). In 80 unilateral BHRs with sequential ion
measurements, Cr and Co levels were found to decrease significantly
(p <
0.001) from the initial assessment at a median of six years
(4 to 8) to the last assessment at a median of 11 years (9 to 13),
with a mean reduction of 1.24 µg/l for Cr and 0.88 µg/l for Co.
Three female patients had a >
2.5 µg/l increase of Co ions, associated with
head sizes ≤ 50 mm, clinical symptoms and osteolysis. Overall, there
was no significant difference in change of ion levels between genders
(Cr, p = 0.845; Co, p = 0.310) or component sizes (Cr, p = 0.505;
Co, p = 0.370). Higher
Orientation of the acetabular component influences
wear, range of movement and the incidence of dislocation after total
hip replacement (THR). During surgery, such orientation is often
referenced to the anterior pelvic plane (APP), but APP inclination
relative to the coronal plane (pelvic tilt) varies substantially
between individuals. In contrast, the change in pelvic tilt from
supine to standing (dPT) is small for nearly all individuals. Therefore,
in THR performed with the patient supine and the patient’s coronal
plane parallel to the operating table, we propose that freehand placement
of the acetabular component placement is reliable and reflects standing
(functional) cup position. We examined this hypothesis in 56 hips
in 56 patients (19 men) with a mean age of 61 years (29 to 80) using
three-dimensional CT pelvic reconstructions and standing lateral
pelvic radiographs. We found a low variability of acetabular component
placement, with 46 implants (82%) placed within a combined range
of 30° to 50° inclination and 5° to 25° anteversion. Changing from
the supine to the standing position (analysed in 47 patients) was associated
with an anteversion change <
10° in 45 patients (96%). dPT was
<
10° in 41 patients (87%). In conclusion, supine THR appears
to provide reliable freehand acetabular component placement. In
most patients a small reclination of the pelvis going from supine
to standing causes a small increase in anteversion of the acetabular component Cite this article:
Peri-articular soft-tissue masses or ‘pseudotumours’
can occur after large-diameter metal-on-metal (MoM) resurfacing
of the hip and conventional total hip replacement (THR). Our aim
was to assess the incidence of pseudotumour formation and to identify
risk factors for their formation in a prospective cohort study. A total of 119 patients who underwent 120 MoM THRs with large-diameter
femoral heads between January 2005 and November 2007 were included
in the study. Outcome scores, serum metal ion levels, radiographs
and CT scans were obtained. Patients with symptoms or an identified
pseudotumour were offered MRI and an ultrasound-guided biopsy. There were 108 patients (109 hips) eligible for evaluation by
CT scan at a mean follow-up of 3.6 years (2.5 to 4.5); 42 patients
(39%) were diagnosed with a pseudotumour. The hips of 13 patients
(12%) were revised to a polyethylene acetabular component with small-diameter
metal head. Patients with elevated serum metal ion levels had a
four times increased risk of developing a pseudotumour. This study shows a substantially higher incidence of pseudotumour
formation and subsequent revisions in patients with MoM THRs than
previously reported. Because most revision cases were identified
only after an intensive screening protocol, we recommend close monitoring
of patients with MoM THR.
We report the findings of an independent review
of 230 consecutive Birmingham hip resurfacings (BHRs) in 213 patients
(230 hips) at a mean follow-up of 10.4 years (9.6 to 11.7). A total
of 11 hips underwent revision; six patients (six hips) died from
unrelated causes; and 13 patients (16 hips) were lost to follow-up.
The survival rate for the whole cohort was 94.5% (95% confidence
interval (CI) 90.1 to 96.9). The survival rate in women was 89.1%
(95% CI 79.2 to 94.4) and in men was 97.5% (95% CI 92.4 to 99.2).
Women were 1.4 times more likely to suffer failure than men. For
each millimetre increase in component size there was a 19% lower
chance of a failure. The mean Oxford hip score was 45.0 (median
47.0, 28 to 48); mean University of California, Los Angeles activity
score was 7.4 (median 8.0, 3 to 9); mean patient satisfaction score
was 1.4 (median 1.0, 0 to 9). A total of eight hips had lysis in
the femoral neck and two hips had acetabular lysis. One hip had
progressive radiological changes around the peg of the femoral component.
There was no evidence of progressive neck narrowing between five
and ten years. Our results confirm that BHR provides good functional outcome
and durability for men, at a mean follow-up of ten years. We are
now reluctant to undertake hip resurfacing in women with this implant.
In this prospective study we studied the effect
of the inclination angle of the acetabular component on polyethylene wear
and component migration in cemented acetabular sockets using radiostereometric
analysis. A total of 120 patients received either a cemented Reflection
All-Poly ultra-high-molecular-weight polyethylene or a cemented
Reflection All-Poly highly cross-linked polyethylene acetabular
component, combined with either cobalt–chrome or Oxinium femoral
heads. Femoral head penetration and migration of the acetabular
component were assessed with repeated radiostereometric analysis
for two years. The inclination angle was measured on a standard
post-operative anteroposterior pelvic radiograph. Linear regression
analysis was used to determine the relationship between the inclination
angle and femoral head penetration and migration of the acetabular component. We found no relationship between the inclination angle and penetration
of the femoral head at two years’ follow-up (p = 0.9). Similarly,
our data failed to reveal any statistically significant correlation
between inclination angle and migration of these cemented acetabular
components (p = 0.07 to p = 0.9).
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 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
