Background. Artificial total knee designs have revolutionized over time, yet 20% of the population still report dissatisfaction. The standard implants fail to replicate native knee kinematic functionality due to mismatch of condylar surfaces and non-anatomically placed implantation. (Daggett et al 2016; Saigo et al 2017). It is essential that the implant surface matches the native knee to prevent Instability and soft tissue impingement. Our goal is to use computational modeling to determine the ideal shapes and orientations of anatomically-shaped components and test the accuracy of fit of component surfaces. Methods. One hundred MRI scans of knees with early osteoarthritis were obtained from the NIH Osteoarthritis Initiative, converted into 3D meshes, and aligned via an anatomic coordinate system algorithm. Geomagic Design X software was used to determine the average anterior-posterior (AP) length. Each knee was then scaled in three dimensions to match the average AP length. Geomagic's least-squares algorithm was used to create an average surface model. This method was validated by generating a statistical shaped model using principal component analysis (PCA) to compare to the least square's method. The averaged knee surface was used to design component system sizing schemes of 1, 3, 5, and 7 (fig 1). A further fifty arthritic knees were modeled to test the accuracy of fit for all component sizing schemes. Standard deviation maps were created using Geomagic to analyze the error of fit of the implant surface compared to the native femur surface. Results. The average shape model derived from Principal Component Analysis had a discrepancy of 0.01mm and a standard deviation of 0.05mm when compared to Geomagic least squares. The bearing surfaces showed a very close fit within both models with minimal errors at the sides of the epicondylar line (fig 2). The surface components were lined up posteriorly and distally on the 50 femurs. Statistical Analysis of the mesh deviation maps between the femoral condylar surface and the components showed a decrease in deviation with a larger number of sizes reducing from 1.5 mm for a 1-size system to 0.88 mm for a 7-size system (table 1). The femoral components of a 5 or 7-size system showed the best fit less than 1mm. The main mismatch was on the superior patella flange, with maximum projection or undercut of 2 millimeters. Discussion and Conclusion. The study showed an approach to total knee design and technique for a more accurate reproduction of a normal knee. A 5 to 7 size system was sufficient, but with two widths for each size to avoid overhang. Components based on the average anatomic shapes were an accurate fit on the bearing surfaces, but surgery to 1-millimeter accuracy was needed. The results showed that an accurate match of the femoral bearing surfaces could be achieved to better than 1 millimeter if the component geometry was based on that of the average femur. For any figures or tables, please contact the authors directly

Introduction. Individuals with significant hip and knee trauma receive total knee (TKA) and total hip arthroplasty (THA) as definitive end-stage procedures. In Aotearoa, injury-related costs, including workers compensation, may be funded by ACC. With a steady increase of arthroplasty procedures in Aotearoa, we aim to understand the magnitude and characteristics of such procedures to inform future healthcare strategies. Method. This is a longitudinal collaborative study from 1st January 2000 to 31st December 2020, using ACC and New Zealand Joint Registry databases. Total cost was subcategorised into social and medical cost for analysis. Results. ACC funded 10179 TKA and 5611 THA, amounting to 918 million New Zealand Dollars. Most clients were between 55 and 65 years of age at time of surgery, with greater representation by Male sex and European prioritised ethnicity. Māori and Pacific peoples represent less than 10% of the study population. ACC identified requiring more than 182 days of workers’ compensation as a significant marker for needing additional supports. Risk of this was 21% for TKA and 11% for THA, with risk factors being younger age (RR 0.96), Male sex (TKA RR 1.12, THA RR 1.23), and heavy work-types (TKA RR 1.50, THA RR 1.57). Discussion. Supporting individuals with post-traumatic lower limb arthroplasty is costly. Workers’ compensation contributes to a significant proportion of social expenditure. Risk factors for increased cost utilisation can be used to highlight vulnerable clients and target interventions. Conclusions. This is one of few nationwide studies investigating the healthcare cost of post-traumatic lower limb arthroplasty. We need to focus on injury prevention, targeted treatment, and rehabilitation protocols to improve recovery and reduce time off work. These findings would be of interest to multiple stakeholders

Total knee and hip arthroplasty (TKA and THA) are two of the highest volume and resource intensive surgical procedures. Key drivers of the cost of surgical care are duration of surgery (DOS) and postoperative inpatient length of stay (LOS). The ability to predict TKA and THA DOS and LOS has substantial implications for hospital finances, scheduling and resource allocation. The goal of this study was to predict DOS and LOS for elective unilateral TKAs and THAs using machine learning models (MLMs) constructed on preoperative patient factors using a large North American database. The American College of Surgeons (ACS) National Surgical and Quality Improvement (NSQIP) database was queried for elective unilateral TKA and THA procedures from 2014-2019. The dataset was split into training, validation and testing based on year. Multiple conventional and deep MLMs such as linear, tree-based and multilayer perceptrons (MLPs) were constructed. The models with best performance on the validation set were evaluated on the testing set. Models were evaluated according to 1) mean squared error (MSE), 2) buffer accuracy (the number of times the predicted target was within a predesignated buffer of the actual target), and 3) classification accuracy (the number of times the correct class was predicted by the models). To ensure useful predictions, the results of the models were compared to a mean regressor. A total of 499,432 patients (TKA 302,490; THA 196,942) were included. The MLP models had the best MSEs and accuracy across both TKA and THA patients. During testing, the TKA MSEs for DOS and LOS were 0.893 and 0.688 while the THA MSEs for DOS and LOS were 0.895 and 0.691. The TKA DOS 30-minute buffer accuracy and ≤120 min, >120 min classification accuracy were 78.8% and 88.3%, while the TKA LOS 1-day buffer accuracy and ≤2 days, >2 days classification accuracy were 75.2% and 76.1%. The THA DOS 30-minute buffer accuracy and ≤120 min, >120 min classification accuracy were 81.6% and 91.4%, while the THA LOS 1-day buffer accuracy and ≤2 days, >2 days classification accuracy were 78.3% and 80.4%. All models across both TKA and THA patients were more accurate than the mean regressors for both DOS and LOS predictions across both buffer and classification accuracies. Conventional and deep MLMs have been effectively implemented to predict the DOS and LOS of elective unilateral TKA and THA patients based on preoperative patient factors using a large North American database with a high level of accuracy. Future work should include using operational factors to further refine these models and improve predictive accuracy. Results of this work will allow institutions to optimize their resource allocation, reduce costs and improve surgical scheduling. Acknowledgements:. The American College of Surgeons National Surgical Quality Improvement Program and the hospitals participating in the ACS NSQIP are the source of the data used herein; they have not verified and are not responsible for the statistical validity of the data analysis or the conclusions derived by the authors

Background. The JOURNEY™ II Cruciate-Retaining Total Knee System (JIICR) and the JOURNEY™ II Bi-Cruciate Stabilized Total Knee System (JIIBCS) (both, Smith & Nephew, Memphis, TN, USA) are used for the treatment of end-stage degenerative knee arthritis. Belonging to the JOURNEY family of knee implants, the relatively new devices are designed to provide guided motion. Studies suggest that long-term outcomes of robotic-assisted navigation in total knee arthroplasty (TKA) are superior to the classical approach. This is the first report describing early postoperative outcomes of the NAVIO® robotic-assisted surgical navigation using the JOURNEY™ II family of knee implants. Materials & Methods. In this ongoing study, six investigational sites in the US prospectively enrolled 122 patients (122 TKAs, 64 JIIBCS and 58 JIICR). Patients underwent TKA using the NAVIO system (Figure 1), a next-generation semi-autonomous tool that uses handheld miniaturized robotic-assisted instrumentation that the surgeon manipulates in 6 degrees of freedom, but restricts cutting to within the confines of the pre-designated resection area of the patient's bone. The primary outcome was postoperative mechanical alignment on long leg X-ray at one month postoperative compared to operative target alignment. Alignment within ±3 degrees of the target alignment was considered a success. Results. Average age was 65.7 years (range, 39–79); 60.7% were females. All patients underwent patella resurfacing. Two patients had revision prior to the one-month follow-up visit; two patients withdrew from the study. 95% (112/118) attended the one-month follow-up. Four patients were missing either baseline or follow-up long leg X-ray, resulting in 108 evaluated TKAs. Overall, 92.6% (100/108) of TKAs were within 3 degrees of the target alignment. Of these, 24.1%, 39.8-, 19.4%, and 9.3% were at 0, 1, 2, and 3 degrees of the target alignment, respectively. There were two revisions, one at 18 days postoperative and the second at 27 days postoperative. Discussion. At the one-month follow-up, the NAVIO™ Robotic Assisted TKA procedures resulted in a very high success rate of 92.6% in achieving planned mechanical alignment compared to standard instruments as historical control (73.4%) based on literature. 1. This demonstrates the improved accuracy and reliability of the NAVIO™ Robotic Assisted Surgical System for TKA procedures. For any figures or tables, please contact the authors directly

Background. Kinematic patterns in total knee arthroplasty (TKA) can vary considerably from the native knee. No study has shown a relation between a given kinematic pattern and patient satisfaction yet. Questions. The purpose of this study was to test whether the kinematical pattern, and more specifically the anteroposterior translation during (1) open kinetic chain flexion-extension, (2) closed kinetic chain chair rising and (3) squatting, is related to the level of patient satisfaction after TKA. Methods. Thirty TKA patients were tested using single plane fluoroscopy. Tibiofemoral kinematics were analyzed for 3 activities of daily living (open chain flexion-extension (FE) and closed chain chair rising (CH) and squatting(SQ)). A two- step cluster analysis was performed which resulted in two clusters of patients based on the KOOS and KSS questionnaires. Cluster 1 (CL1) contained patients with good PROMs, cluster 2 (CL2) contained patients with poorer PROMs. Tibiofemoral kinematics were compared between and within both clusters. Results. Significant worse PROMs were found in cluster 2 for all KOOS and KSS subscores (P<0.001). Open chain movement: Concerning the open chain flexion extension no significant difference was found between the two clusters. Closed chain movements: On the medial side, an initial anterior translation (femur relative to tibia) was found in cluster 1 during early flexion but in cluster 2 this translation was steeper and ran more anteriorly. In mid-flexion a stable medial compartment was found in cluster 1 where cluster 2 started moving posteriorly already. In deep flexion a posterior translation was evaluated in both clusters. Concerning the lateral side, a small initial anterior translation in early flexion was found followed by a posterior translation in mid flexion which continued in deep flexion Cluster 1 moved significantly more posterior in deep flexion. Conclusion. This is one of the first studies to evaluate the influence of total knee kinematics on patient reported outcomes. We found that patients with poorer PROMs experience (1) a more pronounced paradoxical anterior motion on the medial side followed by (2) a less stable medial compartment in mid flexion and (3) less posterior translation in deep flexion on the lateral side

A large proportion of wait times for primary total knee (TKA) and hip (THA) arthroplasty is the time from primary care referral to surgical consultation. To our knowledge, no study has investigated whether a referral Oxford Knee or Hip Score (OKHS) could be used to triage non-surgical referrals appropriately. The primary purpose of the current study was to determine if a referral OKHS has the predictive ability to discriminate when a knee or hip referral will be deemed conservative as compared to surgical by the surgeon during their first consultation, and to identify an OKHS cut-off point that accurately predicts when a primary TKA or THA referral will be deemed conservative. We retrospectively reviewed all consecutive primary TKA and THA consultations from a single surgeon's tertiary, high volume practice over a three-year period. Patients with a pre-consultation OKHS, BMI < 4 1, and no absolute contraindication to TJR were included. Consultation knees/hips were categorized into two groups based on surgeon's decision, those that were offered TJR during their first consolation (surgical) versus those that were not (conservative). Baseline demographic data and OKHS were abstracted. Variables of interest were compared between cohorts using the exact chi-square test and Wilcoxon rank-sum test. Spearman's rank correlation coefficients were used to measure association between pre-consult OKHS and the surgeon's decision. A receiver operator characteristic (ROC) curve analysis was used to calculate the area under the curve (AUC) and to identify a cut-off point for the pre-operative OKHS that identified whether or not a referral was deemed conservative. TKA and THA referrals were analyzed separately. The study included 1,436 knees (1,016 patients) with a median OKS of 25 (IQR 19–32) and 478 hips (388 patients) with a median OHS of 22 (IQR 16–29). Median pre-consultation OKHS demonstrated clinically and statistically significant differences between the surgical versus conservative cohorts (p 32 (sensitivity=0.997, NPV=0.992) and for hips is OHS >34 (sensitivity=0.997 NPV=0.978). ROC analysis identified severable potential lower OKHS thresholds, depending on weight of prioritization of sensitivity, specificity, and NPV. Referral OKS and OHS demonstrate good ability to discriminate when a primary TKA or THA referral will be deemed non-surgical versus surgical at their first consultation in a single surgeon's practice. Multiple potential effective OKHS thresholds can be applied as a tool to decrease wait times for primary joint arthroplasty. However, a cost analysis would aid in identifying the optimal cut-off score, and these findings need to be externally validated before they can be broadly applied

Introduction. Achieving high flexion after total knee arthroplasty is very important for patients in Asian countries where deep flexion activities are an important part of daily life. The Bi-Surface Total Knee System (Japan Medical Material, Kyoto, Japan), which has a unique ball-and-socket mechanism in the mid-posterior portion of the femoral and tibial components, was designed to improve deep knee flexion and long-term durability after total knee arthroplasty (Figure 1). The purpose of this study was to determine the in vivo three dimensional kinematics of Bi-Surface Total Knee System in order to evaluate and analyze the performance of this system with other conventional TKA designs currently available in the market today. Materials and Methods. Three dimensional kinematics were evaluated during a weight-bearing deep knee bend activity using fluoroscopy and a 2D-to-3D registration technique for 66 TKA. Each knee was analyzed to determine femorotibial kinematics, including weight-bearing range of motion, anterior/posterior contact position, and tibio-femoral rotation. Results. The average weight-bearing range of motion for the entire group was 125.5∗∗∗∗∗. Forty three of sixty six knees had greater range of motion than 120∗∗∗∗∗. At full extension, the average contact positions were −0.5mm (range, from −12.2mm to 6.8mm; standard deviation 3.5mm), and −3.8mm (range, from −14.1mm to 6.0mm; standard deviation 4.9mm) for the medial compartment and the lateral compartment, respectively. At maximum flexion, the average contact position was −9.2mm (range, from −17.8mm to 2.4mm; standard deviation 3.7mm), and −14.8mm (range, from −20.1mm to 5.7mm; standard deviation 2.7mm) for the medial compartment and the lateral compartment, respectively (Figure 2). From full extension to maximum flexion, the average posterior femoral rollback observed was −8.7mm (range, from −22.1mm to 1.0mm; standard deviation 4.3mm) for the medial compartment, and −11.0mm (range, from −21.9mm to 6.6mm; standard deviation 5.4mm) for the lateral compartment. At full extension, the average axial orientation was 3.8∗∗∗∗∗ (range, from −5.3∗∗∗∗∗ to 26.4∗∗∗∗∗; standard deviation 5.2∗∗∗∗∗) of external femoral rotation. At maximum flexion, the average axial orientation was 9.5∗∗∗∗∗ (range, from −5.9∗∗∗∗∗ to 27.7∗∗∗∗∗; standard deviation 6.7∗∗∗∗∗). Therefore, from full extension to maximum flexion, the average amount of axial rotation was 5.7∗∗∗∗∗ (range, from −15.1∗∗∗∗∗ to 22.2∗∗∗∗∗; standard deviation 6.4∗∗∗∗∗). Discussion. The Bi-Surface Knee System was designed to accommodate the life style led by Asian populations, by aiming to improve both, knee flexion and long-term durability. Though durability of the device is beyond the scope of this study, subjects in this study did achieve high weight-bearing flexion, excellent posterior femoral rollback of both condyles and a normal axial rotation patterns, albeit, less than the normal knee. Also, this is the first in vivo study conducted to understand the kinematic patterns generated for subject implanted with this device. The amount of posterior rollback and axial rotation were found to be similar in nature to the normal knee as well as other established TKA devices available for implantation today, but again less than the normal knee

Background. Patellofemoral complications have dwindled with contemporary total knee designs that market anatomic trochlear grooves that intend to preserve normal patella kinematics. While most reports of patellofemoral complications address patella and its replacement approach, they do not focus on shape of trochlear grooves in different prostheses [1]. The purpose of this study was to characterize 3D geometry of trochlear grooves of contemporary total knee designs (NexGen, Genesis II, Logic, and Attune) defined in terms of sulcus angle and medial-lateral offset with respect to midline of femoral component in coronal view and to compare to those of native femurs derived from 20 osteoarthritic patient CT scans. Materials and Methods. Using 3D models of each implant and native femur, sulcus location and orientation were obtained by fitting a spline to connect sulcus points marked at 90°, 105°, 130°, and 145° of femoral flexion (Fig A). Implant reference plane orientations were established using inner facets of distal and posterior flanges. Reference planes of native femurs were defined using protocols developed by Eckhoff et al. [2] where coronal plane was defined using femoral posterior condyles and greater trochanter. In the coronal plane, a best fit line was used to measure sulcus angle and medial-lateral offset with respect to midline at the base of trochlear groove (Fig B). Results. With exception to Logic (0° sulcus angle & 0 mm offset), contemporary knee designs include high valgus angulations (4° to 18°) with laterally-biased offsets (3 to 5 mm). The native sulcus angle on average was slightly valgus, but varied significantly among the cohort (−0.2° ± 4.6°). Native trochlear groove offset was biased laterally (2.5 ± 1.7 mm). Discussion. We observed a considerable geometric deviation between native femur and implants in terms of sulcus angle while both geometries displayed comparable lateral bias at the base of trochlear groove. Similar to past studies by Iranpour et al. [4] and Feinstein et al. [5], a large variation in sulcus angle was observed among the selected native femurs with an average of small valgus angulation (Fig C). However, most contemporary trochlear grooves are biased towards higher valgus angulations. Retrieval and registry studies have shown that NexGen trochlear groove design (4° sulcus angle) has been shown to better accommodate natural patellas, which highlights that the differences among designs may be significant [5,6]. It remains unclear which features specifically translate to better patellafemoral outcomes, which is a merit for further study. Conflict of Interest: None. Figure A. Sulcus points defined at various flexion angles. Figure B. Best fit line to measure ML-offset and sulcus angle. Figure C. Sulcus angle comparison to past studies. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

This study aims to implement and assess the inter and intra-reliability of a modernised radiolucency assessment system; the Radiolucency In cemented Stemmed Knee (RISK) arthroplasty classification. Furthermore, we assessed the distribution of regions affected by radiolucency in patients undergoing stemmed cemented knee arthroplasty.

Stemmed knee arthroplasty cases over 7-year period at a single institution were retrospectively identified and reviewed. The RISK classification system identifies five zones in the femur and five zones in the tibia in both the anteroposterior (AP) and lateral planes. Post-operative and follow-up radiographs were scored for radiolucency by four blinded reviewers at two distinct time points four weeks apart. Reliability was assessed using the kappa statistic. A heat map was generated to demonstrate the reported regions of radiolucency.

29 cases (63 radiographs) of stemmed knee arthroplasty were examined radiographically using the RISK system. Intra-reliability (0.83) and Inter-reliability (0.80) scores were both consistent with a strong level of agreement using the kappa scoring system. Radiolucency was more commonly associated with the tibial component (76.6%) compared to the femoral component (23.3%), and the tibial anterior-posterior (AP) region 1 (medial plateau) was the most affected (14.9%).

The RISK classification system is a reliable assessment tool for evaluating radiolucency around stemmed knee arthroplasty using defined zones on both AP and lateral radiographs. Zones of radiolucency identified in this study may be relevant to implant survival and corresponded well with zones of fixation, which may help inform future research.

Aim

Debridement, antibiotics and implant retention (DAIR) are considered as an optimal curative treatment option for prosthetic joint infection (PJI) when the biofilm is still immature and radical debridement is achievable. There are two main groups of patients suitable for DAIR. Those with an early acute PJI and patients with acute hematogenous PJI. However, there is also a third group of early PJI resulting from a wound healing problem or leaking hematoma. These may be either high or low grade depending on the microorganisms that infected the artificial joint “per continuitatem”.

Abstract. By next summer the number of patients in the tranexamic acid group will be much higher, probably around 50–60. Purpose. Tranexamic acid has been extensively studied in single total knee and total hip replacement patients. It has been found to reduce blood loss and transfusion rates, with no increase in the rate of venous thromboembolism. This study was undertaken to determine whether tranexamic acid reduces blood loss and the rate of blood transfusion after bilateral total knee replacement, which has a much higher transfusion rate. Method. The preoperative haemoglobin and the lowest postoperative haemoglobin for 30 consecutive bilateral tkr patients who received tranexamic acid was recorded. These were compared with a a consecutive series of 262 historic controls that did not receive tranexamic acid. All patients were operated on by the same surgeon. The surgical procedure was essentially unchanged throughout the study period. The decision to transfuse was made by the hospitalist, who did not know whether the patient received tranexamic acid. Data calculated included the percentage drop in haemoglobin, and the transfusion rate for each group. A subset of patients who were anaemic preoperatively (Hb < 125) were compared for each group. Results. For the control group, which did not receive tranexamic acid, the average preoperative haemoglobin was 138, and dropped to 85 postoperatively. This represented a 38% drop in haemoglobin. Of the 262 patients, 105 required transfusion, giving a transfusion rate of 40%. The average number of units transfused was 1.8. For the study group, which received tranexamic acid, the average preoperative haemoglobin was 133, and dropped to 97 postoperatively. This represented a 27% drop in haemoglobin. Of the 30 patients, only one required transfusion, giving a transfusion rate of 4%. That one patient required only one unit of blood. For the patients who were anaemic preoperatively (Hb < 125) the transfusion rate for the control group was 97%, and for the study group was 20% (1/5). Conclusion. Tranexamic acid markedly reduces blood loss and the rate of transfusion for patients undergoing bilateral total knee replacement

Deep infection is a devastating complication of total knee arthroplasty (TKA). This study aimed to determine if there was a relationship between surgeon volume and the incidence of revision for infection after primary TKA.

Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) from 1 September 1999 to 31 December 2020 for primary TKA for osteoarthritis that were revised for infection. Surgeon volume was defined by the number of primary TKA procedures performed by the surgeon in the year the primary TKA was performed and grouped as <25, 25-49, 50-74, 75-99, >100 primary TKA procedures per year. Kaplan Meir estimates for cumulative percent revision (CPR) and Cox Proportional Hazard Ratios were performed to compare rates of revision for infection by surgeon volume, with sub-analyses for patella and polyethylene use, age <65 years and male gender.

5295 of 602,919 primary TKA for osteoarthritis were revised for infection. High volume surgeons (>100 TKA/year) had a significantly lower rate of revision for infection with a CPR at 1 and 17 years of 0.4% (95% CI 0.3, 0.4) and 1.5% (95% CI 1.2, 2.0), respectively, compared with 0.6% (95% CI 0.5, 0.7) and 2.1% (95% CI 1.8, 2.3), respectively, for low volume surgeons (<25 TKR/year). Differences between the high-volume group and the remaining groups remained when sub-analysis for age, gender, ASA, BMI, patella resurfacing and the use of cross-linked polyethylene (XLPE).

High volume surgeons have lower rates of revision for infection in primary TKA.

Novel oral anticoagulant (NOAC) use in Australia has increased significantly since their introduction to the Pharmaceutical Benefits Scheme (PBS). Currently, there are no specific guidelines regarding recommencement of NOAC therapy post-operatively for patients concurrently on a NOAC and undergoing arthroplasty. To address this gap in the literature, the aim of this study was to compare the clinical and patient-reported outcomes in a patient cohort recommencing a therapeutic dose of NOAC within 24 hours of total hip or knee arthroplasty.

Data was retrieved from a prospective registry (ACTRN1262000079698) containing hip and knee arthroplasties. Cases were labelled based on whether they presented on a therapeutic dose of NOAC prior to surgery or not. Descriptive statistics were used to summarise patient outcomes.

Of 291 patients undergoing 331 primary arthroplasties, 9.3% were undertaking NOAC therapy prior to their surgery. In the NOAC cohort, there was a 34.5% adverse event rate, however on closer analysis of each event, it was found that none of these events were complications in relation to NOAC use. This was compared to 15.6% of the comparison cohort who experienced a range of complications, some involving bleeding events. PROMs improved to a similar degree amongst both groups.

This study showed that recommencing therapeutic doses of NOACs in patients post hip and knee arthroplasty within 24 hours was safe. These findings will help guide larger scale analysis to better inform clinical guidelines pertaining to hip and knee arthroplasty.

Purpose

Unexpected-positive-intraoperative-cultures (UPIC) in presumed aseptic revision-total-knee-arthroplasties (rTKA) are common, and the clinical significance is not entirely clear. In contrast, in some presumably septic rTKA, an identification of an underlying pathogen was not possible, so called unexpected-negative-intraoperative-cultures (UNIC). The purpose of this study was to evaluate alpha defensin (AD) levels in these patient populations.

INTRODUCTION. Most total knees today are CR or PS, with lateral and medial condyles similar in shape. There is excellent durability, but a shortfall in functional outcomes compared with normals, evidenced by abnormal contact points and gait kinematics, and paradoxical sliding. However unicondylar, medial pivot, or bicruciate retaining, are preferred by patients, ascribed to AP stability or retention of anatomic structures (Pritchett; Zuiderbaan). Recently, Guided Motion knees have been shown to more closely reproduce anatomic kinematics (Walker; Willing; Amiri; Lin; Zumbrunn). As a design approach we proposed Design Criteria: reproduce the function of each anatomic stabilizing structure with bearing surfaces on the lateral and medial sides and intercondylar; resected cruciates because this is surgically preferred; avoid a cam-post because of central femur bone removal, soft tissue entrapment, noises, and damage (Pritchett; Nunley). Our hypothesis was that these criteria could produce a Guided Motion design with normal kinematics. METHODS & MATERIALS. Numerous studies on stability and laxity showed the ACL was essential to controlling posterior femoral displacement on the tibia whether the knee was loaded or unloaded. Under load, the anterior upwards slope of the medial tibial plateau prevented anterior displacement (Griffen; Freeman; Pinskerova; Reynolds). The posterior cruciate and the downward lateral tibial slope produced lateral rollback in flexion. The Replica Guided Motion knee had 3 bearings (Fig 1). The lateral side was shallow and sloped posteriorly, with a posterior lip to prevent excess displacement. The medial anterior tibial and femoral slopes were increased as in the anatomic knee. In the intercondylar region, a saddle bearing replaced ACL function by controlling posterior femoral displacement. For testing, a typical PS design was used as comparison. A Knee Test Machine (Fig 2) flexed the knee, and applied axial compression, shear and torque to represent a range of functions. Bone shapes were reproduced by 3D printing and collaterals by elastomeric bands. Motion was recorded with a digital camera, and Geomagic to process data. RESULTS. The kinematics of normal knees was the benchmark (Arno). The results for neutral path of motion, and the AP laxity about the neutral path, are shown (Fig 3). The PS showed symmetric motion, with anterior medial sliding and excessive constraint in low and high flexion. For the Replica, the medial condyle remained almost constant, but the lateral side rolled posteriorly with flexion, less than normal to prevent damage to the posterior lateral tibial plastic. The lateral side had similar anterior laxity to anatomic, but more than anatomic in late flexion. Based on 10 parameter motion scoring, the Replica was closer to normal than the PS, 82% cf 51%. DISCUSSION. Functional outcomes after TKA are less than normal, TKA design being a likely factor. The approach shown here is intended to reproduce more anatomic kinematics of neutral path of motion and laxity. Such a Replica Guided Motion knee, based on an anatomic structure/stability approach, could reproduce close to normal kinematics even without the cruciates or a cam-post. This may result in improved functional outcomes, and a closer feeling of a normal knee. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. Total knee arthroprasty (TKA) is an excellent treatment with osteoarthritis of the knee joint. The acquisition of joint stability after TKA is one of the most important factors to improve the patient's quality of life. Deep flexion of knee joint is often demanded in daily life, and stability in flexed knee position is also important. But there were few papers reporting about laxity in flexed knee position. This study aimed to analyze influence of pre-operative alignment on post-operative varus-valgus joint laxity in TKA. We investigated the varus-valgus laxity of knee joint throughout flexion intra-operatively before and after prosthetic implantation. Methods. A total of 20 knees underwent TKA using posterior-stabilised (PS) type component by the measured resection method were included in this study. The varus-valgus joint laxity of knee was measured using an intra-operative navigation system at every 10 ° throughout the range of movement under general anesthesia. We examined the correlations between the pre-operative femorotibial angle (FTA) and varus-valgus joint laxity by method of least squeres. We divided the patients group into two populations according to pre-operative FTA. Large FTA group had more than or equal to 186 °of pre-operative FTA. Small FTA group had less than 186 °pre-operative FTA. T- test was performed between those populations. Result. After TKA, mean FTA improved from 189.15 °(SD = 5.87 SD: Standard Deviation) to 172.65 °(SD = 1.59). All of patients were improved in the Knee Society Score (KSS) and range of motion (ROM) (Fig 1). There were significant positive correlations between the pre-operative FTA and varus-valgus joint laxity in flexion of 90 °(CC = 0.48, P < 0.05 CC: Correlation Coefficient P: probability value), 100 °(CC = 0.57, P < 0.01), 110 °(CC = 0.55, P < 0.05), and 120 °(CC = 0.57, P < 0.01). In the large FTA group, the varus-valgus joint laxities were larger than that of small FTA group in initial flexed position before TKA (Fig 2), whereas the varus-valgus joint laxities were larger in flexed position after TKA (Fig 3). Discussion. Our results showed that in patients who had large FTA and were underwent TKA using PS type component by the measured resection method, they had large varus-valgus joint laxities in flexed knee position. There is a possibility that the increase of laxity in the flexed knee position was due to acquisition of stability with releasing of medial collateral ligament in the extended knee position not but in flexed knee position. In this study we demonstrated correlations between the pre-operative FTA and varus-valgus joint laxity in flexed knee position. In the further study, we would like to investigate how the increasing laxities in the flexion knee position affect the clinical symptoms

INTRODUCTION. The majority of papers covering MIS total knee describe a surgical approach where the quads tendon is violated. This presentation describes a modified subvastus approach using MIS technique. The results are compared to the regular subvastus approach. MATERIAL AND METHODS. 423 total knee replacements were performed through MIS subvastus approach from November 2002 to February 2004. All cases were performed by the same surgeon. The subvastus approach was modified to allow more quads excursion so the surgery can be performed without dislocating the patella. The data was processed at University of Dundee. The results were compared to the results of 361 cases of standard subvastus approach performed by the same surgeon. RESULTS. The average skin incision for the MIS group was 10.2 CM. as compared to 18.4 to the standard subvastus. There was no significant difference in the blood loss between the two groups. The progress with rehabilitation was the same in both groups as well. Hospital stay was also the same. DISCUSSION. Kanasaki et al. (ISTA 2002) has shown that patients who had subvastus approach were able to regain the ability to do a straight leg raising faster than the standard parapateller incision. The results in this paper confirm the same showing that the ability of patients to rehabilitate is not related only to the size of the incision. Having relatively small incisions help in shorten hospital stay but did not make any difference in blood loss. CONCLUSION. The subvastus approach is the only true quad sparing approach and it can be performed through 10 cm. incision safely even in heavy patients with severe knee deformity

The purpose of balancing in total knee surgery is to achieve smooth tracking of the knee over a full range of flexion without excessive looseness or tightness on either the lateral or medial sides. Balancing is controlled by the alignment of the bone cuts, the soft tissue envelope, and the constraint of the total knee. Recently, Instrumented Tibial Trials (OrthoSensor) which measure and display the location and magnitude of the forces on the lateral and medial condyles, have been introduced, offering the possibly of predictive and quantitative balancing. This paper presents the results of experiments on 10 lower limb specimens, where the effects of altering the bone cuts or the femoral component size were measured. A special leg mounting rig was fixed to a standard operating table. A boot was strapped to the foot, and the boot tracked along a horizontal rail to allow flexion-extension. The initial bone cuts were carried out by measured resection using a navigation system. The trial femoral component and the instrumented tibial trial were inserted, and the following tests carried out:. Sag Test; foot lifted up, the trial thickness chosen to produce zero flexion. Heel Push Test; heel moved towards body to maximum flexion. Varus-Valgus Test, AP and IXR Tests were also carried out, but not discussed here. For an initial state of the knee, close to balanced, the lateral and medial contact forces were recorded for the full flexion range. The mean value of the contact forces per condyle was 77.4N, the mean in early flexion (0–60 deg) was 94.2N, and the mean in late flexion (60–120 deg) was 55.7N. The difference was due to the effect of the weight of the leg. One of the following Surgical Variables was then implemented, and the contact forces again recorded. . 1. Distal femoral cut; 2 mm resection (2 mm increase in insert thickness to preserve extension). 2. Tibial frontal varus, 2 mm lateral stuffing. 3. Tibial frontal valgus, 2 mm medial stuffing. 4. Tibial slope angle increase (5 deg baseline); +2 degrees. 5. Tibial slope angle decrease (5 deg baseline); −2 degrees. 6. Increase in AP size of femoral component (3 mm). The differences between the condyle force readings before and after the Surgical Variable were calculated for low and high angular ranges. The mean values for the 10 knees of the differences of the above Surgical Variables from the initial balanced state are shown in the chart. From literature data, the mean tension increase in one collateral ligament is close to 25N/mm up to the toe of the load-elongation graph, and 50N/mm after the toe. Hence in the initial balanced state, the collateral ligaments were elongated by 2–4 mm producing pretension. From the Surgical Variables data, up to 2 mm/2 deg change in bone cuts (or 3 mm femcom change), and collateral ligament releases up to 2 mm, would correct from any unbalanced state to a balanced state. This data provides useful guidelines for the use of the Instrumented Tibial Trials at surgery, in terms of bone cut adjustments and ligament releases

Surgical Site Infection (SSI) is one of the most frequent nosocomial infections and depends on many factors: patient, microorganism, antiseptic solution use, antibiotic prophylaxis, hand scrubbing, wound care or hospital stay lenght. With the present paper the authors aim to study the SSI incidence after Total Knee (TKA) or Hip Arthroplasty (THA). All patients who underwent primary TKA or THA between January 2011 and May 2012 at our institution were considered. Patients who died within 1 year after the procedure of unrelated causes were excluded. Data collected included ASA classification, type of procedure, total and post-operative hospital stay, type and duration of antibiotic prophylaxis. Data were collected from the consultation at 1 month and 1 year post-operative, clinical registries and telephone interview. SSI was defined according to the Centers for Disease Control and Prevention criteria. Suspected cases of SSI included antibiotic administration longer than 5 days or absence of antibiotic prescription, hospital stay after the procedure longer than 9 days, patient referring infection symptoms, and clinical data reports of infection or re-intervention. During the studied period and after exclusion of 5 cases, a total of 251 surgeries (104 TKA, 147 THA) were performed, of which 2 were urgent. For both TKA and THA, the average total hospital stay was 9 days (8 days post-operative). The majority were American Society of Anesthesiologists (ASA) classification 2 and 3. There were 4 SSI (1,60%), 2 TKA (1,92%) and 2 THA (1,36%), all of them after discharge. Their average total hospital stay was 10,5 days. Antibiotic prophylaxis was used in 93% of the patients (97,4% a cephalosporin), with an average length of 5,7 days. Recommended hospital stay after a TKA or THA is about 5 days. On HELICS-CIRURGIA 2006–2010 report it was 10 days, similar to ours. In infected patients, our total hospital stay was lower (10,5 vs 26). Recommended duration of antibiotic prophylaxis is 24h. On HELICS-CIRURGIA more than 50% had it for more than 24h, which also happened with us; our antibiotic coverage was similar. Comparing to HELICS-CIRURGIA, the predominance of ASA 2 and 3 classifications was similar, but the overall SSI rate was lower (1,6% vs 2,24%). We conclude we must reduce hospital stay and antibiotic duration and keep the surveillance of SSI after TKA or THA

Internal fixation for supracondylar fracture of the femur after total knee arthroplasty (TKA) is technically difficult and troublesome because the distal bony fragment is often osteoporotic and too small to fix by screws or K-wires. In addition, the femoral component interferes with the screws or K-wires to be inserted from distal direction for fixation of the fracture. Patients and Methods. Four knees in 4 patients (all female; average age, 81.5 +/− 2.6 years) with the fracture after TKA were treated with revision TKA. Follow-up period was between six months and 3 years postoperatively. Operative technique. All operations were performed with the patient in the supine position and using a curved anterior (Payer) approach with or without osteotomy of the tuberositas tibiae. The femoral component was removed with detachment from fractured bony fragments. New femoral component with long stem for fixation of the fracture were inserted with bone cement in each case. Post-operative regimen. On the third postoperative day the patient began flexion and exension exercise of the operated knee joint with a rehabilitation programmed by clinical path under the supervision of a physiotherapist. The use of crutches for ambulation was begun on the 10. th. to 14. th. postoperative day, and the extent of weight bearing was allowed individually according to the stability of the fixation of the fracture. The time to full weight bearing in each patient was 3 to 8 weeks postoperatively. Results. Postoperative courses were uneventful in all of the cases. The supracondylar fracture of the femur was rigidly fixed and healed radiographically within 8 weeks postoperatively in each case. The JOA scores were improved in all od the cases. The mean Japanese Orthopaedic Association (JOA) scores for the knees improved to 90 points postoperative. No femoral components had definite radiographic evidence of loosening and were re-revised. Discussion. In the current study of short-term results of revision total knee arthroplasty for treatment of supracondylar fracture of the femur after total knee with osteoporosis, the component have shown to remain stable in weight bearing conditions and functioned well. Fracture healing and good clinical outcome, evaluated according to the JOA score, were achieved in all cases. Longer-term outcome should be the subject of further investigation. Conclusion. The revision TKA was a successful method for treatment of the supracondylar fracture after TKA