Bone Structure and Healing, Osteomyelitis, Septic Arthritis Flashcards
Formation of flat bones
Intramembranous ossification directly from mesenchyme
Mutation in flat bone formation that leads to cleidocranial dysplasia
RUNX2 / Cbfa1
Formation of short bones
Endochondral ossification (same as long bones)
Portion of bone supplied by the nutrient artery
Inner 2/3 of cortex and the medulla
Portion of bone supplied by the periosteal artery
Outer 1/3 of cortex
Portion of bone supplied by the metaphyseal artery
Metaphyseal junction (poor supply in the 5th metacarpal –> fracture)
Organization structure of cortical bone
Osteon/Haversian system
Origin tissue of osteoblasts
Mesenchyme
Products of osteoblasts
RANK
Alkaline phosphatase
TYPE 1 COLLAGEN (for bone formation)
osteocalcin (activity marker)
Origin tissue of osteoclasts
Hematopoietic cells
Products of osteoclasts
Tartrate resistant phosphatase (TARP)
MoA of osteoprotegrin
Prevents bone resorption by binding and inhibiting RANK ligand produced by osteoblasts.
Prevents activation of osteoclasts.
MoA of RANK-L
Produced by osteoblast cells to activate clasts and resorb bone
Effect of PTH on bone
High, continuous levels of PTH result in bone resorption
Pulsed levels of PTH results in bone formation
MoA of forteo
Acts as an artificial PTH, given in pulses to stimulate bone growth in osteoporosis
MoA of denosumab
Anti-RANK-L antibodiy –> reduced bone resorption
Forces that bone is weakest against
shear, then tension (strongest in compression)
Fracture pattern seen in tensile forces or pure bending
Transverse
Fracture pattern seen in compression
Oblique
Fracture pattern seen in bending with an axial load
Butterfly with two oblique fractures on the side of compression.
Fracture pattern seen with bone torsion
Spiral
Types of epiphyses
Pressure and traction
Traction epiphysis
FOrms at insertions of tendons
Does not lenghten bone but does influence shape
Pressure epiphysis
FOrmes at areas of joint articulation
Lengthens bones
THe three major zones of the epiphysis
Reverse zone
Proliferative zone
Hypertrophic zone
Function of the reverse zone
Mainly anoxic
Produces and stores cartilaginous matrix
Function of the proliferative zone
High levels of O2 and chondrocyte division
Production of ECM matrix
Function of the hypertrophic zone
Preparation and calcification of matrix from the proliferative and reverse zones
At the end of the hypertrophic zone, cells are no longer viable due to calcification and anoxia
Types of epiphyseal injury most associated with future growth abnormalities
III, IV, and V (Crush)
Type III epiphyseal fracture
fracture through the epiphysis and physis only
Type IV epiphyseal fracture
Fracture through the physis, eipphysis and underlying bone
Type V epiphyseal fracture
crush
Type II epiphyseal fracture
fracture through physis only, often due to a chip of bone
Type I epiphyseal fracture
Sliding of the epiphysis off of the physis (ex: hip dysplasia)
Difference between osteopenia, osteomalacia, and osteoporosis
Osteopenia: decreased bone density during immobility
Osteomalacia: decreased bone QUALITY due to poor mineralization
Osteoporosis: decreased bone density (but bone of normal quality)
Risk factors for developing osteoporosis
smoking (estrogens are protective?)
Most common agents of osteomyelitis in adults
Staph and GNR
Most common agents of osteomyelitis in children
Strep and staph
Joints most commonly affected by osteomyelitis in children
growth plates
Joints most commonly affected by osteomyelitis in adults
Spine, SI, sternoclavicular joints
Most common agents of osteomyelitis in prosthetics
S. epidermidis
Most common agents of osteomyelitis in bites or fist injuries related to the mouth
Streptococcus or anaerobes
Most common agents of osteomyelitis in pressure or diabetic ulcers
Strep or anaerobes
Most common agents of osteomyelitis in SCD
Salmonella
Most common agents of osteomyelitis in trauma or diabetic lesions
Anaerobes
Most common sources of Pseudomonas osteomyelitis
Tennis shoe
Otitis (malignant)
IV drug abuse
Limitations of sinus tract culture in osteomyelitis
Only finds aerobes
Not necessarily correlated to organism causing osteomyelitis
Treatment of CCO
Surgery is the only curative option
In patients who should not get surgery, suppression with antibiotics can be done
Treatment of acute osteomyelitis
Can be cured with antibiotics
Empiric therapy of osteomyelitis
NOT GIVEN, must get biopsy first
Septic arthritis therapy for patients without risk factors
Nafcillin
Septic arthritis therapy for patients with risk factors
Nafcillin + (FQ or aminoglycoside)
OR
2nd generation cephalosporin (cefuroxime, cefoxitin)
Should also cover anaerobes
Differences in reactive gonococcal arthritis and septic
REACTIVE: Multiple joints, rash, involves wrists/hands
(can’t pee, can’t see, can’t climb a tree)
SEPTIC: Single joint, knee/hip, no rash (may have lesion on joint)
Most common joints for SA in adults and children
Adults: Knee
Children: Hip
