ENGINEERING ANALYSIS OF PENILE HEMODYNAMIC AND STRUCTURAL-DYNAMIC RELATIONSHIPS - PART I - CLINICAL IMPLICATIONS OF PENILE TISSUE MECHANICAL-PROPERTIES

Purpose: The least investigated physical determinant of penile rigidit y has been penile tissue material properties. The goals in this study (Part I) were to define two penile mechanical parameters, cavernosal e xpandability X and tunical distensibility V-E/V-F, determine their mag nitudes in humans and develop an analytical expression for penile volu me as a function of these two tissue characteristics and intracavernos al pressure. Methods: Dynamic infusion pharmacocavernosometry was perf ormed in 21 impotent patients (age 43+/-19y) to provide human geometri c, hemodynamic and structural data. A mathematically derived model of hemodynamic and structural-dynamic characteristics of penile erection was developed (Parts I, II, III) incorporating penile tissue mechanica l qualities. Results: Cavernosal expandability X provided a measure of the ability to approach maximum volume at relatively low intracaverno sal pressures. Tunical distensibility V-E/V-F denoted the maximal erec t to flaccid penile volume ratio. The magnitudes of X and V-E/V-F in t he study population were 0.04-0.17 mmHg(-1) and 1.7-5.0 respectively. Conclusions: Enabling penile volume to be derived as a function of tis sue mechanical characteristics and pressure, allows for penile rigidit y to be expressed (in Part II) as a function of pressure, geometry and tissue qualities.