Chronic, non metabolic bone disorder
Characterised by increased bone resorption, bone formation and remodelling
Rare < 40
1 – 3 % population over 60
M > F
Unknown
Paramyxovirus implicated
- measles
- RSV
- canine distemper virus
Electron Microscope
1. Contained Metaphyseal Defect
2. Damaged Metaphyseal
A. One Condyle
B. Both Condyles
3. Deficient Metaphysis +/- collaterals +/- extensor mechanism
Attempt to reduce outliers in all 3 planes of the knee
- improve alignment
- theoretically improve survival and outcomes
Image based
Pre-op CT
- uncommon
- resource heavy
| Medial Structures | Lateral Structures | |
| Tight in Extension |
Posterior MCL Semimembranosus Posterior capsule Pes Anserinus |
ITB Conformity Materials Fixation GenderConformity
Definition
Geometric measure of the closeness of the fit of the knee articulation
Concepts
The ideal TKA maximises articular conformity while minimising axial constraint
Highly conforming / Fully congruent - constant sagittal femoral radius - large contact areas - theoretical limitation of flexion to 120o due to posterior impingement of the tibial component ConstraintPhilosophy
Need the least amount of constraint necessary to obtain sufficient stability
Increasing constraint
Advantages - increase stability
Disadvantage - increase stress at implant host interface
3 Types
1. Unconstrained
A. Posterior cruciate retaining Patella ResurfacingOptions
1. Always resurface 2. Never resurface 3. Selectively resurface
Decision Making
Controversial - literature divided on issue
Historically - poor outcomes due to poor implant design - now improved designs - non resurfacing also improved due to better design and improved techniques in regard to tracking and rotation
PatellaProblems
Instability / Maltracking Fracture Loosening or failure of component Patella Clunk Syndrome Extensor Mechanism Rupture
Incidence
PFJ complications 5%
PFJ Instability / Maltracking
Effect
Catastrophic wear Component loosening Pain FracturesIntraoperative Fractures
1. Shaft fracture from IM rod
2. Posterior condylar fracture
Management - assess stability - ORIF if needed
Wound Problems
|
Incidence