Kinematic Alignment Research Articles

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

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. An online survey with 57questions 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. 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 aminor 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%). The results indicate arelatively 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.

Sparse and inconsistent reporting of pre- and post-operative radiographic angles of total knee arthroplasty using true unrestricted kinematic alignment: An umbrella review and secondary meta-analysis.

To identify, synthesise and critically appraise findings of systematic reviews and meta-analyses on pre- and post-operative radiographic angles (lateral distal femoral angle [LDFA], medial proximal tibial angle [MPTA] and hip-knee-ankle [HKA] angle) of unrestricted kinematic alignment versus mechanical alignment in total knee arthroplasty (TKA). Two authors searched MEDLINE, EMBASE and Epistemonikos for systematic reviews, with or without meta-analyses, that reported on TKA outcomes using unrestricted kinematic alignment. The methodological quality of the included systematic reviews and meta-analyses was independently assessed using A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2). The effect size with its 95% confidence interval (CI) for radiographic angles was extracted from the systematic reviews and meta-analyses. The characteristics of clinical studies included in systematic reviews were listed and tabulated. Pre- and post-operative MPTA, LDFA and HKA angles were summarised using meta-analytic random-effects models. Nineteen records were eligible for data extraction. Systematic reviews and meta-analyses included 44 clinical studies, of which 31 were on unrestricted kinematic alignment and 13 were on restricted versions of kinematic alignment. None of the included systematic reviews or meta-analyses fulfiled all seven critical AMSTAR-2 domains. Few comparative studies reported both pre- and post-operative angles (LDFA, n = 3; MPTA, n = 4; and HKA angle, n = 10). Mean pre- and post-operative LDFAs were 88.0° (range, 83-94°) and 88.0° (range, 80-96°) for the kinematic alignment group, and 88.2° (range, 83-95°) and 90.2° (range, 84-97°) for the mechanical alignment group. Mean pre- and post-operative MPTAs were 86.0° (range, 78-93°) and 87.1° (range, 78-94°) for the kinematic alignment group and 86.4° (range, 77-94°) and 89.6° (range, 84-95°) for the mechanical alignment group. Mean pre- and post-operative HKA angles were -3.3° (range, -24° to 24°) and -0.3° (range, -10° to 8°) for the kinematic alignment group and -6.9° (range, -25° to 7°) and -0.9° (range, -8° to 7°) for the mechanical alignment group. Most systematic reviews and meta-analyses that report outcomes of TKA using kinematic alignment do not distinguish between the different versions of kinematic alignment. The clinical studies included in systematic reviews are limited and inconsistent in their reporting of radiographic angles. Different alignment strategies are often grouped under the umbrella term of kinematic alignment, which contributes to conflicting reports, confusion and unresolved questions regarding the efficacy of true unrestricted kinematic alignment. Level IV.

A Restriction Boundary-Based Coronal Plane Alignment of the Knee (CPAK) Classification for Restricted Kinematic Alignment Total Knee Arthroplasty

A Restriction Boundary-Based Coronal Plane Alignment of the Knee (CPAK) Classification for Restricted Kinematic Alignment Total Knee Arthroplasty

Kinematic versus mechanical alignment: A systematic review of systematic reviews and meta-analyses of randomised controlled trials.

The purpose of this study was to review the currently available systematic reviews and meta-analyses comparing kinematic alignment (KA) and mechanical alignment (MA). A literature search was performed to obtain all systematic review and meta-analyses comparing KA to MA that included one or more randomised controlled trials. A total of 18 studies were obtained, three of which were systematic reviews without meta-analysis. Studies were evaluated based on their meta-analysis methodology, appropriate inclusion criteria, the use of correct definitions of each alignment technique, and risk of bias. These 18 studies included between 3 and 14 RCTs in each study. From the perspective of study design, the majority of papers had low risk of bias. In contrast, most of these reviews had technical issues pertaining to study inclusion in their meta-analyses that would potentially compromise their conclusions. These included mixing time points in the analysis, duplicate inclusion of patients in a meta-analysis, inclusion of studies with incorrect definitions of KA, inclusion of studies performed with restricted kinematic alignment with the KA group, and inappropriate combination of studies with bilateral total knee arthroplasty (TKA) with studies with unilateral TKA. The current literature is inadequate to determine if there is any advantage to KA compared to MA in TKA. Claims made in systematic reviews and meta-analyses on the subject must be carefully scrutinised based not only on risk of bias but also on the included study populations, the surgical methodology of each underlying study, and the authors' understanding of the definitions of each alignment technique. Level 1 based on this study being a systematic review with the inclusion of only systematic reviews and meta-analyses of randomised controlled trials.

Revision Surgery due to Patient Dissatisfaction with Remaining Valgus leg Alignment after Kinematically Aligned Total Knee Arthroplasty: A Case Report

BACKGROUND: The kinematic alignment (KA) technique aims to achieve true resurfacing of the knee joint and recreate prearthritic anatomy while preserving soft tissues. However, it remains uncertain whether all prearthritic anatomies are biomechanically equivalent and if KA is suitable for cases with extreme anatomical variations. CASE PRESENTATION: The case of a 75-year-old female patient with a moderate valgus deformity who underwent kinematically aligned total knee arthroplasty (TKA) was reported. The patient required early revision surgery due to persistent pain in the medial collateral ligament area and dissatisfaction with the postoperative leg alignment. CONCLUSION: There is a paucity of studies addressing the outcomes of kinematically aligned TKA in patients with valgus knees. Concerns persist regarding the suitability of unrestricted KA for all anatomical variations, particularly extreme ones. This case underscores the importance of considering restricted KA as a potentially safer alternative. In addition, patient perception of limb alignment and appearance significantly impacts the success of total knee arthroplasty, particularly in cases with valgus deformities.

Effect of inverse kinematic alignment total knee arthroplasty on coronal alignment of the ankle joint in patients with varus knee deformity.

Varus or valgus knee deformities influence ankle coronal alignments. The impact of Total Knee Arthroplasty (TKA) on ankle joint alignment has not been entirely illustrated. Inverse Kinematic Alignment (iKA) is a surgical philosophy that aims to restore soft tissue balance, function, and native anatomy within validated boundaries to restore restrictive native kinematics. Therefore, this study aimed to investigate the postoperative association of patient-specific alignment on the coronal alignment of the ankle in patients with varus knee deformity who underwent iKA TKA. We hypothesized that greater preoperative varus malalignments would correlate with significant postoperative ankle coronal alignment changes. This retrospective study of a prospective collected cohort assessed patients who underwent imageless navigation assisted robotic TKA using a single implant design for primary osteoarthritis between January 2022 and August 2023. Preoperative and postoperative full-length standing anteroposterior X-ray imaging was used to measure Hip-Knee-Ankle (HKA), Tibial Plafond Inclination (TPI), Talar inclination (TI), and Tibiotalar Tilt (TTT) angles. Patients were subsequently divided into groups of neutral varus) < 10°) and severe varus (≥ 10°) according to the preoperative HKA angle. Significant changes in preoperative and postoperative HKA angles were found in the severe varus (14.5° vs. 6.4°, p < 0.001) group. Changes were also significant between preoperative and postoperative TPI and TI angles in the severe varus group; however, TTT did not reach statistical significance. Delta change from pre- to postoperative HKA was significantly higher for the severe varus group (8.1° vs. 0.8°, p < 0.019). Delta change of TPI, TI and TTT did not differ between groups. Coronal knee alignment after TKA affects coronal alignment of the ankle. iKA technique in TKA for varus knee deformity preserves or minimizes substantial coronal alignment changes of the ankle joint. These findings may add to the benefits reported for patient specific alignment TKA techniques. III.

Boundaries in Kinematic Alignment: Why, When, and How.

The use of alternative alignments in total knee arthroplasty (TKA) has recently been increasing in popularity: many of these alignments have been included in the broad spectrum of "kinematic alignment." This alternative approach was recommended to increase patients' satisfaction since many studies based on patient-reported outcome measures (PROMs) showed that every fifth patient is not satisfied with the surgical outcome. In fact, the original kinematic alignment technique was designed as a "pure resurfacing" technique, maintaining the preoperative axes (flexion-extension and axial rotation) of the knee. In adjunct, many new classifications of the preoperative limb deformity have been proposed to include a large range of knee anatomies, few of them very atypical. Following those classifications, many surgeons aimed for a reproduction of unusual anatomies putting in jeopardy the survivorship of the implant according to the classical "dogma" of a poor knee kinematics and TKA biomechanics if the final hip-knee-ankle (HKA) axis was not kept within 5 degrees from neutral. This article reviews the literature supporting the choice of setting alignment boundaries in TKA when surgeons are interested in reproducing the constitutional knee anatomy of the patient within a safe range.

An Insert Goniometer Can Help Select the Optimal Insert Thickness When Performing Kinematically Aligned Total Knee Arthroplasty with a Medial 1:1 Ball-in-Socket and Lateral Flat Surface Insert and Posterior Cruciate Ligament Retention.

Current surgical practices in total knee arthroplasty (TKA) have advanced and include significant changes and improvements in alignment philosophies, femorotibial implant conformities, and ligament management to replicate in vivo knee kinematics. While corrective measures have emphasized sagittal plane alignment to restore normal flexion-extension (F-E) motion and coronal plane ligament balance, internal-external (I-E) rotation kinematics in the axial plane have been largely neglected. Recent in vivo evidence indicates that the combination of factors necessary to closely restore native tibial rotation as the knee flexes and extends is kinematic alignment (KA), which resurfaces the patient's pre-arthritic knee without releasing ligaments, an insert with medial 1:1 ball-in-socket conformity and a lateral flat surface, and posterior cruciate ligament (PCL) retention. However, the inherent anterior-posterior (A-P) stability provided by the medial 1:1 ball-in-socket limits the surgeon's ability to select the correct insert thickness using manual laxity testing. Accordingly, this review presents the design and validation of an instrument called an insert goniometer that measures I-E tibial rotation for inserts that differ in thickness by 1 mm and uses rotation limits at extension and 90° flexion to select the optimal insert thickness. The optimal thickness is the one that provides the greatest external tibial orientation in extension and internal tibial orientation at 90° flexion without lift-off of the insert.

Better restoration of joint line obliquity in tibia first restricted kinematic alignment versus mechanical alignment TKA.

In total knee arthroplasty (TKA), suboptimal restoration of joint line obliquity (JLO) and joint line height (JLH) may lead to diminished implant longevity, increased risk of complications, and reduced patient reported outcomes. The primary objective of this study is to determine whether restricted kinematic alignment (rKA) leads to improved restoration of JLO and JLH compared to mechanical alignment (MA) in TKA. This retrospective study assessed patients who underwent single implant design TKA for primary osteoarthritis, either MA with manual instrumentation or rKA assisted with imageless navigation robotic arm TKA. Pre- and post-operative long standing AP X-ray imaging were used to measure JLO formed between the proximal tibial joint line and the floor. JLH was measured as the distance from the femoral articular surface to the adductor tubercle. Overall, 200 patients (100 patients in each group) were included. Demographics between the two groups including age, sex, ASA, laterality, and BMI did not significantly differ. Distribution of KL osteoarthritis classification was similar between the groups. For the MA group, pre- to post-operative JLO significantly changed (2.94° vs. 2.31°, p = 0.004). No significant changes were found between pre- and post-operative JLH (40.6mm vs. 40.6mm, p = 0.89). For the rKA group, no significant changes were found between pre- and post-operative JLO (2.43° vs. 2.30°, p = 0.57). Additionally, no significant changes were found between pre- and post-operative JLH (41.2mm vs. 42.4mm, p = 0.17). Pre- to post-operative JLO alteration was five times higher in the MA group compared to the rKA group, although this comparison between groups did not reach statistical significance (p = 0.09). rKA-TKA results in high restoration accuracy of JLO and JLH, and demonstrates less pre- and post-operative JLO alteration compared to MA-TKA. With risen interest in joint line restoration accuracy with kinematic alignment, these findings suggest potential advantages compared to MA. Future investigation is needed to correlate between joint line restoration accuracy achieved by rKA and enhanced implant longevity, reduced risk of post-operative complications, and heightened patient satisfaction.

A bone graft from the tibial resection or patella that rectified a tibial over-resection reliably healed and improved clinical outcome scores: A retrospective study of kinematically aligned TKA.

During kinematically aligned (KA) total knee arthroplasty (TKA), the surgeon may need to rectify an over-resection of the medial, lateral or posterior tibia. This study tested the hypothesis that a bone graft taken from the tibial resection or patella and impacted beneath a tibial baseplate would heal, regardless of whether the tibial component and knee were in outlier ranges according to mechanical alignment (MA) criteria. The study also tested the hypothesis that the Oxford Knee Score (OKS) and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) would improve beyond the substantial clinical benefit and that the source and thickness of the bone graft would not influence their improvement. This retrospective study radiographically assessed the healing of a bone graft from the tibial resection (n = 19) or patella (n = 10) in 29 KA TKAs (18 females, mean age 65 years). The tibial component and knee alignment were categorized as in-range or outliers based on reported MA criteria for bone graft healing and implant survival. The one-sample t test identified differences in the improvement of the OKS and KOOS JR from their reported substantial clinical benefit of 16 and 20 points, respectively. At an average follow-up of 37 months, all bone grafts healed even though ≥55% of tibial components and 34% of knees were varus outliers according to MA criteria for bone healing and implant survival. Amongst the 29 patients, the mean OKS and KOOS JR improvements of 25 ± 11 and 47 ± 21 points, respectively, surpassed the threshold of their respective substantial clinical benefit (p < 0.01) and were not influenced by the bone graft's source and thickness (p ≥ 0.51). During cemented KA TKA, the surgeon can use a bone graft from the tibial resection or patella to rectify a tibial over-resection. This technique led to consistent bone healing and improved outcome scores. Level IV.

Excellent results of restricted kinematic alignment total knee arthroplasty at a minimum of 10 years of follow-up.

While restricted kinematic alignment (rKA) total knee arthroplasty (TKA) with cemented implants has been shown to provide a similar survivorship rate to mechanical alignment (MA) in the short term, no studies have reported on the long-term survivorship and function. One hundred four consecutive cemented cruciate retaining TKAs implanted using computer navigation and following the rKA principles proposed by Vendittoli were reviewed at a minimum of 10 years after surgery. Implant revisions, reoperations and clinical outcomes were assessed using knee injury and osteoarthritis outcome score (KOOS), forgotten joint score (FJS), patients' satisfaction and joint perception questionnaires. Radiographs were analyzed to identify signs of osteolysis and implant loosening. Implant survivorship was 99.0% at a mean follow-up of 11.3 years (range: 10.3-12.9) with one early revision for instability. Patients perceived their TKA as natural or artificial without limitation in 50.0% of cases, and 95.3% were satisfied or very satisfied with their TKA. The mean FJS was 67.6 (range: 0-100). The mean KOOS were as follows: pain 84.7 (range: 38-100), symptoms 85.5 (range: 46-100), function in daily activities 82.6 (range: 40-100), function in sport and recreation 35.2 (range: 0-100) and quality of life 79.1 (range: 0-100). No radiological evidence of implant aseptic loosening or osteolysis was identified. Cemented TKA implanted with the rKA alignment protocol demonstrated excellent long-term implant survivorship and is a safe alternative to MA to improve patient function and satisfaction. IV, continuous case series with no comparison group.

Two-Year Outcomes are Equal in Kellgren-Lawrence Osteoarthritis Grades 1-4 after Total Knee Arthroplasty with Medial-Pivot Implants and Kinematic Alignment.

Introduction While risks exist with total knee arthroplasty (TKA) and survivorship is not indefinite, delaying surgery may lead to further deterioration of the knee joint, functional outcomes, and health status. Most studies report that patients with high-grade osteoarthritis (OA) scores have higher satisfaction and functional scores, cautioning against TKA in those with lower OA grades. This study correlates Kellgren-Lawrence (KL) OA scores with outcomes following kinematically-aligned TKA. Methods Preoperative anteroposterior weight-bearing radiographs of 168 patients enrolled in a prospective trial were scored for KL grade. Patients were segregated into two groups: the low-grade OA group had KL scores of 1 or 2, the high-grade OA group had a KL score of 3 or 4. Outcomes as measured with Forgotten Joint Score (FJS), Knee Society Score (KSS), and Range of motion were compared up to 2-years. Results There were 29 subjects with low-grade KL scores and 127 with high-grade KL scores. There were no differences in BMI, age, or gender distribution. The only statistically significant difference was in the preoperative KSS Pain/Motion score, 60.6 in the low-grade OA group vs. 46.4 in the high-grade group (P&lt;0.008). There were no significant differences between the groups in FJS at one or two-year follow-up. There were no differences in KSS Functional or Composite Scores, or in range of motion (ROM) at pre-op, 1-year or 2-years, and in KSS Pain/Motion at 1 or 2-years. Conclusion There were no significant differences in FJS, KSS, and ROM in patients with low- vs. high-grade OA up to 2-year follow-up. Patients with lower grade OA demonstrated substantial improvements in their FJS, KSS scores, and ROM indistinguishable from the higher-grade OA cohort up to 2-years, suggesting no shorter-term downside to earlier intervention with kinematically-aligned medial-pivot (MP) TKA.

The Viability and Success of Noncemented Kinematic Total Knee Arthroplasty.

The prevalence of noncemented total knee arthroplasty (TKA) is increasing as personalized knee alignment strategies deviate from implanting components on a strict mechanical axis. This retrospective study evaluated the outcomes of 74 consecutive noncemented unrestricted kinematic TKA procedures. This study included 74 consecutive noncemented kinematic TKAs performed by one surgeon at a tertiary academic medical center from 2021 to 2023. The technique used was unrestricted femur-first caliper kinematic TKA. The outcomes included revision, pain scores, and radiographic measurements. Of the 74 procedures performed, there were no revisions or readmissions for problems related to TKA. The mean follow-up was 17.6 months, with 74% of patients being followed up for more than 1 year postoperatively. On the day of surgery, postoperative measurements showed that the average tibial mechanical, distal femoral, and anatomic tibiofemoral angles were 3.3°, 7.7°, and 5.8°, respectively. 5 knees were observed initially with signs of radiolucency, which all resolved by the most recent appointment. None of the knees was radiographically loose. Of the patients, 65%, 19%, and 16% reported no pain, minimal pain, and some pain, respectively, at the 6-week follow-up visit. This improved to 78%, 19%, and 3% at the most recent follow-up. Combining kinematic alignment with noncemented fixation showed excellent clinical and radiographic outcomes with short-term survivorship. Although the use of both kinematic alignment and noncemented TKAs has been controversial, these early data suggest that noncemented kinematic TKA is safe and effective.

Addressing sagittal plane imbalance in primary total knee arthroplasty.

Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies. In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference. FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001). Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue.

CORR Insights®: No Difference in 10-year Clinical or Radiographic Outcomes Between Kinematic and Mechanical Alignment in TKA: A Randomized Trial.

CORR Insights®: No Difference in 10-year Clinical or Radiographic Outcomes Between Kinematic and Mechanical Alignment in TKA: A Randomized Trial.

A Novel Technique for Restricted Kinematic Alignment Total Knee Arthroplasty Without Computer-Assisted Devices

A Novel Technique for Restricted Kinematic Alignment Total Knee Arthroplasty Without Computer-Assisted Devices

No Difference in 10-year Clinical or Radiographic Outcomes Between Kinematic and Mechanical Alignment in TKA: A Randomized Trial.

There is continuing debate about the ideal philosophy for component alignment in TKA. However, there are limited long-term functional and radiographic data on randomized comparisons of kinematic alignment versus mechanical alignment. We present the 10-year follow-up findings of a single-center, multisurgeon randomized controlled trial (RCT) comparing these two alignment philosophies in terms of the following questions: (1) Is there a difference in PROM scores? (2) Is there a difference in survivorship free from revision or reoperation for any cause? (3) Is there a difference in survivorship free from radiographic loosening? Ninety-nine patients undergoing primary TKA for osteoarthritis were randomized to either the mechanical alignment (n = 50) or kinematic alignment (n = 49) group. Eligibility for the study was patients undergoing unilateral TKA for osteoarthritis who were suitable for a cruciate-retaining TKA and could undergo MRI. Patients who had previous osteotomy, coronal alignment > 15° from neutral, a fixed flexion deformity > 15°, or instability whereby constrained components were being considered were excluded. Computer navigation was used in the mechanical alignment group, and patient-specific cutting blocks were used in the kinematic alignment group. At 10 years, 86% (43) of the patients in the mechanical alignment group and 80% (39) in the kinematic alignment group were available for follow-up performed as a per-protocol analysis. The PROMs that we assessed included the Knee Society Score, Oxford Knee Score, WOMAC, Forgotten Joint Score, and EuroQol 5-Dimension score. Kaplan-Meier analysis was used to assess survivorship free from reoperation (any reason) and revision (change or addition of any component). A single blinded observer assessed radiographs for signs of aseptic loosening (as defined by the presence of progressive radiolucent lines in two or more zones), which was reported as survivorship free from loosening. At 10 years, there was no difference in any PROM score measured between the groups. Ten-year survivorship free from revision (components removed or added) likewise did not differ between the groups (96% [95% CI 91% to 99%] for the mechanical alignment group and 91% [95% CI 83% to 99%] for the kinematic alignment group; p = 0.38). There were two revisions in the mechanical alignment group (periprosthetic fracture, deep infection) and four in the kinematic alignment group (two secondary patella resurfacings, two deep infections). There was no statistically significant difference in reoperations for any cause between the two groups. There was no difference with regard to survivorship free from loosening on radiographic review (χ2 = 1.3; p = 0.52) (progressive radiolucent lines seen at 10 years were 0% for mechanical alignment and 3% for kinematic alignment). Like the 2-year and 5-year outcomes previously reported, 10-year follow-up for this RCT demonstrated no functional or radiographic difference in outcomes between mechanical alignment and kinematic alignment TKA. Anticipated functional benefits of kinematic alignment were not demonstrated, and revision-free survivorship at 10 years did not differ between the two groups. Given the unknown long-term impact of kinematic alignment with regard to implant position (especially tibial component varus), we must conclude that mechanical alignment remains the reference standard for TKA. We could not demonstrate any advantage to kinematic alignment at 10-year follow-up. Level I, therapeutic study.

Femoral cartilage thickness measured on MRI varies amongindividuals: Time to deepen one of the principles of kinematic alignment in total knee arthroplasty. A systematic review.

Kinematically aligned total knee arthroplasty (KA TKA), as a pure resurfacing procedure, is based on matching implant thickness with bone cut and kerf thickness, plus cartilage wear. However, the assumption of a consistent 2 mm femoral cartilage thickness remains unproven. This study aimed to systematically review the available literature concerning magnetic resonance imaging (MRI) assessment of femoral cartilage thickness in non-arthritic patients. Our hypothesis was that cartilage thickness values would vary significantly amongindividuals, thereby challenging the established KA paradigm of 'one-cartilage-fits-all'. Systematic literature searches (Pubmed, Scopusand Cochrane Library) followed PRISMA guidelines. English-language studies assessing distal and posterior femoral cartilage thickness using MRI in non-arthritic adults were included. Studies lacking numerical cartilage thickness data, involving post-operative MRI, considering total femoro-tibial cartilage thickness, or failing to specify the compartment of the knee being studied were excluded. Overall, 27 studies comprising 8170 MRIs were analysed. Weighted mean femoral cartilage thicknesses were: 2.05 ± 0.62 mm (mean range 1.06-2.6) for the distal medial condyle, 1.95 ± 0.4 mm (mean range 1.15-2.5) for the distal lateral condyle, 2.44 ± 0.5 mm (mean range 1.37-2.6) for the posterior medial condyleand 2.27 ± 0.38 mm (mean range 1.48-2.5) for the posterior lateral condyle. Femoral cartilage thickness varies significantly across patients. In KA TKA, relying on a fixed thickness of 2 mm may jeopardize the accurate restoration of individual anatomy, leading to errors in implant coronal and rotational alignment. An intraoperative assessment of cartilage thickness may be advisable to express the KA philosophy at its full potential. Level IV.

Kinematic alignment adequately restores trochlear anatomy, patellar kinematics and kinetics in total knee arthroplasty: A systematic review.

Patellofemoral pain, maltrackingand instability remain common and challenging complications after total knee arthroplasty. Controversy exists regarding the effect of kinematic alignment on the patellofemoral joint, as it generally leads to more femoral component valgus and internal rotation compared to mechanical alignment. The aim of this systematic review isto thoroughly examine the influence of kinematic alignment on the third space. A systematic search of the Pubmed, Cochraneand Web of Science databases was performed to screen for relevant articles published before 7 April 2024. This led to the final inclusion of 42 articles: 2 cadaveric, 9radiographic, 12 computer simulationand 19 clinical studies. The risk of bias was evaluated with the risk of bias in non-randomised studies - of interventions tool as the lowest level of evidence of the included clinical studies was IV. The effects of kinematic alignment on patellar kinematics and kinetics, trochlear anatomy reconstructionand patellofemoral complication rate were investigated. Kinematic alignment closely restores native patellar kinematics and kinetics,better reproduces native trochlear anatomy than mechanical alignment and leads to a 0%-11.4% incidence of patellofemoral complications. A more valgus joint line of the distal femur can cause lateral trochlear undercoverage and a trochlear angle orientation medial to the quadriceps vector when applying kinematic alignment, both of which can be solved by using an adjusted design with a 20.5° valgus trochlea. Kinematic alignment appears to be a safe strategy for the patellofemoral joint in most knees, provided that certain precautions are taken to minimize the risk of complications. Level IV clinical studies, in vitro research.

'Extended' restricted kinematic alignment results in decreased residual medial gap tightness among osteoarthritic varus knees during robotic-assisted total knee arthroplasty.

The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases. Patients who underwent RA-TKA between January and December 2022 for primary varus osteoarthritis were included. Safe boundaries for E-rKA were defined. Residual medial compartment tightness was compared following virtual surgical planning using E-rKA and MA, in the same set of knees. Soft-tissue releases were documented. Errors in postoperative alignment in relation to planned alignment were compared between patients who did (group A) and did not (group B) require soft-tissue releases. The use of E-rKA helped restore all knees within the predefined boundaries, with appropriate soft-tissue balancing. E-rKA compared with MA resulted in reduced residual medial tightness following surgical planning, in full extension (2.71 mm (SD 1.66) vs 5.16 mm (SD 3.10), respectively; p < 0.001), and 90° of flexion (2.52 mm (SD 1.63) vs 6.27 mm (SD 3.11), respectively; p < 0.001). Among the study population, 156 patients (78%) were managed with minor adjustments in component positioning alone, while 44 (22%) required additional soft-tissue releases. The mean errors in postoperative alignment were 0.53 mm and 0.26 mm among patients in group A and group B, respectively (p = 0.328). E-rKA is an effective and reproducible alignment strategy during RA-TKA, permitting a large proportion of patients to be managed without soft-tissue releases. The execution of minor alterations in component positioning within predefined multiplanar boundaries is a better starting point for gap management than soft-tissue releases.