1 - Orthopedics/Anatomy Flashcards
What is the difference between endochondral and intramembranous ossification?
Endochondral - bone REPLACES cartilaginous model (e.g. long bones, physis, fracture callus)
Intramembranous - mesenchymal cells differentiate into osteoblasts which form the bone (e.g. flat bones like skull)
What is appositional bone growth?
osteoblasts deposit new bone on existing bone (e.g. periosteal bone enlargement) —> increased thickness
During endochondral ossification what is responsible for 1. resorption of calcified cartilage an 2 formation of new bone?
- osteoclasts resorb cartilage
2. osteoblasts form the bone
What do osteoblasts produce as a byproduct during proliferation (growth of new tissue)
They produce Alkaline Phosphatase
Note - they even produce it in bone tumor formation (serum alk phos is a good way to diagnose this)
What are osteocytes?
Osteocytes are osteoblasts that have become surrounded by a newly formed bone matrix
They communicate through canaliculi (holes) and control the levels of calcium and phosphorus in the ECM
What hormones stimulate/inhibit osteoclast activities?
Stimulated by: calcitonin
Inhibited by: parathyroid hormone
Drugs that help bone reform following fractures are _____ (hormone) based because it activates the activity of osteocytes.
Calcitonin
What is Howship’s lacuna?
aka - resorption bays - A region of bone formed by osteoclasts which can resorb bone surface to make way for new growth/repair/maintainence
What are the 4 major regions of the physis in bone?
Resting zone
Proliferative zones
Hypertrophic Zones
Vascular invasion/zone of calcification
Describe the physeal resting zone?
Area of reserve, consists of scattered chondrocytes, stores lipids/glycogen/proteoglycan for later growth/matrix formation
Describe the physeal zones of proliferation
Chondrocytes start to stack into lines in direction of growth, start to proliferate/divide
TOP CELL IS MOTHER (dividing)
Describe the physeal zone of hypertrophy
Chondrocytes that have proliferated/divided start to enlarge 5-10x
Enlargement responsible for 44-59% of long bone growth
Differential growth can be attributed to differential cell sizes here
Describe the physeal zone of calcification
It is near the zone of vascularization invasion
Where the chondrocytes begin to die
Matrix begins to calcify, which is followed by osteo proginator cell invasion and replacement
What type of collagen is formed in the physeal matrix?
TYPE II
What hormone is involved with the termination of chondrocyte activity during physeal closure?
Estrogen
In the event of a physeal fracture, where do fractures most commonly occur?
In the HYPERTROPHIC ZONE
Describe the process of intramembranous ossification
- Mesenchymal cells cluster together and start secreting organic components of bone matrix which then becomes mineralized through the crystallization of calcium salts
- As calcification occurs the mesenchymal cells differentiate into osteobalsts
What is the location where ossification begins begins called?
ossification center
What are the names of the fractures that result in direct force? (3)
Tapping
Crush
Low/High Velocity Penetrating
What are the types of fractures that can result from indirect forces? (6)
Traction Angulation Rotational Vertical compression Axial Loading/Angulation Angulation with Torsion and Axial Loading
If a fracture happens near the end of a bone adjacent to joint called?
Epiphyseal Fracture
If a fracture displays flaring at the end of a shaft of bone what is it called?
Metaphyseal (region of bone between diaphysis and epiphysis, where it begins to taper out wider)
A fracture that occurs in the shaft of a long bone is called?
Diaphyseal Fracture
Describe the possible orientations of fractures?
Transvers: perpendicular to long axis Oblique: angulated fracture line Spiral: multi-planar Comminuted: more than two fragments Segmental: separate segments Intra-articular: enters into a joint
How is the displacement of a fracture named?
It is named by the movement of the distal portion of the fracture
What is a bayonet displacement?
longitudinal overlap of fragments
What is the definition of a fracture that communicates through a hole in the skin?
Contaminated - always refer to ortho for contaminated fractures with a hole >1cm
What is the Gustillo-Anderson Classification?
A system of classifying soft tissue injury in open fractures
What are the three types of gustillo-anderson classifications
All greater than 10cm wound size/ high energy impact fractures
Type III-A: Extensive tissue laceration, adequate bone coverage after debridement. Free flaps not necessary to cover bone. Segmental fractures (Gunshot Injuries). HIGH Degree of Contamination
Type III-B: Extensive soft tissue injury with periosteal stripping and exposed bone after debridement. Requires local or free flap to cover bone. MASSIVE Contamination.
Type III-C: Same as B, Includes Vascular injury requiring repair for limb salvage. MASSIVE Contamination.
Describe a plastic deformation fracture
A bend in pediatric bone
Describe a buckle fracture
aka Torus fracture
Pediatric fracture where only one cortex is involved
Describe a greenstick fracture
Crack on one cortex and buckle of the opposite side
Where are triplane and tillaux fractures and what is the underlying cause of this fracture?
They occur as a result of assymetrical closure of the distal tibial growth plate. REFER TO PICTURES (SL60&61)
Both are intra-articular and require anatomic reduction
Describe the salter-harris fracture classifications?
SH-I: widening of the epiphyseal plate
SH-II: through physeal plate and metaphysis
SH-III: through physeal plate and epiphysis
SHIV: through both metaphysis and epiphysis
SHV: Crushed physeal plate (physis)