Background. The anatomy of the human knee is very different than the tibiofemoral surface geometry of most modern total knee replacements (TKRs). Many TKRs are designed with simplified articulating surfaces that are mediolaterally symmetrical, resulting in non-natural patterns of motion of the knee joint [1]. Recent orthopaedic trends portray a shift away from basic tibiofemoral geometry towards designs which better replicate natural knee kinematics by adding constraint to the medial condyle and decreasing constraint on the lateral condyle [2]. A recent design concept has paired this theory with the concept of guided kinematic motion throughout the flexion range [3]. The purpose of this study was to validate the kinematic pattern of motion of the surface-guided knee concept through in vitro, mechanical testing. Methods. Prototypes of the surface-guided knee implant were manufactured using cobalt chromium alloy (femoral component) and ultra-high molecular weight polyethylene (tibial component). The prototypes were installed in a force-controlled knee wear simulator (AMTI, Watertown, MA) to assess kinematic behavior of the tibiofemoral articulation (Figure 1). Axial joint load and knee flexion experienced during lunging and squatting exercises were extracted from literature and used as the primary inputs for the test. Anteroposterior and internal-external rotation of the implant components were left unconstrained so as to be passively driven by the tibiofemoral surface geometry. One hundred cycles of each exercise were performed on the simulator at 0.33 Hz using diluted bovine calf serum as the articular surface lubricant. Component motion and reaction force outputs were collected from the knee simulator and compared against the kinematic targets of the design in order to validate the surface-guided knee concept. Results. Under deep flexion conditions of up to 140° of squatting the surface-guided knee implants were found to undergo a maximum of 22.2° of tibial internal rotation and 20.4 mm of posterior rollback on the lateral condyle. Pivoting of the knee joint was centered about the highly congruent medial condyle which experienced only 1.6 mm of posterior rollback. Experimental results were within 2° (internal-external rotation) and 1 mm (anteroposterior translation) agreement with the design target throughout the applied exercises (Figure 2). Conclusion. The results of this test confirm that by combining a constrained medial condyle with guiding geometry on the lateral condyle, deep knee flexion activities of up to 140° can be performed while maintaining near-natural kinematics of the knee joint. The authors believe that the tested surface-guided implant concept is a significant step toward the development of novel TKR which allows a greater range of motion and could improve the quality of life for active patients undergoing knee replacement. For any figures or tables, please contact the authors directly

Introduction. The regionalisation of major trauma in the UK has significantly improved outcomes for patients with severe, lower limb injuries. Chronic pain after complex lower limb injuries is well documented, but seems to remain a problem despite better clinical and radiological outcomes. We hypothesised that pain was mediated through the saphenous nerve, especially as most tibial injuries affected the soft tissues medially. As a proof of concept, we undertook adductor canal blocks to understand pain aetiology. Materials & Methods. Patients with chronic pain following complex lower limb trauma or congenital deformity correction have been selected and underwent an adductor canal block by one of our trauma anaesthetist that specialises in this procedure. Their outcomes were recorded in their clinical records and patients were contacted by phone to document their experiences. Results. 14 patients with chronic, treatment refractory lower limb pain who were being managed in our orthoplastics clinic following complex, lower limb trauma were identified. Six of those patients had required plastic coverage. Of these 14 patients, all stated their pain completely resolved after the procedure and then returned between 24 hours and 4 weeks after the procedure. Two patients underwent a saphenous nerve diversion after conduction of the blocks, reporting subsequent resolution of their complaints. Conclusions. As a proof of concept, we report that the saphenous nerve underlies chronic pain in patients with complex lower limb injuries. An adductor canal block is an effective diagnostic tool for these patients. Saphenous diversion may offer a permanent solution in patients who respond well to saphenous nerve block. A prospective study is planned to objectively measure pain and quality of life scores after treatment of complex injuries and pre and post adductor canal block

Aim. Reconstruction of composite soft-tissue defects with extensor apparatus deficiency in patients with periprosthetic joint infection (PJI) of the knee is challenging. We present a single-centre multidisciplinary orthoplastic treatment concept based on a retrospective outcome analysis over 20 years. Method. One-hundred sixty-seven patients had PJI after total knee arthroplasty. Plastic surgical reconstruction of a concomitant perigenicular soft-tissue defect was indicated in 49 patients. Of these, seven presented with extensor apparatus deficiency. Results. One patient underwent primary arthrodesis and six patients underwent autologous reconstruction of the extensor apparatus. The principle to reconstruct missing tissue ‘like with like’ was thereby favoured: Two patients with a wide soft-tissue defect received a free anterolateral thigh flap with fascia lata; one patient with a smaller soft-tissue defect received a free sensate, extended lateral arm flap with triceps tendon; and three patients received a pedicled medial sural artery perforator gastrocnemius flap, of which one with Achilles tendon. Despite good functional results 1 year later, long-term follow-up revealed that two patients had to undergo knee arthrodesis because of recurrent infection and one patient was lost to follow-up. In parts, results have been published under doi: 10.7150/jbji.47018. Conclusions. A treatment concept and its rationale, based on a single-centre experience, is presented. It differentiates between various types of soft-tissue defects and shows reconstructive options following the concept to reconstruct ‘like with like’. Despite good results 1 year postoperatively, PJI of the knee with extensor apparatus deficiency remains a dreaded combination with a poor long-term outcome

Aim. To provide proof of concept in an in vivo animal model for the prevention of prosthetic joint infection prevention using electric fields along with conventional antibiotic prophylaxis. Corresponding Author: Marti Bernaus. Method. First, we standardized the animal model to simulate implant contamination during the surgical procedure. We then implanted cobalt-chrome prostheses adapted to both knees of two New Zealand White rabbits, under standard aseptic measures and antibiotic prophylaxis with cefazolin. Prior to implantation, we immersed the prostheses in a 0.3 McFarland inoculum of S. aureus (ATCC 25923) for 30 seconds. In the first animal (control), the joint was directly closed after washing with saline. In the second animal (case), both prostheses were treated with electric current pulses for 30 seconds, washed with saline, and the joint was closed. After 72 hours, both animals were reoperated for the collection of periprosthetic tissue and bone samples, and prosthesis removal. In all samples, we performed quantitative cultures prior to vortexing and sonication, as well as prolonged cultures of the sonication broth. We confirmed the absence of contamination by identification with MALDI-TOF (VITEK-MS) and automated antibiotic susceptibility testing of the isolated colonies (VITEK-2). Results. In the “control” animal, we isolated S. aureus in all studied samples. The bacterial count expressed as log10 (cfu/cm2) in the prostheses of the right and left legs was 9.38 and 8.86, respectively. The bacterial count expressed as log10 (cfu/mL) in bone and periprosthetic tissue biopsies was 2.70 and 2.72 in the right leg and 3.24 and 3.87 in the left leg, respectively. In the “case” animal, where an electric field was applied to the implant after placement in addition to cefazolin prophylaxis, all samples (prosthesis, bone, and periprosthetic tissue) were negative, and no isolation of the inoculated strain of S. aureus was obtained after incubation of the sonication broth for 14 days. Conclusions. This in vivo model suggests the potential effectiveness of applying an electric field to a prosthetic implant in combination with cefazolin for the prevention of PJI development, after exposure of the implant to an inoculum of S. aureus (ATCC 25923). Our findings need to be confirmed using a larger sample size

Culture of multiple intraoperative tissue samples is the standard of microbiological diagnosis of prosthetic joint infections. Recently, improved sensitivity of using prosthesis sonication method and molecular techniques has been reported in the literature. However, collecting the removed prosthesis as well as additional specimens for molecular analysis is not straightforward for the surgeons and assistants in the operation theatre. Our All-in-a-Box concept addresses the need for simple and unambiguous sampling of clinical specimens in the operating theatre, and to overcome the variation in sampling technique within and between surgical teams and across different hospitals. The All-in-a-Box concept was developed in close cooperation between surgeons, their operating assistants, clinical microbiologists and molecular biologists in order to ensure the concept is easily implemented in the operating theatre, achieving high completeness, and being well preserved all the way to the laboratory. All needed equipment, vials and forms are collected in a single box, and corresponding items are clearly color coded to further reduce the likelihood of confusion. Boxes are designed to address the specific needs for either routine diagnosis or special demands as in clinical studies. Their design is based on large experience in connection with diagnosis of joint prosthesis-related infections. Downstream SOPs for sample processing are included in the All-in-a-box concept and specimens can subsequently be analyzed in parallel by culturing and molecular methods. We have implemented this concept in two large research projects, we received 1508 (89%) of 1685 scheduled samples during the 2-year project period in the first project despite several different surgical teams and hospitals, while the other project is still ongoing. All-in-a-Box is useful concept to improve the completeness of routine sampling for microbial analysis

Total hip replacement procedures are among the most frequent surgical interventions in all industrialized countries. Although it is a routine operationliterature reports that important parameters regarding for example cup orientation and leg length discrepancy often turn out to be not satisfying after surgery. This paper presents a novel concept to improve the reproducibility and accuracy for implantation of cup and stem prosthesis at exactly the desired locations. Existing computer- based commercial products either offer software solutions for just pre-operative planning, or imageless navigation systems that are only used during surgery in the operating theatre. The innovation of our approach is based on an integrated computer-assisted solution that combines pre-operative planning and intra-operative navigation to support THR procedures. The software for pre-operative planning can process both, 3D CT images and standard 2D x-ray images. A custom-built navigation system using optical 3D localizing technology has been developed to transfer planning results to the OR. The main objective of our approach is to implant the artificial joint in a way to restore the natural anatomy of the joint before surgery as close as possible, or with exactly planned modifications. In particular, cup inclination, cumulative anteversion of cup and stem, CCD angle and lateral offset, centre of rotation, leg length discrepancy, and joint range of motion are considered. It is not necessary to determine numerical values for all of these parameters because our approach uses a unique procedure to record the natural anatomical situation by combining pre-operative planning and intra-operative navigation, and subsequently supports implantation of the prosthesis components by surgical navigation in order to restore this situation. In case planar 2D x-ray images are used for pre-operative planning accurate scaling of these images is a prerequisite for exact determination of relevant parameters. The patient-specific scaling factor depends on the distance of the hip joint rotation centre from the x-ray detector or film. We have designed a low-cost localization system to be mounted close to the x-ray apparatus. It localizes the 3D position of the rotation centre by small motions of the leg and eliminates uncertainties of conventional methods that are caused by improper positioning of a calibration body. Easy and robust setup and application have been key objectives for the development of our custom-built navigation system. Acquisition of intraoperative parameters for example includes the determination of the acetabular centre axis by localizing selected landmarks at the acetabular rim. Intra-operative parameters are combined with pre-operative parameters without needing sophisticated matching procedures with the pre-operative images. A preliminary surgical workflow that will be detailed in the conference presentation has been designed for evaluation of the concept using sawbones models. Based on the promising results of our laboratory tests we have started to prepare first clinical experiments in close cooperation with surgeons

Objective. To investigate the effectiveness of applying fast track surgery concept in primary total hip arthroplasty. Methods. The data of patients with primary total hip arthroplasty in our department from January 1, 2013 to October 1, 2015 were retrospectively analyzed. The patients were divided into traditional recovery group, enhanced recoverygroup and update enhanced recovery group according to different interventions. The blood loss, transfusion rate, complications rate, postoperative function, length of stay, hospitalization expense and readmission rate were compared between three groups. Results. A total of 435 cases were included. Compared with traditional recovery group, the average blood loss, length of stay and total cases of complication in update enhanced recovery group were reduced 91.44 ml, 1.34 days and 14.05%, respectively, and the differences showed statistical significance. From 2013 to 2015 the hip flexion and abduction degree increased annually, the differences also showed statistical significance. The blood transfusion rate, other complications and hospitalization expense were all reduced, but there were no statistical significance. Conclusions. The emphasis of fast track surgery concept in primary total hip arthroplasty was the management in perioperative period. Through continuous optimization of intervention measures under the guidance of evidence based medicine, it can effectively accelerate recovery, diminish complications and reduce the length of hospital stay

Introduction. An increasing trend in the incidence of primary and revision bone replacements has been observed throughout the last decades, mainly among patients under 65 years old.10-year revision rates are estimated in the 5–20% range, mainly due to peri-implant bone loss. Recent advances allow the design of implants with custom-made geometries, nanometer-scale textured surfaces and multi-material structures. Technology also includes (bio)chemical modifications of the implants' surfaces. However, these approaches present significant drawbacks, as their therapeutic actuations are unable to: (1) perform long-term release of bioactive substances, namely after surgery; (2) deliver personalized stimuli to target bone regions and according to bone-implant integration states. The Innovative Concept. Here we propose the design of instrumented active implants with ability to deliver personalized biophysical stimuli, controlled by clinicians, to target regions in the bone-implant interface throughout the patients' lifetime. The idea is to design bone implants embedding actuators, osseointegration sensors, wireless communication and self-powering systems. This work proposes an advanced therapeutic actuator for personalized bone stimulation, and a self-powering system to electrically supply these advanced implants. Novel Capacitive Stimulators and Self-Powering Systems. A novel circular capacitive stimulator was designed for personalized stimulatory therapies based on the delivery of electric fields to bone cells. Its architecture is composed by 3 coplanar electrodes, 2 mm wide, 1 mm thick, and 0.5 mm apart from each other. It enables the delivery of controllable stimuli, as different stimuli (varying waveform, strength, frequency, etc.) can be delivered to target regions of bone. Numerical biophysical models were developed using COMSOL Multiphysics (v. 5.2) to analyze the osteogenic effects of stimulation delivered in vitro to MC3T3-E1 bone cells. 8 domains (electrodes, petri dish, substrate, air, cellular medium and physiological medium) were considered to simulate an apparatus to stimulate cell cultures. Simulations were carried out by applying low and high frequency (14 Hz and 60 kHz) sinusoidal excitations with 10 V of amplitude. A motion-driven and maintenance-free self-powering system was designed using magnetic levitation-based electromagnetic energy harvesting. A semi-analytical non-linear mathematical model of its complex energy transduction was developed (it includes modelling of the magnetic field produced by levitating hard magnetic elements, repulsive force between two magnets, electrical and mechanical damping, induced voltage, mechanical and electric dynamics) to estimate the energy harvested during gait patterns. Results. This cosurface stimulator is able to deliver similar magnitude stimuli to bone cells as those already recognized as osteogenic by previous studies. Heterogeneous stimuli is delivered both for low and high excitations, although quite different stimuli distributions are found along the cellular layer. Maximum stimuli occur over the electrode-anode region and its magnitude is approximately 0.3 V/mm. The electrode thickness influence must also be highlighted: the use of electrodes with 0.1 mm thick result in 2.5-fold magnitude increases in high-frequency stimulation. Excellent agreement was obtained between simulations and experiments with mean energy errors around 6% and cross-correlations higher than 85%. These results indicate that the design of this self-powering system can be optimized prior to fabrication and according to gait patterns of patients

Background. The management of non-unions of subtrochanteric femoral fractures with associated implant failure is challenging. This study assessed the outcome of a cohort of patients treated according to the diamond concept. Methods. Between 2005–2010 all patients with subtrochanteric aseptic non-unions presented post implant failure (Gamma Nail breakage) were eligible in the absence of severe systemic pathologies and comorbidities. Demographics, initial fracture pattern, method of stabilisation, mode of failure of metal work, time to revision of fixation, complications, time to union, and functional outcome were recorded over a minimum period of follow-up of 12 months. The revision strategy was based on the “diamond concept;” optimising the mechanical and biological environment (revision of fixation, osteoinduction/BMP-7, osteoconduction/RIA harvested graft, and osteogenicity/concentrate of bone marrow aspirate). Results. Out of 280 nailing procedures 12 (4.3%) cases met the inclusion criteria. A consistent mode of metalwork failure was recorded with initial breakage of the proximal distal locking screw followed by nail breakage at the lag screw level. Biomechanical SEM analysis of the nails revealed no structural damage besides the standard fatigue striation. Varus mal-reduction was present in all cases, with an average of 7.3 degrees (5–11). The average time to screw failure was 4.3 months (2–6) and nail failure was 5.9 months (4–10). All but one of the cases were revised to a 95 degrees blade plate and one to an Affixus nail. Time to union was 6.5 months (5–10). All but one of the cases by 12 months have returned to their preinjury level of mobilisation. Conclusion. Varus mal-reduction must be avoided in the initial stabilisation of subtrochanteric fractures. Proximal distal screw failure is predictive of future fracture non-union and subsequent nail breakage. The diamond concept for optimising mechanics and bone biology is a successful method for managing complex sub-trochanteric non-unions with failed metalwork

Introduction. The orthopaedic market offers more than two hundred different hip femoral stems. Of these, very few have undergone scientific studies with published results. The differences of designs of the stem are mainly related to surface texture and geometry sections. The development of a new cemented hip prosthesis is certainly a very hard task if aiming the improvement of actual performance. Materials and Methods. This study presents the influence of geometric variables in a novel hip stem concept which was based on the comparison of the performance of the best cemented stems actually in the market. The study was developed using finite element analysis and experiments with in vitro femoral replacements. A numerical simplified model of the hip replacement was designed to generate the final geometry of the femoral stem section. After an in vitro cemented commercial stem was done, with the best cemented stem a Lubinus, Charnley, Stanmore and Müller. Realistic numerical models also allowed us to determine cement mantle stresses of commercial femoral stems that were compared with those obtained for the new concept stem. The new model was then prototyped and tested through in vitro fatigue tests. Finally fatigue tests were also performed to determine the density of cracks in the cement mantles, as well as debonding for both conventional and new designs. Results. Stem section geometry influences the fatigue mechanism at the stem–cement interface and is an important factor in the load transfer. The organic section presents 60% (average) less cement stress than sharp sections. Concerning the new stem, detail design geometry parameters were analyzed, such as collar position and orientation, medial radius and geometry of the stem tip. The simulations performed show that the new stem design presents 98.5% of cement volume under an equivalent stress lower than 3 MPa [FIG 1]. The correlation factor between this percentage with the clinical follow up results for 10 years of commercial stems is 0.964, being p=0.641 the significance level of one tailed Person correlation. Discussion. The variables associated to the stem geometry presents influence in the cement mantle stress and could improve the success. The section of stem is an important factor to improve the load transfer. The [FIG. 2] presents a resume of some variables in a new concept. The inclination of collar 5° at sagital plane reduces the stress in 10% proximally. The tip geometry influences the stress in cement and improves the femoral position. The tip geometry could reduce 20% of cement stress in distal region. Conclusions. The new femoral design was based on the findings of the finite element analysis and fatigue tests. It presents an innovative collar, “organic” geometry sections and a geometry tip that minimizes stress concentration. The stem developed reduces the cement stresses in an average of 25% relatively to the commercial stems used in the study. The work demonstrates in a new hip concept that small details in design of cemented hip may have consequences in the implant success

Aim. The purpose of this single center study was to analyze the robustness and thoroughness of debridement and irrigation in first stage procedures for periprosthetic joint infections in which the latter had been confirmed by fulfilling the PJI criteria produced by the musculoskeletal infection society. Method. After introduction of ‘a clean phase’ concept in our center, we developed a method of using new instrumentation sets and waterproof cover sheets as well as sets of gloves and aprons after thorough debridement followed by copious irrigation under a splash sheet, once the prosthetic components were removed during which several (6 to 8) tissue biopsies and cultures were harvested. ‘Clean phase’ tissue specimens ad random were again obtained and cultured and compared with ‘dirty phase’ cultures and sonication results. Our zero hypothesis was that we were not able to entirely eradicate bacterial colonization. We tested this hypothesis during a period of 18 months in a consecutive series of first stage revisions for PJI at our center after introduction of the clean phase concept. Results. We were able to reject our zero hypothesis in that ‘clean phase’ tissue cultures were either negative or that they did not match ‘dirty phase’ tissue cultures suggestive of bacterial contamination. Descriptive statistical analysis was utilized. Conclusion. Our findings suggest that our procedures and methods of debridement and irrigation in first stage PJI revision procedures are robust and thorough. Further investigation is required to determine whether ‘clean phase’ culture negativity is matching with a successful outcome in the run up and after the second stage revision procedure

INTRODUCTION

Simulation plays an important role in surgical education and the ability to perfect surgical performance. Simulation can be enhanced by adding various layers of realism to the experience. Haptic feedback enhances the simulation experience by providing tactile responses and virtual reality imagery provides an immersive experience and allows for greater appreciation of three-dimensional structures. In this study, we present a proof-of-concept haptic simulator to replicate key steps of a cervical laminoplasty procedure. The technology uses affordable components and is easily modifiable so that it can be used from novice through to expert level. Custom models can be easily added ensuring the simulator can be used in a wide range of orthopaedic applications from baseline education through to day of surgery pre-operative simulation.

Aim. Data of optimal management of infections after internal fixation (IIF) is scarce and long-term follow-up results often lack. We analyzed characteristics of infections after intramedullary (IIIF) and extramedullary long bone fixation (IEIF) and evaluated their infection and functional outcome. Method. Consecutive patients with IIF diagnosed at our institution from 01/2010-10/2017 were retrospectively included. Infection was defined as visible purulence, sinus tract, microbial growth in ≥2 independent samples or positive histopathology. The outcome was compared before and after implementation of a comprehensive surgical and antimicrobial treatment algorithm in 04/2013. Results. Of 127 patients, infection involved lower extremity in 111 patients (87%). Median age was 53 years (range, 19–89 years), 70% were men. Fixation was performed with intramedullary nail in 47 (37%) and with extramedullary osteosynthesis (plates, screws, pins) in 80 patients (63%). At infection diagnosis, the implant was in situ in 96 patients (76%), whereas 31 patients (24%) had residual osteomyelitis after implant removal. The time from bone fixation to infection was longer in IIIF than IEIF (25 vs. 7 months, p=0.027). Pain was reported in 55 patients (43%) and local infection signs in 96 patients (75%), including sinus tract in 46 patients, more commonly reported after IIIF than IEIF (49% vs. 29%, p=0.035). Infections were monomicrobial in 85 (67%), polymicrobial in 18 (14%) and culture-negative in 23 patients (18%). Most common pathogens were S. aureus (43%), coagulase-negative staphylococci (28%) and gram-negative rods (22%). Débridement (with device retention, if present) was performed in 40, device removal in 43, one-stage exchange in 16 and two-stage exchange in 20 patients. One patient had no surgery and 7 patients underwent limb amputation. 43 patients (34%) were treated before implementation of the interdisciplinary treatment concept and 84 patients (66%) afterwards. Among 111 patients with available follow-up (median, 5.2 months; range, 0.2–86 months), in 78 cases (70%) infection eradication was achieved (similar in IIIF and IEIF). However, overall infection and functional outcome was only 48% (53 patients). After implementation of the treatment algorithm, the infection outcome improved from 56% to 79% (p=0.03) and the overall success from 33% to 56% (p=0.016). Conclusions. Approximately half of infections after IIF failed in terms of infection eradication or restoration of function. After implementation of standardized surgical and antibiotic treatment concept, infection and functional outcome improved significantly. No significant differences between IIIF and IEIF was observed in terms of infection and functional success

We introduce a novel active tensioning system that can be used for dynamic gap-based implant planning as well as for assessment of final soft tissue balance during implant trialing. We report on the concept development and preliminary findings observed during early feasibility testing in cadavers with two prototype systems. System description. The active spacer (fig 1) consists of a motorized actuator unit with integrated force sensors, independently actuated medial and lateral upper arms, and a set of modular attachments for replicating the range of tibial baseplate and insert trial sizes. The spacer can be controlled in either force or position (gap) control and is integrated into the OMNIBotics. TM. Robotic-assisted TKA platform (OMNI, MA, USA). Cadaver Study. Two design iterations were evaluated on eleven cadaver specimens by seven orthopaedic surgeons in three separate cadaver labs. The active spacer was used in a tibial-first technique to apply loads and measure gaps prior to and after femoral resections. To determine the range of forces applied on the spacer during a varus/valgus assessment procedure, each surgeon performed a varus/valgus stress test and peak medial and lateral forces were measured. Surgeons also rated the feel of the stability of the knee at 50N and 80N of preload using the following scale: 1 – too loose; 2 – slightly loose; 3 – ideal; 4 slightly tight; 5 – too tight. Final balanced was assessed with the spacer and with manual trial components. Results. Overall the prototype system successfully met the functional requirements for applying controlled tension during ligament balancing, and user feedback on usability and feasibility for use in TKA was highly positive. Peak forces measured during blinded stability assessments were significantly imbalanced from medial to lateral and exhibited a wide range across users (range: 70N – 310N, table 1). Each surgeon rated 50N of tension as feeling “slightly loose” and 80N as feeling “ideal” in extension. “Ideal” soft tissue balance was achieved in the last three knees tested using the second design iteration, as rated by the surgeons with final trial components in place. Discussion. Our preliminary cadaver results have established the initial feasibility of the active spacer concept for applying tension during ligament balancing and implant planning. Our initial results also suggest that performing a varus/valgus assessment without force readings can lead to imbalanced mediolateral load application. This may be due to factors such as hand dominance and pulling in varus versus pushing in valgus. There was also considerable inter-surgeon variability in the peak forces applied. An advantage of computer-controlled ligament tensioning and force sensing is ability to standardize applied mediolateral forces across patients and surgeons. In the assessment of the ‘ideal' static ligament tension in extension a force of 80N was preferred over 50N, which is in the range of forces applied by others during ligament balancing. What is the ideal patient specific force to apply remains a topic of future research. Our next steps will be to further evaluate use of the system in the context of virtual trialing

Introduction. Functional stability is a new concept stating that lower tensions than expected are enough to achieve joint stability leading to proper function after TKA. To check this rationale clinically, a new electronic device (DLB bicon sensorplate) was used intraoperatively to measure ligament tension and allow the surgeon to proper balance the knee after TKA insertion. In this study a controlled clinical analysis at 1 YR follow-up is reported. Methods. A cohort of 25 patients was treated in a single centre, single surgeon study to quantify the influence of the use of this electronic device in the short- and midterm results (DLB Group). A control cohort of 25 patients were treated without the device (Control Group). All patients were monitored by the use of OKS, AKSS and FJS; beside that, the muscle function before and after the surgery was tested and a load distribution analysis was performed. The FU examinations were done after 6 weeks, 3 months, 6 months and 1 yr. All the patients finished the study and could be included. Results. DLB group showed an improvement of 10% in the OKS compared to the Control Group, even if the preoperative measurements were lower (OKS DLB Group improve from 18 to 44, Control group from 26 to 40). Also the AKSS shows an improvement around 10% in the DLB Group (38 to 97) compared to the Control Group (53 to 93); the knee score improved also in the same matter (DLB Group 32 to 91, Control Group 40 to 91). Similar improvement in the FJS was also found in the DLB Group and in the Control Group. The muscles function testing showed a faster recovery of the muscle status and restore of the original functionality in the DLB Group. DLB Group patients recovered approx. 1/3 of the time faster than Control Group ones. The load distribution analysis shows a better load distribution with a more normal gait in the DLB Group. Summary. In all PROMs the group treated by the support of the device showed a significant improvement and better clinical outcome, also the subjective patient satisfaction was higher in the DLB Group, where the proper ligament tension (aimed to functional stability) was achieved. Conclusion. The use of sensory devices to secure proper balancing is justified by several studies. This study proves the efficacy of using a sensory device intraoperatively to measure the necessary ligament tension to achieve functional stability in a controlled single centre study

Abstract

INTRODUCTION. Since over 40 years, ceramics are known for their excellent biocompatibility, extremely low wear rates and excellent wettability. This would make a ceramic-on-Polyethylene bearing also a beneficial combination for a knee implant if potential strength issues could be overcome. METHODS. A mechanical proof-test for a ceramic femoral knee implant component was developed by subsequent steps of numerical load/stress analysis and design of adequate mechanical test equipment. The procedure was organized as follows: . 1. Analysis of maximum in-vivo loading condition and distinguish between alternating regular loading with a high cycle number during life time and irregular worst case loading. The relevant regular loading is represented by rising from a chair and normal walking. The most critical irregular worst cases are stumbling or impact loading. The load transfer, stress distribution and the anticipated cycle number during life-time are distinguished and taken into account for the development of the test concept. 2. Analysis of the “boundary conditions,” i.e. the fixation of the ceramic prosthesis on the bone identifying the worst-case conditions. 3. Finite Element analysis: Identifying regions of highest stress concentration at variable external loading. 4. Design analysis and accommodation if necessary. From step 3 it is evident that stress concentration is mainly generated by geometric features, e.g. the shape of the corners at the interface to the cement. Significant reduction of stress concentration was achieved by some minor corrections of design details. . 1. Development of an adequate mechanical test equipment which produces stresses comparable to the in-vivo conditions and performing of mechanical tests with ceramic femoral components. 2. Validation of the test concept: comparison of test results and stress analysis. 3. Assign “safety margin,” i.e. required overload tolerance of the ceramic component with respect to worst case load in-vivo. 4. Establish “proof test,” i.e. in-production mechanical testing of each individual component in order to provide safety margin. RESULTS. An in-vivo load scenario has been determined for a ceramic femoral component using a regular and a tension test for the femoral components. In the regular test, the mechanical strength of the polished outer condyles is tested using a force which is equivalent to an in-vivo loading of 16 times bodyweight. In the tension test, the interior sides of the condyles are stressed in the sagittal plane ensuring a mechanically reliable implantation. This test is performed with a force equivalent to 10 times bodyweight. The verification of the numerical calculations of the experimental test setup was done using strain gauges. It has been shown that the mechanical tests exactly produce the intended stress distribution for the femoral ceramic knee component. Using these new and validated test methods ceramic femoral components are safe for clinical use. DISCUSSION. The procedure to determine proof loads using the maximum in-vivo loads together with a safety factor ensures the mechanical safety of a ceramic knee component. Together with its excellent tribological and biological behaviour of ceramics, this application provides an alternative to standard metallic knee components

INTRODUCTION. Soft tissue balancing in knee arthroplasty remains an art. To make it a science reliable quantification and reference values for soft tissue tension and contact loads are necessary. This study intends to prove the concept of a compartmental load safe target zone as a clinical tool for balancing total knee arthroplasties by studying the relationship between post- balancing compartmental load distribution and patient satisfaction at 6 months. MATERIALS AND METHODS. In this prospective non-randomised clinical series of 102 patients (110 knees), medial and lateral loads were recorded intra-operatively using a tibial liner load sensor system. All knees were balanced using specific algorithm sequences with a goal of equal distribution between compartments. A safe target zone area was defined on a scatterplot graph displaying lateral versus medial loads. Individual points on the graft were coded with their satisfaction score at 6 months. RESULTS. Eighty-two (82) cases satisfied the study criteria and were analysed. The boundaries of the safe zone were defined by combining absolute and relative load values. Fifty-seven (57) knees fitted in the defined zone and 25 lied outside. Excellent satisfaction scores were 4.2 times more likely to be in the safe zone. Poor scores were twice more likely to lie outside the zone. In the zone the median satisfaction score was 36/40, whereas outside the zone it fell to 31/40. DISCUSSION. Load balancing of knee arthroplasty is a useful clinical tool. Early studies by a developing group showed increased satisfaction rates. One problem remains the subjectivity of testing at the time of surgery. Other studies have also pointed to the difficulty in defining a target zone for balancing. Using specific ligamentous balance algorithms it is now possible to predictably achieve a balanced load differential within 15 lbs between compartments. In this paper, we have demonstrated in a prospective series that a target zone can be defined as an area rather than a single ideal value. Within this zone satisfaction scores reach 90–95%. Of all excellent results there are 4.2 more within the zone than outside. Balancing a knee arthroplasty to medial and lateral compartment load values defined by a safe target zone can therefore be predictive of patient satisfaction

Aim. Spinal infections with and without aSCI represent a severe disease with a high lethality rate of up to 17%. The current treatment recommendations include an antimicrobial therapy and if necessary in combination with operative procedures. Aims of this study are the analysis of risk factors and treatment concepts and to compare the outcome of patients suffering a spinal infection with and without an aSCI. Method. Monocentric prospective case study from 2013 – 2015. Patients were examined using a diagnostic algorithm (CT-thorax/abdomen, MRI total-spine, blood cultures, dental chart, echocardiogram). A calculated antimicrobial therapy was initially administered and later changed according to the antibiotic resistance. Additional operative procedures were performed with respect to the clinical and radiological findings. Results. 68 patients (age 69.8 ± 13.7 years) were included. A Charlson-Comorbidity-Index of 3.9 ± 2.5 was calculated. An spinal infection with aSCI was associated with a significantly higher number of infected spinal segments (p=0.013). A longer duration of antibiotic treatment (statistically non-significant) and a higher operation rate was shown with aSCI. Also the inpatient and intensive-care unit treatment duration was significantly longer with aSCI. The number of treatment-associated complications and the lethality were equal in both groups. The age (odds-ratio 1.1 per one year increase; p=0.02) and the appearance of an epidural empyema (odds-ratio 7.9; p=0.04) have been identified as independent lethality factors. Conclusions. Patients with spinal infections are multimorbid and have multiple infectious origins, which warrant further diagnostic investigations. Treatment associated complications, lethality rates and clinical outcome of spinal infection with and without aSCI are comparable in a specialized unit. Lethality risk factors are age and presence of an epidural empyema. In subsequent studies the antibiotic treatment duration and the long-term follow up will be evaluated

Background. Performing total knee replacement needs both bony & soft tissue consideration. Late John Insall advocating spacer blocks with concept of balanced & equal flexion – extension Gap. Although we usually excise both ACL & PCL, still it is possible to retain more soft tissue. Both PCL retaining & sacrificing Require intact collaterals for stability. Superficial MCL & LCL should be preserved, if possible. After PCL removal the following advantages could obtain: More correction of fixed varus or valgus deformity, More surgical exposure. but there are no proved disadvantages like; increasing in stress & loosening of bone-cement-prosthesis interface, specific clinical difference in ROM, forward lean during stepping up, proprioception inferiority. In other hand over tight PCL cause excessive rollback of tibia & knee hinges open, preventing flexion (booking), and Severe posteromedial poly wear in poor balance PCL might be happened. Mid range laxity when Post. Capsule is tight, even with correct tensioning in full extension & 90 degree flexion, may occur (and secondary collateral ligaments imbalance throughout ROM). There is a major effect of capsular contracture in coronal mal alignment with flexion contracture. Full MCL releases not only correct fixed varus but also open the medial space in flexion. MCL & post. Capsule has combined valgus resistant effect in extension. PCL release increase flexion gap more, May be necessary to release something that affect extension gap as compensated balancing (Post.medial capsule). Any flexion contracture need to posterior capsulotomy & post. Condyle osteophyte removal before femoral recut. So it is possible to perform posteromedial capsulotomy prior to superficial MCL release. Method. From May 2009 to June 2013, 219 TKA (165 patient) (bilateral in 54 patients, simultaneous bilateral in 5 patients) with primary DJD and varus deformity of knees were operated by myself with joint replacement. Most patients had some degree of varus correction in flexion, passively. The varus angle was less than 25*, means mild to severe but not decompensate. 46 patients had some degree of patella baja. For soft tissue balancing during Total knee arthroplasty I consider the following steps; Medial capsule & deep MCL release, PCL release, Posteromedial capsulotomy, semimembranous release, Superficial MCL release, Pes anserinous release. Post.medial capsulotomy was done in all cases. The Average Age was 65.47 years, 131 patients (177 knees) were female (79.3%) and five of them had bilateral TKA simultaneously. Lt Knee was operated in 94 cases (42.9% of 219). Spinal anesthesia was applied in 54.3% (119 patients) & epidural anesthesisa in 5 % (13 cases). 14 knees were operated with MIS technique and 205 knees with Standard medial parapatellar incision. Semi membranous release was necessary in 72 knees (33 pure=15%, without S.MCL release). S.MCL release was mandatory in 39 (17.8 %) knees for checking balanced medial and lateral subtle laxity (playing), I have used simple blade with 1 & 2 mm thickness in each ends for younger patients, and the other one with 3&4 mm thickness in elder cases. Results. Average follow up period is 2.07 years. Average Operating time was 1: 38 (h: m). Average Transfusion = 1.29 unit packed cell. Average varus malalignment=14.76*(2–25*) / Av. Valgus angle= 7.11* (5–10 *) / Av. DLFA= 91.15* (85–102*) / Av. PMTA = 82.04* (68.5–90*) / Av. Ext. rotation cut = 5.7* (0–9). Stage l + PCL + Post. Med. Capsular release was performed in all. pure stage l + P.M.capsular release in147 cases(67.2%), plus semimembrnous release in33 cases(15%), S.MCL release in 39cases(17.8%)/ Av. Post op alignment:1.01 * varus(0 −6 *) (worse in medial pivot knee). so S.MCL release was preventedin 82.1% of cases. Av. Polyethylen size: 12.26 (9 in oxynium −19 in plus) / Semi membranous release was necessary in 72(32.8%) cases (preop varus 17.57*). / S.MCL release was mandatory in 39(17.8 %) cases (preop varus 17.6 * & No Flexibility in 30* flexion). pre operation knee society score: stage I = 26.6, stage II = 38.7 increase to stage I = 86.45, stage II = 77.63. Conclusion. In society with more kneeling habitués, during performing total knee arthroplasty with less than 25* degree varus malalignment plus some degree flexibility of the deformity in flexion, it is wise to consider posteromedial capsular release prior to semi membranous & S.MCL release to obtain full correction of alignment. But the most important thing is reaching to more align limb without instability, regardless of various technique