reverse total shoulder arthroplasty reza omid, m.d. assistant professor orthopaedic surgery shoulder...
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Reverse Total Shoulder Arthroplasty
Reza Omid, M.D.Assistant Professor Orthopaedic
SurgeryShoulder & Elbow Reconstruction
Sports MedicineKeck School of Medicine of USC
Glenohumeral OA
•Glenoid cartilage is typically spared anteriorly
•Wear is more pronounced posteriorly with appearance of a “biconcave glenoid”.
Indications for RTSA
•Rotator cuff dysfunction•Proximal humerus fractures
•Glenoid bone loss•Revision TSA
Reverse TSA
• Predictable outcome• Best TSA or Hemi is better
than the best reverse• Best indication is CTA• Worst indication is revision
arthroplasty• Not a good option if good
FE
REVERSE TSA
Two Types: •Lateralized
• Initial design of the 70’s but abandoned• Frankle design recently
•Medialized • Grammont design 1991• Most common design (zimmer, tornier, depuy,
etc)
Biomechanics
1. Medialization converst the shear force to a compressive force at the baseplate/glenoid interface.
2. Distalization tensions deltoid
3. Semiconstraint nature overcomes deficient cuff
Constraint
•Under active conditions, a mismatch of 4mm was found to produce translations (1-2mm) that most closely reproduced those observed with the original anatomy
•(Williams JOR 1996:14(6):986-993).
Benefits of Medialization
•Biomechanically superior (compression force at baseplate glenoid interface)
Integra Reverse Shoulder System
Central Screw
Peripheral Screws
Baseplate
Glenosphere
Humeral Insert
Humeral Body
Stem
GlenosphereGlenospheres made of CoCr
38mm diameter
Many options to varying patient anatomy, increase ROM and prevent scapular
notching– Concentric Glenosphere, 2mm Lateralized– Concentric Glenosphere, 5mm Lateralized
– 4mm Eccentric Glenosphere, 2mm Lateralized
– 4mm Eccentric Glenosphere, 5mm Lateralized
– 4mm Eccentric Glenosphere, Inferior Hooded 2mm Lateralized
Lateralizing the C.O.R. = increased ROM, increased
internal/external, decreased scapula notching.
Eccentric = ideal baseplate positioning while allowing the
glenosphere to be position inferiorly and avoid scapular notching. Increases deltoid
tension.
Both options together + multiple humeral body heights allow us
to have only one diameter Glenosphere (38mm).
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Glenosphere Positioning
Baseplate and Screws
Glenoid baseplates made of Ti with Asymmatrix porous coating– 15mm length post (primary cases)– 25mm length post (revision and
bone grafting) length options– Curved back (convex) – anatomic
shape
27mm
22mm
Central Compression Screw – 5.5mm x (20-45mm) length in 5mm
increments– Independent compression screw in various
length adds for central compression of baseplate into glenoid
Peripheral polyaxial locking screws – 4.5mm x (15-55mm) length in 5mm
increments– Anterior and Posterior are compression
screws– Superior and Inferior are compression and
then locked (Variable Angle Locking Screws)
Baseplate and Screws
Reverse Body • Reverse Humeral Body made of Ti with
Asymmatrix porous coating• 142 degree inclination angle
– Decreases scapular notching versus a 155 degree inclination
– Increased glenoid access
• Polished medial calcar to allow for tuberosity and soft tissue suture retention.
• Asymmatrix coating allows for good secondary fixation and allows for all press fit humeral component.
• Morse taper and backup screw for body to stem connection
• 3 body height options – Small (30mm)– Standard (35mm) – Large (40mm)
Humeral insert made of UHMWPe
– Standard - +0mm, +3mm, +6mm, +9mm– Retentive - +0mm, +3mm, +6mm, +9mm
» Retentive option provides more glenosphere coverage providing more stability yet increased chance for scapular notching.
• Humeral Stems made from Ti for press fit applications– 11 sizes (6-16mm) 1mm increments
• Humeral Stems made from CoCr for cemented applications– 5 sizes (6-14mm) 2mm increments
Humeral Poly Liners & Stems
Baseplate Screw Fixation5.5 Central Screw Preparation
4.5 Peripheral Screw Preparation and Locking Caps