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)
What is an apophyseal fracture?
Like an avulsion fracture, where a bony outcorpping is separated.
Describe the stages of fracture healing
Bleeding: devascularizes and forms hematoma (hour-glass sign on radiograph)
Resorption: osteoclasts and inflammatory cells response
Mesenchymal differentiation: differentiate into osteoblasts and fibroblast-progenitor cells
Callous formation: can be seen on radiograph sometimes
When does increased bone blood flow peak following a fracture?
~ 2 weeks, returns to normal by 3-5 months
What are the 3 primary bone circulation systems?
Nutrient-artery system: pierces diaphysis through the nutrient foramen and then traverses to the medullary canal of the bone
Metaphyseal-epiphyseal system: (i.e. geniculates) form the periarticular vascular plexus
Periosteal system: capillaries that supply the outer third of the diaphysis
What are the 4 stages of fracture repair?
Hematoma formation
Fibrocartilage callous formation
Bony callous formation
Remodeling
Early in the stages of fracture healing what are the 2 most important growth factors present and how do they reach the fracture site?
Bone Morphogenic Protein (BMPs) facilitated by primative mesenchymal and osteoprogenitor cells
Transforming Growth Factor Beta (TGFB) secreted by macrophages and platelets that infiltrate the fracture site
What are the actions of BMPs in the fracture healing process?
STIMULATE BONE FORMATION**
- Osteoinductive: induces metaplasia of mesenchymal cells into osteoblasts.
- Target the undifferentiated perivascular mesenchymal cells
What are the actions of TGFB in the fracture healing process?
Enhance bone growth/ lay the framework***
Induce mesenchymal cells and osteoblasts to produce type II collagen and proteoglycans
Surgeons coat porous implants with TGFB and it enhances bone growth in the area
What is the most important thing that the fracture hematoma provides for the healing process?
Progenitor cells and growth factor for mesenchymal differentiation.
What is the intermediate between hypertophic cartilage and bone called?
Woven bone - terminal differentiation of chondrocytes causes cartilage calcification resulting in woven bone
Picture in slides (~halfway thru intro lecture)
Why is woven bone weak?
It is a haphazard arrangement of calcified collagen. Hasn’t been remodeled
What is wolff’s law of bone remodeling?
bone remodeling in response to mechanical stress
What is the piezoelectric charge law of bone remodeling.
Theory that explains how remodeling can repair a fracture in a straight fashion:
Compression (concave) side of the bone (-) charge activates blasts Tension side (convex) side of the bone (+) charge activates clasts
How is cortical bone remodeled?
Cancellous bone?
osteoclastic tunneling (cutting cones) osteoclastic resorption followed by blasts laying down new bone
What is delayed union, non-union, atrophic non-union?
Delayed union: not healed in twice the normal healing time
Nonunion: not healed in 3x the normal healing time (6 mos.)
Atrophic non-union: bone near the fracture becomes pointed with no apparent healing of the fracture.
What is hypertrophic nonunion?
Formation of enormous amounts of bone at the fracture site with no healing. (Elephants foot)
What is a malunion?
Fracture that is united with unacceptable angulation, rotation, or shortening
What are fracture blisters and how do they form?
Skin blisters that present in the skin directly overlying a fracture.
Caused in response to increased compartmental pressure
Caused by uneven extrinsic pressure
What is a Jone’s fracture? What are complications of this fracture?
Fracture of the 5th metatarsal
Poor blood supply = High incidence of non-union
What are some signs/symptoms of a DVT/PE
Calf/Thigh Pain Edema distal to obstruction Homan's sign (pain with passive dorsiflexion) Shortness of Breath Chest Pain Tachycardia Hypotension
What is a fat embolism?
fat within the circulation which can produce embolic phenomena, with or without clinical squelae
What is fat embolism syndrome?
fat in the circulation associated with an identifiable clinical pattern of symptoms and signs
Describe the mechanical theory and biochemical theory of fat embolisms.
(Gauss) Mechanical Theory: 3 conditions needed - injury to adipose tissue, rupture of veins in the zone of injury, mechanism that will cause passage of free fat into the open ends of the vessels
(Lehman) Biochemical Theory: Plasma mediators mobilize fat from body stores, they then form large droplets, embolized fat is degraded into FFAs [TOXIC]
What are the findings (classic triad) of a fat embolism.
Neurological abnormalities (first symptom in pts with PFO), Hypoxemia, Petechial Rash
What is Gurds criteria used to diagnose?
Fat emboli syndrome
What is reflex sympathetic dystrophy?
aka Complex Regional Pain Syndrome
Type I: Tissue Injury
Type II: Nerve Injury
Caused by catecholamines released from sympathetic nerves which acquire the capacity to activate pain pathways following a nerve or tissue injury
What are the stages of CRPS?
Acute - burning, swelling, pain
Dystrophic - thin shiny skin, loss of hair, contractures
Atrophic - loss of motion, loss of subcutaneous fat, osteoporosis, pathological fractures.
What are the most common sites of AVN?
Femoral Head Carpal Navicular Talus Humeral Head Metacarpal Head Scaphoid
What is a pathologic fracture?
A fracture that happens in an area weakened by another disease process (usually happens during normal activity)
Treatment must address the underlying disease process
In what case are comparison x-rays usually used?
usually done to verify a fracture in a ped. patient
In what case are stress x-rays used?
To assess ligamentous stability of a joint
Describe high and low frequency ultrasound
Low: less resolution, greater depth of penetration
High: higher resolution, better for ortho – images of tendons and ligaments
Which type of MRI will be used to try and discover a muscle strain?
T2
What is the best radioisotope for bone scanning?
Sr85, tc99 (better-excreted in urine)
What is the best radioisotope for tagging WBCs for finding areas of infection?
Indium 111
What is Gallium 67 used for/
Impregnates into calcium hydroxyapatite crystals taken up in neutrophils and bacteria.
What are PET scans generally used for?
Metabolic imaging, especially good for soft tissue neoplasms or osseous metastasis
measures glucose utilization by tissue, can be combined with CT for more precise imaging
(based on increased glycolytic activity rate in pathologic tissues
What type of imaging is commonly used to check/confirm an osteoporosis/osteopenia dx?
DEXA scan (state of the art bone density screening), measures absorption of 2 beams of radiation into hip and spine
What T scores on a DEXA scan correlate to certain pathologies?
-1 to -2.5 = Osteopenia
<-2.5 = Osteoporosis
Normal = -1 and above
Describe the choice of modality slide?
CT Scan - cross sectional capacity
Bone Scan - early detection of fracture or infection
MRI - Bone contusions, articular cartilages, vascular structure relationships with other structures
Ultrasound - fluid filled tissue and vascular supply
Why does the elbow have a high degree of vulnerability for supracondylar fracture?
There is a central thinning on the distal humerus, produced by the olecranon fossa posteriorly and the coronoid fossa anteriorly
What is the average carrying angle of the ulnohumeral joint in children/adults?
Kids: 15
Adults: 18
How does one test for medial epicondylitis
load the flexors of the wrist/hand
How does one test for lateral epicondylitis?
Load the extensors of the wrist/hand
REVIEW ATLAS PICS OF HAND LIGS
REVIEW
What is the significance of the Helicoid Triquetro-Hamate Joint?
The way the bones overlap in fex/ext/rad dev/ ulnar dev, Help test for dislocations?
Flexion is similar to Radial Deviation
Extension is similar to Ulnar Deviation
Describe DISI (Dorsal intercalated segment instability)
lunate rotates dorsally
Lunate aka Intercalated segment tilts dorsally in radial deviation or flexion due to disruption of scapho-lunate and radio-scapho-capitate ligament disruption
Describe VISI (Volar Intercalated Segment Instability)
Lunate Rotates Volarly
Disruption of the luno-triquetrial ligament
Why is an infection of the fingertip hard to get rid of?
Compartmentalized (fibrous septae) make it hard for bloodflow of antimicrobial defenses to reach the infection
What are the etiologies for the boutonierre deformity?
Rheumatoid arthritis (central slip rupture) Trauma: triangular ligament tear, central slip extensor tear
What are the etiologies for the swan neck deformity?
Rheumatoid arthritis (PIP synovitis with dorsal displacement of lateral bands) Late result of mallet: proximal retraction of lateral bands due to loss of distal anchor
What are the common overuse injuries of the hand?
Parasthesia/Tingling/Numbness: Carpal/Cubital Tunnel Syndrome, Radial Sensory Neuritis
Pain: Flexor/Extensor tendonitis +/- triggering, CMC Thumb synovitis/arthritis
