Introduction

Anteromedial osteoarthritis of the knee (anteromedial gonarthrosis-AMG) is a common form of knee arthritis. In a clinical setting, knee arthritis has always been assessed by plain radiography in conjunction with pain and function assessments. Whilst this is useful for surgical decision making in bone on bone arthritis, plain radiography gives no insight to the earlier stages of disease. In a recent study 82% of patients with painful arthritis had only partial thickness joint space loss on plain radiography. These patients are managed with various surgical treatments; injection, arthroscopy, osteotomy and arthroplasty with varying results. We believe these varying results are in part due to these patients being at different stages of disease, which will respond differently to different treatments. However radiography cannot delineate these stages. We describe the Magnetic Resonance Imaging (MRI) findings of this partial thickness AMG as a way of understanding these earlier stages of the disease.

Introduction

Anteromedial gonarthrosis is a common well described pattern of knee osteoarthritis with cartilage wear beginning in the anteromedial quadrant of the medial tibial plateau in the presence of an intact and functioning ACL. It is well known that mechanical factors such as limb alignment and meniscal integrity affect the progression of arthritis and there is some evidence that the morphology of the tibial plateau may be a risk factor in the development of this disease. The extension facet angle is the angle of the downslope of the anterior portion of the medial tibial plateau joint surface in relation to the middle portion on a sagittal view. If this is an important factor in the development of AMG there may be potential for disease modifying intervention.

This study investigates if there is a significant difference in this angle as measured on MRI between a study cohort with early AMG (partial thickness cartilage damage and intact ACL) and a comparator control cohort of patients (no cartilage damage and ACL rupture).

Introduction

The results of the mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing with a five year survival of 82%. Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to high dislocation rate, all occurring in the first year. A detailed analysis of the causes of bearing dislocation confirmed the elevated lateral tibial joint line to be a contributory factor. A new surgical technique was therefore introduced in which care was taken neither to remove too much bone from distal femur nor to over tighten the knee and thus ensure that the tibial joint line was not elevated. Other modifications to the technique were also introduced including use of a domed tibial component.

Introduction

Total knee arthroplasty (TKA) accounts for 84% of all knee replacement surgery in the UK (NJR 2009) despite published epidemiological data showing that single compartment disease is most prevalent. We investigated this incompatibility further by describing the compartmental pattern and stage of cartilage loss of all patients with osteoarthritis (OA) presenting to a specialist knee clinic over one year.

We obtained information from the Elective Orthopaedic Centre on 1523 patients with baseline and six-month Oxford hip scores (OHS) after undergoing primary hip replacement (THR) and 1784 patients with Oxford knee scores (OKS) for primary knee replacement (TKR) who completed a six-month satisfaction questionnaire.

Receiver operating characteristic curves identified an absolute change in OHS of 14 points or more as the point that discriminates best between patients’ satisfaction levels and an 11-point change for the OKS. Satisfaction is highest (97.6%) in patients with an absolute change in OHS of 14 points or more, compared with lower levels of satisfaction (81.8%) below this threshold. Similarly, an 11-point absolute change in OKS was associated with 95.4% satisfaction compared with 76.5% below this threshold. For the six-month OHS a score of 35 points or more distinguished patients with the highest satisfaction level, and for the six-month OKS 30 points or more identified the highest level of satisfaction. The thresholds varied according to patients’ pre-operative score, where those with severe pre-operative pain/function required a lower six-month score to achieve the highest levels of satisfaction.

Our data suggest that the choice of a six-month follow-up to assess patient-reported outcomes of THR/TKR is acceptable. The thresholds help to differentiate between patients with different levels of satisfaction, but external validation will be required prior to general implementation in clinical practice.

Objectives

Surgical marking during tendon surgery is often used for technical and teaching purposes. This study investigates the effect of a gentian violet ink marker pen, a common surgical marker, on the viability of the tissue and cells of tendon.

Purpose of study

To investigate the linear penetration rate of the polyethylene bearing in unicompartmental knee arthroplasty at twenty years.

Introduction

Obesity has been considered a relative contra-indication in unicompartmental knee arthroplasty (UKA) due to fear of high wear rates, loosening and tibial collapse. The aim of this study was to investigate the impact of high body mass index (BMI) on ten-year survivorship and five-year functional outcome after Oxford UKA, a fully congruous mobile bearing design with large contact area and low wear rate.

Objective

To investigate the effect of lab-based simulator training, on the ability of surgical trainees to perform diagnostic knee arthroscopy.

Purpose of Study

To assess the incidence of radiolucency in cemented and cementless Oxford unicompartmental knee replacement at two years.

Introduction

Kozinn and Scott have made recommendations about contra-indications for unicompartmental knee replacement (UKR). They suggest that patients younger than 60, weight > 82 kilograms, patients with exposed bone in patella-femoral compartment or patients who are physically active/perform heavy labour should not be offered a UKR. In addition, chondrocalcinosis is a contra-indication. These strict selection criteria are based on the experience with fixed bearing UKAs and are more intuitive than evidence based. The Oxford UKR has a fully congruous mobile bearing and has been shown to have minimal wear. Over the past 25 years, the Oxford Group has followed a standardised protocol for patient selection for UKR. We ignore patella-femoral joint pathology, chondrocalcinosis, patient's age, weight and activity level when deciding the suitability for UKR.

Aim

A case series with functional and radiographic outcomes, of modular endoprosthetic distal femoral replacement in complex cases of periprosthetic fracture.

We obtained pre-operative and six-month post-operative Oxford hip (OHS) and knee scores (OKS) for 1523 patients who underwent total hip replacement and 1784 patients who underwent total knee replacement. They all also completed a six-month satisfaction question.

Scatter plots showed no relationship between pre-operative Oxford scores and six-month satisfaction scores. Spearman’s rank correlation coefficients were -0.04 (95% confidence interval (CI) -0.09 to 0.01) between OHS and satisfaction and 0.04 (95% CI -0.01 to 0.08) between OKS and satisfaction. A receiver operating characteristic (ROC) curve analysis was used to identify a cut-off point for the pre-operative OHS/OKS that identifies whether or not a patient is satisfied with surgery. We obtained an area under the ROC curve of 0.51 (95% CI 0.45 to 0.56) for hip replacement and 0.56 (95% CI 0.51 to 0.60) for knee replacement, indicating that pre-operative Oxford scores have no predictive accuracy in distinguishing satisfied from dissatisfied patients.

In the NHS widespread attempts are being made to use patient-reported outcome measures (PROMs) data for the purpose of prioritising patients for surgery. Oxford hip and knee scores have no predictive accuracy in relation to post-operative patient satisfaction. This evidence does not support their current use in prioritising access to care.

Introduction: Although originally designed to aid the management of primary malignant bone tumours, the indications for modular endoprosthetic replacement (EPR) have expanded to include complex periprosthetic fractures and failed internal fixation. The incidence of these challenging cases is increasing with an aged population. We reviewed retrospectively our experience with the use of EPR in patients who had undergone limb salvage following complex trauma presentations.

Methods: Between 2003 and 2008 twenty one patients presented with complex trauma related problems and underwent EPR at a specialist tertiary referral centre. The mean age was 71 years (range 44–87) and the median number of previous surgical procedures was 3 (range 0–11). Eight patients presented following failed internal fixation of proximal femoral fractures. Nine patients had periprosthetic fractures around joint arthroplasties, seven relating to total knee replacements (TKRs) and two to total hip replacements (THRs). One case of periprosthetic fracture around THR had undergone failed internal fixation. Two patients had distal femoral fractures, of which one was infected and had undergone failed internal fixation, while the other was unrecon-structable. Two patients had proximal tibia fractures which had both undergone failed internal fixation.

Results: The mean Harris Hip Score was 89.5 (range 64–85) at a mean follow up period of 8 months (minimum 4 months). The mean American Knee Society Score was 82 (range 62–100) and the mean functional score was 62 (range 30–75) at a mean follow up period of 6 months (minimum 2 months). Complications included two cases of deep infection; one resulted in a two stage revision procedure, while the other retained the EPR following a washout.

Discussion: Modular EPR in the lower limb is a durable reconstructive option in complex trauma problems, particularly in the elderly and those patients with significant bone loss. Preliminary functional results indicate very satisfactory results.

Introduction: Approximately 20% of unicompartmental knee replacement (UKR) revisions are related to polyethylene wear. The Phase 1 Oxford UKR was introduced as a design against wear, with a fully congruent mobile bearing. The Phase 2 implant was introduced with new instrumentation (femoral mill) and changes to the bearing shape (lower anterior wall) to reduce the incidence of anterior impingement. We have previously shown that the Oxford UKR has a wear rate of 0.02 mm/year at ten years, in well functioning devices, but that higher wear rates can be seen with impingement or if the congruous articulation is lost. The aim of this study was to determine the 20 year in-vivo wear of the Oxford Phase 1 and Phase 2 UKR, using Roentgen Stereophotogrammetric Analysis (RSA).

Method: We measured the in-vivo wear of 6 Phase 1 (5 patients, mean age 65.24 years) and 7 Phase 2 (4 patients, mean age 63.43) Oxford UKR bearings. Average time since surgery was 22.37 years and 19.46 years for the Phase 1 and Phase 2 implants respectively. Selection criteria included patients who were mobile, with an exercise tolerance greater than 100m as per the American Knee Society Score (AKSS) functional questionnaire. RSA x-rays were taken with the knee in the normal anatomical position on standing and with the knee flexed to 30o. The Oxford knee score (OKS) and AKSS were gained at the RSA examination. Phase 1 and 2 components were reverse engineered by laser scanning, and converted to CAD models. The CAD models of the tibia and femur were pose-estimated in the RSA software (Medis Specials, Leiden, Netherlands). A sphere was fit to the femoral component and the minimum bearing thickness was determined by measuring the shortest perpendicular distance between the sphere and the plane contained on the tibial tray articular surface. The linear wear for each bearing was calculated by subtracting the measured thickness from the corrected nominal bearing thickness. Non-parametric statistics were used to compare the two Phases.

Results: There was no significant difference in age, OKS and AKSS between the two groups. The median wear rate was 0.078 mm/year for Phase 1 and 0.023 mm/year for Phase 2. This difference was statistically significant (p = 0.027).

Discussion: The difference in wear rate is explained by impingement in Phase 1, which was reduced by design changes with the introduction of Phase 2; the Phase 2 is designed to avoid impingement between the femur and the bearing. This study demonstrates that very low wear rates can be maintained with the Phase 2 implant to the end of the second decade after implantation. This is of particular importance when the device is used in younger patients and demonstrates that the Oxford UKR can be a definitive implant for the treatment of isolated compartmental osteoarthritis.

Introduction: Anteromedial gonarthrosis is a common well described pattern of knee osteoarthritis with cartilage wear beginning in the anteromedial quadrant of the medial tibial plateau in the presence of an intact and functioning ACL. It is well known that mechanical factors such as limb alignment and meniscal integrity affect the progression of arthritis and there is some evidence that the morphology of the tibial plateau may be a risk factor in the development of this disease. The extension facet angle is the angle of the downslope of the anterior portion of the medial tibial plateau joint surface in relation to the middle portion on a sagittal view. If this is an important factor in the development of AMG there may be potential for disease modifying intervention.

This study investigates if there is a significant difference in this angle as measured on MRI between a study cohort with early AMG (partial thickness cartilage damage and intact ACL) and a comparator control cohort of patients (no cartilage damage and ACL rupture).

Methods: 3 Tesla MRI scans of 99 patients; 54 with partial thickness cartilage damage and 44 comparitors with no cartilage damage (acute ACL rupture) were assessed. The extension facet angle was measured (Osirix v3.6) using a validated technique on two consecutive MRI T2 sagittal slices orientated at the mid-coronal point of the medial femoral condyle. (InterClass Correlation 0.95, IntraClass Correlation 0.97, within subject variation of 1.1° and coefficiant of variation 10.7%). The mean of the two extension angle values was used. The results were tabulated and analysed (R v2.9.1).

Results: Of the 99 knees, 38 were female and 61 male; 44 left knees and 55 right. The mean extension facet angle for the partial thickness group was 12.7° (SD 3.35) and for the comparator group 8.7° (SD 3.09). There was a significant difference between these 2 groups (Mann Whitney U, p< 0.001). Although there were significantly more men than women in the comparator group, stratification analysis showed that there was no effect of gender on the mean extension facet angle.

Discussion: There is a significance difference in the extension facet angle between patients with AMG with only partial thickness cartilage loss and a comparator group. This has not been shown in a study group of this size before. Since none of the subjects had full thickness cartilage loss it is unlikely that this difference is due to bone attrition changing the angle as part of the disease process but this is an important area for further study. We believe that a higher medial tibial extension facet angle alters the mechanics within the medial compartment, placing these patients at higher risk of developing AMG. This may present an opportunity for risk factor modification, for example osteotomy.

Introduction: Partial Knee Replacement (PKR) is an appealing alternative to Total Knee Replacement (TKR) when the patient has isolated compartment osteoarthritis (OA). In nearly all cases there is a radiolucency observed between the tibial tray wall and the boney interface. The reasons why radiolucencies appear are unknown, but the bone will adapt to its altered mechanical environment by bone remodelling in accordance with ‘Wollf’s Law’. The aim of this study was to investigate the mechanical environment of the tibia bone adjacent to the tray wall, following cemented and cementless PKR, in order to determine whether this region of bone resorbs.

Methods: A validated finite element (FE) model of a cadaver tibia implanted with an Oxford PKR was used in this study. Kinematic data from fluoroscopy measurements during a step-up activity were used to determine the relative tibio-femoral positioning for the Oxford PKR model. Load data were adapted from the in-vivo measured loads using an instrumented implant during a step-up activity. The standard operating protocol was simulated for the Oxford PKR FE models, with the tibial tray implanted in a neutral position. The tibia was sectioned around the tray. Zone 7 was defined as parallel to the vertical tray wall, corresponding to the region on screened x-rays where radiolucencies are observed. It was assumed that the bone in the implanted tibia will attempt to normalise its stress-strain patterns locally to its equilibrium state, the intact tibia, for the same loading conditions. Forty patients (20 cemented, 20 cementless) who had undergone PKR were randomly selected from a database, and their screened x-rays assessed for radiolucency in region 7.

Results: The SED in region 7 was 80% lower in the cemented and cementless tibia, compared to the intact tibia (Figure 2). The maximum tensile stress was 63% lower in the cemented and cementless tibia, compared to the intact tibia. The corresponding maximum compressive stress was 52% lower. Radiolucency was observed in all forty radiographs in region 7.

Discussion: After implantation with a cemented or cementless PKR the bone strains and SED in region 7 are reduced. This reduction may provide the signal for adaptive bone remodelling and bone will be resorbed from this region, decreasing the volume and increasing the SED. Bone resorption will continue until the equilibrium state is reached. If a ‘lazy’ zone between 35% and 50% of the remodelling signal is considered, bone resorption will still occur due to the large decrease in SED for this region. For region 7 to return its SED to the equilibrium state, its volume will need to be reduced by 80%. This is likely to be the reason why a radiolucency is observed clinically in this region in almost every case, whether a cemented or cementless implant is used.

Introduction: Although originally designed to aid the management of primary malignant bone tumours, the indications for modular endoprosthetic replacement (EPR) have expanded to include complex periprosthetic fractures and failed internal fixation. The objective of this study was to evaluate the success of endoprosthetic replacement (EPR) in patients who had undergone limb salvage following complex trauma presentations.

Materials and Methods: Between 2003 and 2008 twenty one patients presented with complex trauma related problems and underwent EPR at a specialist tertiary referral centre. The mean age was 71 years (range 44–87) and the median number of previous surgical procedures was 3 (range 0–11). Eight patients presented following failed internal fixation of proximal femoral fractures. Nine patients had periprosthetic fractures around joint arthroplasties, seven relating to total knee replacements (TKRs) and two to total hip replacements (THRs). One case of periprosthetic fracture around THR had undergone failed internal fixation. Two patients had distal femoral fractures, of which one was infected and had undergone failed internal fixation, while the other was unreconstruc-table. Two patients had proximal tibia fractures which had both undergone failed internal fixation.

Results: The mean Harris Hip Score was 89.5 (range 64–85) at a mean follow up period of 8 months (minimum 4 months). The mean American Knee Society Score was 82 (range 62–100) and the mean functional score was 62 (range 30–75) at a mean follow up period of 6 months (minimum 2 months). Complications included two cases of deep infection; one resulted in a two stage revision procedure, while the other retained the EPR following a washout.

Conclusion: Modular EPR in the lower limb is a durable reconstructive option in complex trauma problems, particularly in the elderly and those patients with significant bone loss. Preliminary functional results indicate very satisfactory results.

The results of mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing (five-year survival: 82%). Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to a high dislocation rate. A detailed analysis confirmed the elevated lateral tibial joint line to be a contributory factor to bearing dislocation. A new surgical technique was therefore introduced in which care was taken neither to remove too much bone from the distal femur nor to over tighten the knee and therefore ensure that the tibial joint line was not elevated. Other modifications included use of a domed tibial component.

The aim of this study is to compare the outcome of these iterations: the original series (series I), those with improved surgical technique (series II) and the domed tibial component (series III). The primary outcome measure was bearing dislocation at one year. One year was chosen as all the dislocations in the first series occurred within a year. In the original series (n=53), implanted using a standard open approach, there were six dislocations in the first year, the average flexion 110°, and 95% had no/mild pain on activity. In the second series (n=65), there were 3 dislocations, the average flexion was 117°, and 80% had no/mild pain on activity.

In the third series with the modified technique and a convex domed tibial plateau, there was one dislocation, average flexion was 125° and 94% had no/mild pain on activity. At four years the cumulative primary dislocation rates were 10%, 5% and 0% respectively, and were significantly different (p=0.04).

The improved surgical technique and implant design has reduced dislocation rate to an acceptable level so a mobile bearing can now be recommended for lateral UKR.

About ten years ago we introduced sophisticated instrumentation and an increased range of component sizes for the Oxford unicompartmental knee replacement (UKR) to facilitate a minimally invasive surgical (MIS) approach. The device is now routinely implanted through an incision from the medial pole of the patella to the tibial tuberosity. This has resulted in a more rapid recovery and an improved functional result. As the access to the knee is limited there is a concern that the long term results may be compromised. The aim of this study was to determine the 10 year survival.

A prospective follow up of all Phase 3 minimally invasive Oxford UKR implanted by two senior authors (DWM & CAFD) has been undertaken. So far 1015 UKRs have been implanted for anteromedial osteoarthritis. All patients received a cemented implant through a MIS approach and were followed up prospectively by an independent observer. The data was collected prospectively regarding pre-operative status, complications and clinical as well as functional outcome at predetermined intervals.

The average age of patients was 66.4 years (range: 33 – 88) with mean Oxford Knee Score 41 (SD: 7.9) at the time of last follow up, Knee Society Score (objective) of 84 (SD: 13) and Knee Society Score (functional) of 83 (SD: 21). At ten years the survival of this cohort is 96%. There were 22 revisions including 7 for progression of arthritis, 5 for infection, 5 for bearing dislocation, 4 for unexplained pain and one for rupture of ACL secondary to trauma.

We conclude that the Oxford Knee can be implanted reliably through a minimally invasive approach, giving excellent long term results.

Our aim was to investigate the molecular features of progressive severities of cartilage damage, within the phenotype of Anteromedial Gonarthrosis (AMG).

Ten medial tibial plateau specimens were collected from patients undergoing unicompartmental knee replacements. The cartilage within the area of macroscopic damage was divided into equal thirds: T1(most damaged), to T3 (least damaged). The area of macroscopically undamaged cartilage was taken as a 4th sample, N. The specimens were prepared for histological (Safranin-O and H& E staining) and immunohistochemical analysis (Type I and II Collagen, proliferation and apoptosis). Immunoassays were undertaken for Collagens I and II and GAG content. Real time PCR compared gene expression between areas T and N.

There was a decrease in OARSI grade across the four areas, with progressively less fibrillation between areas T1, T2 and T3. Area N had an OARSI grade of 0 (normal). The GAG immunoassay showed decreased levels with increasing severity of cartilage damage (p< 0.0001). There was no significant difference in the Collagen II content or gene expression between areas. The Collagen I immunohistochemistry showed increased staining within chondrocyte pericellular areas in the undamaged region (N) and immunoassays showed that the Collagen I content of this macroscopically and histologically normal cartilage, was significantly higher than the damaged areas (p< 0.0001). Furthermore, real time PCR showed a significant increase in Collagen I expression in the macroscopically normal areas compared to the damaged areas (p=0.04).

In AMG there are distinct areas, demonstrating progressive cartilage loss. We conclude that in this phenotype the Collagen I increase, in areas of macroscopically and histologically normal cartilage, may represent very early changes of the cartilage matrix within the osteoarthritic disease process. This may be able to be used as an assay of early disease and as a therapeutic target for disease modification or treatment.

Introduction: This study explores whether modern magnetic resonance imaging (MRI) with improved cartilage sequencing is able to show a more detailed view of antero-medial osteoarthritis of the knee (AMOA) than previously, so enabling a radiographic description of this common phenotype of disease. Modern MRI technology allows us to visualize in great detail the structures and cartilage within the knee, providing a better understanding of the pathoanatomy of AMOA. This description of the end stage of disease is useful as a baseline when investigating the progression of arthritis through the knee. Preoperative assessment of patients and selection of intervention is very important and preoperative imaging forms an integral part of this. This will also be useful in preoperative assessment and surgical management of patients.

Methods: 50 patients with a radiographic diagnosis of anteromedial osteoarthritis of the knee and had been listed for unicompartmental knee arthroplasty (UKA) had MRI as part of their pre-op workup. At operation all were deemed suitable for UKA using the current Oxford indications. The image sequences were coronal, axial and sagittal with a predetermined cartilage protocol. The state of the ACL, cartilage wear degree and location, presence and pattern of osteophytes, meniscal anatomy and subchondral high signal were assessed.

Results: All the ACLs were visualized and in continuity, however 40% showed intrasubstance high signal. 100% of medial compartments showed full thickness anteromedial loss with preservation of the posteromedial cartilage. When present, the meniscus was extruded in 75% of cases.

90% of lateral compartments were normal and none had full thickness cartilage loss. However 10% showed high signal in the tibial plateau. There was a highly reproducible pattern of osteophyte formation; 94% posteromedial and posterolateral aspect of medial femoral condyle; 90% medial tibial; 80% medial femoral and 84% lateral intercondylar notch.

Discussion: This study maps the pattern of anteromedial osteoarthritis using modern MRI techniques. This creates a baseline description of disease which is useful when investigating disease progression. This also has importance in determining preoperative indications (preservation of ACL and posteromedial cartilage); surgical technique (determine pattern of osteophytes requiring resection) and potentially important for long-term outcome (early lateral compartment changes).

Introduction: Anteromedial gonarthrosis (AMG) is a distinct phenotype of osteoarthritis (OA), with a specific pattern of disease. There is full thickness cartilage loss anteromedially, progressing to an area of damaged cartilage, and then to an area of macroscopically and histologically normal cartilage posteriorly. It can be considered to be a spatial model of OA progression. Apoptosis, or chondrocyte cell death, has been shown to be a feature of OA cartilage, however the triggers are poorly understood; similarly, reactive oxygen species (ROS) have been implicated in OA. They have never been studied in a replicable topographical model of OA. This study characterises the regional levels of cell death and implicated ROS in AMG using a number of immunohistochemical studies.

Method: Ten tibial resection specimens were obtained from patients undergoing unicompartmental knee arthroplasty. Eight above knee amputations (from patients with peripheral vascular disease) were used as age matched controls. Cross sections taken through all regions were paraffin embedded. Routine histology was performed and immunohistochemical studies were conducted for Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), Active Caspase 3, Cytochrome C, Active Bax, Bim, 3-Nitrotyrosine and Forkhead Box O3A (FOXO 3A).

Results: Cell death, as detected by TUNEL appeared predominantly in the surface layer of chondrocytes of damaged cartilage (p< 0.001). Median values were 23% in superficial cartilage (range 0 – 51) compared to 0% in deeper cartilage (range 0 – 15). There was a significant difference in TUNEL staining between regions (p=0.001). This ranged from 26% (most damaged) to 4% (undamaged). There was a good correlation with degree of cartilage damage (ρ=0.66, p< 0.001) asdefined by histological grade and TUNEL was significantly higher (p< 0.001) in AMG compared to the control samples which showed an average of 2% TUNEL overall. Upstream markers of apoptosis (Active Caspase 3, Cytochrome C, Active Bax), assessed qualitatively, were present in a similar distribution to that of TUNEL staining. 3-Nitrotyrosine was also shown to be a predominantly surface phenomenon. There was a significant difference (p< 0.001) between regions, ranging from 58% (most damaged) to 10% (undamaged). Again, this was significantly higher that the control samples (p< 0.001). In line with indicators of ROS mediated damage, Bim and FOXO3A were also detected.

Discussion: The mechanism of apoptosis in OA cartilage has not been studied in depth, and understanding the biochemical and molecular responses of ‘stressed’ chondrocytes may provide invaluable information about the specific causes of cell death. Such cellular responses may provide targets for disease modification, thus delaying or preventing the need for joint arthroplasty. We conclude that AMG is a phenotype demonstrating cartilage at progressive stages of disease. Apoptosis involves the intrinsic mitochondrial pathway and ROS appear to be implicated. Further work is needed to provide evidence of what lies further upstream of markers demonstrated in this study.

Introduction: Most unicompartmental knee replacements (UKRs) employ cement for fixation of the prosthetic components to the bone. The information in the literature about the relative merits of cemented and cementless UKR is contradictory, with some favouring cementless fixation while others favouring cemented fixation. There is concern about the radiolucency which frequently develops around the tibial component with cemented fixations. The exact cause of the occurrence of radiolucency is unknown but according to some, it may suggest suboptimal fixation.

Method: Following ethical approval, 62 patients with medial OA were randomised to receive either cemented (n=31) or cementless components (n=31). All patients underwent identical surgical procedure with either a cemented or cementless Oxford UKR. Patients were assessed clinically and radiologically. The x-rays were taken with an image intensifier (I.I.). The position of the I.I. was adjusted until it was perfectly aligned with the tibial bone-implant interface thereby allowing accurate assessment of presence and extent of the radiolucency.

Results: The patients in the two groups were well matched. There was no significant difference in the clinical scores between the two groups. The mean OKS for the cemented group was 40 (± 8.3) and 42 (± 4.6) for cementless group. Narrow radiolucent lines were seen at the bone-implant interfaces of 75% of the cemented tibial components; partial in 43% and complete in 32%. In the cementless implants, partial radiolucencies were seen in 7% and complete radiolucencies in none. The differences are statistically highly significant (p< 0.0001) and imply satisfactory bone ingrowth into the cementless implants.

Conclusions: The method of fixation influences the incidence of radiolucency. With identical designs, no patient with cementless components developed any complete radiolucency. The observation raises the question as to whether cementless rather than cemented components should be routinely used for UKR.

Purpose: The purpose of this study was to report the mid-term survival results of Oxford UKAs in patients of 50 years of age or less, using (1) revision surgery and (2) Oxford Knee Scores (OKS) as outcome measures.

Method: A literature review identified studies of Oxford mobile bearing UKAs containing individuals 1) 50 years old or less with 2) medial osteoarthritis and 3) 2 years or longer follow-up. Authors were approached to participate in a multi-centre survival analysis by submitting all their patients, 50 years of age or less, who received a medial UKA for osteoarthritis. Patients who had died, been lost to follow-up or who underwent revision were identified. OKS were established for all patients with surviving implants.

Results: Seven centres submitted 107 patients. The mean age was 47 years (range 32–50). The average follow-up was 4 years (range 1–25). Forty-seven patients had follow-up into their fifth year or longer. The cumulative 7-year survival using revision as the endpoint was 96% (CI 8). The mean post-operative OKS for surviving implants was 38 (CI 2) out of a possible 48.

Conclusion: While early survival rates and function are encouraging, long-term follow-up is required before concluding UKA is a viable treatment option in young patients with unicompartmental knee arthritis.

Inflammatory changes in synovial tissues occur commonly in knee osteoarthritis (OA) and are termed “inflammatory OA”. The pathogenic significance of this inflammatory OA is uncertain. It is also not known whether inflammatory changes in the synovial membrane are reflected in the synovial fluid (SF) and whether the SF contains a similar inflammatory cell infiltrate.

This study examined 34 cases of knee joint OA and cytologically and immunohistochemically characterised inflammatory cells in the synovial membrane and SF. Specimens of SF and synovial membrane were taken at the time of knee arthroplasty.

All cases of inflammatory OA synovium contained (CD68+) macrophages; several cases also contained a scattered, focally heavy (CD3+) lymphocytic infiltrate and occasional lymphoid aggregates. Inflammatory changes in OA SF reflected this cell composition with numerous CD68+ macrophages and CD3+ lymphocytes being noted in inflammatory OA cases. The SF volume was greater (> 5ml) in cases of inflammatory OA. Non-inflammatory OA knee joints contained very few inflammatory cells, which were mainly macrophages, in both the synovial membrane and SF.

Our findings indicate that inflammatory changes in the synovial membrane of OA knee joints are reflected in the SF and that the volume of SF is commonly increased in cases of inflammatory OA. Both macrophages and lymphocytes in the inflammatory infiltrate of knee joint SF may contribute to joint destruction in OA by providing mononuclear phagocyte osteoclast precursors and the production of inflammatory cytokines and growth factors that promote osteoclastogenesis.

In conclusion, the cytology of SF and synovitic membrane are similar in inflammatory OA. With knee effusions of greater than 5mls and inflammatory synovitic membrane consideration of total knee arthoplasty in the presence of single compartment disease should be considered because of the risk of further joint destruction.

Introduction: This study explores whether modern magnetic resonance imaging (MRI) with improved cartilage sequencing is able to show a more detailed view of anteromedial osteoarthritis of the knee (AMOA). Preoperative assessment of patients and selection of intervention is very important and preoperative imaging forms an integral part of this. Modern MRI technology may allow us to visualize in great detail the structures and cartilage within the knee, providing a better understanding of the pathoanatomy of AMOA. This will be useful in preoperative assessment and surgical management of patients.

Methods: 50 patients with a radiographic diagnosis of anteromedial osteoarthritis of the knee and had been listed for unicompartmental knee arthroplasty (UKA) had MRI as part of their pre-op workup. At operation all were deemed suitable for UKA using the current Oxford indications. The image sequences were coronal, axial and sagittal with a predetermined cartilage protocol. The state of the ACL, cartilage wear location and pattern, presence of osteophytes and subchondral high signal were assessed.

Results: All the ACLs were visualized and in continuity, however 40% showed intrasubstance high signal.

100% of medial compartments showed full thickness anteromedial loss with preservation of the posteromedial cartilage. When present, the meniscus was extruded in 96% of cases.

Discussion: This study maps the pattern of anteromedial osteoarthritis using modern MRI techniques. This has importance in determining preoperative indications (preservation of ACL and posteromedial cartilage); surgical technique (determine pattern of osteophytes requiring resection) and potentially important for long-term outcome (early lateral compartment changes).

Introduction: Viscosupplementation is an effective treatment for patients suffering from knee osteoarthritis (OA). Most available products use 3 or 5 injection regimens. The objective of this study was to compare the safety and efficacy of a single 6 mL intra-articular administration of hylan G-F 20 with placebo.

Methods: In this prospective, multicenter, randomized, double-blind study, patients diagnosed with knee OA were randomized to one 6-mL injection of hylan G-F 20 or saline. The primary efficacy analysis (WOMAC A) was performed on the intent-to-treat population and was based on a repeated-measures model over the 26 weeks of the study. The incidence of adverse events (AEs) was collected over the study duration

Results: 253 patients were randomized to hylan G-F 20 (n=124) or placebo (n=129). Mean age was 63 years (42–84), BMI 29.4 (19.5–52.4 kg/m2), 71% were female, and all had primary knee OA of Kellgren Lawrence grade 2 (45%) or 3 (55%). Patients in the hylan G-F 20 group experienced a mean change from baseline in their WOMAC A Likert pain score (0–4 scale) over 26 weeks (primary efficacy criteria) of −0.84, which was statistically significantly different from the change reported in the placebo group (−0.69, p=0.047). Statistically significant differences favoring hylan G-F 20 were also reported for most of the secondary efficacy criteria: WOMAC A1 (estimate Odds Ratio over 26 weeks placebo/hylan G-F 20, 0.64, p=0.013), patient global assessment (0.69, p=0.029), and clinical observer global assessment (0.71, p=0.041); WOMAC B and C changes were not statistically significant between groups. There was no statistically significant difference in the use of rescue medication between the 2 groups. There were no serious AEs related to treatment. In the target knee, injection-related AEs occurred in 4.9% and 3.1% of patients for hylan G-F 20 and placebo, respectively, and treatment-related AEs occurred in 3.3% and 0.8% of patients, respectively. All target knee AEs were local pain, with or without joint swelling or effusion, and were of mild or moderate intensity.

Conclusion: This double-blind placebo-controlled study showed one injection of hylan G-F 20, possibly repeated 6 months later, was safe and provided symptomatic relief lasting up to 6 months in patients with knee OA.

Statement of purpose: The aim of this study is to evaluate different designs of unicompartmental knee replacement (UKR) by comparing the peak von Mises and contact stresses in polyethylene (PE) bearings over a step-up activity.

Summary of Methods: A validated finite element (FE) model was used in this study. Three UKR designs were modelled: a spherical femoral component with a spherical PE bearing (fully-congruent), a poly-radial femoral component with a concave PE bearing (semi-congruent), and a spherical femoral component with a flat bearing (non-congruent).

Kinematic data from in-vivo fluoroscopy measurements during a step-up activity was used to determine the relative tibial-femoral position as a function of knee flexion angle for each model. Medial and lateral force distribution was adapted from loads measured in-vivo with an instrumented implant during a step-up activity. The affect that varying the bearing thickness has on the stresses in the bearing was investigated. In addition, varus-valgus mal-alignment was investigated by rotating the femoral component through 10 degrees.

Summary of Results: Only the fully congruent bearing experienced peak von Mises and contact stresses below the PE lower fatigue limit (17MPa) for the step-up activity (fully congruent PE peak contact stress, 5MPa). The highest PE contact stresses were observed for the semi-congruent and non-congruent designs, which experienced approximately 3 times the PE lower fatigue limit. Peak PE von Mises stresses for the semi-congruent and non-congruent designs were similar, peaking at approximately 25MPa. Peak PE von Mises stresses were ameliorated with increased bearing thickness. Varus-valgus mal-alignment had little effect on the peak stresses in the three UKR designs.

Statement of Conclusions: Fully congruent articulating surfaces significantly reduce the peak contact stresses and von Mises stresses in the bearing. The FE model demonstrates that fully congruent bearings as thin as 2.5mm can be used without increasing the contact stresses significantly. Fully congruent designs can use thinner bearings and enable greater bone preservation.

Introduction: The results of the mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing with a five year survival of 82%. Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to high dislocation rate, all occurring in the first year. A detailed analysis of the causes of bearing dislocation confirmed the elevated lateral tibial joint line to be a contributory factor. A new surgical technique was therefore introduced in which care was taken neither to remove too much bone from the distal femur nor to over tighten the knee and therefore ensure that the tibial joint line was not elevated. Other modifications to the technique were also introduced including use of a domed tibial component.

Aim: The aim of this study is to compare the outcome of these iterations: the original series [series I], Series II with improved surgical technique and the domed tibial component [Series III].

Method: The primary assessment of outcome was bearing dislocation at one year. One year was chosen as all the dislocations in the first series occurred within a year. In series I, there were 53 knees, in series II 65 knees and in series III 60 knees, all with a minimum of one year follow up.

Results: In series I, there were 6 bearing dislocations (11%) and the average range of movement (ROM) was 110°. In the second series, there were 2 dislocations (3%) and the average ROM was 118°. In the third series, there were no primary dislocations and the average ROM was 125°.

Conclusions: The improved surgical technique and implant design has reduced the dislocation rate to an acceptable level so a mobile bearing can now be recommended for lateral UKR.

Statement of purpose: Finite element (FE) models of bone can be used to evaluate new and modified knee replacements. Validation of FE models is seldom used, and the quantification of modelling parameters has a considerable effect on the results obtained. The aim of this study is to develop a FE model of a cadaveric tibia and validate it against a comprehensive set of experiments.

Summary of Methods: Seventeen tri-axial rosettes were attached to a cleaned, fresh frozen cadaveric human tibia and the tibia was subjected to 13 loading conditions. Deflection and strain data were used for comparison with the FE model. A geometric model was created on the basis of computed tomography (CT) scans. The CT data was used to map 600 orthotropic material properties to the tibia. All experiments were simulated on the FE model. Measured principal strains were compared to their corresponding FE values using regression analysis. The validated tibia model was reduced in size (75mm to the proximal) and then re-modelled to represent only the proximal tibia. This re-modelled tibia was validated against the reduced size FE model. Virtual surgery was performed on the validated proximal model to implant a UKR.

Summary of Results: For the whole tibia model, the regression line for all axial loads combined had a slope of 0.999, an intercept of −6.24 micro-strain, and an R2 value of 0.962. The root mean square error as a percentage was 5%. For the proximal tibia model, correlation coefficients of 0.989 and 0.976 were obtained for the maximum and minimum principal strains respectively.

Statement of Conclusions: An FE model of an implanted proximal tibia has been validated against experimental data. This model is able to accurately predict the deflection and stresses in a replaced knee joint to obtain clinically relevant information. This will provide a virtual model of unicompartmental arthroplasty, where variables such as fixation method and bearing mechanics can be assessed.

Purpose: To compare the site of lesions in medial and lateral unicompartmental osteoarthritis (OA) of the knee.

Methods: Patients with medial (n=35) and lateral (n=15) OA, having unicompartmental knee arthroplasty, were recruited. Intra-operatively, the distance between the anterior, posterior, medial and lateral margins of the full-thickness lesion and reference lines dividing the condyles was measured. The midpoints of lesions were calculated and groups were compared. Lateral radiographs were used to determine the relationship between the lesion site and knee flexion angle (KFA).

Results: Femoral lesion: In lateral OA, the midpoint of lesions was 25.0mm (SD:8.8) posterior to the reference line passing transversely through the apex of the inter-condylar notch. This was significantly different (p< 0.001) from midpoint in medial OA, which was 10.7mm (SD:9.4) posterior to the reference line.

Tibial lesion: In lateral OA, the midpoint of lesions was 2.0mm (SD:6.5) posterior to the reference line passing through the mid-coronal plane of the resected tibia. This was located significantly more posterior (p=0.038) than midpoint in medial OA, which was 2.2mm (SD:5.7) anterior to the reference line.

Knee Flexion Angle: In lateral OA, the midpoint of lesions was on average at 40° flexion and sites of smaller lesions were very variable. The lesion expanded both anteriorly and posteriorly. In medial OA, smaller femoral lesions occurred in full extension and extended further posteriorly with disease progression.

No significant difference was demonstrated in medial and lateral localisation of the lesions.

Conclusion: Medial OA begins near full extension, progresses in a predictable manner and is perhaps initiated by events occurring at heel strike. Lateral OA begins in flexion in a less predictable manner, at KFA above that seen during the gait cycle. The different sites of lesions in medial and lateral OA suggest different aetiology and pathophysiology. Therefore, prevention and treatment strategies should be different.

Purpose: The objective of this study was to compare the safety and efficacy of 1 × 6 mL intra-articular administration of hylan G-F 20 with placebo.

Methods: In this prospective, multicenter, randomized, double-blind study, patients diagnosed with knee OA were randomized to one 6-mL injection of hylan G-F 20 or saline. The primary efficacy analysis (WOMAC A) was performed on the intent-to-treat population and was based on a repeated-measures model over the 26 weeks of the study.

Results: 253 patients were randomized to hylan G-F 20 (n=124) or placebo (n=129). Mean age was 63 years (42–84), BMI 29.4 (19.5–52.4 kg/m2), 71% were female, and all had primary knee OA of Kellgren Lawrence grade 2 (45%) or 3 (55%). Patients in the hylan G-F 20 group experienced a mean change from baseline in their WOMAC A Likert pain score (0–4 scale) over 26 weeks (primary efficacy criteria) of −0.84, which was statistically significantly different from the change reported in the placebo group (−0.69, p=0.047). Statistically significant differences favoring hylan G-F 20 were also reported for most of the secondary efficacy criteria: WOMAC A1 (estimate Odds Ratio over 26 weeks placebo/hylan G-F 20, 0.64, p=0.013), patient global assessment (0.69, p=0.029), and clinical observer global assessment (0.71, p=0.041); WOMAC B and C changes were not statistically significant between groups. The OMERACT-OARSI responder analysis indicated that 59% of the patients were responders in the hylan G-F 20 group versus 51% in placebo group (0.66, p=0.059). There was no statistically significant difference in the use of rescue medication (acetaminophen) between the 2 groups.

Discussion and Conclusion: This double-blind placebo-controlled study showed one injection of hylan G-F 20 provided symptomatic relief lasting up to 6 months in patients with knee OA; it avoids the need for multiple injections.

Introduction: Treatment options for the young active patient with isolated symptomatic medial compartment OA and pre-existing ACL deficiency are limited. Implant longevity and activity levels may preclude TKA, whilst HTO and unicompartmentasl knee arythroplasty (UKA) are unreliable due to ligamentous instability. UKAs tend to fail because of wear or tibial loosening resulting from eccentric loading. Combined UKA and ACL reconstruction may therefore be a solution.

Method: Fifteen patients with combined ACL reconstruction and Oxford UKA (ACLR group), were matched (age, gender and follow-up period) with 15 patients with Oxford UKA with intact ACL (ACLI group). Prospectively collected clinical and x-ray data from the last follow-up (minimum 3 years, range: 3 – 5) were compared. Ten patients from each group also underwent in-vivo kinematic assessment using a standardised protocol.

Results: At the last follow-up, the clinical outcome for the two groups were similar. One ACLR patient needed revision due to infection. Radiological assessment did not show any significant difference between relative component positions and none of the patients had pathological radiolucencies suggestive of component loosening. Kinematic assessment showed posterior placement of the femur on tibia in extension for the ACLR group, which corrected with further flexion.

Conclusions: The short-term clinical results of combined ACL reconstruction and UKA are excellent. Lack of pathological radiolucencies and near normal knee kinematics suggest that early tibial loosening due to eccentric loading is unlikely.

Aim: The aim of this study was to asses the accuracy of skyline radiographs in the assessment of the patellofemoral joint, when compared to open intraoperative assessment.

Methods: Eighty nine patients undergoing knee replacement surgery were included in the study. Skyline radiographs were obtained preoperatively. These radiographs were assessed and graded by an experienced musculoskeletal radiologist using the Altman and Ahlbäck classifications. The grades were calculated for both the medial and lateral facets of the PFJ. Intraoperative assessment of the Patellofemoral joint was undertaken at the time of surgery. The damage was graded using the modified Collins classification (0: Normal, 1: Superficial damage, 2: Partial thickness cartilage loss, 3: Focal Full thickness cartilage loss < 2cm2, 4: Extensive full thickness cartilage loss < 2cm2). Data was obtained for the Medial Facet, Lateral Facet and Trochlea.

Results: Spearman’s rank correlation coefficient between the radiographic and macroscopic changes within the lateral PFJ were poor with both the Altman 0.22 (p=0.0350) and Ahlbäck 0.24 (p=0.018). The correlation of the medial PFJ was slightly better with a coefficient for Altman 0.42 (P< 0.0001) and Ahlbäck 0.34 (P> 0.001).

Conclusion: In conclusion skyline radiographs provide a poor to moderate preoperative assessment of the degree of osteoarthritis within the patella-femoral joint. This has significant implications for establishing radiographic criteria for planning patella-femoral joint replacement.

Purpose: The aim of this study is to compare the long-term survival results of TKA in patients under the age of 60, using

revision surgery and

Method: From our knee database we identified a cohort of 60 total knee replacements that had been performed over 15 years previously. We identified those who had died, those who had been revised and established the Oxford Knee Score (OKS) for all those still surviving.

Results Using the following endpoint criteria the cumulative 15-year survival was (A) revision surgery alone = 78% (CI 12), (B) revision surgery or an OKS less than or equal to 24 (50% of total OKS) = 63% (CI 13), and (C) revision surgery or moderate pain = 48% (CI 14).

Conclusion The functional survival of TKA in patients under the age of 60 decreases in the second decade following implantation with a significant number of prostheses failing the patient due to knee pain

Purpose: The purpose of this study was to establish patient mortality following salvage treatment (debridement, retention of prosthesis and antibiotic therapy) for infection of primary joint replacement, performed at the unit.

Method: A series of 89 patients underwent salvage treatment for infected primary total joint replacement (47 hips and 42 knees) between 1998 and 2003. The average age of the patients was 70.3 years (range 31.8 to 89.1). A survival analysis was performed using death as the sole endpoint and there were no patients lost to follow-up.

Results: There were a total of 26 deaths with a mean time to death of 3.3 years (range 0.8 to 7.2). The 7-year cumulative patient survival of was 66% (CI 5, number at risk 21).

Conclusions: The morbidity associated with infected total arthroplasty has been well documented. This study highlights that patients undergoing salvage treatment for this condition have significant mortality, with up to a third of patients potentially dying by 7 years.

Introduction: The information in the literature about the relative merits of cemented and cementless unicompartmental knee replacement (UKR) is contradictory, with some favouring cementless fixation while others favouring cemented fixation. Cemented fixations give good survivorship but there is concern about the radiolucency which frequently develops around the tibial component. The exact cause of the occurrence of radiolucency is unknown but according to some, it may suggest suboptimal fixation.

Method: Sixty-two knees (31 in each group) were randomised to receive either cemented or cementless UKR components. The components were similar except that the cementless had a porous titanium and hydroxyappatite (HA) coating. Patients were prospectively assessed by an independent observer pre-operatively and annually thereafter. The clinical assessment included Oxford Knee Score, Knee Society Scores and Tegner activity score. Fluoroscopically aligned radiographs were assessed for thickness and extent of radiolucency under the tibial implant.

Results: At one year there were no differences in the clinical outcome between the groups and there were no loose components. No radiolucencies thicker than 1mm were seen. At one year none of the cementless tibias and 30% of the cemented tibias had complete radiolucencies. One out of 31 cementless (3%) and 12 out of 31 cemented (39%) had partial radiolucencies. This difference between these two groups was high significant (p< 0 0001).

Conclusions: This study clearly demonstrates that the incidence of radiolucency beneath the tibial component is influenced by component design and method of fixation. With identical designs of tibial component none of the cementless components developed complete radiolucences whereas 30% of the cemented components did. We conclude that HA achieves better bone integration than cement.

The aim of this study was to investigate the molecular features of progressive severities of cartilage damage, within the phenotype of Anteromedial Osteoarthritis of the Knee (AMOA).

Ten medial tibial plateau specimens were collected from patients undergoing unicompartmental knee replacements. The cartilage within the area of macroscopic damage was divided into equal thirds: T1(most damaged), to T3 (least damaged). The area of macroscopically undamaged cartilage was taken as a 4th sample, N. The specimens were prepared for histological (Safranin-O and H& E staining) and immunohistochemical analysis (Type I and II Collagen). Immunoassays were undertaken for Collagens I and II and GAG content. Real time PCR compared gene expression between areas T and N.

There was a decrease in OARSI grade across the four areas, with progressively less fibrillation between areas T1, T2 and T3. Area N had an OARSI grade of 0 (normal).

The GAG immunoassay showed decreased levels with increasing severity of cartilage damage (ANOVA P< 0.0001). There was no significant difference in the Collagen II content or gene expression between areas. The Collagen I immunohistochemistry showed increased staining within chondrocyte territorial areas in the undamaged region (N) and immunoassays showed that the Collagen I content of this macroscopically and histologically normal cartilage, was significantly higher than the damaged areas (ANOVA P< 0.0001). Furthermore, real time PCR showed that there was a significant increase in Collagen I expression in the macroscopically normal areas (p=0.04).

In AMOA there are distinct areas, demonstrating progressive cartilage loss. We conclude that in this phenotype the Collagen I increase, in areas of macroscopically and histologically normal cartilage, may represent very early changes of the cartilage matrix within the osteoarthritic disease process. This may be able to be used as an assay of early disease and as a therapeutic target for disease modification or treatment.

Objective: To investigate the effect of lab based simulator training, on the ability of basic surgical trainees to perform diagnostic knee arthroscopy.

Method: 20 orthopaedic SHO’s with minimal arthroscopic experience were randomised to 2 groups. 10 received a fixed protocol of simulator based arthroscopic skills training. This consisted of 3 sessions of 6 simulated arthroscopies using a Sawbones bench-top knee model. Their learning curve was assessed objectively using motion analysis. Time taken, path length and number of movements were recorded. All 20 then spent an operating list with a blinded consultant trainer. They received instruction and demonstration of diagnostic knee arthroscopy before performing the procedure independently. Their performance was assessed using the intra- operative section of the Orthopaedic Competence Assessment Project (OCAP) procedure based assessment (PBA) protocol for diagnostic arthros-copy and further quantified with a global rating assessment scale.

Results: In theatre, simulator-trained SHO’s outscored all but one untrained SHO. The simulator trained group were scored as competent on more than 70% of occasions compared to less than 15% for the un-trained group (p< 0.05). The mean global rating score of the trained group was 24.4 out of 45 compared with 12.4 for the untrained group (p< 0.05). Motion analysis demonstrated objective and significant improvement in performance during simulator training.

Conclusion: The use of lab based arthroscopic skills training leads to subsequent significant improvement in operating theatre performance. This may suggest that formalised lab based training should be a standardised part of future surgical curricula. OCAP PBA’s appear to provide a useful framework for assessment however potential questions are raised about the ability of OCAP to truly distinguish levels of surgical competence.

Aim: The aim of this study was to investigate whether viable chondrocytes can be isolated and subsequently expanded in culture, from cryopreserved intact human articular cartilage.

Method: Human articular cartilage samples, retrieved from patient undergoing total knee replacement, were cored as 5 mm diameter discs then minced to approximately 0.1 mm³ size pieces. Samples were cryopreserved at the following stages; intact cartilage discs, minced cartilage and chondrocytes immediately after enzymatic isolation. After completing of isolation, cell viability was examined using LIVE/DEAD fluorescent staining. Isolated chondrocytes were then cultured and a cell proliferation assay was performed at day 4, 7, 14, 21 and 28 days.

Results: The results showed that the viability of isolated chondrocytes from control, cryopreserved intact AC discs, minced AC and isolated then frozen samples were 71.84 ± 2.63%, 25.61 ± 2.41%, 31.32 ± 2.47 % and 42.53 ± 4.66% respectively. Isolated chondrocytes from all groups were expanded by following degrees after 28 days of culture; Group A: 10 times, Group B: 18 times, Group C: 106 times, and Group D: 154 times.

Conclusion: We conclude that viable chondrocytes can be isolated from cryopreserved intact human AC and then cultured to expand their number. This method could be employed to patients benefit undergoing autologous chondrocyte implantation.

Anteromedial osteoarthritis is a distinct phenotype of osteoarthritis. The arthritic lesion on the tibia is localised to the anteromedial quadrant with an intact ACL. Deficiency of the ACL leads to a progression to tricompartmental disease. Within the spectrum of intact ACL a varying degree of ligament damage is seen. Our aim was to correlate the progression of ACL damage to the geographical extent of disease and the degree of cartilage loss on the tibial plateau.

We systematically digitally mapped 50 tibial plateau resection specimens from clinical photographs of patients undergoing unicompartmental arthroplasty, additionally the damage to their ACL was graded (0: normal, 1:synovium loss, 2:longitudinal splits)

These images were imported into image analysis software. Accurate measurements were made of the dimensions of the specimen. Measurements included the AP distance to the anterior and posterior aspect of the lesion, and the distance to the start of the macroscopically non damaged cartilage. The areas of cartilage damage and full thickness loss were also recorded. The results were represented as a % of total area to account for variation in size of the resection specimens. We compared % of full thickness loss in patients with normal to those with damaged, but functionally intact ligaments.

All specimens had a similar macroscopic appearance. A significant difference was seen with the progression of ACL damage and area of eburnation of bone. Using an unpaired t test, a significant difference in area of % full thickness cartilage loss (P=0.047) was seen between patients with a normal and longitudinal splits within their ACL. No correlation between the clinical status of the ACL and start or finish point of cartilage loss on the tibial plateau

We surmise that the progression from anteromedial to tricompartmental osteoarthritis of the knee may be related to the graduated damage of the ACL.

A sibling risk study that shows a statistically significant increase in risk for anteromedial osteoarthritis of the knee.

Anteromedial osteoarthritis is a distinct phenotype of osteoarthritis. Previous studies have shown a genetic aetiology to both hip and knee osteoarthritis. The aim of this study was to determine the sibling risk of antero-medial osteoarthritis of the knee.

We conducted a retrospective cohort study of 132 probands with primary anteromedial osteoarthritis, who had undergone unicompartmental arthroplasty. Sibling were identified as having symptomatic knee problems by postal Oxford Knee Score (OKS). A positive OKS was defined as an OKS+/− 2SD of the mean of the proband group. Sibling spouses were used as controls. Those siblings & spouses that were symptomatic from the OKS were invited to undergo Knee X-rays, to look for radiological signs of osteoarthritis. Osteoarthritis was diagnosed as greater than Grade II on the Kell-gren Lawrence classification. The pattern of disease was noted and it was considered if the sibling were suitable for a unicompartmental knee arthroplasty. The prevalence and sibling risk of anteromedial osteoarthritis was determined using a randomly selected single sibling per proband family. The prevalence was determined in the 103 single proband sibling pairs.

There was a statistically significant risk within the sibling group P= 0.024 using the Chi square test. The relative risk of anteromedial osteoarthritis was. 3.21(95% CI 1.08 to 9.17)

Genetic factors play a major role in the development of anteromedial osteoarthritis.

Aim: This paper presents the 20-year survival and 10-year clinical follow-up results from the entire series of all medial Oxford meniscal bearing unicompartmental knee arthroplasties performed in a single centre in Sweden, between 1985 and 2004.

Method: Patients were contacted and information about the state of the knee collected. Revision surgery was used in the life-table survival analysis performed. For the entire cohort clinical follow up at 10-years is routinely performed, using the HSS knee score.

Results: The entire group comprised of 683 knees in 572 patients. The mean age at implantation was 69.7 (range 48–94). There had been 30 revision procedures: 8 for lateral arthrosis, 7 for component loosening, 3 for infection, 6 for bearing dislocation, 1 for bearing fracture and 5 for unexplained pain. The 10-year, 15-year and 20-year survival (all cause revision) were 94.1 % (CI 2.9, 237 at risk), 93.5% (CI 4.6, 101 at risk) and 92.3% (CI 15.1, 11 at risk) respectively. From the patients reviewed clinically the mean pre-operative HSS knee score was 57 (95% CI 1), compared to 87 (95% CI 1) at 10-years. Using HSS criteria the results were: 68% excellent, 23% good, 6% moderate and 2% poor.

Conclusion: The results show that this mobile bearing unicompartmental prosthesis offers patients excellent clinical results during the first decade and is durable during the second decade after implantation.

Antero-medial osteoarthritis of the knee displays a well recognised pattern of cartilage damage on the medial tibial plateau. Anteriorly there is a full thickness cartilage defect, with transition to a partial thickness defect, becoming full thickness in the posterior third of the plateau. The retained posterior cartilage is macroscopically normal, but no previous study has assessed its histo-logical features. This study characterises the histological changes, to examine if antero-medial OA of the knee represents a model of progressive osteoarthritic cartilage damage.

Five unicompartmental resection specimens of patients with idiopathic single compartment antero-medial osteoarthritis were assessed. The samples were stained with H& E and Saffinin-O stains and reviewed using the Mankin system, an established method for scoring osteoarthritic changes in cartilage (range 0 [normal] to 14 [grossly osteoarthritic]) Digital images of the histology were reviewed by two observers to exclude inter and intra observer error. Each specimen was assessed at 4 interval points (A,B,C,D) along the A-P axis starting from the most posterior aspect of the exposed bone to the area of macroscopically normal cartilage. Three repeat measurements were taken from the macroscopically normal region (D1,D2,D3). The scores were compared to historical age matched controls of non-osteoarthritic cartilage, where a Mankin grade of < 3 suggests normal cartilage.

From anterior to posterior the H& E staining showed a consistent decrease in structural integrity and cellularity of the cartilage, matched by a qualitative decrease in GAG content (Saffinin-O staining). Mean Mankin scores showed a progressive decrease in score; A = 14.0 (95% CI 0), B = 5.8 (95%CI 2.4), C = 4.4 (95%CI 2.5), D = 1.0 (95%CI 0.9) {p=0.04 ANOVA}. Repeated measurements at the macroscopically normal area showed the Mankin grade was maintained; D1= 1.0 (95%CI 0.9), D2 = 0.6 (95%CI 0.5), D3 = 0.6 (95%CI 0.6).

The results show that the retained posterior cartilage in antero-medial arthritis has a consistently normal Mankin grade. We suggest the defect represents a model of progressive cartilage damage from near normal (posterior) to the grossly osteoarthritic state (anterior).

Introduction This study assesses the outcome of medial unicompartmental knee arthroplasty (UKA) using the Oxford prosthesis for end-stage focal spontaneous osteonecrosis of the knee (SONK, Ahlback grades III & IV).

Methods A total of 29 knees (27 patients) with SONK were assessed using the Oxford Knee Score. Twenty-six had osteonecrosis of the medial femoral condyle; 3 had osteonecrosis of the medial tibial plateau. This group was compared to a similar group who had undergone Oxford Medial UKA for primary osteoarthritis. Patients were matched for age, sex and time since operation.

Results Mean length of follow-up was 5.2 years (range 1–13 years). There were no implant failures in either group, but there was one death 9 months post-arthroplasty from unrelated causes in the group with osteonecrosis. The mean Oxford Knee Score (SD) in the group with osteonecrosis was 37.8 (7.6) and 40.0 (6.6) in the group with osteoarthritis. There was no significant difference between the two groups using Student’s t-test (p=0.29).

Interpretation Use of the Oxford Medial UKA for focal spontaneous osteonecrosis of the knee is reliable in the short to medium term, and gives similar results to when used for patients with primary osteoarthritis.

Introduction and Aims: Single compartmental replacement procedures are increasingly preferred over total knee replacement (TKR) for single compartment osteoarthritis of the knee joint. Theoretically, reduced disruption of the native joint should produce more normal kinematics. This study aimed to describe and compare the sagittal plane kinematics of four different, commonly used devices.

Method: Four groups of patients who had undergone successful single compartment replacement at least two years previously were recruited. Fifteen following Oxford medial UKA, 12 following medial St Georg Sled UKA, five following Oxford lateral UKA, and 12 following Avon PFJ replacement. Patients performed flexion/extension against gravity, and a step-up during video fluoroscopy. The Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, was obtained as a function of knee flexion. This relationship provides indication of sagittal movement between femur and tibia through range and has been validated as a reliable measure of joint kinematics.

Results: The kinematic profile for each group was compared to that of the profile for 12 normal and 30 TKR (AGC) knees. All three tibiofemoral devices produced knee kinematics similar to the normal knee. The PTA was found to have a linear relationship to flexion angle, decreasing with increasing knee flexion angle. No such linear relationship exists for the TKR joint, which display abnormal kinematics. The PF device also reflected similar trends to that for normal knees except that the PTA was moderately increased throughout the entire range of flexion (three degrees).

Conclusion: In contrast to TKR, all single compartmental knee replacements provided kinematics similar to the normal joint. The kinematic pattern of the PFJ replacement may be of most interest as the observed increase in PTA through range could influence patello-femoral contact forces

Introduction and Aims A randomised controlled trial (RCT) and a multi-centre unilateral cohort study were performed as part of the stepwise introduction of a new mobile bearing knee. The aim was to ensure that outcome for the new device was at least as good as that for an established fixed bearing device. This paper presents three year follow up of the published one year results. Instability and prevalence of “clicking” from the joint were examined in detail.

Method 1. A multi-centre RCT of patients undergoing bilateral knee replacement compared functional outcome between two different prostheses, the new mobile bearing device (TMK) and an established fixed bearing device (AGC). 2. A separate multi-centre cohort of 166 patients who had undergone a unilateral mobile bearing procedure at least six months previously was used to assess complication rate and corroborate any findings from the bilateral trial. Outcome measures included Oxford Knee Scores, American Knee Society ratings and complication rate.

Results The bilateral trial revealed no significant differences in outcome between the two devices. Revision rate for all (199) mobile bearing knees was less than 2%. The mean Oxford Knee Score for outcome for all mobile bearing knees was 37.1 ± 10.1. About 7% of patients reported instability. Clicking was more common in the TMK (48%) than in the AGC (30%) and was reported as a problem in 16% of TMK’s in the cohort study. However, clicking was unrelated to outcome score in both studies.

Conclusion At three years, the mobile bearing device was as good as the fixed bearing device. There was a relatively high prevalence of “clicking” in the TMK but the cause remains unclear. Furthermore, the symptom was not associated with poor functional outcome. The bilateral RCT and cohort study allows assessment of function and potential problems. It provides rigourous scientific justification for the introduction and early assessment of new implants.

Polyethylene wear remains an important cause of failure in knee replacements. Retrieval studies, simulators and simple X-ray methods produce wear data that may be inaccurate or unrealistic. We have developed an accurate RSA system for measuring wear in-vivo. Using this system we have found wear rate in a fixed bearing TKR to be about 0.1mm/yr[1]. In this abstract we extend the study to fully congruent mobile bearings.

Four Oxford uni-compartmental knee replacements, with excellent clinical results were studied ten years after implantation. RSA X-rays were taken in double leg stance with the knee in full extension and 15 and 30 degrees flexion. Following RSA calibration, silhouettes of the components on the stereo X-rays were extracted using a Canny edge detector and were matched to silhouettes projected using CAD models to determine the 3D component position. The average minimum thickness of the bearing was determined and was compared with the measured minimum thickness of 14 unused bearings to calculate linear penetration.

The average linear penetration after average 10 years implantation (range 8.5 to 10.25 years) was 0.16 mm (SD 0.13 mm). The average penetration rate was 0.017 mm/year (SD 0.011 mm/year). The maximum linear penetration rate was 0.027 mm/year.

The penetration rate is similar to that obtained in a retrieval study [2]. Compression of the bearing is minimal due to 6sqcm of contact area. This study therefore demonstrates that polyethylene wear on the upper and lower surfaces is minimal in fully congruous mobile bearing knee replacements.

Introduction: Radiolucencies are frequently observed around joint replacements. Their signiþcance & etiology remain unclear. Aim: 1. To study radiolucency under tibial tray of Oxford UKA and correlate it to the clinical outcome. 2. To study implant migration using RSA and study the correlation between migration and radiolucency. Materials and Methods: Fifty consecutive patients cemented Oxford UKA with a minimum follow up of two years were studied. At 2 years precisely aligned radiographs were obtained and evaluated for presence and extent of radiolucency under the tibial tray. The patients were divided into two groups Ð those with (Group I) and those without presence of radiolucency under the tibial tray (Group II). All the patients were assessed using KSS. Patients had RSA marker balls inserted around the prosthesis at the time of index procedure. Using RSA, the degree and direction of implant movement was measured at 1 & 2 yrs post surgery. Results: A) There were 26 patients in group I and 24 in group II. Both the groups were well matched for age and sex distribution. There was no signiþcant difference between the two groups when various clinical scores were compared. Maximum width of radiolucency was 1.1 mm and the average width was 0.57 mm. B) RSA study: By 12 months, the tibial component had migrated signiþcantly distally (mean: 0.42 mm, S.D.: 0.15 mm) and anteriorly (mean: 0.47 mm, S.D. 0.27mm). No signiþcant migration occurred after 12 mths. There was no correlation between presence or extent of radiolucency and migration of the tibial component. Conclusion: There is no relationship at 2 years between radiolucency and clinical results. There is also no relationship between radiolucency and migration. Therefore radiolucencies of 1mm or less can be ignored