Biomedical subjects

R K Daniel

Publications and source records attributed to R K Daniel.

At least 37 records · Page 2Linked to original sources

PubMed1988

The superficial musculoaponeurotic system of the nose.

Thirty noses were examined macroscopically and histologically to determine the fibromuscular and aponeurotic layers. There are five soft-tissue components beneath the dermis: a superficial fatty panniculus, a fibromuscular layer, a deep fatty layer, a longitudinal fibrous sheet, and an interdomal ligament. The nose is covered by a nasal SMAS, which forms part of the SMAS of the face. The continuous fibromuscular layer interconnects the musculature through aponeuroses, thus distributing their forces. The alar muscles change the transnasal pressure of the nasal valve, affecting respiration. To preserve the integrity of the nasal soft-tissue layers, one may elevate the soft-tissue envelope beneath the nasal musculature.

Aged↗

PubMed1987

Rhinoplasty: creating an aesthetic tip. A preliminary report.

A new approach for creating an anatomically aesthetic nasal tip is presented. It is based on extensive cadaver dissections which demonstrate that a convex domal segment plus a sharp domal segment-lateral crural drop-off are key determinants of a refined tip. This configuration can be achieved with sutures in a manner similar to creating the anthelical curl in an otoplasty. Two operative variations are presented. One achieves tip refinement with a limited increase in projection, while the other provides maximum projection. Currently, the technique is of value in bilateral cleft lip noses, posttraumatic deformities, certain secondary cases, and very selected primary aesthetic cases where tip refinement and projection are limited.

Adult↗

PubMed1987

Rhinoplasty: a CT-scan analysis.

In order to assess the postoperative consequences of various rhinoplasty techniques, CT scans were done in 35 patients having a rhinoplasty operation. This series can be subdivided into those having preoperative and postoperative scans at both 2 days and 6 months (15 patients), a postoperative scan only at 48 hours (10), or a long-term postoperative scan at a mean of 12 months (10). Preoperative analysis indicates that a wide variation exists in lateral nasal wall anatomy and angulation. Surgically, the lateral nasal walls undergo limited medial movement, with tilt a significant component. Postoperatively, extensive remodeling can occur, and virtually all osteotomies are healed by osseous union at 6 months. Future application of CT scans in severely deviated noses may be justified.

Adult↗

PubMed1986

Neuroanatomical evidence of reinnervation in primate allografted (transplanted) skin during cyclosporine immunosuppression.

Histological evidence is presented documenting the reinnervation of sensory mechanoreceptors across major histocompatibility barriers in allografted primate (baboon) skin. Meissner and pacinian corpuscles, as well as hair follicles, showed a spectrum of reinnervation by host axons. Our light and electron microscopic evidence to date has suggested that allografted Merkel cells did not survive transplantation. This, and other instances of tissue and receptor destruction resulting from histoincompatibility, indicated marked differences when skin allografts were compared to autografts with respect to the ability of host axons to locate and reinnervate sensory mechanoreceptors.

Animals↗

PubMed1986

Tissue transplants in primates for upper extremity reconstruction: a preliminary report.

Recent advances in clinical transplantation surgery suggest that hand transplantation is no longer an unrealistic expectation. However, two questions must be answered. Can composite tissue transplants survive in a primate species? Does the required neural reinnervation occur under immunosuppression? Four hand transplants and seven neurovascular free flap transplants were done in baboons immunosuppressed with Cyclosporin A and steroids (methylprednisolone). Long-term survival occurred in nine. Electrophysiologic tests of sensory axons revealed reinnervation of transplanted skin as evidenced by well-defined, low threshold receptive fields in the donor tissue. Reinnervation of donor muscle was demonstrated by motor unit recruitment in stepwise fashion after electrical stimulation of the recipient's median and ulnar nerves. Afferent fibers serving the donor's joints and muscle spindles were also observed.

Animals↗

PubMed1986

Primary and secondary critical ischemia times of myocutaneous flaps.

The primary critical ischemia time of the latissimus dorsi myocutaneous flap model was determined in the pig. Latissimus dorsi flaps were subjected to a primary ischemic insult of 2 hours (mimicking the ischemic event of free-tissue transfer). Following 12 hours of normal flow, the flaps were subjected to a second ischemic insult ranging from 0 to 12 hours. The secondary critical ischemia time (11.3 hours) was found to be statistically comparable to the primary critical ischemia time (9.1 hours). Questions are raised concerning the mechanism of action of this phenomenon and its clinical relevance.

Animals↗

PubMed1986

Free tissue transfers to the upper extremity.

With the expanded surgical options provided by free tissue transfers, upper extremity reconstruction has progressed to a level of greater finesse. Recognizing the ideal tissue for restoration of function and aesthetics, thin skin dorsally and sensate glabrous skin volarly, is the first step to effective application of microsurgery in the hand. With complex deformities, all missing components must be considered and the patient's goals realistically defined. An in-depth understanding of hand function is combined with an exhaustive knowledge of free tissue donor sites and a reconstructive plan is formulated. Staged reconstruction may be necessary, depending on the complexity of the problem. Ideal donor tissues are not always available, but it is expected that advances in immunology will soon make "spare part surgery" a viable alternative.

Adult↗

PubMed1985

Surgical anatomy of septorhinoplasty.

Anatomic studies of the nose were done in 60 cadavers, both fresh and embalmed, allowing correlation of surgical anatomy and operative techniques. All septorhinoplasties were performed on fresh cadavers, using a clinical instrument set and head lamp. In addition, the alar cartilages were assessed in 25 patients undergoing external rhinoplasty. This multifaceted study provided an integrated approach to nasal anatomy.

Esthetics↗

PubMed1985

Pressure sores and paraplegia: an experimental model.

An investigation into the effect of spinal cord transection on pressure sore development is presented and the critical importance of soft tissue atrophy is examined. A technique of spinal laminectomy and spinal cord transection was developed in pigs and shown to have a minimal morbidity rate. Following tissue atrophy, pressure was applied to the paraplegic animals for varying durations. Pressure application was achieved by a computer-controlled application system. The experimental model produced pressure sores extending down to the bone. The resulting tissue damage was assessed, graded, and a pressure-duration curve for paraplegic animals established.

Animals↗

PubMed1984

Experimental electrical burns: low voltage.

Low-voltage electrical burns were studied in 25 pigs submitted to bilateral thigh burns using 500 volts AC for 10 seconds. In a group of 6 animals, the wounds were observed and histologic specimens obtained at different intervals during the first week. The burn measured approximately 4 cm in diameter and extended through two muscle layers. This tissue underwent further necrosis during the first 48 hours. After 2 days there was no further necrosis. In a second group, the wounds were debrided and covered with either a split-thickness skin graft or a rectus abdominis musculocutaneous flap. All wounds with flap coverage healed primarily and there was no deep necrosis. From our findings we conclude that debridement and definitive closure can safely be performed 2 days after low-voltage electrical burns.

Animals↗

PubMed1984

Skin flap research: a candid view.

To better understand skin flap research, three pivotal papers of the last decade are reviewed. The validity of Milton's questioning the accepted length to width ratio is confirmed, whereas the shunt theory of skin flap failure is rejected, and the value of isoxsuprine treatment for preventing flap failure is debated. Current trends in three other areas of skin flap research are highlighted--skin flap metabolism, skin flap monitoring, and the use of musculocutaneous flaps for contaminated wounds.

Evaluation Studies as Topic↗

PubMed1984

An anastomotic device for microvascular surgery: evolution.

A new anastomotic device is demonstrated that is suitable in microvascular surgery for repairing severed blood vessels and inserting vein grafts. Initial pilot studies indicate a 100% patency rate for vessel anastomosis, and a one-year study produced a 96% success rate. However, histological examination revealed notable vessel deterioration with a rigid device. Therefore, an absorbable anastomotic coupler was developed that demonstrates a high patency rate (92%) in both arteries and veins, with substantial absorption of the device by 70 days. Healing at the anastomotic site was qualitatively similar to that obtained with a sutured anastomosis; there was endothelialization by 14 days and absorption of the device by 70 days.

Animals↗

PubMed1984

Experimental models in primates for reconstructive surgery utilizing tissue transplants.

Two experimental models for tissue transplantation between unrelated individuals of a primate species have been designed to study survival and reinnervation. The first is a neurovascular free flap consisting of the entire soft tissue coverage of the index finger. The second is an entire hand transplant through the distal forearm. Ongoing studies show that cyclosporin A at high doses, in combination with a tapering regimen of steroids to a low maintenance level, permits prolonged survival of both transplant models. Careful biochemical, hematological, and cyclosporin A serum trough level monitoring permits use of this drug a very high dosages in primates. Continuing experiments should yield detailed neurophysiological data on the reinnervation of these transplants over the next 6 to 18 months.

Animals↗

PubMed1984

Rhinoplasty: a graded aesthetic-anatomical approach.

The fundamental rhinoplasty principles established by Joseph and the aesthetic canons of Sheen can be reconciled by selecting the optimal surgical technique based on in-depth anatomical knowledge. Since neither the perfect nose nor the perfect rhinoplasty operation exists, the goal remains to choose those procedures best suited for the individual patient. The greater the surgeon's commitment and repertoire, the higher the chances of success.

Adult↗

PubMed1984

An absorbable anastomotic device for microvascular surgery: experimental studies.

A new absorbable anastomotic device is presented. Over 200 anastomoses were done in the rabbit's carotid artery and posterior facial vein with an overall patency rate of 96 percent. Follow-up extended to 1 year in certain series. Its advantages over other devices include a consistently high patency rate, complete absorption by 70 days, lack of intraluminal foreign body, and simple instrumentation. Its principle advantage over suture anastomosis is a shortened insertion time (5 minutes). However, it does require additional vessel length for eversion and a skilled assistant. It can accommodate only limited vessel size discrepancies and has no capability for end-to-side anastomoses.

Absorption↗

PubMed1984

An absorbable anastomotic device for microvascular surgery: clinical applications.

An absorbable anastomotic device that can be inserted in less than 4 minutes for vessels with a 1.3- to 2.5-mm diameter was utilized in 20 clinical cases. Only one documented thrombosis occurred, and it was successfully revised. In 11 of 20 cases, tissue survival was totally dependent on the coupled anastomosis. Subsequent follow-up offers evidence of maintained patency. It would appear that anastomotic devices are a useful adjunct for the experienced microsurgeon skilled in suture techniques.

Absorption↗

PubMed1984

Secondary critical ischemia time of experimental skin flaps.

Secondary ischemia time represents the interval between a postoperative vascular thrombosis of a free flap and its successful revascularization. Using an island-flap model in pigs, the skin was found to tolerate an average secondary ischemia time of 7.2 hours. The safe secondary critical ischemia time (10 percent probability of necrosis) is 4.7 hours. This compares with the primary ischemia times of 13.1 hours (average) and 7.0 hours (10 percent necrosis). The discrepancies between these observed values are discussed.

Animals↗

PubMed1984

The morphology and patency of arterial and venous microvascular anastomoses throughout the first post-operative year. A histological study.

End-to-end microvascular suture anastomoses, 40 arterial and 41 venous, from the rabbits carotid artery and posterior facial vein were harvested at 5 different time intervals (1, 2, 3, 6 and 12 months) post surgery and evaluated with light microscopy. A 100% long-term patency was noted both in arteries and veins. Quantitative measurements of the width of the vessel wall components indicated that a statistically significant temporary hypertrophic response occurred in the arterial intima, culminating in the third month when the width of the vessel wall at the anastomotic level almost doubled the normal. After that the width of the vessel wall again declined but it remained thicker than the adjacent vessel wall at one year post surgery. Among the venous anastomoses, however, the wall thickness at the anastomotic level remained thinner than the adjacent vessel wall throughout the evaluation period. The original vessel wall characteristics are not restored at the anastomotic site with intimal hyperplasia compensating for medial necrosis. Despite these events a technically satisfactory microvascular anastomosis should remain patent for years.

Animals↗