TKA

Paget's Disease

Definition

 

Chronic, non metabolic bone disorder

Characterised by increased bone resorption, bone formation and remodelling

 

Epidemiology

 

Rare < 40

1 – 3 % population over 60

M > F

 

Aetiology

 

Unknown

 

Paramyxovirus implicated

- measles

- RSV

- canine distemper virus

 

Electron Microscope

Management Bone Defects

AORI / Andersen Orthopedic Research Institute

 

T Tibial  F Femoral

 

1.  Contained Metaphyseal Defect

 

2.  Damaged Metaphyseal

A.  One Condyle

B.  Both Condyles

 

3.  Deficient Metaphysis +/- collaterals +/- extensor mechanism

 

1.  Contained Metaphyseal defect 

 

Navigation

Aim

 

Attempt to reduce outliers in all 3 planes of the knee

- improve alignment

- theoretically improve survival and outcomes

 

TKR Valgus Femoral Implant Non Navigated

 

Types

 

Image based

 

Pre-op CT

- uncommon

- resource heavy

 

Balancing

Coronal Plane Balancing / Varus Valgus

 

Whiteside's Manual

 

  Medial Structures Lateral Structures
Tight in Extension

Posterior MCL

Semimembranosus

Posterior capsule

Pes Anserinus

ITB

Conformity Materials Fixation Gender

Conformity

 

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

Constraint

Philosophy

 

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 Resurfacing

Options

 

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

 

Patella

Problems

 

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

Fractures

Intraoperative Fractures

 

1.  Shaft fracture from IM rod

 

TKR Femoral Shaft Fracture IM Rod

 

2.  Posterior condylar fracture

 

Management

- assess stability

- ORIF if needed

 

Wound Problems

TKR Wound ComplicationIncidence

 

10 -15%

 

Include

- marginal necrosis

- wound slough

- sinus tract formation

- dehiscence

- haematoma

- oozing knee wound

 

Blood supply

 

Anterior knee has no muscles to supply vessels directly