The ability to learn arthroscopic surgery is an important aspect of modern day orthopaedic surgery. Knowing that variation in innate ability exists amongst medical students, the aim of this study was to investigate the effect of training on the arthroscopic surgical performance of our future orthopaedic surgeons (medical students). Two arthroscopic tasks (one shoulder and one knee) were set up in a bioskills laboratory to represent core skills required for arthroscopic training. Thirty three medical students with no previous arthroscopic surgery experience were randomised to a ‘Trained’ (n=16) and ‘Non-trained’ (n=17) cohort. Both groups watched an instructional video. The Trained cohort also received specific training on the tasks prior to their first episode. Thirty episodes of each task were then undertaken. The primary outcome variable was success or failure. Individuals were assessed as ‘competent’ if they stabilised their learning curve within 20 episodes. The secondary outcome measure was an objective assessment of technical dexterity using a validated Motion Analysis system (time taken to complete tasks, total path length of the subject's hands, and number of hand movements).Background
Methods
In pre-operative planning for total hip arthroplasty (THA), femoral offset (FO) is frequently underestimated on AP pelvis radiographs as a result of inaccurate patient positioning, imprecise magnification, and radiographic beam divergence. The aim of the present study was to evaluate the reliability and accuracy of predicting three-dimensional (3-D) FO as measured on computed tomography (CT) from measurements performed on standardised AP pelvis radiographs. In a retrospective cohort study, pre-operative AP pelvis radiographs and corresponding CT scans of a consecutive series of 345 patients (345 hips, 146 males, 199 females, mean age 60 (range: 40-79) years, mean body-mass-index 27 (range: 29-57) kg/m2) with primary end-stage hip osteoarthritis were reviewed. Patients were positioned according to a standardised protocol and all images were calibrated. Using validated custom programmes, FO was measured on corresponding AP pelvis radiographs and CT scans. Inter- and intra-observer reliability of the measurement methods were evaluated using intra-class correlation coefficients (ICC). To predict 3-D FO from AP pelvis measurements, the entire cohort was randomly split in two groups and gender specific linear regression equations were derived from a subgroup of 250 patients (group A). The accuracy of the derived prediction equations was subsequently assessed in a second subgroup of 100 patients (group B). In the entire cohort, mean FO was 39.2mm (95%CI: 38.5-40.0mm) on AP pelvis radiographs and 44.6mm (95%CI: 44.0-45.2mm) on CT scans. FO was underestimated by 14% on AP pelvis radiographs compared to CT (5.4mm, 95%CI: 4.8-6.0mm, p<0.001) and both parameters demonstrated a linear correlation (r=0.642, p<0.001). In group B, we observed no significant difference between gender specific predicted FO (males: 48.0mm, 95%CI: 47.1-48.8mm; females: 42.0mm, 95%CI: 41.1-42.8mm) and FO as measured on CT (males: 47.7mm, 95%CI: 46.1-49.4mm, p=0.689; females: 41.6mm, 95%CI: 40.3-43.0mm, p=0.607). The results of the present study suggest that femoral offset can be accurately and reliably predicted from AP pelvis radiographs in patients with primary end-stage hip osteoarthritis. Our findings support the surgeon in pre-operative templating and may improve offset and limb length restoration in THA without the routine performance of CT.
In uncemented total hip arthroplasty (THA), the optimal femoral component should allow both maximum cortical contact with proximal load transfer and accurate restoration of individual joint biomechanics. This is often compromised due to a high variability in proximal femoral anatomy. The aim of this on-going study is to assess the variation in proximal femoral canal shape and its association with geometric and anthropometric parameters in primary hip OA. In a retrospective cohort study, AP-pelvis radiographs of 98 consecutive patients (42 males, 56 females, mean age 61 (range:45-74) years, BMI 27.4 (range:20.3-44.6) kg/m2) who underwent THA for primary hip OA were reviewed. All radiographs were calibrated and femoral offset (FO) and neck-shaft-angle (NSA) were measured using a validated custom programme. Point-based active shape modelling (ASM) was performed to assess the shape of the inner cortex of the proximal femoral meta- and diaphysis. Independent shape modes were identified using principal component analysis (PCA). Hierarchical cluster analysis of the shape modes was performed to identify natural groupings of patients. Differences in geometric measures of the proximal femur (FO, NSA) and demographic parameters (age, height, weight, BMI) between the clusters were evaluated using Kruskal-Wallis one-way-ANOVA or Chi-square tests, as appropriate. In the entire cohort, mean FO was 39.0 mm, mean NSA was 131 degrees. PCA identified 10 independent shape modes accounting for over 90% of variation in proximal femoral canal shape within the dataset. Cluster Analysis revealed 6 shape clusters for which all 10 shape modes demonstrated a significantly different distribution (p-range:0.000-0.015). We observed significant differences in age (p=0.032), FO (p<0.001) and NSA (p<0.001) between the clusters. No significant differences with regard to gender or BMI were seen. Our preliminary analysis has identified 6 different patterns of proximal femoral canal shape which are associated with significant differences in femoral offset, neck-shaft-angle and age at time of surgery. We are currently evaluating the entire dataset of 345 patients which will allow a comprehensive classification of variation in proximal femoral shape and joint geometry. The present data may optimise preoperative planning and improve future implant design in THA.
Traditional TKR designs exhibit abnormal and unpredictable kinematics: with posterior subluxation in extension and anterior slide with flexion. These can contribute to restricted knee flexion and reduced quadriceps efficiency. Newer designs attempt to provide “guided motion” with the aim of mimicking normal knee kinematics. The Journey (Smith & Nephew) BCS TKR incorporates both an anterior and a posterior cam/post mechanism while Triathlon PS TKR (Stryker) incorporates a posterior cam/post mechanism. This study compares the in-vivo kinematics of these two designs and compares it with normal knee. Knee kinematics of 10 patients with Journey-BCS TKR and 11 patients with Triathlon PS TKR; all with excellent clinical outcome (average age: 65) were analysed. Patients underwent fluoroscopic assessment of the knee during a step-up and deep knee bend exercise. 2D fluoroscopic images were recorded. Data was analysed for patella tendon angle (PTA) and contact points using a 3D model fitting technique. This data was compared to normal knee kinematics (n=20).Introduction
Methods
A femoral head/neck ratio (HNR) of less than 1.27 is associated with an increased risk of arthritis. The aim of this study was to establish whether there is evolutionary evidence that the homonin, bipedal stance has led to alterations in HNR that predispose humans to osteoarthritis (OA). Specimens provided by The Natural History Museums of London, Oxford and the Department of Zoology, University of Oxford were grouped according to gait pattern, HAKF (Hip and knee flexed), Arboreal (ability to stand with hip and knee joints extended) and homonin/bi-pedal. Specimens included those from Devonion, Triassic, Jurrasic, Cretaceous, Miocene, Paleolithic, Pleistocene periods to modern day. Three-dimensional skeletal geometries were segmented using CT images and HNR measurements were taken from coronal views. These were compared with the HNR of 119 asymptomatic human volunteers and 210 patients that had a hip joint replacement for primary OA. Species of the HAKF group had the smallest HNR (1.10, SD:0.09). Species of the Arboreal group had significantly higher HNR (1.63, SD:0.15) in comparison to the Bipedal group (1.41, SD:0.04) (p=0.006), Human (1.33, SD:0.08) and the OA group (1.3, SD:0.09). The range of movement associated with arboreal habitat caused an associated change in HNR. This study would suggest that the HNR peaked in the Miocene period with species that ambulated on both ground and trees. More recent homonin gait appears to have developed a smaller HNR and humans have the smallest amongst their close ancestors. Evolutionary theory would suggest that modern environmental pressures might pre-dispose future hominin evolution to OA, secondary to a further reduction in HNR.
Stem geometry is known to influence the outcome in THA; however it is unknown whether the material properties, stiffness in particular can influence the stem stability and outcome. The aim of this study was to measure the influence of stem material properties on micromotion and migration using Roentgen Stereophotogrammetric Analysis (RSA) system. 41 patients were implanted with a collarless polished tapered (CPT) femoral stem (Zimmer, Warsaw, Indiana), which was made of either cobalt-chromium (CoCr) (n=21) or stainless steel (n=20). RSA was used to measure dynamically inducible micromotion (DIMM: difference in stem position in going from double-leg stance (DLS) to single leg stance (SLS)), prosthesis bending (difference in the head-tip distance when going from DLS to SLS), and mean migration of the head, tip and the cement restrictor. DIMM and bending were measured at 3 months, migration at 6, 12 and 24 months. All analyses were carried out using SPSS for windows (v.15.0.0, Chicago. IL, USA). Results were reported as mean ± 95% confidence interval (CI) and regarded as significant when p < 0.05. Preliminary analysis showed that total head DIMM was significantly (p = 0.02) greater for CoCr (0.97mm ± 0.6mm) than stainless steel (0.27mm ± 0.6mm). The mean stem bending for CoCr was 0.08mm (± 0.06mm) and for stainless steel 0.15mm (± 0.06mm) (p =0.77). Both implants heads migrated posteriorly, medially and distally. The mean subsidence for the cobalt-chromium and stainless steel stems was 1.02mm (± 0.19mm) (p < 0.001) and 1.12mm (± 0.34mm) (p=0.001) (p= 0.07) at 24 months. It was interesting to note that the dynamically induced micromotion was greater for the stiffer stem, however there were no differences in terms of overall migration, indicating that survival (in terms of loosening) should be the similar for both steel and CoCr versions of this implant.
Primary mechanical stability is important with uncemented THR because early migration is reduced, leading to more rapid osseointegration between the implant and bone. Such primary mechanical stability is provided by the design features of the device. The aim of this study was to compare the migration patterns of two uncemented hip stems, the Furlong Active and the Furlong HAC stem; the study was designed as a randomised control trial. The implants were the Furlong HAC, which is an established implant with good long term results, and the Furlong Active, which is a modified version of the Furlong HAC designed to minimise stress concentrations between the implant and bone, and thus to improve fixation. The migration of 43 uncemented femoral components for total hip replacement was measured in a randomised control trial using Roentgen Stereophotogrammetric Analysis (RSA) over two years. Twenty-three Furlong HAC and twenty Furlong Active stems were implanted into 43 patients. RSA examinations were carried out post-operatively, and at six months, 12 months and 24 months post-operatively. The patients stood in-front of a purpose made calibration frame which contained accurately positioned radio-opaque markers. From the obtained images, the 3-D positions of the prosthesis and the host bone were reconstructed. Geometrical algorithms were used to identify the components of the implant. These algorithms allowed the femoral component to be studied without the need to attach markers to the prosthesis. The migration was calculated relative to the femoral coordinate system representing the anterior-posterior (A-P), medial-lateral (M-L) and proximal-distal (P-D) directions respectively. Distal migration was termed subsidence.Introduction
Materials and methods
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. 46 subjects with symptomatic partial thickness AMG underwent MRI assessment with dedicated 3 Tesla sequences. All joint compartments were scored for both partial and full thickness cartilage lesions, osteophytes and bone marrow lesions (BML). Both menisci were assessed for extrusion and tear. Anterior cruciate ligament (ACL) integrity was also assessed. Osteophytes were graded on a four point scale in the intercondylar notch and the lateral margins of the joint compartments. Scoring was performed by a consultant radiologist and clinical research fellow using a validated MRI atlas with consensus reached for disagreements. The results were tabulated and relationships of the interval data assessed with linear by linear Chi2 test and Pearson's Correlation.Introduction
Method
The results of the original mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing because of high dislocation rates (11%). This original implant used a flat bearing articulation on the tibial tray. To address the issue of dislocation a new implant (domed tibia with biconcave bearing to increase entrapment) was introduced with a modified surgical technique. The aim of this study was to compare the risk of dislocation between a domed and flat lateral UKR. Separate geometric computer models of an Oxford mobile bearing lateral UKR were generated for the two types of articulation between the tibial component and the meniscal bearing: Flat-on-flat (flat) and Concave-on-convex (domed). Each type of mobile bearing was used to investigate three distinct dislocation modes observed clinically: lateral to medial dislocation, with the bearing resting on the tray wall (L-M-Wall); medial to lateral dislocation, out of the joint space (M-L); anterior to posterior dislocation, out of the joint space (A-P). A size C tray and a medium femoral component and bearing were used in all models. The femoral component, tibial tray and bearing were first aligned in a neutral position. For each dislocation the tibial tray was restrained in all degrees of freedom. The femoral component was restrained from moving in the anterior-posterior directions and in the medial-lateral directions. The femoral component was also restrained from rotating about the anterior-posterior, medial-lateral and superior-inferior directions. This meant that the femoral component was only able to move in the superior-inferior direction. Different bearing sizes were inserted into the model and the effect that moving the femoral component medially and laterally had on the amount of distraction required to cause bearing dislocation was investigated.Introduction
Methods
Osteoarthritis (OA) is a degenerative, chronic disease of the articular cartilage that affects more than 150 million people [1]. In the knee, OA can begin as either isolated medial OA or isolated lateral OA. Previous research [2,3] shows medial OA and lateral OA have characteristic cartilage lesion locations and progression patterns as well as flexion angles associated with lesion development, indicating strong involvement of mechanical factors in disease initiation. Therefore, it is important to investigate these mechanical factors. Previous studies combined data sets (geometry, motion, load) from separate sources. The aim of the current work was to use a consistent multi-modal approach. A finite element (FE) model of a healthy knee in full extension was created using magnetic resonance imaging (MRI) and motion analysis data from the same subject (female, 24 yrs). MRI data was obtained using a 3T MRI scanner (Philips Medical Systems/Achieva). Surface geometries of the tibia, femur, and associated cartilage were then semi-automatically segmented and processed (Mimics 12.5; Geomagic Studio 11; SolidWorks 2009). Motion data was collected at 100 Hz (Vicon 612) during level walking and subsequently applied to a lower limb model (AnyBody Version 3.0) to calculate muscle forces. Both sets of data were then combined to create a subject-specific FE model (ANSYS 11.0) which was solved to determine relative contact areas, pressures, and deformations in the medial and lateral tibiofemoral compartments.Background
Method
Unicompartmental Knee Replacement (UKR) is an appealing alternative to Total Knee Replacement (TKR) when the patient has isolated compartment osteoarthritis (OA). A common observation post-operatively is radiolucency between the tibial tray wall and the bone. In addition, some patients complain of persistent pain following implantation with a UKR; this may be related to elevated bone strains in the tibia. The aim of this study was to investigate the mechanical environment of the tibia bone adjacent to the tray wall, following UKR, to determine whether this region of bone resorbs, and how altering the mechanical environment affects tibia strains. A finite element (FE) model of a cadaver tibia implanted with an Oxford UKR was used in this study, based on a validated model. A single static load, measured in-vivo during a step-up activity was used. There was a 1 mm layer of cement surrounding the keel in the cemented UKR, and the cement filled the cement pocket. In accordance with the operating procedure, no cement was used between the tray wall and bone. For the cementless UKR a layer of titanium filled the cement pocket. An intact tibia was used to compare to the cemented and cementless UKR implanted tibiae. The tibia was sectioned by the tray wall, defining the radiolucency zone (parallel to the vertical tray wall, 2 mm wide with a volume of 782.5 mm3), corresponding to the region on screened x-rays where radiolucencies are observed. Contact mechanics algorithms were used between all contacting surfaces; bonded contact was also introduced between the tray wall and adjacent bone, simulating a mechanical tie between them. Strain energy density (SED), was compared between the intact and implanted tibia for the radiolucency zone. Equivalent strains were compared on the proximal tibia between the intact and implanted tibia models. Forty patients (20 cemented, 20 cementless) who had undergone UKR were randomly selected from a database, and assessed for radiolucency.Introduction
Materials and methods
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). 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 coefficient of variation 10.7%). The mean of the two extension angle values was used. The results were tabulated and analysed (R v2.9.1).Introduction
Methods
Iterative finite element (FE) models are used to simulate bone remodelling that takes place due to the surgical insertion of an implant or to simulate fracture healing. In such simulations element material properties are calculated after each iteration of solving the model. New material properties are calculated based on the results derived by the model during the last iteration. Once the FE model has gone through a number of such iterations it is often necessary to assess the remodelling that has taken place. The method widely used to do this is to analyse element Young's modulus plots taken at particular sections through the model. Although this method gives relevant information which is often helpful when comparing different implants, the information is rather abstract and is difficult to compare with patient data which is commonly in the form of radiographs. The authors suggest a simple technique that can be used to generate synthetic radiograph images from FE models. These images allow relatively easy comparisons of FE derived information with patient radiographs. Another clear advantage of this technique is that clinicians (who are familiar with reading radiographs) are able to understand and interpret them readily. To demonstrate the technique a three dimensional (3D) model of the proximal tibia implanted with an Oxford Unicompartmental Knee replacement was created based on CT data obtained from a cadaveric tibia. The model's initial element material properties were calculated from the same CT data set using a relationship between radiographic density and Young's modulus. The model was subject to simplified loading conditions and solved over 365 iterations representing one year of in vivo remodelling. After each iteration the element material properties were recalculated based on previously published remodelling rules. Next, synthetic anteroposterior radiographs were generated by back calculating radiographic densities from material properties of the model after 365 iterations. A 3D rectangular grid of sampling points which encapsulated the model was defined. For each of the elements in the FE model radiographic densities were back calculated based on the same relationships used to calculate material properties from radiographic densities. The radiographic density of each element was assigned to all the sampling grid points within the element. The 3D array of radiographic densities was summed in the anteroposterior direction thereby creating a 2D array of radiographic densities. This 2D array was plotted giving an image analogous to anteroposterior patient radiographs. Similar to a patient radiograph denser material appeared lighter while less dense material appeared darker. The resulting synthetic radiographs were compared to patient radiographs and found to have similar patterns of dark and light regions. The synthetic radiographs were relatively easy to produce based on the FE model results, represented FE results in a manner easily comparable to patient radiographs, and represented FE results in a clinician friendly manner.
The heat produced by drills, saws and PMMA cement in the handling of bone can cause thermal necrosis. Thermal necrosis could be a factor in the formation of a fibrous tissue membrane and impaired bony ingrowth into porous prostheses. This has been proposed to lead to non-union of osteotomies and fractures, the failure of the bone-cement interface and the failure of resurfacing arthroplasty. We compared three proprietary blades (the De Soutter, the Stryker Dual Cut and the Stryker Precision) in an in-vitro setting with porcine tibiae, using thermocouples embedded in the bone below the cutting surface to measure the increases in bone temperature. There was a significant (p=0.001) difference in the change in temperature (δT) between the blade types. The mean increase in temperature was highest for the De Soutter, 2.84°C (SD: 1.83°C, range 0.48°C to 9.30°C); mean δT was 1.81°C (SD: 1.00°C, range 0.18°C to 4.85°C) for the Precision and 1.68°C (SD: 0.95°C, range 0.24°C to 5.67°C). Performing paired tests, there was no significant difference in δT between the Precision and Dual Cut blades (p=0.340), but both these blades had significantly (p=0.003 for Precision vs De Soutter, p<0.001 for Dual Cut vs De Soutter) lower values for δT than the Dual Cut.
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. 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].Introduction
Aim
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. This prospective study examines a consecutive series of 595 knees (mean age 66 years, range: 33-88) undergoing Oxford UKA with a minimum 5-year follow-up. Patients were divided into three groups; Group I (Normal body weight), BMI <25 (n=171), Group II (overweight), BMI 25- 30 (n=264), and Group III (Obese), BMI ≥30 (n=160). The survivorship and functional outcome (as assessed by change in Oxford Knee Score [DeltaOKS]) and Knee Society Score (KSS) for all three groups were compared.Introduction
Methods
To investigate the linear penetration rate of the polyethylene bearing in unicompartmental knee arthroplasty at twenty years. The Phase 1 Oxford medial UKR was introduced in 1978 as a design against wear, with a fully congruous articulation. In 1987 the Phase 2 implant was introduced with new instrumentation and changes to the bearing shape. We have previously shown a linear penetration rate (LPR) of 0.02 mm/year at ten years in Phase 2, but that higher penetration rates can be seen with impingement. The aim of this study was to determine the 20 year in-vivo LPR of the Oxford UKR, using Roentgen Stereophotogrammetric Analysis (RSA).Purpose of study
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. Using the standardised indications, more than 1100 Oxford UKRs have been performed to date over the last 10 years. These patients are assessed pre-operatively and at regular intervals post-operatively in a dedicated research clinic. We present the results of these consecutive cases. Patients were classified into two groups: group I (satisfy Kozinn-Scott recommendations) and group II (outside recommendations).Introduction
Methods
In 12 patients, we measured the oxygen concentration in the femoral head-neck junction during hip resurfacing through the anterolateral approach. This was compared with previous measurements made for the posterior approach. For the anterolateral approach, the oxygen concentration was found to be highly dependent upon the position of the leg, which was adjusted during surgery to provide exposure to the acetabulum and femoral head. Gross external rotation of the hip gave a significant decrease in oxygenation of the femoral head. Straightening the limb led to recovery in oxygen concentration, indicating that the blood supply was maintained. The oxygen concentration at the end of the procedure was not significantly different from that at the start. The anterolateral approach appears to produce less disruption to the blood flow in the femoral head-neck junction than the posterior approach for patients undergoing hip resurfacing. This may be reflected subsequently in a lower incidence of fracture of the femoral neck and avascular necrosis.
To assess the incidence of radiolucency in cemented and cementless Oxford unicompartmental knee replacement at two years. Most unicompartmental knee replacements (UKRs) employ cement for fixation of the prosthetic components. The information in the literature about the relative merits of cemented and cementless UKR is contradictory, with some favouring cementless fixation and others favouring cemented fixation. In addition, there is concern about the radiolucency that frequently develops beneath the tibial component with cemented fixation. The exact cause of the occurrence of radiolucency is unknown but it has been hypothesised that it may suggest suboptimal fixation.Purpose of Study
Introduction
