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
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
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
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
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
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
D. All poly liner and cemented stem
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
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
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%