Reverse Shoulder Arthroplasty

1. Journal club on Reverse Shoulder
Arthroplasty
Presenter - Dr. Shubhanshu Ranjan Singh
Guide - Dr. John Mukhopadhaya

2. Introduction
• Cuff tear arthropathy coined by Neer et al. in 1983.
• Grammont and Baulet in 1985 developed delta
shoulder prosthesis.
• RSA first described by Grammont et al. in 1987
• Treatment for patients with rotator cuff tear
arthropathy for which non-operative treatment had
failed.
• Reversing the polarity of the ball and socket joint
• Ball component on the glenoid and articular socket at
proximal humerus.

3. Shoulder biomechanics
• Concavity compression
• Ball sitting in concavity of table
• Greater the depth of cavity greater displacing force
required to dislodge ball for a given compression load
• Central line represent a line perpendicular to articular
surface of glenoid and directed 10degree posterior to plane
of scapula.
• Rotator cuff provide compressive load
• Glenohumeral joint instability
• Disrupt glenohumeral and scapulothoracic motion are
coupled to maintain centre line beneath the humeral head
throughout the shoulder ROM.

4. Changes in geometry of shoulder joint
• Shift joint centre of rotation medially upto 20.9mm
relative to normal shoulder.
• Lowering the humerus increasing tensioning of
glenoid-humeral cup oriented 155degree wrt long axis
of humerus covers less than half of glenosphere.
• More deltoid fibres of deltoid during elevation,
improve force production, increase range of motion.
• Glenosphere offer greater potential arc of movement
of humerus before impingment of humeral component
occurs.
• Substantial changes in movement arms of muscles
spanning the glenohumeral joint.

5. Approach to RSA
• Delto-pectoral approach
– Minimun damage to deltoid
– Good ROM
– Greater glenoid exposure
– Compromises subscapularis which causes joint
dislocation
• Antero-superior deltoid splitting approach
– Postoperative joint stability
– Poor exposure of glenohumeral joint
– Impingement on scapula by proximal humerus

6. RSA component -
Glenoid base plate fixation
• Secure fixation to glenoid
• High quality bone
• Peripheral screws in good quality bone
• Chebli et al jses 2008
• Base of coracoid, spine of scapula
• Humphrey et al. jses 2008
• Micromotion decreased by increasing the lengh
diameter and inclination of peripheral screws
• Hopkins et al. jses 2008
• Locked screws – 29% less micro motion than
unlocked screw

7. Glenoid position
• Area of research
• For impingement free arc of motion
• 15 degree inferior tilt, lateralized and
concenteric.
• Rocking horse effect at glenoid.
• Gutierrez et al. corr 2008

8. Glenosphere
• Lateralization
• Scapular notching decreases
• Problem that transmit torque directly to
baseplate

9. Stability

10. Prosthesis design
• MG/MH
• LG/MH
• MG/LH
• LG/LH

11. Indication
• Rotator cuff arthropathy
• Arthritis with intact rotator cuff
• Tumor resection
• Postinfectious sequelae
• Revision of failed arthroplasty

12. Complication
• Instability
• Scapular notching
• Adduction deficit
• Glenoid/humerus fracture
• Acromial/scapular spine fracture
• External rotator cuff deficit
• Dislocation
• Deltoid rupture/injury
• CRPS

13. Instability
• Instability – 3.3%
• Within 90 days post-op : 60%
• Center of rotation
• Medialized 2.8%
• Lateralized 2.1%

14. Glenoid/humerus fracture

15. Acromial/scapular spine fracture
Componenets Fracture rate
Acromial Fx 1.6
Scapular spine Fx 1
CTA 2.6
PHF 0.7
RCT 2.5
Inflammatory 7.8
LG/MH 2.8
MG/LH 2.2
LG/LH 0.7
MG/MH 2.5

16. TAKE HOME MESSAGE
• RSA needs functional medial deltoid muscle
fibres.
• Glenoid component in position
– 10 degree Inferior tilt of glenoid fixation plate,
lateralization and concentric of glenosphere
• Central lag screw to increase compression at
baseplate bone junction
• Centre of rotation closer to anatomic centre of
rotation
• More varus neck shaft angle reduces notching
and associated complications