Tibial periprosthetic fracture is an important complication of the Oxford Unicompartmental Knee Replacement (OUKR). Primary fixation of cementless OUKR tibial components relies on the interference-fit of the ‘keel’ and a slot in the proximal tibia. Clinically used double blade keel saws (DKS) create slots with two grooves, generating stress concentrations where fractures may initiate. This study aimed to investigate slot factors that may influence incidence of tibial periprosthetic fractures. Slots were made in PCF20 polyurethane foam using the DKS plus/minus adjuvant rasping, single blade keel saw (SKS), and rasp-only. Round and square slots were machined with milling cutters. Compact tensile tests were conducted per ASTM E399 to determine tensile load to fracture (TLTF) and results were validated using bovine tibia. Cementless OUKR components were implanted into slots in custom polyurethane blocks and compressed to failure to determine anatomical load to fracture (ALTF). A custom MATLAB program calculated slot roundness from cross-sectional images. Round slots had higher TLTF (29.5N, SD=2.7) than square (25.2N, SD=1.7, p<0.05) and DKS slots (23.3N, SD=2.7, p<0.0001). Fractures occurred at the round slot apices, square slot corners, and deepest DKS slot grooves. ALTF was not significantly different between square and round slots. Adjuvant rasping made DKS slots significantly rounder, resulting in significantly higher TLTF, but rasping did not increase ALTF. ALTF was significantly higher for SKS (850N, SD=133, p<0.01) and rasp-only (912N, SD=100, p<0.001) slots compared to standard DKS slots (703N, SD=81). Round keel slots minimise stress concentrations and increase TLTF but do not increase ALTF. The SKS and rasp-only slots retain material at slot ends and have significantly higher ALTF. Future studies should assess saw blades that retain material and round slot ends to evaluate if their use may significantly reduce the incidence of tibial periprosthetic fracture.
The Oxford Unicompartmental Knee Replacement's (OUKR's) fully-congruent design minimises polyethylene wear. Consequently, wear is a rare failure mechanism. Phase-3 OUKR linear wear at 5 years was higher than previous OUKR phases, but very low compared to fixed-bearing UKRs. This study aimed to measure OUKR bearing wear at 10 years and investigate factors that may affect wear. Bearing thickness for 39 OUKRs from a randomised study was calculated using radiostereometric analysis at regular intervals up to 10 years. Data for 39 and 29 OUKRs was available at 5 and 10 years, respectively. As creep occurs early, wear rate was calculated using linear regression between 6 months and 10 years. Relationships between wear and patient factors, fixation method, Oxford Knee Score (OKS), bearing position, and component position were analysed.Abstract
Introduction
Methodology
Cementless fixation of Oxford Unicompartmental Knee Replacements (UKRs) is an alternative to cemented fixation, however, it is unknown whether cementless fixation is as good long-term. This study aimed to compare primary and long-term fixation of cemented and cementless Oxford UKRs using radiostereometric analysis (RSA). Twenty-nine patients were randomised to receive cemented or cementless Oxford UKRs and followed for ten years. Differences in primary fixation and long-term fixation of the tibial components (inferred from 0/3/6-month and 6-month/1-year/2-year/5-year/10-year migration, respectively) were analysed using RSA and radiolucencies were assessed on radiographs. Migration rates were determined by linear regression and clinical outcomes measured using the Oxford Knee Score (OKS).Abstract
Introduction
Methodology
The aim of this study was to determine the polyethylene wear rate of Phase 3 Oxford Unicompartmental Knee Replacement bearings and to investigate the effects of resin type and manufacturing process. A total of 63 patients with at least ten years’ follow-up with three bearing types (1900 resin machined, 1050 resin machined, and 1050 resin moulded) were recruited. Patients underwent full weight-bearing model-based radiostereometric analysis to determine the bearing thickness. The linear wear rate was estimated from the change in thickness divided by the duration of implantation.Objectives
Methods
The primary stability of the cementless Oxford Unicompartmental Knee Replacement (OUKR) relies on interference fit (or press fit). Insufficient interference may cause implant loosening, whilst excessive interference could cause bone damage and fracture. The aim of this study was to identify the optimal interference fit by measuring the force required to seat the tibial component of the cementless OUKR (push-in force) and the force required to remove the component (pull-out force). Six cementless OUKR tibial components were implanted in 12 new slots prepared on blocks of solid polyurethane foam (20 pounds per cubic foot (PCF), Sawbones, Malmo, Sweden) with a range of interference of 0.1 mm to 1.9 mm using a Dartec materials testing machine HC10 (Zwick Ltd, Herefordshire, United Kingdom) . The experiment was repeated with cellular polyurethane foam (15 PCF), which is a more porous analogue for trabecular bone.Objectives
Materials and Methods
High tibial osteotomy is an efficient treatment for medial compartment osteoarthritis of the knee; its used for middle aged patients with high activity levels and can delay the need for total arthroplasty. The results of total knee arthroplasty after failed high tibial osteotomy are controversies; several authors reported inferior outcomes, but others have concluded that tibial osteotomy doesn't bias following total arthroplasty. The aim of this study was to evaluate the results of failed high tibial osteotomy subsequently converted to total knee arthroplasty and compare the results to group of patients underwere primary arthroplasty; the authors evaluate some of technical problems that a previous high tibial osteotomy can generate, like scar tissue, patellar tendon shortening and changes of proximal tibial anatomy. 50 total knee arthroplasty performed after a previous closed wedge osteotomy were matched with 50 patients operated with a primary knee prosthesis for osteoarthritis. The time from a proximal tibial osteotomy to a prosthesis operation was in mean eight years. the Knee Society clinical and radiographic score system and W.O.M.A.C. evaluation were used to evaluate knees before surgery and at each follow up (average 5 years). At an average of five years follow up, the clinical results of total knee arthroplasty after high tibial osteotomy were similar to those of primary knee prosthesis.Methods
Results
High tibial osteotomy is an efficient treatment for medial compartment osteoarthritis of the knee; its used for middle aged patients with high activity levels and can delay the need for total arthroplasty. The results of total knee arthroplasty after failed high tibial osteotomy are controversies; several authors reported inferior outcomes, but others have concluded that tibial osteotomy doesn’t bias following total arthroplasty. The aim of this study was to evaluate the results of failed high tibial osteotomy subsequently converted to total knee arthroplasty and compare the results to group of patients underwere primary arthroplasty; the authors evaluate some of technical problems that a previous high tibial osteotomy can generate, like scar tissue, patellar tendon shortening and changes of proximal tibial anatomy.
At an average of five years follow up, the clinical results of total knee arthroplasty after high tibial osteotomy were similar to those of primary knee prosthesis.
High tibial osteotomy is an efficient treatment for medial compartment osteoarthritis of the knee; its used for middle aged patients with high activity levels and can delay the need for total arthroplasty. The results of total knee arthroplasty after failed high tibial osteotomy are controversies; several authors reported inferior outcomes, but others have concluded that tibial osteotomy doesn’t bias following total arthroplasty. The aim of this study was to evaluate the results of failed high tibial osteotomy subsequently converted to total knee arthroplasty and compare the results to group of patients underwere primary arthroplasty; the authors evaluate some of technical problems that a previous high tibial osteotomy can generate, like scar tissue, patellar tendon shortening and changes of proximal tibial anatomy.
At an average of five years follow up, the clinical results of total knee arthroplasty after high tibial osteotomy were similar to those of primary knee prosthesis.
Obesity is strongly linked to osteoarthritis; can affect the outcome of total knee arthroplasty and can increase the load on the components with reduction of the implant’s survivorship. The purpose of this study is to compare clinical and radiographic outcomes in obese (defined as BMI >
30) and non obese patients. The Knee Society scoring system and WOMAC was used to evaluate the knees preoperately and at latest follow up. With a follow up ranging from 1 to 5 years, Knee Society score and WOMAC for the patients who were obese were lower than non obese patients. Non progressive radiolucent lines were located adjacent to the tibial component in the group of obese patients, but without clinical significance.
Subjective data included SF-36, DASH, Simple shoulder test; active and passive ROM, muscles strength etc. represented objective data. A rigorous statistical analysis was performed.
The authors believe that better knowledge of correlation between outcome and technical aspects in shoulder replacement could be important to define surgical practice criteria.
Shoulder replacement has increased exponentially over the past decades due to good results reported in literature and improvement of surgical technique and devices efficacy. Previous studies suggested the effectiveness of shoulder replacement in fractures, assessing objective parameters as range of motion and radiographic images and evaluating the of postoperative complications and subsequent revision; pain relief, physical function level and health related quality of life (QoL) improvement were often left out. A prospective study was conducted on 21 patients surgically treated with shoulder emiarthroplasty for proximal humeral fractures (18 women and 3 men, mean age at follow-up 70 years – range: 57–82). The purpose of the present study is to collect the patient-relevant outcomes in a homogeneous sample (for surgeon, surgery, implant, inclusion-exclusion criteria, neurological status) of patients who underwent shoulder replacement for proximal humeral fractures. Preoperatively patients were evaluated through x-rays (trauma series), Ct-scans were performed when necessary for surgical decision. Postoperatively, two independent examiners examined all patients clinically and radiographically. For patient-oriented standardized measure SF-36, DASH (Disability of Arm, Shoulder and Hand questionnaire), ASES (American Shoulder and Elbow Surgeon), OSQ (Oxford Shoulder Questionnaire) and SST (simple Shoulder test) were chosen. Outcomes of our series were statistically compared with literature data and widely analyzed. This kind of data are unavailable in literature and could represent the first step towards the definition of outcome for this kind of procedure.
High tibial osteotomy is an efficient treatment for medial compartment osteoarthritis of the knee; its used for middle aged patients with high activity levels and can delay the need for total arthroplasty. The results of total knee arthroplasty after failed high tibial osteotomy are controversies; several authors reported inferior outcomes, but others have concluded that tibial osteotomy doesn’t bias following total arthroplasty. The aim of this study was to evaluate the results of failed high tibial osteotomy subsequently converted to total knee arthroplasty and compare the results to group of patients underwere primary arthroplasty; the authors evaluate some of technical problems that a previous high tibial osteotomy can generate, like scar tissue, patellar tendon shortening and changes of proximal tibial anatomy.
At an average of five years follow up, the clinical results of total knee arthroplasty after high tibial osteotomy were similar to those of primary knee prosthesis.
