Shoulder Arthroplasty

1. Shoulder Arthroplasty
Seminar
1st Oct 2015
Dr Udit Biswal

2. History
• 1893- Dr Jules Emile Pean- 1st total
shoulder replacement for TB
• Humeral stem of platinum and
leather, with rubber head coated with
paraffin

3. • 1st Generation Arthroplasty- 1950 – Fredreich Krueger- vitallium
implant crafted from molding on cadaveric humerus

4. • 1951- Dr Charles Neer- Neer-I non constrained humeral prosthesis for humeral head fracture,
vitallium
• 1973- Neer II – nonconstrained prosthesis, keeled, rectangular, required intact rotator cuff,
glenoid component
• Bad results in cuff tears
• “a massive rotator cuff tear with superior humeral head migration and diminished
acromiohumeral distance with “femoralization” of the tuberosities and “acetabularization” of
the acromion” – Dr Charles Neer

5. • 2nd generation arthroplasties- modular
• 3rd generation arthroplasties- 1980s – Boileau and Walch- anatomic
variations concept
• Humeral head variations- multiple diameters
• Retroversion varies by more than 50 degrees- anatomic neck cut
• Prosthetic stem with variable neck shaft angle

6. HUMERAL COMPONENT: DESIGN
3 generations
Monoblocks
Modular heads
and ingrowth
coating
Anatomical /
adaptable

7. 1st generation
• Monoblocks
• Pioneered by Neer (Neer I in 1951 and Neer-II in 1973)
• Limited sizes available
• Bad results

8. 2nd generation
• Modular heads and ingrowth coating
• Ideal head size and soft tissue balancing
• Easier removal from stem at revision
• Minimal improvement in results

9. 3rd generation
• Anatomic/ adaptable
• Allow positioning of prosthetic head wrt stem in AP and ML planes
• Allow various degrees of head inclination

10. Resurfacing implants
• Cemented or coated with hydroxyapatite
• No intramedullary stem
• Proximal humeral deformity necessiting osteotomy
• RA patients needing elbow arthroplasty
• Easier to revise humeral side
• Difficult to achieve stability if local bone stock poor
• Glenoid exposure hindered by native humeral head preservation
• Soft tissue balance difficult due to unalterability of humeral head
• Difficult to assess bone – implant interface

11. HUMERAL COMPONENT : FIXATION
• Neer’s prosthesis- smooth surface- polymethylmethacrilate cement
• 50 % incidence of progressive radiolucent lines and migration when
used without cement e.g for good bone quality, without texturing
• Advantages of cemented fixation
 low rate of mechanical failure
Antibiotics can b added
Adequate humeral component positioning in poor bone stock,
proximal humerus fractures or deformities
Difficult to remove well fixed cement at revision
Radial nv injury through cement extrusion through nutrient artery
foramen
Distal migration during pressurisation – use bone plug

12. • Limited studies on outcomes of cementless fixation
• Sperling et al. – 6 % mechanical failure with first generation Cofield
component- coated only beneath head
• Current heads have ingrowth surfeces – variable distance
• For primary surgery- short length fixation chosen
• Cementless fixation standardly used except when cement is
absolutely needed such as proximal humerus fractures for stability,
where even cancellous bone grafting doesn’t give adequate stability

13. GLENOID COMPONENT
• All polyethelene implant, slight convex back, keels for glenoid vault
• Pegged- better for normal bone, Keeled- rheumatoid disease (with
bone loss)
• Pegged- more accurate, less radiolucent lines in post op radiograph

15. • Most glenoids – polymethylmethacrilate cement
• Hybrid glenoids- polyethylene or metal ingrowth
• Self pressurizing glenoids- pegs maintain pressure when cement
curing
• Glenoid loosening- most common mode of failure
• Cementless glenoid- thin polyetyhylene dissociates
• Possible with porous titanium or tantalum glenoids

16. Gleno humeral mismatch
• Postero superior quadrant of glenoid- primary
contact
• Too superior head- supraspinatus impingement
• Too inferior head- GT-acromion impingement,
internal impingement at glenoid rim
• Too anterior/ posterior- glenoid rim
impingement & subscapularis/ posterior cuff
tendon stretch
• 2-4mm larger glenoid than humeral head-
avoids edge loading and “rocking horse effect”
• Larger glenoids- transverse plane stability more

17. Indications
• Glenoid loosening
• Glenoid exposure difficult
• More operating time
• For OA and RA- better pain relief and function
• Glenoid erosion in hemiarthroplasty >>> Glenoid loosening in TSA
• Risk factors for glenoid loosening
1. Poor bone stock
2. Rotator cuff deficiency- superior migration, eccentric loading
3. Poor cementing- radiolucent lines

18. Indications
Deficient forward elevation – TSA better, if 90 or more then hemiarthroplasty preferred

19. Matsen et al –
indications of hemiarthroplasty
1. Sufficient intact glenoid arc
2. Fixed proximal migration- cuff
tear arthropathy
3. Insufficient glenoid bone stock
4. Past history of shoulder
infection
5. Heavy loading expected
occupationally
6. Medical comorbidities
mandating less OT time
1. Recent sepsis
2. Paralytic shoulder
3. Cuff/ deltoid deficiency
4. Patient consent and
cooperation lacking
5. Uncorrectable glenohumeral
instability
Contraindications to both

20. Results of TSA
• Primary OA- TSA superior to hemi (Garstmann et al, Sperling et al). Both
have > 90 % patient satisfaction
• Osteonecrosis- Hemi has good results with idiopathic (>80%). In post
traumatic ON and where tuberosity osteotomy needed (sequeale of
fractures) results worse
• Inflammatory arthritis- Both hemi and TSA good results. TSA > hemi if
rotator cuff intact. Both fail if rotator cuff torn or unstable
• Cuff tear arthropathies- Hemi is preferable , Pain relief 70 % and mean
forward elevation only 90

21. Pre and post op hemiarthroplasty in cuff tear

22. Shoulder arthroplasty in fractures
• Classic 4 part fractures, head splitting
and head impaction fractures-
hemiarthroplasty
• Valgus impacted 4 part #s, 3 part #s with
osteopenia – locked plating
• Displacement of anatomic landmarks of
approach
• Implant should facilitate tuberosity
reconstruction – narrow proximal
profile, hydroxyapatite coating
• Heavy horizontal + vertical non
absorbable sutures through rotator cuff,
implant and diaphysis

23. • Adequate head – tuberosity relation needs recreation
• Bone autograft should be placed between # fragments to avoid
cement interposition
• Immobilise 4-6 weeks in mild internal rotation. Excess IR – stresses
the GT repair
• Pain minimal in absence of complications
• Average elevation is 90-100 degrees only

24. Reverse shoulder arthroplasty
• 1987 – Dr Paul Grammont – reverse shoulder prosthesis-
polyethylene humeral cup – cobalt-chromium-molybdenum
glenosphere
• Joint center at glenoid surface(medialised 20.9 mm from anatomic
shoulder)
• More fibers of deltoid recruited

25. Reverse shoulder arthroplasty- biomechanics
• Humeral cup oriented at 155°- less than 50% of glenosphere contact
• Distalises humerus- tenses deltoid- improved deltoid lever arm and
semi-constrained nature give active elevation gain
• Overtensioning !- acromion # & reduced function in mid-long term

26. • Glenosphere – greater arc offered before impingement
• Centre of rotation at glenoid bone surface – reduced torque and
shear stress at glenosphere-bone interface as in lateralized
glenosphere, causes base plate failure
• Average abduction and flexion moment arms of middle deltoid are
increased by 17.2 and 14.8mm respectively
• Posterior deltoid also recruited for abduction
• Reduced muscle stress in pushing and lifting activities
• Reduces external rotation moment arms, increases internal rotation
moments- detrimental if infraspinatus and teres minor dysfunctional

27. Indications Contraindications
• Glenoid bone loss
• Deltoid paralysis
• Isolated supraspinatus tear – TSA is
better as shoulder is balanced
• Cuff tear without arthritis
• Cuff tear with full active elevation-
look for biceps tendon (static head
depressor & victim of tendinitis in
RCT) – tenotomy, arthroscopic
debridement

28. Surgical approaches
Deltopectoral
• Minimises damage to deltoid
• Better glenoid exposure- better
assessment of glenosphere tilt
and version
• Subscapularis damaged*
Deltoid splitting
• Subscapularis intact
• Glenoid superior tilt error due to
inadequate exposure- intra-
operative scapula impingement
• Unintentional excessive cut from
humerus leading to use of large
poly insert

29. Scapular notching & adduction deficit
• Medial impingement “notching”
due to medialisation of centre of
rotation
• Gradual erosion of scapula neck
inferior to pegs
• Sirveaux classification – Grade 4
can cause glenoid loosening
• Adduction deficit
• Poly wear debris lead to
osteolysis
• Glenosphere lateralization- upto
10mm of lateral offset

31. BIO-RSA (Bony increased offset)
• Autograft between
glenosphere & glenoid
• Lateralises rotation without
stressing glenosphere
• No notching and no base
plate failure

32. Reverse bearing surfaces
• Poly glenosphere and metal
humeral cup- no poly wear in
the event of impingement

33. Inferiorly angulated glenosphere
• To reduce scapular notching
• More reaming needed- poor
bone stock
• Further medialisation of center
of rotation
• Negates lateralization if used
with lateral offset glenospheres
• Uneven force distribution
leading to rocking horse effect

34. External rotation deficit
• Reduced moment arm of
external rotators
• fatty atrophy of teres minor
• damage to suprascapular nerve
by superior and posterior
glenosphere screws
• Better in 90° abducted position-
deltoid recruitment
• Lateralised designs theoretically
improve- clinically not proven
• Increase humeral retroversion –
shifts arc of rotation-
impingement free ext rot at cost
of int rot
• Impinges earlier in internal
rotation

35. Dislocation
• MC complication
• More common in revision RSAs for fracture hemiarthroplasties
• Irreparable subscapularis tears
• Increased glenoid retroversion- avoid more than 10°, keep neutral or
slightly anteverted
• Keep inferior tilt of glenosphere

36. Non specific complications
• Infections- DM, prior shoulder surgeries predispose
Debridement, IV antibiotics better function than resection arthroplasty
• Hematoma
• Nerve palsies- axillary nv in RSA, brachial plexus in TSA, more
common in RSA, arm lengthening mean 2.7+/-1.8 cm, transient
palsies only

37. Implant specific complications
• Internal glenoid notching
• Muscle imbalance and instability
• External rotation deficit
• Mechanical dismantling of humeral prosthesis
• Glenosphere disengagement with screw breakage
• Acromion fractures- classified by Crosby et al.
a) Type I- small avulsion of anterior acromion
b) Type II-#s through ant acromion, post to AC jt
c) Type III- #s of posterior acromion or spine of scapula

38. Implant specific complications (contd)
• Glenosphere loosening in poor bone stock