Experimental measurements of femoral primary stability in two cementless posterior-stabilized knee replacement implants.

Sufficient primary stability through interference fit is required for bone ingrowth and subsequent long-term fixation of cementless knee replacement implants, and can be evaluated in experimental testing. In this study, primary stability of a novel posterior-stabilized (PS) femoral component (Attune PS) and a contemporary PS component (Triathlon PS) were analyzed, and compared to previous outcomes of cruciate-retaining (CR) implants. Potential bone ingrowth was evaluated by measuring micromotions over the implant-bone interface in six cadaveric femur pairs under two loading conditions using digital image correlation, for a paired comparison of the PS implants.

Computational tibial bone remodeling over a population after total knee arthroplasty: A comparative study.

Periprosthetic bone loss is an important factor in tibial implant failure mechanisms in total knee arthroplasty (TKA). The purpose of this study was to validate computational postoperative bone response using longitudinal clinical DEXA densities. Computational remodeling outcome over a population was obtained by incorporating the strain-adaptive remodeling theory in finite element (FE) simulations of 26 different tibiae.

Population-based effect of total knee arthroplasty alignment on simulated tibial bone remodeling.

Periprosthetic bone loss is an important factor in tibial implant failure mechanisms in total knee arthroplasty (TKA). The purpose of this study was to determine the effect of postoperative knee alignment and population variation on tibial bone remodeling, to assess long-term stability of a knee replacement. Strain-adaptive finite element (FE) remodeling simulations were conducted following kinematic and mechanical alignment of a cemented fixed-bearing implant after TKA; kinematic TKA alignment was assumed to be more consistent with the preoperative varus alignment, while mechanical alignment was defined according to the neutral mechanical axes.

Reproducibility and discriminant validity of two clinically feasible measurement methods to obtain coronal plane gait kinematics in participants with a lower extremity amputation.

Introduction: Measuring coronal plane gait kinematics of the pelvis and trunk during rehabilitation of participants with a lower extremity amputation is important to detect asymmetries in gait which are hypothesised as associated with secondary complaints. The aim of this study was to test the reproducibility and discriminant validity of a three-dimensional (3-D; inertial measurement units) and a two-dimensional (2-D; video-based) system.

Methods: We tested the test-retest and inter-rater reproducibility of both systems and the 2-D system, respectively, in participants with a lower extremity amputation (group 1) and healthy subjects (group 2).

In situ comparison of A-mode ultrasound tracking system and skin-mounted markers for measuring kinematics of the lower extremity.

Skin-mounted marker based motion capture systems are widely used in measuring the movement of human joints. Kinematic measurements associated with skin-mounted markers are subject to soft tissue artifacts (STA), since the markers follow skin movement, thus generating errors when used to represent motions of underlying bone segments. We present a novel ultrasound tracking system that is capable of directly measuring tibial and femoral bone surfaces during dynamic motions, and subsequently measuring six-degree-of-freedom (6-DOF) tibiofemoral kinematics.

Improving stress shielding following total hip arthroplasty by using a femoral stem made of β type Ti-33.6Nb-4Sn with a Young's modulus gradation.

Stress shielding-related bone loss occurs after total hip arthroplasty because the stiffness of metallic implants differs from that of the host femur. Although reducing stem stiffness can ameliorate the bone resorption, it increases stress at the bone-implant interface and can inhibit fixation. To overcome this complication, a novel cementless stem with a gradient in Young's modulus was developed using Ti-33.