Browsing by Subject "knee"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Finite Element Analysis of an Electro-Mechanical Knee Loading Device
    (ASME, 2016-11) Prabhala, Sai Krishna; Anwar, Sohel; Yokota, Hiroki; Chien, Stanley; Mechanical Engineering, School of Engineering and Technology
    The mechanical loading of knee is an effective regimen for treatment of bone related ailments like fractures, osteoarthritis, and osteoporosis [1–2]. Efficacy of knee loading is evident from the previous studies done on rodents and other small animals [3]. In order to test this loading concept on human subjects, a prototype of a portable and compact device was designed previously. In this study, the prototype device was re-designed with a modified slider crank mechanism. Since this device has multiple moving parts, durability of the parts under stress is a key factor for its success. Thus, this paper focuses on its mechanical characteristics using finite element analysis (FEA). In particular, structural deformities and modal frequency characteristics are analyzed. The FEA analysis is performed on a CAD model of the device. The static structural and modal analyses are performed on two different configurations, in which different materials were used for selected components. Individual parts were meshed and solved extensively to obtain useful results under maximum loading conditions, such as total deformation, Von Mises stress, and modal frequencies. The analysis results show that ABS plastic based design provides an optimal solution in terms weight, cost, and usability.
  • Thumbnail Image
    Item
    Surgical Treatment of Chronic Periprosthetic Joint Infection: Fate of Spacer Exchanges
    (Elsevier, 2019) Tan, Timothy L.; Goswami, Karan; Kheir, Michael M.; Xu, Chi; Wang, Qiaojie; Parvizi, Javad; Orthopaedic Surgery, School of Medicine
    Introduction Patients with periprosthetic joint infection (PJI) undergoing two-stage exchange arthroplasty may undergo an interim spacer exchange for a variety of reasons including mechanical failure of spacer or persistence of infection. The objective of this study was to understand the risk factors and outcomes of patients that undergo spacer exchange during the course of a planned two-stage exchange arthroplasty. Methods Our institutional database was used to identify 533 patients who underwent a two-stage exchange arthroplasty for PJI, including 90 patients with a spacer exchange, from 2000-2017. A retrospective review was performed to extract relevant clinical information. Treatment outcomes included 1) progression to reimplantation and 2) treatment success as defined by a Delphi-based criterion. Both univariate and multivariate COX regression models were performed to investigate whether spacer exchange was associated with failure. Additionally, a propensity score analysis was performed based on a 1:2 match. Results A spacer exchange was required in 16.9%. Patients who underwent spacer exchanges had a higher body mass index (BMI) (p<0.001), rheumatoid arthritis (p=0.018), and were more likely to have PJI caused by resistant (0.048) and polymicrobial organisms (p=0.007). Patients undergoing a spacer exchange demonstrated lower survivorship and an increased risk of failure in the multivariate and propensity score matched analysis compared to patients who did not require a spacer exchange. Discussion Despite an additional load of local antibiotics and repeat debridement, patients who underwent a spacer exchange demonstrated poor outcomes, including failure to undergo reimplantation and twice the failure rate. The findings of this study may need to be borne in mind when managing patients who require spacer exchange.