Debridement, antibiotics and implant retention (DAIR) is a surgical option in the treatment of prosthetic joint infection (PJI). It is thought to be most appropriate in the treatment of early (≤6 weeks post-op) PJI. Most studies to-date reporting on DAIRs in hip PJI have been underpowered by reporting on small cohorts (n= <45), or report on registry data with associated biases and limitations. In our, tertiary referral, bone infection unit we consider DAIR to be a suitable option in all cases of PJI with a soundly fixed prosthesis, with early or late presentation, especially in patients who are too elderly or infirm to undergo major surgery. Aim: To define the 10-year outcome following DAIR in hip PJI and identify factors that influence it. We retrospectively reviewed all DAIRs performed in our unit between 1997 and 2013 for hip PJI. Only infected cases confirmed by histological and microbiological criteria were included. Data recorded included patient demographics and medical history, type of surgery performed (DAIR or DAIR + exchange of modular components), organism identified and type/duration of antibiotic treatment. Outcome measures included complications, mortality rate, implant survivorship and functional outcome. 121 DAIRs were identified with mean age of 71 years (range: 33–97). 67% followed an index procedure of 1° arthroplasty. 53% included exchange of modular components. 60% of DAIRs were for early onset PJI. Isolated staphylococcus was present in 50% of cases and 25% had polymicrobial infection. At follow-up (mean:7 years, range: 0.3 – 18), 83 patients were alive; 5- and 10- year mortality rates were 15% and 35% respectively. 45% had a complication (persistence of infection: 27%, dislocation: 10%) and 40% required further surgery. Twenty hips have been revised to-date (17%). Performing a DAIR and not exchanging the modular components was associated with an almost 3× risk (risk ratio: 2.9) of subsequent implant failure (p=0.04). 10-yr implant survivorship was 80% (95%CI: 70 – 90%). Improved 10-year implant survivorship was associated with DAIR performed for early PJI (85% Vs 68%, p=0.04). Functional outcome will be discussed. DAIR is a particularly valuable option in the treatment of hip PJI, especially in the early post-operative period. Whenever possible, exchange of modular implants should be undertaken, however DAIRs are associated with increased morbidity even in early PJI. Factors that predict success of DAIR in late PJI need to be identified.
Joint preserving procedures have gained popularity in an attempt to delay arthroplasty in young, dysplastic hips. Excellent results can be achieved with peri-acetabular osteotomy (PAO) in congruent non-arthritic hips. The role of salvage procedures such as the Shelf acetabuloplasty remains undefined. This study aims to determine the long-term survival and functional outcome following Shelf acetabuloplasty and to identify factors that influence outcome. This is a retrospective, consecutive, multi-surgeon, case series from a UK referral centre. 125 Shelf procedures were performed between 1987–2013 on 117 patients for symptomatic hip dysplasia. Mean age was 33 years (15–53). Mean follow-up was 10 years (1–27). Radiographic parameters measured included pre-operative arthritis, acetabular-index, centre-edge-angle, joint congruency, subluxation and femoral sphericity. Oxford Hip and UCLA scores were collected at follow-up. Failure was defined as conversion to arthroplasty or OHS<20.Introduction
Patients/Materials & Methods
We assessed the orientation of the acetabular
component in 1070 primary total hip arthroplasties with hard-on-soft, small
diameter bearings, aiming to determine the size and site of the
target zone that optimises outcome. Outcome measures included complications,
dislocations, revisions and ΔOHS (the difference between the Oxford
Hip Scores pre-operatively and five years post-operatively). A wide
scatter of orientation was observed (2 This study demonstrated that with traditional technology surgeons
can only reliably achieve a target zone of ±15°. As the optimal
zone to diminish the risk of dislocation is also ±15°, surgeons
should be able to achieve this. This is the first study to demonstrate
that optimal orientation of the acetabular component improves the
functional outcome. However, the target zone is small (± 5°) and
cannot, with current technology, be consistently achieved. Cite this article:
National Institute of Clinical Excellence guidelines
state that cemented stems with an Orthopaedic Data Evaluation Panel
(ODEP) rating of >
3B should be used for hemiarthroplasty when treating
an intracapsular fracture of the femoral neck. These recommendations
are based on studies in which most, if not all stems, did not hold
such a rating. This case-control study compared the outcome of hemiarthroplasty
using a cemented (Exeter) or uncemented (Corail) femoral stem. These
are the two prostheses most commonly used in hip arthroplasty in
the UK. Data were obtained from two centres; most patients had undergone
hemiarthroplasty using a cemented Exeter stem (n = 292/412). Patients
were matched for all factors that have been shown to influence mortality
after an intracapsular fracture of the neck of the femur. Outcome
measures included: complications, re-operations and mortality rates
at two, seven, 30 and 365 days post-operatively. Comparable outcomes
for the two stems were seen. There were more intra-operative complications in the uncemented
group (13% This study therefore supports the use of both cemented and uncemented
stems of proven design, with an ODEP rating of 10A, in patients
with an intracapsular fracture of the neck of the femur. Cite this article:
There is great variability in acetabular component
orientation following hip replacement. The aims of this study were
to compare the component orientation at impaction with the orientation
measured on post-operative radiographs and identify factors that
influence the difference between the two. A total of 67 hip replacements
(52 total hip replacements and 15 hip resurfacings) were prospectively
studied. Intra-operatively, the orientation of the acetabular component
after impaction relative to the operating table was measured using
a validated stereo-photogrammetry protocol. Post-operatively, the
radiographic orientation was measured; the mean inclination/anteversion
was 43° ( This study demonstrated that in order to achieve a specific radiographic
orientation target, surgeons should implant the acetabular component
5° less inclined and 8° more anteverted than their target. Great
variability (2 Cite this article:
The orientation of the acetabular component is
influenced not only by the orientation at which the surgeon implants
the component, but also the orientation of the pelvis at the time
of implantation. Hence, the orientation of the pelvis at set-up
and its movement during the operation, are important. During 67
hip replacements, using a validated photogrammetric technique, we
measured how three surgeons orientated the patient’s pelvis, how
much the pelvis moved during surgery, and what effect these had
on the final orientation of the acetabular component. Pelvic orientation
at set-up, varied widely (mean (± 2, standard deviation ( Cite this article:
Metal-on-metal hip resurfacing (MoMHRA) requires a new standardized radiographic evaluation protocol. Evaluation of the acetabular component is similar to total hip arthroplasty but the femoral component requires different criteria since there is no component in the femoral canal and the metallic femoral implant overlies the junctions between bone-cement and cement-prosthesis. Lucencies around the metaphyseal HRA femoral stem can be described with the femoral zonal system into 3 peg-zones (Amstutz' et al) but this doesn't account for bony changes of the femoral neck away from the stem. This study proposes a new femoral zonal system for radiographic HRA assessment. We tested the efficacy of radiographs in identifying a problem by reviewing 711 radiographs of resurfaced hips and correlating radiographic features to outcome. 611 in-situ HRA (one surgeon) with minimum two radiographs at >12 months postoperatively and 100 revised HRA (55 referred) were assessed for component positioning, reactive lines±cortical thickening±cancellous condensation (borderline) and lucent lines±osteolysis±bone resorption (sinister). Findings around the acetabular implant were classified in six zones: Zones I-III equally distributed acetabular zones (DeLee-Charnley); Zone IV, V and VI situated in the iliac, pubic and ischial bone respectively. Findings around the proximal femur are defined with a new zonal system, dividing the implant-cement-bone interfaces and the femoral neck into 7 areas. Zones 1,7 at the superior and inferior part of the femoral neck-head, zones 2,3 at the proximal and distal halves of the superior aspect of the stem, zone 4 at the tip, zones 5,6 at the distal and proximal inferior aspects of the stem). Radiological findings and zones were correlated with gender, size, survival, Harris Hip Scores (HHS), metal ions, and adverse soft tissue reactions (ALTR).INTRODUCTION
METHODS
Solid or cystic pseudotumour is a potentially destructive complication of metal on metal (MoM) couples, usually needing revision surgery. However, complete clearance of the pseudotumour is unlikely at times. This prospective case-controlled study reports cases which had recurrence after revision surgery for pseudotumour related to metal on metal hip couples. A total of 37 hips (33 MoM hip resurfacing and four big head MoM total hip arthroplasty (THA)) were revised for pseudotumour during the last 10 years. The patient demographics, time to revision, cup orientation, operative and histological findings were recorded for this cohort. Patients were divided into two groups - group R (needing re-revision for disease progression) and group C (control - no evidence of disease progression). Oxford hip scores (OHS, 0–48, 48 best outcome) were used to assess clinical outcome. The diagnosis of disease progression was based on recurrence of clinical symptoms, cross-sectional imaging, operative and histological findings.Introduction
Methods
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.
Since the introduction of 3rd generation Metal-on-Metal-Hip-Resurfacing-Arthroplasty (MoMHRA), thousands of such prostheses have been implanted worldwide in younger patients with end-stage hip osteoarthritis. However, no independent centre has reported their medium-to-long term outcome. The aim of this study is to report the ten year survival and outcome of the Birmingham Hip Resurfacing (BHR), the most commonly used MoMHRA worldwide. Since 1999, 648 BHRs were implanted in 555 patients, the majority of which were male (326). The mean age at surgery was 52.1years (range: 17–82), with primary OA as most common indication (85%). Mean follow up was 7.1years (range: 1–11). The Oxford Hip Score (OHS) and UCLA questionnaires were sent to all patients. Implant survival was established, with revision as the end point. Sub-analysis was performed by gender, femoral component size (small: <45mm, standard: 46–52, large: >53mm) and age at surgery (young:<50yrs, old:>50yrs).Introduction
Methods
Metal-on-metal hip resurfacing arthroplasty (MoMHRA) is a surgical option in the treatment of end-stage hip disease. The measurement of systemic levels of metal ions gives an insight into the wear occurring and is advocated by regulatory bodies as routine practice in the assessment of resurfaced hips. However, the acceptable upper levels of Chromium (Cr) and Cobalt (Co) ions concentration with clinical significance still have to be established. The aim of this study is to address this issue in unilateral and bilateral resurfaced hips. 453 patients with unilateral MoMHRA and 139 patients with bilateral MoMHRA at >12 months postoperative were retrospectively identified from an independent hip specialist's database. Routine metal ion levels were measured at last follow-up (ICPMS protocol). Radiological assessment included measurement of acetabular component orientation using EBRA, calculation of contact patch to rim (CPR) distance, and evaluation for any adverse X-ray findings. The cohort was divided into the well functioning group (Group A) and the non-well functioning group (Group B). A well functioning resurfacing gad to fulfil all of the following criteria (bilateral patients had to fulfil criteria for both hips): no patient reported hip complaints, no surgeon detected clinical findings, HHS> 95, CPR distance> 10mm, no abnormal radiological findings and no further operation scheduled. Upper levels (acceptable limits) of Cr/Co were considered to be represented by the top margin of the box-whisker plot [upper limit = 75th quartile value + (1.5 x interquartile range)] in Group A.INTRODUCTION
METHODS
Femoral neck narrowing (NN) following Metal-on-Metal Hip Resurfacing Arthroplasty (MoMHRA) is a well-recognised clinical phenomenon. The incidence of resurfaced hips with NN > 10% is reported to be up to 27%. Its pathogenesis is thought to be multi-factorial secondary to stress shielding, impingement, osteolysis secondary to wear/ion particles and as a result of reduced vascularity and pressure effect on cancellous bone secondary to the presence of a soft-tissue mass around the resurfaced hip. Recognised risk factors for its development include: female gender and the presence of a pseudotumour. Serum Chromium (Cr) and Cobalt (Co) are recognised surrogate markers of in-vivo wear of MoMHRA. The aims of this study were to establish whether NN is associated with increased wear. A cohort of 214 patients with unilateral MoMHRA (139M: 75F) was included in this study. Primary osteoarthritis was the diagnosis leading to surgery for the majority of patients (208). The average age at surgery was 54.1 years old (13–73). Six different implants were used; BHR (116), Conserve plus (92), Recap (2), ASR (2), Adept (1) and Cormet (1). The average femoral component size was 49.2mm (range: 38–59). The average follow up was 4.3 years (range: 2–10). Patients were subdivided into 3 groups as per implant size. Small size component group had implants <45mm, average size group had components 45–51mm and large component size group had components >51mm. All patients had Prosthesis-Junction-Ratio (PJR) measured from postoperative (PJRpost) and at latest follow up (PJRfollow) radiographs. Measurements were made using the method described by Lilikakis1. Metal ion levels (Cr/Co) were measured at last follow-up for all patients. Cr level >5.1g/ml and Co levels >4.4 g/ml were considered high2 and patients with such levels formed the high ion group.INTRODUCTION
METHODS
Osteoarthritis (OA) of the hip is an important cause of pain and morbidity. The mechanisms and pathogenesis of OA'sdevelopment remain unknown. Minor acetabular dysplasia and subtle variations in proximal femoral morphology are increasingly being recognized as factors that potentially compromise the joint biomechanically and lead to OA. Previous studies have shown that risk of hip OA increased as the femoral head to femoral neck ratio (HNR) decreased. Previous work has described the evolutionary change in inferior femoral neck trabecular density and geometry associated with upright stance, but no study has highlighted the evolutionary change in HNR. The aim of this study was to examine evolutionary evidence that the hominin bipedal stance has lead to alterations in HNR that would predispose humans to hip OA. A collaboration with The Natural History Museums of London, Oxford and the Department of Zoology, University of Oxford provided specimens from the Devonian, Jurassic, Cretaceous, Miocene, Palaeolithic and Pleistocene periods to modern day. Specimens included amphibious reptiles, dinosaurs, shrews, tupaiae, lemurs, African ground apes, Lucy (A. Afarensis), H. Erectus, H. Neaderthalis and humans. Species were grouped according to gait pattern; HAKF (hip and knee flexed), Arboreal (ability to stand with hip and knee joints extended) and hominin/bi-pedal. Imaging of specimens was performed using a 64 slice CT scanner. Three-dimensional skeletal geometries were segmented using MIMICS software. Anatomical measurements from bony landmarks were performed to describe changes in HNR, in the coronal plane of the different specimens over time using custom software. Measurements of HNR from the specimens were compared with HNR measurements made from AP pelvic radiographs of 119 normal subjects and 210 patients with known hip OA listed for hip arthroplasty.Introduction
Methods
Tribological studies have described a characteristic wear pattern of metal-on-metal hip resurfacings (MoMHRAs) with a run-in period followed by a ‘bedding-in’ phase minimising wear or by an increasing wear patch with edge loading. The use of metal ions as surrogate markers of in-vivo wear is now recommended as a screening tool for the performance of MoMHRAs. The aims of this retrospective, single-surgeon study were to measure ion levels in unilateral MoMHRAs at different stages during the steady-state in order to study the evolution of wear and factors affecting it. 218 consecutive patients with minimum two serum ion measurements were included. The mean age at surgery was 52.3 years, the first assessment was made at a mean of 2.5 years (11 months–8 years) and the last assessment at a mean of 4.6 years post resurfacing (2– 12 years). Ion level change was defined as Ion level at last assessment minus Ion level at first assessment. Ten different resurfacing designs were implanted, the majority being BHR (n=104), Conserve plus(n=55) and ASR (n=25). The median femoral component size was 50 mm (38–59mm). Radiological assessment of acetabular component orientation was made with EBRA.Introduction
Methods
Studies have suggested that there is a reduction in head-neck-ratio (HNR) associated with MoMHRA. A reduction in HNR at operation would decrease range of movement and increase impingement risk. Impingement could lead to 20 edge loading, increasing wear. Serum ion levels of Chromium (Cr) and Cobalt (Co) are surrogate markers of wear. Although acetabular component orientation has been shown to contribute to wear and PT development, the role of a decrease in HNR has only been highlighted in PT development. This study aimed to measure changes in HNR that occur at resurfacing and determine any gender- and component size-specific differences. In addition it aimed to determine whether changes in HNR could be associated with increased wear. 84 patients (56M: 28F) with unilateral MoMHRA were included. The mean age at surgery was 57 years. The mean femoral component was 49mm. Components were considered small if <45mm, average if between 45–50mm and large if >50mm. Three designs were implanted; BHR, C+ and Recap. The average follow up was 4 years. All patients had Cr/Co levels measured at follow up. Patients were considered to have high ions if Cr and Co levels were 5.1ppb and 4.4ppb respectively. Pre-operative HNR (HNRpre) and the post-operative HNR (HNRpost) were made from the respective pelvic radiographs. Assuming a 2mm thick cartilage layer, the HNR based on the diameter of the articular cartilage pre-operatively (HNRart) was calculated. The immediate changes in HNR as a result of the operation were expressed relative to articular HNR pre-op: HNRartpost=HNRpost–HNRartINTRODUCTION
METHODS
Although simulation studies have shown superior wear properties of metal-on-metal articulations, increased concern exists regarding the excess in-vivo wear of a small number of Metal-on-Metal-Hip-Resurfacing (MoMHRA) implants. Serum ion levels of Chromium (Cr) and Cobalt (Co) are surrogate markers of wear. Risk factors associated with increased wear include female gender, small components, dysplasia, cup orientation outside safe zone and femoral head downsize during surgery with an associated decrease in Head-Neck-Ratio (HNR). However, these factors are interlinked. This study aims to identify the factors that are most important for subsequent wear of MoMHRA, by performing a multivariate analysis. 206 patients (124M: 82F) with unilateral MoMHRA were included in this study. The average follow up was 3.3 years. All patients had Cr/Co levels measured at follow up. Inclination and anteversion of each cup were measured using EBRA. Cups were analysed as being within or outside the previously defined optimum-zone. HNR measurements were made from pre-operative (HNRpre) and post-operative (HNRpost) radiographs. The immediate changes in HNR (downsize/upsize of femoral head) as a result of the operation were expressed as: HNRprepost=HNRpost–HNRpre Multivariate linear regression modelling was used to explore the association between measures of ions with the following predictor variables (gender, age, diagnosis, femoral component size, orientation of the acetabular component, head/neck ratio and position of femoral stem). Analyses were carried out separately for each outcome (Cr and Co). Classification and Regression Tree (CART) models were fitted as a complimentary approach to regression modelling.INTRODUCTION
METHODS
The introduction of hard-on-hard bearings and the consequences of increased wear due to edge-loading have renewed interest in the importance of acetabular component orientation for implant survival and functional outcome following hip arthroplasty. Some studies have shown increased dislocation risk when the cup is mal-oriented which has led to the identification of a safe-zone1. The aims of this prospective, multi-centered study of primary total hip arthroplasty (THA) were to: 1. Identify factors that influence cup orientation and 2. Describe the effect of cup orientation on clinical outcome. In a prospective study involving seven UK centers, patients undergoing primary THA between January 1999 and January 2002 were recruited. All patients underwent detailed assessment pre-operatively as well as post-op. Assessment included data on patient demographics, clinical outcome, complications and further surgery/revision. 681 primary THAs had adequate radiographs for inclusion. 590 hips received cemented cups. The primary functional outcome measure of the study was the change between pre-operative and at latest follow up OHS (OHS). Secondary outcome measures included dislocation rate and revision surgery. EBRA was used to determine acetabular inclination and version. The influence of patient's gender, BMI, surgeon's grade and approach on cup orientation was examined. Four different zones tested as possibly ± (Lewinnek Zone, Callanan's described zone and zones ± 5 and ±10 about the study's mean inclination and anteversion) for a reduced dislocation risk and an optimal functional outcome.INTRODUCTION
METHODS
A femoral head/neck ratio (HNR) of less than 1.27 is associated with an increased risk of arthritis. The aim of this study was to establish whether there is evolutionary evidence that the homonin, bipedal stance has led to alterations in HNR that predispose humans to osteoarthritis (OA). Specimens provided by The Natural History Museums of London, Oxford and the Department of Zoology, University of Oxford were grouped according to gait pattern, HAKF (Hip and knee flexed), Arboreal (ability to stand with hip and knee joints extended) and homonin/bi-pedal. Specimens included those from Devonion, Triassic, Jurrasic, Cretaceous, Miocene, Paleolithic, Pleistocene periods to modern day. Three-dimensional skeletal geometries were segmented using CT images and HNR measurements were taken from coronal views. These were compared with the HNR of 119 asymptomatic human volunteers and 210 patients that had a hip joint replacement for primary OA. Species of the HAKF group had the smallest HNR (1.10, SD:0.09). Species of the Arboreal group had significantly higher HNR (1.63, SD:0.15) in comparison to the Bipedal group (1.41, SD:0.04) (p=0.006), Human (1.33, SD:0.08) and the OA group (1.3, SD:0.09). The range of movement associated with arboreal habitat caused an associated change in HNR. This study would suggest that the HNR peaked in the Miocene period with species that ambulated on both ground and trees. More recent homonin gait appears to have developed a smaller HNR and humans have the smallest amongst their close ancestors. Evolutionary theory would suggest that modern environmental pressures might pre-dispose future hominin evolution to OA, secondary to a further reduction in HNR.
