This document summarizes a journal club presentation on reverse shoulder arthroplasty. It discusses the history and development of reverse shoulder arthroplasty. It also covers changes in shoulder biomechanics with reverse arthroplasty, including shifting the center of rotation medially and lowering the humerus. Component design, surgical approaches, indications, complications, and strategies to reduce complications like scapular notching are summarized. The take home message emphasizes the importance of medial deltoid function and optimizing glenoid component position and fixation to improve outcomes.

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