Engineering analysis of penile hemodynamic and structural-dynamic relationships: Part II—Clinical implications of penile buckling

Abstract

Purpose: Penile buckling force was analytically described in terms of its constituents. In addition, theoretically-derived buckling force data were compared to clinically measured data and the in¯uence of each constituent on penile buckling force data was assessed. Methods: Using engineering buckling theory for a column, a mathematically-derived penile buckling model was developed which incorporated geometric and hemodynamic data obtained by dynamic infusion pharmacocavernosometry studies in 21 impotent patients (age 43, range 24±62 y) as well as penile tissue mechanical characteristics previously developed (Part I). Results: In 17 of 21 patients the mean difference between theoretically derived and clinically measured buckling force data was 0.33 AE 0.25 kg (r 0.96). Factors which increased penile buckling forces were: (1) high intracavernosal pressure values (rigidity was related to pressure in an exponential-like fashion); (2) high penile aspect ratio (D/L) values (relatively large diameter/ short length penile geometry) and high¯accid diameter; and (3) high cavernosal expandability values (a measure of the ability of the corpora to approach its erect volume with relatively low intracavernosal pressures). Conclusions: Pressure-volume data (pressure, geometry and tissue characteristics) obtained during erectile function testing have been shown, for the ®rst time, to theoretically predict the magnitude of clinically-measured penile buckling forces.

Engineering analysis of penile hemodynamic and structural-dynamic relationships: Part III—Clinical considerations of penile hemodynamic and rigidity erectile responses

“…The major factors which predict high penile buckling forces other than high values of intracavernosal pressure are high values of cavernosal expandability, high values of penile aspect ratios and high accid penile diameters. 2 Patients (such as 19 and 11 in this study) exist who have high equilibrium pressure values (based on normal or relatively normal hemodynamic in¯owaout¯ow criteria) and who, in addition, have low cavernosal expandability values andaor low penile aspect ratios andaor low¯accid penile diameters. Such patients may have inadequate penile buckling forces and erectile impotence.…”

“…2 A series of analyses were performed (Part III) to further examine the relationship between the erectile hemodynamic variables described above and the constituents of penile buckling force.…”

“…1 Although penile rigidity usually follows normal physiologic hemodynamic erectile responses, there are situations where the quality of penile rigidity does not directly correlate with the quality of the physiological hemodynamic erectile responses. 2 Such disparities between penile rigidity and hemodynamic responses are confusing both to patients and clinicians. For example, penile rigidity may develop despite hemodynamic impairments, that is, where the equilibrium intracavernosal pressure is lower than the normal physiologic hemodynamic value responses.…”

“…For example, penile rigidity may develop despite hemodynamic impairments, that is, where the equilibrium intracavernosal pressure is lower than the normal physiologic hemodynamic value responses. 2 In such cases, patients may possess the ability to have satisfactory intercourse despite the recording of abnormal hemodynamic integrity by such studies as duplex Doppler ultrasonography 3 or dynamic pharmacocavernosometry. 4 On the other hand, penile rigidity may be inadequate despite the observation of normal physiologic hemodynamic erectile responses by erectile function testing.…”

“…Such patients have often been classi®ed as having psychogenic impotence but physical factors other than hemodynamic variables have been shown to affect the magnitude of penile buckling forces. 2 There has been a paucity of investigation concerning the relationships between hemodynamic responses and penile rigidity responses. Hemodynamic testing procedures predict in¯ow and out¯ow parameters, while penile buckling forces predict the ability of the erection to prevent deformation following vaginally-mediated axial loading.…”