Clinical outcomes of kinematic alignment versus mechanical alignment in total knee arthroplasty: a systematic review

A retrospective comparison of mechanically vs. kinematically aligned unicompartmental knee arthroplasties

Background

Unicompartmental Knee Arthroplasties (UKAs) treat unicompartmental arthritic degeneration. Traditionally, they are placed in a mechanical alignment with bone cuts perpendicular to the leg's mechanical axis. Kinematic alignment, an alternative, considers the patient's pre-arthritic alignment.

Methods

A retrospective study at Medstar Washington Hospital Center from 2015 to 2022 identified 72 UKA patients. Among them, 53 had mechanical alignments, and 20 had kinematic alignments. Using the Forgotten Joint Score (FJS) and Oxford Knee Score (OKS), Patient Reported Outcome Measures for these surgeries were recorded. Individuals were additionally analyzed post-surgically for Coronal Plane Alignment of the Knee (CPAK). Analysis was performed within the post-operative joint imaging, where mechanical medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) were measured. The arithmetic hip knee ankle angle (aHKA) and joint line obliquity (JLO) were calculated according to the results of MPTA-LDFA and MPTA + LDFA respectively and grouped in accordance with the CPAK classification.

Results

Overall, there was a statistically significant response rate of 51% (>50%). According to the FJS, the mechanical cohort averaged a score of 39.1 (±33.8), while the kinematical cohort averaged 56.5 (±35.2). A two-sample t-test of this data demonstrated a statistically insignificant p-value of 0.1537. According to the OKS, the mechanical cohort averaged a score of 29.1 (±10) and the kinematical cohort averaged 38.4 (±8). A two-sample t-test of this data demonstrated a statistically significant p-value of <0.001. Of note, 7 patients had to undergo revisions in the mechanical alignment cohort compared to 0 in the kinematic alignment cohort due to aseptic loosening.

Conclusion

This study demonstrates the potential benefit in patient outcomes for individuals who undergo a kinematic rather than mechanical alignment of their UKAs. The results of the CPAK data with the significance of LDFA are consistent with the goals of the mechanical and kinematic alignment respectively.

Methods of alignment in total knee arthroplasty, systematic review

Introduction

Although total knee arthroplasty (TKA) is a very frequent surgery, one in five patients is not completely satisfied. Mechanical alignment (MA) is the most popular technique for implanting TKA. However, to improve clinical outcomes, new techniques that aim to rebuild the native alignment of the knee have been developed.

Objective

The aim of this study is to perform a systematic review of the available clinical trials and observational studies comparing clinical and radiological outcomes of different methods of alignment (kinematic, anatomic, functional) to MA.

Methods

A systematic review is performed comparing results of patient reported outcome measures (PROMs) questionnaires (WOMAC, OKS, KSS, KOOS, FJS), radiological angles (HKA, mLDFA, MPTA, JLOA, femoral rotation and tibial slope) and range of motion (ROM).

Results

Kinematic and functional alignment show a slight tendency to obtain better PROMs compared to mechanical alignment. Complication rates were not significantly different between groups. Nevertheless, these results are not consistent in every study. Anatomic alignment showed no significant differences compared to mechanical alignment.

Conclusion

Kinematic alignment is an equal or slightly better alternative than mechanical alignment for patients included in this study. However, the difference between methods does not seem to be enough to explain the high percentage of dissatisfied patients. Studies implementing lax inclusion and exclusion criteria would be needed to resemble conditions of patients assisted in daily surgical practice. It would be interesting to study patient's knee phenotypes, to notice if any method of alignment is significantly better for any constitutional deviation.

Navigating the Divide: A Comprehensive Review of the Mechanical and Anatomical Axis Approaches in Total Knee Replacement

This comprehensive review explores the mechanical and anatomical axis approaches in total knee replacement (TKR) surgery, addressing the ongoing debate within the orthopedic community. Emphasizing the significance of TKR in alleviating knee-related disorders, this review underscores the pivotal role of accurate alignment in achieving optimal surgical outcomes. The purpose is to navigate the divide between the well-established mechanical axis approach, focusing on a straight-line alignment, and the anatomical axis approach, aligning with natural knee landmarks. The analysis delves into the advantages, disadvantages, and clinical implications of each approach, offering a nuanced perspective on their efficacy. The conclusion emphasizes a patient-centric approach, recommending the adoption of hybrid strategies and the incorporation of emerging technologies for enhanced precision. The future of TKR aligns with personalized medicine, leveraging advancements in computer-assisted navigation, robotics, and patient-specific implants. Ongoing professional development and interdisciplinary collaboration are crucial for surgeons, and as the field evolves, innovations in artificial intelligence, imaging, and 3D printing are expected to shape the trajectory of TKR alignment approaches.

Which method for femoral component sizing when performing kinematic alignment TKA? An in silico study

INTRODUCTION

The kinematically alignment (KA) technique for TKA aims to reproduce the pre-arthritic knee anatomy, including both the femoro-tibial and femoro-patellar joints. An in silico study was conducted to compare 3 different femoral component sizing techniques to identify the anatomical landmark which allows closest restoration of the native trochlear anatomy. Our study's question was: what was the best method for sizing the femoral component when performing KA-TKA? It was hypothesized that sizing the femoral component by aiming to restore the groove height would be the best method to restore the native trochlear anatomy.

METHODS

GMK sphere® (Medacta) femoral component 3D models were virtually kinematically aligned on 30 tri-dimensional (3D) bony osteoarthritis knee models. The femoral component was mediolaterally positioned to match distal native and prosthetic grooves. Three methods were used to size the femoral component: a conventional method with the anterior femoral cut flush to the femoral cortex (C-KATKA) and two alternative personalized methods aiming to recreate either the medial facet's height (ATM-KATKA) or the groove's height (ATG-KATKA). In-house analysis software was used to compare native and prosthetic trochlear articular surfaces and mediolateral implant overhangs.

RESULTS

Compared with the C-KATKA, ATG-KATKA and ATM-KATKA techniques increased the component size by a mean of 0.90 (SD 0.31, min 0.5 to max 1.5) (p<0.001) and 1.02 (SD 0.31, min 0.5 to max 1.5) (p<0.001), respectively. C-KATKA technique substantially proximally understuffed the trochleae with maximum values of 7.11mm (SD 1.39, min 3.93mm to max 10.57mm) in the medial facet, 4.72mm (SD 1.27, min 1.46mm to max 6.86mm) in the lateral facet and 4.51mm (SD 1.40, min 1.92mm to max 7.30mm) in the groove, respectively. Alternative techniques understuffed medial facet with maximum values of 5.07mm (SD 1.29, min 2.83mm to max 8.34mm) and 4.70mm (SD 1.52, min 0.83mm to max 8.04mm) for ATG-KATKA and ATM-KATKA techniques, respectively. There was no significant understuffing of the groove or lateral facet for alternative techniques (ATM and ATG). The ATM-KATKA and ATG-KATKA techniques generated mediolateral implant overhang, mainly postero-lateral, with a rate of 90.0% and 86.7%, respectively. In this study, no mediolateral implant overhang was found for C-KATKA.

DISCUSSION/CONCLUSION

The C-KATKA technique substantially understuffs the native trochlear articular surfaces in medial, lateral and groove parts. Alternative techniques (ATM-KATKA and ATG-KATKA) for sizing the femoral component better restore the native trochlear anatomy but also generate a high rate of postero-lateral implant overhangs. Would this postero-lateral implant overhang be clinically deleterious remains unknown? The aspect ratio of contemporary femoral TKA implants can probably be optimized to allow a better anatomical restoration of the anterior femoral compartment.

LEVEL OF EVIDENCE

II, in silico study.

Large multiplanar changes to native alignment have no apparent impact on clinical outcomes following total knee arthroplasty

PURPOSE

This study sought to examine if achieved postoperative alignment when compared to the native anatomy would lead to a difference in Patient Reported Outcome Measures (PROMs), and whether the achieved alignment could be broadly categorised by an accepted alignment strategy.

METHODS

A retrospective cohort study of prospectively collected data on patients undergoing single primary or bilateral simultaneous total knee arthroplasty (TKA) was carried out. CT scans were used to determine the mean change ("delta values") between the pre and postoperative; hip-knee-ankle angle, lateral distal femoral angle, medial proximal tibial angle and femoral implant rotation. Femoral implant flexion and tibial implant slope were measured postoperatively. The primary outcome was the relationship of the variables to the change in KOOS pain subscale after one year. The secondary outcome was the number of knees which could be categorised postoperatively to an alignment strategy, and the mean PROMs in each cohort.

RESULTS

A total of 296 knees in 261 patients were available for analysis. With regards to the primary outcome, the delta values for each variable did not demonstrate any association with the change in knee injury and osteoarthritis outcome score (KOOS) pain score. Approximately 46% of knees could not be categorised to an alignment strategy based on postoperatively measured alignment, with no significant difference between each cohort with regards to the change in KOOS Pain score.

CONCLUSION

Achieved alignment does not consistently match accepted alignment strategies, and appears to confer no benefit to clinical outcomes when the native anatomy is most closely approximated, nor results in poorer outcomes in outliers. This study highlights the importance of routine three dimensional pre and postoperative imaging in clinical practice and for the valid analysis of outcomes in studies on alignment.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Simultaneous Evaluation of Tibiofemoral and Patellofemoral Mechanics in Total Knee Arthroplasty: A Combined Experimental and Computational Approach

Contemporary total knee arthroplasty (TKA) has not fully restored natural patellofemoral (P-F) mechanics across the patient population. Previous experimental simulations have been limited in their ability to create dynamic, unconstrained, muscle-driven P-F articulation while simultaneously controlling tibiofemoral (T-F) contact mechanics. The purpose of this study was to develop a novel experimental simulation and validate a corresponding finite element model to evaluate T-F and P-F mechanics. A commercially available wear simulator was retrofitted with custom fixturing to evaluate whole-knee TKA mechanics with varying patella heights during a simulated deep knee bend. A corresponding dynamic finite element model was developed to validate kinematic and kinetic predictions against experimental measurements. Patella alta reduced P-F reaction forces in early and midflexion, corresponding with an increase in T-F forces that indicated an increase in extensor mechanism efficiency. Due to reduced wrapping of the extensor mechanism in deeper flexion for the alta condition, peak P-F forces in flexion increased from 101% to 135% of the applied quadriceps load for the baja and alta conditions, respectively. Strong agreement was observed between the experiment and model predictions with root-mean-square errors (RMSE) for P-F kinematics ranging from 0.8 deg to 3.3 deg and 0.7 mm to 1.4 mm. RMSE for P-F forces ranged from 7.4 N to 53.6 N. By simultaneously controlling dynamic, physiological loading of the T-F and P-F joint, this novel experimental simulation and validated model will be a valuable tool for investigation of future TKA designs and surgical techniques.

Accuracy of Conventional Instrumentation is Dependent on Alignment Philosophy Using the Identical Surgical Technique in Total Knee Arthroplasty

The objective of this prospective study was to assess the precision of restoring the anatomical tibial obliquity, as measured by the medial proximal tibial angle (MPTA) on conventional X-rays, in relation to the surgical technique employed. Specifically, the study aimed to compare the accuracy of tibial obliquity restoration between kinematic alignment (KA) and conventional mechanical alignment (MA) in total knee arthroplasty (TKA). Two-hundred-and-sixty patients underwent either mechanically aligned TKA (n = 139) or kinematically aligned TKA (n = 121) using conventional instrumentation (CI). Pre- and postoperative X-rays were measured twice by two observers, with a 2-week interval. Inter- and intraclass correlations were calculated, and postoperative tibial obliquity was compared to the preoperative anatomy. In the group of 139 patients with mechanically aligned TKA, no cases with an MPTA deviation greater than 1 degree from 90 degrees were observed. Sixteen percent of the cases (n = 22) had a deviation of 0 to 1 degree. The remaining 84% of the cases (n = 117) had their MPTA of 90 degrees achieved. In the group of 121 patients with kinematically aligned TKA, no cases had a deviation greater than 1 degree compared with the preoperative MPTA. Thirty-one percent of the cases (n = 37) had a deviation of 0 to 1 degree with respect to preoperative MPTA. The remaining 69% of the cases (n = 84) had their tibial obliquity restored. Mechanically aligned TKA revealed statistically significant smaller deviations of accuracy compared to kinematically aligned TKA (p = 0.005). The inter- and intraclass correlations indicated substantial agreement of all measurements (intraclass correlation coefficient [ICC] < 0.90). Both mechanically aligned and kinematically aligned TKA demonstrated satisfactory outcomes in terms of restoring tibial obliquity or a neutral MPTA of 90 degrees using CI. However, MA showed superior results regarding precision compared to KA. When starting with kinematical alignment using CI, the surgeons should be aware that the learning curve according to accuracy differs to MA. It was a Prospective Level II study.

Restricted kinematic alignment is clinically non-inferior to mechanical alignment in the short and mid-term: A systematic review

BACKGROUND

In recent years, kinematic alignment (KA) is becoming a valid alternative to mechanical alignment (MA) in total knee arthroplasty (TKA). However, to avoid early failures, the restricted kinematic alignment (rKA) approach has been developed to restore native knee kinematics without reproducing extreme knee phenotype. This systematic review aims to evaluate clinical and radiological outcomes between rKA and MA for TKA.

METHODS

A systematic literature search was conducted following PRISMA guidelines on Pubmed, Scopus and Cochrane Library. The following search string was adopted: (((restricted kinematic) AND (mechanical)) AND (alignment)) AND (knee). We included studies that analyzed rKA versus MA in terms of clinical outcomes and complications with a minimum of 6 months of follow up. The following rKA- and MA-related data were evaluated: patient-reported outcome scores (PROMs), radiographic analysis of lower limb alignment, and complications. Criteria from the Methodological Index for Non-Randomized Studies were used to assess the methodological quality of the articles.

RESULTS

This systematic review included seven clinical studies with a total of 892 knees (471 for MA group and 421 for rKA group, respectively). Overall, post-operative PROMs were similar between rKA and MA. Moreover, rKA reached better results regarding Forgotten Joint Score and post-operative patient satisfaction. Finally, no higher complication rate was observed with the rKA approach.

CONCLUSION

The rKA aims to restore native knee kinematics, avoiding extreme deformities. Clinical outcomes are not inferior or even better for rKA compared with MA, without increasing the risk of short-middle-term implant failure. However, there is a high heterogeneity regarding the 'restricted' protocols used.

High degree of alignment precision associated with total knee arthroplasty performed using a surgical robot or handheld navigation

PURPOSE

The purpose of this study was to compare the precision of bony resections during total knee arthroplasty (TKA) performed using different computer-assisted technologies.

METHODS

Patients who underwent a primary TKA using an imageless accelerometer-based handheld navigation system (KneeAlign2®, OrthAlign Inc.) or computed tomography-based large-console surgical robot (Mako®, Stryker Corp.) from 2017 to 2020 were retrospectively reviewed. Templated alignment targets and demographic data were collected. Coronal plane alignment of the femoral and tibial components and tibial slope were measured on postoperative radiographs. Patients with excessive flexion or rotation preventing accurate measurement were excluded.

RESULTS

A total of 240 patients who underwent TKA using either a handheld (n = 120) or robotic (n = 120) system were included. There were no statistically significant differences in age, sex, and BMI between groups. A small but statistically significant difference in the precision of the distal femoral resection was observed between the handheld and robotic cohorts (1.5° vs. 1.1° difference between templated and measured alignments, p = 0.024), though this is likely clinically insignificant. There were no significant differences in the precision of the tibial resection between the handheld and robotic groups (coronal plane 0.9° vs. 1.0°, n.s.; sagittal plane 1.2° vs. 1.1°, n.s.). There were no significant differences in the rate of overall precision between cohorts (n.s.).

CONCLUSIONS

A high degree of component alignment precision was observed for both imageless handheld navigation and CT-based robotic cohorts. Surgeons considering options for computer-assisted TKA should take other important factors, including surgical principles, templating software, ligament balancing, intraoperative adjustability, equipment logistics, and cost, into account.

LEVEL OF EVIDENCE

III.

Robotic technology in total knee arthroplasty

Key factors for successful total knee arthroplasty include accurate implant positioning with precise tibial and femoral resection, combined with appropriate soft tissue balancing to achieve the desired alignment. Robotic-assisted total knee arthroplasty allows surgeons to execute pre-planned strategies with precision, with growing evidence suggesting that robotic-assisted-total knee arthroplasty reduces radiological outliers. This has yet to be proven to translate into long-term improvements in patient-reported outcomes and implant survivorship. Robotic-assisted-total knee arthroplasty systems can be divided into fully autonomous and semi-autonomous systems. While fully autonomous systems showed initial promise, semi-autonomous systems are gaining popularity with encouraging early outcomes suggesting improved radiological and clinical outcomes, although concerns remain regarding a significant learning curve, installation costs, radiation exposure and cost associated with preoperative imaging. The future of total knee arthroplasty seems certain to involve robotic technology, although to what degree and in what capacity will depend on further high-quality studies assessing long-term outcomes, complications, survivorship and cost-benefit analyses.

Restoring Anatomical Features in Primary Total Knee Arthroplasty

Today, the number of people affected by gonarthrosis symptoms is increasing proportionally. Total knee arthroplasty (TKA) is a successful intervention that aims to reduce pain and restore knee function. However, studies have shown that active young patients still have limitations in performing activities such as skiing, golfing, surfing, and dancing. Over the last few years, total knee arthroplasty has undergone significant changes. Most of the modern TKA implants are designed to reproduce the normal biomechanics of the knee joint, mimicking the physiological pattern with greater compliance in the medial compartment between the tibial insert and femoral condyle and less congruence on the lateral side. Unfortunately, functional outcomes are compromised in approximately half of TKA patients. This loss may be caused by the abnormal kinematics and inherent instability of many contemporary implants. The proper alignment of the femoral component during TKA is a crucial step that influences postoperative results. The position of the femoral component in the axial plane is responsible for flexion stability, knee joint kinematics, flexion alignment, and patellar tracking. The main goal when choosing a type of prosthesis is to achieve an adequate recovery that leads to an improvement in mobility and an increase in the efficiency of the quadriceps.

Influence of Mechanical Alignment on Functional Knee Phenotypes and Clinical Outcomes in Primary TKA: A 1-Year Prospective Analysis

In total knee arthroplasty (TKA), functional knee phenotypes are of interest regarding surgical alignment strategies. Functional knee phenotypes were introduced in 2019 and consist of limb, femoral, and tibial phenotypes. The hypothesis of this study was that mechanically aligned (MA) TKA changes preoperative functional phenotypes, which decreases the 1-year Forgotten Joint (FJS) and Oxford Knee Score (OKS) and increases the 1-year WOMAC. All patients included in this study had end-stage osteoarthritis and were treated with a primary MA TKA, which was supervised by four academic knee arthroplasty specialists. To determine the limb, femoral, and tibial phenotype, a long-leg radiograph (LLR) was imaged preoperatively and two to three days after TKA. FJS, OKS, and WOMAC were obtained 1 year after TKA. Patients were categorized using the change in functional limb, femoral, and tibial phenotype measured on LLR, and the scores were compared between the different categories. A complete dataset of preoperative and postoperative scores and radiographic images could be obtained for 59 patients. 42% of these patients had a change of limb phenotype, 41% a change of femoral phenotype, and 24% a change of tibial phenotype of more than ±1 relative to the preoperative phenotype. Patients with more than ±1 change of limb phenotype had significantly lower median FJS (27 points) and OKS (31 points) and higher WOMAC scores (30 points) relative to the 59-, 41-, and 4-point scores of those with a 0 ± 1 change (p < 0.0001 to 0.0048). Patients with a more than ±1 change of femoral phenotype had significantly lower median FJS (28 points) and OKS (32 points) and higher WOMAC scores (24 points) relative to the 69-, 40-, and 8-point scores of those with a 0 ± 1 change (p < 0.0001). A change in tibial phenotype had no effect on the FJS, OKS, and WOMAC scores. Surgeons performing MA TKA could consider limiting coronal alignment corrections of the limb and femoral joint line to within one phenotype to reduce the risk of low patient-reported satisfaction and function at 1-year.

Clinical, Radiographic, and Patient-Reported Outcomes Associated with a Handheld Image-free Robotic-Assisted Surgical System in Total Knee Arthroplasty

One of the primary aims of total knee arthroplasty (TKA) is restoration of the mechanical axis of the lower limb. Maintenance of the mechanical axis within 3° of neutral has been shown to result in improved clinical results and implant longevity. Handheld image-free robotic-assisted total knee arthroplasty (HI-TKA) is a novel way of performing TKA in the era of modern robotic-assisted TKA. The aim of this study is to assess the accuracy of achieving targeted alignment, component placement, clinical outcomes, as well as patient satisfaction after HI-TKA.

The Adherence of Digital Templating of Cemented Bicondylar Total Knee Arthroplasty Reveals Gender Differences

INTRODUCTION

Preoperative digital templating is a standard procedure that should help the operating surgeon to perform an accurate intraoperative procedure. To date, a detailed view considering gender differences in templating total knee arthroplasty (TKA), stage of arthrosis, and the surgeons' experience altogether has not been conducted.

METHODS

A series of 521 patients who underwent bicondylar total knee arthroplasty was analyzed retrospectively for the planning adherence of digital templating in relation to sex, surgeon experience, and stage of arthrosis. Pre- and postoperative X-rays were comparably investigated for planned and implanted total knee arthroplasties. Digital templating was carried out through mediCAD version 6.5.06 (Hectec GmbH, 84032 Altdorf, Germany). For statistical analyses, IBM SPSS version 28 (IBM, 10504 Armonk, NY, US) was used.

RESULTS

The general planning adherence was 46.3% for the femur and 41.8% for the tibia. The Mann-Whitney U test revealed a gender difference for templating the femur (z = -5.486; p ≤ 0.001) and tibia (z = -3.139; p = 0.002). The surgeon's experience did not show a significant difference through the Kruskal-Wallis test in the femur (K-W H = 4.123; p = 0.127) and the tibia (K-W H = 2.455; p = 0.293). The stage of arthrosis only revealed a significant difference in the planning of the femur (K-L-score (K-W H = 6.516; p = 0.038) alone.

DISCUSSION/CONCLUSION

Digital templating for total knee arthroplasty brought up gender differences, with oversized implants for women and undersized implants for men. A high stage of femoral arthrosis can lead to the under and oversized planning of the surgeon. Since the surgeon's experience in planning did not show an effect on the adherence to templating, the beneficial effect of digital templating before surgery should be discussed.

Kinematic alignment results in clinically similar outcomes to mechanical alignment: Systematic review and meta-analysis

PURPOSE

It is unclear whether a difference in functional outcome exists between kinematically aligned (KA) and mechanically aligned (MA) knee replacements. The aim of this study is to perform a comprehensive systematic review and meta-analysis of the available level I-IV evidence.

METHODS

A meta-analysis of randomised controlled trials and observational studies comparing patient reported outcome measures (PROMs), range of motion (ROM), gait analysis and complications in TKA with KA and MA was performed. Quality assessment was performed for each study using the Joanna Briggs Institute (JBI) critical appraisal tools.

RESULTS

Twelve randomised controlled trials and fourteen observational studies published between 2014 and 2022 were included in the final analysis. Meta-analysis revealed KA to have significantly better Oxford Knee Score (OKS) (p = 0.02), Forgotten Joint Score (FJS) (p = 0.006), Knee Society Score (KSS) Objective Knee (p = 0.03) and KSS Functional Activity (p = 0.008) scores. However, these improvements did not exceed the minimum clinically important difference (MCID) values reported in the literature. Subgroup analysis showed robotic assisted KA-TKA to have a clinically superior FJS (p = 0.0002) and trend towards KSS Objective Knee score (p = 0.10), compared to PSI. Gait and plantar pressure distribution of KA cohorts more closely represented healthy cohorts, and KA showed a weak association of a decreased knee adduction moment (KAM) compared to MA. Differences in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), range of motion and complications were not significant between groups.

CONCLUSION

Although KA results in several improved functional outcomes, these do not reach clinical significance. Further standardised large-scale randomised studies are required to improve the quality of evidence. As it stands, it is difficult to recommend one philosophy over the other.

No advantage with navigated versus conventional mechanically aligned total knee arthroplasty-10 year results of a randomised controlled trial

PURPOSE

Computer-assisted surgery (CAS) total knee arthroplasty (TKA) remains a controversial area of surgical practice. The aim of this study is to report the ten-year revision rates and patient-reported outcome measures (PROMS) of a single-blinded, prospective, randomised controlled trial comparing electromagnetically (EM) navigated and conventional TKA.

METHODS

199 patients were randomised to receive either EM navigated or conventional TKA where the aim of implantation was neutral mechanical alignment in all cases. Ten-year revision rates were collated and compared between the two intervention groups. Longitudinal PROMS data was collected prospectively at various time points up to 10 years post-operatively.

RESULTS

Over the ten-year period, there were 23 deaths (22.8%) in the EM navigation cohort and 30 deaths (30.6%) in the conventional cohort. At 10 years post-operatively, there was no statistically significant difference in all cause revision between the EM navigation and conventional cohort (4.0 vs 6.1%, p = 0.429). When analysing causes of revision that might be influenced by utilising EM navigation, there was no statistically significant difference in revisions (3.0% EM navigated vs 4.1% conventional group, p = 0.591). Patients that received navigated TKAs had improved Oxford Knee Society, American Knee Society Score and range of motion at 3 months following surgery compared to conventional TKA (p = 0.002, p = 0.032, and p = 0.05, respectively). However, from 1 to 10 years post-operatively, both interventions had equivalent outcomes.

CONCLUSION

There is no difference in revision rates or clinical outcomes comparing EM navigated versus conventional TKA at ten-year follow-up. The expected mortality rate makes it unlikely that a difference in revision rates will reach statistical significance in the future. In the setting of an experienced knee arthroplasty surgeon, it is difficult to justify the additional costs of CAS in TKA surgery.

LEVEL OF EVIDENCE

I.

Recent Trends and Hotspots in Knee Arthroplasty: A Bibliometric Analysis and Visualization Study of the Last Five-Year Publications

Objectives

Bibliometric analysis is one of the most prevalent methods for analyzing and predicting the research trends of particular subjects. Through a bibliometric analysis, this study sought to look into and depict the hotspots and research trends in knee arthroplasty research over the previous five years.

Methods

The Web of Science Core Collection database was used to find research articles on knee arthroplasty published between 2018 and 2022. The VOS viewer, Cite Space, and Bibliometrix were used to carry out the bibliometric study and network visualization.

Results

During the previous five years, 7,422 included knee arthroplasty publications were cited 57,087 times. The United States and the Journal of Arthroplasty were the top countries and journals regarding the number of articles. The top 10 global high-impact documents were determined using the citation ranking and citation burst. The most frequently referenced article revealed that the epidemiological characteristics of knee arthroplasty, perioperative care in knee arthroplasty, prosthetic joint infections, and opioid medications were the hot topics in knee arthroplasty research. Keyword burst analysis showed that the research trends in knee arthroplasty through 2022 were racial disparity, limb alignment, tibial slope, and meniscectomy. The analysis of the subject areas revealed the close connections and relationships between different subject areas, as demonstrated by the figures.

Conclusion

The knee arthroplasty research community is highly productive and centralized. Recent hotspots in knee arthroplasty research were unicompartmental knee arthroplasty, periprosthetic joint infection, kinematic alignment, outpatient total knee arthroplasty (TKA), bariatric surgery, payment model, tranexamic acid, Robotic-Assisted TKA, patient-reported outcome measures, metaphyseal cone, opioid use, and patient-specific instrumentation. Research trends in knee arthroplasty research were racial disparity, limb alignment, tibial slope, and meniscectomy.

Outcomes of cruciate-retaining total knee arthroplasty for osteoarthritis with severe varus deformity

BACKGROUND

Varus deformity is common in osteoarthritic knee. The purpose of this study was to investigate the clinical and radiographic outcomes after cruciate-retaining (CR) total knee arthroplasty (TKA) for severely varus osteoarthritic knees and compare them to those of mildly to moderately deformed osteoarthritic knees.

METHODS

Eight hundred ninety-four subjects were undergone CR TKA, 137 had severe varus deformity (group 1), and 757 had mild-to-moderate deformity (group 2) of the lower limb preoperatively. Pre- and postoperative outcomes were compared between two groups clinically and radiographically.

RESULTS

Mean follow-up period was 54.7 ± 28.9 months. Mean age was 77.8 ± 6.7 years in group 1 and 74.5 ± 7.4 years in group 2 (p < 0.001). Preoperative hip-knee-ankle angle (HKAA) was - 17.7°±2.9° in group 1 and - 6.3° ± 5.1° in group 2 (p < 0.001). Preoperative range of motion (ROM) was 127.7° ± 15.2° in group 1 and 130.8 °± 9.6° in group 2 (p = 0.019). Preoperative Knee Society scores and WOMAC score were not significantly different between two groups. Postoperative HKAA was - 0.4° ± 2.3° in group 1 and 0.6 ° ± 2.0° in group 2 (p < 0.001). Postoperative ROM, Knee Society scores, and WOMAC score were not significantly different between two groups.

CONCLUSIONS

CR TKA showed results in subjects with severe varus deformities comparable to those without severe varus deformities. Whether the degree of preoperative varus deformity of the lower limb should be considered when deciding to perform CR-type or PS-type TKA requires further discussion.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Resection of Infrapatellar Fat Pad during Total Knee Arthroplasty Has No Impact on Postoperative Function, Pain and Sonographic Appearance of Patellar Tendon

Routine resection of the infrapatellar fat pad (IFP) during total knee arthroplasty (TKA) is controversial, as it may result in shortening of the patellar tendon (PT) and anterior knee pain. This prospective study examined whether IFP excision during TKA affects joint function, anterior knee pain, PT dimensions and sonographic structure. A total of 65 consecutive patients undergoing TKA for osteoarthritis were randomized into two groups: IFP was resected in one and retained in the other. Patients were examined preoperatively, at 6 weeks and 6 months postoperatively: pain (Numerical Rating Scale-NRS), range of motion (ROM) and knee function (Knee Injury and Osteoarthritis Outcome Score-KOOS score) were evaluated; sonographic examination determined the length, structure and vascularity of the PTs. In both groups there were postoperative improvements in NRS and KOOS scores, although IFP resection did not influence clinical outcomes or sonographic parameters. At 6 weeks and 6 months postoperatively for both groups there were no differences between NRS scores (Mann-Whitney test, p = 0.511 and p = 0.579), ROM scores (Mann-Whitney test, p = 0.331, p = 0.180) or all KOOS subscores. IFP excision had no effect on sonographic parameters. This study suggests that IFP resection during TKA does not influence postoperative functional outcomes, pain scores, patellar tendon length and thickness, or sonographic structure.

Arthroscopic-assisted robotic bi-unicompartmental knee arthroplasty: a pilot cadaveric study

INTRODUCTION

Although bicondylar arthroplasty showed great functional results, it encounters some difficulties to be performed routinely. On the other hand, arthroscopic techniques tend to replace open surgical techniques in sports medicine but strive to be developed in the field of arthroplasty. This study aimed to assess the feasibility of a micro-invasive bi-compartmental knee arthroplasty using both arthroscopic and robotic technologies (A-BiUKA).

MATERIALS AND METHODS

The study was conducted on complete fresh-frozen and embalmed cadaveric specimens. The main criterion of judgment was the successful positioning of trial implants through a minimal quad-sparing approach. Arthroscopy was used for bone-morphing and burring, supported by an image-free robotic system. Secondary criteria of judgment were axial deviation (measured using the navigation system), operating time, and incision length.

RESULTS

Ten A-BiUKA were performed. Implantation was successful in all cases. The mean preoperative frontal deviation was 179.8° ± 3.2 [175: 185], the mean postoperative frontal deviation was 178.5° ± 2.2 [175: 182], without any outliers. The mean correction was 1.7° ± 1.6 [0: 5]. Once the eight first A-UKA were performed, constituting the learning curve, the mean operative time for the remaining twelves surgeries was 90 min ± 6. The mean skin incision length was 3.35 cm ± 0.13 [3: 4].

CONCLUSION

Associated arthroscopic and robotic technologies allows to perform Bi-UKA procedure using a quad sparing mini-invasive approach. Clinical prospective studies have to confirm the feasibility and the clinical outcomes of this surgery.

Restricted kinematic alignment may be associated with increased risk of aseptic loosening for posterior-stabilized TKA: a case-control study

PURPOSE

The purpose of the study was to compare clinical and radiological results between kinematic alignment (KA) and mechanical alignment (MA) with a posterior-stabilized (PS) total knee arthroplasty (TKA) with a post-cam mechanism at a minimum follow-up of 3 years. The authors hypothesized a higher risk of aseptic loosening when performing KA using PS TKA.

METHODS

A retrospective monocentric single surgeon case control study was performed comparing 100 matched patients who had TKA performed using a MA philosophy to 50 patients receiving TKA with a KA technique between January 2016 and October 2017. All patients had the same knee prosthesis (GMK primary posterior-stabilized, Medacta^®, Switzerland). Patient specific cutting blocks were used in both groups and a restricted KA (rKA) was aimed in the KA group. A hybrid cementation technique was performed. The new Knee Society Score (KSS) and radiological assessment were collected preoperatively and at the final follow-up. Comparisons between groups were done with the T test or Fisher exact test. Global survival curves were estimated with Kaplan-Meier model. Significance was set at p < 0.05.

RESULTS

Mean follow-up was 42.9 months ± 3.6 (range 37.6-46.7) and 53.3 months ± 4.1 (range 45.5-59.8) for rKA and MA groups. Postoperatively, no significant differences were found for clinical scores between both groups. Radiological assessment found similar postoperative Hip-Knee-Ankle angle for rKA and MA groups (178° versus 179° respectively, NS). At last follow-up, a significant higher survivorship was found for the MA group compared to the rKA group (97 versus 84%; p < 0.001) for aseptic loosening revision as the endpoint.

CONCLUSION

An increased risk of tibial implant loosening was found with rKA compared to MA using a posterior-stabilized TKA with a post-cam system at short-term follow-up. Caution should be taken when choosing the TKA design while performing rKA.

LEVEL OF EVIDENCE

Retrospective case-control study, Level IV.

Posterior Tibial Slope in Computer-Navigated Total Knee Arthroplasty: The Transmalleolar Sagittal Axis Underestimates Slope Compared to Traditional Intramedullary Axis

BACKGROUND

Tibial slope in total knee arthroplasty (TKA) impacts knee flexion, balance, and ligament strain. Implants were initially designed with tibial slope recommendations based on the intramedullary axis. However, technology-assisted TKA, such as robotics or navigation, determines slope from the ankle-knee axis connecting the center of the transmalleolar line to the proximal exit point of the tibial shaft axis. We sought to quantify the difference in tibial slope between the traditional intramedullary and transmalleolar sagittal tibial axes.

METHODS

We retrospectively identified 40 TKAs with preoperative computed tomography scans. We reconstructed the 3-dimensional geometry of the tibia and fibula and determined the intramedullary axis as the best fit cylinder to the tibial shaft. We defined the transmalleolar axis according to accepted industry standards. We measured the angular difference between both axes in the sagittal plane.

RESULTS

The transmalleolar axis was radiographically posterior to the intramedullary axis in 39 knees. Utilizing the transmalleolar axis to set posterior tibial slope would reduce the posterior tibial slope by a mean of 1.9° ± 1.3° compared to the intramedullary axis. Furthermore, the posterior slope would be reduced between 0° and 2° in 24 knees (60%), between 2° and 4° in 10 knees (25%), and more than 4° in 5 knees (13%).

CONCLUSION

Tibial components implanted with technology assistance referencing the transmalleolar axis to set posterior slope will show an average of 1.9° less posterior slope when measured in sagittal plain radiographs, potentially concerning for knee kinematics.

The Morphology of a Kinematically Aligned Distal Femoral Osteotomy Is Different from That Obtained with Mechanical Alignment and Could Have Implications for the Design of Total Knee Arthroplasty

Background: Kinematically aligned total knee arthroplasty (KA-TKA) may lead to a different pattern of osteotomy from mechanically aligned total knee arthroplasty (MA-TKA). This paper aims to analyze the effects of KA and MA on the morphology of the distal femoral osteotomy surface. Methods: Computed tomography scans of 80 TKA candidates were reconstructed into 3D models. The measurement of bone morphology was performed after the distal femur cut according to two different alignment techniques. The aspect ratio, trapezoidicity ratio, and asymmetry ratio of the distal femur were assessed. Results: The aspect ratio and the asymmetry ratio in the KA group was significantly lower than that in the MA group in the general population (p < 0.001). The trapezoidicity ratio in the KA group was significantly higher than that in the MA group in the general population (p < 0.001). Conclusions: It was found that KA-TKA and MA-TKA presented different morphologies of the distal femoral osteotomy surface, and this difference was also influenced by gender. The surgery pattern of KA-TKA and MA-TKA and gender should be considered when surgeons choose femoral prostheses.

Correctability of the knee joint observed under a stressed state

BACKGROUND

Well-balanced postoperative knee joints are often based on subjective 'feel' of experienced surgeons rather than quantifiable references. Most alignment strategies continue to reference the bone despite the complexity in anatomical variations and presence of deformity. Categorical prescription of a singular alignment philosophy for all patients may not be appropriate. This study aims to characterize coronal alignment correctability in relation to anatomical measures to develop a mechanism for distinguishing patients for whom repeatable strategies are optimal in the form of alternative alignment techniques or advanced soft tissue balancing.

METHODS

A consecutive series of 103 pre-operative knees who underwent primary total knee arthroplasty (TKA) were analysed. Pre-operative supine computer tomography (CT) scans were segmented, with output STL bone models placed against several stressed positions determined by the TELOS SD-900 (METAX, Germany) device. Anatomical analysis using two-dimensional (2D) -3D image registration was performed. Statistical analysis was conducted for variations in anatomical morphology and regression modelling was used to determine the relationship between these measurements and correctability of a patient.

RESULTS

The mean preoperative supine hip-knee-ankle (HKA) angle was 5.1° and 2.3°, lateral distal femoral angle (LDFA) was 2.0° and 3.1°, medial proximal tibial angle (MPTA) was 3.7° and 3.0° varus for male and female, respectively. The mean laxity range was 4.3°. We found 36% of valgus patients and 55% of mild varus patients to be correctable. Supine HKA was a statistically significant predictor for correctability (P < 0.001). A statistically significant correlation between laxity and the HKA (P = 0.01) as well as LDFA angles (P = 0.01) exist for the mild varus cohort.

CONCLUSION

Relationship between HKA angle and the correctability of the knee joint to neutral in patients presenting with mild to moderate varus cannot be consistently predicted using bony anatomy. If there is a desire to avoid ligament release during TKA, careful consideration of both a patient's bony anatomy and soft tissue laxity envelope must be made prior to surgery.

The medial condylar wall is a reliable landmark to kinematically align the femoral component in medial UKA: an in-silico study

PURPOSE

Kinematic alignment (KA) aligns the femoral implant perpendicular to the cylindrical axis in the frontal and axial plane. Identification of the kinematic axes when using the mini-invasive sub-quadricipital approach is challenging in unicompartmental knee arthroplasty (UKA). This study aims to assess if the orientation of condylar walls may be suitable for use as an anatomical landmark to kinematically align the femoral component in medial UKA. It was hypothesised that the medial wall of the medial condyle would prove to be a reliable anatomical landmark to set both the frontal and axial alignment of the femoral component in medial UKA.

METHODS

73 patients undergoing medial UKA had pre-operative CT imaging to generate 3D models. Those with osteophytes that impaired visualisation of the condylar walls were excluded. 28 patients were included in the study. The ideal KA was determined using the cylindrical axis in the frontal and axial plane. Simulations using the medial wall of the medial condyle (MWMC) and the lateral wall of the medial condyle (LWMC) were performed to set the frontal alignment. To set the axial alignment, the MWMC, LWMC, medial wall of the lateral condyle (MWLC), and medial diagonal line (MDL) anatomical landmarks were investigated. Differences between the ideal measured KA values and values obtained using landmarks were investigated.

RESULTS

Use of the MWMC let to similar frontal alignment compared to the ideal KA (2.9° valgus vs 3.4° valgus, p = 0.371) with 46.4% (13/28) of measurements being [Formula: see text] 1.0° different from the ideal KA and only 1 simulation with greater than 4.0° difference. Use of the MWMC led to very similar axial alignments compared to the ideal KA (0.5° internal vs 0.0°, p = 0.960) with 75.0% (21/28) of measurements being [Formula: see text] 1.0^o different from the ideal KA, and a maximum difference of 3.0°. Use of the MWLC and MDL was associated with significant statistical differences when compared to the ideal KA (p < 0.001 for both).

CONCLUSIONS

The native orientation of the medial condylar wall seems to be a reliable anatomical landmark for aligning the femoral component in medial KA UKA in both the axial plane and frontal planes. Other assessed landmarks were shown to not be reliable. Clinical and radiographic assessments of the reliability of using the MWMC to set the frontal and axial orientation of the femoral component when performing a medial KA UKA are needed.

Total Knee Arthroplasty and Intra-Articular Pressure Sensors: Can They Assist Surgeons with Intra-Operative Decisions?

PURPOSE OF REVIEW

Soft tissue imbalance, presenting as instability or stiffness, is an important cause of revision total knee arthroplasty (TKA). Traditional methods of determining soft tissue balance of the knee lack precision and are not reliable between operators. Use of intra-operative pressure sensors offers the potential to identify and avoid soft tissue imbalance following TKA. This review aims to summarise the literature supporting the clinical indication for the use of intra-articular pressure sensors during TKA.

RECENT FINDINGS

Analytical validation studies suggest that intra-operative pressure sensors demonstrate 'moderate' to 'good' intra-observer reliability and 'good' to 'excellent' interobserver reliability throughout the flexion arc. However, there are important errors associated with measurements when devices are used out-with the stated guidelines and clinicians should be aware of the limitations of these devices in isolation. Current evidence regarding patient benefit is conflicting. Despite positive early results, several prospective studies have subsequently failed to demonstrate significant differences in overall survival, satisfaction, and patient-reported outcome measures within 1 year of surgery. Surgeon-defined soft tissue stability appears to be significantly different from the absolute pressures measured by the intra-operative sensor. Whilst it could be argued that this confirms the need for intra-articular sensor guidance in TKA; the optimal 'target' balance remains unclear and the relationship with outcome in patients is not determined. Future research should (1) identify a suitable reference standard for comparison; (2) improve the accuracy of the sensor outputs; and (3) demonstrate that sensor-assisted TKA leads to patient benefit in patient-reported outcome measures and/or enhanced implant survival.

Revision Total Knee Arthroplasty With the Use of Restricted Kinematic Alignment Protocol: Surgical Technique and Initial Results

Purpose: Kinematic alignment (KA) for primary total knee arthroplasty (TKA) has been shown to provide equivalent or better results to mechanical alignment (MA). The use of KA in revision TKA to restore the individual knee anatomy, kinematics, and soft-tissue balance, has not been documented yet. The purpose of this study is to describe the technique for performing TKA revision using the restricted KA (rKA) protocol and to report (1) rerevision rate and adverse events, (2) patient-reported outcome measures (PROMs), and (3) radiological signs of implant dysfunction related to this technique.

Methods: The rKA protocol was used in 43 selected TKA revisions cases suitable for the technique. Adverse events, reoperation, revision, and their causes were recorded. In addition, PROMs assessed by WOMAC score and radiographic evaluation to identify signs of implant dysfunction were documented at last follow-up.

Results: After a mean follow-up of 4.0 years (0.9–7.7, ±2), only one rerevision (2.3%) was required for persisting instability (polyethylene liner exchange from posterior stabilized to a semi-constrained). Short-cemented stems were used for both the femur and tibia in 28 (65%) cases, for the femur alone in 13 (30%) cases, and no stems in two cases. In 31 (72%) cases, a standard posterior stabilized tibial insert was used, while 12 (28%) cases required a semi-constrained insert. The mean WOMAC score was 34.4 (0–80, ±21.7). Mean postoperative arithmetic hip-knee-ankle angle (HKA) was 0.8° varus (from 5° varus to 4° valgus), mean mechanical distal femoral angle was 1.7° valgus (from 2° varus to 5° valgus), and mean mechanical tibia proximal angle was 2.2° varus (from 5° varus to 1° valgus). No radiological evidence of aseptic loosening or periprosthetic radiolucencies were identified.

Conclusion: Although current revision TKA implants are not ideal for revision TKA performed with rKA, they are an appealing alternative to MA, especially in cases of early, non-wear-related, unsuccessful MA TKAs. rKA TKA revision using short-cemented stems in conjunction with meticulous preoperative planning is safe in the mid-term.

Level of evidence: IV

Effect of gap balancing and measured resection techniques on implant migration and contact kinematics of a cementless total knee arthroplasty

BACKGROUND

The purpose of this study was to compare implant migration and tibiofemoral contact kinematics of a cementless primary total knee arthroplasty (TKA) implanted using either a gap balancing (GB) or measured resection (MR) surgical technique.

METHODS

Thirty-nine patients underwent TKA via a GB (n = 19) or a MR (n = 20) surgical technique. Patients received an identical fixed-bearing, cruciate-retaining cementless implant. Patients underwent a baseline radiostereometric analysis (RSA) exam at two weeks post-operation, with follow-up visits at six weeks, three months, six months, and one year post-operation. Migration including maximum total point motion (MTPM) of the femoral and tibial components was calculated over time. At the one year visit patients also underwent a kinematic exam via RSA.

RESULTS

Mean MTPM of the tibial component at one year post-operation was not different (mean difference = 0.09 mm, p = 0.980) between the GB group (0.85 ± 0.37 mm) and the MR group (0.94 ± 0.41 mm). Femoral component MTPM at one year post-operation was also not different (mean difference = 0.27 mm, p = 0.463) between the GB group (0.62 ± 0.34 mm) and the MR group (0.89 ± 0.44 mm). Both groups displayed similar kinematic patterns.

CONCLUSIONS

There was no difference in implant migration and kinematics of a single-radius, cruciate retaining cementless TKA performed using a GB or MR surgical technique. The magnitude of migration suggests there is low risk of early loosening. The results provide support for using the cementless implant with either a GB or MR technique.

[Total knee arthroplasty in the young patient-an update]

The absolute number of total knee arthroplasties (TKA) continues to rise every year. About 10% of the patients are less than 55 years of age, although it is known that functional results and patient satisfaction are lower combined with an increased likelihood of revision compared to older patients. Higher physical activity and patient expectations are a major challenge in this age group. At the same time, the incidence of posttraumatic/postoperative alterations is high, including ligamentous or bony deficiencies, which can make the surgical procedure challenging. In view of these facts conservative treatments and joint sparing procedures should always be considered first. The potential correction of lower-limb deformities and unicompartmental knee arthroplasties need to be carefully evaluated before considering total knee arthroplasty. Only in advanced cases of osteoarthritis in more than one compartment of the knee of with combined ligamentous instability, can a TKA provide satisfactory results in the young patient. However, the strongest predictor of satisfaction is a realistic expectation.

Can robot-assisted total knee arthroplasty be a cost-effective procedure? A Markov decision analysis

BACKGROUND

Total knee arthroplasty (TKA) is a frequently and increasingly performed surgery in the treatment of disabling knee osteoarthritis. The rising number of procedures and related revisions pose an increasing economic burden on health care systems. In an attempt to lower the revision rate due to component malalignment and soft tissue imbalance in TKA, robotic assistance (RA) has been introduced in the operating theatre. The primary objective of this study is to provide the results of a theoretical, preliminary cost-effectiveness analysis of RA TKA.

METHODS

A Markov state-transition model was designed to model the health status of sixty-seven-year-old patients in need of TKA due to primary osteoarthritis over a twenty-year period following their knee joint replacement. Transitional probabilities and independent variables were extracted from existing literature.

RESULTS

The value attributed to the utility both for primary and revision surgery has the biggest impact on the ICER, followed by the rate of successful primary surgery and the cost of RA-technology. Only 2.18% of the samples yielded from the probabilistic sensitivity analysis proved to be cost-effective (threshold set at $50000/QALY). A calculated surgical volume of at least 253 cases per robot per year is needed to prove cost-effective taking the predetermined parameter values into account.

CONCLUSION

Based upon transitional probabilities and independent variables derived from existing studies, RA TKA may be cost-effective at a surgical volume of 253 cases per robot per year when compared to conventional TKA.

Total knee replacement wear during simulated gait with mechanical and anatomic alignments

Total knee replacements (TKR) have historically been implanted perpendicular to the mechanical axis of the knee joint, with a commensurate external rotation of the femur in flexion relative to the posterior condylar axis (PCA). Although this mechanical alignment (MA) method has typically offered good long-term survivorship of implants, it may result in alignment of the implant that departs significantly from the native Joint Line (JL) in extension and flexion for a considerable portion of the patient population. There is a growing interest with surgeons to implant TKR components more closely aligned to the natural JL (Anatomic Alignment-AA) of the patient's knee joint to reduce the need for soft tissue releases during surgery, potentially improving knee function and patient satisfaction. Using a previously-validated finite element model of the lower extremity, implant- and alignment-specific loading conditions were developed and applied in a wear experiment via a six-degree-of-freedom joint simulator. MA was defined as 0° Joint Line (JL), 0° varus hip-knee-ankle (HKA) angle, and 3° external femoral rotation. AA was defined as 5° varus JL, 3° varus HKA, and 0° femoral rotation. The experiment returned wear rates of 3.76 ± 0.51 mg/million cycles (Mcyc) and 2.59 ± 2.11 mg/Mcyc for ATTUNE^® cruciate-retaining (CR) fixed bearing (FB) in MA and AA, respectively. For ATTUNE posterior-stabilized (PS) FB in AA, the wear rate was 0.97 ± 1.11 mg/Mcyc. For ATTUNE CR rotating platform (RP), the wear rates were 0.23 ± 0.19 mg/Mcyc, 0.48 ± 1.02 mg/Mcyc in MA and AA respectively. Using a two-way ANOVA, it was determined that there was no significantly difference in the wear rates between AA and MA (p = 0.144) nor the wear rate of ATTUNE PS FB in AA significantly different from either ATTUNE CR FB or ATTUNE CR RP.

Artificial intelligence and surgical innovation: lower limb arthroplasty

The number of patients requiring hip and knee arthroplasty continues to rise each year. Patients are living longer and expecting to remain active into later life following joint replacement. Developments in computer-assisted surgery and robotic technology may optimise surgical outcomes and patient satisfaction following lower limb arthroplasty. The use of artificial intelligence in healthcare is rapidly growing and has gained momentum in lower limb arthroplasty. This article reviews the use of artificial intelligence and surgical innovation in lower limb arthroplasty, with a particular focus on robotic-assisted surgery in total knee arthroplasty.