Is adapted measured resection superior to gap-balancing in determining femoral component rotation in total knee replacement?

Obtaining a balanced flexion gap with correct femoral component rotation is one of the prerequisites for a successful outcome after total knee replacement (TKR). Different techniques for achieving this have been described. In this study we prospectively compared gap-balancing versus measured resection in terms of reliability and accuracy for femoral component rotation in 96 primary TKRs performed in 96 patients using the Journey system. In 48 patients (18 men and 30 women) with a mean age of 65 years (45 to 85) a tensor device was used to determine rotation. In the second group of 48 patients (14 men and 34 women) with a mean age of 64 years (41 to 86), an 'adapted' measured resection technique was used, taking into account the native rotational geometry of the femur as measured on a pre-operative CT scan. Both groups systematically reproduced a similar external rotation of the femoral component relative to the surgical transepicondylar axis: 2.4 (SD 2.5) in the gap-balancing group and 1.7 (SD 2.1) in the measured resection group (p = 0.134). Both gap-balancing and adapted measured resection techniques proved equally reliable and accurate in determining femoral component rotation after TKR. There was a tendency towards more external rotation in the gap-balancing group, but this difference was not statistically significant (p = 0.134). The number of outliers for our 'adapted' measured resection technique was much lower than reported in the literature

Hinged versus CCK revision arthroplasty for the stiff total knee

BACKGROUND: Total knee arthroplasty (TKA) remains the gold standard for end-stage knee osteoarthritis. The prevalence of stiffness after this procedure described in literature varies from 1.3% to 5.3%. The causes of arthrofibrosis after total knee arthroplasty are multifactorial. Revision TKA is a successful procedure when performed for loosening, instability, mechanical implant failure, or infection. The results of revision TKA for idiopathic arthrofibrosis and stiffening are however less favorable. PURPOSE: It has been the authors' impression that the poor results in arthrofibrosis could be in part related to the use of traditional PS or CCK-type revision implants. Our hypothesis is that better results can be achieved in case a rotating hinge design (RHK) is used. The reason could be that RHK designs allow for much more aggressive capsuloligament debridement and therefore more adequate fibrosis removal, while securing optimal implant stability, tibiofemoral rotational freedom, and flexion-extension space stability. The purpose of our study was to investigate in our database whether this hypothesis is correct. METHODS: Retrospectively, 40 patients with the defined range of knee motion were identified. Patients with underlying mechanical malalignment, component malposition, soft-tissue imbalance or infections were excluded. Twenty-two patients received a hinged-type prosthetic device (18 Zimmer RHK, four Stryker RHK) and 18 patients received a less constrained condylar type prosthetic device (17 Legion CCK, one Vanguard CCK). RESULTS: Preoperative data were similar for RHK as CCK-type implants except for knee pain score, which was significantly worse for the RHK group (36 vs 44, p = 0.049). At two years of follow-up, compared to CCK, the RHK group demonstrated significantly better postoperative results for knee function scores (68.9 vs 54.2, p = 0.0015), knee function improvement (22.8 vs 4.8, p = 0.0015), knee pain improvement (26.4 vs 9.4, p = 0.0050), greater maximal flexion (99.9° vs 81.4°, p = 0.0005), better maximal extension (-1.9° vs -6.2°, p = 0.0447), greater flexion gain (35.8° vs 14.2°, p = 0.0002), and greater extension gain (8.6° vs 2.0°, p = 0.0083). CONCLUSION: Our data show that revision arthroplasty of the stiff knee using a rotating hinged device can provide excellent results in selected cases. To date, this is the first study to describe the difference in outcome between revision total knee arthroplasty for idiopathic arthrofibrosis using a hinged or a constrained condylar knee device.status: publishe

Anteroposterior positioning of the tibial component and its effect on the mechanics of patellofemoral contact.

The biomechanics of the patellofemoral joint can become disturbed during total knee replacement by alterations induced by the position and shape of the different prosthetic components. The role of the patella and femoral trochlea has been well studied. We have examined the effect of anterior or posterior positioning of the tibial component on the mechanisms of patellofemoral contact in total knee replacement. The hypothesis was that placing the tibial component more posteriorly would reduce patellofemoral contact stress while providing a more efficient lever arm during extension of the knee. We studied five different positions of the tibial component using a six degrees of freedom dynamic knee simulator system based on the Oxford rig, while simulating an active knee squat under physiological loading conditions. The patellofemoral contact force decreased at a mean of 2.2% for every millimetre of posterior translation of the tibial component. Anterior positions of the tibial component were associated with elevation of the patellofemoral joint pressure, which was particularly marked in flexion > 90°. From our results we believe that more posterior positioning of the tibial component in total knee replacement would be beneficial to the patellofemoral joint.Journal Articleinfo:eu-repo/semantics/publishe

Is there a biomechanical explanation for anterior knee pain in patients with patella alta? influence of patellar height on patellofemoral contact force, contact area and contact pressure.

The purpose of this study was to test the hypothesis that patella alta leads to a less favourable situation in terms of patellofemoral contact force, contact area and contact pressure than the normal patellar position, and thereby gives rise to anterior knee pain. A dynamic knee simulator system based on the Oxford rig and allowing six degrees of freedom was adapted in order to simulate and record the dynamic loads during a knee squat from 30 degrees to 120 degrees flexion under physiological conditions. Five different configurations were studied, with variable predetermined patellar heights. The patellofemoral contact force increased with increasing knee flexion until contact occurred between the quadriceps tendon and the femoral trochlea, inducing load sharing. Patella alta caused a delay of this contact until deeper flexion. As a consequence, the maximal patellofemoral contact force and contact pressure increased significantly with increasing patellar height (p < 0.01). Patella alta was associated with the highest maximal patellofemoral contact force and contact pressure. When averaged across all flexion angles, a normal patellar position was associated with the lowest contact pressures. Our results indicate that there is a biomechanical reason for anterior knee pain in patients with patella alta.Journal Articleinfo:eu-repo/semantics/publishe

Is there a biomechanical explanation for anterior knee pain in patients with patella alta?

The purpose of this study was to test the hypothesis that patella alta leads to a less favourable situation in terms of patellofemoral contact force, contact area and contact pressure than the normal patellar position, and thereby gives rise to anterior knee pain. A dynamic knee simulator system based on the Oxford rig and allowing six degrees of freedom was adapted in order to simulate and record the dynamic loads during a knee squat from 30 degrees to 120 degrees flexion under physiological conditions. Five different configurations were studied, with variable predetermined patellar heights. The patellofemoral contact force increased with increasing knee flexion until contact occurred between the quadriceps tendon and the femoral trochlea, inducing load sharing. Patella alta caused a delay of this contact until deeper flexion. As a consequence, the maximal patellofemoral contact force and contact pressure increased significantly with increasing patellar height (p < 0.01). Patella alta was associated with the highest maximal patellofemoral contact force and contact pressure. When averaged across all flexion angles, a normal patellar position was associated with the lowest contact pressures. Our results indicate that there is a biomechanical reason for anterior knee pain in patients with patella alta.Journal Articleinfo:eu-repo/semantics/publishe

Single-joint and whole-body movement changes in ACL athletes returning to sport

INTRODUCTION: Athletes returning to sport after anterior cruciate ligament reconstruction (ACLR) demonstrate prolonged changes in landing kinematics, kinetics, and muscle activation, predisposing them for reinjury, knee osteoarthritis, and/or knee instability. So far, researchers have been focusing on how kinematics and kinetics change in every joint separately. However, as the human body operates within a kinetic chain, we will assess whether single-joint changes are associated with whole-body changes. METHODS: Twenty-one athletes who had an ACLR and 21 uninjured controls performed five unilateral landing tasks, whereas lower limb kinematics, kinetics, and muscle activations of vastus medialis, vastus lateralis, biceps femoris, semitendinosus, semimembranosus, gastrocnemius, and gluteus medius were recorded. Single-joint landing kinematics, kinetics, and muscle activations of the ACL-injured leg were compared with the uninjured leg and compared with the control group. Whole-body changes were assessed by decomposing movements into fundamental components using marker-based principal component analysis (PCA). RESULTS: We found several single-joint changes in landing kinematics, kinetics, and muscle activations in the athletes with ACLR that were seen across all tasks and therefore of major interest as they are likely to occur during sports as well. Hamstrings activation increased and external knee flexion moments decreased in the ACL-injured leg compared with their uninjured leg. Furthermore, hip adduction moments and knee abduction angles decreased compared with the control group. The PCA could detect changes in whole-body movement, which were task-specific. CONCLUSIONS: Athletes with ACLR still show protective task-independent single-joint kinematic, kinetic, and muscle activation changes during single-leg landings at the time of return to sport. These single-joint changes were not consistently accompanied by changes in whole-body movements (revealed by marker-based PCA). Whole-body expressions of the single-joint compensations are likely to be affected by the demands of the task.status: publishe

The influence of malrotation and femoral component material on patellofemoral wear during gait

info:eu-repo/semantics/publishe