Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning. 3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane.Aims
Methods
The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants. We compared two groups, one made via 3D-printing (n = 7) and the other using conventional techniques (n = 7). We collected implant details, type of surgery and removal technique, patient demographics, and clinical history. Bone integration was assessed by macroscopic visual analysis, followed by sectioning to allow undecalcified histology on eight sections (~200 µm) for each implant. The outcome measures considered were area of bone attachment (%), extent of bone ingrowth (%), bone-implant contact (%), and depth of ingrowth (%), and these were quantified using a line-intercept method.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
Previous studies have suggested that metal-on-metal (MoM) Pinnacle (DePuy Synthes, Warsaw, Indiana) hip arthroplasties implanted after 2006 exhibit higher failure rates. This was attributed to the production of implants with reduced diametrical clearances between their bearing surfaces, which, it was speculated, were outside manufacturing tolerances. This study aimed to better understand the performance of Pinnacle Systems manufactured before and after this event. A total of 92 retrieved MoM Pinnacle hips were analyzed, of which 45 were implanted before 2007, and 47 from 2007 onwards. The ‘pre-2007’ group contained 45 implants retrieved from 21 male and 24 female patients, with a median age of 61.3 years (interquartile range (IQR) 57.1 to 65.5); the ‘2007 onwards’ group contained 47 implants retrieved from 19 male and 28 female patients, with a median age of 61.8 years (IQR 58.5 to 67.8). The volume of material lost from their bearing and taper surfaces was measured using coordinate and roundness measuring machines. These outcomes were then compared statistically using linear regression models, adjusting for potentially confounding factors.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 use of ceramic femoral heads in total hip arthroplasty (THA) has increased due to their proven low bearing wear characteristics. Ceramic femoral heads are also thought to reduce wear and corrosion at the head-stem junction with titanium (Ti) stems when compared with metal heads. We sought to evaluate taper damage of ceramic compared with metal heads when paired with cobalt chromium (CoCr) alloy stems in a single stem design. This retrieval study involved 48 total hip arthroplasties (THAs) with CoCr V40 trunnions paired with either CoCr (n = 21) or ceramic (n = 27) heads. The taper junction of all hips was evaluated for fretting/corrosion damage and volumetric material loss using a roundness-measuring machine. We used linear regression analysis to investigate taper damage differences after adjusting for potential confounding variables.Objectives
Methods
The aim of this study was to compare the design of the generic
OptiStem XTR femoral stem with the established Exeter femoral stem. We obtained five boxed, as manufactured, implants of both designs
at random (ten in total). Two examiners were blinded to the implant
design and independently measured the mass, volume, trunnion surface
topography, trunnion roughness, trunnion cone angle, Caput-Collum-Diaphyseal
(CCD) angle, femoral offset, stem length, neck length, and the width
and roughness of the polished stem shaft using peer-reviewed methods.
We then compared the stems using these parameters.Aims
Materials and Methods
The National Joint Registry for England, Wales and Northern Ireland
(NJR) has extended its scope to report on hospital, surgeon and
implant performance. Data linkage of the NJR to the London Implant
Retrieval Centre (LIRC) has previously evaluated data quality for
hip primary procedures, but did not assess revision records. We analysed metal-on-metal hip revision procedures performed
between 2003 and 2013. A total of 69 929 revision procedures from
the NJR and 929 revised pairs of components from the LIRC were included.Aims
Methods
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:
We measured the orientation of the acetabular and femoral components in 45 patients (33 men, 12 women) with a mean age of 53.4 years (30 to 74) who had undergone revision of metal-on-metal hip resurfacings. Three-dimensional CT was used to measure the inclination and version of the acetabular component, femoral version and the horizontal femoral offset, and the linear wear of the removed acetabular components was measured using a roundness machine. We found that acetabular version and combined version of the acetabular and femoral components were weakly positively correlated with the rate of wear. The acetabular inclination angle was strongly positively correlated with the rate of wear. Femoral version was weakly negatively correlated with the rate of wear. Application of a threshold of >
5 μm/year for the rate of wear in order to separate the revisions into low or high wearing groups showed that more high wearing components were implanted outside Lewinnek’s safe zone, but that this was mainly due to the inclination of the acetabular component, which was the only parameter that significantly differed between the groups. We were unable to show that excess version of the acetabular component alone or combined with femoral version was associated with an increase in the rate of wear based on our assessment of version using CT.
We carried out metal artefact-reduction MRI, three-dimensional CT measurement of the position of the component and inductively-coupled plasma mass spectrometry analysis of cobalt and chromium levels in whole blood on 26 patients with unexplained pain following metal-on-metal resurfacing arthroplasty. MRI showed periprosthetic lesions around 16 hips, with 14 collections of fluid and two soft-tissue masses. The lesions were seen in both men and women and in symptomatic and asymptomatic hips. Using three-dimensional CT, the median inclination of the acetabular component was found to be 55° and its positioning was outside the Lewinnek safe zone in 13 of 16 cases. Using inductively-coupled plasma mass spectrometry, the levels of blood metal ions tended to be higher in painful compared with well-functioning metal-on-metal hips. These three clinically useful investigations can help to determine the cause of failure of the implant, predict the need for future revision and aid the choice of revision prostheses.
