Immediate Z-plasty for semicircular wounds

Simple layered repair of semicircular and curved lacerations frequently results in elevation of the central area following contraction of the scar. Traditionally, immediate tissue rearrangement at the time of the injury has been discouraged. We performed single or multiple Z-plasties at the time of the initial repair on five consecutive patients with curved and semicircular lacerations of the face. None of the wounds formed the typical trapdoor deformity. Use of immediate Z-plasties in the acute management of semicircular flaplike lacerations seems to prevent the formation of the trapdoor deformity.     

A simplified algorithm for the use of Z-plasty

For the neophyte, the Z-plasty maneuver can be a surgical procedure veiled in intrigue. The theoretical mechanics of Z-plasty geometry are described, establishing that the new length of the central limb in a 60-degree Z-plasty is square root(3) of its original length. Factors such as skin tension, flap thickness, and flap location can, in application, distort the desired outcome. An algorithm is established that describes the indications and simplifies the execution of this technique.     

Good genes, old age and life-history trade-offs

The possibility of using old age of a mate as an indicator of genetic quality is currently controversial. Early verbal models as well as a recent simulation study noted that female choice for old mates is beneficial because longevity indicates viability in the current environment. In contrast, a quantitative genetic model of the relationship between age and breeding value of fitness casts strong doubts on the mechanism. The present analysis shows, however, that these doubts are mainly the result of assuming that all variation among individuals arises from differences in allocation between components of fitness. This neglects the possibility of variability in condition as a whole. Instead, when allowing for persistent variability in condition and assuming optimal reaction norms in allocation, it is shown that correlations between survival and genetic quality or fitness can easily be established at all ages. On the other hand, the results also suggest that the validity of verbal arguments is limited, and counterexamples can be generated where low-quality individuals should invest more in survival. Therefore, resolution of the old age indicator problem requires specification of the constraints acting on life-history characteristics.     

Mathematical principle of planar Z-plasty

To extend the work of precursors attempting to use Z-plasties with angles that have arbitrary degrees and may or may not be equal in size, a comprehensive study was done to clarify and simplify the correlation among the angles, limbs, and diagonals of the geometrical construction of Z-plasties. In geometry, the truth of a proposition must be proved; it is a question to which the answer must be found. By law and formula, a ternary trigonometric equation was derived from a simplified geometric diagram by a trigonometric approach. A procedure declaration accompanies this formula; neither was previously mentioned in the literature.     

Good genes and old age: Do old mates provide superior genes?

It has been suggested that female preference for older mates in species without parental care has evolved in response to an alleged higher genetic quality of older individuals. This is based on the widespread assumption that viability selection produces older individuals that are genetically superior to younger individuals. In contrast, we propose that the oldest individuals rarely are genetically superior. Quantitative genetic models of life history evolution indicate that young to intermediately aged individuals are likely to possess the highest breeding values of fitness. This conclusion is based on four arguments: 1) Viability selection on older individuals may decrease or at least not substantially increase breeding values of fitness, because there may exist negative genetic correlations between late-age and early-age life history parameters, 2) Fertility selection is likely to raise the fitness of gametes produced by young individuals more than those produced by old individuals, because the covariance between fertility and fitness often decreases with age, 3) The history of selection on their parents makes younger individuals more fit than older individuals, 4) Germ-line mutations, which are generally deleterious, significantly decrease the breeding value of fitness of an individual throughout its lifespan, especially in males. Therefore, females that mate with the oldest males in a population are doing so for reasons other than to obtain offspring of high genetic quality.     

Experience with the Furlow double-reversing Z-plasty for cleft palate repair

One-hundred and six cases of soft palate closure using the Furlow double-reversing Z-plasty technique have been reported. Most of these patients have been done in the past 2 years. There seem to be a number of worthwhile advantages to this procedure, with few disadvantages or complications. The operation is adaptable for use in early soft palate closure (3 to 6 months) as well as late closure (12 to 14 months), in submucosal clefts, as well as in secondary palatal repair where lengthening and repositioning of the levator muscle is desired. With this type of palatoplasty, the need for raising or shifting large mucoperiosteal flaps from the hard palate has been completely avoided. The operation can be combined with a primary posterior pharyngeal flap if desired, although this is not advised if early palatal closure (3 to 6 months) is used because of a high incidence of sleep apnea. Preliminary speech results are very encouraging.     

Radial half of extensor carpi radialis longus tendon as graft to elongate muscle tendon unit for correction of finger clawing

In 12 patients, the extensor carpi radialis longus muscle tendon unit was elongated using the radial half of the parent tendon so that it could reach the site of new insertion, the A1-A2 pulley of flexor sheath or lateral bands, after routing the transfer through the carpal tunnel. The tendon was of appropriate thickness and could be split into two halves to be used as a graft. Further splitting of the tendon into four tails was possible. The transferred slips retained adequate strength to activate the fingers after the operation. It is suggested that splitting of the extensor carpi radialis longus tendon to use one half as a tendon graft be considered in patients in whom extensor carpi radialis longus transfer is planned to correct finger clawing. This technique is simple, needs minor modification in the sequence of operative steps, reduces operating time, and saves the patient from postoperative discomfort, muscle herniation, and scarring at the donor site (usually the thigh).     

Computation of hemodynamics in the left coronary artery with variable angulations

The purpose of this study was to investigate the hemodynamic effect of variations in the angulations of the left coronary artery, based on simulated and realistic coronary artery models. Twelve models consisting of four realistic and eight simulated coronary artery geometries were generated with the inclusion of left main stem, left anterior descending and left circumflex branches. The simulated models included various coronary artery angulations, namely, 15°, 30°, 45°, 60°, 75°, 90°, 105° and 120°. The realistic coronary angulations were based on selected patient's data with angles ranging from narrow angles of 58° and 73° to wide angles of 110° and 120°. Computational fluid dynamics analysis was performed to simulate realistic physiological conditions that reflect the in vivo cardiac hemodynamics. The wall shear stress, wall shear stress gradient, velocity flow patterns and wall pressure were measured in simulated and realistic models during the cardiac cycle. Our results showed that a disturbed flow pattern was observed in models with wider angulations, and wall pressure was found to reduce when the flow changed from the left main stem to the bifurcated regions, based on simulated and realistic models. A low wall shear stress gradient was demonstrated at left bifurcations with wide angles. There is a direct correlation between coronary angulations and subsequent hemodynamic changes, based on realistic and simulated models. Further studies based on patients with different severities of coronary artery disease are required to verify our results.     

FEA analysis of Normofunctional forces on periodontal elements in different angulations

In the literature, the periodontal tissue reaction to dissimilar occlusal stress has been described, including clinical and histologic changes caused by stresses in periodontal structures. With respect to occlusal forces, periodontal assembly demonstrates varying adaptive capacity from individual to individual and period to period within the same individual. Unfortunately, these occlusal stresses are yet to be quantified. As a result, determining the effect of normal occlusal force on periodontal elements in various angulations is of interest. Based on CBCT images, one FEA of the maxillary First molar was created, consisting of tooth pulp, periodontal ligament (PDL), and alveolar bone; the effect of normal occlusal force on the pdl in alternate angulations was assessed. Occlusion will occur at three contact areas representing the centric occlusion contact points, each of which will share a 150 N force. The analysis was performed for four force inclinations (0, 22.5°, 45°, and 90°). Maximum stresses are observed in cases of 90-degree loading. These stresses, however, are insignificant and will not cause the periodontal components to rupture. These tensile stresses, which are concentrated in the apical and cervical regions, may obstruct blood flow, resulting in tooth decay or, in some cases, periodontal breakdown in PDL. There have been attempts to express numerical data of stress to be provided for normal and hyper function loads to simulate occlusal situations at various angulations that are known to be accountable for healthy and diseased periodontium.     

Nonuniform activation of the agonist muscle does not covary with index finger acceleration in old adults.

This study examined the patterns of activation in the superficial and deep parts of the first dorsal interosseus muscle and in the antagonist muscle, second palmar interosseus, during postural tasks (position holding) and slow movements (position tracking) of the index finger performed by young and old adults. The position-tracking task involved the index finger lifting light loads (2.5, 10, and 35% of maximum) with shortening and lengthening contractions as steadily as possible. Steadiness was quantified in both tasks as the standard deviation of index finger acceleration. The fluctuations in acceleration during the two tasks were greater for the old subjects (62-72 yr) compared with young subjects (19-27 yr), especially with the lightest loads. The two groups of subjects activated the superficial and deep parts of first dorsal interosseus at similar intensities during the position-holding task, whereas the deep part was more active during the shortening and lengthening contractions of the position-tracking task. The nonuniform activation of first dorsal interosseus, therefore, was not associated with the difference in the standard deviation of acceleration between the young and old subjects. Furthermore, there was no association between the average level of coactivation by the antagonist muscle and the standard deviation of acceleration for either group of subjects across these tasks. Thus the greater variability in motor output exhibited by the older adults could not be explained by either the nonuniform activation of the agonist muscle or the average level of coactivation by the antagonist muscle.