An Optimization System for Intent Recognition Based on an Improved KNN Algorithm with Minimal Feature Set for Powered Knee Prosthesis

In this article,a new optimization system that uses few features to recognize locomotion with high classification accuracy is proposed.The optimization system consists of three parts.First,the features of the mixed mechanical signal data are extracted from each analysis window of 200 ms after each foot contact event.Then,the Binary version of the hybrid Gray Wolf Optimization and Particle Swarm Optimization(BGWOPSO)algorithm is used to select features.And,the selected features are optimized and assigned different weights by the Biogeography-Based Optimization(BBO)algorithm.Finally,an improved K-Nearest Neighbor(KNN)classifier is employed for intention recognition.This classifier has the advantages of high accuracy,few parameters as well as low memory burden.Based on data from eight patients with transfemoral amputations,the optimization system is evaluated.The numerical results indicate that the proposed model can recognize nine daily locomotion modes(i.e.,low-,mid-,and fast-speed level-ground walking,ramp ascent/decent,stair ascent/descent,and sit/stand)by only seven features,with an accuracy of 96.66%±0.68%.As for real-time prediction on a powered knee prosthesis,the shortest prediction time is only 9.8 ms.These promising results reveal the potential of intention recognition based on the proposed system for high-level control of the prosthetic knee.

Transfer film effects induced by 3D-printed polyether-ether-ketone with excellent tribological properties for joint prosthesis

Based on the building principle of additive manufacturing,printing orientation mainly determines the tribological properties of joint prostheses.In this study,we created a polyether-ether-ketone(PEEK)joint prosthesis using fused filament fabrication and investigated the effects of printing orientation on its tribological properties using a pin-on-plate tribometer in 25% newborn calf serum.An ultrahigh molecular weight polyethylene transfer film is formed on the surface of PEEK due to the mechanical capture of wear debris by the 3D-printed groove morphology,which is significantly impacted by the printing orientation of PEEK.When the printing orientation was parallel to the sliding direction of friction,the number and size of the transfer film increased due to higher steady stress.This transfer film protected the matrix and reduced the friction coefficient and wear rate of friction pairs by 39.13%and 74.33%,respectively.Furthermore,our findings provide a novel perspective regarding the role of printing orientation in designing knee prostheses,facilitating its practical applications.

Is there sufficient evidence to support the use of antibiotic holiday just before the second stage of an infected total hip or knee arthroplasty revision surgery?

The practice of implementing an antibiotic holiday before the second stage of hip or knee arthroplasty is currently controversial due to limited evidence for this approach,as per the International Consensus Meeting 2018 on Musculoskeletal Infection.A greater understanding of this issue could augment the quality of Alrayes and Sukeik’s mini-review(2023)on diagnosing,managing,and treating periprosthetic knee infections.However,a significant lack of literature exists concerning the optimal duration for the antibiotic holiday,calling for more research before establishing any clinical guidelines.

Review of Recent Progress in Robotic Knee Prosthesis Related Techniques:Structure,Actuation and Control

As the essential technology of human-robotics interactive wearable devices,the robotic knee prosthesis can provide above-knee amputations with functional knee compensations to realize their physical and psychological social regression.With the development of mechanical and mechatronic science and technology,the fully active knee prosthesis that can provide subjects with actuating torques has demonstrated a better wearing performance in slope walking and stair ascent when compared with the passive and the semi-active ones.Additionally,with intelligent human-robotics control strategies and algorithms,the wearing effect of the knee prosthesis has been greatly enhanced in terms of stance stability and swing mobility.Therefore,to help readers to obtain an overview of recent progress in robotic knee prosthesis,this paper systematically categorized knee prostheses according to their integrated functions and introduced related research in the past ten years(2010−2020)regarding(1)mechanical design,including uniaxial,four-bar,and multi-bar knee structures,(2)actuating technology,including rigid and elastic actuation,and(3)control method,including mode identification,motion prediction,and automatic control.Quantitative and qualitative analysis and comparison of robotic knee prosthesis-related techniques are conducted.The development trends are concluded as follows:(1)bionic and lightweight structures with better mechanical performance,(2)bionic elastic actuation with energy-saving effect,(3)artificial intelligence-based bionic prosthetic control.Besides,challenges and innovative insights of customized lightweight bionic knee joint structure,highly efficient compact bionic actuation,and personalized daily multi-mode gait adaptation are also discussed in-depth to facilitate the future development of the robotic knee prosthesis.

Patient-Specific Design and Biomechanical Evaluation of a Novel Bipolar Femoral Hemi-Knee Prosthesis

While total knee replacement is successful, hemiarthroplasty is necessary for some young, obese and active patients who are especially not suitable for unicompartmental or total knee prostheses. Hemiarthroplasty also provides an opportunity for children with bone tumors. The design ofhemiarthroplasty should be patient-specific to reduce contact stress and friction as well as instability, compared to conventional hemi-knee prosthesis. A novel bipolar hemi-knee prosthesis with two flexion stages was developed according to a healthy male＇s knee morphological profile. The motion mode of the bipolar hemi-knee prosthesis was observed through roentgenoscopy in vitro experiment. The biomechanical properties in one gait cycle were evaluated though finite element simulation. The bipolar hemi-knee prosthesis was found to produce knee flexion at two stages through X-ray images. The first stage is the motion from upright posture to a specified 60~ flexion, followed by the second stage of motion subsequently to deep flexion. The finite element simulation results also show that the designed hemi-knee prosthesis has the ability to reduce stresses on the joint contact surfaces. Therefore, it is possible for the bipolar hemi-knee prosthesis to provide better biotribological performances because it can reduce stresses and potentially wear on the opposing contacting surface during a gait cycle, orovidin~ a t^romisin~ treatment strate^v in future Joint renair znd renlneement

Population-Based and Personalized Design of Total Knee Replacement Prosthesis for Additive Manufacturing Based on Chinese Anthropometric Data

At present,most total knee replacement(TKR)prostheses on the market are designed according to the sizes of Caucasians.However,extensive studies have indicated that human anatomies differ among different ethnicities.A number of reports have indicated that Chinese TKR patients do not match with available prostheses.In this study,computed tomography(CT)images of 52 knees of Chinese men and women were used for anthropometric measurements.Index and geometric measurements were definedand used for correlation analysis.Key parameters from the measurement results were identified.Detailed geometries of knees were measured as coordinates.A deformable three-dimensional(3D)knee modelbased on anatomical coordinates correlating with the identified key parameters was generated.A pros-thesis was then designed according to the analyzed results.Surface matching analysis,bone resectionanalysis,and cadaveric trials were conducted and compared with commercial products to validate theproposed design.The femoral component designed by this study resulted in the highest accuracy(rootmean square point-to-surface(RMS PS),(1.08±0.20)mm)and lowest amount of resected bone volume(27412mm^(3))in comparison with two commercial knee prostheses.This study suggests a new approachfor population-based patient-specific femoral prosthesis design With a single,easilty acquired dimen-sion-namely,epicondyle width(ECW)-as input,a patient-specific femoral prosthesis can be designed according to the analyzed measured data and manufactured by additive manufacturing(AM)methods.Meanwhile,the reconstructed femoral condylar surface was compared with the femoral condylar surfacein the original CT scanning data The average RMS PS distance of the reconstructed femoral condylar surface among all data was(1.10±0.18)mm,which is comparable to other statistical shape modeling methods using multiple radiographs as input data.There is a need to develop an anthropometric-based knee prosthesis for the Chinese population.Based on the anthropometry of the Chinese population,our new design fits Chinese patients better and reserves more bone volume compared with current commercial prostheses,which is an essential step toward AM for personalized knee prostheses.

A comparison of the short-term effects of fixed platform versus rotating high-fiexion prosthesis for the patients with osteoarthrities of knee

Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteoarthritis of

Robotic Knee Tracking Control to Mimic the Intact Human Knee Profile Based on Actor-Critic Reinforcement Learning

We address a state-of-the-art reinforcement learning(RL)control approach to automatically configure robotic pros-thesis impedance parameters to enable end-to-end,continuous locomotion intended for transfemoral amputee subjects.Specifically,our actor-critic based RL provides tracking control of a robotic knee prosthesis to mimic the intact knee profile.This is a significant advance from our previous RL based automatic tuning of prosthesis control parameters which have centered on regulation control with a designer prescribed robotic knee profile as the target.In addition to presenting the tracking control algorithm based on direct heuristic dynamic programming(dHDP),we provide a control performance guarantee including the case of constrained inputs.We show that our proposed tracking control possesses several important properties,such as weight convergence of the learning networks,Bellman(sub)optimality of the cost-to-go value function and control input,and practical stability of the human-robot system.We further provide a systematic simulation of the proposed tracking control using a realistic human-robot system simulator,the OpenSim,to emulate how the dHDP enables level ground walking,walking on different terrains and at different paces.These results show that our proposed dHDP based tracking control is not only theoretically suitable,but also practically useful.

The Knee Wear Prediction of UHMWPE Tibial Insert Using VIPRO Platform

The failure mechanism was postulated as a combination of the high level of loading during normal activities and a non-conforming contact mechanism between the femoral condyles and the tibial insert. The question that arises is： could be this phenomenon evaluated quantitatively a priori, e.g., could be the failure due to delamination wear predicted？ In order to do some finite element simulations were performed to dynamically determinate the contact area and contact pressure for three different activities. The results obtained using VIPRO platform lead to the conclusion that many clinically reported failures of the tibial tray are caused by the adhesive and fatigue wear.

Design,Testing and Control of a Magnetorheological Damper for Knee Prostheses

This study aims to develop a magnetorheological(MR)damper for semi-active knee prostheses to restore the walking ability of transfemoral amputees.The core dimensions of the MR damper were determined via theoretical magnetic field calculations,and the theoretical relationship between current and joint torque was derived through electromagnetic simulation.Then,a physical prototype of the semi-active prosthetic knee equipped with the MR damper was manufactured.Based on the data obtained from angle sensor,pressure sensor(loadcell),and inertial measurement unit(IMU)on the prosthesis,a matching control algorithm is developed.The joint torque of the MR damper can be adaptively adjusted according to the walking speed of the amputee,allowing the amputee to realize a natural gait.The effectiveness of the control program was verified by the ADAMS and MATLAB co-simulation.The results of the test and simulation show that the MR damper can provide sufficient torque needed for normal human activities.

Damage due to rolling in total knee replacement-The influence of tractive force

The femoral condyles of a knee prosthesis articulate with a combination of rolling and sliding on the tibial polyethylene plateau.Little is known about potential polyethylene damage due to rolling motion.Since rolling does not exclude the presence of tangential surface loads,this study sought to investigate the influence of tractive rolling on the wear of polyethylene.A“wheel-on-flat”apparatus,consisting of a metal wheel and a polyethylene flat,mimicked contact conditions present in total knee replacement.An increasingly tractive force under conditions of pure rolling was applied.It was found that under rolling kinematics a tangential surface load of up to 17%of the normal load could be transferred through the contact.Surface damage was dependent on the amount of tractive force and appeared more severe with higher forces.In the region of highest tractive force,wear features were identified that resembled perpendicular ridges on surfaces of retrieved tibial polyethylene devices.This suggests that tractive rolling may be a relevant wear mode in total knee replacement.

Use of mid-vastus approach in less invasive primary total knee arthroplasty

Background Total knee arthroplasties （TKR） combined with the concept of reduced trauma to tissue has been performed by many doctors. The aim of this study was to retrospectively assess the early results of a group of TKR with a mid-vastus approach, which was characterized as no patellar eversion, no disruption of suprapatellar pouch and extensor mechanism, and to compare the outcome with conventional operative techniques. Methods A total of 59 patients （67 knees） were followed. All patients received the same prosthesis of Genesis II posterior-stabilized total knees. Of them, 29 consecutive patients （34 knees） had a mid-vastus approach and were operated on with less invasive instruments and techniques. The mean follow-up duration was 11.6 months. Clinical evaluations were performed according to the Hospital for Special Surgery scores; radiographic assessment followed the guidelines of the Knee Society. Postoperative recovery of quadriceps strength and the extensor mechanism was also evaluated. Results No prosthetic loosening or anterior knee pain was found at the latest follow-up; 1 patient had a superficial infection and postoperative stiffness of the knee who undertook a debridement and manipulation several months later. The angulations of tibial osteotomy were within normal range. The average preoperative and postoperative Hospital for Special Surgery scores were 57.9 points and 86.1 points respectively. The mean postoperative range of motion was 113.5^-. Most patients regained their quadriceps strength at the third or fourth month postoperatively. Conclusions The overall early results from using the mid-vastus approach were comparable with that of using a standard approach, and the exposure did not affect the accuracy of the tibial cut. The muscle maximal contraction strenath recovered araduallv after oDeration. The aDDroach was safe and Datients of this aroup obtained satisfactorv outcomes.

Intelligent Knee Prostheses: A Systematic Review of Control Strategies

The intelligent knee prosthesis is capable of human-like bionic lower limb control through advanced control systems and artificial intelligence algorithms that will potentially minimize gait limitations for above-knee amputees and facilitate their reintegration into society.In this paper,we sum up the control strategies corresponding to the prevailing control objectives(position and impedance)of the current intelligent knee prosthesis.Although these control strategies have been successfully implemented and validated in relevant experiments,the existing deficiencies still fail to achieve optimal performance of the controllers,which complicates the definition of a standard control method.Before a mature control system can be developed,it is more important to realize the full potential for the control strategy,which requires upgrading and refining the relevant key technologies based on the existing control methods.For this reason,we discuss potential areas for improvement of the prosthetic control system based on the summarized control strategies,including intent recognition,sensor system,prosthetic evaluation,and parameter optimization algorithms,providing future directions toward optimizing control strategies for the next generation of intelligent knee prostheses.

A preliminary report of patellofemoral arthroplasty in isolated patellofemoral arthritis

Background Isolated patellofemoral osteoarthritis is not uncommon. Surgical treatment of isolated patellofemoral arthritis remains controversial and poses a challenging treatment dilemma. The present study aimed to evaluate the short-term results of patellofemoral arthroplasty for patients with isolated patellofemoral osteoarthritis.Methods We analyzed 11 patellofemoral arthroplasties performed from March 2006 to September 2009 in 11 patients with isolated patellofemoral arthritis. The patients comprised 2 males and 9 females with an average age of 53.7 years （range, 46-74 years）. Standard weightbearing radiographs were taken in the anteroposterior, lateral, and 45° axial views.The knee pain and functional status were evaluated by the Western Ontario and McMaster Universities Osteoarthritis Index （WOMAC） scales and American Knee Society （AKS） scores. For comparison, 23 total knee arthroplasties in 23 patients with primary tibiofemoral osteoarthritis were matched according to age, gender, bilaterality and body mass index.The duration of follow-up was 23.7 months （range, 12-47 months）.Results The majority of the 11 patients experienced improvement in their patellofemoral symptoms after patellofemoral arthroplasty. The WOMAC scores improved considerably by 7.4 points with respect to pain and by 5.2 points with respect to function. The AKS scores also improved considerably by 23.9 points with respect to pain and 44.3 points with respect to function. Although the clinical outcomes after patellofemoral arthroplasty were not better than those after total knee arthroplasty, patellofemoral arthroplasty exhibited advantages in the shorter operation time, lower blood loss and increased postoperative range of motion. At the latest follow-up, there was no clinical or radiographic evidence of patellofemoral maltracking, loosening or wear.Conclusions On the basis of our experience in this relatively small series of patients with a short-term follow-up,patellofemoral arthroplasty is an effective treatment alternative to total knee arthroplasty in isolated patellofemoral arthritis. MRI and arthroscopy may contribute to define those patients with isolated patellofemoral degeneration.