Extended mechanical loads for the analysis of acetabular cages.

To analyse the strength and mechanical behaviour of hip implants, it is essential to employ an appropriate loading model. Generating computational models supplemented with muscle forces is a complicated task, especially in the initial phase of implant development. This research aims to expand the possibilities of the simpler acetabular cage model based on joint loads without significantly increasing the demand for computing resources. A Python script covered and grouped the loads from daily activities. The ten calculated major loads were compared with the maximum of the walking and stair climbing loads through the finite element analyses of a custom-made acetabular cage. Sensitivity analyses were performed for the surrounding bones' elastic modulus and the pelvis boundary conditions. The major loads can geometrically cover the entire load spectrum of daily activities. The effect of many high-magnitude force vectors is uncertain in the approach that uses the most common maximum loads. Using these resultant major loads, a new stress concentration area could be detected on the acetabular cage, besides the stress concentration areas induced by the loads reported in the literature. The qualitative correctness of the results is also supported by a control computed tomography scan: a fracture occurred in an extensive, high-stress zone. The results are not sensitive to changes in the elastic modulus of the surrounding bone and the boundary conditions of the model. The presented load vectors and the algorithm make more extensive static analyses possible with little computational overhead. The proposed method can be used for checking the static strength of similar implants.

[Hyperbaric oxygen therapy in outpatient care]. / A túlnyomásos oxigénkezelés és helye az ambuláns ellátásban.

Hyperbaric oxygen therapy, or high pressure oxygen therapy, is a highly specialised branch of medicine. Applications and results date back to the 1960s and it has been used, researched and developed ever since. During the treatment, patients breathe 100% oxygen in a pressurised chamber. For clinical purposes, as defined, the pressure must equal or exceed 1.4 atmosphera absolute, most of the cases typically higher (2.0-2.5 atmosphera absolute). Oxygen dissolves by pressure in body fluids, transported by circulation to all tissues. Cellular regeneration and tissue processes are induced by both the increased oxygen supply and the intermittent change in tissue partial oxygen pressure associated with treatment. The effect can be used in the treatment of many diseases, usually as part of a complex treatment plan. Additional advantage is that it is a non-invasive and pain-free therapy. Evidence-based indications and general baseline usage are regulated by the European Underwater and Baromedical Society through the European Committee of Hyperbaric Medicine, in accordance with the principles of evidence-based medicine. The authors describe three cases in their publication where hyperbaric oxygen therapy significantly contributed to the success of overall treatment. Orv Hetil. 2023; 164(25): 993-996.

Equivalent loads from the life-cycle of acetabular cages in relation to bone-graft transformation.

BACKGROUND AND OBJECTIVES: Bone grafts placed behind acetabular cages change their structure in response to mechanical stimuli. The full consideration of lifestyle loads is extremely resource-intensive, so a method using substitutive loads was proposed to reduce the calculation cost. The aim of the study is to present and prove this method. METHODS: By means of mechanical equations and using the force vectors from the literature which have the same initial point and their relative frequency, while applying a linear model, the average strain energy density distribution for all load cases can be calculated, compiling a matrix from the external loads. From the elements of this matrix, three substitutive load vectors can be calculated, which can be proven to produce the same strain energy density distribution by averaging their effects. The feasibility of using this to model the transformation of bone grafts placed behind acetabular cages is demonstrated with a finite element model, along with a reference calculation. RESULTS: The substitutive load vectors could be calculated in closed form and the simulations showed that they produced a similar density distribution to the reference model with a numerical calculation error range. Accordingly, the density distribution calculated from bone graft transformation is almost the same. CONCLUSIONS: In addition to the aforementioned linearity and the same initial point limitations, the applied method is able to produce the substitutive load vectors with which the calculation of the strain energy density distribution and the bone graft's new density distributions can be carried out faster.

Institutionally Adopted Perioperative Blood Management Program Significantly Decreased the Transfusion Rate of Patients Having Primary Total Hip Replacement Surgery.

Perioperative transfusion in patients undergoing orthopedic surgery increases the number of postoperative complications. Thus, we have introduced an institution-tailored perioperative blood management program (PBM) to decrease the amount of blood transfused in patients going through primary total hip replacement (THR) surgery. We have conducted a before-after observational cohort study in two predetermined observational periods. Demographic and clinical data, ASA scores, laboratory parameters, features of surgical procedure, and anesthesia were registered. Parameters of perioperative fluid administration, transfusion rate, and postoperative complications were also assessed. One hundred patients in the first and 108 patients in the second observational period were enrolled. Eventhough the ratio of posttraumatic THR procedures increased (9% vs. 17%), the PBM protocol has been utilized effectively and a significant decrease in perioperative blood transfusion rate has been observed (61% vs. 21%). The abolishment of routine preoperative LMWH prophylaxis (90% vs. 16%), intraoperative use of tranexamic acid (10% vs. 84%), and the encouraged exploitation of our postoperative observational facility (5% vs. 39%) were abided by our colleagues. Patients still requiring transfusion had lower preoperative hemoglobin levels (129 vs. 147 g/l), scored higher in ASA (ASA III: 46% vs. 19%), and more often presented postoperative hypotension (40% vs. 7%), oliguria (23% vs. 5%), and infections (9% vs. 2%). We conclude that the individualized perioperative blood management protocol was successfully implemented and yielded a lower transfusion rate and better outcomes. Our study suggests that a partial, institution-tailored PBM program may be suitable and beneficial in countries where the modalities of perioperative blood management are limited.

Intraarticular Injection of a Cross-Linked Sodium Hyaluronate Combined with Triamcinolone Hexacetonide (Cingal) to Provide Symptomatic Relief of Osteoarthritis of the Knee: A Randomized, Double-Blind, Placebo-Controlled Multicenter Clinical Trial.

OBJECTIVE: To evaluate the efficacy and safety of an intraarticular injection of Cingal (Anika Therapeutics, Inc., Bedford, MA) compared with Monovisc (Anika Therapeutics, Inc., Bedford, MA) or saline for the treatment of knee osteoarthritis. DESIGN: This multicenter, double-blind, saline-controlled clinical trial randomized subjects with knee osteoarthritis (Kellgren-Lawrence grades I-III) to a single injection of Cingal (4 mL, 88 mg hyaluronic acid [HA] plus 18 mg triamcinolone hexacetonide [TH]), Monovisc (4 mL, 88 mg HA), or saline (4 mL, 0.9%). The primary efficacy outcome was change in WOMAC (Western Ontario and McMaster Universities Arthritis Index) Pain Score through 12 weeks with Cingal versus saline. Secondary outcomes included Patient and Evaluator Global Assessments, OMERACT-OARSI Responder index, and WOMAC Total, Stiffness, and Physical Function scores through 26 weeks. RESULTS: A total of 368 patients were treated (Cingal, n = 149; Monovisc, n = 150; saline, n = 69). Cingal improvement from baseline was significantly greater than saline through 12 weeks ( P = 0.0099) and 26 weeks ( P = 0.0072). WOMAC Pain was reduced by 70% at 12 weeks and by 72% at 26 weeks with Cingal. Significant improvements were found in most secondary endpoints for pain and function at most time points through 26 weeks. At 1 and 3 weeks, Cingal was significantly better than Monovisc for most endpoints; Cingal and Monovisc were similar from 6 weeks through 26 weeks. A low incidence of related adverse events was reported. CONCLUSIONS: Cingal provides immediate and long-term relief of osteoarthritis-related pain, stiffness, and function, significant through 26 weeks compared to saline. Cingal had similar immediate advantages compared with HA alone, while showing benefit comparable to HA at 6 weeks and beyond.

Mechanical loading stimulates chondrogenesis via the PKA/CREB-Sox9 and PP2A pathways in chicken micromass cultures.

Biomechanical stimuli play important roles in the formation of articular cartilage during early foetal life, and optimal mechanical load is a crucial regulatory factor of adult chondrocyte metabolism and function. In this study, we undertook to analyse mechanotransduction pathways during in vitro chondrogenesis. Chondroprogenitor cells isolated from limb buds of 4-day-old chicken embryos were cultivated as high density cell cultures for 6 days. Mechanical stimulation was carried out by a self-designed bioreactor that exerted uniaxial intermittent cyclic load transmitted by the culture medium as hydrostatic pressure and fluid shear to differentiating cells. The loading scheme (0.05 Hz, 600 Pa; for 30 min) was applied on culturing days 2 and 3, when final commitment and differentiation of chondroprogenitor cells occurred in this model. The applied mechanical load significantly augmented cartilage matrix production and elevated mRNA expression of several cartilage matrix constituents, including collagen type II and aggrecan core protein, as well as matrix-producing hyaluronan synthases through enhanced expression, phosphorylation and nuclear signals of the main chondrogenic transcription factor Sox9. Along with increased cAMP levels, a significantly enhanced protein kinase A (PKA) activity was also detected and CREB, the archetypal downstream transcription factor of PKA signalling, exhibited elevated phosphorylation levels and stronger nuclear signals in response to mechanical stimuli. All the above effects were diminished by the PKA-inhibitor H89. Inhibition of the PKA-independent cAMP-mediators Epac1 and Epac2 with HJC0197 resulted in enhanced cartilage formation, which was additive to that of the mechanical stimulation, implying that the chondrogenesis-promoting effect of mechanical load was independent of Epac. At the same time, PP2A activity was reduced following mechanical load and treatments with the PP2A-inhibitor okadaic acid were able to mimic the effects of the intervention. Our results indicate that proper mechanical stimuli augment in vitro cartilage formation via promoting both differentiation and matrix production of chondrogenic cells, and the opposing regulation of the PKA/CREB-Sox9 and the PP2A signalling pathways is crucial in this phenomenon.