Indications
RA
OA
AVN
Contra-indications
Infection
Charcot
Paralysis of deltoid
Torn rotator cuff
Insufficient glenoid bone stock
Requirements
1. Functioning / repairable rotator cuff
- maintain stability
- maintain centre of rotation
- early failure if cuff deficient due to rocking horse effect on glenoid component
Repaired rotator cuff
MRI demonstrating intact cuff
2. Intact Deltoid
3. Reasonable glenoid bone stock
- commonly posterior bone loss in OA
- glenoid component must be completely supported by peripheral bone rim or early failure
Anatomy
Glenoid
Pear shaped Elliptical Vault Superior inclination
Alashkam et al. Clin Anatomy 2021
- approximately 70% glenoids are pear shaped due to presence of glenoid notch anterior margin
- remainder elliptical
- glenoid height varies 30 - 50 mm (mean 35 - 40)
- glenoid width varies 17 - 40 mm (mean 22 - 30 mm)
- inclination superior 4 - 5o
Version
- CT scan 410 normal shoulders
- mean retroversion 1o +/- 3o
- wide range -9o to 13o
- increased glenoid retroversion in men > women, and in dominant arm
Humeral head and scapula
Scapula 30o anteverted from coronal plane
- humeral head retroversion mean 26o +/- 11o
- wide range -2 - 60o
- increased glenoid and humeral (both) retroversion in men > women, and in dominant arm
Glenohumeral OA Classification
Samilson-Prieto
Grade 2 Grade 3
Grade 1: Osteophytes < 3 mm
Grade 2: Osteophytes 3 - 7 mm with slight narrowing GHJ
Grade 3: Ostephytes > 7 mm with GHJ narrowing and sclerosis
Glenoid morphology, bone stock and version
Issues
1. What is the morphology?
2. Is there sufficient bone stock for glenoid replacement?
3. Does version need to be addressed?
Walch classification glenoid morphology
Type A - centred humeral head, concentric wear, no humeral head subluxation
A1: minor central erosion
A2: major central erosion with humeral head protrusion
Type B - posterior subluxation of the humeral head, with biconcave glenoid and asymmetric wear
B1: narrowing of the posterior joint space
B2: biconcave glenoid with posterior rim erosion and retroverted glenoid
B3: monoconcave glenoid with > 15° retroversion or >70% posterior humeral head subluxation or both
Type C
C1: dysplastic glenoid with >25° retroversion
C2: biconcave, posterior bone loss, posterior translation of the humeral head
Type D: glenoid anteversion or anterior humeral head subluxation <40°
Type A2 Type B1
Type B2 Type B3
Type B3
Accuracy of Walch classification
- xray and CT of 100 shoulders with GHJ OA
- intra-observer reliability for xray and CT substantial (0.73)
- inter-observer reliability for xray and CT moderate (0.55, 0.52)
- CT v MRI
- largely comparable
- MRI less accurate at distinguishing between type B2 and type C
Progression over time
- 65 patients with shoulder OA with CT scans 2 years apart
- 8/42 type A progressed
- 17/19 type B1 progressed
Glenoid bone stock
Glenoid version measurement
1. Xray v CT
- glenoid version axillary xray v CT
- glenoid retroversion overestimated on xray in 86%
- mean difference in measurements between xray and CT was 6.5o
2. Include scapula
Chalmers et al. J Should Elbow Surg 2017
- 14 B2 glenoids
- glenoid version measurement accurate if > 50% of the scapula width included
3. Measurement techniques
a. Friedman method
- tip of the medial border of the scapula to the midpoint of the glenoid fossa
b. Scapula body method
- intersection of the scapula body axis and the glenoid surface
- 3o difference in measurement of glenoid version between the two
- excellent reliability for both measurement techniques
c. Glenoid vault method
- tip of scapula vault to centre of glenoid
Automated 3D measurement of version
- automated software 3D measurement versus 2D Friedman method in 60 shoulders
- mean difference of 2o
- 3D software reliable and accurate
Anatomical Total Shoulder Design
Issues
Constraint
Stems
Glenoid component design
Glenoid position
Glenoid version
Constraint
Early highly constrained had high failure rates
Modern design
- unconstrained
- high levels of glenohumeral mismatch and high levels of humeral head translation
- improved ROM and reduces rim stresses on glenoid
Semi Constrained
- cupped glenoid
Stem
Options
1. Long stems / short stems / resurfacing
2. Cemented versus uncemented
Stemmed humeral implants
Australian Joint Registry 2021
- 8324 aTSA with stemmed humeral implants
- 10 year revision rate 12%
- 14 year revision rate 15%
Cemented versus uncemented humeral implants
Werthal et al. Bone Joint J 2017
- 4636 shoulders (1167 cemented and 3469 uncemented)
- survival without loosening at 20 years 98% for cemented
- survival without loosening at 20 years 92% uncemented
Short stem
- systematic review of short stem TSA
- 13 studies with 823 shoulders at 33 month follow up
- 92% uncemented
- 2% humeral loosening, 1% revision for humeral loosening, 3% overall revision rate
Resurfacing
Willems et al EFORT Open Rev 2021
- systematic review and meta-analysis of 31 articles and 1944 stemless implants
- reduced intra-operative humeral fractures with stemless
- RCT of stemless and stemmed implants in 265 shoulders
- no difference in outcomes or complications
Glenoid design
Glenoid options
All poly v metal back
Peg v keel
Flat versus curved back
All poly v metal back
Uncemented metal back advantage
- secured with screws
- can convert to reverse easily if needed
Uncemented metal back disadvantage
- thicker - issues with overstuffing
- issues with metal / poly interface
- higher rate of revision
- Australian Joint Registry
- 11,000 aTSA at 5 years follow up
- revision rate cemented glenoid 3.7% v 17.9% uncemented
- most common revision reasons uncemented were rotator cuff insufficiency (4.4% v 0.4%) and instability (3.8% v 0.8%)
- revision for loosening 1.1% for both groups
Peg v keel cemented all poly
Welsher et al. JSES All Access 2019
- meta-analysis of comparative studies
- higher rate of revision with keel v peg
- no difference in functional outcomes
Glenoid positioning
Standard PSI
Options
- standard instrumentation based upon identifying the glenoid centre point
- navigation
- PSI - patient specific instrumentation
Burns et al. Should Elbow 2019
- comparison standard v navigation v PSI
- both navigation and PSI improved glenoid positioning
- high rate glenoid malposition with standard instrumentation
Type B2 glenoids
Options
1. Eccentric reaming
2. Reduce humeral head retroversion
3. Bone grafting
4. Augmented glenoids
Eccentric reaming
Limit to 10o
- compromises anterior bone stock
- risk peg penetration through vault and glenoid fracture
- associated with glenoid loosening
- excessive glenoid reaming associated with radiological loosening of glenoid
Glenoid bone graft
Risks
- graft resorption / nonunion / migration / loss of fixation
- systematic review of glenoid bone grafting in aTSR
- 7 articles
- revision rate 5.4% at 6 years
Augmented glenoids
Posterior-wedged augment Stepped augment Full wedged augment
Advantages
- good version correction
- preserves bone stock
- CT evaluation of standard glenoid v posterior stepped augmented glenoid
- posterior stepped glenoid better at correcting version in type B2 and B3
- difficult to restore ML joint line position with both with central glenoid erosion i.e. type A2 or B3
Sheth et al. Should Elbow 2022
- systematic review of augmented glenoid components
- 9 studies and 312 patients
- good version correction
- increased radiolucency seen with 16 wedges and 5 mm steps
Outcomes anatomical TSA
Revision
Australian Joint Registry 2021
- 10 year revision rate 12%
- 14 year revision rate 15%
- rotator cuff insufficiency most common indication for revision
- followed by instability / loosening / infection / fracture
Revision by age
Australian Joint Registry 2021
- 10 year revision rates
- < 55 14%
- 55 - 64 16.5%
- 65 - 74 11%
- > 74 8%
aTSA v revTSA for OA
Parada et al. J Should Elbow Surg 2021
- 2224 aTSA complication rate 11%, revision rate 5.6%
- aTSA complications: 3% cuff failure, 2.5% aseptic glenoid loosening, 1.3% infection rate
- 4158 revTSA complication rate 9%, revision rate 2.5%
- revTSA complications: 2.5% acromial/scapular fracture, 1.4% instability, 1.2% pain