Background and Objectives: This study’s purpose was to examine the benefit of using a tibial extension in the primary operation of total knee arthroplasty (TKA). This is important because it is not a common practice to use the extension in a primary TKA, a standard configuration offering sufficient stability and good long-term survivorship. The following question arises: which situation requires the use of a standard configuration implant (without a stem) and which situation requires using the extension? Materials and Methods: The opportunity to use the tibial extension in the primary TKA was analyzed in correlation to the tibial bone structural properties. Using finite elements (FEs), the virtual model of the tibial bone was connected to that of the prosthetic implant, with and without a stem, and its behavior was analyzed during static and dynamic stresses, both in the situation in which the bone had normal physical properties, as well as in the case in which the bone had diminished physical properties. Results: The maximum stress and displacement values in the static compression regime show that adding a stem is only beneficial to structurally altered bone. Compression fatigue was reduced to almost half in the case of altered bone when adding a stem. Dynamic compression showed slightly better results with the tibial stem in both healthy and degraded bone. Conclusions: It was concluded that, if the bone is healthy and has good structural properties, it is not necessary to use the tibial extension in the primary operation; and if the bone has diminished physical properties, it is necessary to use the tibial extension at the primary operation, enhancing the stability, fixation, and implant lifespan.

The hip (coxofemoral) joint is built so as to provide, at the same time, maximum stability and mobility, and is characterized by a very low wear rate and very low frictional forces thanks to the very good natural lubrication. In time, due to various reasons such as aging, joint illnesses, bone tumors, arthritis, injuries, coxofemoral joints may lose their self-lubrication ability, causing pains that make movement almost impossible. The therapeutic solution for coxofemoral joint illnesses is hip implant arthroplasty. Medical implants replacing the bone segments of coxofemoral joints are subjected to mechanical stress during walking and daily activities, which leads to wear in the long run. In the (most frequent) case of a bipolar hip implant, consisting of a femoral stem and femoral head, the area most affected by wear is the hip implant coupling, which represents the connection between the sphere-shaped proximal end of the femoral stem and the femoral head’s ball groove. Typically, the spherical proximal end of the femoral stem is made of metallic biomaterials (titanium and titanium alloys, cobalt-based alloys, stainless steels) or ceramic biomaterials (alumina, zirconia), while the femoral head’s ball groove is made of polymeric biomaterials (high-density polyethylene), metallic biomaterials or ceramic biomaterials. In the hip implant’s coupling there takes place a sliding friction whose coefficient depends on the nature of the touching surfaces (metal on metal, metal on polyethylene, ceramic on polyethylene, ceramic on ceramic). The wear that occurs in the coupling is due especially to the particles of material detached from the surfaces coming into contact. A worn coupling should be replaced by a revision surgery that the patient must go through, since loose particles generate severe joint inflammation. The objective of this paper is: -to point out the wear degree of the components forming the friction coupling of a hip implant, by presenting images, as seen on a video microscope, of two implants retrieved from patients after revision surgery -to present a new structural option for the construction of a hip implant coupling, by introducing two ball cages that replace the femoral head’s ball groove, which reduces the contact surface and replaces sliding friction with rolling friction (with a lower friction coefficient), thus diminishing the wear on the implant coupling.

This paper presents a literature review of low-power hybrid wind–photovoltaic (PV) systems and introduces a 3 m diameter prototype rotor featuring twelve PV-coated pivoting blades stiffened by a peripheral rim. Existing solutions—foldable umbrella concepts, Darrieus rotors with PV-integrated blades, and morphing blades—are surveyed, and current gaps in simultaneous wind + PV co-generation on a single moving structure are highlighted. Key performance indicators such as power coefficient (C_p), DC ripple, cell temperature difference (ΔT), and levelised cost of energy (LCOE) are defined, and an integrated assessment methodology is proposed based on blade element momentum (BEM) and computational fluid dynamics (CFD) modelling, dynamic current–voltage (I–V) testing, and failure modes and effects analysis (FMEA) to evaluate system performance and reliability. Preliminary results point to moderate aerodynamic penalties (ΔC_p ≈ 5–8%), PV output during rotation equal to 15–25% of the nominal PV power (P_PV), and an estimated 70–75% reduction in blade–root bending moment when the peripheral ring converts each blade from a cantilever to a simply supported member, resulting in increased blade stiffness. Major challenges include the collective pitch mechanism, dynamic shading, and wear of rotating components (slip rings); however, the suggested technical measures—maximum power point tracking (MPPT), string segmentation, and redundant braking—keep performance within acceptable limits. This study concludes that the concept shows promise for distributed microgeneration, provided extensive experimental validation and IEC 61400-2-compliant standardisation are pursued. This paper has a dual scope: (i) a concise literature review relevant to low-Re flat-blade aerodynamics and ring-stiffened rotor structures and (ii) a multi-fidelity aero-structural study that culminates in a 3 m prototype proposal. We present the first evaluation of a hybrid wind–PV rotor employing untwisted flat-plate blades stiffened by a peripheral ring. Using low-Re BEM for preliminary loading, steady-state RANS-CFD (k-ω SST) for validation, and elastic FEM for sizing, we assemble a coherent load/performance dataset. After upsizing the hub pins (Ø 30 mm), ring (50 × 50 mm), and spokes (Ø 40 mm), von Mises stresses remain < 25% of the 6061-T6 yield limit and tip deflection ≤ 0.5%·R acrosscut-in (3 m s⁻¹), nominal (5 m s⁻¹), and extreme (25 m s⁻¹) cases. CFD confirms a broad efficiency plateau at λ = 2.4–2.8 for β ≈ 10° and near-zero shaft torque at β = 90°, supporting a three-step pitch schedule (20° start-up → 10° nominal → 90° storm). Cross-model deviations for C_p, torque, and pressure/force distributions remain within ± 10%. This study addresses only the rotor; off-the-shelf generator, brake, screw-pitch, and azimuth/tilt drives are intended for later integration. The results provide a low-cost manufacturable architecture and a validated baseline for full-scale testing and future transient CFD/FEM iterations.