Modified kinematic alignment better restores plantar pressure distribution than mechanical alignment in total knee arthroplasty: a randomized controlled trial

To identify, synthesise and critically appraise the findings of meta-analyses that compare patient-reported outcome measures (PROMs) between unrestricted kinematic alignment and mechanical alignment in total knee arthroplasty (TKA). It was hypothesised that some meta-analyses inaccurately combine PROMs from unrestricted and restricted kinematic alignment techniques. Two authors independently screened articles based on inclusion and exclusion criteria and assessed the methodological quality based on the 16 domains of A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2). Effect sizes of difference in PROMs were tabulated for each meta-analysis. Studies included in the meta-analyses were assessed to determine if they were on true unrestricted kinematic alignment. A secondary meta-analysis excluded studies on restricted kinematic alignment techniques, to recalculate pooled estimates (mean difference (MD) with their 95% confidence interval (CI)) of the Knee Society Score (KSS), Oxford Knee Score (OKS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Forgotten Joint Score (FJS). The quality of evidence was assessed using the GRADE. There were 15 meta-analyses pooling data from 39 clinical studies eligible for data extraction. None fulfilled all seven critical AMSTAR-2 domains. Some reported kinematic alignment yielded superior KSS (Function, n = 9; Knee, n = 6: Combined, n = 8), OKS (n = 7), WOMAC (n = 8) and FJS (n = 1). The secondary meta-analysis included only studies on unrestricted kinematic alignment and results at the latest follow-up, for which the mean and standard deviations were reported and revealed no difference in KSS, OKS, WOMAC or FJS between kinematic and mechanical alignment. GRADE analysis revealed 'very low' quality of evidence for KSS, WOMAC and FJS, while it was 'low' quality for OKS. Current evidence suggests no difference in PROMs between kinematic and mechanical alignment in TKA. Meta-analyses that report the contrary often need more rigour as they pool studies on various kinematic alignment techniques or represent the same cohort at different times. Orthopaedic societies should promote using objective outcome measures to evaluate and compare alignment techniques. Systematic review protocol registration (Prospero: CRD42023434713). Level III.

Functional, patient-reported, and radiographic outcomes of kinematic versus mechanical alignment in robotic total knee arthroplasty: A systematic review and meta-analysis.

This study aims to evaluate the clinical and radiological outcomes of a modified technique of Kinematically Aligned Total Knee Arthroplasty (KA TKA) using a cruciate sacrificing (CS) medially stabilised prosthesis at a minimum 24-months follow-up. 59 patients with a varus HKA angle who underwent a TKA from May, 2016 to April, 2017 were retrospectively enrolled. Radiological and clinical evaluations were assessed after 40days, 6months and at a minimum follow-up of 24months. Long leg standing X-rays were performed pre-operatively and the Hip-Knee-Ankle (HKA) angle, the mechanical Lateral Distal Femoral Angle (mLDFA), the mechanical Medial Proximal Tibial Angle (mMPTA) and the Knee Joint Line Obliquity Angle (KJLOA) were analysed. At a minimum follow-up of 24months, the patients were evaluated subjectively based on the Western Ontario and McMaster Universities Osteoarthritis Index Score (WOMAC) and the Oxford Knee Score (OKS). The post-operative range of motion (ROM) was measured. To reduce flexion instability, an original technique was used, with more posterior positioning of the femoral component, called the "virtuous mistake". Results were compared to the data reported in the literature in patients treated with standard kinematic alignment (KA) technique. No difference was found between the mean pre-operative and post-operative angles regarding mLDFA (p value = 0.410) and mMTPA (p value = 0.242). A difference of 0.8° in HKA angle between males and females was found, with more varus results in males. At a minimum follow-up of 24months, the WOMAC was 87 (SD 4.3), the OKS was 41 (SD 2.4), and the flexion was 124°, which was similar to the data reported in literature with standard KA. There were not any cases of aseptic failures. The modified KA TKA surgical technique proposed in this study can achieve good clinical results at minimum 24months of follow-up, reproducing accurately native mLDFA and mMPTA. Level III, therapeutic study.

BackgroundRestricted Kinematic Alignment (rKA) is a well-established technique for total knee arthroplasty (TKA) that aims to approximate natural knee motion within defined safety boundaries. This meta-analysis aims to evaluate the clinical efficacy of rKA compared to mechanical alignment (MA) in TKA.MethodA comprehensive search was conducted in the PubMed, Embase, Web of Science, and Cochrane Library databases for randomized controlled trials (RCTs) published from the inception of these databases until December 6, 2024. RCTs assessing the clinical efficacy of rKA and MA in TKA were included. A total of six RCTs were analyzed.ResultsA total of six RCTs involving 444 patients were included in the analysis. The meta-analysis revealed that the Knee Society Score (KSS) and McMaster Universities Osteoarthritis Index (WOMAC) scores were significantly higher in the rKA group compared to the MA group. However, no significant differences were found between the rKA and MA groups in terms of the Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score (FJS), hip-knee-ankle angle (HKA), and lateral distal femoral angle (LDFA). Additionally, the postoperative revision rate in the rKA group was not significantly different from that in the MA group.ConclusionThis study suggests that rKA provides better functional outcomes in TKA compared to MA, particularly in terms of WOMAC score and KSS.Clinical trial numberNot applicable.

BackgroundDespite potential for improving patient outcomes, studies using three-dimensional measurements to quantify proximal tibial sclerotic bone and its effects on prosthesis stability after total knee arthroplasty (TKA) are lacking. Therefore, this study aimed to determine: (1) the distribution range of tibial sclerotic bone in patients with severe genu varum using three-dimensional measurements, (2) the effect of the proximal tibial sclerotic bone thickness on prosthesis stability according to finite-element modelling of TKA with kinematic alignment (KA), mechanical alignment (MA), and 3° valgus alignment, and (3) the effect of short extension stem augment utilization on prosthesis stability.MethodsThe sclerotic bone in the medial tibial plateau of 116 patients with severe genu varum was measured and classified according to its position and thickness. Based on these cases, finite-element models were established to simulate 3 different tibial cut alignments with 4 different thicknesses of the sclerotic bone to measure the stress distribution of the tibia and tibial prosthesis, the relative micromotion beneath the stem, and the influence of the short extension stem on stability.ResultsThe distribution range of proximal tibial sclerotic bone was at the anteromedial tibial plateau. The models were divided into four types according to the thickness of the sclerotic bone: 15 mm, 10 mm, 5 mm, and 0 mm. The relative micromotion under maximum stress was smallest after MA with no sclerotic bone (3241 μm) and largest after KA with 15 mm sclerotic bone (4467 μm). Relative micromotion was largest with KA and smallest with MA in sclerotic models with the same thickness. Relative micromotion increased as thickness of the sclerotic bone increased with KA and MA (R = 0.937, P = 0.03 and R = 0.756, P = 0.07, respectively). Relative micromotion decreased with short extension stem augment in the KA model when there was proximal tibial sclerotic bone.ConclusionsThe influence of proximal tibial sclerotic bone on prosthesis’s stability is significant, especially with KA tibial cut. Tibial component’s short extension stem augment can improve stability.

The Impact of Mechanical and Restricted Kinematic Alignment on Knee Anatomy in Total Knee Arthroplasty

The purpose of this study was to assess whether kinematic alignment (KA) outperforms mechanical alignment (MA) in restoring patellar tracking to native patterns by using a clustering algorithm. Twenty cadavers (40 knees) were evaluated. For each cadaver, one knee was randomly assigned to KA and the other to MA. KA total knee arthroplasty (TKA) procedures were performed using a caliper-verified technique, while MA TKA procedures utilized a measured resection technique. Subsequently, all specimens were mounted on a customized knee-testing system, and patellar tracking was measured using a motion analysis system. All patellar tracking data were clustered using the density-based spatial clustering of applications with noise algorithm. Differences in patellar tracking patterns and the restoration of native patellar tracking were compared between the two alignment strategies. Patellar tracking patterns following KA were considerably different from MA. Pre- and post-TKA patellar tracking patterns following MA were grouped into separate clusters, whereas a substantial proportion of patellar tracking patterns following KA were grouped into the pre-TKA dominant cluster. Compared to MA, a greater proportion of patellar tracking patterns following KA showed similar patterns to native knees (p < 0.05) and more patellar tracking patterns following KA paired with preoperative patterns (p < 0.01). KA restored native patellar tracking patterns more closely compared to MA. Level I, therapeutic study.

The knowledge of new technologies and current concepts are primordial in orthopaedic surgery. That is necessary to progress and improve our current practice continuously. This special issue of SICOT-J about hip and knee arthroplasty consists of 12 original articles on orthopaedic advances or controversial subjects, such as robotic-assisted surgeries, alignment of total knee arthroplasty (TKA), cementless tibial implants, polyethylene or ceramic in total hip arthroplasty, return to sport and arthroplasty… Kouyoumdjian et al. reported the current concepts in robotic-assisted total hip arthroplasty. The advantages and the impact of robotic-assisted surgery in knee arthroplasty has been often described in recent literature. Nevertheless, the impact of robotic-assisted system for hip arthroplasty is less known. This paper brings a clear state of knowledge about this new technology [1]. The materials used in total hip arthroplasty remain a relevant issue. In a comparative study on highly cross-linked polyethylene (XLPE) and ultra-high molecular weight polyethylene (UHMWPE), Carli et al. showed that annual linear wear rates were significantly higher with UHMWPE (0.21 mm/year) compared to XLPE (0.05 mm/year) in a simple mobility in total hip arthroplasty [2]. XLPE coupled with oxidized zirconium femoral heads had minimal wear and no osteolysis at 10-year follow-up. In a relevant update, Langlois and Hamadouche reported the major and recent knowledges on crosslinked polyethylene in total hip arthroplasty [3]. While Bauwens et al. reported the earlier results of ceramic-on-ceramic bearing in total hip arthroplasty by direct anterior approach [4]. Neri et al., described with a pragmatic way the tips and tricks of the dual mobility in total hip arthroplasty [5]. This article brings interesting and relevant advices and concepts to improve the right use of dual mobility. The surgical approach in total hip arthroplasty can also evolve, but this evolution can become difficult according to the complexity of surgical techniques. Foissey et al. have described the learning curve of the anterior approach in total hip arthroplasty according to the surgeon experience [6]. Five published articles reported interesting results about knee arthroplasty. Pacoret et al. described the survival rate of the tibial component in cementless TKA at a mean follow-up of 8 years, with a minimal follow-up of 5 years [7]. Indeed, it is now accepted that cementless implantation of the femoral component provides equivalent results to cemented one, however, the optimal fixation method of the tibial component remains controversial. This comparative study reports a very satisfying survival rate in both groups cemented and cementless TKA. In addition to implants fixation, two articles introduce the impact of alignment in TKA. In a systematic review, Sappey-Marinier et al. assessed five prospective randomized controlled trials comparing clinical and radiological outcomes, and complications in TKA with kinematic alignment and mechanical alignment [8]. Kinematic alignment in TKA achieved clinical and radiological results similar to those of mechanical alignment. The complication rate was not increased. Assi et al. were warning that the intra-medullary guide can yield sub-optimal corrections, particularly for severe tibial varus in TKA [9]. The osteotomies around the knee can impact the surgical strategy of TKA and their outcomes. In a relevant systematic review, Luceri et al. reported the results of five useful studies on TKA after distal femoral osteotomy [10]. They concluded on the complexity of this surgery and the need of specific technical tips and tricks to obtain an accurate knee balancing. But future prospective studies and comparative trials are yet necessary to address the impact of distal femoral osteotomy in knee replacement surgery. In the last study, Plassard et al. described the return to sport after TKA and assessed its predictive factors in a large cohort of TKA [11]. Preoperative condition and activity are the two most significant predictive factors for return to sport. The current concepts and innovations can also settle in the treatment of prosthetic-joint infection. In a didactic article, Ferry et al. described the medical innovations to maintain the function in patients with chronic prosthetic-joint infection for whom explantation is not desirable: phage therapy and phage lysins [12]. There is no doubt that these technologies and current concepts are here to stay and as they improve, they will change the operating theatre of the future and the outcomes for our patients. We hope that you will enjoy reading this special issue of SICOT-J about hip and knee arthroplasty. Good reading.

➢ Adherence to accepted definitions of the various alternative total knee arthroplasty alignment strategies is important for research and communication between surgeons.➢ Technological advances, including robotics and navigation-assisted systems, have made precise execution of alternative alignment strategies feasible.➢ Modern studies have suggested that minor deviations (±3°) from neutral mechanical alignment do not significantly impact long-term total knee arthroplasty implant survivorship.➢ Individualized alignment strategies, such as kinematic, restricted kinematic, and functional alignment, aim to respect native anatomy and soft-tissue balance.➢ The majority of studies comparing intermediate-term outcomes of kinematic and mechanical alignment suggest noninferior outcomes with kinematic alignment; however, some studies have suggested superior outcomes with kinematic alignment.

Most of the population has different degrees of natural varus or valgus knee. Mechanical alignment, the most widely used in total knee arthroplasty, however, does not fully follow this physiological variation. Neutral alignment in coronal plane is considered as goal in mechanical alignment. Some authors speculated that this may have something to do with the lower satisfaction rate after total knee replacement. Kinematic alignment, which focuses more on the articular topography of the natural knee joint, emerged in this context. As this method may reduce soft tissue release, improve knee function and patient satisfaction. Therefore, it has received widespread attention in recent years. The author’s hospital is one of the earliestinstitutions in China to perform kinematic alignment in total knee replacement using patient-specific instrumentation. This review summarized the technology’s preoperative planning, pearls and pitfalls in surgical techniques, relevant basic theories, and clinical evidences, so as to help readers fully understand kinematic alignment. Key words: Arthroplasty, replacement, knee; Mechanics

A retrospective comparison of Coronal Plane Alignment of the Knee

While the number of primary TKAs completed in the United States is expected to increase dramatically in the years to come, approximately 20% of patients undergoing primary TKA are dissatisfied with the procedure [5, 11]. As such, substantial healthcare resources have been devoted to the development and use of patient-specific instrumentation (PSI), computer navigation, robotics, and other tools that help achieve a neutrally aligned TKA in the coronal plane [1, 2, 14]. On the other hand, some investigators support a different approach: The concept of a kinematically aligned TKA [6, 8–10]. In general terms, a neutrally aligned TKA cuts the distal femur and proximal tibia 90° to the respective mechanical axes, while a kinematically aligned TKA incorporates 3° of varus into the tibia and an additional 3° of valgus into the femur. However, there remains considerable controversy in this area, in large measure because of a relative paucity of research comparing the approaches. As such, I have invited two internationally known experts to discuss these two approaches to obtaining a well-aligned TKA – the neutrally aligned and kinematically aligned techniques.

Kinematic alignment is bone and soft tissue preserving compared to mechanical alignment in total knee arthroplasty

The purpose of this study was to compare 2 alignment methods for total knee arthroplasty (TKA): kinematic alignment with the use of patient-specific guides and mechanical alignment with conventional instruments. A randomized, controlled trial of 41 kinematically aligned and 41 mechanically aligned patients was conducted with the patient, radiographic evaluator, and clinical evaluator blinded to the alignment technique. Radiographic measurements were made from long-leg computer tomography scanograms. Clinical outcome scores and motion were measured preoperatively and 6 months postoperatively. The hip-knee-ankle angle (0.3° difference; P=.693) and anatomic angle of the knee (0.8° difference; P=.131) were similar for both groups. In the kinematically aligned group, the angle of the femoral component was 2.4° more valgus (P<.000) and the angle of the tibial component was 2.3° more varus (P<.000) than the mechanically aligned group. At 6 months postoperatively, the Western Ontario and McMaster Universities Osteoarthritis Index score was 16 points better (P<.000), Oxford Score was 7 points better (P=.001), combined Knee Society Score was 25 points better (P=.001), and flexion was 5.0° greater (P=.043) in the kinematically aligned group than in the mechanically aligned group.Our findings suggest that the risk of early failure related to limb or knee alignment should be similar in kinematic and mechanically aligned TKA. More anatomic alignment of the implant was associated with better flexion and better clinical outcome scores in the kinematically aligned group.

Background/Objectives: Mechanical neutrality has long been regarded as the principal alignment target in total knee arthroplasty (TKA). However, radiographic neutrality does not necessarily reflect physiological morphology or patient perception. This study aimed to evaluate one-week postoperative patient-perceived lower-limb straightness after unrestricted kinematic alignment (KA) TKA and to examine its relationship with radiographic alignment parameters and functional findings. Methods: A total of 175 patients (203 knees) who underwent unrestricted KA-TKA were retrospectively reviewed. Pre- and postoperative radiographs, clinical assessments, and a study-specific, non-validated questionnaire were analyzed one week postoperatively. Patient perception of straightness was assessed using the Straightness Visual Analog Scale (S-VAS) and the Straightness Satisfaction Visual Analog Scale (SS-VAS). Radiographic parameters included the hip-knee-ankle angle (HKAA), the medial proximal tibial angle (MPTA), the mechanical lateral distal femoral angle (mLDFA), the joint line convergence angle (JLCA), and Coronal Plane Alignment of the Knee (CPAK) patterns. Correlative analyses between VAS scores and radiographic and clinical parameters were examined. Results: Preoperatively, 85% of knees were perceived as bowed, and all were reported as straight after surgery. Among knees not perceived as bowed preoperatively, 60% were newly perceived as straight postoperatively, while 40% remained perceived as straight. Postoperative satisfaction was high (S-VAS 88.9 ± 11.6; SS-VAS 92.3 ± 12.9). Associations between S-VAS/SS-VAS and HKAA were weak but statistically significant, whereas both showed moderate positive correlations with postoperative knee extension (S-VAS r = 0.54; SS-VAS r = 0.59). Conclusions: At one week after surgery, patients tended to perceive lower-limb straightness as being associated with restoration of physiological morphology and improved knee extension rather than with radiographic mechanical neutrality. Patient-perceived straightness reflects an individualized and natural sense of limb alignment ("inherent straightness") and should be interpreted as an exploratory, patient-centered concept based on an early postoperative test, supporting a personalized framework for alignment evaluation in unrestricted KA-TKA.