MCP Joint Replacement

Question 1

Why were early finger replacements not successful?

Answer 1

Migration into the bone
Loosening
Mechanical problems

Question 2

What is the most frequently indicated hand joint replacement?

Answer 2

MCP

Question 3

What are the 2 types of MCP replacement?`

Answer 3

Flexible hinge

Total metacarpophalangeal

Question 4

What is the main indication for MCP replacement?

Answer 4

Pain and deformity associated with RA

Question 5

Other indications for MCP replacement

Answer 5

Impaired hand function secondary to soft tissue imbalance but with minimum discomfort

Question 6

What is the preferred treatment option for younger patients requiring a strong pinch?

Answer 6

Arthrodesis of the index finger

Question 7

What position is the index finger fused at in arthrodesis?

Answer 7

40 degrees of flexion

Question 8

What type of joints are MCP joints?

Answer 8

Condyloid (ovoid head of metacarpal + elliptical cavity of the base of the proximal phalanx

Question 9

What contributes to the stability of the MCP joint?

Answer 9

Joint capsule
Collateral ligaments
Fibrocartilaginous palmar plate
Muscle tendons

Question 10

What planes does the MCP allow motion in?

Answer 10

Flexion-extension
Abduction-adduction
Pronation-supination (small amount)

Question 11

How much flexion does the MCP joint allow?

Answer 11

90 degrees

Question 12

How much does the MCP joint contribute to total finger flexion?

Answer 12

80%

Question 13

Describe the Swanson MCP prosthesis

Answer 13

Designed as an adjunct to resection arthroplasty
Flexible silicone elastomer hinge
Relies on encapsulation to help maintain alignment

Question 14

How is the Swanson MCP prosthesis fixed?

Answer 14

Stems are not fixed (they freely glide within the medullary canals)

Question 15

Why are the stems not fixed in the Swanson MCP prosthesis?

Answer 15

Mor even force transmission

Increased range of motion

Question 16

Why were titanium bone liners (grommets) introduced to the Swanson MCP prosthesis?

Answer 16

To shield the implant from sharp bone edges after high tear rates

Question 17

How are grommets fixed?

Answer 17

Press-fit (interference fit)

Question 18

What are the clinical results of the Swanson flexible hinge prosthesis?

Answer 18

70-80% satisfaction
Active ROM increases only slightly but is shifted to a more functional arc of extension
80% aesthetic improvement
Infections are rare

Question 19

Are fractures an issue in flexible hinge MCP prostheses?

Answer 19

Less than 10%

Even when they occur the prosthesis doesn’t always need replaced and joint often has pain-free motion and remains stable

Question 20

3 examples of total MCP joint prostheses

Answer 20

Steffee
Schultz
Strickland

Question 21

What are total MCP joint prostheses made of?

Answer 21

Metallic component and polyethylene component

Both cemented in medullary canals

Question 22

What problems have been found with total MCP replacements?

Answer 22

Implant fracture
Migration
Loosening

Question 23

Why is there a need for a total MCP joint prosthesis that produces uniformly good results?

Answer 23

Flexible hinge prostheses are not particularly suited to younger patients and those who would wish to perform tasks that place higher demands on the MCP joints