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Technique of scleral buckling for retinal detachment repair
Published in A Peyman MD Gholam, A Meffert MD Stephen, D Conway MD FACS Mandi, Chiasson Trisha, Vitreoretinal Surgical Techniques, 2019
Scleral buckling can be performed under either local or general anesthesia, and the choice is often a function of surgeon preference and community standard of care. The advantages of local anesthesia include shorter operating time, quicker postoperative recovery, and decreased systemic morbidity. Potential risks include perforation of the globe (especially in myopic eyes), retrobulbar hemorrhage, retinal vascular occlusion, optic nerve injury, and brainstem anesthesia leading to respiratory arrest and grand-mal seizures.4 Peribulbar anesthesia may reduce these complications. The major disadvantage of local anesthesia is inadequate analgesia, which may occur in up to 10% of cases. If a two-injection technique is used for peribulbar anesthesia, the injection in the superior orbit should be given first to reduce the risk of globe perforation.5
Disc Structure and Function
Published in Peter Ghosh, The Biology of the Intervertebral Disc, 2019
The importance of correct orientation of reinforcing fibers in tissues indicates that the annulus is not directly responsible for withstanding much of the pressure applied to the disc. Axial compression of the annulus tends to compress its fibers, if they are not subjected to any other forces. When fiber-reinforced materials are compressed, their fibers tend to buckle either cooperatively, as shown in Figure 19a, or noncooperatively, as shown in Figure 19 b.108 Each fiber simply buckles like a tendon — the surrounding material (proteoglycan gel in the annulus) may influence the mode of buckling (cooperative or noncooperative), but does not prevent it.108 Thus, the annulus does not have a suitable structure for withstanding directly applied compression. However, we have already seen, in Section III.A, that the nucleus of a healthy disc has a high internal pressure and so supports most of the compressive load. We shall see, in Section IV.C, that in an intact disc the radial component of this pressure places the fibers of the annulus in tension, so that they are stretched when the disc is compressed. As a result they do not tend to buckle.
Nasal Reconstruction
Published in John C Watkinson, Raymond W Clarke, Terry M Jones, Vinidh Paleri, Nicholas White, Tim Woolford, Head & Neck Surgery Plastic Surgery, 2018
A pivot flap is one whose axis rotates around a pivot to close the defect. As the degree of rotation increases, the effective length of the flap decreases. The entire flap and the surrounding skin need to be undermined in all directions. Failure to do this results in excessive tension during closure and buckling and will possibly compromise vascularity.29 A bilobed flap is an example of a pivot flap. This is ideal for small defects (<1.5 cm) on the lateral side of the nose where local skin of the same thickness and colour can be used to fill a defect. If these flaps rotate skin through an arc of more than 110 degrees in the relatively inflexible thick skin of this region, it produces a prominent dog ear.
Can pain flares in knee osteoarthritis be predicted?
Published in Scandinavian Journal of Rheumatology, 2021
I Atukorala, A Pathmeswaran, J Makovey, B Metcalf, KL Bennell, L March, T Chang, Y Zhang, DJ Hunter
Our results show that exposures (with potential to vary during the following 30 days) assessed at baseline correlated with the occurrence of the same risk factors in the following 30 days. This explains why knee insults (injury or buckling), even if assessed at baseline, improved the predictive capacity of the model. We have therefore demonstrated that knee buckling/injury, once present, has the potential to recur. Because knee buckling is caused by knee effusions, instability, and muscle weakness, it can be repetitive in the same individual (38, 39). Similarly, participants tended to be equally injury prone and to wear similar heel heights/shoes during the following 30 days as at baseline. This supports that exposures which have the potential to vary in the following 30 days can usefully predict flares, despite being assessed at baseline. Although correlations were demonstrated in this case, it is not a requirement for the predictors in a model (assessed at baseline) to correlate with further predictor measurements during the follow-up.
Numerical investigation of mechanical behavior of human femoral diaphysis in normal and defective geometry: experimental evaluation
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Moeinoddin Mahmoudi, Hossein Mahbadi
Three-dimensional modeling of bone geometry is another important factor in numerical analysis of the bone. In some previous studies, a cylinder with a constant geometry and cross-section had been used to simplify the analysis (Fouad 2010; Sanderson et al. 2011, 2013). However, variation of the cross-sectional area has significant effect on FEA of bones. In this study, the CT scan method is used to model the endosteal geometry of both specimens. Considering the effect of bone cavity shows that the average cross-sectional area of the first specimen was 62% higher than the second specimen. This variation has significant effect on bending and buckling analysis of the bone. While the stress distribution and buckling load is affected by variation of the length and cross-section of the bone, these parameters has not been considered in previous studies (Miramini et al. 2016).
Features of Marfan syndrome not listed in the Ghent nosology – the dark side of the disease
Published in Expert Review of Cardiovascular Therapy, 2019
Yskert von Kodolitsch, Anthony Demolder, Evaldas Girdauskas, Harald Kaemmerer, Katharina Kornhuber, Laura Muino Mosquera, Shaine Morris, Enid Neptune, Reed Pyeritz, Svend Rand-Hendriksen, Alexander Rahman, Nina Riise, Leema Robert, Ingmar Staufenbiel, Katalin Szöcs, Thy Thy Vanem, Stephan J. Linke, Marina Vogler, Anji Yetman, Julie De Backer
Patients mention two distinct ophthalmic features that are not listed as features of Marfan syndrome in the Ghent nosologies, which we will briefly discuss here: Early onset cataract as the major symptom from the patients perspective is interesting and to my opinion due to the combination of ectopia lentis and cataract. Both are lens related and result in visual disturbance (increase of refractive error and optical aberrations by ectopia lentis) and reduced visual acuity (loss of transparency by early onset cataract). The patient (and doctor) cannot unambiguously differentiate these entities since both result in reduced visual acuity. Lens replacement (cataract) surgery is the common treatment option.Prolonged conjunctival wound healing from the patients’ perspective is surprising for me and probably a consequence of retinal detachment surgery. Due to altered scleral tissue buckling surgery can be more complex. It would be interesting to correlate the patient-reported prolonged conjunctival wound healing to the complexity of the surgery.