Numerous papers present in-vivo knee kinematics data following total knee arthroplasty (TKA) from fluoroscopic testing. Comparing data is challenging given the large number of factors that potentially affect the reported kinematics. This paper aims at understanding the effect of following three different factors: implant geometry, performed activity and analysis method.

A total of 30 patients who underwent TKA were included in this study. This group was subdivided in three equal groups: each group receiving a different type of posterior stabilized total knee prosthesis. During single-plane fluoroscopic analysis, each patient performed three activities: open chain flexion extension, closed chain squatting and chair-rising. The 2D fluoroscopic data were subsequently converted to 3D implant positions and used to evaluate the tibiofemoral contact points and landmark-based kinematic parameters.

Significantly different anteroposterior translations and internal-external rotations were observed between the considered implants. In the lateral compartment, these differences only appeared after post-cam engagement. Comparing the activities, a significant more posterior position was observed for both the medial and lateral compartment in the closed chain activities during mid-flexion. A strong and significant correlation was found between the contact-points and landmarks-based analyses method. However, large individual variations were also observed, yielding a difference of up to 25% in anteroposterior position between both methods.

In conclusion, all three evaluated factors significantly affect the obtained tibiofemoral kinematics. The individual implant design significantly affects the anteroposterior tibiofemoral position, internal-external rotation and timing of post-cam engagement. Both kinematics and post-cam engagement additionally depend on the activity investigated, with a more posterior position and associated higher patella lever arm for the closed chain activities. Attention should also be paid to the considered analysis method and associated kinematics definition: analyzing the tibiofemoral contact points potentially yields significantly different results compared to a landmark-based approach.

Background

The current average tariff of a total knee replacement (TKR) is £5500. The approximate cost of each knee prosthesis is £2500. Therefore, length of patient stay (LOS) and the cost of patient rehabilitation influence the total costs significantly. Previous studies have shown a mean LOS of between 5 and 9.4 days for patients undergoing primary unilateral TKR but none looked at the factors influencing length of stay following bilateral primary total knee replacements (BTKR) at the same sitting.

Background

Post-operative acute kidney injury is significant complication following surgery. Patients who develop AKI have an increased risk for progression into chronic kidney disease, end-stage renal failure and increased mortality risk. The patient outcomes following total knee replacement (TKR), who develop AKI has been a topic of interest in recent years as it may have patient and medicolegal implications. Nevertheless, there are no studies looking at the incidence, risk factors and outcomes of AKI following bilateral TKRs at the same sitting.

Experimental simulation is the gold standard wear testing method for total knee replacements (TKR), with reliable replication of physiological kinematic conditions. When combined with a computational model, such a framework is able to offer deeper insight into the biomechanical and wear mechanisms. The current study developed and validated a comprehensive combined experimental and computational framework for pre-clinical biomechanics and wear simulation of TKR.

A six-station electro-mechanical knee simulator (SimSol, UK), capable of replicating highly demanding conditions with improved input kinematic following, was used to determine the wear of Sigma fixed bearing curved TKRs (DePuy, UK) under three different activities; standard-walking, deep-squat, and stairs-ascending. The computational model was used to predict the wear under these 3 conditions. The wear calculation was based on a modification of Archard's law which accounted for the effects of contact stress, contact area, sliding distance, and cross-shear on wear. The output wear predictions from the computational model were independently validated against the experimental wear rates.

The volumetric wear rates determined experimentally under standard-walking, deep-squat, and stairs-ascending conditions were 5.8±1.4, 3.5±0.8 and 7.1±2.0 [mm3/mc] respectively (mean ± 95% CI, n=6). The corresponding predicted wear rates were 4.5, 3.7, and 5.6 [mm3/mc]. The coefficient of determination for the wear prediction of the framework was 0.94.

The wear predictions from the computational model showed good agreement with the experimental wear rates. The model did not fully predict the changes found experimentally, indicating other factors in the experimental simulation not yet incorporated in the framework, such as plastic deformation, may play an additional role experimentally in high demand activities. This also emphasises the importance of the independent experimental validation of computational models.

The combined experimental and computational framework offered deeper insight into the contact mechanics and wear from three different standard and highly demanding daily activities. Future work will adopt the developed framework to predict the effects of patients and surgical factors on the mechanics and wear of TKR.

Summary Statement

Wear of total knee replacement (TKR) is a clinical concern. This study demonstrated low-conformity moderately cross-linked-polyethylene fixed bearing TKRs showed lower volumetric wear than conventional-polyethylene curved fixed bearing TKRs highlighting potential improvement in TKR performance through design and material selection.

Total knee replacements (TKR) have been the main choice of treatment for alleviating pain and restoring physical function in advanced degenerative osteoarthritis of the knee. Recently, there has been a rising interest in minimally invasive surgery TKR (MIS-TKR). However, accurate restoration of the knee axis presents a great challenge. Patient-specific-instrumented TKR (PSI-TKR) was thus developed to address the issue. However, the efficacy of this new approach has yet to be determined. The purpose of the current study was thus to measure and compare the 3D kinematics of the MIS-TKR and PSI-TKR in vivo during sit-to-stand using a 3D fluoroscopy technology.

Five patients each with MIS-TKR and PSI-TKR participated in the current study with informed written consent. Each subject performed quiet standing to define their own neutral positions and then sit-to-stand while under the surveillance of a bi-planar fluoroscopy system (ALLURA XPER FD, Philips). For the determination of the 3D TKR kinematics, the computer-aided design (CAD) model of the TKR for each subject was obtained from the manufacturer including femoral and tibial components and the plastic insert. At each image frame, the CAD model was registered to the fluoroscopy image via a validated 2D-to-3D registration method. The CAD model of each prosthesis component was embedded with a coordinate system with the origin at the mid-point of the femoral epicondyles, the z-axis directed to the right, the y-axis directed superiorly, and the x-axis directed anteriorly. From the accurately registered poses of the femoral and tibial components, the angles of the TKR were obtained following a z-x-y cardanic rotation sequence, corresponding to flexion/extension, adduction/abduction and internal/external rotation.

During sit-to-stand the patterns and magnitudes of the translations were similar between the MIS-TKR and PSI-TKR groups, with posterior translations ranging from 10–20 mm and proximal translations from 29–31mm. Differences in mediolateral translations existed between the groups but the magnitudes were too small to be clinically significant. For angular kinematics, both groups showed close-to-zero abduction/adduction, but the PSI-TKR group rotated externally from an internally rotated position (10° of internal rotation) to the neutral position, while the MIS-TKR group maintained at an externally rotated position of less than 5° during the movement.

During sit-to-stand both groups showed similar patterns and magnitudes in the translations but significant differences in the angular kinematics existed between the groups. While the MIS-TKR group maintained at an externally rotated position during the movement, the PSI-TKR group showed external rotations during knee extension, a pattern similar to the screw home mechanism in a normal knee, which may be related to more accurate restoration of the knee axis in the PSI-TKR group. A close-to-normal angular motion may be beneficial for maintaining a normal articular contact pattern, which is helpful for the endurance of the TKR. The current study was the first attempt to quantify the kinematic differences between PSI and non-PSI MIS. Further studies to include more subjects will be needed to confirm the current findings. More detailed analysis of the contact patterns is also needed.

The number of primary Total Knee Arthroplasty (TKA) and primary Total Hip Arthroplasty (THA) procedures carried out in England and Wales is increasing annually. The British Orthopaedic Association guidelines for follow up currently differ for patients with TKA and THA. In THA the BOA recommends that Orthopaedic Data Evaluation Panel (ODEP) 10A rated implants should be followed up in the first year, once at seven years and three yearly thereafter. The BOA guidelines for TKA minimum requirement is radiographs at 5 years and each five years thereafter. Few studies have investigated if early follow up affects patient management following total hip and knee arthroplasty

We carried out a retrospective review of all revision procedures carried out in our institution between April 2010 to April 2013. The medical notes and radiographs for each patient were examined to determine the operative indications and patients symptoms. 92 knee revisions and 143 hip revisions were identified. Additionally we retrospectively reviewed the outcome of 300 one year routine arthroplasty follow up appointments.

The mean time of hip revision was 8.5years (range 0 to 27years) and 5.6years (range 0 to 20years) for knee revisions. The commonest cause for revision was aseptic loosening associated with pain in 49 (53%) of knee revision patients and 89 (63%) of hip revisions. Infection accounted for 26 (28%) knee revisions and 16 (12%) hip revisions. Only 1% of hip and knee revisions was carried out in asymptomatic patients with aseptic loosening.

We did not identify any cases were a patients management was altered at the routine arthroplasty review clinic and none were referred on for further surgical treatment. The findings of our study suggest there is no evidence for a routine one year arthroplasty review and revisions were carried out in asymptomatic patients in 1% of patients.

Summary

In this study we validate that weight-bearing images are needed for accurate polyethylene liner wear measurement in total knee prostheses by measuring the difference in minimum joint space width between weight-bearing and non-weight-bearing RSA views.

Summary Statement

Using current analysis/methodology, new implant technology is unlikely to demonstrate a large enough change in patient function to impact on the cost-effectiveness of the procedure.

We aimed to determine the impact of anaesthetic techniques on post-operative analgesic utilisation in people undergoing total knee arthroplasty. We conducted a prospective study at a district general hospital to assess post-operative analgesia use via patient controlled analgesia (PCA) in patients undergoing a elective total knee arthroplasty. Subjects were divided into three groups; group 1 (general anaesthetic and local nerve block, n = 39), group 2 (spinal only, n= 39) and group 3 (general anaesthetic only, n = 38). The primary outcome measure was post-operative morphine consumption through a PCA within the first 24 hours. All subjects were followed up post-operatively by a dedicated pain control nurse. Data was analysed using SPSS version 17 for Windows (SPSS Inc, Chicago, IL, USA).

Results are reported as mean (SD) unless stated otherwise. No significant difference in the age or sex distribution between groups was demonstrable. There was no statistical difference in the average usage of morphine when comparing Group 1 compared to group 2, (77.57 (49.56) vs 65.80 (44.71), p=0.27), group 1 compared to group 3, (77.57 (49.56) vs 77.80 (45.52) p=0.98) and finally group 2 compared to group 3, (65.80 (44.71) vs 77.80 (45.52), p=0.25).

In this cohort of patients undergoing total knee arthroplasty the anaesthetic technique used does not appear to have an influence on the post-operative pain management.

The price per total knee replacement (TKR) performed is fixed but the subsequent length of hospital stay (LOS) is variable. The current national average for LOS following TKR is six days. LOS is an important marker of resource consumption, has implications in patient satisfaction, and is used as a marker of hospital quality. The aim of this study was to describe the temporal change in demographics between 2004 and 2009, and to identify intra-operative factors and patient characteristics associated with a prolonged LOS that could be addressed to improve clinical practice. We performed a retrospective cohort review of 184 patients (2004 n=88, 2009 n=96) who underwent primary TKRs at Chorley District General Hospital. The median LOS in 2009 was eight days compared to ten days in 2004, an average of 3.5 days less (p < 0.001). Patients were significantly younger (p < 0.001) in 2009 (median 66 years) compared to 2004 (median 74 years), with both years having a similar female predominance. There was no significant change in the BMI or American Society of Anesthesiologists score between 2004 and 2009. This data suggests that block contracts with the private sector has not influenced the demographics of patients being treated in the NHS. Intra-operative factors including the use of a peripheral nerve block, the surgeon grade, the day of the week the operation was performed, the operation length, and the change in pre- to post-operative haemoglobin were not found to significantly increase the LOS (p = 0.058, p = 0.40, p = 0.092, p = 0.50, p = 0.43 respectively). Cemented TKRs had a median LOS of nine days compared to eight for uncemented implants (p = 0.015). However, patients with a cemented implant were on average 6.2 years older than patients with an uncemented implant (p < 0.001). Using Cox proportional hazard regression modelling, the occurrence of a post-operative complication (p < 0.001), female sex (p = 0.024), advancing age (p = 0.036), and the need for a blood transfusion (p = 0.0056) were the most significant factors for prolonging the LOS. Patients who were given a transfusion stayed a median of 13 days compared to nine for those who did not (p < 0.001). The median pre-operative haemoglobin for those who required a transfusion was 11.85g/dl compared to 13.6g/dl for those who did not (p < 0.001). Being obese or morbidly obese did not significantly prolong the LOS (p = 0.95).

In conclusion, this study highlights significant patient characteristics which are associated with a prolonged LOS following TKR. The relatively low pre-operative haemoglobin in patients requiring a blood transfusion is a potential target for reducing the LOS.

Allogeneic blood transfusion is associated with many complications and significant cost. The RD&E has looked at the use of autologous drains after our study of 100 cases showed an improved post-operative haemoglobin and reduced length of stay. There is a need to identify those patients of increased need for an autologous drain, in order to decrease the frequency of allogeneic transfusion. In 2007 a protocol was drawn up using information from our study of 191 cases which showed an average haemoglobin drop post-operatively of 3.05g/dl and average intra-operative blood loss of 285 ml. This protocol gives the surgeon triggers for autologous drain use; preoperative haemoglobin of <13g/dl, intra-operative blood loss of >400ml, tourniquet use, patient weight <50kg and patients refusing donated blood.

In 2007-08, 65% of a further 275 cases analysed met the triggers for use of an autologous system. The remaining patients received low vacuum drains. Of the 275 patients, only 2 (<1%) of those who did not fulfil the criteria for an autologous drain required allogeneic blood, compared with 43 patients (24%) of those deemed high risk of transfusion, and assigned autologous drains. The protocol was therefore deemed to be successful in identifying those patients who required additional support and expenditure to minimise allogeneic blood transfusion.

Analysis of this data led to recommended changes to the protocol in order to maximise the efficiency of the autologous drain use. In 2010 a further patient cohort studied showed a reduction in allogeneic blood transfusion to <10% of those receiving autologous drains, and an increase to 5% of those with low vacuum drains.

Due to the increased cost of autologous drains (£68) compared with the low vacuum systems (£32), and the cost of allogeneic units at £141, the expenditure per patient was calculated and shown to fall from £92 in 2007 to £78 in the 2010.

In conclusion, this protocol allows the clinician to appropriately target the use of the more expensive autologous drains to those of increased risk of transfusion. This protocol helps to minimise unnecessary allogeneic blood transfusion risks, and this has been shown to be more cost effective.

INTRODUCTION

Useful feedback from a Total Knee Replacement (TKR) can be obtained from post-surgery in-vivo assessments. Dynamic Fluoroscopy and 3D model registration using the method of Banks and Hodge (1996) [1] can be used to measure TKR kinematics to within 1° of rotation and 0.5mm of translation, determine tibio-femoral contact locations and centre of rotation. This procedure also provides an accurate way of quantifying natural knee kinematics and involves registering 3D implant or bone models to a series of 2D fluoroscopic images of a dynamic movement.

In severe cases of total knee & hip arthroplasty, where off-the-shelf implants are not suitable (i.e., in cases with extended bone defects or periprosthetic fractures), 3D-printed custom-made knee & hip revision implants out of titanium or cobalt-chromium alloy represent one of the few remaining clinical treatment options. Design verification and validation of such custom-made implants is very challenging. Therefore, a methodology was developed to support surgeons and engineers in their decision on whether a developed design is suitable for the specific case. A novel method for the pre-clinical testing of 3D-printed custom-made knee implants has been established, which relies on the biomechanical test and finite element analysis (FEA) of a comparable clinically established reference implant. The method comprises different steps, such as identification of the main potential failure mechanism, reproduction of the biomechanical test of the reference implant via FEA, identification of the maximum value of the corresponding FEA quantity of interest at the required load level, definition of this value as the acceptance criterion for the FEA of the custom-made implant, reproduction of the biomechanical test with the custom-made implant via FEA, decision making for realization or re-design based on the acceptance criterion is fulfilled or not. Exemplary cases of custom-made knee & hip implants were evaluated with this new methodology. The FEA acceptance criterion derived from the reference implants was fulfilled in both custom-made implants and subsequent biomechanical tests verified the FEA results. The suggested method allows a quantitative evaluation of the biomechanical properties of custom-made knee & hip implant without performing physical bench testing. This represents an important contribution to achieve a sustainable patient treatment in complex revision total knee & hip arthroplasty with custom-made 3D printed implants in a safe and timely manner

Total knee and hip arthroplasty (TKA and THA) are the most commonly performed surgical procedures, the costs of which constitute a significant healthcare burden. Improving access to care for THA/TKA requires better efficiency. It is hypothesized that this may be possible through a two-stage approach that utilizes prediction of surgical time to enable optimization of operating room (OR) schedules. Data from 499,432 elective unilateral arthroplasty procedures, including 302,490 TKAs, and 196,942 THAs, performed from 2014-2019 was extracted from the American College of Surgeons (ACS) National Surgical and Quality Improvement (NSQIP) database. A deep multilayer perceptron model was trained to predict duration of surgery (DOS) based on pre-operative clinical and biochemical patient factors. A two-stage approach, utilizing predicted DOS from a held out “test” dataset, was utilized to inform the daily OR schedule. The objective function of the optimization was the total OR utilization, with a penalty for overtime. The scheduling problem and constraints were simulated based on a high-volume elective arthroplasty centre in Canada. This approach was compared to current patient scheduling based on mean procedure DOS. Approaches were compared by performing 1000 simulated OR schedules. The predict then optimize approach achieved an 18% increase in OR utilization over the mean regressor. The two-stage approach reduced overtime by 25-minutes per OR day, however it created a 7-minute increase in underutilization. Better objective value was seen in 85.1% of the simulations. With deep learning prediction and mathematical optimization of patient scheduling it is possible to improve overall OR utilization compared to typical scheduling practices. Maximizing utilization of existing healthcare resources can, in limited resource environments, improve patient's access to arthritis care by increasing patient throughput, reducing surgical wait times and in the immediate future, help clear the backlog associated with the COVID-19 pandemic

Among the advanced technology developed and tested for orthopaedic surgery, the Rizzoli (IOR) has a long experience on custom-made design and implant of devices for joint and bone replacements. This follows the recent advancements in additive manufacturing, which now allows to obtain products also in metal alloy by deposition of material layer-by-layer according to a digital model. The process starts from medical image, goes through anatomical modelling, prosthesis design, prototyping, and final production in 3D printers and in case post-production. These devices have demonstrated already to be accurate enough to address properly the specific needs and conditions of the patient and of his/her physician. These guarantee also minimum removal of the tissues, partial replacements, no size related issues, minimal invasiveness, limited instrumentation. The thorough preparation of the treatment results also in a considerable shortening of the surgical and of recovery time. The necessary additional efforts and costs of custom-made implants seem to be well balanced by these advantages and savings, which shall include the lower failures and revision surgery rates. This also allows thoughtful optimization of the component-to-bone interfaces, by advanced lattice structures, with topologies mimicking the trabecular bone, possibly to promote osteointegration and to prevent infection. IOR's experience comprises all sub-disciplines and anatomical areas, here mentioned in historical order. Originally, several systems of Patient-Specific instrumentation have been exploited in total knee and total ankle replacements. A few massive osteoarticular reconstructions in the shank and foot for severe bone fractures were performed, starting from mirroring the contralateral area. Something very similar was performed also for pelvic surgery in the Oncology department, where massive skeletal reconstructions for bone tumours are necessary. To this aim, in addition to the standard anatomical modelling, prosthesis design, technical/technological refinements, and manufacturing, surgical guides for the correct execution of the osteotomies are also designed and 3D printed. Another original experience is about en-block replacement of vertebral bodies for severe bone loss, in particular for tumours. In this project, technological and biological aspects have also been addressed, to enhance osteointegration and to diminish the risk of infection. In our series there is also a case of successful custom reconstruction of the anterior chest wall. Initial experiences are in progress also for shoulder and elbow surgery, in particular for pre-op planning and surgical guide design in complex re-alignment osteotomies for severe bone deformities. Also in complex flat-foot deformities, in preparation of surgical corrections, 3D digital reconstruction and 3D printing in cheap ABS filaments have been valuable, for indication, planning of surgery and patient communication; with special materials mimicking bone strength, these 3D physical models are precious also for training and preparation of the surgery. In Paediatric surgery severe multi planar & multifocal deformities in children are addressed with personalized pre-op planning and custom cutting-guides for the necessary osteotomies, most of which require custom allografts. A number of complex hip revision surgeries have been performed, where 3D reconstruction for possible final solutions with exact implants on the remaining bone were developed. Elective surgery has been addressed as well, in particular the customization of an original total ankle replacement designed at IOR. Also a novel system with a high-tibial-osteotomy, including a custom cutting jig and the fixation plate was tested. An initial experience for the design and test of custom ankle & foot orthotics is also in progress, starting with 3D surface scanning of the shank and foot including the plantar aspect. Clearly, for achieving these results, multi-disciplinary teams have been formed, including physicians, radiologists, bioengineers and technologists, working together for the same goal

Abstract. Objective. Explore whether high tibial osteotomy (HTO) changes knee contact forces and to explore the relationship between the external knee adduction moment (EKAM) pre and 12 months post HTO. Methods. Three-dimensional gait analysis was performed on 17 patients pre and 12-months post HTO using a modified Cleveland marker-set. Tibiofemoral contact forces were calculated in SIMM. The scaled musculoskeletal model integrated an extended knee model allowing for 6 degrees of freedom in the tibiofemoral and patellofemoral joint. Joint angles were calculated using inverse kinematics then muscle and contact forces and secondary knee kinematics were estimated using the COMAC algorithm. Paired samples t-test were performed using SPSS version 25 (SPSS Inc., USA). Testing for normality was undertaken with Shapiro-Wilk. Pearson correlations established the relationships between EKAM1 to medial KCF1, and EKAM2 to medial KCF2, pre and post HTO. Results. Total knee contact force peak 1 significantly reduced from 2.6 x body weight pre-HTO to 2.3 x body weight 12-months post-HTO. Medial contact force peak 1 significantly reduced from 1.7 x body weight pre-HTO to 1.5 x body weight 12-months post-HTO. Second peak lateral knee contact force significantly increased from 0.9 body weight pre-HTO to 1.1 x body weight 12-months post-HTO. Furthermore, this study found very strong correlations between EKAM1 and medial KCF1 pre-HTO (r=0.85) as well as post-HTO (r=0.91). There was a significantly moderate relationship between EKAM2 and medial KCF2 pre-HTO (r=0.625). Conclusion. HTO significantly reduced overall and medial KCF during the first half of stance whilst increasing second half of stance peak lateral knee contact force. This study demonstrated a strong relationship between EKAM peaks and respective medial KCF peaks, supporting the usefulness of EKAM as a surrogate measure of medial compartment tibiofemoral contact forces. This demonstrates HTO successfully offloads the tibiofemoral joint overall, as well as offloading the medial compartment

Regulatory bodies impose stringent pre-market controls to certify the safety and compatibility of medical devices. However, internationally recognized standard tests may be expensive, time consuming and challenging for orthopedic implants because of many possible sizes and configurations. In addition, cost and time of standard testing may endanger the feasibility of custom-device production obtained through innovative manufacturing technologies like 3d printing. Modeling and simulation (M&S) tools could be used by manufactures and at point-of-care to improve design confidence and reliability, accelerate design cycles and processes, and optimize the amount of physical testing to be conducted. We propose an integrated cloud platform to perform in silico testing for orthopedic devices, assessing mechanical safety and electromagnetic compatibility, in line with recognized standards and regulatory guidelines. The . InSilicoTrials.com. platform contains two M&S tools for orthopedic devices: CONSELF and NuMRis. CONSELF (. conself.com. ) uses Salome-Meca 2017 to compute static implant stresses and strains on metallic orthopedic devices, following the requirements and considerations of ASTM F2996-20 for non-modular hip femoral stems and ASTM F3161-16 for total knee femoral components. Simulation results were consistent with those reported in the two standards. NuMRis (. numris.insilicomri.com. ) uses ANSYS HFSS and ANSYS Mechanical 2019R3 to compute radio-frequency energy absorption and induced heating in 1.5T and 3T MRI coils, replicating the ASTM F2182-19e2 Standard Test Method. Simulation results were validated against in vitro measurements. The integrated M&S workflow on the cloud platform allows the user to upload the 3D geometry and the material properties of the orthopedic device to be tested, automatically set up the standard testing scenarios, run simulations and process outcome, with the option to summarize the results in accordance with current FDA guidance on M&S reporting. The easy-to-use interfaces of InSilicoTrials tools run through commercial web browsers, requiring no specific expertise in computational methods or additional on-premise software and hardware resources, since all simulations are run remotely on cloud infrastructure. The integrated cloud platform can be used to evaluate design alternatives, test multi-configuration devices, perform multi-objective design optimization and identify worst-case scenarios within a family of implant sizes, or to assess the safety and compatibility of custom-made orthopedic devices. InSilicoTrials.com. is the first cloud platform offering a collection of M&S tools to perform in silico standard testing for orthopedic devices. The proposed tools allow to assess mechanical safety and electromagnetic compatibility before prototyping, preventing risks and criticalities for the patient, and helping manufacturers and point-of-care to accelerate time and reduce costs during the device development. The proposed platform promotes the broader adoption of digital evidence in preclinical trials, supporting the device submission process and pre-market regulatory evaluation, and helping secure regulatory approval

Backgroud: Allogeneic transfusion rates after primary hip and knee arthroplasty are used as quality indicators for hospitals, but hospital comparisons may be hampered by low event rates. Extended hospital stay is often used and may be more suitable as an alternative. This study aims to assess whether transfusion rates and extended hospital stay can be used to reliably rank hospitals. Methods. We used the baseline data from the LISBOA implementation trial, where data on patient characteristics and outcomes were collected in a sample of approximately 100 patients undergoing elective primary total hip or knee arthroplasty for each of the 23 participating hospitals. We calculated the reliability of ranking (Rankability) of transfusion rates and extended hospital stay (> 4 postoperative days), using fixed and random effects logistic regression analysis, by dividing the between-hospital variation to the sum of within and between-hospital variation. Rankability thus shows which part of the hospital differences are true differences and not due to random variation. Results. 1163 total hip and 986 total knee procedures were assessed. After adjustment for patient characteristics the odds ratio (OR) of receiving a transfusion in a hospital after total hip ranged from 0.72 to 1.38 and from 0.30 to 3.30 in total knee. Rankability was 17% for hip and 36% for knee arthroplasty, meaning that only 17% and 36% are true hospital differences. Larger hospital variation was found for extended hospital stay (OR range [0.28–3.51] for hip and [0.10–9.95] for knee arthroplasty), and better rankability. Conclusion. Although allogeneic transfusion rates are useful for monitoring quality within hospitals, they should not be used for ranking hospitals. A large proportion of differences in transfusion rates between hospitals is due to random variation, suggesting that this outcome is not suitable for ranking hospitals contrary to extended hospital stay. Level of evidence. Level 2. Financial disclosure. This study was funded by a grant from The Netherlands Organisation for Health Research and Development and by a grant from Sanquin Blood Supply. Conflict of interest. The authors declare that there are no conflicts of interest. Approval. The Medical Ethical Committee of the Leiden University Medical Center decided that ethical approval was not required under Dutch National law for this type of study

Whilst home-based exercise rehabilitation plays a key role in determining patient outcomes following orthopaedic intervention (e.g. total knee replacement), it is very challenging for clinicians to objectively monitor patient progress, attribute functional improvement (or lack of) to adherence/non-adherence and ultimately prescribe personalised interventions. This research aimed to identify whether 4 knee rehabilitation exercises could be objectively distinguished from each other using lower body inertial measurement units (IMUs) and principle components analysis (PCA) in the hope to facilitate objective home monitoring of exercise rehabilitation. 5 healthy participants performed 4 repetitions of 4 exercises (knee flexion in sitting, knee extension, single leg step down and sit to stand) whilst wearing lower body IMU sensors (Xsens, Holland; sampling at 60 Hz). Anthropometric measurements and a static calibration were combined to create the biomechanical model, with 3D hip, knee and ankle angles computed using the Euler sequence ZXY. PCA was performed on time normalised (101 points) 3D joint angle data which reduced all joint angle waveforms into new uncorrelated PCs via an orthogonal transformation. Scatterplots of PC1 versus PC2 were used to visually inspect for clustering between the PC values for the 4 exercises. A one-way ANOVA was performed on the first 3 PC values for the 9 variables under analysis. Games-Howell post hoc tests identified variables that were significantly different between exercises. All exercises were clearly distinguishable using the PC scatterplot representing hip flexion-extension waveforms. ANOVA results revealed that PC1 for the knee flexion angle waveform was the only PC value statistically different across all exercises. Findings demonstrate clear potential to objectively distinguish between different knee rehabilitation exercises using IMU sensors and PCA. Flexion-extension angles at the hip and knee appear most suited for accurate separation, which will be further investigated on patient data and additional exercises