No difference between mobile and fixed bearing in primary total knee arthroplasty: a meta-analysis

Continuous femoral nerve block as pain management following total knee arthroplasty: a systematic review

INTRODUCTION

The present systematic review evaluated the current level of I evidence on continuous femoral nerve block (FNB) as pain management following total knee arthroplasty (TKA), comparing different drugs.

MATERIALS AND METHODS

This study followed the 2020 PRISMA guidelines. PubMed, Embase and Web of Science were accessed in November 2024. All clinical studies concerning continuous FNB for pain management following TKA were considered.

RESULTS

Data from 22 RCTs were retrieved. The drugs included in the analyses were levobupivacaine, bupivacaine and ropivacaine in isolation or combined with prilocaine or dexmedetomidine. A statistically significant difference was found in VAS at rest in postoperative day (POD) 0 (p < 0.01): the bupivacaine group demonstrated the highest values, and the ropivacaine combined with dexmedetomidine group had the lowest values. No other statistically significant difference in VAS at rest was found for any group in POD 1, 2, and 3 (p = 0.1, p = 0.1, and p = 0.4, respectively). The groups receiving ropivacaine combined with dexmedetomidine and prilocaine had the lowest values of VAS during activity in POD2 (p < 0.01), while in POD3 the groups receiving ropivacaine combined with prilocaine and the bupivacaine one had the lowest values (p < 0.01). No significant difference was found in VAS during activity between any group in POD 0 (p = 0.4) and POD 1 (p = 0.3).

CONCLUSION

Ropivacaine combined with dexmedetomidine might be the best compound for continuous femoral nerve block to manage pain following TKA during the first PODs. Further high-quality investigations are necessary to validate these findings in clinical settings.

Management of Postoperative Pain Following Primary Total Knee Arthroplasty: A Level I Evidence-Based Bayesian Network Meta-Analysis

Background: Postoperative pain management after total knee arthroplasty (TKA) is crucial for promoting early recovery. Advances in pain management techniques have significantly improved outcomes after TKA. Recently, multimodal analgesia has emerged as a key concept in pain management following TKA, using regional anaesthesia to reduce narcotic use and minimise narcotic-related side effects. This Bayesian network meta-analysis compared different treatment options for the management of postoperative pain following primary TKA. Methods: This study was conducted following the 2020 PRISMA statement. In January 2025, all randomised controlled trials (RCTs) related to postoperative pain management following TKA were accessed. Pain reported on postoperative days (PODs) 1-3 was evaluated. Results: Data from 7199 patients were retrieved. Of these, 63.2% (4232 of 6691) were women, and the mean age was 66.7 ± 3.1 years. The mean length of follow-up was 10.2 ± 18.3 weeks. At baseline, comparability was confirmed for age (p = 0.1), BMI (p = 0.8), and visual analogue scale (VAS, p = 0.1). On POD 1, single-shot SNB/three-in-one block was associated with a lower VAS, followed by continuous intra-articular analgesia/local infiltration analgesia (LIA)/posterior capsule infiltration (PCI) and continuous femoral nerve block (FNB)/intermittent SNB. On POD 2, continuous intra-articular analgesia/LIA/PCI was associated with a lower VAS, followed by continuous FNB/PCI and single-shot femoral triangle block (FTB)/single-shot infiltration between the popliteal artery and capsule of the knee (IPACK). On POD 3, continuous ACB was associated with a lower VAS, followed by continuous intra-articular analgesia/LIA/PCI and continuous FNB/PCI. Conclusions: Continuous intra-articular analgesia/LIA/PCI was associated with the best pain control following primary TKA. Multimodal analgesia, which incorporates peripheral nerve blockade and periarticular injections, has become a key concept in contemporary pain management following TKA.

Superior One-year Forgotten Joint Scores with cruciate-retaining mobile bearings versus posterior-stabilized mobile and fixed bearings in a contemporary total knee system

BACKGROUND

Total knee arthroplasty (TKA) mainly involves the femoral, tibial, and bearing implants. Bearings are categorized by posterior cruciate ligament (PCL) status (cruciate-retaining [CR] vs. posterior-stabilized [PS]) and motion (mobile vs. fixed). This study assessed the impact of three bearing combinations (CR Mobile, PS Mobile, and PS Fixed) on one-year patient-reported outcome measures (PROMs) following TKA.

METHODS

In this retrospective analysis of 486 TKAs using the same prosthesis with varied bearings, patients were grouped as CR Mobile, PS Mobile, and PS Fixed. Patient characteristics, preoperative, and one-year postoperative PROMs (Forgotten Joint Scores [FJS] and Knee Society Scores [KSS], and Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]), were collected. Multivariate analysis was conducted to assess the impact of bearing type on one-year PROMs.

RESULTS

The multivariate regression model showed that bearing type significantly impacted the one-year FJS, with CR Mobile showing higher scores than PS Mobile and PS Fixed bearings (p < 0.001). However, bearing type did not significantly influence one-year KSS and WOMAC scores (all p > 0.05).

CONCLUSION

This study was the first to analyze the impact of the combination of PCL status and bearing motion in TKA. Bearing type selection had an impact on the one-year postoperative FJS, particularly favoring CR Mobile bearings. Other PROMs were not affected by the choice of bearing type.

Minimum twenty-year follow-up of fixed-vs mobile-bearing total knee arthroplasty: Double blinded randomized trial

Introduction

Mobile-bearing (MB) inserts, designed to minimize aseptic loosening and to reduce contact stresses leading to polyethylene wear, are an alternative to fixed-bearing (FB) inserts. Most studies have shown no significant difference between MB and FB constructs, and there is limited long-term data comparing the two constructs [1,2,3,4]. The purpose of this study was to report the outcomes of a randomized controlled trial comparing MB versus FB inserts on patients with minimum 20-year follow-up.

Methods

Between 2002 and 2003, 132 patients were randomized intra-operatively to the rotating-platform (RP) prosthesis group or the FB prosthesis group. 40 patients from the previous minimum 12-year follow-up were evaluated to obtain information on implant survival and satisfaction. Basic univariate statistics were used.

Results

26 patients were deceased, and 4 patients were lost to follow-up. This left 10 remaining knees (FB = 5, RP = 5) for inclusion. The mean age at surgery was 56.8 years, and the mean follow-up was 21 years overall for both groups. There were four failures and two revisions in total for each group 12. The RP revisions were for patellar component loosening and deep infections. The revisions on FB knees were for patella fracture and dislocation, pain from an oversized femoral component, and a loose tibial baseplate. The remaining patients expressed satisfaction with their replaced knees. No additional revisions were reported in this follow-up study. With the numbers available for study, there was no difference in ROM at 122° ± 12.5° for RP knees and 119° ± 6.5° for FB knees (p = 0.92).

Conclusions

There were few revisions, and most patients, in both RP and FB groups, expressed satisfaction and limited wear with their knees. While a safe, viable option for TKA, RP inserts did not result in long-term clinical benefit compared to FB.

[Digital tools in primary total knee arthroplasty-Prevalence in the German-speaking region]

BACKGROUND

Digital tools are being increasingly used worldwide in primary knee arthroplasty. This study aimed to analyze the utilization density of digital tools, the preferred alignment strategies, and the obstacles and benefits of implementing these technologies in German-speaking countries.

MATERIALS AND METHODS

An online survey with 57 questions about digital tools in primary knee arthroplasty and their usage was conducted among members of the Arthroplasty Working Group (AE). The survey included questions on navigation, robotics, patient-specific instruments, individualized implants, and augmented reality.

RESULTS

The survey revealed that 18% of hospitals use navigation and 17% use robotic systems in primary total knee arthroplasty surgery. The main reasons for not implementing supportive technologies were high acquisition and ongoing costs, as well as longer surgical duration. Patient-specific instruments and individualized implants currently play a minor role. Patient-specific alignment strategies, such as kinematic (navigation: 35%; robotics: 44%) and functional alignment (navigation: 15%; robotics: 35%), are preferred in this context. With conventional instrumentation predominantly mechanical alignment was applied (79%).

DISCUSSION

The results indicate a relatively high utilization density of digital tools, which are mainly used to perform personalized alignment strategies in primary knee arthroplasty in German-speaking countries. This was particularly evident in high-volume hospitals. Economic aspects were the main reasons for not using these technologies. Future developments should aim to simplify the systems and thus achieve improved cost efficiency.

Mobile bearing total knee arthroplasty does not lead to better joint awareness compared to fixed bearing design: A systematic review and meta-analysis

Purpose

Mobile-bearing total knee arthroplasty (MB-TKA) and fixed-bearing (FB) TKA are both widely used, with MB-TKA theoretically offering better functional outcomes due to its natural kinematics. This systematic review and meta-analysis aimed to compare joint awareness between MB-TKA and FB-TKA, as measured by Forgotten Joint Score-12 (FJS-12), to provide insights into patient-perceived outcomes.

Methods

A comprehensive literature search was conducted across major databases following PRISMA guidelines, without date or language restrictions. Studies focusing on TKA with MB or FB as the intervention and control groups, respectively, and reporting on FJS-12 were included. The selection process involved two independent reviewers. Data extraction was carried out using a structured checklist and assessed for quality using the Newcastle-Ottawa Scale (NOS). The meta-analysis employed Hedge's g method to compare FJS-12 and assessed publication bias using Egger's test and funnel plot analyses.

Results

Six studies, including two randomized clinical trials and four cohort studies with 731 participants and mean follow-up of 5.4 years, met the inclusion criteria. The meta-analysis revealed no significant difference in FJS-12 between MB and FB TKA (pooled difference = 0.132, 95% confidence interval: -0.103 to 0.367, p = 0.271), with moderate heterogeneity observed (I 2 = 53.5%). Publication bias assessment indicated no significant bias. Meta-regression did not identify factors contributing to heterogeneity.

Conclusion

MB-TKA does not provide superior patient-perceived outcomes in terms of joint awareness compared to FB-TKA. This suggests that the clinical advantage of MB-TKA in terms of joint awareness is likely negligible. Therefore, the choice between MB and FB TKA should be based on other considerations, such as surgeon preference, implant cost and individual patient needs.

Level of Evidence

Level III.

Fixed-Bearing and Higher Postoperative Knee Flexion Angle as Predictors of Satisfaction in Asian Patients Undergoing Posterior-Stabilized Total Knee Arthroplasty

Background

Patient-reported satisfaction following total knee arthroplasty (TKA) can be affected by various factors. This study aimed to assess patient satisfaction rates and identify factors related to patients, surgery, and postoperative knee motion associated with satisfaction in posterior-stabilized TKA among Asian patients.

Methods

A retrospective cross-sectional study was conducted in patients with primary osteoarthritis who underwent TKA and had a follow-up period of over 2 years. Patient satisfaction was measured using a 5-point Likert scale, and the patients were divided into satisfied and dissatisfied groups. The factors potentially affecting satisfaction were collected, including demographics, comorbidities, surgical options, and knee motion. Univariate and multivariate regression analyses were performed.

Results

Of the 858 patients included, 784 (91.4%) were satisfied and 74 (8.6%) were dissatisfied. Fixed-bearing implants and higher postoperative knee flexion angles were associated with satisfaction (odds ratio [OR], 2.366; p = 0.001 and OR, 1.045; p < 0.001, respectively), whereas cerebrovascular disease was related to dissatisfaction (OR, 0.403; p = 0.005). The regression model demonstrated moderate predictability (R 2 = 0.112).

Conclusions

Fixed-bearing implants and higher postoperative knee flexion angles were associated with patient satisfaction following TKA, whereas cerebrovascular disease was associated with dissatisfaction. The identification of these factors could help improve surgical outcomes and patient satisfaction following TKA.

Reliability and validity of patient-reported outcome measures in assessing knee osteoarthritis in the Chinese population: A systematic review

Objective

Knee osteoarthritis (KOA) is a prevalent condition in China, necessitating effective assessment tools for treatment outcomes. This study systematically reviews and analyzes the reliability, validity, and selection of patient-reported outcome measures (PROMs) for evaluating KOA.

Methods

Following PRISMA guidelines, a literature search was conducted across seven databases, including CNKI, PubMed, and Embase, covering publications from December 2012 to December 2022. The methodological quality of the studies was assessed using the COSMIN checklist.

Results

Twenty-one studies met the inclusion criteria, involving eight types of KOA PROMs. The Oxford Knee Score (OKS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were the most frequently utilized, appearing in nine and four studies, respectively. OKS achieved a "strong" rating in internal consistency, test-retest reliability, content validity, responsiveness, and measurement error, while WOMAC received a "strong" rating in internal consistency, test-retest reliability, and content validity, with a "moderate" rating in structural validity.

Conclusion

Both OKS and WOMAC are effective PROMs for evaluating KOA in China. However, the choice of a specific tool should be based on the study's objectives and the practical context, considering each tool's reliability, validity, and other measurement properties.

[Research progress on unicompartmental knee arthroplasty for elderly patients with knee osteoarthritis]

Objective

To conclude the research progress of unicompartmental knee arthroplasty (UKA) in the treatment of elderly patients with knee osteoarthritis (KOA).

Methods

The literature on UKA at home and abroad in recent years was reviewed to summarize the clinical characteristics of elderly patients with KOA, perioperative management (including evaluating indications preoperatively, intraoperative prosthesis selection, postoperative complication management, etc).

Results

Through reasonable preoperative evaluation, prosthesis selection, and advanced perioperative management, for elderly patients with KOA who meet the indications, UKA can be considered. Compared with total knee arthroplasty, the incidence of postoperative complications in elderly patients undergoing UKA is lower, joint awareness is reduced, functional improvement and satisfaction are higher. Meanwhile, choosing appropriate prostheses and fixation methods can lead to a good survival rate.

Conclusion

UKA can provide a safe and effective treatment option for elderly patients with KOA within a certain range of indications.

Factors influencing periprosthetic bone mineral density in total knee arthroplasty: a systematic review

INTRODUCTION

Following total knee arthroplasty (TKA), there is a significant decline in periprosthetic bone mineral density (BMD), potentially resulting in complications such as prosthetic loosening, periprosthetic fracture, and influencing the postoperative recovery. The objective of this study was to summarize the factors influencing periprosthetic BMD in TKA from existing studies.

METHODS

A comprehensive systematic search was performed in 4 databases: Pubmed, Embase, Web of Science, and Cochrane Library. The last search was carried out on October 12, 2023. We used the keywords ''total knee arthroplasty'', ''bone mineral density'' and each of them combined with ''tibia'' and ''femur'' to identify all relevant articles reporting about potential impact factors influencing the periprosthetic BMD in patients after TKA.

RESULTS

Out of 1391 articles, 22 published from 2001 to 2023 were included in this systematic review. Following eligibility screening, six significant categories affecting periprosthetic BMD were recognized: prosthesis type, design of stem, coating, body weight, cement, and peg distance.

CONCLUSION

Mobile-bearing prostheses, modular polyethylene design, short stems, cruciform stems, avoidance of bone cement, higher body mass index, titanium nitride coating, and a smaller medial peg distance could potentially benefit periprosthetic BMD. Comprehensive consideration of diverse factors influencing periprosthetic BMD before surgery and collaboration with post-operative drug therapy are essential.

TRIAL REGISTRY

The PROSPERO registration number is CRD42023472030.

Comparison of revision rates and epidemiological data of a single total knee arthroplasty system of different designs (cruciate retaining, posterior stabilized, mobile bearing, and fixed bearing): a meta-analysis and systematic review of clinical trials and national arthroplasty registries

BACKGROUND

This study aimed to meta-analyze epidemiological data, revision rates, and incidences of different designs of a single Total Knee Arthroplasty System and compare these factors across different countries.

METHODS

A systematic review was conducted on clinical studies and arthroplasty registries of ATTUNE TKA from 1999 to 2020. The main endpoints analyzed were revision rates and epidemiological data.

RESULTS

The average age of patients was 67.8 years, with a gender distribution of 60% female and 40% male. The pooled average BMI was 29.4 kg/m2. Eight clinical studies showed a pooled revision rate per 100 observed CY of 0.5 (n = 1343 cases). Cumulative revision rates after 1, 3, and 5 years varied among registries, with the Swiss registry having the highest revision data (after 5 years: 6.3%) and the American registry having the lowest revision data (after 5 years: 1.7%). A comparison of the revision rates of mobile bearing and fixed bearing (41,200 cases) as well as cruciate retaining and posterior stabilized (n = 123,361 cases) showed no significant advantage in the first 5 years after implantation.

CONCLUSION

In conclusion, pooled data from 41,200 cases of TKA with a single Total Knee Arthroplasty System in two arthroplasty registries revealed that there was no significant difference in revision rates between the mobile bearing and fixed bearing design within the first 5 years after implantation. In addition, a comparison of the revision rates in n = 123,361 cases showed no significant advantage for cruciate retaining or posterior stabilized in the first 5 years after implantation.

Comparison of bilateral cementless total knee arthroplasty results between patients in different BMI groups

INTRODUCTION

The aim of this study was to compare the results of cementless bilateral total knee arthroplasty (TKA) between individuals in different obesity groups.

MATERIALS AND METHODS

This was a retrospective cohort study. Patients with a body mass index (BMI) greater than 25 who underwent bilateral TKA for gonarthrosis between 2014 and 2020 and completed a minimum follow-up of 24 months were included. Age, sex, height, weight, BMI, operation time, length of stay, patient satisfaction, knee scores and complications were compared. Patients with missing data, who were followed for less than 24 months or had postoperative fractures around the knee were excluded.

RESULTS

There was a significant difference between the groups in terms of operation time (Class III > overweight > Class II > Class I p < 0.001). There was a significant difference in complications between the groups (Class III > Class I > Class II > overweight p = 0.010). According to our pairwise comparison, complications were more common in the class III group than in the overweight group. Knee score (KS) and function score (FS) increased significantly after surgery in all groups (p < 0.001), with no difference in FS (p = 0.448). Knee score changes were greater in the overweight and class I groups (p < 0.001). There was a significant interaction between both KS and FS and person satisfaction (p < 0.001).

CONCLUSION

Cementless TKA improved KS and FS in all obesity groups, yielded high patient satisfaction. Although the incidence of complications was higher in the morbidly obese patients than in the overweight patients, the difference was not significant. Patients with morbid obesity should be informed about related risks before planning cementless TKA.

Functional alignment in robotic-assisted total knee arthroplasty: a systematic review

PURPOSE

The present study systematically reviewed current evidence on functional alignment (FA) in robotic total knee arthroplasty (TKA), discussing advantages and limitations, possible pitfalls, and prospects.

METHODS

This study was conducted according to the 2020 PRISMA statement. In August 2023, the following databases were accessed: PubMed, Web of Science, Google Scholar, and Embase with no additional filters or time constraints. All the clinical studies investigating functional alignment in robotic TKA were accessed. Only studies published in peer-reviewed journals were considered. The risk of bias was evaluated following the guidelines in the Cochrane Handbook for Systematic Reviews of Interventions. Non-randomized controlled trials (non-RCTs) were evaluated using the Risk of Bias in Nonrandomised Studies of Interventions (NRSI) (ROBINS-I) tool.

RESULTS

Data from 1198 patients (seven studies) were retrieved. The mean length of the follow-up was 17.1 ± 6.4 months. The mean age was 67.2 ± 5.4 years, and the mean BMI was 30.9 ± 2.7 kg/m2.

CONCLUSION

FA might improve resection accuracy, implant alignment, and gap balancing in TKA, and additional high-quality clinical trials are necessary to properly establish the superiority of FA to other alignment techniques in TKA. Long-term clinical trials are needed to investigate the impact of FA on implant survivorship.

LEVEL OF EVIDENCE

Level IV, systematic review and meta-analysis.

No differences in long-term clinical outcomes and survival rate of navigation-assisted versus conventional primary mobile-bearing total knee arthroplasty: A minimum 10-year follow-up

PURPOSE

This study aimed to compare long-term clinical and radiographic outcomes and survival rates between navigation-assisted (NAV) total knee arthroplasty (TKA) and conventional (CON) TKA using a mobile-bearing insert.

METHODS

From May 2008 to December 2009, 45 and 63 mobile-bearing TKA patients were enroled in the CON- and NAV-TKA groups with 146.8 months follow-up, respectively. Clinical outcomes (Western Ontario and McMaster University Osteoarthritis Index and Knee Society Scores), radiographic outcomes (hip-knee-ankle [HKA], lateral distal femoral, medial proximal tibial, γ, and δ angles), and survivorship were compared between both groups.

RESULTS

The number of HKA angle outliers (more than 3 degrees or less than -3 degree) was significantly lower in the NAV-TKA group (24.4% vs. 9.5%, p = 0.036) than in the CON-TKA group. However, long-term clinical outcomes were similar between both groups. The cumulative survival rate (best-case scenario) was 98.3% in the CON-TKA group and 97.5% in the NAV-TKA group, with no significant difference between the groups (p = 0.883).

CONCLUSION

Long-term clinical outcomes and survival rates were similar between the two groups despite fewer outliers of postoperative lower-limb alignment in the NAV-TKA group. Excellent survival rates were observed in both groups using mobile-bearing inserts.

LEVEL OF EVIDENCE

Level IV, case series.

Less wear in deep-dished mobile compared to fixed bearing total knee arthroplasty of the same design at 5-year follow-up: a randomised controlled model-based Roentgen stereophotogrammetric analysis trial

PURPOSE

The aim of this prospective randomised controlled study was to compare wear characteristics and functional outcome between deep-dished mobile bearing (MB) and fixed bearing (FB) cemented total knee arthroplasty (TKA). We hypothesised that deep-dished MB reduces polyethylene wear and improves patient-reported outcome measures.

METHODS

A total of 50 patients were randomised to receive a MB or FB tibia component of the same cemented TKA design. Patients were evaluated over a 5-year follow-up period. Medial and lateral wear were assessed using model-based Roentgen Stereophotogrammetric Analysis (RSA) and compared with the direct postoperative minimal joint space measurement. Functional outcome was assessed by the clinician-derived KSS and OKS, WOMAC, LEAS, and FJS-12. All data were derived using a general linear mixed model.

RESULTS

At 5-year follow-up, decreased wear in the MB compared to the FB group was observed on the lateral side (0.07 ± 0.17 mm, p = 0.026), but not on the medial side (0.31 ± 0.055 mm, p = 0.665). Functional outcomes improved with a statistical significant effect over time, with no significant differences between groups (all p > 0.17).

CONCLUSION

This model-based RSA study with 5-year follow-up showed that cemented deep-dished MB reduced lateral polyethylene wear as compared to FB in a single TKA system, whilst clinical outcomes were comparable. Longer follow-up is needed to establish clinical implications of these altered wear patterns and determine type of wear.

LEVEL OF EVIDENCE

Level 1 randomised controlled trial.

Lateral joint tightness in flexion following cementless mobile-bearing total knee arthroplasty decreases patient-reported outcome measures and postoperative range of motion

PURPOSE

The purpose of this study was to clarify the association between clinical outcomes and the flexion joint gap following rotating concave-convex (Vanguard ROCC) total knee arthroplasty (TKA).

METHODS

This consecutive retrospective series included 55 knees that underwent ROCC TKA. All the surgical procedures were performed using a spacer-based gap-balancing technique. To evaluate the medial and lateral flexion gaps, axial radiographs of the distal femur were obtained using the epicondylar view with a distraction force to the lower leg at 6 months postoperatively. Lateral joint tightness was defined as the lateral gap being greater than the medial gap. To evaluate clinical outcomes, patients were asked to complete patient-reported outcome measures (PROMs) questionnaires preoperatively and during at least 1 year of follow-up postoperatively.

RESULTS

The median follow-up duration was 24.0 months. Overall, 16.0% of patients had postoperative lateral joint tightness in flexion. The postoperative range of motion and PROMs were lower in patients with lateral joint tightness than in those with a balanced flexion gap or lateral joint laxity. No serious complications, including bearing dislocations, occurred during the observation period.

CONCLUSION

Lateral joint tightness in flexion following ROCC TKA decreases PROMs and postoperative range of motion.

LEVEL OF EVIDENCE: 4

Mechanical complications after total knee arthroplasty

INTRODUCTION

With the increasing demand for total knee arthroplasty (TKA) and the burden of revision TKA on the healthcare system, as well as the quality of life implications for patients, it is extremely important for surgeons to be able to anticipate and prevent TKA mechanical complications. Surgeons must be familiar with the different causes and mechanisms of TKA complications so that they can properly treat patients with failed TKAs and better avoid these complications.

AREAS COVERED

This review addresses TKA mechanical complications and provides context for the topic. A detailed review of surgical factors, implant factors, and patient factors that contribute to mechanical complications after TKA is provided. All of the literature cited in this review was gathered from the PubMed online database using different keywords based on the section of the manuscript.

EXPERT OPINION

As surgeons and engineers solve certain issues in TKA, new challenges will inevitably arise. We must continue to push forward and innovate from both a surgical technique and implant design perspective.

BioMAT: An Open-Source Biomechanics Multi-Activity Transformer for Joint Kinematic Predictions Using Wearable Sensors

Through wearable sensors and deep learning techniques, biomechanical analysis can reach beyond the lab for clinical and sporting applications. Transformers, a class of recent deep learning models, have become widely used in state-of-the-art artificial intelligence research due to their superior performance in various natural language processing and computer vision tasks. The performance of transformer models has not yet been investigated in biomechanics applications. In this study, we introduce a Biomechanical Multi-activity Transformer-based model, BioMAT, for the estimation of joint kinematics from streaming signals of multiple inertia measurement units (IMUs) using a publicly available dataset. This dataset includes IMU signals and the corresponding sagittal plane kinematics of the hip, knee, and ankle joints during multiple activities of daily living. We evaluated the model's performance and generalizability and compared it against a convolutional neural network long short-term model, a bidirectional long short-term model, and multi-linear regression across different ambulation tasks including level ground walking (LW), ramp ascent (RA), ramp descent (RD), stair ascent (SA), and stair descent (SD). To investigate the effect of different activity datasets on prediction accuracy, we compared the performance of a universal model trained on all activities against task-specific models trained on individual tasks. When the models were tested on three unseen subjects' data, BioMAT outperformed the benchmark models with an average root mean square error (RMSE) of 5.5 ± 0.5°, and normalized RMSE of 6.8 ± 0.3° across all three joints and all activities. A unified BioMAT model demonstrated superior performance compared to individual task-specific models across four of five activities. The RMSE values from the universal model for LW, RA, RD, SA, and SD activities were 5.0 ± 1.5°, 6.2 ± 1.1°, 5.8 ± 1.1°, 5.3 ± 1.6°, and 5.2 ± 0.7° while these values for task-specific models were, 5.3 ± 2.1°, 6.7 ± 2.0°, 6.9 ± 2.2°, 4.9 ± 1.4°, and 5.6 ± 1.3°, respectively. Overall, BioMAT accurately estimated joint kinematics relative to previous machine learning algorithms across different activities directly from the sequence of IMUs signals instead of time-normalized gait cycle data.