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A 12 year old boy has a broken elbow and a fractured humerus bone that is…
A 12 year old boy has a broken elbow and a fractured humerus bone that is penetrating the skin.
Upstream Cause:
Direct
- trauma from when boy fell forward on his arm with his body weight.
Indirect
- lactose intolerance and poor diet made his bones weak.
PHYSIOLOGY
Stages of Bone Healing
Bone repair begins with
Reduction
- realignment of the broken bones
Hetmatoma Forms
- blood vessels are torn, causing blood clots to form
Can cause pain and inflammation
Fibrocartilaginous Callus Forms-
broken ends connect due to fibroblasts producing collagen fibers
Bony Callus Forms
- osteoblasts begin forming spongy bone, which will gradually replace the fibrocartilaginous callus with immature bone, called bony callus
Bone Remodeling Occurs
- Osteoclasts will start to shave away bony callus as osteoblasts lay down new bone matrix
Epiphyseal Plate
Location:
can be found in the Epiphysis of long bone
Becomes epiphyseal line in adults
Role
: it id a disc of hyaline cartilage that grows durning childhood to lengthen the bone
ANATOMY
Classification of Bone Fractures
Completeness of the Break
Complete:
The bone is broken through the fracture
Incomplete
: The bone is not broken through
Penetration of the skin
Open:
The fracture penetrates through the skin
Closed:
The fracture doesn't go through the skin
Position of the Bone
Displaced
: bones are out of normal alignment
Non-displaced
: bone retains its original position
Long Bone Anatomy
Cells
Osteoblasts
: bone-forming cells that secrete bone matrix; secretion includes collagen and calcium-binding proteins that make up initial un-mineralized bone
Osteocytes
: mature bone cells that occupy lacunae; monitor and maintain bone matrix
Osteogenic Cells
: meiotically active stem cells found in membranes; can turn into osteoblasts
Osteoclasts:
multinucleate cells located at sites of bone resorption
Structure
Diaphysis
: Shaft, forms long axis of the bone; surrounds the central medullary cavity
Epiphysis:
bone ends, outer layer of compact bone, inner layer of spongy bone
Includes epiphyseal line/plate
Compact Bone:
dense outer layer, looks smooth and solid
Osteons
: elongated cylinder oriented parallel to long axis of bone, group of lamella on top of each other
Canals & Canaliculi:
-Central Canal:
contains small blood vessels and nerve fibers
-Perforating Canals
: lie at right angles and connect blood and nerves of medullary cavity to central canals lined with endosteum
-Canaliculi:
radiate from lacunae, connecting therm to each other and to central canal
Spongy Bone:
a honeycomb of small needle-like pieces called trabeculae
-Open spaces between trabeculae are filled with red or yellow bone marrow
Trabeculae align precisely along lines to stress to help the bone resists stress
Membrane:
Periosteum- covers the external surface of entire bone except joints
-outer fibrous layer is dense irregular connective tissue
-inner osteogenic layer on bone surface contains osteoprogenitor cells, osteoblasts, and osteoclasts
Formation of Bones
Endochondral Ossification
: Bone develops by replacing hyaline cartilage
A bone collar forms around the diaphysis of the hyaline cartilage model
Cartilage calcifies in the center of the diaphysis and then develops cavities.
The Periosteal bud invades the internal cavities and spongy bone forms
The diaphysis elongates and the medullary cavity forms
The epiphysis ossify
Growth in Long Bones
Proliferation zone: cell at the top stack next to the resting zone, divide quickly and push away from diaphysis
2.Hypertrophic Zone: older chondrocytes, which are closer to the diaphysis, enlarge, leaving large interconnecting spaces
3.Calcification zone: surrounding cartilage calcifies and matrix begins to deteriorate, allowing blood vessels to invade
Ossification zone: calcified spicules are invaded by marrow elements, osteoclasts erode then osteoblasts cover them with new bone
Downstream Cause
: The boy has a complete open fracture that seems to also be displaced due to the his broken elbow
Because of his age, his bones theoretically should heal in 4-6 weeks. But since he has a bad diet, it will hinder his ability to make new bone.