Wayne F. Larrabee

A finite element model of skin deformation. I. Biomechanics of skin and soft tissue: A review

Skin flap design has traditionally been based on geometric models which ignore the elastic properties of skin and its subcutaneous attachments. This study reviews the theoretical and experimental mechanics of skin and soft tissues (I) and proposes a mathematical model of skin deformation based on the finite element method (III). Finite element technique facilitates the modeling of complex structures by analyzing them as an aggregate of smaller elements.

Wound Tension and Blood Flow in Skin Flaps

The relationship between wound-closing tension, blood flow, and flap viability is examined using piglets as an experimental model. Twenty-seven rectangular skin flaps with random-pattern blood flow were created and closed under varying tensions. Closing tensions were accurately measured using a stabilized mechanical force gauge. In flaps with an impaired blood supply, there was a statistically significant increase in flap necrosis for those flaps closed with greater than 250 g of tension. The laser Doppler demonstrated a clear-cut inverse relationship between flap tension and blood flow in these flaps which correlated well with the experimental flap necrosis seen.

A finite element model of skin deformation. III. The finite element model.

Skin flap design has traditionally been based on geometric models which ignore the elastic properties of skin and its subcutaneous attachments. This study reviews the theoretical and experimental mechanics of skin and soft tissues (I) and proposes a mathematical model of skin deformation based on the finite element method (III). Finite element technique facilitates the modeling of complex structures by analyzing them as an aggregate of smaller elements.

A finite element model of skin deformation. II. An experimental model of skin deformation.

Skin flap design has traditionally been based on geometric models which ignore the elastic properties of skin and its subcutaneous attachments. This study reviews the theoretical and experimental mechanics of skin and soft tissues (I) and proposes a mathematical model of skin deformation based on the finite element method (III). Finite element technique facilitates the modeling of complex structures by analyzing them as an aggregate of smaller elements.

Frontal sinus fractures — their suppurative complications and surgical management

A series of 54 patients treated for frontal sinus fractures at Charity Hospital, New Orleans, from 1967‐77 is presented. There were a large number of suppurative complications related to the various medical and surgical managements.

The tracheoesophageal diversion and laryngotracheal separation procedures for treatment of intractable aspiration

Intractable aspiration is a severe and often fatal complication in patients with impaired protective function of the larynx. This problem is usually a result of central nervous system disorders such as cerebrovascular accident, trauma, neoplasms, or degenerative disease. Surgical separation of the upper respiratory tract from the digestive tract can prevent recurrent contamination of the respiratory system in these patients. Two such procedures are the tracheoesophageal diversion procedure and a modification of this operation, the laryngotracheal separation procedure. The Virginia Mason Medical Center experience with these procedures, their indications, technique, and outcome are presented. In addition, cases of successful surgical reversal of the diversion procedures are discussed.

The nasal dermoid.

Nasal dermoid cysts and sinus are rare congenital lesions believed to be related embryologically to the nasal glioma and encephalocele. Without recognition and treatment, growth of these lesions can cause nasal and midfacial disfigurement, recurrent localized infection, and symptoms consistent with an intranasal lesion (e.g., obstruction). If an intracranial connection exists, meningitis and its sequelae are possible. Two cases are reported to demonstrate salient features of the nasal dermoid.

Skin Flap Tension and Wound Slough: Correlation with Laser Doppler Velocimetry

The effects of wound tension on flap viability and blood flow are investigated in an animal model using the domestic piglet. In flaps with an impaired blood supply, wound closing tensions >250 g resulted in a significantly increased incidence of flap necrosis. The laser Doppler is a device of recent origin for the measurement of cutaneous blood flow. In this study, it provided a simple quantitative measure of the inverse relationship between skin tension and blood flow.

BONE-INDUCING IMPLANTS IN HEAD AND NECK SURGERY : AN EXPERIMENTAL STUDY

The use of autologous bone for head and neck reconstruction requires a separate harvesting procedure which provides limited quantities of bone that may become infected or undergo resorption after being implanted. In this study, a collagen/ceramic carrier containing osteoinductive factor extract (OFE) was used in a rabbit facial augmentation model. Bone-inducing activity of these implants were evaluated in subcutaneous, intramuscular, and subperiosteal sites. Implants with (test) and without OFE (control) were placed on opposite sides of the face in 40 rabbits, and were harvested at 21 days. Bone formation was evaluated by implant alkaline phosphatase determinations and histomorphometry. Osteoblastic activity, bone formation, and preservation of facial augmentation were noted in the OFE implants, showing maximal bone formation when implanted subperiosteally. Control (no OFE) and demineralized bone implants showed no bone formation. Before these implants can be used clinically, novel bone-inducing factors must be manufactured by recombinant deoxyribonucleic acid (DNA) methodology to verify activity of the homogeneous molecule which would be free of other proteins or infectious agents.

Nonsurgical correction of auricular deformities

There appears to be a sound physiologic basis reported in the literature for the success of nonsurgical reshaping of the ear shortly after birth. Cartilage is composed of a cellular component, the chondrocytes, and an extracellular matrix, consisting of collagen and proteoglycan aggregate. Proteoglycan is a macro‐molecule with a core of protein surrounded by many glycosaminoglycans (principally chondroitin sulfate and keratin sulfate) and a hyaluronic acid molecule. The proteoglycan molecule appears to be responsible for cartilage elasticity.6 One of the substances that has been shown to increase cartilage pliability is estrogen, which directly increases hyaluronic acid levels.7–8 At birth, there are very high circulating.