Shoulder Joint Replacement Flashcards
What 3 categories are shoulder replacements divided into?
unconstrained (Neer)
semi-constrained (Gristina)
constrained (Michael Reese)
What are prostheses that do not conform to normal joint anatomy known as?
reversed/inverted anatomy designs
Give an example of a reversed prosthesis
cavendish
Name the primary goal and then 2 secondary goals of shoulder replacement surgery
relieve pain
improve ROM
improve function
What factors influence the choice of prosthesis?
quality of soft tissues
strength
stability
function
IF the rotator cuff is intact and functional, what kind of prosthesis will normally be chosen?
unconstrained
If there is little soft tissue support to the shoulder, what type of prosthesis will be chosen?
constrained
What 3 synovial joints make up the shoulder?
glenohumeral
acromioclavicular
sternoclavicular
What other important bone-on-muscle-on-bone articulation is present in the shoulder joint?
scapulothorcic
What is the most important shoulder articulation?
glenohumeral - largest ROM and forces - prosthesis must be able to withstand these
What feature of the glenoid fossa allows the large ROM? What is the downside of this?
shallow nature of the fossa
inherent instability
What 4 muscles make up the rotator cuff?
supraspinatus
infraspinatus
teres minor
subscapularis
What structure must provide support to the shoulder due to the absence of inherent bony support?
rotator cuff
Who designed the original unconstrained prosthesis?
Charles Neer
What rotator cuff function is necessary for an unconstrained prosthesis?
intact and well functioning
What material is used for the glenoid component in the Neer prosthesis?
polyethylene
Name some advantages of the Neer prosthesis
near anatomical design
maximal potential ROM
good predictable pain relief
minimal bone resection
Name one disadvantage of the Neer prosthesis
it is dependent on the quality fo the rotator cuff and deltoid muscles
What risk does total arthroplasty carry with it?
loosening of the glenoid component
How do unconstrained prostheses gain their additional stability?
the glenoid component is HOODED and roofs over the superior aspect of the humeral component, thus resisting the upward shear force produced when the arm is elevated
What is joint stability dependent on in the semi constrained prosthesis?
rotator cuff mechanism primarily
some constraint built into the design
What are the disadvantages of semiconstrained prostheses?
motion is limited compared to unconstrained designs
greater forces are transmitted to the glenoid bone-cement junction which causes more frequent loosening
How are greater forces created at the bone-cement junction of the glenoid in semi constrained prostheses?
forces that act vertically on the hood produce moments which must be counteracted by additional forces at the bone-cement junction
What type of forces are created superiorly and inferiorly in semiconstrained prostheses?
compression superiorly
tension inferiorly
What are the disadvantages of a semicontrained prosthesis in comparison to unconstrained?
restricted ROM
more frequent loosening of the glenoid component
