Sacrum
The sacrum consists of the five fused sacral vertebrae which are treated for analysis as a single unit. Only the anterior and posterior epiphyses on the body of the element are considered when coding whether the element is fused or un-fused. Loose un-fused anterior or posterior epiphyses unassociated with the rest of the element are coded as being of weathered condition and undifferentiated BU. Epiphyses on the spinous and transverse processes are ignored in considering element fusion. When isolated un-fused epiphyses from the spinous or transverse processes are identified, they are coded as “undifferentiated” BU.
For the Fincastle Project, Bone Unit 22 was added.
BU 1
SC A
Complete element
BU 15
SC B
Fused 1st – 3rd or 4th sacral vertebrae. Ala complete. Medium crest and lateral sacral crests may be damaged. (DS)
BU 21
SC C
Unit consists of complete first to second sacral vertebra, which may or may be fused. (WU)
BU 18
SC D
Body of 1st sacral vertebra with all or most of both wings present. Arch intact and may or may not show evidence of crushing along crest. (MB)
BU 19
SC E
Unit is complete, with the exception that the first sacral vertebra is missing one ala. (WU)
BU 20
SC F
Unit consists of fused 1st – 3rd sacral vertebra. The first vertebra only has one ala, and the dorsal spine is often crushed. Similar to BU 15, except for the possession of only one ala by the first vertebra. (WU)
BU 17
SC G
Body of 1st sacral vertebra with all or most of one wing present. Arch intact and may or may not show evidence of crushing along crest. (MB)
BU 11
SC H
All or most of wing or ala of 1st sacral vertebrae detached from body. Either side may be represented. (TH)
BU 2
SC I
Complete body of 1st sacral vertebra body. Medial portion of ala represented.
BU 13
SC J
Anterior portion of 1st sacral vertebra body. Ala not represented. Posterior portion of body absent. (DS)
BU 3
SC K
All or major portion of left half of body of 1st sacral vertebra. Medial portion of ala represented.
BU 4
SC L
All or major portion of right half of body of 1st sacral vertebra. Medial portion of ala represented.
BU 5
SC M
Fragment of 1st sacral vertebra including one of articular processes. Frequency indicates number of pieces only.
BU 8
SC N
Essentially complete 2nd to 5th sacral vertebra including body and arch separated from the rest of sacrum. Similar to BU 16.
BU 16
SC O
Essentially complete, fused 2nd to 5th sacral vertebra bodies. Arch and spinous process absent. Similar to BU 8. (DS)
BU 12
SC P
Anywhere from 1-3 fused vertebrae (other than 1st sacral vertebrae) detached from rest of sacrum. Body and arch represented but usually damaged to some extent. (DS)
BU 6
SC Q
Left or right ½ of a body of a 2nd to a 5th sacral vertebra split medially. Frequency indicates number of pieces only.
BU 7
SC R
Irregular shaped fragment of 2nd – 5th sacral vertebrae bodies. Fragment may include portions of both sides of a single vertebral body; or portions of the bodies of 2 fused adjacent vertebra. Frequency indicates number of pieces only.
BU 9
SC S
Fragment(s) characterized primarily by portion of median crest of sacrum. Frequency indicates minimum number of elements represented. For Oldman Dam, frequency indicates number of pieces.
BU 10
SC T
Not a bone unit. Number of pieces comprising BU 9. Not coded for Oldman Dam.
BU 14
SC U
Fragment of lateral sacral crest. (DS)
BU 22
SC V
Unfused second to fifth vertebra. (SB)