Shoulder Joint Replacement

Question 1

What 3 categories are shoulder replacements divided into?

Answer 1

unconstrained (Neer)
semi-constrained (Gristina)
constrained (Michael Reese)

Question 2

What are prostheses that do not conform to normal joint anatomy known as?

Answer 2

reversed/inverted anatomy designs

Question 3

Give an example of a reversed prosthesis

Answer 3

cavendish

Question 4

Name the primary goal and then 2 secondary goals of shoulder replacement surgery

Answer 4

relieve pain

improve ROM
improve function

Question 5

What factors influence the choice of prosthesis?

Answer 5

quality of soft tissues
strength
stability
function

Question 6

IF the rotator cuff is intact and functional, what kind of prosthesis will normally be chosen?

Answer 6

unconstrained

Question 7

If there is little soft tissue support to the shoulder, what type of prosthesis will be chosen?

Answer 7

constrained

Question 8

What 3 synovial joints make up the shoulder?

Answer 8

glenohumeral
acromioclavicular
sternoclavicular

Question 9

What other important bone-on-muscle-on-bone articulation is present in the shoulder joint?

Answer 9

scapulothorcic

Question 10

What is the most important shoulder articulation?

Answer 10

glenohumeral - largest ROM and forces - prosthesis must be able to withstand these

Question 11

What feature of the glenoid fossa allows the large ROM? What is the downside of this?

Answer 11

shallow nature of the fossa

inherent instability

Question 12

What 4 muscles make up the rotator cuff?

Answer 12

supraspinatus
infraspinatus
teres minor
subscapularis

Question 13

What structure must provide support to the shoulder due to the absence of inherent bony support?

Answer 13

rotator cuff

Question 14

Who designed the original unconstrained prosthesis?

Answer 14

Charles Neer

Question 15

What rotator cuff function is necessary for an unconstrained prosthesis?

Answer 15

intact and well functioning

Question 16

What material is used for the glenoid component in the Neer prosthesis?

Answer 16

polyethylene

Question 17

Name some advantages of the Neer prosthesis

Answer 17

near anatomical design
maximal potential ROM
good predictable pain relief
minimal bone resection

Question 18

Name one disadvantage of the Neer prosthesis

Answer 18

it is dependent on the quality fo the rotator cuff and deltoid muscles

Question 19

What risk does total arthroplasty carry with it?

Answer 19

loosening of the glenoid component

Question 20

How do unconstrained prostheses gain their additional stability?

Answer 20

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

Question 21

What is joint stability dependent on in the semi constrained prosthesis?

Answer 21

rotator cuff mechanism primarily

some constraint built into the design

Question 22

What are the disadvantages of semiconstrained prostheses?

Answer 22

motion is limited compared to unconstrained designs

greater forces are transmitted to the glenoid bone-cement junction which causes more frequent loosening

Question 23

How are greater forces created at the bone-cement junction of the glenoid in semi constrained prostheses?

Answer 23

forces that act vertically on the hood produce moments which must be counteracted by additional forces at the bone-cement junction

Question 24

What type of forces are created superiorly and inferiorly in semiconstrained prostheses?

Answer 24

compression superiorly

tension inferiorly

Question 25

What are the disadvantages of a semicontrained prosthesis in comparison to unconstrained?

Answer 25

restricted ROM

more frequent loosening of the glenoid component