The Sacrum and Coccyx

Superior articular processes of Sacrum

-Articulate with the inferior articular processes of L5 and form the lumbo-sacral junction -

Ala

-Broad, expanded portion of the upper sacral segment

Location of Sacrum

-Directly inferior to the lumbar spine -Between the 2 innominate bones, forming the posterior aspect of the pelvic cavity

Location of Coccyx

-Directly inferior to the sacrum -Most inferior portion of the spinal column

General Description of Sacrum

-Formed by the fusion of the five sacral vertebral segments into a curved, triangular bone.

Vertebral foramen

-Forms a descending tunnel called the sacral canal

Evaluation Criteria, AP Axial Sacrum

-No foreshortening -No overlapping by pubic bones -No rotation, as indicated by symmetric alae -Centered and seen in it's entirety -Tight collimation -No overlapping by fecal material

Anatomical characteristics of the Sacrum

-Only bony anatomy considered to be part of both the axial and appendicular skeleton -Shaped like an inverted triangle -Presents left and right borders which articulate with the innominate bones

Evaluation Criteria, AP obl. SI Joints

-Open sacroiliac joint space with minimal overlapping of the ilium and sacrum

Sacral foramina

-Provide passageways for the sacral nerves through both the anterior and posterior sides of the sacrum

Evaluation Criteria, AP Axial Coccyx

-Segments not superimposed -Short-scale contrast -No rotation -Centered and seen in it's entirety -Tight collimation

Evaluation Criteria, LAT Sacrum and Coccyx

-Short-scale contrast -Use of tight collimation and lead rubber absorber behing the sacrum -Closely superimposed posterior margins of the ischia and ilia

Breathing Instructions LAT Coccyx

-Suspend Respiration

Breathing Instuctions, LAT Sacrum

-Suspend on Expiration

Sacro-coccygeal articulation

-The superior articulating processes on the superior aspect of the coccyx articulates with the inferior segment of the sacrum

CR placement, AP Obl. SI Joints LPO/RPO

1" medial to ASIS

Film size, and Collimation, ALL Sacrum views

10X12 LW B, 8 by 8 collimation

Film size and Collimation, Obl. SI Joints

10X12 LW B, FFC

CR placement, LAT Coccyx

2" inferior, and 3 1/2" posterior to ASIS

CR placement, LAT Sacrum

3 1/2" posterior to ASIS

Number of Sacral Foramina

4 pairs of foramina

Film size, and Collimation, LAT Coccyx

8X10 LW B, 6 by 6 collimation

Film size, Collimation, and CR, AP Axial Coccyx

8X10 LW B, 6 by 6 collimation, Align MSP, 2" superior to symphysis pubis

CR placement, AP Axial Sacrum

Aligned to MSP, and 2" superior to symphysis pubis