Background

total shoulder arthroplast allPoly Glenoid

 

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

 

TSR plus cuff repair

Repaired rotator cuff

 

Shoulder OAShoulder OA intact cuff on MRI

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

 

Shoulder CT Glenoid OvalShoulder Glenoid CT Pear ShapedTriangular vault scapulaGlenoid Inclination

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

 

Matsumura et al. JSES 2014

- 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

 

Matsumura et al. JSES 2014

- 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

 

Glenohumeral joint OA Grade 2Type 3 Glenohumeral joint OA

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

 

Walch Glenoid Morphology Classfication

 

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 glenoidType B2 glenoid

Type A2                                                   Type B1

 

Type B2 glenoidScapula CT for total shoulder

Type B2                                                  Type B3

 

Type B3

Type B3

 

Accuracy of Walch classification

 

Shukla et al. JSES 2019

- 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)

 

Lowe et al. JSES 2017

- CT v MRI

- largely comparable

- MRI less accurate at distinguishing between type B2 and type C

 

Progression over time

 

Walker et al. JBJS Am 2018

- 65 patients with shoulder OA with CT scans 2 years apart

- 8/42 type A progressed

- 17/19 type B1 progressed

 

Glenoid bone stock

 

CT TSR Preop Glenoid CystsRheumatoid shoulder CTType A1 glenoid

 

Glenoid version measurement

 

1. Xray v CT

 

Nyffeler et al. JSES 2003

- 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

 

Scapula CT for total shoulderFriedman method glenoid version

 

b. Scapula body method

- intersection of the scapula body axis and the glenoid surface

 

Type B2 glenoidScapula body method glenoid version

 

Roleau et al. JSES 2019

- 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

 

Type B2 glenoidGlenoid vault version measurement

 

Automated 3D measurement of version

 

Boileau et al. JBJS Am 2018

- automated software 3D measurement versus 2D Friedman method in 60 shoulders

- mean difference of 2o

- 3D software reliable and accurate

 

3D CT glenoid 13D CT glenoid 2

 

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

 

TSR Uncemented StemTSR Cemented Stem

 

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

 

Short stem aTSAShort stem TSA 2

 

Erickson et al. JSES Int 2020

- 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

 

TSR No Stem

 

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

 

Wiater et al. JBJS Am 2021

- 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

 

TSR Metal Backed Glenoid

 

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

 

Page et al. JSES 2018

- 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

 

Keeled glenoid polyPegged glenoid 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 glenoid instrumentationPSI glenoid

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

 

Walch et al JSES 2011

- excessive glenoid reaming associated with radiological loosening of glenoid

 

Glenoid bone graft

 

Risks

- graft resorption / nonunion / migration / loss of fixation

 

Zhang et al Should Elbow 2021

- systematic review of glenoid bone grafting in aTSR

- 7 articles

- revision rate 5.4% at 6 years

 

Augmented glenoids

 

Augmented glenoids

 

Types glenoid augments

Posterior-wedged augment               Stepped augment                    Full wedged augment

 

Advantages

- good version correction

- preserves bone stock

 

Richetti et al. JSES 2021

- 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 reasons aTSARevision aTSA

 

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