Aims. 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
Hip resurfacing remains a potentially valuable surgical procedure for appropriately-selected patients with optimised implant choices. However, concern regarding high early failure rates continues to undermine confidence in use. A large contributor to failure is adverse local tissue reactions around metal-on-metal (MoM) bearing surfaces. Such phenomena have been well-explored around MoM total hip arthroplasties, but comparable data in equivalent hip resurfacing procedures is lacking. In order to define genetic predisposition, we performed a case-control study investigating the role of human leucocyte antigen (HLA) genotype in the development of pseudotumours around MoM hip resurfacings. A matched case-control study was performed using the prospectively-collected database at the host institution. In all, 16 MoM hip resurfacing 'cases' were identified as having symptomatic periprosthetic pseudotumours on preoperative metal artefact reduction sequence (MARS) MRI, and were subsequently histologically confirmed as high-grade aseptic lymphocyte-dominated vasculitis-associated lesions (ALVALs) at revision surgery. ‘Controls’ were matched by implant type in the absence of evidence of pseudotumour. Blood samples from all cases and controls were collected prospectively for high resolution genetic a nalysis targeting 11 separate HLA loci. Statistical significance was set at 0.10 a priori to determine the association between HLA genotype and pseudotumour formation, given the small sample size.Aims
Methods
This annotation reviews current concepts on the three most common surgical approaches used for proximal interphalangeal joint arthroplasty: dorsal, volar, and lateral. Advantages and disadvantages of each are highlighted, and the outcomes are discussed. Cite this article:
To find out if there is an inverse association between estimated glomerular filtration rate (eGFR) and whole blood cobalt (Co) and chromium (Cr) levels in patients with metal-on-metal (MoM) hip arthroplasties and renal insufficiency, suggesting that renal insufficiency could cause accumulation of Co and Cr in blood. Out of 2,520 patients with 3,013 MoM hip arthroplasties, we identified 1,244 patients with whole blood Co, Cr, and creatinine measured within no more than a one-year interval. We analyzed the correlation of blood metal ion levels and eGFR to identify a potential trend of accumulating Co or Cr with decreasing eGFR.Aims
Methods
The optimum clearance between the bearing surfaces of hip arthroplasties is unknown. Theoretically, to minimize wear, it is understood that clearances must be low enough to maintain optimal contact pressure and fluid film lubrication, while being large enough to allow lubricant recovery and reduce contact patch size. This study aimed to identify the relationship between diametrical clearance and volumetric wear, through the analysis of retrieved components. A total of 81 metal-on-metal Pinnacle hips paired with 12/14 stems were included in this study. Geometrical analysis was performed on each component, using coordinate and roundness measuring machines. The relationship between their as-manufactured diametrical clearance and volumetric wear was investigated. The Mann-Whitney U test and unpaired Aims
Methods
Routine surveillance of primary hip and knee arthroplasties has traditionally been performed with office follow-up visits at one year postoperatively. The value of these visits is unclear. The present study aims to determine the utility and burden of routine clinical follow-up at one year after primary arthroplasty to patients and providers. All patients (473) who underwent primary total hip (280), hip resurfacing (eight), total knee (179), and unicompartmental knee arthroplasty (six) over a nine-month period at a single institution were identified from an institutional registry. Patients were prompted to attend their routine one-year postoperative visit by a single telephone reminder. Patients and surgeons were given questionnaires at the one-year postoperative visit, defined as a clinical encounter occurring at nine to 15 months from the date of surgery, regarding value of the visit.Aims
Methods
Total ankle arthroplasty (TAA) has become the most reliable surgical solution for patients with end-stage arthritis of the ankle. Aseptic loosening of the talar component is the most common complication. A custom-made artificial talus can be used as the talar component in a combined TAA for patients with poor bone stock of the talus. The purpose of this study was to investigate the functional and clinical outcomes of combined TAA. Ten patients (two men, eight women; ten ankles) treated using a combined TAA between 2009 and 2013 were matched for age, gender, and length of follow-up with 12 patients (one man, 11 women; 12 ankles) who underwent a standard TAA. All had end-stage arthritis of the ankle. The combined TAA features a tibial component of the TNK ankle (Kyocera, Kyoto, Japan) and an alumina ceramic artificial talus (Kyocera), designed using individualized CT data. The mean age at the time of surgery in the combined TAA and standard TAA groups was 71 years (Aims
Patients and Methods
We investigated the reliability of the cobalt-chromium (CoCr) synovial joint fluid ratio (JFR) in identifying the presence of a severe aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) response and/or suboptimal taper performance (SOTP) following metal-on-metal (MoM) hip arthroplasty. We then examined the possibility that the CoCr JFR may influence the serum partitioning of Co and Cr. For part A, we included all revision surgeries carried out at our unit with the relevant data, including volumetric wear analysis, joint fluid (JF) Co and Cr concentrations, and ALVAL grade (n = 315). Receiver operating characteristic curves were constructed to assess the reliability of the CoCr JFR in identifying severe ALVAL and/or SOTP. For part B, we included only patients with unilateral prostheses who had given matched serum and whole blood samples for Co and Cr analysis (n = 155). Multiple regression was used to examine the influence of JF concentrations on the serum partitioning of Co and Cr in the blood.Objectives
Methods
Aims.
This study presents the long-term survivorship, risk factors for prosthesis survival, and an assessment of the long-term effects of changes in surgical technique in a large series of patients treated by metal-on-metal (MoM) hip resurfacing arthroplasty (HRA). Between November 1996 and January 2012, 1074 patients (1321 hips) underwent HRA using the Conserve Plus Hip Resurfacing System. There were 787 men (73%) and 287 women (27%) with a mean age of 51 years (14 to 83). The underlying pathology was osteoarthritis (OA) in 1003 (75.9%), developmental dysplasia of the hip (DDH) in 136 (10.3%), avascular necrosis in 98 (7.4%), and other conditions, including inflammatory arthritis, in 84 (6.4%).Aims
Patients and Methods
The aim of this study was to describe temporal trends and survivorship of total hip arthroplasty (THA) in very young patients, aged ≤ 20 years. A descriptive observational study was undertaken using data from the National Joint Registry (NJR) for England, Wales, Northern Ireland and the Isle of Man between April 2003 and March 2017. All patients aged ≤ 20 years at the time of THA were included and the primary outcome was revision surgery. Descriptive statistics were used to summarize the data and Kaplan–Meier estimates calculated for the cumulative implant survival.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
Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted through the patient’s surrounding tissues. A commercially available impaction tool was modified to assemble components in the laboratory using impactor tips with varying stiffness at different applied energy levels. Springs were mounted below the modular components to represent the patient. The pull-off force of the head from the stem was measured to assess stability, and the displacement of the springs was measured to assess the force transmitted to the patient’s tissues.Objectives
Methods
The aim of this study was to determine whether patients with
metal-on-metal (MoM) arthroplasties of the hip have an increased
risk of cardiac failure compared with those with alternative types
of arthroplasties (non-MoM). A linkage study between the National Joint Registry, Hospital
Episodes Statistics and records of the Office for National Statistics
on deaths was undertaken. Patients who underwent elective total
hip arthroplasty between January 2003 and December 2014 with no
past history of cardiac failure were included and stratified as
having either a MoM (n = 53 529) or a non-MoM (n = 482 247) arthroplasty.
The primary outcome measure was the time to an admission to hospital
for cardiac failure or death. Analysis was carried out using data
from all patients and from those matched by propensity score.Aims
Patients and Methods
The MAGnetic Expansion Control (MAGEC) system
is used increasingly in the management of early-onset scoliosis.
Good results have been published, but there have been recent reports
identifying implant failures that may be associated with significant
metallosis surrounding the implants. This article aims to present
the current knowledge regarding the performance of this implant,
and the potential implications and strategies that may be employed
to identify and limit any problems. We urge surgeons to apply caution to patient and construct selection;
engage in prospective patient registration using a spine registry;
ensure close clinical monitoring until growth has ceased; and send
all explanted MAGEC rods for independent analysis. The MAGEC system may be a good instrumentation system for the
treatment of early-onset scoliosis. However, it is innovative and
like all new technology, especially when deployed in a paediatric
population, robust systems to assess long-term outcome are required
to ensure that patient safety is maintained. Cite this article:
Aims. Our first aim was to determine whether there are significant
changes in the level of metal ions in the blood at mid-term follow-up,
in patients with an Articular
Objectives. The high revision rates of the DePuy Articular
Our aim was to report survivorship data and lessons learned with
the Corail/Pinnacle cementless total hip arthroplasty (THA) system. Between August 2005 and March 2015, a total of 4802 primary cementless
Corail/Pinnacle THAs were performed in 4309 patients. In March 2016,
we reviewed these hips from a prospectively maintained database.Aims
Patients and Methods
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
High failure rates of metal-on-metal hip arthroplasty implants have highlighted the need for more careful introduction and monitoring of new implants and for the evaluation of the safety of medical devices. The National Joint Registry and other regulatory services are unable to detect failing implants at an early enough stage. We aimed to identify validated surrogate markers of long-term outcome in patients undergoing primary total hip arthroplasty (THA). We conducted a systematic review of studies evaluating surrogate markers for predicting long-term outcome in primary THA. Long-term outcome was defined as revision rate of an implant at ten years according to National Institute of Health and Care Excellence guidelines. We conducted a search of Medline and Embase (OVID) databases. Separate search strategies were devised for the Cochrane database and Google Scholar. Each search was performed to include articles from the date of their inception to June 8, 2015.Objectives
Methods
To assess the extent of osteointegration in two designs of shoulder
resurfacing implants. Bony integration to the Copeland cylindrical
central stem design and the Epoca RH conical-crown design were compared. Implants retrieved from six patients in each group were pair-matched.
Mean time to revision surgery of Copeland implants was 37 months
(standard deviation (Aims
Patients and Methods
Aims. This study investigated whether the use of tranexamic acid (TXA)
decreased blood loss and transfusion related cost following surface
replacement arthroplasty (SRA). . Methods. A retrospective review of patients treated with TXA during a
SRA, who did not receive autologous blood (TXA group) was performed.
Two comparison groups were established; the first group comprised
of patients who donated their own blood pre-operatively (auto group)
and the second of patients who did not donate blood pre-operatively
(control). Outcomes included transfusions, post-operative haemoglobin
(Hgb), complications, and length of post-operative stay. . Results. Between 2009 and 2013, 150 patients undergoing SRA were identified
for inclusion: 51 in the auto, 49 in the control, and 50 in the
TXA group. There were no differences in the pre-operative Hgb concentrations
between groups. The mean post-operative Hgb was 11.3 g/dL (9.1 to
13.6) in the auto and TXA groups, and 10.6 g/dL (8.1 to 12.1)in
the control group (p = 0.001). Accounting for cost of transfusions,
administration of TXA, and length of stay, the cost per patient
was $1731, $339, and $185 for the auto, control and TXA groups,
respectively. . Discussion. TXA use demonstrated higher post-operative Hgb concentrations
when compared with controls and decreased peri-operative costs. Take home message: Tranexamic acid safely limits allogeneic transfusion,
maintains post-operative haemoglobin, and decreases direct and indirect
transfusion related costs in
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
We present the results of 62 consecutive acetabular
revisions using impaction bone grafting and a cemented polyethylene
acetabular component in 58 patients (13 men and 45 women) after
a mean follow-up of 27 years (25 to 30). All patients were prospectively
followed. The mean age at revision was 59.2 years (23 to 82). We performed Kaplan–Meier (KM) analysis and also a Competing
Risk (CR) analysis because with long-term follow-up, the presence
of a competing event (i.e. death) prevents the occurrence of the
endpoint of re-revision. A total of 48 patients (52 hips) had died or had been re-revised
at final review in March 2011. None of the deaths were related to
the surgery. The mean Harris hip score of the ten surviving hips
in ten patients was 76 points (45 to 99). The KM survivorship at 25 years for the endpoint ‘re-revision
for any reason’ was 58.0% (95% confidence interval (CI) 38 to 73)
and for ‘re-revision for aseptic loosening’ 72.1% (95% CI 51 to
85). With the CR analysis we calculated the KM analysis overestimates
the failure rate with respectively 74% and 93% for these endpoints.
The current study shows that acetabular impaction bone grafting
revisions provide good clinical results at over 25 years. Cite this article:
Arthroplasty registries are important for the
surveillance of joint replacements and the evaluation of outcome. Independent
validation of registry data ensures high quality. The ability for
orthopaedic implant retrieval centres to validate registry data
is not known. We analysed data from the National Joint Registry
for England, Wales and Northern Ireland (NJR) for primary metal-on-metal
hip arthroplasties performed between 2003 and 2013. Records were
linked to the London Implant Retrieval Centre (RC) for validation.
A total of 67 045 procedures on the NJR and 782 revised pairs of
components from the RC were included. We were able to link 476 procedures
(60.9%) recorded with the RC to the NJR successfully. However, 306
procedures (39.1%) could not be linked. The outcome recorded by the
NJR (as either revised, unrevised or death) for a primary procedure
was incorrect in 79 linked cases (16.6%). The rate of registry-retrieval
linkage and correct assignment of outcome code improved over time.
The rates of error for component reference numbers on the NJR were
as follows: femoral head category number 14/229 (5.0%); femoral head
batch number 13/232 (5.3%); acetabular component category number
2/293 (0.7%) and acetabular component batch number 24/347 (6.5%). Registry-retrieval linkage provided a novel means for the validation
of data, particularly for component fields. This study suggests
that NJR reports may underestimate rates of revision for many types
of metal-on-metal hip replacement. This is topical given the increasing
scope for NJR data. We recommend a system for continuous independent
evaluation of the quality and validity of NJR data. Cite this article:
Metal-on-metal resurfacing of the hip (MoMHR)
has enjoyed a resurgence in the last decade, but is now again in question
as a routine option for osteoarthritis of the hip. Proponents of
hip resurfacing suggest that its survival is superior to that of
conventional hip replacement (THR), and that hip resurfacing is
less invasive, is easier to revise than THR, and provides superior
functional outcomes. Our argument serves to illustrate that none
of these proposed advantages have been realised and new and unanticipated
serious complications, such as pseudotumors, have been associated
with the procedure. As such, we feel that the routine use of MoMHR
is not justified. Cite this article:
Resurfacing of the humeral head is commonly used
within the UK to treat osteoarthritis (OA) of the shoulder. We present
the results of a small prospective randomised study of this procedure
using the Global CAP prosthesis with two different coatings, Porocoat
and DuoFix hydroxyapatite (HA). We followed two groups of ten patients
with OA of the shoulder for two years after insertion of the prosthesis
with tantalum marker beads, recording pain, Constant–Murley and
American Shoulder and Elbow Surgeons (ASES) outcome scores, and
using radiostereometric analysis to assess migration. The outcomes
were similar to those of other series, with significant reductions
in pain (p = 0.003) and an improvement in the Constant (p = 0.001)
and ASES scores (p = 0.006). The mean migration of the prosthesis
three months post-operatively was 0.78 mm (0.51 to 1.69) and 0.72
mm (0.33 to 1.45) for the Porocoat and DuoFix groups, respectively.
Analysis of variance indicated that the rate of migration reached
a plateau after three months post-operatively in both groups. At
follow-up of two years the mean migration was 1 mm ( The addition of a coating of HA to the sintered surface does
not improve fixation of this prosthesis. Cite this article:
Surface hip replacement (SHR) is generally used
in younger, active patients as an alternative conventional total
hip replacement in part because of the ability to preserve femoral
bone. This major benefit of
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:
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
We summarise and highlight the safety concerns
within the field of trauma and orthopaedic surgery with particular
emphasis placed on current controversies and reforms within the United
Kingdom National Health Service.
The December 2012 Wrist &
Hand Roundup360 looks at: the imaging of scaphoid fractures; splinting to help Dupuytren’s disease; quality of life after nerve transfers; early failure of Moje thumbs; electra CMCJ arthroplasty; proximal interphalangeal joint replacement; pronator quadratus repair in distal radius fractures; and osteoporosis and wrist fractures.
Since 1996 more than one million metal-on-metal
articulations have been implanted worldwide. Adverse reactions to
metal debris are escalating. Here we present an algorithmic approach
to patient management. The general approach to all arthroplasty
patients returning for follow-up begins with a detailed history,
querying for pain, discomfort or compromise of function. Symptomatic
patients should be evaluated for intra-articular and extra-articular
causes of pain. In large head MoM arthroplasty, aseptic loosening
may be the source of pain and is frequently difficult to diagnose.
Sepsis should be ruled out as a source of pain. Plain radiographs
are evaluated to rule out loosening and osteolysis, and assess component
position. Laboratory evaluation commences with erythrocyte sedimentation
rate and C-reactive protein, which may be elevated. Serum metal
ions should be assessed by an approved facility. Aspiration, with
manual cell count and culture/sensitivity should be performed, with
cloudy to creamy fluid with predominance of monocytes often indicative
of failure. Imaging should include ultrasound or metal artifact
reduction sequence MRI, specifically evaluating for fluid collections
and/or masses about the hip. If adverse reaction to metal debris
is suspected then revision to metal or ceramic-on-polyethylene is indicated
and can be successful. Delay may be associated with extensive soft-tissue
damage and hence poor clinical outcome.
We systematically reviewed all the evidence published
in the English language on proximal interphalangeal joint (PIPJ)
replacement, to determine its effectiveness on the function of the
hand and the associated post-operative complications. Original studies were selected if they reported clinical outcome
with a minimum of one year’s follow-up. Quality was assessed using
the Cowley systematic review criteria modified for finger-joint
replacements. Of 319 articles identified, only five were adequately
reported according to our quality criteria; there were no randomised
controlled trials. PIPJ replacements had a substantial effect size
on hand pain of -23.2 (95% confidence interval (CI) -27.3 to -19.1)
and grip strength 1.2 (95% CI -10.7 to 13.1), and a small effect
on range of movement 0.2 (95% CI -0.4 to 0.8). A dorsal approach
was most successful. Post-operative loosening occurred in 10% (95%
CI 3 to 30) of ceramic and 12.5% (95% CI 7 to 21) of pyrocarbon
replacements. Post-operative complications occurred in 27.8% (95%
CI 20 to 37). We conclude that the effectiveness of PIPJ replacement has not
been established. Small observational case studies and short-term
follow-up, together with insufficient reporting of patient data,
functional outcomes and complications, limit the value of current
evidence. We recommend that a defined core set of patients, surgical and
outcome data for this intervention be routinely and systematically
collected within the framework of a joint registry.
Radiostereometric analysis (RSA) can detect early
micromovement in unstable implant designs which are likely subsequently
to have a high failure rate. In 2010, the Articular Surface Replacement
(ASR) was withdrawn because of a high failure rate. In 19 ASR femoral
components, the mean micromovement over the first two years after implantation
was 0.107 mm ( We conclude that the ASR femoral component achieves initial stability
and that early migration is not the mode of failure for this resurfacing
arthroplasty.
Recent events have highlighted the importance
of implant design for survival and wear-related complications following
metal-on-metal hip resurfacing arthroplasty. The mid-term survival
of the most widely used implant, the Birmingham Hip Resurfacing
(BHR), has been described by its designers. The aim of this study
was to report the ten-year survival and patient-reported functional
outcome of the BHR from an independent centre. In this cohort of 554 patients (646 BHRs) with a mean age of
51.9 years (16.5 to 81.5) followed for a mean of eight years (1
to 12), the survival and patient-reported functional outcome depended
on gender and the size of the implant. In female hips (n = 267)
the ten-year survival was 74% (95% confidence interval (CI) 83 to
91), the ten-year revision rate for pseudotumour was 7%, the mean
Oxford hip score (OHS) was 43 ( This study supports the ongoing use of resurfacing in young active
men, who are a subgroup of patients who tend to have problems with
conventional THR. In contrast, the results in women have been poor
and we do not recommend metal-on-metal resurfacing in women. Continuous
follow-up is recommended because of the increasing incidence of
pseudotumour with the passage of time.
It is accepted that resurfacing hip replacement
preserves the bone mineral density (BMD) of the femur better than total
hip replacement (THR). However, no studies have investigated any
possible difference on the acetabular side. Between April 2007 and March 2009, 39 patients were randomised
into two groups to receive either a resurfacing or a THR and were
followed for two years. One patient’s resurfacing subsequently failed,
leaving 19 patients in each group. Resurfaced replacements maintained proximal femoral BMD and,
compared with THR, had an increased bone mineral density in Gruen
zones 2, 3, 6, and particularly zone 7, with a gain of 7.5% (95%
confidence interval (CI) 2.6 to 12.5) compared with a loss of 14.6%
(95% CI 7.6 to 21.6). Resurfacing replacements maintained the BMD
of the medial femoral neck and increased that in the lateral zones
between 12.8% (95% CI 4.3 to 21.4) and 25.9% (95% CI 7.1 to 44.6). On the acetabular side, BMD was similar in every zone at each
point in time. The mean BMD of all acetabular regions in the resurfaced
group was reduced to 96.2% (95% CI 93.7 to 98.6) and for the total
hip replacement group to 97.6% (95% CI 93.7 to 101.5) (p = 0.4863).
A mean total loss of 3.7% (95% CI 1.0 to 6.5) and 4.9% (95% CI 0.8
to 9.0) of BMD was found above the acetabular component in W1 and
10.2% (95% CI 0.9 to 19.4) and 9.1% (95% CI 3.8 to 14.4) medial
to the implant in W2 for resurfaced replacements and THRs respectively.
Resurfacing resulted in a mean loss of BMD of 6.7% (95% CI 0.7 to
12.7) in W3 but the BMD inferior to the acetabular component was
maintained in both groups. These results suggest that the ability of a resurfacing hip replacement
to preserve BMD only applies to the femoral side.
Plasma levels of cobalt and chromium ions and
Metal Artefact Reduction Sequence (MARS)-MRI scans were performed
on patients with 209 consecutive, unilateral, symptomatic metal-on-metal
(MoM) hip arthroplasties. There was wide variation in plasma cobalt
and chromium levels, and MARS-MRI scans were positive for adverse reaction
to metal debris (ARMD) in 84 hips (40%). There was a significant
difference in the median plasma cobalt and chromium levels between
those with positive and negative MARS-MRI scans (p <
0.001).
Compared with MARS-MRI as the potential reference standard for the
diagnosis of ARMD, the sensitivity of metal ion analysis for cobalt
or chromium with a cut-off of >
7 µg/l was 57%. The specificity was
65%, positive predictive value was 52% and the negative predictive
value was 69% in symptomatic patients. A lowered threshold of >
3.5 µg/l for cobalt and chromium ion levels improved the sensitivity
and negative predictive value to 86% and 74% but at the expense
of specificity (27%) and positive predictive value (44%). Metal ion analysis is not recommended as a sole indirect screening
test in the surveillance of symptomatic patients with a MoM arthroplasty.
The investigating clinicians should have a low threshold for obtaining
cross-sectional imaging in these patients, even in the presence
of low plasma metal ion levels.
Modern metal-on-metal hip resurfacing has been
widely performed in the United Kingdom for over a decade. However,
the literature reports conflicting views of the benefits: excellent
medium- to long-term results with some brands in specific subgroups,
but high failure rates and local soft-tissue reactions in others.
The National Joint Registry for England and Wales (NJR) has collected
data on all hip resurfacings performed since 2003. This retrospective
cohort study recorded survival time to revision from a resurfacing
procedure, exploring risk factors independently associated with
failure. All patients with a primary diagnosis of osteoarthritis
who underwent resurfacing between 2003 and 2010 were included in
the analyses. Cox’s proportional hazard models were used to analyse
the extent to which the risk of revision was related to patient,
surgeon and implant covariates. A total of 27 971 hip resurfacings were performed during the
study period, of which 1003 (3.59%) underwent revision surgery.
In the final adjusted model, we found that women were at greater
risk of revision than men (hazard ratio (HR) = 1.30, p = 0.007),
but the risk of revision was independent of age. Of the implant-specific
predictors, five brands had a significantly greater risk of revision
than the Birmingham Hip Resurfacing (BHR) (ASR: HR = 2.82, p <
0.001,
Conserve: HR = 2.03, p <
0.001, Cormet: HR = 1.43, p = 0.001,
Durom: HR = 1.67, p <
0.001, Recap: HR = 1.58, p = 0.007). Smaller
femoral head components were also significantly more likely to require
revision (≤ 44 mm: HR = 2.14, p <
0.001, 45 to 47 mm: HR = 1.48,
p = 0.001) than medium or large heads, as were operations performed
by low-volume surgeons (HR = 1.36, p <
0.001). Once these influences
had been removed, in 4873 male patients <
60 years old undergoing
resurfacing with a BHR, the five-year estimated risk of revision
was 1.59%. In summary, after adjustment for a range of covariates we found
that there were significant differences in the rate of failure between
brands and component sizes. Younger male patients had good five-year
implant survival when the BHR was used.
An ongoing prospective study to investigate failing metal-on-metal
hip prostheses was commenced at our centre in 2008. We report on
the results of the analysis of the first consecutive 126 failed
mated total hip prostheses from a single manufacturer. Analysis was carried out using highly accurate coordinate measuring
to calculate volumetric and linear rates of the articular bearing
surfaces and also the surfaces of the taper junctions. The relationship
between taper wear rates and a number of variables, including bearing
diameter and orientation of the acetabular component, was investigated.Objectives
Methods
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.
The Articular
We retrospectively studied 14 patients with proximal and diaphyseal tumours and disappearing bone (Gorham’s) disease of the humerus treated with wide resection and reconstruction using an allograft-resurfacing composite (ARC). There were ten women and four men, with a mean age of 35 years (8 to 69). At a mean follow-up of 25 months (10 to 89), two patients had a fracture of the allograft. In one of these it was revised with a similar ARC and in the other with an intercalary prosthesis. A further patient had an infection and a fracture of the allograft that was revised with a megaprosthesis. In all patients with an ARC, healing of the ARC-host bone interface was observed. One patient had failure of the locking mechanism of the total elbow replacement. The mean post-operative Musculoskeletal Tumor Society score for the upper extremity was 77% (46.7% to 86.7%), which represents good and excellent results; one patient had a poor result (46.7%). In the short term ARC effectively relieves pain and restores shoulder function in patients with wide resection of the proximal humerus. Fracture and infection remain significant complications.
Bioengineering reasons for increased wear and failure of metal-on-metal (MoM) bearings in hip prostheses have been described. Low wear occurs in MoM hips when the centre of the femoral head is concentric with the centre of the acetabular component and the implants are correctly positioned. Translational or rotational malpositioning of the components can lead to the contact-patch of the femoral component being displaced to the rim of the acetabular component, resulting in a ten- to 100-fold increase in wear and metal ion levels. This may cause adverse tissue reactions, loosening of components and failure of the prosthesis.