Testing a Quaternion Conversion Method to Determine Human 3D Tibiofemoral Angles During an in Vitro Simulated Jump Landing

Lower limb joint kinematics have been measured in laboratory settings using fixed camera-based motion capture systems; however, recently inertial measurement units (IMUs) have been developed as an alternative. The purpose of this study was to test a quaternion conversion (QC) method for calculating the three orthogonal knee angles during the high velocities associated with a jump landing using commercially available IMUs. Nine cadaveric knee specimens were instrumented with APDM Opal IMUs to measure knee kinematics in one-legged 3-4x bodyweight simulated jump landings, four of which were used in establishing the parameters (training) for the new method and five for validation (testing). We compared the angles obtained from the QC method to those obtained from a commercially available sensor and algorithm (APDM Opal) with those calculated from an active marker motion capture system. Results showed a significant difference between both IMU methods and the motion capture data in the majority of orthogonal angles (p<0.01), though the differences between the QC method and Certus system in the testing set for flexion and rotation angles were smaller than the APDM Opal algorithm, indicating an improvement. Additionally, in all 3 directions both the limits of agreement and root mean square error between the QC method and the motion capture system were smaller than between the commercial algorithm and the motion capture.

Passive ligament stability in natural knee: a cadaveric biomechanical study

Objectives: Applying the correct amount of collateral ligaments tension in the knees during surgery is a prerequisite to restore normal kinematics after TKA. It is well known that a low value of ligament tension could lead to an instable joint while a higher tension could induce over-tensioning and problems at later follow-up. In this study, an experimental cadaveric activity was performed to measure the minimum tension required to achieve stability in the knee joint.Methods: 10 cadaveric knee specimens were investigated in this study. The femur and tibia were fixed with polyurethane foam in specific designed fixtures and clamped to a loading frame.Increasing displacement was applied to the femoral clamp and the relative force was measured by a loading-frame machine up to the stability of the joint, determined by a decrease in the derivate of the force/displacement trend followed by a plateau.The force span between the slack region and the plateau was considered as the tension required to stabilize the joint.This methodology was applied for joints with intact cruciate ligaments, after ACL resection and after further PCL resection, to simulate the knee behavior prior a CR and a PS implant.The test was performed at 0, 30, 60 and 90° of flexion. Each configuration was analyzed three times for the sake of repeatability.Results and Conclusion: Results demonstrated that an overall tension of 41.2N (range 30.0-48.0 N) is sufficient to reach stability in a native knee with intact cruciate ligaments. Similar values appear to be sufficient also in an ACL resected knee (average 45.6, range 41.2-50.0 N), while higher tension is required (average 58.6N, range 40.0-77.0 N) were necessary in the case of PCL retention. Moreover, in this configuration, the tension required for stabilization was slighter higher at 30 and 60° of flexion compared to the one required at 0 and 90° of flexion.The results are in agreement to the ones found by other recent experimental study [Manning et al 2018 (KSSTA)] and shown that the tension necessary to stabilize a knee joint in different ligament conditions is way lower than the ones usually applied via tensioners nowadays.To reach functional stability, surgeons need to consider such results intraoperatively to avoid laxity, mid-flexion instability or ligament over-tension.

Assessment of the Degree of Osteoarthritis in Aging Male and Female Femoral Condyles: A Cadaveric Study

Objective Determine if femoral chondral cartilage degeneration on cadaveric knee joints exacerbate differently with aging between the sexes. Methods A total of 85 cadaveric femurs were assessed for macroscopic femoral condyle pathology using a scale for gross signs of osteoarthritis. Raters scored specimens and raters’ scores were averaged to provide each specimen a Disease Severity Score (DSS). Results The DSS for the 80+-year-old population was greater than the DSS of the 70- to 79-year-old population (* P < 0.05) and the <70-year-old population (** P < 0.01). Specimens that scored a DSS of 2 and higher were assessed for their specific site of most severe degeneration. The most severe degeneration on the articular cartilage was most regularly on the patellar fossa. The second most degenerated region varied by age and biomechanical alterations. There were no significant changes in DSS between the sexes within the age groups. Conclusions No difference was shown between the sexes in the severity or location of degeneration indicating that men and women are likely affected by the same biomechanical changes that spur on osteoarthritis in their eighth decade of life (70s) and later. Lateral femoral degeneration predominates in younger populations. When patients approach their 70s, medial degeneration begins to predominate likely based on an increase in shearing at the knee joint.

Development and Assessment of a Microcomputed Tomography Compatible Five Degrees-of-Freedom Knee Joint Motion Simulator

Currently available knee joint kinematic tracking systems fail to nondestructively capture the subtle variation in joint and soft tissue kinematics that occur in native, injured, and reconstructed joint states. Microcomputed tomography (CT) imaging has the potential as a noninvasive, high-resolution kinematic tracking system, but no dynamic simulators exist to take advantage of this. The purpose of this work was to develop and assess a novel micro-CT compatible knee joint simulator to quantify the knee joint's kinematic and kinetic response to clinically (e.g., pivot shift test) and functionally (e.g., gait) relevant loading. The simulator applies closed-loop, load control over four degrees-of-freedom (DOF) (internal/external rotation, varus/valgus rotation, anterior/posterior translation, and compression/distraction), and static control over a fifth degree-of-freedom (flexion/extension). Simulator accuracy (e.g., load error) and repeatability (e.g., coefficient of variation) were assessed with a cylindrical rubber tubing structure and a human cadaveric knee joint by applying clinically and functionally relevant loads along all active axes. Micro-CT images acquired of the joint at a loaded state were then used to calculate joint kinematics. The simulator loaded both the rubber tubing and the cadaveric specimen to within 0.1% of the load target, with an intertrial coefficient of variation below 0.1% for all clinically relevant loading protocols. The resultant kinematics calculated from the acquired images agreed with previously published values, and produced errors of 1.66 mm, 0.90 mm, 4.41 deg, and 1.60 deg with respect to anterior translation, compression, internal rotation, and valgus rotation, respectively. All images were free of artifacts and showed knee joint displacements in response to clinically and functionally loading with isotropic CT image voxel spacing of 0.15 mm. The results of this study demonstrate that the joint-motion simulator is capable of applying accurate, clinically and functionally relevant loads to cadaveric knee joints, concurrent with micro-CT imaging. Nondestructive tracking of bony landmarks allows for the precise calculation of joint kinematics with less error than traditional optical tracking systems.

Interference Screw Versus Suture Endobutton Fixation of a Fiber-Reinforced Meniscus Replacement Device in a Human Cadaveric Knee Model

Background: Meniscal lesions represent one of the most common intra-articular knee injuries. Meniscus replacement devices are needed to restore load distribution and knee stability after meniscectomy. Fixation of these devices is crucial to the generation of hoop stresses and the distribution of loads in the joint. Purpose: To evaluate 2 different fixation techniques (suture endobutton and interference screw) for implantation of a novel meniscus device. Study Design: Controlled laboratory study. Methods: In 7 human cadaveric knees (aged 17-61 years), 1 anterior and 2 potential posterior tunnel locations were investigated, and both fixation techniques were tested in each tunnel. The native meniscus roots, devices fixed with a suture endobutton, and devices fixed with an interference screw were gripped with cryoclamps, and tibias were drilled and loaded into a custom jig. Samples were preloaded, preconditioned, loaded for 500 cycles (50-150 N), and tested in tension until failure. Results: For all 3 tunnels, suture fixation resulted in greater elongation (54.1%-150.7% greater; P < .05) during cyclic loading than interference screw fixation, which approximated the native roots. Both fixation techniques displayed ultimate tensile loads in the same range as native roots. However, stiffness of the suture fixation groups (36.5-41.6 N/mm) was only 28% to 37% of that of the interference screw fixation groups (98.7-131.6 N/mm), which had values approaching those of the native roots (anterior: 175.4 ± 24.2 N/mm; posterior: 157.6 ± 22.9 N/mm). Conclusion: Interference screw fixation was found to be superior to suture fixation with regard to elongation and stiffness, a finding that should be considered in the design and implantation of novel meniscus replacement devices. Clinical Relevance: With the emergence of various devices for total meniscus replacement, the establishment of fixation strategies is crucial for the generation of tensile hoop stresses and the efficacy of these approaches.