Polyetheretherketone (PEEK) has been proposed as an implant material for femoral total knee arthroplasty (TKA) components. Potential clinical advantages of PEEK over standard cobalt chrome alloys include modulus of elasticity and subsequently reduced stress shielding potentially eliminating osteolysis, thermal conduction properties allowing for a more natural soft tissue environment, and reduced weight enabling quicker quadriceps recovery. Manufacturing advantages include reduced manufacturing and sterilization time, lower cost, and improved quality control. Currently, no PEEK TKA implants exist on the market. Therefore, evaluation of mechanical properties in a pre-clinical phase is required to minimize patient risk. The objectives of this study include evaluation of implant fixation and determination of the potential for reduced stress shielding using the PEEK femoral TKA component. Experimental and computational analysis was performed to evaluate the biomechanical response of the femoral component (Freedom Knee, Maxx Orthopedics Inc., Plymouth Meeting, PA; Figure 1). Fixation strength of CoCr and PEEK components was evaluated in pull-off tests of cemented femoral components on cellular polyurethane foam blocks (Sawbones, Vashon Island, WA). Subsequent testing investigated the cemented fixation using cadaveric distal femurs. The reconstructions were subjected to 500,000 cycles of the peak load occurring during a standardized gait cycle (ISO 14243-1). The change from CoCr to PEEK on implant fixation was studied through computational analysis of stress distributions in the cement, implant, and the cement-implant interface. Reconstructions were analyzed when subjected to standardized gait and demanding squat loads. To investigate potentially reduced stress shielding when using a PEEK component, paired cadaveric femurs were used to measure local bone strains using digital image correlation (DIC). First, standardized gait load was applied, then the left and right femurs were implanted with CoCr and PEEK components, respectively, and subjected to the same load. To verify the validity of the computational methodology, the intact and reconstructed femurs were replicated in FEA models, based on CT scans.Introduction
Methods and Materials
Total hip arthroplasty (THA) in patients with congenital dysplasia of the hip (CDH) is complex and challenging. The Crowe and Hartofilakidis classification systems are the most commonly used. However, neither encompasses the whole spectrum of disease and deformity and therefore does not guide modern surgical options. We present a new classification system which aims to guide surgical strategy by focusing on the three main areas of disease and deformity: The aim of this study is to assess the reliability of this new adult CDH classification system in the setting of THA. A sample size calculation showed 28 evaluations were required to reach a power of 85% (based on a kappa value of 0.4). The anterior-posterior pelvis and lateral hip radiographs of 30 hips, in 26 patients were evaluated by three Consultant Orthopaedic Surgeons using the classification detailed in table 1. A second evaluation, with the case order randomised, was performed after a minimum period of 1month. Randolph's free multi-rater Kappa co-efficient was used to assess for inter and intra- observer reliability and 95% confidence intervals were calculated.Background
Study design and Methods
To evaluate a panel of peripheral blood and synovial fluid biomarkers for the identification of periprosthetic joint infection PJI. Peripheral blood and synovial fluid measurements of CD64, IL-1a, IL-1b, IL-6, IL-8, IL-10, IL-17, Alpha Defensin and CRP were made on samples collected from patients with suspected PJI using a combination of flow cytometry (CD64), ELISA (Alpha Defensin) and MSD Electrochemiluminescence (IL-1a, IL-1b, IL-6, IL-8, IL-10, IL-17). Receiver operating characteristic (ROC) curves which combine sensitivity and specificity were created for each marker using GraphPad PRISM statistical software. The diagnosis of infection was based on MSIS major criteria.Aim
Method
The highly cross-linked polyethylene Exeter RimFit flanged cemented
acetabular component was introduced in the United Kingdom in 2010.
This study aimed to examine the rates of emergence of radiolucent
lines observed when the Rimfit acetabular component was implanted
at total hip arthroplasty (THA) using two different techniques: firstly,
the ‘rimcutter’ technique in which the flange sits on a pre-prepared
acetabular rim; and secondly, the ‘trimmed flange’ technique in
which the flange is trimmed and the acetabular component is seated
inside the rim of the acetabulum. The radiographs of 150 THAs (75 ‘rimcutter’, 75 ‘trimmed flange’)
involving this component were evaluated to assess for radiolucencies
at the cement/bone interface by three observers. Aims
Patients and Methods
Periprosthetic bone remodelling after Total Knee Arthroplasty (TKA) may be attributed to local changes in the mechanical strain field of the bone as a result of the stiffness mismatch between high modulus metallic implant materials and the supporting bone. This can lead to significant loss of periprosthetic bone density, which may promote implant loosening, and complicate revision surgery. A novel polyetheretherketone (PEEK) implant with a modulus similar to bone has the potential to reduce stress shielding whilst eliminating metal ion release. Numerical modelling can estimate the remodelling stimulus but rigorous validation is required for use as a predictive tool. In this study, a finite element (FE) model investigating the local biomechanical changes with different TKA materials was verified experimentally using Digital Image Correlation (DIC). DIC is increasingly used in biomechanics for strain measurement on complex, heterogeneous anisotropic material structures. DIC was used following a previously validated technique [1] to compare bone surface strain distribution after implantation with a novel PEEK implant, to that induced by a contemporary metallic implant. Two distal Sawbone® femora models were implanted with a cemented cobalt-chromium (CoCr) and PEEK-OPTIMA® femoral component of the same size and geometry. A third, unimplanted, intact model was used as a reference. All models were subjected to standing loads on the corresponding UHMWPE tibial component, and resultant strain data was acquired in six repeated tests. An FE model of each case, using a CT-derived bone model, was solved using ANSYS software.Introduction
Methodology
Excision of prominent metatarsal heads for severe rheumatoid forefoot deformity is well established in clinical practice but results may deteriorate with time. The Stainsby forefoot arthroplasty however, recognises the pathological anatomy of the deformity and is designed to preserve the metatarsal heads by repositioning the plantar plates and forefoot fat pad underneath them. A prospective case series observing the clinical outcomes and changes in pedobarograph patterns in rheumatoid arthritis patients with severe deformity undergoing Stainsby forefoot arthroplasty.Introduction
Design
Membrane type 1 matrix metalloproteinase (MT1-MMP) plays a role in the progression of several common solid cancers. Given that osteosarcoma features extensive local invasion and haematogenous metastases, we hypothesised that osteosarcoma cells utilise MT1-MMP to drive these processes. Moreover, since hypoxia regulates MT1-MMP expression in breast cancer we investigated the effects of hypoxia on MT1-MMP expression in osteosarcoma cells.
Examination of MT1-MMP expression in osteosarcoma biopsy tissue in relation to clinical outcome Assessment of MT1-MMP, together with hypoxia inducible factors HIF-1α and HIF-2α expression in a panel of osteosarcoma cell lines under normoxia and hypoxiaBackground
Aims
To review the results of patients who underwent fixation of complex proximal femur fractures using the Proximal Femur Locking Plates (PFP) and analyse causes of failure of PFP. Retrospective review of radiographs and case notes of PFP fixations in two hospitals between February 2008 and June 2011. Primary outcome was union at six months. Secondary outcome included post-operative complications, and need for further surgical intervention.Aim
Methods
The prevalence of HIV infection in East Africa has increased rapidly in recent years. We made a prospective study of the incidence of HIV-seropositivity in patients undergoing orthopaedic procedures in a large district hospital in Bulawayo, Zimbabwe. One of our aims was to determine whether a clinically-based screening programme, derived from the Centre for Disease Control classification of HIV infection, could identify high-risk individuals before surgery. During a 3-month period, 76 patients were tested, and 12 were HIV-positive (16%). Only two of these patients (17%) had clinical features associated with HIV infection; ten (83%) were entirely asymptomatic. Our results indicate that preoperative clinical screening is unlikely to be successful in identifying seropositive patients before routine surgery.
