General Flashcards
most likely organisms to grown in CHRONIC (> 4wks) prosthetic joint infections?
- coagulase negative Staph
- Proprionibacterium acnes
most likely organism to grown in ACUTE (
- Staph aureus
- beta hemolytic Strep
joint aspiration results in a periprosthetic knee joint infection?
- WBC > 1,000
- >64% neutrophils
T or F: a pt w/ BMI > 40 has a significantly increased risk of reinfection after a stage 2 revision has been completed?
True
Avg blood loss for closed femur fx?
1250mL
avg blood loss for closed tibia fx?
750mL
In the presence of exsanguinating external hemorrhage, control of hemorrhage should take precedence over the ABCDE primary survey
.
management of a tarsal navicular stress fx
NWB w/ cast immobilization as initial tx
most common complication following locked plate and screw fixation of proximal humerus fx?
screw penetration of the articular surface (subsequently falls into varus deformity)
management of irreparable rotator cuff tear (fatty infiltration) and glenohumeral arthritis?
conservative management (NSAIDs, corticosteroid injection, PT, and activity modification) -shoulder hemiarthroplasty and reverse total shoulder arthroplasty may be considered for pts who have failed a trial of non-op management
Tx of LC-1 type pelvic injury
WBAT
Nonossifying fibroma
- most commonly found in metaphysis of long bones, 80% in LE
- common locations include the knee (distal femur and proximal tibia) and distal tibia
- fibroblastic spindle cells in whirled or storiform pattern; fibroblastic connective tissue background; numerous lipophages and giant cells; hemosiderin pigmentation
role of vertebroplasty in tx of vertebral compression fracture
No role; conservative management; progress to kyphoplasty if persistent pain
management of post-axial polydactyly of the feet
no further work up necessary
most abundant non-collagenous protein in bone?
osteocalcin
osteocalcin
- most abundant non-collagenous protein in bone
- secreted by osteoBLASTS
- plays role in bone mineralization and calcium homeostasis
- biochemical marker for bone formation
- part of the ORGANIC matrix of bone
bone matrix
- 40% organic
- 60% inorganic
what is the organic matrix of bone made up of?
- collagen (90%, mostly type 1, TENSILE strength)
- proteoglycans (inhibit mineralization, COMPRESSIVE strength)
- matrix proteins (osteocalcin, osteonectin, osteopontin)
- cytokines and growth factors (IL-1, IL-6, IGF, TGF-b, BMP)
what makes up the inorganic components of bone?
- calcium hydroxyapatitie
- osteocalcium phosphate (brushite)
major source of nutrition to the growth plate
Perichondral artery of La Croix
cortical capillaries drain where?
emissary venous plexus
high pressure system that branches from major systemic arteries and supplies the inner 2/3 or mature bone?
Nutrient arteries
Blood supply to long bones
- nutrient artery system (high pressure)
- epiphyseal-metaphyseal system
- periosteal system (low pressure)
during early fracture healing, blood flow is which way?
centripetal (outside to inside; because high pressure nutrient artery system is often disrupted)
which artery system provides blood to the outer 1/3 of diaphyseal long bones?
periosteal arterioles
main difference between lamellar and woven bone
woven bone is disorganized and NOT oriented by stress patterns. lamellar bone is organized by stress patterns
tx for muscle injuries, including partial lacerations
-affected extremity should be immobilized no more than 3-5 days, followed by a progressive strengthening and stretching program
what is the proper placement of ACL reconstruction femoral tunnel?
- 10:30 in a R knee, 1:30 in a L knee
- these positions attempt to reconstruct both the anteromedial bundle, which provides AP stability, and the posterolateral bundle, which provides rotational stability
- improper femoral graft placement is one of the most common reasons for ACL revision surgery
positive ER dial test at 30 degrees indicates what?
Posterolateral corner injury
“burner” or “stinger”
- transient unilateral neurapraxia
- most commonly involves the biceps, deltoid, and rotator cuff muscles
- return to play requires normal strength and sensation in both upper extremities as well as a normal cervical spine exam (including ROM, compression, Spurling’s Adson’s, and resistive head pressures)
differential diagnosis of lower leg pain from exercise
- chronic exertional compartment syndrome
- medial tibia stress syndrome
- fibular and tibial stress fractures
- fascial defects
- nerve entrapment syndrome
- vascular claudication (atherosclerotic or popliteal artery entrapment syndrome)
- lumbar disc herniation
popliteal artery entrapment syndrome
- presents w/ intermittent claudication and decreased pulses
- compression of popliteal artery by the medial head of gastrocnemius
- passive dorsiflexion and plantarflexion provokes symptoms
- arteriogram demonstrates compression
- sx often relieved w/ exercising for a few minutes
functions of the ACL
Primary restraint to anterior translation of the tibia relative to the femur.
Secondary restraint to tibial rotation and varus/valgus rotation.
typical findings in ACL deficient knees
anterior shift and internal rotation of the tibia at low flexion angles.
medial translation of the tibia between 15-90 deg of flexion.
MCL deficiency
increased valgus rotation and slightly increased internal rotation
PLC deficiency
increased external rotation of tibia
is weight training and plyometrics safe for adolescents?
yes, it can generate gains in strenght secondary to improved neuromuscular activation and coordination, rather than hypertrophy
when is open hamstring tendon repair recommended in athletes?
- when all of the hamstring tendons have avulsed off their origin or 2 tendons have avulsed and retracted more than 2 cm
- remember to test the peroneal branch of the sciatic nerve function, as injury to this branch will cause weakness of the short head of the biceps femoris and may slow potential post-op rehab
tx of single tendon hamstring rupture/avulsion?
- non op tx
- rest, ice, weight bearing as tolerated, NSAIDs, gentle stretching, therapeutic exercise, and gradual return to athletic activity over approx. 4-6 wks
name the 3 hamstring muscles
- biceps femoris
- semimembranosis
- semitendinosis
radiographic findings of a lateral (typical) discoid meniscus
-widening of the lateral joint space, squaring of the lateral condyle, cupping of lateral tibial plateau and hypoplasia of the lateral tibial spine
discoid meniscus
- occur in 3-5% of population
- usually lateral, and may be bilateral in 25-50%
- sagittal MRI showing meniscal continuity in three 5mm sagittal images (“bow-tie sign”) is diagnostic
- if pain, mechanical sx, meniscal tear or detachment, arthroscopic debridement and saucerization is indicated
- no difference in saucerization w/ or w/o stabilization
MR findings w/ chondromalacia patellae
-high cartilage signal on T2 or proton density weighted MR images
findings consistent w/ bucket handle tear (usually medial) of meniscus
- double anterior horn sign
- double PCL sign (second smaller PCL lying anteroinferior to the native PCL)
- flipped meniscus sign and disproportional posterior horn sign
cystic lesion within the meniscus demonstrating high signal intensity on T2 weighted imaging
meniscal cyst
what is the most common long-term complication after meniscal transplantation?
meniscal graft tear
-graft failure that results from graft tears is thought to be related to the acellularity of graft tissue
what is the return-to-play progression protocol for sports concussion?
- no activity (complete physical and cognitive rest)
- light aerobic activity (walking, swimming, stationary cycling at 70% max HR; no resistive exercises)
- sports-specific exercises (specific sports-related drills but no head impact)
- noncontact training drills (more complex drills, may start light resistance training)
- full contact practice (after medical clearance, participate in normal training)
- return to play (normal game play)
Athletes must be symptom-free through each step, which is usually monitored for at least 24hrs
most common cause of early failure following ACL reconstruction?
malpositioned tunnel
what is the ideal tunnel placement for ACL reconstruction?
femoral side: approx 2 o’clock (for a L knee) or 10 o’clock (for R knee) position on the lateral wall, which facilitates a more horizontal, anatomic graft
tibial side: trajectory in the coronal plane should be about 60-75 deg from the horizontal and the tunnel entrance should be approx. 10-11mm from the anterior border of the PCL
ways to treat articular cartilage defects
- debridement
- fixation of unstable osteochondral fragments
- marrow stimulation techniques (microfracture, abrasion chondroplasty)
- cartilage replacement techniques (osteochondral autograft and allograft)
- cellular techniques (autologous chondrocyte implantation)
mechanism of carb loading?
maximizes stored MUSCLE glycogen for endurance after 90 min of exercises
typical carb depletion/loading regimen?
a hard workout followed by 3 days of a low carb diet, another hard workout, and another 3 days of a high carb diet
which class of meds has been shown to improve skeletal muscle regeneration and decrease fibrosis following muscle injury in an animal model?
angiotensin II receptor blockade (e.g. losartan)
after successful ACL reconstruction, which of the following factors has shown to contribute the greatest influence on a player’s decision to return to sport?
lifestyle and psychological factors
- return to preinjury level of sport is frequently expected within 1 yr after ACL reconstruction
- factors associated w/ not returning to preinjury level sport: previous ACL reconstruction to either knee, poorer hop-test symmetry and subjective knee function
- fear of reinjury is considered one of the most common reasons cited for a post-op reduction in or cessation of sports participation
when should an athlete return to play if they have infectious mononucleosis?
3 wks AFTER symptom resolution
- LIGHT activity after 3 wks from symptom onset when afebrile, has a good energy level, and does not have any significant associated abnormalities
- CONTACT sports after at least 3 wks when athlete has no remaining symptoms, is afebrile, and has a normal energy level
absolute contraindications to meniscal transplantation?
- inflammatory arthritis
- diffuse arthritis
- outerbridge grade IV changes
- untreated tibiofemoral subluxation
- synovial disease
- previous joint infection
- skeletal immaturity
- marked obesity
indications for meniscal transplantation
- after non-op measures have failed (unloading braces, weight loss, activity modification, analgesia)
- young pts (
discoid meniscus
- imaging shows squaring of affected condyle (lateral > medial), w/ cupping of tibial plateau
- abnormal development of a hypertrophic and discoid shaped meniscus
- 3-5% of population
- considered the most common cause of a symptomatic clicking or clunking in a childs knee
- lateral meniscus most commonly involved, and will occur b/l in 25% of affected people
- the WATANABE classification describes 3 types: type 1 = incomplete, type 2 = complete, type 3 = Wrisberg (lack of posterior meniscotibial attachment to tibia)
- majority of discoid tears occur in the posterior or middle aspect of the discoid meniscus
- partial meniscectomy yielded better radiologic results than subtotal/total meniscectomy for torn discoid menisci in pediatric population
diagnosis of discoid meniscus
3 or more 5mm sagittal images on MRI (bow-tie sign)
which meniscus is bigger?
Medial (medial has more)
Watanabe classification
discoid meniscus
- incomplete
- complete
- Wrisberg (missing posterior coronary ligament)
- Ring shaped
internal snapping hip (coxa saltans)
- caused by psoas tendon sliding over femoral head, iliopectineal ridge, lesser trochanter exostoses, or iliopsoas bursa
- hip pain and popping w/ activity
- PE findings of moving from hip flexion-abduction-external rotation to neutral triggers a popping sensation
snapping hip syndrome
- 3 forms: 1, external snapping hip, which is caused by the IT band sliding over the greater trochanter; 2, internal snapping hip; 3, intraarticular snapping hip, which is caused by loose bodies or labral tears
- tx: if painful, activity modification, PT, steroid injections; surgical tx (ITB z-plasty or psoas tenotomy) is indicated if non-op management is unsuccessful
PE findings w/ pincer-type femoroacetabular impingement
- pain w/ internal and external rotation of hip w/ hip and knee in extended position
- internal rotation only to neutral w/ hip flexed to 90 deg, but full external rotation
PE findings of cam-type femoroacetabular impingement
-decreased internal rotation and a positive impingement test (forced flexion, adduction, and internal rotation)
signs of athletic pubalgia
pain w/ half sit-up and tenderness at the pubic ramus
what is associated with a mal-positioned vertical femoral tunnel in ACL reconstruction?
-persistently positive pivot shift and lower Lysholm satisfaction scores
bundles of the ACL
- 2 bundles: anteromedial and posterolateral
- AM is longer and tight in FLEXION (you flex in the AM)
- PL is shorter and LOOSE in flexion
- AM bundle is attached anterior to the PL bundle on the TIBIA
- on the femur, the AM bundle begins at the proximal-anterior aspect of the femoral insertion site, while the PL bundle begins at the posterior-inferior part
- in extension, the AM bundle is LOOSE and the PL bundle is TIGHT
best reason to use an autograft (rather than an allograft) for ACL reconstruction in a young athlete?
lower graft rupture rate
what is the primary function of the posterior oblique ligament in the knee?
resist internal tibial rotation w/ the knee in full extension
function of superficial MCL
resists valgus and external rotation forces
role of osteoprotegerin (OPG)?
binds to and sequesters RANK-L
-causes decreased production of osteoclasts by inhibiting the differentiation of osteoclast precursors
molecules shown to inhibit osteoclasts
- OPG (binds RANK-L)
- calcitonin (binds osteoclasts)
- estrogen (decreases production of RANK-L)
- TGF-b (increases OPG)
- IL-10 (suppresses osteoclasts)
calcitonin mechanism
decreases osteoclast activity by directly binding to receptor on osteoclast
-decreases osteoclast number and activity, as well as decreases serum calcium
molecules known to activate osteoclasts
- RANK-L (binds to RANK)
- PTH (binds to osteoblasts to stimulate production of RANK-L and M-CSF, activates adenylyl cyclase)
- IL-1 (stimulates osteoclast differentiation)
- 1,25-dihydroxy vitamin D (stimulates RANK-L)
- PGE-2 (activates adenylyl cyclase)
- IL-6 (myeloma)
- MIP-1A (myeloma)
influence of PTH and 1,25-dyihydroxyvitamin D on osteoblasts?
-cause secretion of RANK-L
do bisphosphonates act on osteoblasts or osteoclasts?
-osteoclasts
PTH receptor activation primarily acts through which pathway?
-adenylyl cyclase/G-alpha stimulatory protein/cAMP/ protein kinase A in OSTEOCYTES
the binding of RANK-L to RANK on causes what?
- RANK-L binds to RANK on osteoclast precursor cells, causing differentiation into mature osteoclasts (multinucleated giant cells)
- mature osteoclasts then bind to bone surfaces via integrins and resorb bone in Howship’s lacunae
role of sclerostin?
-glycoprotein secreted primarily by osteocytes that act as negative regulator of bone mass through inhibition of bone formation by osteoblasts
what do osteoclasts secrete?
fibroblast growth factor-23 (FGF-23), BMPs and sclerostin to regulate osteoblast activity
who do bisphosphonates work?
both classes function to induce OSTEOCLAST apoptosis
Denosumab
monoclonal antibody to RANK-L, which binds to and prevents it from stimulating RANK
PTH mechanism
stimulates osteoblast to secrete RANK-L, when then goes on to stimulate the osteoclast precursor to become active
Calcitonin
- hormone secreted by the parafollicular cells of the thyroid gland to slow bone resorption, reduce calcium resorption in the tubules of the kidney, and reduce serum calcium
- opposes the effects of PTH
- secretion is upregulated by hypercalcemia, gastrin, and pentagastrin
peak bone mass attainment in both men and women is most dependent on which sex-steroid?
-estrogen
risk factors for osteoporosis?
- increasing age
- female sex
- early menopause
- fair-skinned
- family hx of hip fx
- low body weight
- smoking
- glucocorticoid use
- excessive alcohol
- low protein intake
- anticonvulsant or antidepressant use
what disease process occurs due to over-secretion of a hormone that preferentially affects the proliferative zone of the growth plate?
gigantism (over secretion of growth hormone)
how does longitudinal bone growth occur?
at the growth plate by endochondral ossification in which cartilage is first formed and then remodeled into bone tissue
layers of the growth plate?
- the resting zone
- the proliferative zone
- the hypertrophic zone
disproportionate dwarfism, spinal involvement, and a barrel chest from a COL2A1 mutation
Spondyloepiphyseal dysplasia (SED)
“hitch-hikers” thumb, cauliflower ear, cleft palate, and short-limbed dwarfism
Diastrophic dysplasia
-due to a sulfate transport mutation
defect in core-binding factor alpha 1 (CBFA-1) causing dwarfism and absent clavicles
cleidocranial dysplasia
disproportionate dwarfism w/ multiple epiphyses involved, shortened metacarpals, valgus knees, but no spinal involvement
- Multiple epiphyseal dysplasia (MED)
- due to a COMP mutation
during what age do most people achieve their peak bone mass?
16-25 yrs
what portion of the biceps tendon distal insertion is typically injured in partial biceps tears?
The Radial side of the footprint of the insertion
main flexor of the arm?
Brachialis
main supinator of the arm
biceps brachii
what nerve is injured most commonly during the superficial dissection when repairing a distal biceps rupture through a single incision anterior approach?
Lateral antebrachial cutaneous nerve
bone resection in TKA?
6 deg valgus distal femoral cut, neutral tibial cut
TKA: what should you do if tight in both flexion and extension?
symmetrical gap
-cut more proximal tibia
TKA: what to do if extension gap is good, but you’re loose in flexion?
asymmetric gap, too much posterior femur was cut
- upsize femoral component
- fill posterior gap w/ cement or metal augment
TKA: what do you do if extension gap is tight and flexion gap is good?
asymmetric gap, either not enough of posterior capsule was released or not enough distal femur was cut
- release posterior capsule
- cut more distal femur in 1-2mm increments
TKA: what do you do if extension gap is good, but flexion gap is tight?
asymmetric gap, tibial bone cut has no posterior slope and either not enough posterior bone was cut or if a PCL retained implant is used, PCL is too tight and scarred down
- size of femoral component should be downsized
- PCL should be recessed
- posterior slope of tibia should be reassessed and recut if slope is anterior
TKA: what do you do if extension gap is loose and flexion gap is good?
asymmetric gap, either too much of distal femur was cut or A-P size of implant is too big
- distal femoral augmentation should be performed
- smaller size (A-P) femoral component should be used
- thicker tibial poly insert
what is the normal anatomic axis of the lower limb?
6 degrees of valgus from the mechanical axis of the lower limb, and 9 degrees of valgus from the true vertical axis of the body
what is the anatomical axis of the tibia?
3 degrees of varus from the true vertical axis of the body
how is the proximal tibial cut made?
perpendicular to the MECHANICAL axis of the tibia (anatomic axis is 3 deg of varus)
how should the femoral component be placed in TKA?
- 3 deg of ER relative to the posterior condylar axis(to compensate for neutral tibial cut, which is normally in 3 deg varus), place lateral instead of medial if you have to choose for patellar tracking purposes
- or neutral to epicondylar axis
- or perpendicular to AP axis
where should the patellar component be placed in TKA?
Medial and superior for best tracking (think of a patella w/ MS)
when can you NOT use the posterior condylar axis to determine axial rotation of femoral component?
- when you have a hypoplastic lateral femoral condyle or significant posterior condylar wear
- Instead you can place parallel to epicondylar axis or perpendicular to AP axis
two techniques to align the tibial component rotationally?
- place center of tibial tray over the junction of medial third of the tibial tubercle w/ lateral 2/3 of tibial tubercle
- place trial components and range the knee, allowing tibial to align w/ flexion axis of the femur
Q angle
-angle between the line extended from anatomical axis of femur, and the line between the center of the patella and tibial tubercle
3 primary factors affecting patellofemoral tracking in TKAs?
- femoral component rotation
- maintenance of joint height
- reproduction of pre-op patellar thickness
Remember that the normal tibia internally rotates (femur ER) during flexion w/ greater posterior translation of the lateral femoral contact point on the tibia relative to the medial femoral contact point. The net effect of this internal rotation during flexion is to center the tibial tubercle in flexion or diminish the Q angle
.
is there a difference between anterior approach to hip vs lateral or posterior?
- anterior: greater blood loss and operative times during the learning curve period (60-100); higher risk of femoral component failure d/t difficult exposure of femur
- posterior: lower risk of needing early revision compared to anterior or lateral; higher risk of acetabular component loosening compared to lateral or anterior; greater risk of instability
DNA
double stranded deoxyribose
exon
-portion of a gene that codes for mRNA