Intraoperative cervix location and apical support stiffness in women with and without pelvic organ prolapse.
BACKGROUND
It is unknown how initial cervix location and cervical support resistance to traction, which we term "apical support stiffness," compare in women with different patterns of pelvic organ support. Defining a normal range of apical support stiffness is important to better understand the pathophysiology of apical support loss.


OBJECTIVE
The aims of our study were to determine whether: (1) women with normal apical support on clinic Pelvic Organ Prolapse Quantification, but with vaginal wall prolapse (cystocele and/or rectocele), have the same intraoperative cervix location and apical support stiffness as women with normal pelvic support; and (2) all women with apical prolapse have abnormal intraoperative cervix location and apical support stiffness. A third objective was to identify clinical and biomechanical factors independently associated with clinic Pelvic Organ Prolapse Quantification point C.


METHODS
We conducted an observational study of women with a full spectrum of pelvic organ support scheduled to undergo gynecologic surgery. All women underwent a preoperative clinic examination, including Pelvic Organ Prolapse Quantification. Cervix starting location and the resistance (stiffness) of its supports to being moved steadily in the direction of a traction force that increased from 0-18 N was measured intraoperatively using a computer-controlled servoactuator device. Women were divided into 3 groups for analysis according to their pelvic support as classified using the clinic Pelvic Organ Prolapse Quantification: (1) "normal/normal" was women with normal apical (C < -5 cm) and vaginal (Ba and Bp < 0 cm) support; (2) normal/prolapse had normal apical support (C < -5 cm) but prolapse of the anterior or posterior vaginal walls (Ba and/or Bp ≥ 0 cm); and (3) prolapse/prolapse had both apical and vaginal wall prolapse (C > -5 cm and Ba and/or Bp ≥ 0 cm). Demographics, intraoperative cervix locations, and apical support stiffness values were then compared. Normal range of cervix location during clinic examination and operative testing was defined by the total range of values observed in the normal/normal group. The proportion of women in each group with cervix locations within and outside the normal range was determined. Linear regression was performed to identify variables independently associated with clinic Pelvic Organ Prolapse Quantification point C.


RESULTS
In all, 52 women were included: 14 in the normal/normal group, 11 in the normal/prolapse group, and 27 in the prolapse/prolapse group. At 1 N of traction force in the operating room, 50% of women in the normal/prolapse group had cervix locations outside the normal range while 10% had apical support stiffness outside the normal range. Of women in the prolapse/prolapse group, 81% had cervix locations outside the normal range and 8% had apical support stiffness outside the normal range. Similar results for cervix locations were observed at 18 N of traction force; however the proportion of women with apical support stiffness outside the normal range increased to 50% in the normal/prolapse group and 59% in the prolapse/prolapse group. The prolapse/prolapse group had statistically lower apical support stiffness compared to the normal/normal group with increased traction from 1-18 N (0.47 ± 0.18 N/mm vs 0.63 ± 0.20 N/mm, P = .006), but all other comparisons were nonsignificant. After controlling for age, parity, body mass index, and apical support stiffness, cervix location at 1 N traction force remained an independent predictor of clinic Pelvic Organ Prolapse Quantification point C, but only in the prolapse/prolapse group.


CONCLUSIONS
Approximately 50% of women with cystocele and/or rectocele but normal apical support in the clinic had cervix locations outside the normal range under intraoperative traction, while 19% of women with uterine prolapse had normal apical support. Identifying women whose apical support falls outside a defined normal range may be a more accurate way to identify those who truly need a hysterectomy and/or an apical support procedure and to spare those who do not.
Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI. Electronic address: scarolyn@med.umich.edu.
Carolyn W
CW
Swenson
Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI.
Tovia M
TM
Smith
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI.
Jiajia
J
Luo
Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI.
Giselle E
GE
Kolenic
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI.
James A
JA
Ashton-Miller
Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI.
John O
JO
DeLancey
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002584:Cervix Uteri / Q000473:pathology / Q000503:physiopathology*; D052858:Cystocele / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008875:Middle Aged; D056887:Pelvic Organ Prolapse / Q000503:physiopathology; D020047:Rectocele / Q000503:physiopathology*; D014596:Uterine Prolapse / Q000503:physiopathology*
apical support stiffness; cervix location; prolapse