Aims

The Advance Medial-Pivot total knee arthroplasty (TKA) was designed to reflect contemporary data regarding the kinematics of the knee. We wished to examine the long-term results obtained with this prosthesis by extending a previous evaluation.

Abstract

Aims. Medial pivot (MP) total knee arthroplasties (TKAs) were designed to mimic native knee kinematics with their deep medial congruent fitting of the tibia to the femur almost like a ball-on-socket, and a flat lateral part. GMK Sphere is a novel MP implant. Our primary aim was to study the migration pattern of the tibial tray of this TKA. Methods. A total of 31 patients were recruited to this single-group radiostereometric analysis (RSA) study and received a medial pivot GMK Sphere TKA. The distributions of male patients versus female patients and right versus left knees were 21:10 and 17:14, respectively. Mean BMI was 29 kg/m. 2. (95% confidence interval (CI) 27 to 30) and mean age at surgery was 63 years (95% CI 61 to 66). Maximum total point motions (MTPMs), medial, proximal, and anterior translations and transversal, internal, and varus rotations were calculated at three, 12, and 24 months. Patient-reported outcome measure data were also retrieved. Results. MTPMs at three, 12, and 24 months were 1.0 mm (95% CI 0.8 to 1.2), 1.3 mm (95% CI 0.9 to 1.7), and 1.4 mm (0.8 to 2.0), respectively. The Forgotten Joint Score was 79 (95% CI 39 to 95) and Knee Injury and Osteoarthritis Outcome Score obtained at two years was 94 (95% CI 81 to 100), 86 (95% CI 75 to 93), 94 (95% CI 88 to 100), 69 (95% CI 48 to 88), and 81 (95% CI59 to 100) for Pain, Symptoms, Activities of Daily Living, Sport & Recreation, and Quality of Life, respectively. Conclusion. In conclusion, we found that the mean increase in MTPM was lower than 0.2 mm between 12 and 24 months and thus apparently stable. Yet the GMK Sphere had higher migration at one and two years than anticipated. Based on current RSA data, we therefore cannot conclude on the long-term performance of the implant, pending further assessment. Cite this article: Bone Jt Open 2021;2(9):737–744

Aims

Between 15% and 20% of patients remain dissatisfied following total knee arthroplasty (TKA). The SAIPH knee system (MatOrtho, Surrey, United Kingdom) is a medial ball and socket TKA that has been designed to replicate native knee kinematics in order to maximize the range of movement, stability, and function. This system is being progressively introduced in a stepwise fashion, with this study reporting the mid-term clinical and radiological outcomes.

Aims. In Asia and the Middle-East, people often flex their knees deeply in order to perform activities of daily living. The purpose of this study was to investigate the 3D kinematics of normal knees during high-flexion activities. Our hypothesis was that the femorotibial rotation, varus-valgus angle, translations, and kinematic pathway of normal knees during high-flexion activities, varied according to activity. Materials and Methods. We investigated the in vivo kinematics of eight normal knees in four male volunteers (mean age 41.8 years; 37 to 53) using 2D and 3D registration technique, and modelled the knees with a computer aided design program. Each subject squatted, kneeled, and sat cross-legged. We evaluated the femoral rotation and varus-valgus angle relative to the tibia and anteroposterior translation of the medial and lateral side, using the transepicodylar axis as our femoral reference relative to the perpendicular projection on to the tibial plateau. This method evaluates the femur medially from what has elsewhere been described as the extension facet centre, and differs from the method classically applied. . Results. During squatting and kneeling, the knees displayed femoral external rotation. When sitting cross-legged, femurs displayed internal rotation from 10° to 100°. From 100°, femoral external rotation was observed. No significant difference in varus-valgus angle was seen between squatting and kneeling, whereas a varus position was observed from 140° when sitting cross-legged. The measure kinematic pathway using our methodology found during squatting a medial pivoting pattern from 0° to 40° and bicondylar rollback from 40° to 150°. During kneeling, a medial pivot pattern was evident. When sitting cross-legged, a lateral pivot pattern was seen from 0° to 100°, and a medial pivot pattern beyond 100°. Conclusion. The kinematics of normal knees during high flexion are variable according to activity. Nevertheless, our study was limited to a small number of male patients using a different technique to report the kinematics than previous publications. Accordingly, caution should be observed in generalizing our findings. Cite this article: Bone Joint J 2018;100-B:50–5

Introduction. Medial pivoting motion of the knee has been widely assumed in total knee arthroplasty (TKA) research, but was not consistently observed in recent studies of in vivo knee motion. This study investigated the in vivo motion characters of the knee by analyzing the axial tibial rotation and tibiofemoral articular contact motion during a weightbearing flexion and a treadmill gait. Methods. In vivo kinematics of eight living human knees during a weightbearing flexion and a treadmill gait was determined using a combined MRI and dual fluoroscopic imaging system technique. The axial tibial rotation and the tibiofemoral cartilage contact point motion on both the tibial plateau and femoral condyle surfaces were analyzed. Results. While internal tibial rotation was observed with flexion of the knee during the two activities, larger excursions of the tibiofemoral contact points were measured on the medial femoral condyle surface than on the lateral side during the weightbearing flexion of the knee. The contact point excursions were also larger on the medial tibial plateau surface than on the lateral side during the treadmill gait. The contact points moved anteriorly with flexion and posteriorly with extension of the knee on the medial tibial surface during the gait, that was opposite to the femoral rollback observed during the weightbearing knee flexion. Conclusion. The data indicates that the in-vivo knee motion is activity- and loading-dependent and cannot be described using a single motion character. The knee could potentially rotate with respect to an axis located at the lateral side of the knee and the traditional “medial pivoting” motion character of the knee was not observed in these in-vivo activities. The data could provide important implications for the improvement of TKA designs and implantation techniques that are aimed to restore normal knee function

Introduction. Inability to reproduce 6-degrees of freedom (6DOF) kinematics, abnormal “paradoxical” anterior femoral translation and loss of normal medial pivot rotation are challenges associated with contemporary posterior cruciate retaining and posterior stabilized total knee arthroplasty (TKA). The removal of the anterior and/or both cruciate ligaments in CR/PS TKA, leading to significant kinematic alteration of the knee joint, has been suggested as one of the potential contributory factors in patients remaining dissatisfied after TKA. Bi-cruciate retaining (BCR) TKA designs allow preservation of both anterior and posterior cruciate ligaments with the potential to replicate normal knee joint kinematics. Physically demanding tasks such as sit-to-stand (STS), and deep lunging may be more sensitive tools for investigating preserved kinematic abnormalities following TKA. This study aims to compare in-vivo kinematics between the operated and the contralateral non-operated knee in patients with contemporary BCR TKA design. Methods. Twenty-nine patients (14 male; 15 female, 65.7±7.7 years) unilaterally implanted with a contemporary BCR TKA design featuring an asymmetric femoral component and independently designed medial and lateral bearings were evaluated. Mean follow-up time after BCR TKA was 12.7±5.1 months. All patients received a computer tomography (CT) scan from the pelvis to the ankles for the creation of 3D surface models of both knees (BCR TKA and non-operated). Patients performed single leg deep lunges and sit-to-stand under a validated dual fluoroscopic imaging system (DFIS) surveillance. Each patient's 2D dynamic fluoroscopic images, corresponding 3D surface bone models (for contralateral non-operated knee) and computer aided design (CAD) implant models (for the BCR TKA implanted knee) were imported into a virtual DFIS environment in MATLAB. An optimization procedure was utilized to perform matching between the 3D surface bone models and the 2D fluoroscopic image outlines. In-vivo 6DOF kinematics of the BCR TKA knees and contralateral non-operated side were quantified and analyzed. Results. When performing the high-flexion lunge, BCR TKA knees demonstrated less average femoral posterior translation (13±4mm) during terminal flexion when compared to the contralateral non-operated knees (16.6±3.7mm) (p=0.001). Similarly, during STS, less femoral rollback was observed (11.6±4.5mm vs 14.4±4.6mm, p<0.04) in BCR TKA knees. Overall, BCR TKA knees partially reproduced a normal “screw-home” motion, demonstrating reduced internal rotation during several intervals of the cycles for strenuous flexion activities. BCR TKA knees demonstrated less internal rotation during high-flexion lunge (4±5.6° vs 6.5±6.1°, p=0.05). Similarly, during STS, less internal rotation was observed (4.5±6° vs 6.9±6.3°, p=0.04, p=0.02, p=0.01, p=0.02) in BCR TKA knees. Conclusion. The BCR TKA design demonstrated asymmetries in flexion-extension and internal-external rotation, suggesting that in-vivo tibiofemoral kinematic parameters are not fully restored in BCR patients during functionally strenuous activities such as single leg deep lunges and sit-to-stand. Further studies are required to elucidate the importance of patient factors, surgical component orientation and implant designs in optimizing in vivo kinematics in patients with BCR TKA. For figures, tables, or references, please contact authors directly

Aims

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.

Introduction. Traditional TKR designs exhibit abnormal and unpredictable kinematics: with posterior subluxation in extension and anterior slide with flexion. These can contribute to restricted knee flexion and reduced quadriceps efficiency. Newer designs attempt to provide “guided motion” with the aim of mimicking normal knee kinematics. The Journey (Smith & Nephew) BCS TKR incorporates both an anterior and a posterior cam/post mechanism while Triathlon PS TKR (Stryker) incorporates a posterior cam/post mechanism. This study compares the in-vivo kinematics of these two designs and compares it with normal knee. Methods. Knee kinematics of 10 patients with Journey-BCS TKR and 11 patients with Triathlon PS TKR; all with excellent clinical outcome (average age: 65) were analysed. Patients underwent fluoroscopic assessment of the knee during a step-up and deep knee bend exercise. 2D fluoroscopic images were recorded. Data was analysed for patella tendon angle (PTA) and contact points using a 3D model fitting technique. This data was compared to normal knee kinematics (n=20). Results. The average maximum KFA achieved by the implant groups was 125° (Journey), 114° (Triathlon) and 141° for the normal group. The average angle of anterior cam/post engagement was 13° knee flexion angle (KFA) and the posterior cam/post mechanism at 45° KFA for Journey and 63° for Triathlon. For the Journey, in the step-up exercise both medial and lateral condylar contact points translated anteriorly with extension. For the lunge both condylar contact points translated posteriorly. Triathlon knees exhibited a medial pivot motion. The PTA for Journey showed a similar trend to normal knees. Conclusions. In the Journey TKR, both anterior and posterior cam-post mechanisms engaged and helped produce consistent femoral translation throughout knee flexion without paradoxical movement. This was similar to normal knee kinematics albeit with slight offset. The Triathlon produced posterior translation but did not completely eliminate paradoxical movement

Aims

Robotic arm-assisted surgery offers accurate and reproducible guidance in component positioning and assessment of soft-tissue tensioning during knee arthroplasty, but the feasibility and early outcomes when using this technology for revision surgery remain unknown. The objective of this study was to compare the outcomes of robotic arm-assisted revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) versus primary robotic arm-assisted TKA at short-term follow-up.

Aims

While mechanical alignment (MA) is the traditional technique in total knee arthroplasty (TKA), its potential for altering constitutional alignment remains poorly understood. This study aimed to quantify unintentional changes to constitutional coronal alignment and joint line obliquity (JLO) resulting from MA.

Aims

Patient dissatisfaction is not uncommon following primary total knee arthroplasty. One proposed method to alleviate this is by improving knee kinematics. Therefore, we aimed to answer the following research question: are there significant differences in knee kinematics based on the design of the tibial insert (cruciate-retaining (CR), ultra-congruent (UC), or medial congruent (MC))?

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal.

Aims

Thresholds of acceptable early migration of the components in total knee arthroplasty (TKA) have traditionally ignored the effects of patient and implant factors that may influence migration. The aim of this study was to determine which of these factors are associated with overall longitudinal migration of well-fixed tibial components following TKA.

Aims

Knee arthroplasty surgery is a highly effective treatment for arthritis and disorders of the knee. There are a wide variety of implant brands and types of knee arthroplasty available to surgeons. As a result of a number of highly publicized failures, arthroplasty surgery is highly regulated in the UK and many other countries through national registries, introduced to monitor implant performance, surgeons, and hospitals. With time, the options available within many brand portfolios have grown, with alternative tibial or femoral components, tibial insert materials, or shapes and patella resurfacings. In this study we have investigated the effect of the expansion of implant brand portfolios and where there may be a lack of transparency around a brand name. We also aimed to establish the potential numbers of compatible implant construct combinations.

Aims

The aims of this study were to investigate the ability to kneel after total knee arthroplasty (TKA) without patellar resurfacing, and its effect on patient-reported outcome measures (PROMs). Secondary aims included identifying which kneeling positions were most important to patients, and the influence of radiological parameters on the ability to kneel before and after TKA.

Aims

This study aims to investigate the effects of posterior tibial slope (PTS) on knee kinematics involved in the post-cam mechanism in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) using computer simulation.

Aims

Vitamin E-infused highly cross-linked polyethylene (E1) has recently been introduced in total knee arthroplasty (TKA). An in vitro wear simulator study showed that E1 reduced polyethylene wear. However there is no published information regarding in vivo wear. Previous reports suggest that newly introduced materials which reduce in vitro polyethylene wear do not necessarily reduce in vivo polyethylene wear. To assist in the evaluation of the newly introduced material before widespread use, we established an in vivo polyethylene wear particle analysis for TKA. The aim of this study was to compare in vivo polyethylene wear particle generation between E1 and conventional polyethylene (ArCom) in TKA.

Aims

The removal of the cruciate ligaments in total knee arthroplasty (TKA) has been suggested as a potential contributing factor to patient dissatisfaction, due to alteration of the in vivo biomechanics of the knee. Bicruciate retaining (BCR) TKA allows the preservation of the cruciate ligaments, thus offering the potential to reproduce healthy kinematics. The aim of this study was to compare in vivo kinematics between the operated and contralateral knee in patients who have undergone TKA with a contemporary BCR design.

Aims

As the population ages, there is projected to be an increase in the level of demand for total knee arthroplasty (TKA) in octogenarians. We aimed to explore whether those aged ≥ 80 years achieved similar improvements in physical function to younger patients while also comparing the rates of length of stay (LOS), discharge to rehabilitation, postoperative complications, and mortality following TKA in older and younger patients.