Orthopaedics Flashcards
What are the indications for joint replacement?
- inflammatory disease (RA)
- Trauma (fracture of neck of femur/humerus)
- Tumour
- Vascular disease (AVN)
- Revision of previously failed/worn out joint replacement
- Degenerative disease (OA)
What are the different types of joint replacements?
- cemented (acrylic glue that holds prosthesis in place - i.e. affixes bone to prosthesis)
- uses polymethylmethacrylate (PMMA) - uncemented (no glue - allows bone to grow and adhere on to prosthesis)
- hybrid = cemented femoral stem and acetabulum is an uncemented cup (can be vice versa)
How can an uncemented prosthesis encourage bone growth?
Rough surface covered with porous/hydroxyapatite covering
it encourages osteocytes and osteoblasts to move in
When might cemented and uncemented prostheses be used?
Cemented: obese, dysplastic (hips), osteoporosis
- can weight bear immediately
Uncemented: young and more active –> less aseptic loosening, and reduced incidence of fat embolism
- 4-6 weeks of non-weight-bearing
What biomaterial used in a prosthesis has the least wear rate?
Ceramic on ceramic
Features:
- immunogenic, inert (fewer infections)
- small rate of failure (can fracture and smash if overstressed)
What other biomaterials can be used in a prosthesis?
- metal on metal
- ceramic in cross-linked polyethylene
- oxinium in cross-linked polyethylene
- metal in cross-linked polyethylene
In what situations is spinal decompression surgery performed?
- spinal stenosis
- damage to IV disc
- fractured vertebra
- tumours
What is spinal fusion also called and what is it?
Arthrodesis
where 2+ vertebrae are joined together with a section of bone to stabilise and strengthen the vertebral column
Which tendons are transferred in the upper limb in radial nerve palsy? (what tendons do they replace, what action do they perform etc)
- Pronator teres takes over for extensor carpi radialis brevis –> for wrist extension
- Flexor carpi ulnaris takes over for extensor digitorum communis –> for finger MCP extension
- Palmaris longus rerouted to extensor pollicus longus –> thumb extension
*anterior compartment muscles + innervation (ulnar or median nerve) and use them to replace extensor muscles
Could also do:
- PT –> ECRL + ECRB
- FDIII –> EDC
- FDSIV –> extensor indicis + EPL
- FCR –> APL + EPB
Describe tendon lengthening in terms of the Achilles tendon.
when plantarflexors are stronger than dorsiflexors we end up toe-walking
- achilles tendon needs to be extended
- y-shape incision and extend by 1cm and stitch back up
- will ensure heel stays on the ground and it gives better movement
How can an ACL be reconstructed? (what is the name of the surgery, what structure(s) is/are used)
- usually perform a bone-ligament-bone graft (patella-ligament-tibia)
- semitendinosus is most often used for ACL reconstruction
- stitch semitendinosus muscle to semimembranosus
- use the tendon from semitendinosus as the main part of the graft (new ACL)
This kind of operation tends to heal faster than other methods
What muscles can be used in free muscle transfer? (give examples of the muscle and what it would replace)
Use any muscle that is expendable, under voluntary control and is innervated Examples: Gracilis (with skin) - deltoid reconstruction - elbow flexion and extension - finger flexion and extension can also use rectus femoris
What are the different types of poor fracture healing?
- delayed: failure to consolidate within 1.5x the normal expected time
- mal-union: misalignment of proximal and distal fragment, leading to biomechanical deformity (rotation, angulation, shortening, translocation)
- non-union: failure to consolidate with 2x normal expected time
- can be atrophic or hypertrophic depending on blood supply and degree of stability
- no bony callus forming
Why are osteotomies performed?
To realign the bone
Why is distraction osteogenesis performed?
for bone lengthening
progressive correction with the use of external fixation
can lengthen by about 1mm a day
