Total shoulder arthroplasty Flashcards
why is the glenoid susceptible to mechanical loosening
low constraint but greater shear stresses
contraindicatiosn for anatomic total shoulder?
- irreparable and deficient rotator cuff (risk loosening due to “rocking horse” phenomenon
- loss of glenoid bone stock (erosion to the coracoid) = no glenoid resurfacing
- deltoid dysfunction
- brachial plexopathy
Walch Classification of Glenoid Wear
A: well centered, 1: minor erosion, 2: deep central erosion
B: posterior head subluxation, 1: posterior wear, 2: severe biconcave wear
C: glenoid retroversion >25 deg (dysplastic)
Management of glenoid deficiency or retroversion
- build up with iliac crest autograft
- do not build up with cement
- eccentrically ream the anterior glenoid
What is the appropriate position of the humeral stem?
25-45 deg retroversion
- use relatively less if you have to retrovert the glenoid in order to avoid posterior dislocations
humeral head should be 5-8mm superior to the top of the GT
Early rehab for TSA:
passive or active-assist only during early phase
- risk of subscap tendon repair rupture is real
Most common cause of TSA failures:
GLENOID LOOSENING (30%)
- humeral stem loosening
- subscap repair failure
- improper balancing
- component malposition
- iatrogenic rotator cuff deformity
- axillary nerve injury
- musculcutaneous nerve injury
Is aspiration sensitive for P. acnes infections?
no. forms rapid biofilm
- aspiration sensitivity is only 17%
- keep cultures for 10-14 days, anaerobic cultures (average 9 days to grow)
What is normal hmeral head retroversion?
20 deg
TSA vs Hemi for GH OA?
TSA demonstrates improved pain scores, mobility, and activity at 2 year follow up
Known risk factors for post-op subscap rupture?
- prior subscap related surgeries
Metal or poly backed glenoid component?
poly backed component, cemented
- metal backed components have higher revision rates than all - poly
What is normal glenoid version
0-3 degrees
What is the goal of version for the glenoid component in TSA?
neutral to slight anteversion
Can you eccentrically ream to correct glenoid retroversion for your TSA?
yes, but if retroversion is >15 deg then you can’t safely correct with eccentric reaming when using a glenoid component with peripheral pegs because you will penetrate into the glenoid vault (Clavert 2007)
If >15 deg version, should use allograft to build up the posterior glenoid
