Reactivation of Coccidioides immitis in a Prosthetic Knee after Initiation of Chemotherapy

Coccidioides is an endemic fungus in the Southwestern United States and Central and South America. Coccidioidomycosis primary infections are typically of the lung with an asymptomatic or self-limiting course. Some infections disseminate to other parts of the body and a few can remain latent for many years. Reactivation of latent fungal disease can occur following an insult to the host immune system. Here, we describe a case of a 76-year-old Caucasian male patient who moved from California to Wisconsin with a history of coccidioidomycosis infection of the left knee that reactivated decades later in his prosthetic knee shortly after being initiated on ibrutinib (Imbruvica), a Bruton tyrosine kinase (BTK) inhibitor, for chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). There have been some case reports regarding coccidioidomycosis infections after initiating ibrutinib therapy but none with a 50 year latency period before reactivation. Readers will learn the immunological effects of ibrutinib on the hosts’ innate and adaptive immunity and its role in putting the host at risk for invasive fungal infections. We also review the literature and data on treatment regimens and recommendations based on current guidelines.

Design of a four-bar latch mechanism and a shear-based rotary viscous damper for single-axis prosthetic knees

With over 30 million people worldwide requiring assistive devices, there is a great need for affordable prosthetic technologies that can enable kinematics close to able-bodied gait. Passive prosthetic knees designed for low-income users have primarily focused on stability and affordability, often at the cost of the high biomechanical performance that is required to replicate able-bodied kinematics. We present the design and preliminary testing of two distinct mechanisms that are novel for passive prosthetic knee applications: the stability module and the damping module. These mechanisms are designed to enable users of single-axis, passive prostheses to walk with close to able-bodied kinematics on level-ground, specifically during the transition from the stance phase to the swing phase of the gait cycle. The stability module was implemented with a latch mounted on a virtual axis of a four-bar linkage, which can be engaged during early stance for stability and disengaged during late stance to initiate knee flexion. The damping module was implemented with a concentric stack of stationary and rotating pairs of plates that shear thin films of high-viscosity silicone oil. For preliminary user-centric validation, a prototype prosthetic knee with the stability module and two dampers (with varying damping coefficients) was tested on a single participant. The stability module enabled smooth transition from stance to swing with timely initiation of knee flexion. An increase in the damping coefficient was found to decrease the peak knee flexion close to the able-bodied range (58-70 deg).

Rotating Hinge Knee Arthroplasty for Revision Prosthetic-Knee Infection: Good Functional Outcomes but a Crucial Need for Superinfection Prevention

Introduction: Management of chronic infection following total knee arthroplasty (TKA) is challenging. Rotating hinged prostheses are often required in this setting due to severe bone loss, ligamentous insufficiency, or a combination of the two. The nature of the mechanical and septic complications occurring in this setting has not been well-described. The aim of this study was to evaluate patient outcomes using a hinge knee prosthesis for prosthetic knee infections and to investigate risk factors for implant removal.Methods: This was a retrospective cohort study that included all patients treated in our tertiary level referral center between January 2009 and December 2016 for prosthetic knee infection with a hinge knee prosthesis. Only patients with a minimum 2-year of follow-up were included. Functional evaluation was performed using international knee society (IKS) “Knee” and “Function” scores. Survival analysis comparing implant removal risks for mechanical and septic causes was performed using Cox univariate analysis and Kaplan-Meier curves. Risk factors for implant removal and septic failure were assessed.Results: Forty-six knees were eligible for inclusion. The majority of patients had satisfactory functional outcomes as determined by mean IKS scores (mean knee score: 70.53, mean function score: 46.53 points, and mean knee flexion: 88.75°). The 2-year implant survival rate was 89% but dropped to 65% at 7 years follow-up. The risk of failure (i.e., implant removal) was higher for septic etiology compared to mechanical causes. Patients with American society of anesthesiologists (ASA) score>1, immunosuppression, or with peripheral arterial diseases had a higher risk for septic failure. Patients with acute infection according to the Tsukayamaclassification had a higher risk of failure. Of the 46 patients included, 19 (41.3%) had atleast one infectious event on the surgical knee and most of these were superinfections (14/19) with new pathogens isolated. Among pathogens responsible for superinfections (i) cefazolin and gentamicin were both active in six of the cases but failed to prevent the superinfection; (ii) cefazolin and/or gentamicin were not active in eight patients, leading to alternative systemic and/or local antimicrobial prophylaxis consideration.Conclusions: Patients with chronic total knee arthroplasty (TKA) infection, requiring revision using rotating hinge implant, had good functional outcomes but experienced a high rate of septic failure, mostly due to bacterial superinfection. These patients may need optimal antimicrobial systemic prophylaxis and innovative approaches to reduce the rate of superinfection.