sacrum
Enable an AI agent to identify a sacrum, record its anatomical and structural state, and determine what further assessment or handling its condition requires.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an AI agent to identify a sacrum, record its anatomical and structural state, and determine what further assessment or handling its condition requires.
The sacrum is the wedge-shaped bone at the base of the human vertebral column, normally formed by fusion of five sacral vertebrae, that articulates with the fifth lumbar vertebra, the coccyx and both hip bones.
It can be Identify and orient the sacrum in an image, anatomical preparation or skeletal specimen.; Map observations to named sacral landmarks and explicitly justified segment levels.; Measure sacral geometry using recorded landmarks and reference planes.; Compare fusion and segmentation with an appropriate developmental and species reference.; Flag observed disruption, displacement or canal involvement for qualified assessment.; Determine which additional view, comparison or specialist interpretation is needed before relying on an uncertain finding..
Distinguishing features
Identify a structure at the base of the vertebral column, between the hip bones, with a superior interface to the lumbar spine and an inferior interface to the coccyx.
In typical mature human anatomy, look for a wedge-shaped bone formed from fused sacral vertebrae; incomplete fusion requires developmental interpretation rather than automatic rejection.
Distinguish it from the coccyx by its broad superior base, lateral auricular surfaces and paired rows of pelvic and dorsal sacral foramina.
Distinguish it from an individual lumbar vertebra by its serial segmental landmarks and contribution to the posterior pelvic framework.
Distinguish it from the ilium by the midline sacral canal and paired foraminal pattern rather than a broad iliac blade.
Scope
+ Identification and boundaries of the sacrum within the vertebral column and pelvis
+ Sacral segmentation, fusion, developmental stage and anatomical variation
+ Sacral surfaces, landmarks, canal and foramina
+ Articular interfaces and attachment sites relevant to pelvic load transfer
+ Observed bone integrity, alignment and changes affecting adjacent structures
+ Evidence supporting identification, measurements and condition assessments
- The whole organism, species or population
- The complete pelvis, lumbar spine and coccyx beyond their interfaces with the sacrum
- Sacral nerve roots and pelvic organs as independently functioning structures
- Sacroiliac joint disorders as complete disease models
- Fracture syndromes, tumours and other diseases beyond their manifestations in the sacrum
- Independent treatment selection, surgical planning and rehabilitation protocols
Characteristics
- Anatomical context
- Species; individual or specimen identifier; in situ, isolated specimen or imaging representation Determines which anatomical reference applies and whether a record describes a physical structure or evidence about it.
- Developmental and fusion state
- Immature, partially fused, fused or indeterminate; identify the observed fusion sites Helps distinguish expected development from injury or unusual segmentation.
- Sacral segment attribution
- Observed segment count and numbering method; transitional anatomy present, absent or uncertain Incorrect segment attribution can mislocate findings and obscure the lumbosacral boundary.
- Sacral dimensions
- Height and width in mm, with landmarks, plane and method recorded Makes size comparisons interpretable across images and specimens.
- Curvature and orientation
- Angles in degrees or described curvature; reference plane and body position required Separates intrinsic shape from position-dependent alignment.
- Articular interfaces
- Superior lumbar, left and right sacroiliac, and inferior coccygeal interfaces; continuity and alignment observations Locates the sacrum within the structures through which it participates in pelvic support.
- Canal and foraminal configuration
- Location, dimensions where measurable, continuity and observed narrowing or disruption Records bony passage anatomy without treating it as proof of nerve function.
- Osseous integrity
- Intact, disrupted, remodelled, focally altered or indeterminate; location and evidence required Supports recognition of structural concerns while keeping observations separate from diagnoses.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 15 findings · 31 questions.
Sacral identity and boundaries Establish that the observed structure is a sacrum and define its anatomical extent.
A sacrum can be misidentified or incorrectly numbered when isolated, incompletely developed or transitional.
Anatomical recognition
Use context and landmarks to establish identity and orientation.
Sacrum identification
Record the species context and visible landmarks supporting identification as a sacrum.
- Which features establish that this is a sacrum rather than a coccyx, lumbar vertebra or part of a hip bone? definition
- Which landmarks establish superior, inferior, pelvic and dorsal orientation? boundary
- What specimen record or imaging study establishes the species and anatomical context? provenance
Segmental extent
Establish where the sacrum begins and ends without assuming segment numbering.
Lumbosacral and coccygeal boundaries
Record superior and inferior limits and uncertainty introduced by transitional anatomy.
- How were the superior sacral segment and the sacrococcygeal boundary identified? boundary
- Does the available view support reliable vertebral numbering, or is wider spinal context needed? action
- Is any apparent sacralisation or lumbarisation directly supported by the observed anatomy? provenance
Development and sacral form Represent fusion, segmentation and geometry in an appropriate developmental context.
Fusion and shape affect identification and interpretation, and variation must not automatically be labelled pathological.
Developmental assembly
Describe the observed relationship between sacral segments and their fusion sites.
Segment fusion pattern
Document which segmental boundaries remain visible and how their appearance is interpreted.
- Which sacral fusion sites are united, incompletely united or not assessable? measurement
- What age or developmental evidence supports interpreting an unfused site as expected development? provenance
- What additional evidence would distinguish an unfused developmental boundary from a fracture? action
Sacral geometry
Characterise dimensions, curvature and bilateral form using reproducible observations.
Shape and asymmetry
Record geometry of the base, alae and body while accounting for image projection and specimen completeness.
- What are the sacral height, maximum width and curvature using explicitly named landmarks? measurement
- Does apparent asymmetry persist after accounting for rotation, projection and missing bone? measurement
- Which species and developmental reference supports interpreting the observed form? provenance
Pelvic support and interfaces Describe the sacrum's connections to the lumbar spine, hip bones and coccyx.
Its role in pelvic support depends on specific interfaces and alignment that cannot be inferred from shape alone.
Articular connections
Locate and assess the bony sides of sacral articulations.
Sacral articular surfaces
Record the superior lumbar interface, paired auricular surfaces and inferior coccygeal interface.
- Which sacral articular surfaces are visible, and which neighbouring structures are represented? boundary
- Is there observed incongruity, displacement or surface alteration at a named interface? measurement
- Which findings describe sacral bone, and which require a separate joint or neighbouring-bone record? boundary
Alignment and attachments
Relate sacral position and attachment landmarks to surrounding pelvic support structures.
Support context
Record positional measurements and visible attachment sites without inferring functional stability from bone appearance alone.
- What body position and reference plane were used for any sacral slope or orientation measurement? measurement
- Which ligament or muscle attachment landmarks are involved in an observed bony change? boundary
- What additional joint, ligament or clinical evidence is needed before assessing pelvic stability? action
Passages, integrity and assessment Locate sacral passage anatomy and structural abnormalities, and define the limits of the available evidence.
Changes near the canal or foramina require precise localisation, while bony observations alone cannot establish neurological effects.
Canal, foramina and hiatus
Describe the sacral canal, paired foramina and sacral hiatus as bony anatomical features.
Sacral passage configuration
Record visible passage boundaries, variation and involvement by structural changes.
- Which portions of the canal, pelvic and dorsal foramina, and sacral hiatus are assessable? boundary
- Where is any narrowing, interruption or unusual opening, and how was it measured? measurement
- What separate evidence would be required to assess involvement of adjacent neural structures? action
Structural condition
Distinguish observed bone changes from diagnostic interpretations and establish appropriate follow-up.
Localised integrity assessment
Document disruption, remodelling or focal alteration relative to sacral segments, alae and passage anatomy.
- Where is the observed abnormality relative to the sacral alae, foramina, canal and articular surfaces? measurement
- Which imaging view, specimen observation or report supports the finding, and what remains unassessable? provenance
- Does the observation require further imaging, comparison with earlier evidence or qualified clinical assessment before a consequential action? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This description assumes human anatomy; sacral structure and vertebral number differ across vertebrate groups.
- The sacrum is an anatomical structure, not an organism or taxon, despite the batch context.
- Fusion, shape and vertebral count vary with development and anatomical variation; five fused vertebrae describes the usual adult configuration.
- Which of these check these first hold for the sense of sacrum this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- Terminologia Anatomica - Os sacrum - Latin anatomical name for the sacrum.
- Which of these identifiers and schemes hold for the sense of sacrum this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- Terminologia Anatomica, maintained by the Federative International Programme for Anatomical Terminology (FIPAT), standardizes anatomical terminology.
- Which of these standards and regulation hold for the sense of sacrum this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Transfers loads from the vertebral column to the pelvic girdle through the sacroiliac joints.
- Forms the posterior wall of the bony pelvis.
- Provides attachment sites for pelvic and spinal muscles and ligaments.
- Its canal and foramina provide passage for nerve roots and associated structures.
- Which of these real-world use hold for the sense of sacrum this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Number of constituent sacral vertebrae - Normally 5 - vertebrae
- Which of these typical measurements hold for the sense of sacrum this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Traumatic fractures can disrupt pelvic stability and injure adjacent nerves.
- Insufficiency fractures can occur in weakened bone.
- Injury affecting sacral nerve roots can impair pelvic organ function or sensation.
- Lumbosacral transitional anatomy can complicate vertebral numbering during imaging and procedures.
- Which of these failure modes and hazards hold for the sense of sacrum this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- coccyx - The coccyx lies below the sacrum and forms the terminal portion of the vertebral column.
- lumbar vertebra - A lumbar vertebra is a separate vertebra above the sacrum; the adult sacrum normally comprises fused sacral vertebrae.
- pelvis - The bony pelvis is the larger skeletal assembly that includes the sacrum, coccyx and paired hip bones.
- sacroiliac joint - A sacroiliac joint is an articulation between the sacrum and an ilium, rather than a bone.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of sacrum this model covers, and on what evidence? provenance
What the second pass must settle
- Does the registry intend this entry to cover human sacra only or homologous sacral structures across vertebrate species?
- Which developmental references should govern interpretation of segment fusion, and how should uncertainty in age be represented?
- Which vertebral enumeration convention should be required when transitional anatomy or limited imaging prevents confident sacral numbering?
- Which validated landmark and measurement conventions should be adopted for sacral dimensions, curvature and positional angles?
- Which evidence standards should govern escalation of sacral structural findings and links to neighbouring joint, neurological and disease models?