Instability is reported to account for around 20% of early TKR revisions. The concept of restoring the “Envelope of Laxity” (EoL) mandates a balanced knee through a continuous arc of functional movement. We therefore hypothesised that a single radius (SR) design should confer this stability since it has been proposed that the SR promotes normal medial collateral ligament (MCL) function with isometric stability throughout the full arc of motion.

Our aim was to characterise the EoL and stability offered by a SR cruciate retaining (CR)-TKR, which maintains a SR from 10–110° flexion. This was compared with that of the native knee throughout the arc of flexion in terms of anterior, varus/valgus and internal/ external laxity to assess whether a SR CR-TKR design can mimic normal knee joint kinematics and stability.

Eight fresh frozen cadaveric lower limbs were physiologically loaded on a custom jig. The operating surgeon performed anterior drawer, varus/ valgus and internal/external rotation tests to determine ‘maximum’ displacements in 1) native knee and 2) single radius CR-TKR (Stryker Triathlon) at 0°, 30°, 60°, 90° and 110° flexion. Displacements were recorded using computer navigation. Significance was determined by linear modelling (p≤0.05).

The key finding of this work was that the EoL offered by the SR CR-TKR was largely equivalent to that of the native knee from 0–110°. The EoL increased significantly with flexion angle for both native and replaced knees. Overall, after TKR anterior laxity was comparable with the native knee, whilst total varus-valgus and internal-external rotational laxities reduced by only 1°. However, separated varus and valgus laxities at 110° significantly increased after TKR as did anterior laxity at 30° flexion.

In conclusion, the overall EoL offered by the SR CR-TKR is comparable to that of the native knee. In the absence of soft tissue deficiency, the implant appears to offer reliable and reproducible stability throughout the functional range of movement, with exception of anterior laxity at 30° and varus and valgus laxity when the knee approaches high flexion. These shortcomings should offer scope for future work.

Abnormal wear of cobalt-containing metal-on-metal joints is associated with inflammatory pseudotumours. Cobalt ions activate human toll-like receptor 4 (TLR4), which normally responds to bacterial lipopolysaccharide (LPS) in sepsis. Activation of TLR4 by LPS increases the expression of chemokines IL-8 and CXCL10, which recruit leukocytes and activated T-cells, respectively. This study was designed to determine whether cobalt induces a similar inflammatory response to LPS by promoting the expression of IL-8 and CXCL10. A human monocytic cell line, derived from acute monocytic leukaemia, was treated with cobalt ions and expression of IL-8 and CXCL10 measured at mRNA and protein levels. Cobalt-treated macrophages showed a 60-fold increase in IL-8 mRNA, and an eightfold increase in production of the mature chemokine (both p < 0.001); expression of the CXCL10 gene and protein was also significantly increased by cobalt (both p < 0.001). Experiments were also performed in the presence of CLI-095, a TLR4-specific antagonist which abrogated the cobalt-mediated increase in IL-8 and CXCL10 expression.

These findings suggest that cobalt ions induce inflammation similar to that observed during sepsis by the simultaneous activation of two TLR4-mediated signalling pathways. These pathways result in increased production of IL-8 and CXCL10, and may be implicated in pseudotumour formation following metal-on-metal replacement.

Cite this article: Bone Joint J 2014; 96-B:1172–7.

Summary

Metal-on-metal hip replacements have been associated with adverse reactions including inflammatory pseudotumours and soft tissue necrosis. We have shown that cobalt can directly activate toll-like receptor 4, an immune receptor causing pro-inflammatory interleukin-8 secretion. This may contribute to adverse reaction development.

Objectives

Wear debris released from bearing surfaces has been shown to provoke negative immune responses in the recipient. Excessive wear has been linked to early failure of prostheses. Analysis using coordinate measuring machines (CMMs) can provide estimates of total volumetric material loss of explanted prostheses and can help to understand device failure. The accuracy of volumetric testing has been debated, with some investigators stating that only protocols involving hundreds of thousands of measurement points are sufficient. We looked to examine this assumption and to apply the findings to the clinical arena.

Introduction

National Institute for Health and Clinical Excellence (NICE) guidelines recommend the use of total hip replacement (THR) for displaced intracapsular fractured neck of femur (NOF) in cognitively intact patients who were independently mobile prior to the injury. The National Joint Registry for England and Wales (NJR) has collected data on THRs performed since 2003. This retrospective cohort study explores risk factors independently associated with implant failure and perioperative mortality.

Background

Current analysis of unicondylar knee replacements (UKR) by national registries is based on the pooled results of medial and lateral implants. Using data from the National Joint Registry for England and Wales (NJR) we aimed to determine the proportion of lateral UKR implanted, their survival and reason for failure in comparison to medial UKR.

Background

Both surgeon and hospital volume influence patient outcomes following revision knee arthroplasty.

Introduction

Following in-depth analysis of the market leading brand combinations in which we identified implant influences on risk of revision, we compared revision in patients implanted with different categories of hip replacement in order to find implant with the lowest revision risk, once known flawed options were removed.

Introduction

Renal homeostasis has been shown to influence mortality after hip fractures; this is true for patients with both chronic kidney disease, and those who develop acute renal dysfunction after surgery. We have examined the influence of impaired renal function upon mortality and length of stay. We investigated this relationship through accurate mathematical modelling of available biochemistry data on a cohort of hip fracture patients.

Purpose

To determine how patient characteristics; health status and pre-operative knee function effect patient reported satisfaction and operative success following total knee replacement (TKR). We hypothesised that a number of patient factors would influence the reported levels of symptomatic improvement (success) and satisfaction and that these two outcomes would represent different aspects of the patient's perception of outcome.

Background

The most appropriate form of chemical thromboprophylaxis following knee replacement is a contentious issue. Most national guidelines recommend the use of low molecular weight Heparin (LMWH) whilst opposing the use of aspirin. We compared thromboembolic events, major haemorrhage and death after knee replacement in patients receiving either aspirin or LMWH.

Purpose

Although classic teaching holds that the least amount of constraint should be implanted, there is very little in the literature to substantiate this. This study attempts to quantify the influence of constraint and various indications upon functional outcome following aseptic first time revision knee arthroplasty. The null hypothesis was that the level of constraint and indication for surgery would not influence the functional outcome following revision knee replacement.

Introduction

Unlike the NJR, no surgeon driven national database currently exists for ligament surgery in the UK and therefore information on outcome and adverse event is limited to case series.

The aim of this study was to describe the epidemiology of elite youth soccer knee injuries from prospective data collected from forty-one English FA Football Academies over a 5 year period. 12306 players were registered from U9 to the U16 age category.

We studied the incidence of injuries around the knee with particular emphasis upon those causing greater than 28 days time off sport.

There were 609 knee injuries with a mean incidence of 0.71 knee injuries per player per year and a median of 17 training days and 2 matches missed per knee injury. Increased injury rates were seen in older players, in competitive situations and in the latter stages of each half of play. Peaks in injury numbers were seen in early season and subsequent to the winter break. Sprain was the most common diagnosis with the Medial Collateral ligament affected in 23.2% of cases. 609 injuries met the UEFA Model criteria for major injury. In total 60,091 training days and 5,272 match appearances were lost through knee injury.

Knee injuries are common in elite level youth footballers and are often severe in nature, resulting in large amounts of training time lost to injury. Diagnosis of ligament sprain is common leading to prolonged time off, and may mask more serious pathology or inappropriate management.

Introduction

We wished to quantify the influence of constraint and various principal indications upon functional outcome following aseptic first time revision knee arthroplasty.

Purpose of the study

To compare the patellofemoral kinematics and patella stability of a new TKR, with a continuous radius versus an established J shaped knee system and the natural knee. It was hypothesised that the high performance new TKR would be a better match to the natural knee and anatomical patella tracking would provide a more stable patella.

During a retrospective case note analysis, a significant difference was found in prosthesis survival, between two cohorts of patients who underwent different total knee replacements. The first cohort included 70 patients who underwent Kinemax Plus total knee replacement, the second cohort included 58 patients who underwent PFC Total Knee replacement. All patients were under the care of one Consultant Orthopaedic Surgeon. Interestingly, the Kinemax Plus cohort was found to have a higher rate of revision compared to the PFC cohort. A detailed comparison was carried out between the two groups to identify any obvious cause for the disparity.

The two cohorts were found to be well matched with respect to age, sex, ASA grade, underlying pathology and operative technique. Median follow up being 6 years and 5 years for the Kinemax Plus and PFC groups respectively.

There were 11 failed prostheses in the Kinemax Plus cohort, 7 undergoing revision with the remaining 4 patients offered revision but unwilling to have surgery. Wear of the polyethylene tibial insert was the most obvious finding at revision, present in six of the seven revisions. 97% of the Kinemax Plus Prostheses were intact at 5 years but by 8 years only 87% were intact. There were no revisions performed in the PFC cohort.

Post-operative x-ray analysis was undertaken to rule out prosthesis malalignment as a cause for the increased failure rate. The coronal alignment of the prostheses (CAK) was calculated and all post operative x-rays were within the normal limits of 4-10 degrees.

Analysis of the explanted Kinemax Plus polyethylene liners was undertaken. In six cases, the polyethylene bearing surfaces displayed severe surface and subsurface delamination. This suggests massive fatigue and fatigue wear. Only one implant showed localised delamination.

These findings suggest the hypothesis of weak polyethylene particle interface strength.

The posterior drawer is a commonly used test to diagnose an isolated PCL injury and combined PCL and PLC injury. Our aim was to analyse the effect of tibial internal and external rotation during the posterior drawer in isolated PCL and combined PCL and PLC deficient cadaver knee.

Ten fresh frozen and overnight-thawed cadaver knees with an average age of 76 years and without any signs of previous knee injury were used. A custom made wooden rig with electromagnetic tracking system was used to measure the knee kinematics. Each knee was tested with posterior and anterior drawer forces of 80N and posterior drawer with simultaneous external or internal rotational torque of 5Nm. Each knee was tested in intact condition, after PCL resection and after PLC (lateral collateral ligament and popliteus tendon) resection. Intact condition of each knees served as its own control. One-tailed paired student's t test with Bonferroni correction was used.

The posterior tibial displacement in a PCL deficient knee when a simultaneous external rotation torque was applied during posterior drawer at 90° flexion was not significantly different from the posterior tibial displacement with 80N posterior drawer in intact knee (p=0.22). In a PCL deficient knee posterior tibial displacement with simultaneous internal rotation torque and posterior drawer at 90° flexion was not significantly different from tibial displacement with isolated posterior drawer. In PCL and PLC deficient knee at extension with simultaneous internal rotational torque and posterior drawer force the posterior tibial displacement was not significantly different from an isolated PCL deficient condition (p=0.54).

We conclude that posterior drawer in an isolated PCL deficient knee could result in negative test if tibia is held in external rotation. During a recurvatum test for PCL and PLC deficient knee, tibial internal rotation in extension results in reduced posterior laxity.

Introduction and Aims: Morbid obesity (BMI> 40) has been shown to cause increased perioperative morbidity and poorer long-term implant survivorship following total knee arthroplasty (TKA). The aim of this study was to determine the impact of morbid obesity on patient-reported outcomes following TKA.

Methods: Patients undergoing primary TKA were invited to complete questionnaires preoperatively and one year after surgery. Questionnaires include the WOMAC and SF-36 health status measures, demographics, self-reported comorbid medical conditions, height and weight. At follow-up, satisfaction with results of TKA is included. Patients were categorised by their preoperative BMI categories as ideal weight (20–25), overweight (> 25–30), obese (> 30–40) or morbidly obese (> 40). We used multivariate analysis to adjust for known significant correlates of WOMAC and SF-36, namely age, gender and comorbid medical conditions. Adjusted mean scores for each assessment were compared by BMI category.

Results: A total of 769 patients were included in the study which included 27 morbidly obese, 280 obese, 314 overweight and 148 ideal weight patients. Morbidly obese patients when compared with non-obese patients had significantly worse preoperative WOMAC pain and function and a trend for worse SF36 scores (Vitality significantly worse, p=0.04). There was no significant difference between the BMI categories at one year for WOMAC or SF-36 scores (trend for the Physical Functioning score to be lower, p=0.052). Morbidly obese patients were all satisfied with pain relief after surgery but were less satisfied with functional results when compared to the non-obese groups.

Discussion: This study shows that morbidly obese patients report significantly worse health status prior to TKA but their post-operative improvement is greater than the non-obese population. Although morbid obesity should not be an absolute contraindication to TKA, patients should be carefully selected balancing the risk of perioperative complications and earlier failure against the demonstrated marked improvement in quality of life.

There have been marked changes in the management of Juvenile Idiopathic Arthritis (JIA) over recent decades, mainly with earlier use of methotrexate (MTX). Our aim was to describe orthopaedic interventions in a large group of adults with JIA followed up over several decades.

This was a retrospective observational study of adult JIA patients attending a teaching hospital clinic, with information collated on JIA subtype, disease duration, orthopaedic interventions and exposure to MTX.

The study included 144 patients with median disease duration of 19 years. Survival analysis showed that joint surgery was observed in the majority (75%) of patients with disease duration over 40 years with a trend for less joint surgery in patients with oligoarticular JIA. In total 41 patients (28.5%) had received joint surgery and 17/41(41%) have required multiple procedures. Of those who have required joint surgery, 20/41(48%) had started MTX in their adult years, with only 5/41 (12%), starting MTX prior to first joint replacement and none within five years of disease onset. Of the patients who have not had joint surgery to date, most (46/103, 45%) were receiving MTX or another immunosuppressive agent, in the majority of cases MTX was started within two years of disease onset.

Many adults with JIA require joint replacement surgery and ongoing immunosuppressive treatments, emphasising that JIA is not a benign disease. Many patients who have had joint replacement surgery have had exposure to MTX albeit after many years after disease onset; it remains to be seen whether patients who have received MTX therapy early in their disease course will ultimately have less requirement for joint surgery.