A bicruciate retaining (BCR) TKA is thought to maintain a closer resemblance to the native knee kinematics compared to a posterior cruciate retaining (CR) TKA. With BCR TKAs retainment of the anterior cruciate ligament (ACL) facilitates proprioception and balance which is thought to lead to more natural knee kinematics and increased functional outcome. The aim of this study was to quantify and compare the kinematics of a BCR and CR TKA during functional tests. In this patient-blinded randomized controlled trial, a total of 40 patients with knee osteoarthritis were included, 18 of them received a BCR TKA (Vanguard XP, Zimmer-Biomet) and 22 received a CR TKA (Vanguard CR, Zimmer-Biomet). Fluoroscopic analysis was done 1 year post-operatively. The main outcome was posterior femoral rollback (i.e. translation of the femorotibial contact point (CP)) of the BCR and CR TKA during a step-up test. Secondary, the kinematics during a lunge test were quantified as anterior-posterior (AP) translation of the femorotibial CP. Independent student t-tests (or non-parametric equivalent) were used to analyze the effect of BCR versus CR TKA on these measures, to correct for the multiple testing problem post-hoc Bonferroni-Holm corrections were applied.Introduction
Materials and Methods
The cruciate ligaments are important structures for biomechanical stability of the knee. For total knee arthroplasty (TKA), understanding of the exact function of the (PCL) and anterior (ACL) cruciate ligament during walking is important in the light of recent designs of bicruciate TKAs. However, studies evaluating in vivo function of the PCL during daily activities such as walking are scarce. We aimed to assess the role of the PCL during gait by measuring kinematics and kinetics of individuals with PCL deficiency and compare them with individuals with ACL deficiency and healthy young adults. Individuals with unilateral PCL deficiency (PCLD; n=9), unilateral ACL deficiency (n=10) and healthy young adults performed (n=10) 10 walk trials (5 for each leg) in which they walked over a force platform. Motion analysis (Vicon Motion Capture System) was used to calculate joint angles and internal moments around the knee, hip and ankle in the sagittal plane. Joint angles and moments of the injured knee (in PCLD and ACLD) or left knee (in HYA) were compared between groups at weight acceptance, mid-stance and push-off phases (see Fig. 1). Clinical assessment included passive knee laxity (Kneelax) for anterior (in 20–30° knee flexion) and posterior tibia translation (in 70–90° knee flexion) and Lysholm questionnaires.Background
Methods
The number of revisions of total knee replacements (TKR) increases annually. Because of reduced bone stock, stable fixation of the implant is important. The femoral and tibial components are usually cemented whereas stems can be placed either cemented or press-fit (hybrid construct). To assess the stability of revision TKR with either cemented or hybrid places implants a randomized controlled trial (RCT) was executed, by using radiostereometric analysis (RSA). The short-term results of this RCT showed no differences between the two groups in stability and clinical outcomes. Although there were no clinical or radiological signs of loosening, both groups showed implants micromotion > 1 mm or degree. These findings might indicate the possibility of loosening later in time; therefore, the current study investigated the stability of cemented versus hybrid-placed revision TKR 6.5 years after surgery. Additionally, clinical results were evaluated. Of the 32 patients in the original RCT, 23 (12 cement, 11 press-fit) were available for mid-term follow-up measures. RSA images taken at baseline, 6 weeks, 3, 6, 12 and 24 months postoperatively were used from the previous study. New RSA images were taken at median 6.5 years (range 5.4–7.3) postoperatively. Stability of the femoral and tibial implants was assessed by using model-based RSA software (RSAcore, Leiden, The Netherlands) to determine micromotion. Clinical results were evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), active flexion, and VAS pain and satisfaction. Stability and clinical outcome were compared between the two groups using independent t-tests or Mann-Whitney U tests when applicable.Introduction
Methods
Tibial slope was shown to majorly affect the outcomes of Total Knee Arthroplasty (TKA). More slope of the tibial component could help releasing a too tight flexion gap in cruciate-retaining (CR) TKA and is generally associated with a wider range of post-operative knee flexion. However, an excessive tibial slope could jeopardize the knee stability in flexion. The mechanism by which tibial slope affects the function of CR-TKA is not well understood. Moreover, it is not known whether the tibial bone resection should be performed by referencing the anterior cortex (AC) of the tibia or the center of the tibial plateau (CP) and whether the choice of either technique plays a role. The aim of this study was to investigate the effect of tibial slope on the position of tibiofemoral (TF) contact point, knee ligament forces, quadriceps muscle forces, and TF and patellofemoral (PF) joint contact forces during squat activity in CR-TKA. A previously validated musculoskeletal model of CR-TKA was used to simulate a squat activity performed by a 86-year-old male subject wearing an instrumented prosthesis [1,2]. Marker data over four consecutive repetitions of a squat motion were tracked using a motion optimization algorithm. Muscle and joint forces and moments were calculated from an inverse-dynamic analysis, coupled with Force-Dependent Kinematics (FDK) to solve knee kinematics, ligament and contact forces simultaneously. The tibial slope in the postoperative case was 0 degree and constituted the reference case for our simulations. In addition, eight additional cases were simulated with −3, +3, +6, +9 degrees of tibial slope, four of them simulating an AC referencing technique and four a CP technique.Introduction
Methods
To improve implant positioning in total knee arthroplasty (TKA) patient-specific instrumentation (PSI) has been introduced as alternative for conventional instrumentation (CI). Though the PSI technique offers interesting opportunities in TKA, there is no consensus about the effectiveness of PSI in comparison with CI and results concerning soft-tissue balancing remain unclear. Therefore, the primary aim of the present study was to investigate the varus-valgus laxity in extension and flexion in patients receiving a TKA using PSI compared with CI. Additionally, radiological, clinical and functional outcomes were assessed. In this prospective randomization controlled trial, 42 patients with osteoarthritis received a Genesis II PS (Smith & Nephew, Memphis, Tennessee), with either PSI (Visionaire, Smith & Nephew) or CI (Smith & Nephew). Patients visited the hospital preoperative and postoperative after 6 weeks, 3 and 12 months. One-year postoperative varus-valgus laxity was measured in extension and flexion on stress radiographs. Additional assessments included: the hip-knee-ankle angle on long-leg radiographs, femoral and tibia component rotation on CT-scans, radiolucency, the Knee Society Score (KSS), VAS pain, VAS Satisfaction, Knee injury and Osteoarthritis Outcome score (KOOS), Patella score (Kujala), the University of California Los Angeles activity score (UCLA), the anterior-posterior laxity in 20° and 90° knee flexion, adverse events and complications. The outcome measures were compared using independent t-tests, non-parametric alternatives and repeated measurements, with a significance level of p<0.05.Background
Methods
Measuring the step off during total knee replacement (TKR) is a newly developed operative strategy (“spacer technique”; Heesterbeek et al, KSSTA 2014;22(3):650–9) to determine the optimal contact point (CP) of the femur with the tibia postoperative and to balance the posterior cruciate ligament (PCL) in cruciate-retaining TKR. Engineers have calculated the ideal step off for every size of the TKR, for which the tibiofemoral contact point in 90° will be at the designed position. With this study we determined the postoperative CP in CR-TKA and investigated whether (adverse) clinical outcome was correlated with the CP. 23 patients presenting with non-inflammatory osteoarthritis, a good functioning PCL, and indication for surgery with a PCL-retaining TKR were selected. Intraoperative PCL balancing was performed with the spacer technique. At 3 months postoperative, a pair of mediolateral radiographs was made using a set-up used for radiostereometric analysis (RSA). The patient was positioned standing with the operated leg in 90 degrees, 50% weight-bearing, knee flexion on a 30 cm-step. Model-based RSA software (RSAcore) was used to determine the 3D positions of the femur and tibia component, that were exported to custom-written software for determining the CP. The CP was defined as the point with the smallest distance between both the medial and lateral femur condyles and tibia plateau. It is expressed as the ratio of the anterior-posterior CP distance and the maximum anterior-posterior tibia plateau size, with 0 being anterior, 1 being posterior. Patients with reduced flexion capacity at follow-up, leading to manipulation under anaesthesia and/or scopic releases, were categorized as COMP, the other patients as no-COMP. CP was compared between these groups.Introduction
Methods
Total knee arthroplasty (TKA) is a cost-effective surgical procedure for degenerative knee disease and has good long-term results. However, these results are not always related to patient satisfaction and functional outcome. With an increasing demand of surgeons and patients on functioning of total knee implants, the need for adequate objective outcome measures is high. Imaging of the knee is commonly used in clinical practice and research to objectively measure many different outcome parameters concerning the implant, such as alignment and complications.1 However, techniques on comparison of the sagittal contour of the knee before and after implant placement are scarce. To develop and describe a standardized method for measuring the sagittal contour of the implant in a 3D model of the knee before and after implant placement.Background
Goal
Total knee arthroplasty can be performed with the balanced gap technique with the tibia cut first guided by the use of a tensor. In a case series of 54 cruciate retaining knee implants (Balansys) 150 N tension was applied to distract the extension gap and 100 N to distract the flexion gap. The following conclusions could be drawn from the collected data: The varus valgus laxity of the total knee joint measured with stress radiograms in extension was similar to that of the healty subjects with the same age and in flexion one degree more. The anterior posterior laxity of the total knee joints compared to the healthy knees was on average 1 mm less. The average ROM of the total knee joints was 118 degrees versus 130 degrees for the healthy knees Ligament releases did not have a significant influence on the stability of the total knee joints. The femur rotation guided by the ligament tension in flexion varied from −4 degrees to + 10 degrees referenced from the posterior condylar line. Only knees with a large medial ligament release had on average slighly less external rotation. Patella position after surgery was not affected by this variable femoral component rotation, only preoperative maltracking was a predictor of postoperative maltracking. One millimeter distraction of the flexiongap causes 1.9–2.3 mm anterior translation of the tibia indicating that very small gap changes in CR knee can cause a relative large shift of the contact point showing the difficulty to balance the PCL. In conclusion the balanced gap technique with a tensor system results in very stable total knee implants with good range of motion. This tensor technique in cruciate retaining total knee arthroplasty is safe even when releases are performed. The variable femur rotation did not affect patella tracking.
