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.

Objective: To ascertain the epidemiology of ankle injuries in elite youth football.

Design: Retrospective analysis of prospectively collected injury data from English Football Association Academies.

Setting: Forty-one FA Football Academies, between 1998 and 2006.

Participants: For the complete seasons studied, a total of 14776 players were registered from U9 to the U16 age category – a mean of 2463 players per year. All ankle injuries of sufficient severity to miss 48 hours or more training were studied – 2563 injuries in total.

Main outcome measurements: The incidence and burden of ankle injuries in this population, and factors associated with injury.

Results: There was a mean incidence of one ankle injury per player per year, and a mean of 20 training days and 2 matches were missed per ankle injury. Increased injury rates were seen in older players, in competition and later in each half of match time. Peaks in injury were observed early in the season and after the winter break. In competition, more injuries were associated with a contact situation than in training. Eighty-eight injuries (3.4%) required a lay-off of three months or more and in 18 (0.7%) cases, the player failed to return to training. In total, 52290 training days and 5182 match appearances were lost through ankle injury. The majority of injuries were sprains, but more severe injuries occurred accounted for 3.9% of the total.

Conclusions: Ankle injuries are common in young football players, and are often severe, with prolonged loss of training time. This has potential far reaching implications, both on and off the field. Further syudy in this area is suggested.

We have attempted to quantify the influence of clinical, radiological and prosthetic design factors upon flexion following knee replacement. Our study examined the outcome following 101 knee replacements performed in two prospective randomized trials using similar cruciate retaining implants. Multivariate analyses, after adjusting for age, sex, diagnosis and the type of prosthesis revealed that the only significant correlates for range of movement at 12-months were the difference in posterior condylar offset ratio (p< 0.001), tibial slope (p< 0.001) and preoperative range of movement (p=0.025). We found a moderate correlation between 12-month range of movement and posterior tibial slope (R=0.58) and the difference of post femoral condylar offset (that is, post-operative minus preoperative posterior condylar offset, R=0.65). Posterior condylar offset had the greatest impact upon final range of movement highlighting this as an important consideration for the operating surgeon at pre-operative templating when choosing both the design and size of the femoral component.

Introduction: Correct alignment in both coronal and sagittal planes has been shown to be associated with longevity of total knee arthroplasty. The majority of procedures are performed using an intramedullary rod with a femoral cutting jig, with a 5°–7° offset depending upon the anatomical and mechanical axes. The cutting jig rotates around the rod and therefore the rotational alignment of the jig will also affect the cut and final component position (in addition to the rod entry point). It is interesting that rotational alignment of the femoral component is often assessed after the distal resection has been made. The distal resection plane determines the final position of the femoral component, influences patellar tracking and medial/lateral, flexion/extension balancing. This study measures the resultant effect on the distal femoral resection when entry point and jig rotation are varied.

Materials and Methods: The distal femoral resection was carried out in sawbones with three different entry points (central, inferior and superolateral) in neutral alignment and rotations of 10° (internal and external) about the transepicondylar axis. The resulting plane of the cut was assessed by a graphical method measuring the changes in orientation of the alignment rod in space before and after the distal cut. A computer navigation system was used to measure the varus/valgus and flexion/extension angles of the distal cut. This experiment was done thrice, in a total of 27 sawbones and the average values were recorded.

Results: The results varied considerably in the sagittal plane with central and inferior entry points. Internal rotation of the jig around a central entry point produced hyperextension (mean 3.3°) and external rotation caused flexion (mean 1.8°). Using an inferior entry point, flexion of the distal plane improved from an average 3° in neutral rotation to 1.6° on internal rotation; external rotation worsened flexion to an average of 4.3°. The angles digressed in both sagittal and coronal planes with a superolateral entry point; rotations of the distal cutting jig caused hyperextension (maximum of 7.5°). Coronal alignment ranged from 4.5° of varus to 5° of valgus in neutral alignment and rotations around a superolateral entry point.

Conclusion: The study demonstrates that there is a possibility of a compound error from misplaced entry point and that malrotation prior to distal resection is real. This error would invariably be extrapolated in the subsequent steps of conventional knee arthroplasty. Computer assisted arthroplasty may have a role in avoiding this surgical error.

Surgical reconstruction of the injured Anterior Cruciate Ligament (ACL) is an effective solution to knee instability, but not all grafts incorporate well. The biological environment in the knee that controls graft integration is not well understood, and this study aims to fill that gap as the first step towards a translational approach to optimise outcomes.

Over two stages, tissue samples and knee fluid samples were harvested from patients undergoing ACL reconstruction. These samples were cultured and stored to allow batch analysis for a variety of cytokines, growth factors and collagenases.

Stage 1 (n=14) identified the presence of specific pro-inflammatory cytokines, growth factors and latent collagenase. Information gathered allowed a more targeted approach to be used in stage 2 (n=18). Stage 2 data from tissue cultures suggest that collagenase activity peaks later than 6 hours post-op. The relationships between collagenase activity and levels of TNF-alpha, IL-1beta and bFGF are of potential interest, and the profiles of patients will be compared with longer term follow-up data to determine any effects on outcomes.

Further detailed assessment of the biology of ACL graft incorporation is required, but these preliminary data have clarified some of the details worthy of further study.

The Kinemax Plus knee replacement has a reported 10 year survival of around 96%. However we found the survival rate of this implant in our cohort to be 75% at 9 years. No abnormalities were found for clinical and radiological parameters. At reoperation the most striking feature was that of significant ultra-high molecular weight polyethylene (UHMWPE) failure. Oxidative and structural analysis of the polyethylene components was therefore undertaken.

Ten Kinemax Plus tibial inserts were analysed; one was a shelf-aged unused implant, the others were explants. An FTIR analysis of the data showed that oxidation is present in all samples. The degree of oxidation however varied with depth and location. Except for a sharp oxidative peak approximately half way into the sample, the shelf aged samples had a fairly constant level of oxidation. The retrieved implants had an overall higher level of oxidation in both bearing and non-bearing regions. The latter had less of a variation in oxidation which implies that in vivo loading exaggerates the degree of oxidation. In the non-articulating regions oxidation of the explants was found to peak often at the region of about 40% from the bottom surface in all retrieved samples. By contrast, most articulating region had two oxidative peaks; one occurring at approximately 1–1.5mm from the surface, which is consistent with findings on subsurface oxidation, and another occurring about 2–3mm from the bottom surface.

SEM imaging provided evidence for the presence of fusion defects by indicating grain boundaries through-out the explants. This indicates a compromised material which is more susceptible to damage. Fatigue loading of the implant has also been seen to produce a subsurface stress maximum at approximately 1 to 2mm below the articulating surface. It is thought that maximum contact stresses within this region cause Type 1 and Type 2 defects to open or become more pronounced. This in turn will increase the local concentration of oxygenating material as it will be present in these defects and voids where surface areas are greater for oxidative reaction. We therefore hypothesise that these fusion defects are the cause for the early failure of the Kinemax implants.