Aims

To explore the clinical efficacy of using two different types of articulating spacers in two-stage revision for chronic knee periprosthetic joint infection (kPJI).

Fractures of the prosthetic components after total knee arthroplasty (TKA) are rare but dangerous complications, sometimes difficult to diagnose and to manage. Aim of this study is to evaluate the incidence of component breakage and its treatment in our single institution's experience. We retrospectively review our institution registry. From 605 revision knee arthroplasties since 2000 to 2018, we found 8 cases of component breakage, of these 3 belonged to UKA, and 5 belonged to TKA. The UKA fractures were all on the metal tibial component; while 4 TKA fractures were ascribed to the liner (2 Posterior-Stabilized designs and 2 constrained designs) and only one case was on the femoral component. For every patient a revision procedure was performed, in two cases a tibial tubercle osteotomy was performed, while in one case (where the fracture was of the post cam) an arthroscopy was performed prior to the arthrotomy. All of the UKA fractures were treated with a standard revision implant. As regard the TKA, 2 liner fractures were treated with the only liner exchange, while the other 2 liner fractures and the fracture of the metallic component were treated with total knee revision. No intra- and post-operative complications were found. Component breakage after TKA is a serious complication. Its treatment, always surgical, can hide pitfalls, especially if the timing is not correct; indeed apart from the revision of one or more components, the surgeons must address any issues of management of bone defect and ligamentous stability

Aim. One of the most severe complications of primary total knee arthroplasty (TKA) is periprosthetic joint infection (PJI). Nowadays, the use of antibiotic-loaded cement for prevention of infection is still controversial. The aim of the present study is to evaluate the use of an antibiotic-loaded cement to reduce the infection rate in primary total knee arthroplasty. Method. Prospective randomized study, with 2893 cemented total knee arthroplasties performed between 2005 and 2010 in our institution. Two different groups were formed depending on which bone cement was used, without antibiotic (the control group) or loaded with erythromycin and colistin (the study group). All patients received the same systemic prophylactic antibiotics. The patients were followed for a minimum of twelve months. The rate of infection was analyzed according to the criteria of the Centers for Disease Control and Prevention (CDC). Results. In 1452 patients the prosthetic components were fixed using bone cement without antibiotic and in 1441 patients bone cement loaded with erythromycin and colistin was used. There were no differences between both groups in terms of demographic data (age, sex and BMI), either in operating time (p>0,05). The rate of infection was similar in both groups, being 2,0% (n=29) in the control group and 1,7% in the study group (p=0,58) at 8,7 years (SD 5,1) of follow up. In terms of prosthetic revision due to any cause (infected or aseptic), there wasn't differences between groups, performing a total of 61 revision arthroplasties in control group and 68 in study group (p>0,05). Moreover, we analyzed the erythromycin resistance rate, being no differences between both groups (p=0.6). Conclusions. The use of erythromycin and colistin-loaded bone cement in total knee arthroplasty did not lead to a decrease in the rate of infection when systemic prophylactic antibiotics were used, a finding that suggests that its use would not be indicated in the general population

Introduction and Objective. TKA have shown both excellent long-term survival rate and symptoms and knee function improvement. Despite the good results, the literature reports dissatisfaction rates around 20%. This rate of dissatisfaction could be due to the overstuff that mechanically aligned prostheses could produce during the range of motion. Either size discrepancy between bone resection and prosthetic component and constitutional mechanical tibiofemoral alignment (MTFA) alteration might increase soft tissue tension within the joint, inducing pain and functional limitation. Materials and Methods. Total knee arthroplasties performed between July 2019 and September 2020 were examined and then divided into two groups based on the presence (Group A) or absence (Group B) of patellofemoral overstuff, defined as a thickness difference of more than 2 mm between chosen component and bone resection performed, taking into account at least one of the following: femoral medial and lateral condyle, medial or lateral trochlea and patella. Based on pre and post-operative MTFA measurements, Group A was further divided into two subgroups whether the considered alignment was modified or not. Patients were assessed pre-operatively and at 6 months post-op using the Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Visual Analogue Scale (VAS) and Range of Motion (ROM). Results. One hundred total knee arthroplasties were included in the present study, 69 in Group A and 31 in group B. Mean age and BMI of patients was respectively 71 and 29.2. The greatest percentage of Patellofemoral Overstuff was found at the distal lateral femoral condyle. OKS, KSS functional score, and FJS were statistically significant higher in patients without Patellofemoral Overstuff. Therefore, Group A patients with a non-modified MTFA demonstrated statistically significant better KSS, ROM and FJS. Conclusions. Patellofemoral Overstuff decrease post-operative clinical scores in patients treated with TKA. The conventional mechanically aligned positioning of TKA components might be the primary cause of prosthetic overstuffing leading to worsened clinical results. Level of evidence: III; Prospective Cohort Observational study;

Aim: To develop a 3-D pre-surgical planner that facilitates selection and placement of correct prosthetic components in the joint, and the design of patient specific templates to use intra-operatively to reproduce the pre-planned implantation procedure, in total knee replacement (TKR) surgery. Design/Methods: The process begun with loading of pre-operative CT scan data of cadaver knee, onto medical software, followed by reconstructions of 3D models of the joint. Then measurements of anterior-posterior diameter of the femoral condyles of the 3D models of the joint were used to select and import a correct CAD drawing of prostheses from a database of electronic files available in a range of sizes. The selected prosthetic components were positioned and aligned on the 3-d model of the joint, making sure that the anterior flange of the femoral prosthesis component did not violate superior cortical bone of trochlea. Whilst the tibial stem was placed central within the medullar space of the bone, and the plane of the tibial cut was perpendicular to the long axis of the tibia. The planned data were next exported to a CAD environment where template to prepare the bone to receive the prostheses, was designed. A template was designed to press fit on a bone (e.g. femur), via minimum number of cylindrical protrusions with their ends made to conform to the geometry of that bone at the regions of contact. The integrated surgical tools were secured to the bones with pins through each of the protrusions, and were equipped with saw guide slits for cutting the bone, and with drill guides for drilling the fixation holes. Thereafter the files describing templates and prosthetic components selected for cadaveric joint concerned were sent to rapid prototyping machine for manufacturing. Results: Fourteen procedures were performed on cadaveric knees to date. Visual examination of the joint has revealed the 3-D planning system enabled correct selection of appropriate prosthetic components and alignment, as evidenced by absence of protrusions or overhanging beyond the edges of the bones. The resected bone surfaces were visually smooth and flat. Gaps between the bones and the internal surfaces of the prosthetic components were measured using steel shim gauges, and largest recorded was 0.9mm. Laxity between the femur and tibia was absent and the joint attained full range of flexion. Dimensional deviations of post-operative scans of the prepared bones from the pre-planned ones were between 0.5 and 0.9mm. The templates after their use were shown capable to withstand the rigors of theatre environment. Conclusion: With the planning software, it has been shown that it is possible to design a simple to use implantation guidance system according to the final position of the restorative prosthesis and the bone pathological condition. Pre-operative planner system relieves the clinician from multiple intra-operative decisions. The system is ideal for critical anatomical situations and eliminates possible manual placement errors such as those from extra and intra-medullary alignment tool. Less inventory required of both implants and instrumentation means reduced complexity of procedure, surgical time and cost

Introduction. Robotics have been applied to total knee arthroplasty (TKA) to improve surgical precision in component placement and joint function restoration. The purpose of this study was to evaluate prosthetic component alignment in robotic arm-assisted (RA)-TKA performed with functional alignment and intraoperative fine-tuning, aiming for symmetric medial and lateral gaps in flexion/extension. It was hypothesized that functionally aligned RA-TKA the femoral and tibial cuts would be performed in line with the preoperative joint line orientation. Methods. Between September 2018 and January 2020, 81 RA cruciate retaining (CR) and posterior stabilized (PS) TKAs were performed at a single center. Preoperative radiographs were obtained, and measures were performed according to Paley's. Preoperatively, cuts were planned based on radiographic epiphyseal anatomies and respecting ±3° boundaries from neutral coronal alignment. Intraoperatively, the tibial and femoral cuts were modified based on the individual soft tissue-guided fine-tuning, aiming for symmetric medial and lateral gaps in flexion/extension. Robotic data were recorded. Results. A total of 56 RA-TKAs performed on varus knees were taken into account. On average, the tibial component was placed at 1.9° varus (SD 0.7) and 3.3° (SD 1.0) in the coronal and sagittal planes, respectively. The average femoral component alignment, based on the soft tissue tensioning with spoons, resulted as follows: 0.7° varus (SD 1.7) in the coronal plane and 1.8° (SD 2.1) of external rotation relative to surgical transepicondylar axis in the transverse plane. A statistically significant linear direct relationship was demonstrated between radiographic epiphyseal femoral and tibial coronal alignment and femoral (r=0.3, p<0.05) and tibial (r=0.3, p<0.01) coronal cuts, resepctively. Conclusion. Functionally aligned RA-TKA performed in varus knees, aiming for ligaments’ preservation and balanced flexion/extension gaps, provided joint line respecting femoral and tibial cuts on the coronal plane

Computer-assisted techniques in total knee replacement (TKR) have been introduced to improve bone cuts execution and relevant prosthesis components positioning. Although these have resulted in good surgical outcomes when compared to the conventional TKR technique, the surgical time increase and the use of additional invasive devices remain still critical. In order to cope with these issues, a new technology in TKR has been introduced also for positioning prosthetic components according to the natural lower-limb alignment. This technique is based on custom-fit cutting block derived from patient-specific lower-limb scan acquisition. The purpose of this study is to assess the accuracy of the custom-fit technology by means of a knee surgical navigation system, here used only as measurement system, and post-operative radiographic evaluations. Particularly, the performances of two different custom-fit cutting blocks realized from as many scan acquisitions have been here reported. Thirty patients affected by primary knee osteoarthritis were enrolled in this study. Fifteen patients were implanted with GMK® (Medacta-International, Castel San Pietro, CH) and as many patients with Journey® (Smith&Nephew, London, UK). Both TKR designs were implanted by using custom-fit blocks for bone cut executions provided by the same TKR manufacturers according to a pre-operative web planning approved by the surgeon. Particularly, the cutting block for the former design was built from CT scan acquisition of the hip, knee and ankle, whereas that for the latter design from MRI scans acquisition of the knee and X-ray lower-limb overview. A knee surgical navigation system (Stryker®-Leibinger, Freiburg, Germany) was used for recording intra-operative alignment of bone cuts as performed by means of the custom-fit cutting blocks and relevant component positioning. Prosthetic components alignments were also assessed post-operatively on X-ray images according to a shape-matching technique. The accuracy of the custom-fit blocks was evaluated through the comparison between pre-operative planning, and intra/post-operative data. Discrepancies above 3° and millimeters were considered as outliers. Within the patient cohort, nine cases were fully analyzed at the moment and here reported. Over them and except for one case, the discrepancy between pre-operative planned femoral/tibial resection level on the frontal plane and the corresponding measured intra-operatively was within 3 mm, being 5 mm in the worse case. Two outliers were observed for the corresponding femoral/tibial cut rotational alignment. Particularly, in one patient, the discrepancy in femoral cut alignment was of 8° in flexion and 6° in external rotation; in another patient this was of 4° in extension and 4° in external rotation in the femoral and tibial cut alignment, respectively. Post-operative radiographs evaluations for the final prosthetic components revealed that femoral/tibial alignment were within 3° in all cases, except for those patients that were already outliers. These preliminary results reveal the efficacy of the custom-fit cutting block for TKR. These were generally fitted properly and final prosthetic components were accurately placed, although some discrepancies were observed. This new technology seems to be a valid alternative to conventional and computer-assisted techniques. More consistent conclusions can be deduced after final evaluation of all patients

Hips and knees are commonly replaced joints for which several types of prostheses are available. As newer versions of the prostheses are brought in, older versions are phased out. When revision is for an isolated component failure as in, wear of acetabular cup, isolated revision of the acetabular cup is an accepted procedure. If the plan is to revise just the isolated component then that particular model of prosthesis should still be available. In an attempt to check the availability of revision components for joint replacements we wrote to ten prostheses manufacturers enquiring the availability of prosthetic components. To have a comparison, we also wrote to eighteen leading car manufacturers enquiring about the duration and any guarantees on the availability of car spare parts. From our survey we found that the availability of the revision implants was satisfactory in that all the prostheses manufacturers were eager to provide as much assistance as possible. The draw back is that there are no regulations to ensure the availability of these prosthetic components for any length of time after discontinuation of a particular model. The car manufacturers are not under any obligation to provide spare parts for discontinued models. The argument put forward by some manufacturers for providing spare parts up to ten years from discontinuing the model was that “it would not reflect well on the company” if it were for any lesser length of time. Conclusion: At present though there are no regulations on the time period of availability of total joint prosthetic components. The manufacturers have taken it upon themselves to provide the prosthetic components whenever a specific request is made. If the manufacturers say they can not provide the implants there is nothing in the governmental regulations that provide for recourse

A near real-time, image-free, contact-determination algorithm is developed for the use of analyzing in vivo kinematics of an artificial knee joint. Using a three-dimensional motion tracker and the knowledge of the precise geometries of the contacting surfaces, the contact regions between two articular surfaces can be determined within seconds. The results are validated with the use of Fuji films, which show high degree of accordance in the contact regions determined. Applications include knee kinematics validation, TKA wear-pattern analysis, and intro-operative surgical assessment. To determine the in vivo contact locations between total knee prosthetic components without the use of any imaging modality. Validated with the Fuji film contact study, this computer algorithm provides an image-free, and accurate way of finding contact regions between prosthetic components. An image-free, near real-time, algorithm is developed to study the in vivo contact condition between prosthetic components. A Dynamic Reference Body (DRB) is attached to each of the Total Knee Arthroplasty component and their motions, while in contact with each other, are tracked with an optical spatial sensor. The geometries of the articular surfaces, represented in point-clouds with point-normal, were obtained from a laser-scanner at 0.4mm resolution. For each recorded pose, the contact between articular surfaces were determined by first matching point normal and then performing a nearest-point search, both facilitated by the use of a generalized binary-search-tree (kd-tree). A size-3 Sigma Knee (Johnson& Johnson), represented by approximately 31,000/19,000 points for each of the femoral/tibial component, respectively, is used for this study. For each pose, the contact between components can be determined under one second on a 2GHz PC, rendering it applicable for intra-operative use. The contacts between prosthetic components are visualized using standard computer graphics techniques and contrasted with the contact obtained by Fuji film of the same pose. Depicted below, the contact regions determined by these two methods show high degree of accordance with each other. This allows for, in particular, an image-free TKA wear-pattern analysis. Please contact Author for diagrams

Patellar tracking is the most common complication observed following total knee arthroplasty. It may constitute a minor disorder or even frank dislocation. Its main cause is a rotation defect in the prosthetic components. CT is the most reliable instrumental test to assess this rotation defect, and an excellent aid for planning a possible revision operation. From January 1999 to November 2003 we treated 33 patients with a total of 35 painful knees using TC prostheses. Ten patients were male and 33 female. Mean age was 66 years. We performed CT scanning using a modified Berger technique. The lower limbs were extended and scans were performed perpendicular to the mechanical axis of the knee from the supracondylar region of the femur to the plane passing under the distal end of the tibial component up to the anterior tibial tuberosity. Reference lines to assess the rotation of each prosthetic component were drawn electronically on the scan planes. Adding together the rotation values of the prosthetic components, we observed that when total internal rotation was between 10° and 4°, there was subluxation or frank dislocation. When total internal rotation was between 1° and 4° the disorder was not severe, such as patellar tilt. When total internal rotation was less than 1° or when the components were externally rotated, no femorotibial compartment disorders were observed. The modified Berger technique enabled us to correlate the degree of prosthetic internal rotation with the severity of the disorder and further demonstrate the benefits of femoral component external rotation on patellar glide and ligament balance of the prosthesis. The authors believe that using CT with the helicoidal technique, by modifying Berger’s technique, enables an accurate assessment of prosthetic component rotation, subsequent correlation with femoro-patella symptoms, and adequate pre-operative planning in case of revision surgery

Background. The current use of a spherical prosthetic humeral head in total shoulder arthroplasty results in an imprecise restoration of the native geometry and improper placement of the center of rotation, maintained in a constant position, in comparison to the native head and regardless of glenoid component conformity. A radially-mismatched spherical head to allow gleno-humeral translation is a trade-off that decreases the contact area on the glenoid component, which may cause glenoid component wear. This finding suggests that the use of a non-spherical head with a more conforming glenoid component may reduce the risk of glenoid component wear by allowing gleno-humeral translation while increasing the contact area. A non-spherical prosthetic head more accurately replicates the head shape, rotational range of motion and gleno-humeral joint kinematics than a spherical prosthetic head, compared with the native humeral head. The combination of inversion of the bearing materials with the non-spherical configuration of the humeral head may thus decrease polyethylene wear. Aim of the present study is to evaluate in vitro wear behaviour of an all-polyethylene elliptical humeral head component against a metallic glenoid component in an anatomic configuration. Material and methods. The prosthetic components tested are from the Mirai. ®. Modular Shoulder System by Permedica S.p.A.. The prosthetic bearing components were tested in their anatomic configuration: the humeral head rubbing against the glenoid inlay, assembled over the glenoid base-plate. The glenoid insert is made of Ti6Al4V alloy coated with TiNbN. The glenoid insert, as the glenoid base-plate have the same shape which reproduce the native shape of the glenoid. Moreover, the glenoid insert has a concave articular surface described by two different radii on orthogonal planes. The vitamin E-blended UHMWPE humeral head is not spherical but elliptic-shaped with an articular surface described by two different profiles in sagittal and coronal plane. The component sizes combination tested have the greatest radial mismatches allowed between humeral head and glenoid insert. The test was performed up to 2.5 million of cycles applying a constant axial load of 756 N. Results. After 2.500.000 cycles the mean mass loss from the humeral head was 0.68 mg. The mean wear rate of the humeral head was 0.28 mg/Mc (SD 0.45 mg/Mc). The surface of the humeral heads showed an elliptical worn area with matt and polished areas with scratching. The surface of the TiNbN-coated glenoid insert counterparts did not show wear signs. Conclusion. The tested prosthetic humeral head has a non-spherical shape with an elliptical base and 2 different radii on sagittal and coronal plane. Also the tested glenoid insert has 2 different radii on sagittal and coronal planes. This components geometry leads to a radial mismatch between head and glenoid on sagittal and coronal planes. A different kinematics, allowing gleno-humeral translation while increasing the contact area, radial mismatch in different planes and the inversion of bearing materials may have a role in reducing component wear and may explain the extremely low wear rate found in the present study

Introduction. Functional outcomes of mechanically aligned (MA) total knee arthroplasty have plateaued. The aim of this study is to find an alternative technique for implant positioning that improves functional outcomes of TKA. Methods. We prospectively randomized 100 consecutive patients undergoing TKA into two groups: in the group A an intramedullary femoral guide and an extramedullary tibial guide were used with aim to obtain a neutral traditional mechanical alignment; in the group B an extramedullary femoral guide set on distal femoral condyles and an extramedullary tibial guide neutrally aligned were used to obtain an adaptation of the conventional MA technique. Patients were followed-up clinically with the Short Form Health Survey (SF-12), Oxford Knee Score (OKS) and Visual Analogue Score (VAS) questionnaires pre-operatively and then at 1 year post-operatively. Mechanical alignment was calculated on standing weight bearing Xray pre- and post-operatively. T-test was used to compare the results between groups. Results. Both groups showed an improvement of clinical scores. At 1 year of follow-up OKS and SF-12 were significantly higher in group B: 47,6 ±0.75 and 46.5 ±0.76 respectively; VAS was similar in both groups. Values of mechanical alignment changed from 6.45 ±8.45 to 0.25 ±0.91 for group A and from 6.8 ±7.94 to 2.5 ±4.7 for group B. Conclusion. This study shows that adjusted mechanical alignment (AMA) with a small under-correction of frontal deformity lead to improved functional scores following total knee replacement compared to conventional technique of neutral alignment. These results are satisfactory at short follow-up but long-term studies are needed to evaluate the difference in the rate of wear of the prosthetic components

Aims. The aim of this to study was to compare the previously unreported long-term survival outcome of the Oxford medial unicompartmental knee arthroplasty (UKA) performed by trainee surgeons and consultants. . Patients and Methods. We therefore identified a previously unreported cohort of 1084 knees in 947 patients who had a UKA inserted for anteromedial knee arthritis by consultants and surgeons in training, at a tertiary arthroplasty centre and performed survival analysis on the group with revision as the endpoint. Results. The ten-year cumulative survival rate for revision or exchange of any part of the prosthetic components was 93.2% (95% confidence interval (CI) 86.1 to 100, number at risk 45). Consultant surgeons had a nine-year cumulative survival rate of 93.9% (95% CI 90.2 to 97.6, number at risk 16). Trainee surgeons had a cumulative nine-year survival rate of 93.0% (95% CI 90.3 to 95.7, number at risk 35). Although there was no differences in implant survival between consultants and trainees (p = 0.30), there was a difference in failure pattern whereby all re-operations performed for bearing dislocation (n = 7), occurred in the trainee group. This accounted for 0.6% of the entire cohort and 15% of the re-operations. . Conclusion. This is the largest single series of the Oxford UKA ever reported and demonstrates that good results can be achieved by a heterogeneous group of surgeons, including trainees, if performed within a high-volume centre with considerable experience with the procedure. Cite this article: Bone Joint J 2016;(10 Suppl B):22–7

In the congenital hip dysplasia, patients treated with total hip replacement (THR) often report persistent disability and pain, with unsatisfactory function and quality of life. A major challenge is to restore the center of rotation of the hip and a satisfactory abduction function [1]. The position of the acetabular cup during THR might be crucial, as it affects abduction moment and motor function. Recently, several software systems have been developed for surgical planning of endoprostheses. Previously developed software called HipOp [2], which is routinely used in clinics, allows surgeons to properly position the prosthetic components into the 3D space of CT data. However, this software did not allow to simulate the articular range of motion and the condition of the abductor muscles. Our aim is to present HipOpCT, an advanced version of the software that includes 3D musculoskeletal planning, through the application to hip dysplasia patients to add knowledge in the diagnosis and treatment of such patients who need THR. 40 hip dysplasia patients received pre-operative CT scanning of pelvis and thighs and had their THR surgery planned using HipOpCT. The base planning includes import of CT data, positioning of prosthetic components interactively through multimodal display, as well as geometrical measurements of the implant and the host bone. The advanced planning additionally includes evaluation of femoro-acetabular impingement and calculation of leg lengths, abductor muscle lengths and lever arms through the automatic creation of a musculoskeletal model. The musculoskeletal parameters in all patients were calculated during the surgical planning, and the data were processed to evaluate pre- and post-operative differences in leg length discrepancy, length and lever arm of the abductor muscles, and how these parameters correlated. The surgical planning led to an increase in the operated leg length of 7.6 ± 5.7 mm. The variation in abductors lever arm was −0.9% ± 4.8% and significantly correlated with the variation in the operated leg length (r = −0.49), pre-operative leg length discrepancy (r = 0.32) and variation in abductors length (r = −0.32). The variation in abductors length was 6.6% ± 5.5%, and significantly correlated with the variation in the operated leg length (r = 0.92), post-operative leg length discrepancy (r = 0.37), pre-operative abductors length (r = −0.37) and variation in abductors lever arm (r = −0.32). The increase in the operated leg length was strongly correlated to the increase in abductor muscle length. Conversely, abductor lever arms slightly decreased on average, and were inversely correlated to leg length variation and abductors lengths. This interactive technology for surgical planning represent a powerful tool for orthopaedic surgeons to consider the best muscle reconstruction, and for rehabilitation specialists to achieve the best functional recovery based on biomechanical outcomes. In a parallel study, we are investigating how these advanced planning is reflected onto the function, pain and biomechanical outcome after a rehabilitation protocol is completed

Purpose: Kinematics of the total knee arthroplasty plateau has been widely studied. Many methods can be used: opto-electronic captors, electromagnetic knee device, radiography, repositioning with the CAO model. We report a simple method based on calculating the position of two radio-opaque markers and the contours of the prosthetic components. Material and methods: Twenty patients with a unilateral mobile plateau total knee arthroplasty were studied. An image amplifier linked to a digital recorder (frequency 25 Hz), CAO models of the implant, and adapted software (Matlab) were used. Each patient performed a series of movements, standing up from the sitting position, within the fluoroscopic field. Each sequence was digitalized. Kinematic images were sampled at 6 Hz. Different parameters were measured on each sampled image: position of two radio-opaque markers included in the polyethylene insert and characteristic dimensions of the prosthesis components. These 2D recordings were used to deduct the relative 3D position of each of the prosthetic components. Laws of analytic geometry and functional analysis were used to resolve the triangular matrices needed to transform the 2D measures into 3D values. Angular and linear positions of the prosthetic components were established for different times t. Reconcatenation by time produced an kinematic analysis of the pros-thesis behaviour. Results: This method allowed us to establish the kinematics of the total knee arthroplasty mobile plateau with a precision of 0.2 mm and 0.4°. The proposed analysis method is reliable and precise. It is less costly in development time than methods based on automatic repositioning of 3D models of the implant on fluoroscopic images. Conclusion: The measurement method proposed requires radio-opaque markers positioned in orthogonal directions so they are visible during movements. Although we used a semi-automatic calculation protocol, totally automatic systems can be applied to process fluoroscopic images

Introduction. Protective hard coatings are appealing for several technological applications and even for orthopaedic implants and prosthetic devices. For what concerns the application to prosthetic components, coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1, 2]; at the same time, concerning use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) ceramic material has shown high strength, fracture toughness, elasticity, hardness, and wear resistance [3, 4]. The purpose of this study was to directly deposit ZTA coatings by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [5]. Preliminary characterization of realized coatings from the point of view of morphology, wettability, adhesion and friction coefficients was performed. Materials and methods. PPD technique was used to deposit ZTA coatings; this technique is able to maintain the stoichiometry of the starting target. In this study we started from a cylindrical ZTA target (30 mm diameter × 5 mm thickness, 75% alumina / 25% zirconia) and followed the procedure described by Bianchi et al [5]. Characterization of morphology, micro-structure and chemistry of deposited coatings was performed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) and Atomic Force Microscope (AFM). Coating-substrate interface quality were investigated by micro-scratch tests. Measurement of the contact angle between a drop of 1 ml of ultrapure water and the surface of the sample was performed to estimate the degree of wetting. A ZTA-coated stainless steel ball (AISI 420, 3 mm radius) was coupled against medical grade UHMWPE to evaluate the friction of the proposed coupling in preliminary ball-on-disk tribological tests. Results. Coatings up to several microns thick have been deposited by PPD. Deposited ZTA films exhibited a smooth nanostructured surface. Mechanical tests showed a well-adherent films were deposited. In particular, scratch tests assessed a good interface adhesion: first formation of cracking in the coating during testing was reported at about 0.8 N. Hydrophobic behavior of the coating was revealed by contact angles (average contact angle 116° ± 2°), probably due to the nano-roughness of the coating itself. Good average friction coefficient ranging from 0.12 to 0.15 was showed by preliminary tribological tests carried out in deionized water after up to 10000 m tracks. Conclusions. The preliminary results of a novel approach aiming to drastically improve the performance of prosthetic couplings by introducing hard ceramic coating was presented. Showed results suggested the feasibility of pursuing this approach of realizing ZTA coatings by means of PPD technique. Further analyses on mechanical properties, nanoroughness and tribology are ongoing. Well-adherent ZTA films deposited directly on the prosthetic components surface would then allow a drastic improvement of the actual prosthetic behaviour

Aim. At present, a variety of clinical guidelines for treatment of periprosthetic joint infections (PJI) inevitably lead to a variety in outcomes by differing case management. Ideally a treatment algorithm should incorporate all components contributing to the decision-making process for a patient tailored solution in PJI. We aim to present a comprehensive and reproducible treatment algorithm based on a validated staging system, a thorough understanding of the host, the causative microbiome and implant complexity. Method. The diagnosis of a PJI was defined according to major and minor criteria following revised International Consensus Symposium algorithm. The validated McPherson staging system was used in our university hospital from January 2015 until January 2019 in referred PJI patients. Standardised preoperative and postoperative survey documents were completed in order to register data from the patient's medical, social and surgical history. The complexity of the infected implant was taken into consideration, including quantity of preceding procedures, residual bone stock, type of fixation, magnitude of prosthetic components and presence or absence of reconstructive options. Further, preoperatively obtained bacteriological information by means of arthrocentesis or tissue/bone biopsies was categorized according to the mono- or polybacterial nature and to the qualification of virulence and difficulties to treat. Social and professional history, financial impediments and patient's functional outcome wishes were included in the joint decision making. Results. We present our comprehensive PJI treatment algorithm. The ‘deTerminators’ we included are a validated staging system focused on the host, the amount of unsuccessful prior attempts, the difficult to treat character of the microbiome, the implant complexity, anatomical location and socioeconomic patient derived factors. Furthermore, we call for source control by minimally invasive means or late DAIR in complex case management combined with lifelong suppressive antibiotic therapy with maintenance of quality of life as the main outcome instead of curative intention. Conclusions. We present a comprehensive treatment algorithm based on an expanded McPherson staging system coupled with bundled clinical, technical, social and psychological data which should assist the surgeon and the patient to make informed choices. We hope that usage and testing of our algorithm in other centers could further demonstrate its usefulness

Background. The main reasons for hip prosthesis failure are aseptic loosening and periprosthetic joint infection (PJI). The real frequency of PJI is probably largely underestimated because of non-standardized definition criteria, diagnostic procedure, treatment algorithm and other confounders. Therefore, data from joint registries are not reflecting the frequency of PJI and can be misleading; particularly low-grade PJI can be frequently misdiagnosed as aseptic failure. Therefore, prospective clinical studies with standardized protocol, comprehensive diagnostic procedure and sufficient follow-up should be performed. Sonication of explanted prosthesis is highly sensitive for detection of biofilms on prosthetic surface and allows quantitative analysis of biofilm formation. We hypothesize that by using sonication, ceramic components (BIOLOX®delta, BIOLOX®forte) will show higher resistance against biofilm adhesion compared to polyethylene (PE) and metal (CoCrMo). Methods. In this prospective multicentre study (level of evidence: Ia), we included all consecutive adults ≥18 years of age, who underwent explantation of the hip prosthesis for infection or aseptic reason. Excluded were patients in whom part of the prosthetic components were retained. A standardized and comprehensive diagnostic algorithm was applied, including sonication of all removed prosthetic components for qualitative and quantitative microbiological analysis (ultrasound bath 40 kHz, 1 W/cm2, 1 min). Individual components (metal, PE, ceramic) were separately placed in sterile boxes for investigation. All patients were simultaneously included in the European Prosthetic joint infection cohort (EPJIC, . www.epjic.org. ) to ensure long-term follow-up. Results. Up to date, 79 patients were included, of whom 47 (60%) were diagnosed with aseptic failure and 32 (40%) with PJI. Mean age was 73 years (27–87 years), 32 (41%) were males. Table 1 summarizes the demographic characteristics. In 32 patients with PJI, most frequently isolated organisms were coagulase-negative staphylococci (n=12, 38%), Staphylococcus aureus (n=7, 22%) and Propionibacterium acnes (n=4, 13%), followed by enterococci (n=2; 6%) and gram-negative bacilli (n=2; 6%); 2 infections (6%) were polymicrobial and 3 were culture-negative (9%). Table 2 summarizes the microbiological results from sonication of removed components. Causative microorganism could be detected in sonication fluid from polyethylene in 100%, from metal in 92% and from ceramic in 69%. Significantly lower bacterial counts expressed as colony-forming units (CFU) were detected in sonication fluid from ceramic components (230 CFU/ml) than from PE (6’250 CFU/ml) and metal components (5’870 CFU / ml) (p < 0.01). Conclusions. These first results support the hypothesis that significantly less biofilm biomass is formed on ceramic surface, compared to PE and metal surfaces, potentially indicating higher ceramic “resistance” against bacterial adhesion. These findings should be confirmed with non-microbiological investigation such as imaging (fluorescent in situ hybridization, confocal laser scanning or electron microscopy). Furthermore, in 6 of 32 patients (19%) with PJI, an aseptic loosening was preoperatively suspected. Infection was found only by systematic application of an optimized diagnostic method, particularly sonication of the removed implant. Final study results are expected to be available by the end of 2016

Introduction. Protective hard coatings are appealing for several technological applications like solar cells, organic electronics, fuel cells, cutting tools and even for orthopaedic implants and prosthetic devices. At present for what concerns the application to prosthetic components, the coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1]. Concerning the use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) reported high strength, fracture toughness, elasticity, hardness, and wear resistance [2]. The main goal of this study was to directly deposit ZTA coating by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [3]. The realized coatings have been preliminary characterized from the point of view of morphology, wettability, adhesion and friction coefficients. Materials and methods. ZTA coatings were deposited by PPD technique, which is able to maintain the stoichiometry of the starting target. In this case we started from a cylindrical ZTA target (30 mm diameter × 5 mm thickness, 75% alumina / 25% zirconia). The morphology, micro-structure and chemistry of deposited coatings were characterized by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectrosopy (EDS) and Atomic Force Microcscope (AFM). Coating-substrate interface quality were investigated by microscratch tests. The degree of wetting was estimated by measuring the contact angle between a drop of 1 ml of ultrapure water and the surface of the sample. Preliminary ball-on-disk tribological tests were carried out in air and deionized water coupling ZTA-coated stainless steel ball (AISI 420, 3 mm radius, grade 200) against medical grade UHMWPE to evaluate the friction of the proposed coupling. Results. Deposited ZTA films exhibited a smooth nanostructured surface. Coatings up to several microns thick have been deposited by PPD [Fig. 1 – SEM image (left) and cross section (right)]. Mechanical tests showed a well-adherent films were deposited. In particular, the good interface adhesion was assessed by scratch tests, reporting at about 0.8 N the first formation of cracking in the coating during testing. The contact angles revealed an hydrophobic behavior of the coating (average contact angle 116° ± 2°), probably due to the nano-roughness of the coating itself [Fig. 2 – Contact angle]. Preliminary tribological tests carried out in deionized water after up to 10000 m tracks showed good average friction coefficient ranging from 0.12 to 0.15 [Fig. 3 – Friction coefficient]. Conclusions. We have presented the preliminary results of a novel approach aiming to the drastically improve the performance of prosthetic couplings by introducing hard ceramic coating. The results showed suggested the feasibility of pursuing this approach of realizing ZTA coatings by means of PPD technique. Further analyese on mechanical properties, nano-roughness and tribology should be performed. Well-adherent ZTA films deposited directly on the surface of prosthetic components of a joint implant would then allow a drastic improvement of the actual prosthetic behaviour

The assessment of large allografts in acetabular reconstruction surgery is notoriously difficult. Because of their invasive natures, methods such as tetracycline-labeled histological examination are not recommended. Radio-isotope studies are unreliable in assessing the degree of incorporation because labeled tissues remain hot for extended periods. CT scans are impractical because of the scatter generated by the metallic prosthetic components. We used DEXA to assess the quality of large acetabular bone grafts immediately after surgery and at regular intervals thereafter. Software programmes were used to subtract the prosthetic components and give values for the remaining bony structure. DEXA results confirmed the initial adequacy of our grafting techniques. Serial scans showed the response of the grafts to both revascularisation and loading. Increases in high-load areas were higher than in low-load areas, reflecting the response of live bone to in vivo stresses. There were also changes reflecting the ongoing revascularisation of the grafts. These findings were born out by radiographs. DEXA is useful in assessing the incorporation and biological responses of large allografts in revision arthroplasty