First Biomimetic Fixation for Resurfacing Arthroplasty: Investigation in Swine of a Prototype Partial Knee Endoprosthesis

Resurfacing hip and knee endoprostheses are generally embedded in shallow, prepared areas in the bone and secured with cement. Massive cement penetration into periarticular bone, although it provides sufficient primary fixation, leads to the progressive weakening of peri-implant bone and results in failures. The aim of this paper was to investigate in an animal model the first biomimetic fixation of components of resurfacing arthroplasty endoprostheses by means of the innovative multispiked connecting scaffold (MSC-Scaffold). The partial resurfacing knee arthroplasty (RKA) endoprosthesis working prototype with the MSC-Scaffold was designed for biomimetic fixation investigations using reverse engineering methods and manufactured by selective laser melting. After Ca-P surface modification of bone contacting surfaces of the MSC-Scaffold, the working prototypes were implanted in 10 swines. Radiological, histopathological, and micro-CT examinations were performed on retrieved bone-implant specimens. Clinical examination confirmed very good stability (4 in 5-point Likert scale) of the operated knee joints. Radiological examinations showed good implant fixation (radiolucency less than 2 mm) without any signs of migration. Spaces between the MSC-Scaffold spikes were penetrated by bone tissue. The histological sections showed newly formed trabecular bone tissue between the spikes, and the trabeculae of periscaffold bone were seen in contact with the spikes. The micro-CT results showed the highest percentage of bone tissue ingrowths into the MSC-Scaffold at a distance of 2.5÷3.0 mm from the spikes bases. The first biomimetic fixation for resurfacing arthroplasty was successfully verified in 10 swines investigations using RKA endoprosthesis working prototypes. The performed research shows that the MSC-Scaffold allows for cementless and biomimetic fixation of resurfacing endoprosthesis components in periarticular cancellous bone.

Assessment of Loosening and Rotational Malalignment Following Knee Endoprosthesis or Other Surgical Components

Total knee arthroplasty (TKA) has significant medical and economic implications. The correct placement of the femoral and tibial components is vital to ensure a functional knee and also low failure and revision surgery rates. This article provides the most relevant information regarding knee endoprosthesis from a radiologic point of view. Basic information on the recommended alignment of the femoral and tibial components in TKA and how to measure them are discussed. We then present the most important axial plane rotational references for the femoral and the tibial components. The optimal coronal alignment, illustrating the axes of the lower limb, and loosening as the major complication are also discussed. Finally, we offer a detailed example of rotational assessment.

Analysis of inpatient costs in patients with knee osteoarthritis treated by implantation of total condylar knee endoprosthesis

Background/Aim. Total knee replacement is an elective and high cost surgical procedure which is performed more frequently as a result of increasing prevalence of knee osteoarthritis. The aim of this study was to provide insight into the value and structure of inpatient costs associated with total knee replacement in Serbia. Methods. This study was conducted as an in-depth, bottom-up, retrospective, case series analysis of services consumption patterns and costs associated with inpatient treatment of patients with knee osteoarthritis by implantation of primary total condylar knee endoprosthesis from perspective of the national Republic Health Insurance Fund. We obtained data on 97 patients treated with primary unilateral or bilateral total knee replacement in 2014 at the Clinic for Orthopaedic Surgery and Traumatology of the Military Medical Academy in Belgrade, a tertiary health care university hospital. Results. Mean age of entire study sample was 67.89 years. Majority of patients (60 patients; 61.9%) had unilateral implantation of total condylar knee endoprosthesis. Bilateral implantation was performed in 37 (38.1%) patients. Mean total inpatient cost per patient for both unilateral and bilateral implantation of total condylar knee endoprosthesis was EUR 2,709.1, ranging from EUR 1,685.2 to EUR 5,356.6. Mean total inpatient cost per patient was EUR 2,093.8 for unilateral implantation and EUR 3,706.8 for bilateral implantation. Two major cost drivers were surgery specific material and surgery. Cost of implants was the highest single cost driver in all observed groups of patients. Conclusion. Our findings imply that inpatient costs associated with implantation of primary total condylar knee endoprosthesis are substantial. It seems that the most important cost drivers are surgery and surgery specific material, with implants being the highest single cost driver. Further research should be focused on analyzing factors that influence these costs in order to develop effective strategies which could contribute to substantial savings in the future.