Shortest diameter of pelvic outlet:
Ans- B Inter tuberousRef.: D.C. Dutta 8th ed. / 94-97; William's 23rd ed. Chapter 2, Maternal Pelvic Anatomy* Most of the students answer interspinous for this question. Obviously interspinous is having the least diameter (10cm)y but it belongs to mid pelvis.* The question is asking about the shortest diameter of pelvic outlet, which is inter-tuberous (diameter between ischial tuberosity) diameter ~ 11cm.PLANES AND DIAMETERS OF THE PELVISThe pelvis is described as having four imaginary planes:* The plane of the pelvic inlet--the superior strait* The plane of the mid pelvis--the least pelvic dimensions* The plane of the pelvic outlet--the inferior strait* The plane of greatest pelvic dimension--of no obstetrical significance.Summarized data of maternal Pelvis planes and diameters (all the numerical data are derived from standard reference i.e. William's 23rd ed.)PlaneDiameterMeasured BetweenSizeTransverseGreatest distance between the linea terminalis on either side~ 13 cmA-P diameter aka true conjugateExtends from the uppermost margin of the symphysis pubis to the sacral promontory11cmOblique diameterExtends from one of the sacroiliac synchondroses to the iliopectineal eminence on the opposite side.12 cmInterspinous diameterBetween the ischial spines10cmAnteroposteriorAt the level of ischial spine11.5cmAntero-posteriorCoccyx to symphysis pubis11.5 cmTransverseBetween ischial tuberosities11 cmPosterior sagittalSacro-Coccygeal angle to the midline imaginary line at base11.5/2 cmObstetrical conjugateShortest distance between the sacral promontory and the symphysis pubis10 cm. the obstetrical conjugate is estimated indirectly by subtracting 1.5 to 2 cm from the diagonal conjugateDiagonal conjugatefrom the lower margin of the symphysis to the sacral promontory11.5-12 cm
Antero-posterior
Inter tuberous
Oblique
Inter-spinous