Ethnic variation in pelvimetric measures and its impact on positive surgical margins at radical prostatectomy

Abstract

Objectives: We sought to evaluate the ethnic variation in pelvimetry and its impact as a predictor of positive surgical margins (PSM) at radical prostatectomy (RP).

Methods: Preoperative MRI was performed in 482 Caucasian and 103 African American (AA) men undergoing RP without previous treatment from July 2003 to January 2005 and November 2001 to June 2007, respectively. We measured bony and soft tissue dimensions on magnetic resonance imaging (MRI) to evaluate the pelvic inlet, midplane, prostate size, and apical depth. Analysis of covariance was performed to determine the effect of ethnicity on the midpelvic area (MPA). We performed multivariate logistic regression analysis for prediction of overall and site-specific PSM.

Results: AA men had a significantly steeper symphysis pubis angle (median, 43.1 vs. 41.3°, respectively, P = .001) and smaller MPA (median, 78.5 vs. 83.9 cm(2), respectively, P = .004). Ethnicity and BMI were found to have a significant effect on MPA. Apical depth of the prostate was identified as a significant independent predictor of apical PSM, with a more pronounced effect in AA men. Pelvimetric measures were not a significant predictor of other sites of PSM.

Conclusions: AA men have a significantly smaller MPA and steeper symphysis angle. The adverse impact of a deep pelvis, as measured by the apical prostatic depth on apical PSM was found to be greater in AA men. Evaluation of pelvic dimensions and prostate parameters in preoperative MRI may add to our understanding of their impact on surgical outcomes.

Figure 1

A: Upper conjugate defined as distance from the innermost aspect of the top of the symphysis pubis to the sacral promontory. B: Height of prostate defined as orthogonal distance from top of symphysis pubis to base of prostate. C: Depth of prostate defined as orthogonal distance from top of symphysis pubis to apex of prostate. D: Symphysis angle: defined as angle between the long axis of the symphysis pubis and the horizontal. E: Lower conjugate defined as distance from lower inner symphysis pubis to sacrococcygeal junction. F: Bony femoral width defined as bony width of the pelvis at the mid-femoral head level. G: Interspinous distance defined as distance between the tips of the ischial spines. H: Width of prostate at the same level as soft tissue width. I: Soft tissue width defined as narrowest distance between the levator muscles. J: Demonstration of the mid-pelvic area (MPA).