1. The Optimal Patient-Specific
Placement of the Reverse
Shoulder Component
1

2. Supervisor: Prof C. Scheffer
Consultant: Dr J. De Beer
Masters Student: Mr S. Delport

3. Review of Discussion
1. Introduction
2. Motivation
3. Objectives
4. Reverse Shoulder
Simulation Software
5. Simulation Results
6. Future Work
7. Conclusion

4. Humeral
Head
Glenoid
Humerus
Clavicle
Scapula
Introduction
• Shoulder replacement background
 Anatomy
1

5. Introduction
• Shoulder replacement background
 Anatomy
Subscapularis
Supraspinatus
Infraspinatus
Deltoid
2
Anterior Posterior

6. Humeral
Stem
Polyethylene
Insert
Glenosphere
Baseplate
Introduction
• Shoulder replacement background
 Hemiarthroplasty
 TSA
 RSA
3

7. Introduction
Study by Sperling et al. (2011)
• 261 shoulders
• 3 year follow-up
• Improvement after RSA
 Abduction, forward flexion, pain relief
• High number of complications (mean, 24.4%)
 Scapular notching, glenoid and humeral
dissociations, glenohumeral dislocation,
nerve injury
4

8. Introduction
DeFranco and Walch (2012)
• RSA clinical outcome factors
 Pre-operative diagnosis
 Function of deltoid and rotator cuff muscles
 Prosthesis biomechanical design
 Orientation and position of the reverse
shoulder components
5

9. Motivation
Effects of reverse shoulder component placement
• Previous studies
 Glenohumeral motion
 Single elevation plane
• Current study
 Shoulder complex motion
 Coronal, scapular and sagittal elevation planes
6

10. Objectives
• Develop a simulation package to determine
optimal patient-specific placement of the
reverse shoulder components
• Analyse the influence of the placement of
the reverse shoulder components on
humerothoracic ROM and adduction deficit
• Analyse the influence of the design of the
reverse shoulder components on
humerothoracic ROM and adduction deficit
7

11. Reverse Shoulder Simulation Software
• Work Flow
Start
Import
Patient Data
Setup
Patient
Position
Implant
Simulate
Desired
ROM
Achieved
Generate
Report
End
no
yes
8

12. • Matlab software
 Graphical User Interface Design Environment
• Patient data
 CT scan
 Sternum, C7 & T8, clavicle, scapula and
humerus
 Mimics software – STL files
Reverse Shoulder Simulation Software
9

13. Reverse Shoulder Simulation Software
• Implant data
Tornier Aequalis® – Reversed II System
Glenoid Components Humeral Components
Glenosphere Baseplate Stem Polyethylene Insert
Ø 36 mm – concentric
Ø 36 mm – 4 mm inferior
Ø 36 mm – 3 mm lateral
Ø 42 mm – concentric
Ø 42 mm – 4 mm inferior
Ø 42 mm – 3 mm lateral
Ø 25 mm
Ø 29 mm
Ø 36 mm – concentric
Ø 36 mm – 2 mm inferior
Ø 36/42 mm – combination
6 mm, 9 mm or 12 mm
6 mm, 9 mm or 12 mm
6 mm, 9 mm or 12 mm
10

14. Shoulder coordinate systems
• International Society of Biomechanics
 Thorax coordinate system
Reverse Shoulder Simulation Software
11
C7 IJ
PX
C7
T8

15. Shoulder coordinate systems
• International Society of Biomechanics
 Clavicle coordinate system
Reverse Shoulder Simulation Software
12
AC
SC

16. Shoulder coordinate systems
• International Society of Biomechanics
 Scapula coordinate systems
Reverse Shoulder Simulation Software
13
AA
AI
SCS1 SCS2
AI
TS
TS
Glenoid
Centre

17. Shoulder coordinate systems
• Boileau and Walch (1997)
 Humerus coordinate system
Reverse Shoulder Simulation Software
14
GH
ME
LE
Upper Shaft
Centre Line

18. • Shoulder complex motion
 Sternoclavicular

 Scapulothoracic
Upward RotationInternal Rotation Posterior Tilting
Acromioclavicular
Joint
ElevationProtraction Posterior Rotation
Scapulothoracic
Joint
Reverse Shoulder Simulation Software
15

19. • Shoulder complex motion
 Humerothoracic
Reverse Shoulder Simulation Software
16
ElevationElevation Plane
Glenohumeral
Rotation Centre

20. Reverse Shoulder Simulation Software
Shoulder complex motion data
• Ludewig et al. (2009)
 Normal shoulders
 12 subjects
 Coronal, scapular and sagittal elevation planes
 0 º – 120 º humerothoracic elevation
 ISB standards
• Motion equations
17

21. Reverse Shoulder Simulation Software
• Shoulder complex motion simulation
 Combined AD
 Combined humerothoracic ROM
18
Impingement
Adduction
Deficit
Humerothoracic
ROM

22. Simulation Results
• Simulation tests
 Validated shoulder model
 Glenoid component inclination angle
 Humeral component retroversion angle
 Reaming depth
 Component combinations
 Implant design changes
19

23. Simulation Results
• Glenoid component inclination
20
-10 º -5 º 0 º 5 º 10 º
• Humeral component angles
LE ME
Humerus
Retroversion
Head and
Neck AxisHead and
Neck Axis
Neck-shaft
Angle
Upper Shaft
Centre Line

24. Simulation Results
21

25. Simulation Results
• Humeral component retroversion
35
30
15
10
15 20 25 35 45
Frequency
Humeral Component Retroversion Angle [º]
40
5
30 40
0
20
25
22

26. Simulation Results
• 42 mm glenosphere
330
300
270
240
-10 -5 0 5 10
CombinedHumerothoracicROM[º]
Glenoid Inclination Angle [º]
Concentric; 29 mm
Inferior; 29 mm
Lateral; 29 mm
Concentric; 25 mm
Inferior; 25 mm
Lateral; 25 mm
360
210
23

27. Simulation Results
• 42 mm glenosphere
90
60
30
0
-10 -5 0 5 10
CombinedAD[º]
Glenoid Inclination Angle [º]
Concentric; 29 mm
Inferior; 29 mm
Lateral; 29 mm
Concentric; 25 mm
Inferior; 25 mm
Lateral; 25 mm
120
24

28. Simulation Results
• Eccentricity design change
300
270
240
210
36 mm 42 mm
CombinedHumerothoracicROM[º]
Glenosphere
Inferior
Lateral
Inferior & Lateral
360
25
330

29. Simulation Results
• Eccentricity design change
60
40
20
0
36 mm 42 mm
CombinedAD[º]
Glenosphere
Inferior
Lateral
Inferior & Lateral
100
26
80

30. Simulation Results
• Inclination force distribution – Gutiérrez et al.
27
Most
Desirable
Concentric
Lateral
Eccentric
Inferior
Eccentric
Acceptable
Least
Desirable

31. Simulation Results
• 25 mm baseplate
• 42 mm glenosphere
• Inferior eccentric with superior inclination
• Combined eccentricity for neutral inclination
28

32. Future Work
• Post-operative active ROM clinical study
• Include different reverse shoulder component
types
• Record large number of simulation data
• Determine patient-specific humeral
component retroversion angle
29

33. Conclusion
• Objectives were addressed and successfully
achieved
• May assist surgeons in pre-operative
implant selection and placement
• More inexperienced surgeons can attempt a
RSA with greater confidence
• Reduce surgery cost and time
• May improve implant survival rates and
long-term clinical outcomes
30

34. Thank you