Abstract. Background. The primary objective of the study is to determine the function outcome and survivorship of
Introduction. In knee biomechanics the concept of the envelope of motion (EOM) has proven to be a powerful method to characterize joint mechanics and the effect of surgical interventions. It is furthermore indispensable for numerical model validation. While commonly used for tibiofemoral kinematics, there is very little report of applying the concept to
Background. Total knee arthroplasty (TKA) surgical techniques attempt to achieve equal flexion and extension gaps to produce a well-balanced knee. Anterior knee pain, which is not addressed by flexion-extension balancing, is one of the more common complaints for TKA patients. The variation in
Many recent knee prostheses are designed aiming to the physiological knee kinematics on tibiofemoral joint, which means the femoral rollback and medial pivot motion. However, there have been few studies how to design a patellar component. Since patella and tibia are connected by a patellar tendon, tibiofemoral and
Introduction. During primary total knee arthroplasty (TKA), surgeons occasionally encounter compromised bone and fixation cannot be achieved using a primary femoral component. Revision knee replacement components incorporate additional features to improve fixation, such as modular connection to sleeves or stems, and feature additional varus-valgus constraint in the post-cam mechanism to compensate for soft tissue laxity. The revision femoral component can be used in place of the primary femur to address fixation challenges; however, it is unclear if additional features of the revision femoral components adversely affect knee kinematics when compared to primary TKA components. The objective of this study was to compare weight-bearing tibiofemoral and
There have been a large number of studies reporting the knee joint force during level walking, however, the data of during deep knee flexion are scarce, and especially the data about patellofemoral joint force are lacking. Deep knee flexion is a important motion in Japan and some regions of Asia and Arab, because there are the lifestyle of sitting down and lying on the floor directly. Such data is necessary for designing and evaluating the new type of knee prosthesis which can flex deeply. Therefore we estimated the
Patellofemoral arthroplasty (PFA) has higher revision rates than total knee arthroplasty (TKA) [Van der List, 2015; Dy, 2011]. Some indications for revision include mechanical failure, patellar mal-tracking, implant malalignment, disease progression and persistent pain or stiffness [Dy, 2011; Turktas, 2015]. Implant mal-positioning can lead to decreased patient satisfaction and increased revision rates [Turktas, 2015]. Morphological variability may increase the likelihood of implant mal-positioning. This study quantifies the morphological variability of the anterior-posterior (AP) and medial-lateral (ML) aspects of the
Introduction. Persistent anterior knee pain, subluxation or dislocation of the patella as well as early aseptic loosening and increased polyethylene wear of the patella implant are common clinical problems after total knee arthroplasty (TKA) which are associated with the patellofemoral joint. In addition to patellar resurfacing, the design of the patellofemoral joint surfaces is attributed a large influence. While for patients without patella resurfacing, the native patella is sliding on the standardized femoral component and therefore the possibility of a reduced surface matching is high, patella resurfacing has been shown to decrease the joint contact area and yield to increased
The LCS RPS knee system is based on the successful LCS mobile bearing prosthesis, and has been introduced with the intention of improving post-operative knee flexion. The aim of this study is to report a high incidence of significant
Introduction. The constitutional knee anatomy in the coronal plane includes the distal femoral joint line obliquity (DFJLO) which in most patients is in slight valgus positioning. Despite this native anatomy, the mechanical positioning of the femoral component during primary total knee arthroplasty (TKA) often ignores the native DFJLO opting to place the femur in a set degree of valgus that varies upon the practitioner's practice and experience. Unfortunately, this technique is likely to generate high rate of distal lateral femoral overstuffing. This anatomical mismatch might be a cause of anterior knee pain and therefore partly explain the adverse functional outcomes of mechanically aligned (MA) TKA. Our study aims at assessing the relationship between constitutional knee anatomy and clinical outcomes of MA TKA. We hypothesized that a negative relationship would be found between the constitutional frontal knee deformity, the distal femoral joint line obliquity, and functional outcomes of MA TKA with a special emphasize on
Introduction. Epidemiologic studies indicate that isolated
Isolated
Purpose Of Study. The in vivo evaluation of
Introduction. Knee arthroplasty is an effective intervention for painful arthritis when conservative measures have failed. Despite recent advances in component design and implantation techniques, a significant proportion of patients experience problems relating to the patella-femoral joint (PFJ). Detailed knowledge of the shape and orientation of the normal and replaced femoral trochlea groove is critical when considering potential causes of anterior knee pain. Furthermore, to date it has proved difficult to establish a diagnosis due to shortcomings in current imaging techniques for obtaining satisfactory coronal plane motion data of the patella in the replaced knee. The aim of this study was to correlate the trochlea shape of normal and replaced knees with corresponding coronal plane PFJ kinematic data. Method. Bony and cartilagenous trochlea geometries from 3T MRI scans of 20 normal healthy volunteers were compared with both anatomical and standard total knee replacements (TKR) and patellofemoral joint replacement (PFJR) geometries. Following segmentation and standardized alignment, the path of the apex of the trochlea groove was measured using customized Matlab software. (Fig1). Next, kinematic data of the 20 normal healthy volunteers (Normal) was compared with that of 20 TKR, and 20 PFJR patients using the validated MAUS. TM. system (Motion Analysis and UltraSound) comprising a 12-camera, motion capture system used to capture images of reflective markers mounted on subjects lower limbs and an ultrasound probe. A mapping between the ultrasound image and the motion capture system allows the ultrasound probe to be used to determine the locations of the patella relative to bony landmarks on the femur during a squat exercise. Results. In normal knees the arc of the trochlear groove apex was orientated progressively laterally for both cartilage and. Neither of these trends were reproduced by any of the knee prostheses. Indeed far from being a laterally directed trochlea groove, both the anatomic TKR and PFJR have a medially orientated trochlea, whilst the TKR showed a neutral straight path (Figure 2). The direction of displacement in the replaced knee is significantly different (opposite) to that of the native knee (p<0.05). The accuracy of the MAUS technique registering the ultrasound images within the motion capture system is 1.84 mm (2 × SD). The three groups showed very different patella tracking patterns which matched the orientation of the underlying trochlea (Figure 3). The sine wave pattern of coronal plane patella motion displayed by the Normal group was not recreated in the TKR or PFJR groups. Movements of the Normal group were significantly different from the TKR group (p=0.03) and the PFJR group (p<0.01), whilst there was no significant difference between the TKR and PFJR groups (p=0.27). Discussion. We present a new, accurate, reliable in vivo technique for measuring 3D
Introduction. Malrotation of the femoral component is a cause of
INTRODUCTION.
Background. The goal of patellofemoral arthroplasty (PFA) is to replace damaged cartilage, and to correct underlying deformities, to reduce pain and prevent maltracking. We aimed to determine how PFA modifies patellar height, tilt, and tibial tuberosity to trochlear groove (TT-TG) distance. The hypothesis was that PFA would correct trochlear dysplasia or extensor mechanism malalignment. Methods. The authors prospectively studied a series of 16 patients (13 women and 3 men) aged 64.9 ± 16.3 years (range, 41 to 86) that received PFA. All knees were assessed pre-operatively and six months post-operatively using frontal, lateral, and ‘skyline’ x-rays, and CT scans to calculate patellar tilt, patellar height and tibial tuberosity–trochlear groove (TT-TG) distance. Results. The inter-observer agreement was excellent for all parameters. (ICC > 0.95). Pre-operatively, the median patellar tilt without quadriceps contraction (QC) was 17.5° (range, 5.3°–33.4°) and with QC was 19.8° (range, 0°–52.0°). The median Caton- Deschamps Index (CDI) was 0.91 (range, 0.80–1.22) and TT-TG distance was 14.5mm (range, 4.0–22.0). Post-operatively, the median patellar tilt without QC was 0.3° (range, −15.3°–9.5°) and with QC was 6.1° (range, −11.5°–13.3°). The median CDI was 1.11 (range, 0.81–1.20) and TT-TG distance was 10.1mm (range, 1.8–13.8mm). Conclusion. The present study demonstrates that, beyond replacing arthritic cartilage, trochlear-cutting PFA improves
Introduction. We have been re-evaluating
Introduction:. Kinematic studies are used to evaluate function and efficacy of various implant designs. Given the large variation between subjects, matched pairs are ideal when comparing competing designs. It is logical to deduce that both limbs in a subject will behave identically during a given motion [1], barring unilateral underlying pathology, thus allowing for the most direct comparison of two designs. It is our goal to determine if this is a valid assumption by assessing whether or not there are significant differences present in the kinematics of left and right knees from the same subject. Gait studies have compared pre-and postoperative implantation kinematics for various pathologies like ACL rupture [2] and osteoarthritis [3, 4]. We designed a study to assess squatting in cadaver specimens. Methods:. Sixteen matched pairs of fresh-frozen cadavers, (Eleven males, five females; aged 71 years [± 10 yrs]) were tested. Each knee, intact, was tested by mounting it on a dynamic, quadriceps-driven, closed-kinetic-chain Oxford knee rig (OKR), which simulated a deep knee bend from full extension to 120° flexion. We chose femoral rollback, tibiofemoral external rotation, tibial adduction,