MRI Sequence Influences Geometrical Information of Osseous Tissues

Although CT-scan data gives accurate geometrical information of bones, MRI data is commonly used instead due to its non-ionizing nature. The geometrical information has a number of applications, including image registration and computer simulations of the human joints, presurgical planning, prosthesis design, linking geometry with function and pain and kinematics. Hence, it is important to for the geometrical information extracted from the MRI data to be accurate. However, this information is influenced by the choice of the MRI sequence. Therefore, the aim of this study is to investigate the effect of different MRI sequences on the accuracy of geometrical information of bones

Fixed-bearing Medial Unicompartmental Knee Arthroplasty Restores Neither the Medial Pivoting Behavior Nor the Ligament Forces of the Intact Knee in Passive Flexion

Medial unicompartmental knee arthroplasty (UKA) is an accepted treatment for isolated medial osteoarthritis. However, using an improper thickness for the tibial component may contribute to early failure of the prosthesis or disease progression in the unreplaced lateral compartment. Little is known of the effect of insert thickness on both knee kinematics and ligament forces. Therefore, a computational model of the tibiofemoral joint was used to determine how non-conforming, fixed bearing medial UKA affects tibiofemoral kinematics and tension in the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) during passive knee flexion. Fixed bearing medial UKA could not maintain the medial pivoting that occurred in the intact knee from 0° to 30° of passive flexion. Abnormal anterior-posterior (AP) translations of the femoral condyles relative to the tibia delayed coupled internal tibial rotation, which occurred in the intact knee from 0° to 30° flexion, but occurred from 30° to 90° flexion following UKA. Increasing or decreasing tibial insert thickness following medial UKA also failed to restore the medial pivoting behavior of the intact knee despite modulating MCL and ACL forces. Reduced AP constraint in non-conforming medial UKA relative to the intact knee leads to abnormal condylar translations regardless of insert thickness even with intact cruciate and collateral ligaments. This finding suggests that the conformity of the medial compartment as driven by the medial meniscus and articular morphology plays an important role in controlling AP condylar translations in the intact tibiofemoral joint during passive flexion

Stress distribution in the knee joint following a high tibial osteotomy

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Reproducibility in modeling and simulation of the knee:Academic, industry, and regulatory perspectives

Stakeholders in the modeling and simulation (M&amp;S) community organized a workshop at the 2019 Annual Meeting of the Orthopaedic Research Society (ORS) entitled “Reproducibility in Modeling and Simulation of the Knee: Academic, Industry, and Regulatory Perspectives.” The goal was to discuss efforts among these stakeholders to address irreproducibility in M&amp;S focusing on the knee joint. An academic representative from a leading orthopedic hospital in the United States described a multi-institutional, open effort funded by the National Institutes of Health to assess model reproducibility in computational knee biomechanics. A regulatory representative from the United States Food and Drug Administration indicated the necessity of standards for reproducibility to increase utility of M&amp;S in the regulatory setting. An industry representative from a major orthopedic implant company emphasized improving reproducibility by addressing indeterminacy in personalized modeling through sensitivity analyses, thereby enhancing preclinical evaluation of joint replacement technology. Thought leaders in the M&amp;S community stressed the importance of data sharing to minimize duplication of efforts. A survey comprised 103 attendees revealed strong support for the workshop and for increasing emphasis on computational modeling at future ORS meetings. Nearly all survey respondents (97%) considered reproducibility to be an important issue. Almost half of respondents (45%) tried and failed to reproduce the work of others. Two-thirds of respondents (67%) declared that individual laboratories are most responsible for ensuring reproducible research whereas 44% thought that journals are most responsible. Thought leaders and survey respondents emphasized that computational models must be reproducible and credible to advance knee M&amp;S.</p

432 Ligament Engagement and In-Situ Force During Multiplanar Loading of the Medial Knee Ligaments

OBJECTIVES/GOALS: Load sharing across the arc of knee flexion of the medial knee ligaments (MKLs) is not well understood. The goal of this research is to characterize ligament engagement and in-situ force within the deep and superficial medial collateral ligament (dMCL, sMCL) and the posterior oblique ligament (POL) in response to externally applied multiplanar loads. METHODS/STUDY POPULATION: Ten human cadaveric knees, 5 male and 5 female, age 32±7 (25-42) [mean±SD (range min-max)] years, were mounted to a force sensor and a 6-degree-of-freedom robotic arm. Knee kinematics, before and after serial dissection of the sMCL, dMCL, and POL, were recorded from 0-30 degrees during applied isolated external rotation, valgus angulation, and anterior tibial moments, and the force (Newtons, N) borne by each structure was measured via the principle of superposition. Loads in the dMCL, sMCL, and POL will be compared across each knee and at each flexion angle with paired t-tests and repeated-measures analysis of variance with Tukey post hoc testing. Ten knees will provide >99% power to detect differences of 5N ± 3% at p=0.05, which is considered the threshold for clinically meaningful force differences. RESULTS/ANTICIPATED RESULTS: Our anticipated results include characterization of the means and standard deviations of the in-situ forces within the dMCL, sMCL, and POL in response to externally applied valgus angulation, tibial external rotation, and anterior-directed tibial loading at 0, 15, and 30 degrees of knee flexion. Our statistical analysis will determine if there are clinically meaningful differences (5N ± 3%) in the loads within each ligament at different knee flexion angles and will also provide data regarding differential relative ligament engagement for each applied force scenario, which is an indication of the percentage of contribution that each structure contributes to knee stability during application of forces and torques to the knee. DISCUSSION/SIGNIFICANCE: Data on ligament engagement and in-situ forces will help clinicians better diagnose potentially injured ligaments when they observe pathological knee laxity in an injured patient. Our results will also inform future computer modeling studies on injury mechanisms, individual anatomical variability, and surgical planning

Biomechanical Evaluation of the Efficacy of External Stabilizers in the Conservative Treatment of Acquired Flatfoot Deformity

This study quantified and compared the efficacy of in-shoe orthoses and ankle braces in stabilizing the hindfoot and medial longitudinal arch in a cadaveric model of acquired flexible flatfoot deformity. This was addressed by combining measurement of hindfoot and arch kinematics with plantar pressure distribution, produced in response to axial loads simulating quiet standing. Experiments were conducted on six fresh-frozen cadaveric lower limbs. Three conditions were tested: intact-unbraced; flatfoot-unbraced; and flatfoot-braced. Flatfoot deformity was created by sectioning the main support structures of the medial longitudinal arch. Six different braces were tested including two in-shoe orthoses, three ankle braces and one molded ankle-foot orthosis.Our model of flexible flatfoot deformity caused the calcaneus to evert, the talus to plantarflex and the height of the talus and medial cuneiform to decrease. Flexible flatfoot deformity caused a pattern of medial shift in plantar pressure distribution, but minimal change in the location of the center of pressure. Furthermore, in-shoe orthoses stabilized both the hindfoot and the medial longitudinal arch, while ankle braces did not. Semi-rigid foot and ankle orthoses acted to stabilize the medial longitudinal arch. Based on these results, it was concluded that treatment of flatfoot deformity should at least include use of in-shoe orthoses to partially restore the arch and stabilize the hindfoot.</jats:p