Implant technology - unit 5 deck 4 Flashcards
what are examples of a total MCP joint replacements and how are they designed
e.g. Steffee, Schultz, Strickland
- these all incorporate a metallic component that articulates with a polyethylene component
- both components are cemented in to the medullary canals
what are the problem associated with MCP total joint replacements
- implant fracture
- migration
- loosening
total MCP joint replacements do not yet provide consistent results compared to the flexible hinge replacements, why is there need for the development of one which does?
As flexible hinge replacements are not suited to younger patients and those who would wish to perform manual tasks that place higher demands on the MCP joints.
what is the main indication for interphalangeal (IP) joint replacement
pain and deformity associated with RA, degenerative arthritis and post-traumatic arthritis
Why is implant arthroplasty of the distal IP joint rarely indicated ?
because this joint contributes far less to the overall finger motion
what is preferred procedure for DIP joints
arthrodesis as more reliable procedure and results in only min functional deficit
what are the 2 types of IP joint replacement and describe their design
- flexible hinge
- total interphalangeal
[actual protheses are same as those used for MCP joints but have smaller dimensions]
what problems does total IP joint replacements face
same problems as MCP joint replacements
[implant fracture, migration and loosening]
Describe the proximal and distal IP joints
They are bicondyloid joints - formed by the two condyles of the more proximal phalanx and the corresponding cavities of the more distal phalanx.
They are stabilised by the bony articulation itself and the surrounding soft tissues (joint capsule, collateral ligaments, the fibrocartilaginous palmar plate and muscle tendons). [same as the MCP]
What movements is permitted by the IP joints ?
- Flexion-extension - mainly
- Small degree of rotation and translation
What is the ROM of flexion provided by the PIP and DIP joints
[this occurs in sagittal plane cause its Flexion]
PIP = 0-110º
DIP = 0-90º
Why is preservation of the PIP more crucial than the DIP?
- because the PIP contributes around 85% of the IP motion
- The DIP only 15%
what is the success rate for flexible hinge prostheses in PIP joints and expected ROM
- PIP joints have satisfactory pain relief in 98% of cases
- 40-60 degrees ROM expected
0.5% infection rate [rare]
5% fracture rate
Are infections a major problem with flexible hinge hand joint replacements?
No - rates are < 1%
what is the name of the highly successful finger joint replacement
Swanson flexible hinge prosthesis
