ANTH Ch. 12 - Skeletal Variation and Pathology Notes

Skeletal Variation

As a result of different genetic and environmental influences, human skeletal structures exhibit considerable variation, affecting attributes such as bone density, size, and overall morphology. These are called idiosyncrasies, or individual variations in morphology and configuration.

Causes of Variation

Congenital

• Genetics (mutations)

• Environmental (epigenetic) factors

Developmental

• Degenerative

• Disease processes

• Trauma

Types of Variation

Normal variation: Presence of normal morphological differences.

• Normal skeletal variation refers to the naturally occurring differences in bone structure and form that can be observed across populations and individuals.

• Examples of normal variation include paranasal sinus configuration, cranial suture patterns, sesamoid bones, trabecular bone pattern, and external bone contour.

• These features are present in normal bone anatomy but differ between individuals.

Skeletal anomalies: Deviations from regular anatomical configuration; can be common.

• Anomalies are things that not everyone has, but they aren’t necessarily rare.

  • Ex: Having a metopic suture isn’t rare, but it is an anomaly.

• Could be cause by genetics or epigenetics

  • Ex: genetic mutations, environmental exposure during developmental stages, etc

• Bone Anomalies

  • Not everyone possesses the same bones; certain anomalies might appear more frequently in particular populations.

  • Accessory bones can occur in multiple parts of the skeleton and may include…

  • Sesamoid bones

  • Extra ribs or vertebra

  • Extrasutural bones: Accessory bones along cranial suture

    • Tend to occur most along the lambdoidal suture, where they are often called Wormian bones.

  • Supernumerary Tooth: Refers to an extra tooth that grows, sometimes in an unusual position.

    • This condition can arise from a duplication error during tooth bud development.

  • Accessory foramina: Extra holes in bone where they would typically not be found

    • Are seen in several locations including the sternum, long bones, and cranium

  • Septal aperature: Incomplete ossification of the bony septum that separates the olecranon and coronoid fossa in the distal humerus

  • Spina bifida: A defect of the developing spinal cord where the spinal column fails to close effectively over the spinal cord, leaving it unprotected.

  • Cleft neural arch: Occurs when the two sides of the neural arch of a vertebra do not fuse properly, leading to a gap that can cause potential spinal issues.

  • Metopic suture: An anatomical feature where the two halves of the frontal bone fail to fuse completely, leaving a visible suture.

Pathology

• Definition: Abnormal anatomy resulting from disease processes.

  • Includes factors like infection, injury, and other disorders leading to lesions.

• Pseudo-pathology

  • Conditions that mimic disease; for instance, skeletal features altered by taphonomic processes after death.

• Differential diagnosis

  • Distinguishing between different conditions.

Types of Lesions

• Proliferative Lesions (Osteoblastic activity): Results in increased bone density and projection of bony processes; seen in conditions like:

  • Periostitis: Inflammation of the periosteum around bones.

  • Osteomyelitis: Bone infection that can lead to pus formation.

  • Heterotopic ossification: Bone formation in non-skeletal tissues, such as ossification of costal cartilage with fusion of the first ribs to the sternum.

• Lytic Lesions (Osteolytic): Characterized by bone resorption or loss

  • Associated with infections and cancers

  • Speed of destruction affects appearance

    • Slow: Smooth appearance with normal margin density.

    • Fast: Sharp margins with less reactive bone.

  • Seen in conditions like…

    • Secondary neoplasms: cancer that has migrated

    • Tubercolosis: an infectious disease caused by bacteria

    • Brucellosis: an infectious disease caused by bacteria

• Deformative Lesions: Change the overall shape of the bone

  • May arise from…

    • Cultural practices (e.g., binding or shaping of skulls).

      • Intentional bone deformation for aesthetic or cultural reasons, such as head binding or cranial shaping.

    • Trauma (e.g., bone fractures and healing misalignments).

  • Examples include…

    • Spinal deformities like lordosis, kyphosos, or scoliosis

    • Conditions like rickets (vitamin D deficiency) or osteomalacia (vitamin D deficiency)

    • Craniosynotosis: A condition in which the cranial sutures fuses abnormally

• Mixed Lesions: Can be characterized by both bone formation and loss (prolific AND lytic)

  • An example is as porotic hyperostosis, or the porous enlargement of bone tissue.

Repetitive Activity

• Skeletal responses to repetitive stress, affecting bone shape and density.

  • Examples include noticeable changes among athletes due to their specific sports activities.

• Response to Mechanical Stress: Influences structural changes in bones and teeth.

  • Hyper-development: Enhancement of specific anatomical structures due to overuse.

  • Asymmetry: Changes observed in favoring one side (e.g.,right handedness affecting the skeletal structure).

• Impact on Teeth: Can lead to occlusal attrition and other dental variations.