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,unstableRead More