Infection

Risk factors

 

Patient 

 

Advanced age

Immunosuppression - steroids / Rheumatoid / DM

Malnutrition - Lymphocyte count / Transferrin / Albumin

Vascular disease

Obesity

Poor skin i.e. psoriasis

Previous infection in joint

Infection elsewhere - i.e. UTi

Prolonged hospital admission

Revision surgery

 

Operative Factors

 

Preoperative

- preoperative wash

- preoperative shave

- admission day of surgery to clean ward

- groin, nasal, axilla swabs clear

- clear urine (MCS preop)

- no skin breaks

 

Operative Period

- laminar flow

- minimal theatre traffic

- IV Abx on induction

- shields

- alcoholic prep

- prep drapes

- short procedure duration

- care of soft tissues

- ABx cement

- wound closure / drains / hemostasis

 

Postoperative Period

- wound haematoma & drainage

- skin necrosis

- post operative ABx

- management remote infections i.e. UTI

- care with dental procedures

 

Incidence

 

Current rate 0.27 - 2 % 

 

Increased risk with high-risk patients (2%)

- immuno-compromised

- recurrent bacteraemia

- revision > 2%

- RA

 

Microbiology

 

S. epidermis most common with S. aureus second

- together make up two thirds of all infections

 

MRSA increasing in prevalence

Also vancomycin resistant S. aureus

 

Also

- streptococcus

- S. capitus

- pseudomonas

- coliforms

- anaerobes

- mixed 1/4

 

Symptoms

 

Usually worsening hip pain

- often minimal constitutional symptoms

 

X-ray

 

Progressive / rapid lysis / bone loss

May be normal appearing xray

 

Infected THR progressive bone loss and lysis

 

Investigations

 

For full details, please see Investigation of Pain in THR Complications section

 

Ultrasound

 

Fluid collection about hip

 

Bloods

 

CRP > 10 and ESR > 30 very suspicious

 

Bone scan

 

Reveal increased uptake about both components

- blood flow, blood pool and delayed uptake phases

- more than 12/12 post implantation

 

Specificity increased by WC scan

 

Aspiration

 

Under II control

- off antibiotics

- confirm infection

 

THR Aspiration

 

Pathology

 

1.  Prosthesis in bone

- difficult for antibiotics to access

- poor blood supply

- similar to osteomyelitis

 

2.  Glycocalyx 

 

Bacteria have two forms

A.  Planktonic form 

- individual free floating cells

B.  Sessile form 

- exist within biofilm of glycocalyx

- 500x more resistant than planktonic form

 

Glycocalyx is a slime layer of polysaccharides produced by bacteria 

- protective barrier against antimicrobial and host defences

- helps bacteria to exist and survive on synthetic substances

- biofilm requires minimum time to form

- infection can be irradicated by Abx while still in planktonic phase but not once form biofilm

 

3.  Prosthesis Surface Properties

 

CO-Cr more susceptible to infection than titanium

- may be related to faster osseointegration by titanium

 

Polished surfaces less susceptible

- smaller surface area for bacteria to adhere

- shorter distance for host cell to travel

 

Classification Gustilo 1993

 

1.  Early post-operative

- < 1/12

- febrile patient

- red swollen discharging wound

 

2.  Late post-operative

- indolent (low virulent)

- > 1/12

 

Typically

- well patient

- healed wound

- worsening of pain

- never pain-free interval

 

3.  Acute haematogenous

- antecedent bacteraemia

- can occur several years after surgery

 

Typically

- well patient

- previously well functioning hip

- UTi or other source of infection

- hip now very painful

 

4. Positive intra-operative culture

- presumptive diagnosis aseptic loosening

- intra-operative m/c/s comes back positive (2 out of 5)

- treat with 6 weeks Abx -> success rate 90% 

 

Management

 

Goals

 

Eradicate infection

Relieve pain

Restore function

 

Options

 

1.  ABx suppression

2.  Debridement and prosthesis retention

3.  One stage revision

4.  Two stage revision

5.  Three stage revision

6.  Resection arthroplasty

 

1. Antibiotic Suppression

 

Indications

 

1.  Gustillo Type 4 

- 90% success

 

2.  Elderly and frail

 

Require

 

Known sensitive organism

Stable prosthesis

Tolerable oral Abx

 

Treatment

 

Indefinite

- 50% retention of prosthesis at 3 years 

 

2. Debridement with Retention THR

 

Indications

 

Time

- symptoms < 4/52

 

Stability

- well fixed prosthesis

 

Microbe

- known sensitive organism

 

Host

- Cierny A / B / C

 

Treatment

 

No Abx until

- swab and tissue for M/C/S

- or after positive blood culture

 

Operation

 

Excision of all necrotic and infected tissue

- ensure implant well fixed

- exchange liner (if uncemented)

- wash +++

- monofilament nylon sutures

- drain

 

IV Abx 6/52

 

Vanco / genta initially until swabs available

- ID consult

 

Results

 

1.  Early post-op infection in cemented well fixed THR

- success = 75% 

 

2.  Early post- op infection in uncemented 

- worse results

- due to lack of cement obstruction

- required 2 stage revision if no bone ingrowth

 

3.  Acute haematogenous

- only 50% success 

- often immunocompromised

 

4.  Chronic late

- poor results 

- window of opportunity lost

 

3. One-Stage Revision

 

Infected THR Pre One stage revisionInfected THR Post One Stage Revision

 

Concept

 

Controversial

- remove prosthesis, debride and replace at single sitting

- lower success rate than two stage

- usually indicated in older, more frail patient

- meticulous debridement critical

- treat infection like cancer

 

Indications

 

Timing

- late onset

 

Host

- healthy host

 

Microbe

- sensitive organisms (gm+)

 

Stability

- no sinuses / good wound

- adequate bone stock

 

Technique

 

Debridement all necrotic and infected tissue

- removal of implants and all cement

- aided by extended trochanteric osteotomy

- wash +++

- re-drape, new instruments

 

Reimplant cemented polished femur and all poly cup

- must use ABx PMMA

- already has tobramycin in it

- add powder form vancomycin 

- 2-3 gram in each packet of cement

- each vanco vial is 0.5g

- femur and acetabulum

 

Can implant poly liner from uncemented acetabulum only

- more ABx cement can be impregnated

- large head for stability

 

Post operative

- IV Ab's 6/52

 

Antibiotics must be

- thermostable (excludes tetracycline & chloramphenicol)

- powder form (not genta)

- low allergenic potential

- elute from the cement

- effective against the infecting organism

- Palacos better as higher surface porosity

 

Results

 

80% long term survival

 

4. Two-Stage Revision

 

Gold Standard

 

Indications

 

Chronic late

Acute haematogenous

 

Advantages

 

Improved success rate compared with single stage

- success 90% with ABx cement

- 2 opportunities for debridement

 

Disadvantages

 

1.  2 procedures required

- difficult for patient between stages

 

2.  Revision surgery more difficult

- scar formation 

- shortening

- distortion of anatomy

 

3.  Increased cost / Longer time

 

First stage

 

Complete debridement

- removal all implants and cement

- meticulous debridement necrotic an infected soft tissue

- insert spacer

 

A.  Ball of ABx Cement

 

Infected THR Cement Ball

 

Advantage

- leeches ABx

- maintain space for revison hip

 

Disadvantage

- very uncomfortable

- o mobility benefit to patient

- can cause bony erosion

 

B.  Abx cement in mould

 

Infected THR Cement Spacer Fracture

 

Disadvantage

- poor function

- fractures / breaks

- painful

- difficult to mobilise

- can cause further bone loss

 

C.  Company produced cement spacer

 

Prostalac

- metal spine

- can dislocate / cause bone loss / cause femur fracture

 

Infected THR Prostalac SpacerInfected THR Dislocated ProstalacProstalac Femur Fracture

 

D.  All poly liner and cemented stem

 

Infected THR Kiwi Hip Spacer

 

Concept of the "kiwi" hip

- +++ Abx cement

- cheap polished femur loosely cemented in

- uncemented poly liner to increase cement load in acetabulum

 

Advantage

- stable construct

- patient can mobilise

- no rush to revise

 

Disadvantage

- cost

 

E.  Antibiotic Coated Nail

 

Infected THR NailAntibiotic Coated Nail

 

Second Stage

 

Timing

- Abx minimum 6/52

- at least 2 - 4 weeks off ABx

- consider hip aspiration

- normal CRP / ESR

- intra-operative FFS at time of surgery

 

5. Three stage Revision

 

A.  Remove implants - 4-6/52 Abx

B.  Bone graft defects - 3-12/12

C.  Revise components when graft incorporated

 

6. Resection Arthroplasty (Girdlestone)

 

Described in 1928 for TB

 

Infected THR GIrdlestones

 

Indications

- medically unfit for further revision surgery

- refusal for further revision surgery

- sepsis control / virulent bug

- unrevisable due to bone loss

- unlikely to become mobile

 

Advantage

 

Effective control of infection (95%)

 

Disadvantage

 

Poor function

- pain

- limp

- require walking aid

- 5cm average LLD

- increased energy expenditure 250%

 

Leaves pateint with nearly useless pseudoarthrosis

- weight bearing almost impossible

- severe shortening

- consider only as last resort

 

Post operative

- used to recommend 6/52 traction

- makes no difference

 

7. Amputation

 

Technique

- hip disarticulation

 

Indications

 

Life-threatening infection

Severe loss of ST & bone stock

Vascular injury

 

Incidence

 

Performed in 0.1%