disadvantages

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

 

Background

AimUKA Oxford AP

 

UKA is intended to be load sharing

- correct to neutral or slight varus

 

HTO is a load-shifting / load-sparing procedure

- over correct into valgus

 

UKA v TKR

 

Advantages UKA

 

1.  Rapid rehabilation

 

Offset

Definition

 

The perpendicular distance from the centre of the femoral head to the long axis of the femur

 

Harris 1992

- aim for supra-physiologic offset 

- avoid making offset less than original at all costs & makes longer if possible

 

Soft tissue balancing equals restoring femoral offset

 

Effect of short offset

 

1.  Abductor lurch / Trendelenburg gait

Resurfacing

ConceptBirmingham Hip Resurfacing

 

Femur

- removal of femoral head cartilage

- resurfacing with metal

- cemented / uncemented

 

Acetabulum

- standard technique

 

Bearing surface

- metal on metal

 

Indications

 

Relatively young man (40 - 50)

OA

Arthrodesis

IndicationsHip Fusion

 

Young adult 

- 16 - 30 years old

- monoarticular disease

- heavy demand 

 

Exhausted options of osteotomy

- risk of THA failure  / multiple revision surgeries considered too high

 

Aims of arthrodesis

 

Maximise bony contact

Minimise shortening