Recon (355-423) & Review Flashcards
Acetabular dysplasia classical definitions: CE angle, Anterior CE angle and Acetabular Index
CE Angle 5 degrees
Acetabular dysplasia classically lacks what coverage?
Anterolateral
Acetabular retroversion - two signs?
Crossover, ischial spine
Acetabular overcoverage for dysplasia?
Excess anterolateral coverage, downsloping aceetabular index >5 degrees downward
Proximal femoral dysplasia - two types?
- Head-neck dysplasia - alpha angle 40 degrees or less 2. Altered neck version - excess ante or retroversion
FAI - where is the abnormal impingement occuring?
Anterosuperior zone of acetabulum
FAI can be caused by pincer and cam. Whats the difference?
Pincer - anatomic aberration between retroverted socket and normal femoral neck creates a mechanical block, pinches acetabular labrum Cam - Raised proximal femoral neck, slips under labrum and impinges articular surface, chondral acetabulum gets damaged
Surgical Treatment of FAI?
- PAO
- Anterior hip decomopression
- Proximal hip osteotomy
PAO?
Corrects tilt and version
Allows for medialization
Correct AI to 0
Head coverage to lateral CE <20
No crossover sign
Advantages:
No abductor, no posterior colum, early WB, low complication rate
Anterior hip decompression as treatment for FAI?
Will not correct shallow socket
Femoral neck, acetabular osteoplasty
Repair soft tissue tears, labrum, chondral flap
Trochanteric slide (vastus and medis attached)
Anterior dislocation
Z capsulotomy
When do you use a proximal hip osteotomy for FAI?
Correction of proximal femoral retroversion or excessive anteversion
Significant coxa valga with decreased lateral offset
4 Non-op hip arthritis treatment
- Activity modification
- NSAID
- Joint injetions
- Assist device (can in OPPOSITE hand)
Hip arthroscopy, 3 most common nerve injuries?
- Pudendal
- LFCN
- Femoral
Hip fusion salient points?
Young male, unilateral
You get adjacent joint OA
Position, 20 flex, neutral add/ab, 0-10 ER
Indication for fusion take down? Ipsilateral knee pain, back pain, contralateral hip pain
Do the abductors work? EMG, If not constrained THA
If no abductors your get a lurch gait
4 indication for THA for hip fracture
- High activity level
- Age greater than 70
- Supcapital or high neck fracture
- No risk factors for dislocation
Osteonecrosis of hip. What vessels are affected?
May be result of hypercoagulable state in idiopathic cases.
Juxtaarticular sinusoids
What percentage of hip osteonecrosis cases are bilateral?
50% so image both hips
What staging system do we use for osteonecrosis of the hip?
Ficat.
0-4 MRI and Bone scan positive only
0-1 Xray neg, 2 positive no crescent, 3 crescent, 4- collapse, DJD
Asymptomatic in only stage 0
Treatment for osteonecrosis of hip?
- Non-op - Bisphosphonates
- Surgical - start before crescent
Prognostic features?
Head collapse, young age, irreversible etiology, extent of head involvement (volume)
Head involvement % on ap x % on lateral
Therefore:
- Young with crescent - THA
- Young no crescent - Core decompression, vascularized fibular strut, curretage and bone grafting
What coating allows for bone ingrowth? Ongrowth?
Porous - Ingrowth
Grit - Ongrowth
Successful cemeting technique requires 5 steps
- Porosity reduction - vaccum
- Pressurization
- Pulsatile lavage
- Stem centralization - avoid mantle defect
- Stiff stem
Biologic fication of bone ingrowth require pore size (um) and porosity of %? Can you think of other factors?
Between 50 and 150 um
Porosity of 40-50%
Pore depth
Minimize distance between prosthesis and bone <50um
Minimal micromotion
Cortical contact
Viable bone
Two techniques of rigid fixation of cementless implants.
What are they, where do fractures occur?
Line to line, press fit
Line to line relies on extensive porous coating and frictional “scratch fit”
Line to line - distal
Press fit - proximal
What is the role of hydroxyapetite?
Osteoblasts adhere to HA and grow toward bone shortening time to biologic fixation
Femoral stress shielding is explained by stem stiffness and Hoek’s law. Why?
Hoek’s law two springs one stiff one soft, stiff takes more so if THA is way stiffer than bone, proximal bone doesn’t take any weight and you get stress shielding
What is the safe zone for screws? What are the dangers in each quadrant?
Posterior Superior - Safe zone
Anterior superior - zone of death, external iliac a and v
Posterior Inferior - Sciatic, Internal pudendal and gluteal
Anterior inferior - Obturator
Segmental and cavitary defects of femur in revision THA what is the rule for how much further the new stem should go?
Two cortical diameters
Concerning osteolysis in THA what are the types of bearing wear?
Adehesive, Abrasive, Third body particles
Where is the most osteolysis seen in proximal femoral coated stems?
Distal to tip, around smooth area fluid will move in path of least resistance
What is the basic science with respect to PE wear causing osteolysis?
PE particles are phagocytosed by macrophages which in turn release cytokines (TNF A, TGF B IL 1,6 and PDGF)
PDGF causes the osteoblast to express RANK which binds to RANK L on the osteoclast activating it
What modulates this Osteoprotegrin which binds RANK and stops it from binding RANK L on osteoclast
Fun fact so do bisphosphonates which straight up inhibit osteoclast activity
What is the vancouver classification of periprosthetic fracture?
All about location
A - around GT
B - Around Stem or just distal BUT
1) Well fixed
2) Loose
3) Loose and no proximal bone stock
C - Distal to tip
Risk factors for dislocation
- Female
- THA for osteonecrosis
- Posterolateral approach
- Smaller head size
- GT non-union
- Revision THA
- Obesity
- Alcoholism
- Neuromuscular conditions
List 5 surgical options for the dislocated THA
- Implant revision
- GT advancement
- Constrained acetabular socket
- Conversion to bipolar hemiarthroplasty
- Resection arthroplasty
List factors influencing polyethylene wear:
Poly factors
- lower wear with highly cross linked
- lower wear with high articular surface conformity design
- Excessive free radical formation with irradiation in oxygen (as opposed to oxygen reduced environment with argon or nitrogen)
- Use of ram-bar extrusion followed by machining leads to higher wear than direct compression molding
- Long shelf life potentially leads to oxidation and more wear
TKA Factors
- Thinner poly increases wear (<8mm)
- Micromotion between insert and tibial tray (backside wear)
- Presence of debris (third body wear)
- Cam-Post impingment
THA Factors
- Femoral head size (smaller head increases linear wear; larger head increases volumetric wear)
- Looseness of components
- Malposition of components
Patient Factors
-Younger patient = more wear
