RSA REGIONAL TEACHING JAN 2010 Notes | EduRev

 Page 1


REVERSE SHOULDER 
ARTHROPLASTY (RSA)
www.gnulc.com
Andreas F Hinsche
Consultant Shoulder and Elbow Surgeon
Page 2


REVERSE SHOULDER 
ARTHROPLASTY (RSA)
www.gnulc.com
Andreas F Hinsche
Consultant Shoulder and Elbow Surgeon
RSA-NORMAL SHOULDER 
KINEMATICS
• Abduction/Elevation
– Joint stability dependent on balance between 
www.gnulc.com
– Joint stability dependent on balance between 
Deltoid (upwards force) and Rotator Cuff
(downwards force)
– Muscle contraction causes shear (upwards 
humeral displacement) and compression
forces (joint stability)
Page 3


REVERSE SHOULDER 
ARTHROPLASTY (RSA)
www.gnulc.com
Andreas F Hinsche
Consultant Shoulder and Elbow Surgeon
RSA-NORMAL SHOULDER 
KINEMATICS
• Abduction/Elevation
– Joint stability dependent on balance between 
www.gnulc.com
– Joint stability dependent on balance between 
Deltoid (upwards force) and Rotator Cuff
(downwards force)
– Muscle contraction causes shear (upwards 
humeral displacement) and compression
forces (joint stability)
RSA-NORMAL SHOULDER 
KINEMATICS
– Deltoid shear forces > compression forces 
until 60 degrees elevation!
www.gnulc.com
– Abduction torque generated by Deltoid
• At 30 degrees 70%
• At 60 degrees 80%
• At 90 degrees 85%
Page 4


REVERSE SHOULDER 
ARTHROPLASTY (RSA)
www.gnulc.com
Andreas F Hinsche
Consultant Shoulder and Elbow Surgeon
RSA-NORMAL SHOULDER 
KINEMATICS
• Abduction/Elevation
– Joint stability dependent on balance between 
www.gnulc.com
– Joint stability dependent on balance between 
Deltoid (upwards force) and Rotator Cuff
(downwards force)
– Muscle contraction causes shear (upwards 
humeral displacement) and compression
forces (joint stability)
RSA-NORMAL SHOULDER 
KINEMATICS
– Deltoid shear forces > compression forces 
until 60 degrees elevation!
www.gnulc.com
– Abduction torque generated by Deltoid
• At 30 degrees 70%
• At 60 degrees 80%
• At 90 degrees 85%
RSA-CUFF DEFICIENCY
• Deltoid lost counterbalance +/- support
(SST, IST, TM, SCC)
• Loss of fulcrum for elevation
• Shear component of deltoid causes 
www.gnulc.com
• Shear component of deltoid causes 
humeral upwards migration
• Unstable joint
• Deltoid fibres retract
• Remaining Function depends on 
remaining anterior/posterior force couple
Page 5


REVERSE SHOULDER 
ARTHROPLASTY (RSA)
www.gnulc.com
Andreas F Hinsche
Consultant Shoulder and Elbow Surgeon
RSA-NORMAL SHOULDER 
KINEMATICS
• Abduction/Elevation
– Joint stability dependent on balance between 
www.gnulc.com
– Joint stability dependent on balance between 
Deltoid (upwards force) and Rotator Cuff
(downwards force)
– Muscle contraction causes shear (upwards 
humeral displacement) and compression
forces (joint stability)
RSA-NORMAL SHOULDER 
KINEMATICS
– Deltoid shear forces > compression forces 
until 60 degrees elevation!
www.gnulc.com
– Abduction torque generated by Deltoid
• At 30 degrees 70%
• At 60 degrees 80%
• At 90 degrees 85%
RSA-CUFF DEFICIENCY
• Deltoid lost counterbalance +/- support
(SST, IST, TM, SCC)
• Loss of fulcrum for elevation
• Shear component of deltoid causes 
www.gnulc.com
• Shear component of deltoid causes 
humeral upwards migration
• Unstable joint
• Deltoid fibres retract
• Remaining Function depends on 
remaining anterior/posterior force couple
RSA – CLASSIFICATION OF
CUFF TEAR ARTHROPATHY
HAMADA et al.
• Radiographic
• Acromiohumeral Interval 
(AHI) 
SEEBAUER et al.
• Biomechanical
• Sup. Migration and
Degree of Instability
www.gnulc.com
• Grade1 AHI > 6mm
• Grade 2 AHI < 6mm
• Grade 3 2 + acetabul.
• Grade 4 3 + GHJ-OA
• Grade 5 HH-collapse
• Type 1A: centred,stable
• Type 1B: centred,medialis.
• Type 2A: decentred,lim.stable
• Type 2B: decentred,unstable