This numerical vibration finite component (FE) examine introduces resonance three-dimensional planning (RP3D) to evaluate preoperatively the primary stability of a cementless stem for whole hip arthroplasty.
Based on a affected person’s CT-scan and a numerical mannequin of a stem, RP3D goals at offering mechanical standards indicative of the achievable primary stability. We examine variations of the modal response of the stem to adjustments of space and obvious stiffness of the bone-implant interface.
The mannequin is computationally low-cost because it doesn’t embrace a mesh of the bone. The obvious stiffness of the bone is modeled by springs hooked up to the nodes of the stem’s mesh. We examine an prolonged vary of stiffness values whereas, in future works, affected person’s particular Hounsfield values may very well be used to outline stiffness.
We report modal frequencies, shapes, and a ratio of elastic potential energies (rEPE) that quantifies the proximal movement that ought to be minimal for a steady stem. The modal response displays a transparent transition between free and tight contact as space and stiffness of the interface enhance. rEPE thresholds that would doubtlessly discriminate preoperatively between steady and unstable stems are given for a Symbios SPS® dimension C stem.
Reproducibility of digital measurements of lower-limb deformity on plain radiographs and settlement with CT measurements
Five angles (HKA, HKS, alpha, beta, tibial slope) are used for goniometry in whole knee arthroplasty. The reproducibility of the measurement of these angles has been assessed on plain and digitized x-rays, however to our data, this has not been confirmed on x-rays taken on the PACS system they usually haven’t been in comparison with computed tomography (CT) measurements, the reference for angle measurement. This potential examine aimed to: (1) consider the inter- and intrarater reliability of the measurement of these angles on digital x-rays taken on a PACS; (2) decide the settlement of these measurements with these obtained utilizing a CT protocol.The measurements of these 5 angles on digitized radiographs are reproducible and in settlement with CT values.Forty-two sufferers affected by knee osteoarthritis and scheduled for whole knee arthroplasty have been included in the examine.
Each affected person had a PACS digitized x-ray and a CT supposed to supply patient-specific instrumentation (Symbios, Yverdon, Switzerland) together with measurements of the angles evaluated. Four senior orthopaedic surgeon-raters measured all the angles twice. Inter- and intrarater reliability was then calculated in addition to the settlement between the second measurement of every rater and the CT measurement utilizing interclass correlation and kappa coefficients (knowledge offered as means and 95% confidence intervals).
The inter- and intrarater reliability values have been wonderful for the HKA, alpha, and beta angles (with, respectively, a coefficient of 0.99 [0.97-0.99], 0.84 [0.76-0.9], and 0.94 [0.86-0.96] interrater reliability and 0.98 [0.96-0.99], 0.86 [0.75-0.92], and 0.65 [0.44-0.8] intrarater reliability). Interrater reliability was low for HKS and tibial slope angles (coefficients all<0.4 for interrater reliability and <0.7 for intrarater reliability).
The x-ray/CT settlement was superb for the HKA, alpha, and beta angles (0.81 [0.67-0.99], 0.74 [0.56-0.91], and 0.74 [0.45-0.92], respectively) and low for the HKS and tibial slope angles (all<0.45).The HKA, alpha, and beta angles have been reproducible for digital radiographs and confirmed good settlement with CT measurements.
HKS and tibial slope angles ought to be used with better warning, and different navigation strategies or patient-specific instrumentation ought to be explored.Level III, potential, comparative diagnostic case-control examine.