Dynamic RSA for the evaluation of inducible micromotion of Oxford UKA during step-up and step-down motion

Background and purpose — Implant inducible micromotions have been suggested to reflect the quality of the fixation interface. We investigated the usability of dynamic RSA for evaluation of inducible micromotions of the Oxford Unicompartmental Knee Arthroplasty (UKA) tibial component, and evaluated factors that have been suggested to compromise the fixation, such as fixation method, component alignment, and radiolucent lines (RLLs). Patients and methods — 15 patients (12 men) with a mean age of 69 (55–86) years, with an Oxford UKA (7 cemented), were studied after a mean time in situ of 4.4 (3.6–5.1) years. 4 had tibial RLLs. Each patient was recorded with dynamic RSA (10 frames/second) during a step-up/step-down motion. Inducible micromotions were calculated for the tibial component with respect to the tibia bone. Postoperative component alignment was measured with model-based RSA and RLLs were measured on screened radiographs. Results — All tibial components showed inducible micromotions as a function of the step-cycle motion with a mean subsidence of up to −0.06 mm (95% CI: −0.10 to −0.03). Tibial component inducible micromotions were similar for cemented fixation and cementless fixation. Patients with tibial RLLs had 0.5° (95% CI: 0.18–0.81) greater inducible medio-lateral tilt of the tibial component. There was a correlation between postoperative posterior slope of the tibial plateau and inducible anterior-posterior tilt. Interpretation — All patients had inducible micromotions of the tibial component during step-cycle motion. RLLs and a high posterior slope increased the magnitude of inducible micromotions. This suggests that dynamic RSA is a valuable clinical tool for the evaluation of functional implant fixation

Disruption of Sleep Microarchitecture Is a Sensitive and Early Marker of Parkinson’s Disease

AbstractBackground:Although sleep disturbances are highly prevalent in patients with Parkinson’s disease, sleep macroarchitecture metrics show only minor changes.Objective:To assess alterations of the cyclic alternating pattern (CAP) as a critical feature of sleep microarchitecture in patients with prodromal, recent, and established Parkinson’s disease.Methods:We evaluated overnight polysomnography for classic sleep macroarchitecture and CAP metrics in 68 patients at various disease stages and compared results to 22 age- and sex-matched controls.Results:Already at the prodromal stage, patients showed a significantly reduced CAP rate as a central characteristic of sleep microarchitecture. Temporal characteristics of CAP showed a gradual change over disease stages and correlated with motor performance. In contrast, the sleep macroarchitecture metrics did not differ between groups.Conclusion:Data suggest that alterations of sleep microarchitecture are an early and more sensitive characteristic of Parkinson’s disease than changes in sleep macroarchitecture