Investigating the Mechanisms of Intradermal Injection for Easier "Skin Booster" Treatment: A Fluid Mechanics Approach to Determine Optimal Delivery Method.

Background: The use of "skin boosters" for rejuvenating aged skin is widely used. However, the accurate injection of the skin booster into the dermal layer remains a challenge due to the density of the dermis. The purpose of this study was to investigate the optimal mechanical variables of delivery that enabled correct targeting of the product to the dermis for optimal results. Methods: We investigated the impact of mechanical variables (syringe diameter, needle diameter and length, and viscosity of the skin booster) on the force required for intradermal injection in porcine skin. The correlation between these variables and the injection force was examined as well. Results: The results show that smaller syringe diameters, larger needle diameters, shorter needle lengths, and lower viscosity of the skin boosters reduce the injection force needed for intradermal injections. Conclusions: During the administration of skin booster injections, clinicians should take into account optimal conditions that facilitate intradermal injections, thus maximizing rejuvenating outcomes. Furthermore, manufacturers of skin boosters should formulate the products with decreased viscosity and provide the product in conjunction with appropriate needles and syringes, designed to optimize ease of injection.

Anatomic basis of interfascicular nerve splitting of innervated partial latissimus dorsi muscle flap.

PURPOSE: To study the anatomic basis for the interfascicular nerve-splitting technique applied to the innervated latissimus dorsi muscle flap to preserve the remnant muscle function. Cadaveric dissection was performed to study the distribution of the thoracodorsal nerve and artery, and simulation of the surgical technique was also executed. METHODS: A total of 42 latissimus dorsi muscles from 21 preserved cadavers were dissected, and the distribution of the nerves and arteries were studied. The thoracodorsal neurovascular bundles were identified entering the muscle, and the distance from the upper margin and lateral margin of the muscle, and the distance from the angle of scapula were measured. The distance from the brachial plexus to the branching of the thoracodorsal nerve were measured and the distance between the branching of the nerve and artery were also measured. Interfascicular splitting of the thoracodorsal nerve was performed under operating microscope and the validity of the technique was confirmed by histology. RESULTS: The thoracodorsal neurovascular bundle entered the muscle at a distance of 39.1 ± 8.8 mm from the upper margin, and 23.8 ± 10.3 mm from the lateral margin. In addition, from the angle of scapula, the distance was 47.8 ± 17.8 mm in the transverse axis, and 48.9 ± 13.5 mm in the sagittal axis. The distance from the brachial plexus to the first branching of the thoracodorsal nerve was 78.5 ± 11.0 mm, and distance to the second branching was 96.3 ± 12.9 mm. The thoracodorsal nerve always branched before the artery, and the distance from the first branching of the nerve to the first branching of the artery was 20.4 ± 8.9 mm. Interfascicular dissection of the nerve was performed under operating microscope, by opening the epineurium and splitting the fascicles with utter care not to injure the perineurium. This procedure was very similar to splitting a wire cable. Histological analysis of the dissected nerve confirmed that the interfascicular dissection was performed without injuring the fascicules and the perineurium was intact. CONCLUSION: We simulated and confirmed that the preservation of the remnant muscle function was possible by using the nerve-splitting technique in the innervated latissimus dorsi muscle flap. It is easy and simple to separate the nerve branch entering the muscle flap from the nerve branch entering the remnant muscle without injury, which results in increasing the nerve length while preserving the muscle function of the donor site. Further, the distribution of the thoracodorsal neurovascular bundle was studied in 42 muscles, which can be used as a reference point during surgery. With this novel technique, preservation of the remnant muscle function is possible when using innervated muscle flaps, which can be applied in areas such as reconstruction of facial paralysis and reconstruction of the chest wall in Poland syndrome.

Anatomic study of the nostril sill: classification and histologic findings.

To define and investigate the normal nostril sill anatomy and classify the different forms.Photographs of the nose of 95 Korean adults and 26 preserved cadavers were studied. Classification of the different forms and cadaveric dissections and histologic studies were performed. Morphologically the noses were studied and classified into 3 types, and histologically the thickness of the soft tissue and muscle layers were measured at the nostril sill.The nostril sill was defined as the soft tissue bulge between 4 borders; medially the foot plate of the columella, laterally the ala, cephalically the vestibule, and caudally the upper lip, and classified into 3 forms. Type I: full nostril sill (55.7%), type II: point nostril sill (31.9%), and type III: flat nostril sill (12.1%). On histologic analysis, in type I, the sill consisted of fibro fatty tissue composed of a mixture of dermal collagen and gland which were thicker at the area of the sill. Also the muscle fibers beneath the sill were more protuberant in this area. The thickness of the soft tissue and muscle layers were significantly thicker at the sill area than the upper lip and vestibule. In types II and III, dermal thickening was not observed and the soft tissue thickness remained unchanged from the upper lip to the nasal vestibule. The muscle fibers showed no protuberance under the sill.This study provides references which will allow more accurate and proper correction and reconstruction of the nose and nostril sill.

The effects of tadalafil on axial-pattern skin flap survival in rats.

BACKGROUND: Pharmacologic augmentation to mimic the delay phenomenon that increases skin flap survival has been studied extensively. Tadalafil is a phosphodiesterase V inhibitor that is used for treatment of erectile dysfunction by enhancing vascular smooth muscle relaxation. OBJECTIVE: The aim of this study was to investigate the effects of local injection of tadalafil in enhancing axial-pattern skin flap survival in rats. MATERIALS AND METHODS: Twenty Sprague-Dawley rats were used and a McFarlane-type caudally based axial-pattern skin flap was designed on the dorsum of the rat (2 x 9 cm). Rats were divided into two groups: the treatment group and the control group. Tadalafil 10 mg/kg/day was injected to the distal flap area of the treatment group for 3 days, and normal saline was injected for the control group. On Postoperative Day 7, necrotic flap area was measured and compared, and angiograms of the skin flaps were obtained in the two groups. RESULTS: In the treatment group, the mean necrotic area was 21.9+/-6.4%, and in the control group, 37.7+/-5.9%. There was a statistically significant increase of skin flap survival in the treatment group (p=.001). Angiography also showed vasodilation of the choke vessels between adjacent angiosomes to form true anastomosis in the treatment group. CONCLUSION: The results demonstrate that the use of local injection of tadalafil to failing skin flaps increases the survival of axial-pattern flaps in rats.

Functional reconstruction of the philtral ridge and dimple in the repaired cleft lip.

Our report describes a simple method of functional reconstruction of the philtral ridge in patients with repaired cleft lip. Philtral reconstruction was performed in 21 children with dehiscence of the orbicularis oris in repaired cleft lip. Prominent groove at the philtral column and lateral bulging during maximal "pucker" were the indications. First, the abnormally inserted orbicularis muscle is freed and realigned in a normal horizontal orientation. The muscle is vertically incised and repaired with vertical mattress sutures, spreading out the muscle to increase the thickness of the philtral ridge. The philtral ridge is accentuated by deepening the dimple with a dermal suture at the midline. Postoperative evaluation was performed at 8-18 months (mean; 13.1 months). The philtrum was evaluated by a panel using two visual scales. Eminence of the philtral ridge was scored by a five-point grading scale and the philtral dimple was scored by a three-point grading scale, both at resting and at maximal pucker. Preoperative scores showed the philtral ridge to be from "prominent groove" to "flat" at maximal pucker and at rest, respectively. Postoperative scores showed improvement of the philtral ridge to "less prominent than the normal philtral ridge" both at rest and at maximal pucker. The philtral dimple preoperative scores ranged from "no dimple" to "slight dimple" and postoperative improvement to "slight dimple" to "prominent dimple." This technique of functional reconstruction of the philtrum gave satisfactory results in formation of the philtral ridge and dimple, both at rest and at maximal pucker.