THA

Technique

Cemented cup and femur via posterior approachTHR Cemented Exeter

 

Set up

- on side

- charnley supports posterior on sacrum

- anteriorly on ASIS

- patient slightly tilted backwards

- avoids cup retroversion

 

Posterior Approach

- identify short ER

Uncemented femur

GoalTHR Uncemented

 

Initial press fit

- implant geometry fits the cortical bone in the proximal femur

- good initial mechanical stability

 

Biological fixation for success

- good press fit

- minimal micromotion

- bony or fibrous tissue ingrowth or ongrowth

 

Management

Management Summary

 

Stage 0

 

Natural history mixed

- depends on size of lesion and diagnosis

- treat if becomes asymptomatic

- may benefit from bisphosphonates

 

Stage 1 / Normal X-ray, abnormal MRI

 

Forage: 80% G/E

Bisphosphonates

 

Stage 2 / Abnormal X-ray with cysts and sclerosis

 

A:  As for Stage I

Templating

AimTHR Templating

 

Reproduce the normal anatomical centre of rotation

Restore femoral offset 

Maintain equal leg lengths 

 

Usually template off normal hip

 

Template

 

1. LLD

2. Offset

3. Femoral component

4. Acetabular component

5. Osteotomy / femoral seating

 

Background

IssuesTHR Uncemented

 

Templating

Approach

Fixation

Bearing Surface

Head Size

Offset

 

Indications

 

Disabling hip pain

Severe functional impairment

Failed non operative management

 

Not Indicated 

 

Painless deformity

Bearing Surfaces

Wear

 

The removal of material, with the generation of wear particles under an applied load and in relative motion

 

Tribology is the study of wear and lubrication

 

Wear mechanisms

 

Adhesion

- bonding of the surfaces when pressed together

- may pull away material from the weaker surface

 

Abrasion

- asperities on the harder surface cut and plough 

Protrusio

Definition

 

Migration of the femoral head past the medial wall of the acetabulum / ilioischial line 

 

Centre edge angle > 40o

 

Aetiology

 

Primary 

 

Otto's Disease

- bilateral in one third

- middle aged females

- pain & decreased ROM early 

- coxa vara & OA common

- ? causally related to osteomalacia

Neuromuscular

Categories

 

Decreased tone

- Polio

- Down's syndrome

- spina bifida

 

Increased tone

- cerbral palsy

- Parkinson's

- CVA

 

Polio

 

Rare

- case reports only

 

Down's Syndrome

 

Acetabular dysplasia not uncommon in this group

 

Results

 

DDH

ConceptTHR Dysplasia Subtrochanteric Osteotomy + Mesh Impaction Bone Graft

 

THR in dysplastic hips has a higher failure rate

- due to anatomic abnormalities

- due to generally younger age

 

Aim

 

Restore normal biomechanics and preserve bone stock

 

Issues

 

Soft tissues

Arthrodesis Conversion

Indications

 

Severe LBP 

- most common indication

 

Ipsilateral knee pain

- less beneficial

 

Malposition

- especially abduction

 

Contraindications

 

Absent abductor mechanism

Flail

Active infection

Insufficient bone stock

 

Examination

 

LLD