Joint reconstruction Flashcards

1
Q

What are the objectives of disc replacement

A

Relieve back pain from degenerating disc

Provides an alternative to joint fusion - that preserves movement

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2
Q

Design considerations for disc replacement

A

Range of motion

Stresses (compressive, shear, bending, axial)

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3
Q

What are the 4 categories of artificial disks

A

Composite: Metal and UHMWPE sandwich
Mechanical: Material articulating with another
Nucleus: hydraulic component
Elastic: Deformable core

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4
Q

What are the 4 categories describing level of constraint

A

Constrained
Semi-constrained
Unconstrained
Deformable

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5
Q

Describe a composite unconstrained model

A
  • UHMWPE sphere
  • CoCr alloy endplates
  • Increase in flexion-extension and axial rotation compared to intact – excessively large range of motion
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6
Q

What part of the spine are composite unconstrained model used in

A

Lumbar spine

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7
Q

Describe a composite constrained model

A
  • CoCr alloy endplates
  • UHMWPE ball
  • Implant design intentionally restricts range of motion (smaller range of motion than unconstrained)
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8
Q

What part of the spine are composite constrained model used in

A

Cervical & Lumbar

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9
Q

Describe a mechanical semi-constrained model

A
  • CoCr metal-on-metal

* An issue with metal on metal is Metallosis

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10
Q

What part of the spine are mechanical semi-constrained model used in

A

Lumbar

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11
Q

Describe a nucleus/elastic deformable model

A
  • Polyurethane nucleus
  • Titanium alloy shells
  • ‘Press fit’ into spine
  • Takes more of anatomical approach
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12
Q

What part of the spine are nucleus/elastic deformable model used in

A

Cervical

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13
Q

Possible complications of disc replacement (5)

A
Loosening
Fracture
Heterotopic calcification
Adjacent segment pathology
Wear
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14
Q

What are the 2 functional divisions of the ACL

A
Anteromedial bundle (AMB)
Posterolateral bundle (PLB)
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15
Q

What kinds of motion are AMB and PLB responsible

A

AMB –> Prevents excessive anterior translation

PLB –> Controls rotational movement

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16
Q

What causes strain (and thus tear) of ACL

A

Forces on anterior tibia by quadriceps

Knee valgus movements

17
Q

Activities that can lead to ACL rupture

A

Pivoting
Jumping backwards (skipping, gymnasts)
Non-contact deceleration

18
Q

Pros and Cons of Allograft for ligament replacement

A

PRO: Person will not have to donate their own ligament
CON: biomechanical properties may be altered due to sterilisation

19
Q

Pros and Cons of Autograft for ligament replacement

A

PRO: No sterilisation necessary
CON: Donor site instability, Injury during procedure

20
Q

Pros and Cons of Synthetic graft for ligament replacement

A

PRO: High ultimate tensile strength, no donation needed
CON: Endogenous properties difficult to replicate

21
Q

Sites of ligament autograft

A

Patella tendon
Quadriceps tendon
Hamstrings tendon

22
Q

What needs to be done when using tendons to replace ligaments

A

Ligamenterisation - process takes over a year

23
Q

Why do tendons need to be ligamentarised

A

Tendons can onlt take significant load in one direction

24
Q

What is the advantage of replacing both bundles of ACL and not just AMB

A

give a result closer to endogenous ACL

25
Objective of osteotomy
to modify load transmission by changing the alignment of the bone. Some examples
26
Describe pathophysiology of Perthes' disease
Blood supply to femoral head is temporarily disrupted leading to ischaemia and eventual necrosis Dead tissue is replaced with woven bone which is weaker so fails under the loads a normal femoral head is subjected to After years, this heals (re-ossification) but femoral head has a different shape than it normally would
27
What type of Osteotomy is done to treat Perthes' disease
Aim is to increase femoral head coverage by acetabulum Close wedge osteotomy on FEMUR Open wedge osteotomy on PELVIS
28
Effect of Perthes osteotomy on muscles
decreases the moment arm of the abductor muscles which means that a larger force will need to be generated to achieve the same torque/moment so the muscle will be tired
29
What type of Osteotomy is done to treat UNICOMPARTMENTAL osteoarthritis
An OPEN wedge osteotomy to straighten the mechanical axis
30
Which compartment of the knee joint is more likely to suffer from osteoarthritis and why?
Medial | The reaction force from the ground acts on the medial compartment