total knee arthroplasty

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

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

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

 

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

 

Stiffness

 

Incidence

 

10%

 

Requirements

 

70 swing phase

80o climb up stairs

90o climb down stairs + sit down in chair

100o low chair

 

NHx

 

Stiffness usually subsides at 6-8/52

- generally improves out to 3/12

- slow improvement for up to next 9/12

 

Vascular Injury

Arterial injury

 

Incidence

 

0.05%

 

Types

 

1. Thrombosis

- most common scenario

- tourniquet with atherosclerosis

- indirect damage to vessel

- femoral or popliteal

 

2.  Embolisation

- atherosclerosis again

- blue toes syndrome post operatively

 

3.  Vessel transection

 

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 

Prevention

Preoperative

 

Identify high risk groups

- immunocompromised

- diabetes

- RA

- malnutrition

 

Urine screen

- check for and treat UTi

 

Groin, nose, axilla swabs

- for MRSA

- if positive, treat

- need 3 consecutive free swabs

 

3 x chlorhexidine preoperative showers in 8 hours

 

Admit day of surgery

- check skin for lesions