Shoulder Arthroplasty

Question 1

Why in TSA we have more risk of glenoid loosening?

Answer 1

cemented all-polyethylene glenoid resurfacing is standard of care

Glenoid is less constrained: leads to greater sheer stresses and is more susceptible to mechanical loosening

Question 2

2 Factors required for success of TSA

Answer 2

1- Rotator cuff intact and functional

an isolated supraspinatus tear without retraction can proceed with TSA

incidence of full thickness rotator cuff tears in patients getting a TSA is 5% to 10%

if positive impingement signs on exam, order a pre-operative MRI

2- Glenoid bone stock and version

if glenoid is eroded down to coracoid process then glenoid resurfacing is contraindicated

Question 3

What are the outcomes of TSA?

Answer 3

◦ pain relief most predictive benefit (more predictable than hemiarthroplasty)

reliable ROM

good survival at 10 years (93%)

good longevity with cemented and press-fit humeral components

worse results for post-capsulorrhaphy arthropathy

Question 4

What is the Walch Classification of Glenoid Wear

Answer 4

Type A

well-centered

A1 minor erosion

A2 deeper central erosion

Type B

head sub-luxated posteriorly

B1 posterior wear

B2 severe biconcave wear

Type C

Glenoid retroversion of more than 25 degrees (dysplastic in origin)

Question 5

What are the indications of TSA?

Answer 5

pain (anterior to posterior), especially at night, and inability to perform activities of daily living

glenoid chondral wear to bone

preferred over hemiarthroplasty for osteoarthritis and inflammatory arthritis

posterior humeral head subluxation

Question 6

6 Contraindications to TSA?

Answer 6

1. insufficient glenoid bone stock
2. rotator cuff arthropathy
3. deltoid dysfunction
4. irreparable rotator cuff (hemiarthroplasty or reverse total shoulder are preferable) –> risk of loosening of the glenoid prosthesis is high (“rocking horse” phenomenon)
5. active infection
6. brachial plexus palsy

Question 7

Exam to obtain before TSA?

Answer 7

CT determine Glenoid version and Glenoid bone stock

Question 8

Treatment for glenoid deficiency?

Answer 8

build up with iliac crest autograft or part of the resected humerus

do not use cement to build up the deficiency

Question 9

Treatment of retroverted glenoid

Answer 9

• build up posterior glenoid with allograft
• eccentrically ream anterior glenoid

Question 10

Glenoid component

Answer 10

• Convex backside superior to flat
• Recreate neutral version
• Peg design is biomechanically superior to keel design
• Polyethylene-backed components superior to metal-backed components
• glenoid not large enough to accommodate both metal and PE
• Uncemented glenoid has a lower rate of loosening
• Conforming vs. nonconforming

both have advantages and neither is superior

conforming is more stable but leads to rim stress and radiolucencies

nonconforming leads to increased polyethylene wear

Question 11

Humeral stem fixation

Answer 11

cemented stem or un-cemented porous-coated implants

position of humeral stem should be 25-45° of retroversion

if position of glenoid retroversion is required, then the humeral stem should be less retroverted to avoid posterior dislocation

avoid valgus positioning of humeral stem

avoid overstuffing the humeral head

increases joint reaction forces and tension on the rotator cuff

the top of the humeral head should be 5 to 8 mm superior to the top of the greater tuberosity

Question 12

What is the Limiting factor in early post-operative rehabilitation of TSA?

Answer 12

risk of injury to the sub-scapularis tendon repair

Question 13

10 Complications of TSA

Answer 13

1. Glenoid loosening
2. Humeral stem loosening
3. Sub-scapularis repair failure
4. Malposition of components
5. Improper soft tissue balancing
6. Iatrogenic rotator cuff injury
7. Stiffness
8. Infection
9. Neurologic injury
10. Periprosthetic fracture

Question 14

What is the most common cause of TSA failure?

And what are the risk factors?

Answer 14

Glenoid loosening (30% of primary revisions)

2.9% re-operation rate for loosening (28% with revision)

radiographic lines

presence of radiographic lines does not correlate with symptoms

progression of a radiographic line does correlate with symptoms

progression present in 50% of patients as early as 3 to 4 years after TSA

radiolucency around the glenoid does not always correlate with clinical failure

at 3- and 7-year follow-up did not correlate with poor functional outcomes or pain

Question 15

When and how can iatrogenic rotator cuff injury occur?

Answer 15

1. can occur if humeral neck osteotomy is inferior to level of rotator cuff insertion
2. overstuffing glenohumeral joint leading to attritional supraspinatus and subscapularis tears

Question 16

What is an acceptable periprosthetic fracture alignment?

Answer 16

acceptable fragment alignment ≤ 20° flexion/extension, ≤ 30° varus/valgus, ≤ 20° rotation malalignment

Question 17

What is Wright and Cofield classification for peri-prosthetic fracture?

Answer 17

Question 18

Questions to aks post-op 1 year TSA?

Answer 18

Pain

Instability

Weakness

Question 19

Fall after TSA with increased ER on clinical exam?

Answer 19

Subscapularis tear

Question 20

How can the rotator cuff tendons be injured during humeral osteotomy?

Answer 20

The rotator cuff tendons can be inadvertantly cut or detached during a TSA if the head cut is made either too distally or in excessive retroversion.

Question 21

What the most common cause of late TSA infection?

Answer 21

Propionibacterium acnes. This is a slow growing organism that is present in over 50% of chronic infections.

Question 22

Origin of the subscapularis nerve?

Answer 22

Posterior cord of the brachial plexus

The upper and lower subscapular nerves come off the posterior cord of the brachial plexus and innervate the subscapularis muscle.