To assess the incidence of radiological lateral osteoarthritis (OA) at 15 years after medial unicompartmental knee arthroplasty (UKA) and assess the relationship of lateral OA with symptoms and patient characteristics. Cemented Phase 3 medial Oxford UKA implanted by two surgeons since 1998 for the recommended indications were prospectively followed. A 15-year cumulative revision rate for lateral OA of 5% for this series was previously reported. A total of 163 unrevised knees with 15-year (SD 1) anterior-posterior knee radiographs were studied. Lateral joint space width (JSWL) was measured and severity of lateral OA was classified as: nil/mild, moderate, and severe. Preoperative and 15-year Oxford Knee Scores (OKS) and American Knee Society Scores were determined. The effect of age, sex, BMI, and intraoperative findings was analyzed. Statistical analysis included one-way analysis of variance and Kruskal-Wallis H test, with significance set at 5%.Aims
Methods
The Oxford Domed Lateral (ODL) Unicompartmental Knee Replacement (UKR) has some advantages over other lateral UKRs, but the mobile bearing dislocation rate is high (1–6%). Medial dislocations, with the bearing lodged on the tibial component wall, are most common. Anterior/posterior dislocations are rare. For a dislocation to occur distraction of the joint is required. We have developed and validated a dislocation analysis tool based on a computer model of the ODL with a robotics path-planning algorithm to determine the Vertical Distraction required for a Dislocation (VDD), which is inversely related to the risk of dislocation. To modify the ODL design so the risk of medial dislocation decreases to that of an anterior/posterior dislocation.Abstract
Background
Objectives
There are advantages and disadvantages of Unicompartmental (UKR) and Total Knee Replacement, with UKR having better functional outcomes with fewer complications but a higher revision rate. The relative merits depend on patient characteristics. The aim was to compare UKR and TKR risk-benefits and cost-effectiveness in patients with severe systemic morbidity. Data from the National Joint Registry for England, Wales and Northern Ireland was linked to hospital inpatient and patient-reported outcomes data. Patients with American Society of Anesthesiologists (ASA) grade ≥3 undergoing UKR or TKR were identified. Propensity score stratification was used to compare 90-day complications and 5-year revision and mortality of 2,256 UKR and 57,682 TKR, and in a subset of 145 UKR and 23,344 TKR Oxford Knee Scores (OKS). A health-economic analysis was based on EQ-5D and NHS hospital costs.Background
Methods
Lateral Unicompartmental Knee Arthroplasty (UKA) is a recognised treatment option in the management of lateral Osteoarthritis (OA) of the knee. Whilst there is extensive evidence on the indications and contraindcations in Medial UKA there is limited evidence on this topic in Lateral UKA. The aim of this study was to assess our experience of mobile lateral UKR and to look specifically at the effect of Contraindications on the outcome. A total of 325 consecutive domed lateral UKAs undertaken for the recommended indications were included, and their functional and survival outcomes were assessed. The effects of age, weight, activity, and presence of full- thickness erosions of cartilage in the patellofemoral joint on outcome were evaluated.Background
Method
To report mid- to long-term results of Oxford mobile bearing domed lateral unicompartmental knee arthroplasty (UKA), and determine the effect of potential contraindications on outcome. A total of 325 consecutive domed lateral UKAs undertaken for the recommended indications were included, and their functional and survival outcomes were assessed. The effects of age, weight, activity, and the presence of full-thickness erosions of cartilage in the patellofemoral joint on outcome were evaluated.Aims
Methods
The aim of this study was to determine the polyethylene wear rate of Phase 3 Oxford Unicompartmental Knee Replacement bearings and to investigate the effects of resin type and manufacturing process. A total of 63 patients with at least ten years’ follow-up with three bearing types (1900 resin machined, 1050 resin machined, and 1050 resin moulded) were recruited. Patients underwent full weight-bearing model-based radiostereometric analysis to determine the bearing thickness. The linear wear rate was estimated from the change in thickness divided by the duration of implantation.Objectives
Methods
The commonest causes of revision of Unicompartmental Knee Replacement (UKR) in National Registers are loosening and pain. Cementless UKR was introduced to address loosening and was found, in small randomised studies, to have better radiographic fixation than Cemented UKR. Although non-significant these studies also suggested the clinical outcome was better with cementless. The aim of this larger study was to compare the pain and function of cementless and cemented UKR at five years. 263 Cemented and 266 Cementless UKR of identical design, implanted by four high volume surgeons for the same indications, were reviewed by independent physiotherapists at five years. Revision, re-operation, Oxford Knee Score (OKS), American Knee Society score (AKSS) and EQ-5D were assessed. Two pain specific scores were also used: Pain Detect (PD) and Intermittent and Constant Osteoarthritis Pain (ICOAP). The pain scores were normalised onto a scale of 0 to 100 with 100 being the best. The cemented cohort was mainly implanted before the cementless, although there was considerable overlap. To explore whether differences were due to progressive improvement in surgical practice with time each cohort was divided into early and late subgroups.Introduction
Methods
Unicompartmental knee replacement (UKR) offers advantages over total knee replacement but has higher revision rates particularly for aseptic loosening. Cementless UKR was introduced in an attempt to address this. We used National Joint Registry (NJR) data to compare the 10-year results of cemented and cementless mobile bearing UKR whilst matching for important patient, implant and surgical factors. We also explored the influence of caseload on outcome. We performed a retrospective observational study using NJR data on 30,814 cemented and 9,708 cementless mobile bearing UKR implanted between 2004 and 2016. Logistic regression was utilised to calculate propensity scores allowing for matching of cemented and cementless groups for various patient, implant and surgical confounders, including surgeon's caseload, using a one to one ratio. 14,814 UKRs (7407 cemented and 7407 cementless) were propensity score matched. Outcomes studied were revision, defined as removal, addition or exchange of a component, and reasons for revision. Implant survival was compared using Cox regression models and groups were stratified according to surgeon caseload.Introduction
Methods
Although we know that smoking damages health, we do not know impact of smoking on a patient's outcome following primary knee arthroplasty (KA). In the UK, clinical commissioning groups (CCGs) have the authority (& funds) to commission healthcare services for their communities. Over the past decade, an increasing number of CCGs are using smoking as a contraindication for patients with end-stage symptomatic knee arthritis being referred to a specialist for due consideration of KA without any clear evidence of the associated risks & benefits. The overall objective of this study is to compare clinical outcomes after knee arthroplasty surgery in smokers, ex-smokers & non-smokers. We obtained data from the UK Clinical Research Practice Datalink (CPRD) that contains information on over 11 million patients (7% of the UK population) registered at over 600 general practices. CPRD data was linked to Hospital Episode Statistics, hospital admissions & Patient Reported Outcome Measures (PROMs) data. We collected data on all KAs (n=64,071) performed over a 21-year period (1995 to 2016). Outcomes assessed included: local & systemic complications (at 6-months post-surgery): infections (wound, respiratory, urinary), heart attack, stroke & transient ischaemic attack, venous thromboembolism, hospital readmissions & GP visits (1-year), analgesic use (1-year), surgical revision (up to 20-years), mortality (90-days and 1-year), & 6-month change from pre-operative scores in Oxford Knee Score (OKS). Regression modelling is used to describe the association of smoking on outcomes, adjusting for confounding factors.Introduction
Methods
Unicompartmental knee arthroplasty (UKA) offers significant advantages over total knee arthroplasty (TKA) but is reported to have higher revision rates in joint registries. In both the New Zealand and the UK national registry the revision rate of cementless UKR is less than cementless. It is not clear whether this is because the cementless is better or because more experienced surgeons, who tend to get better results are using cementless. We aim to use registry data to compare cemented and cementless UKA outcomes, matching for surgical experience and other factors. We performed a retrospective observational study using National Joint Registry (NJR) data on 10,836 propensity matched Oxford UKAs (5418 cemented and 5418 cementless) between 2004 and 2015. Logistic regression was utilized to calculate propensity scores to match the cemented and cementless groups for multiple confounders using a one to one ratio. Standardised mean differences were used before and after matching to assess for any covariate imbalances. The outcomes studied were implant survival, reasons for revision and patient survival. The endpoint for implant survival was revision surgery (any component removal or exchange). Cumulative patient and implant survival rates were determined using the Kaplan-Meier method. Patients not undergoing revision or death were censored on the study end date. The study endpoints implant and patient survival were compared between cemented and cementless groups using Cox regression models with a robust variance estimator.Introduction
Methods
The revision rate of unicompartmental knee replacement (UKR) in national joint registries is much higher than that of total knee replacements and that of UKR in cohort studies from multiple high-volume centres. The reasons for this are unclear but may be due to incorrect patient selection, inadequate surgical technique, and inappropriate indications for revision. Meniscal bearing UKR has well defined evidence based indications based on preoperative radiographs, the surgical technique can be assessed from post-operative radiographs and the reason for revision from pre-revision radiographs. However, for an accurate assessment aligned radiographs are required. The aim of the study was to determine why the revision rate of UKR in registries is so high by undertaking a radiographic review of revised UKR identified by the United Kingdom's (UK) National Joint Registry (NJR). A novel cross-sectional study was designed. Revised medial meniscal bearing UKR with primary operation registered with the NJR between 2006 and 2010 were identified. Participating centres from all over the country provided blinded pre-operative, post-operative, and pre-revision radiographs. Two observers reviewed the radiographs.Introduction
Methods
We studied subchondral intraosseous pressure (IOP) in an animal model during loading, and with vascular occlusion. We explored bone compartmentalization by saline injection. Needles were placed in the femoral condyle and proximal tibia of five anaesthetized rabbits and connected to pressure recorders. The limb was loaded with and without proximal vascular occlusion. An additional subject had simultaneous triple recordings at the femoral head, femoral condyle and proximal tibia. In a further subject, saline injections at three sites were carried out in turn.Objectives
Materials and Methods
Unicompartmental knee arthroplasty (UKA) has
numerous advantages over total knee arthroplasty (TKA) and one disadvantage,
the higher revision rate. The best way to minimize the revision
rate is for surgeons to use UKA for at least 20% of their knee arthroplasties.
To achieve this, they need to learn and apply the appropriate indications
and techniques. This would decrease the revision rate and increase
the number of UKAs which were implanted, which would save money
and patients would benefit from improved outcomes over their lifetime. Cite this article:
The primary stability of the cementless Oxford Unicompartmental Knee Replacement (OUKR) relies on interference fit (or press fit). Insufficient interference may cause implant loosening, whilst excessive interference could cause bone damage and fracture. The aim of this study was to identify the optimal interference fit by measuring the force required to seat the tibial component of the cementless OUKR (push-in force) and the force required to remove the component (pull-out force). Six cementless OUKR tibial components were implanted in 12 new slots prepared on blocks of solid polyurethane foam (20 pounds per cubic foot (PCF), Sawbones, Malmo, Sweden) with a range of interference of 0.1 mm to 1.9 mm using a Dartec materials testing machine HC10 (Zwick Ltd, Herefordshire, United Kingdom) . The experiment was repeated with cellular polyurethane foam (15 PCF), which is a more porous analogue for trabecular bone.Objectives
Materials and Methods
The aim of this study was to determine whether the rates of revision
for metal-on-metal (MoM) total hip arthroplasties (THAs) with Pinnacle
components varied according to the year of the initial operation,
and compare these with the rates of revision for other designs of
MoM THA. Data from the National Joint Registry for England and Wales included
36 mm MoM THAs with Pinnacle acetabular components which were undertaken
between 2003 and 2012 with follow-up for at least five years (n
= 10 776) and a control group of other MoM THAs (n = 13 817). The
effect of the year of the primary operation on all-cause rates of revision
was assessed using Cox regression and interrupted time-series analysis.Aims
Patients and Methods
To determine the outcomes following revision surgery of metal-on-metal
hip arthroplasties (MoMHA) performed for adverse reactions to metal
debris (ARMD), and to identify factors predictive of re-revision. We performed a retrospective observational study using National
Joint Registry (NJR) data on 2535 MoMHAs undergoing revision surgery
for ARMD between 2008 and 2014. The outcomes studied following revision were
intra-operative complications, mortality and re-revision surgery.
Predictors of re-revision were identified using competing-risk regression
modelling.Aims
Patients and Methods
Few studies have assessed outcomes following non-metal-on-metal hip arthroplasty (non-MoMHA) revision surgery performed for adverse reactions to metal debris (ARMD). We assessed outcomes following non-MoMHA revision surgery performed for ARMD, and identified predictors of re-revision. We performed a retrospective observational study using data from the National Joint Registry for England and Wales. All non-MoMHAs undergoing revision surgery for ARMD between 2008 and 2014 were included (185 hips in 185 patients). Outcome measures following ARMD revision were intra-operative complications, mortality and re-revision surgery. Predictors of re-revision were identified using Cox regression.Objectives
Methods
It is not clear whether anterior knee pain and osteoarthritis
(OA) of the patellofemoral joint (PFJ) are contraindications to
medial unicompartmental knee arthroplasty (UKA). Our aim was to
investigate the long-term outcome of a consecutive series of patients,
some of whom had anterior knee pain and PFJ OA managed with UKA. We assessed the ten-year functional outcomes and 15-year implant
survival of 805 knees (677 patients) following medial mobile-bearing
UKA. The intra-operative status of the PFJ was documented and, with
the exception of bone loss with grooving to the lateral side, neither
the clinical or radiological state of the PFJ nor the presence of
anterior knee pain were considered a contraindication. The impact
of radiographic findings and anterior knee pain was studied in a
subgroup of 100 knees (91 patients).Aims
Patients and Methods
Advocates of debridement, antibiotics and implant retention (DAIR)
in hip periprosthetic joint infection (PJI) argue that a procedure
not disturbing a sound prosthesis-bone interface is likely to lead
to better survival and functional outcome compared with revision.
This case-control study aims were to compare outcome of DAIRs for
infected primary total hip arthroplasty (THA) with outcomes following
primary THA and two-stage revision of infected primary THAs. We retrospectively reviewed all DAIRs, performed for confirmed
infected primary hip arthropasty (n = 82) at out institution, between
1997 and 2013. Data recorded included full patient information and
type of surgery. Outcome measures included complications, mortality,
implant survivorship and functional outcome. Outcome was compared with
two control groups matched for gender and age; a cohort of primary
THAs (n = 120) and a cohort of two-stage revisions for infection
(n = 66).Aims
Patients and Methods
