Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Surgical washout and antimicrobial principles
Musculoskeletal medicine and orthopaedics · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Source control and sepsis treatment proceed together
Pus, necrotic tissue, infected implants and closed-space pressure remain biologically active despite antibiotics; delayed or incomplete washout permits cartilage loss, bacteraemia, tissue death and repeated operations.
Action: Resuscitate and culture without harmful delay, start intravenous treatment immediately in sepsis, mobilise the appropriate surgical and anaesthetic team, expose every involved compartment, obtain multiple separately instrumented deep samples before irrigation, excise non-viable tissue, drain thoroughly and define the re-look and antibiotic review before leaving theatre.
Purpose and principles
Understand washout as structured source control rather than irrigation alone, preserve deep microbiology, match surgical access to anatomy, and connect empirical, directed and follow-up antimicrobial decisions to operative findings.
The indication for surgical washout is an anatomical source that medication cannot reliably clear: purulent joint, abscess, necrotic fascia or muscle, infected devitalised bone, contaminated dead space or implant-associated biofilm requiring mechanical disruption. Define the target and urgency before theatre. A septic native joint differs from chronic fracture infection, and necrotising disease requires excision rather than lavage. Review imaging, implants, perfusion, stability and soft-tissue cover and involve plastic, vascular, spinal or arthroplasty expertise before an incomplete first operation commits future options.
Resuscitation and source control are parallel. Take blood cultures and correct immediately reversible physiological threats. A stable patient can remain off antibiotics until aspiration or operative samples are secured. A septic patient receives parenteral therapy after rapidly obtainable blood cultures, without waiting for the operating list. Record every prior antibiotic, allergy, organ dysfunction, anticoagulant and implanted device. Agree blood availability, tourniquet strategy, positioning, imaging and postoperative level of care with anaesthesia.
Practice
Two practice questions
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Question 1 of 2
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Musculoskeletal medicine and orthopaedicsOriginal SBA
Deep-sampling standard
During planned operative debridement of a stable patient with suspected fracture-related infection, which sampling method best preserves reliable microbiological interpretation?
Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Plan samples before skin preparation. Aspirate fluid before incision or irrigation where feasible. In implant or fracture-related infection, take five deep microbiology samples from independent representative sites, each with a fresh sterile instrument and no-touch technique; take two histology specimens in chronic or uncertain infection. Label anatomy precisely rather than numbering unexplained pots. Notify microbiology of prior therapy, implants and suspected fastidious organisms. Superficial swabs, drain fluid and pooled tissues cannot substitute for disciplined deep sampling.
Exposure must reach the disease. Break loculations, irrigate all communicating spaces and remove pus, fibrin, foreign material and clearly non-viable tissue while preserving essential viable structures. Arthroscopy gives broad joint visualisation with less soft-tissue injury in many native large joints; open surgery may be necessary for advanced adhesions, inaccessible recesses, damaged tissue, bone involvement or failed arthroscopy. Necrotising infection requires systematic fascial and muscle assessment and radical debridement, not high-volume irrigation through a small portal.
Implant decisions depend on stability, union, biofilm maturity, symptom duration, organism and tissue. Retention may be reasonable only when fixation is essential and stable, debridement is sufficiently radical and effective antimicrobial treatment exists. Exchange accessible modular components during an indicated DAIR. Remove unnecessary or loose metalwork and restore fracture stability through a planned construct. Debride sequestrum and manage residual cavities with viable coverage; local antimicrobial carriers can support but never replace systemic therapy and perfusion.
At the end of surgery, record what was found, which tissues were excised, implant status, sample map, residual uncertainty, irrigation, drains, closure and planned re-look. Leave infected necrotising wounds open; other wounds close only when viable tissue and source control permit. A drain is not proof of clearance. Decide who will inspect the wound and when. Worsening physiology, recurrent effusion, persistent drainage or an unfavourable CRP and pain trajectory triggers immediate reconsideration of repeat exploration.
Empirical antibiotics start after samples unless instability required earlier administration. Use the full local source-specific regimen rather than a vague broad-spectrum label, and review at 48 hours as preliminary cultures emerge. Narrow to the pathogen and operation, document route and stop or review date, and involve infection specialists for prolonged or biofilm-active combinations. Oral therapy can be appropriate when highly bioavailable, active and absorbable; intravenous access is not itself evidence of superior source control.
Postoperative care protects the surgical result. Track observations, pain, perfusion, neurological status, wound, drains and blood-culture clearance. Adjust renal, hepatic and marrow monitoring to the chosen drugs and reconcile interactions. State weight-bearing and movement restrictions and begin rehabilitation early enough to prevent stiffness and deconditioning. Explain recurrence and toxicity signs. At discharge, make culture ownership explicit so late-growing organisms and susceptibility changes trigger action rather than disappearing after the patient leaves hospital.
Key points
Washout is a source-control package: adequate exposure, decompression, drainage, excision of non-viable tissue, representative sampling, dead-space management and a documented closure or re-look plan.
Stable patients should provide blood and deep samples before antibiotics. Septic patients receive intravenous treatment after rapidly obtainable blood cultures even if theatre or aspiration is delayed.
Take fluid before irrigation and multiple deep tissue samples with a fresh sterile instrument for each; five microbiology specimens are the BOASt standard for fracture-related and peri-prosthetic infection.
Choose arthroscopic, open or image-guided access from joint, loculation, tissue state, implants, surgeon expertise and the need to debride bone or exchange components.
Do not call a small incision and irrigation definitive when necrotic fascia, sequestrum, infected non-union or mature implant biofilm remains outside the field.
Start empirical broad treatment after samples, review at 48 hours with preliminary culture results and narrow to organism, allergies, renal function, surgical strategy and local resistance.
Failure to improve prompts repeat examination, culture review and imaging and often repeat washout; simply extending or broadening antibiotics does not sterilise retained pus or avascular tissue.
Indications, selection and cautions
Drainable closed space
Purulent joint or loculated abscess creates bacterial burden and pressure that systemic drugs alone may not overcome.
Debridement disease
Necrotic fascia, muscle or bone requires excision to viable tissue; irrigation of dead material is not source control.
Implant biofilm problem
Stable essential fixation may sometimes remain, whereas loose, unnecessary or mature-biofilm metalwork changes the reconstructive strategy.
Incomplete first operation
Persistent pain, shock, drainage or bacteraemia after washout suggests retained anatomy or another source rather than simply an insufficient duration.
Soft-tissue dependency
Exposed bone or metalwork cannot heal without perfusion and durable cover, making plastics and vascular planning part of infection surgery.
Culture-limited treatment
Premature antibiotics, pooled specimens and superficial swabs create uncertain microbiology and unnecessarily broad prolonged therapy.
Red flags requiring action
Shock, rising lactate, altered consciousness or progressive organ dysfunction requires immediate sepsis antibiotics and emergency source control rather than prolonged diagnostic optimisation.
Necrotising features, compartment pressure, neurovascular compromise, rapidly spreading tissue change or gas demand radical exploration beyond a limited washout.
Assessment before treatment
01Preoperative blood culturesFirst step
Why
Identify systemic organisms before antibiotics when rapidly possible.
Interpretation and limitations
Positive cultures guide treatment and source search; persistent bacteraemia after washout indicates ongoing burden or another focus.
02Pre-irrigation fluid
Why
Capture undiluted pus or synovial material for microscopy and culture.
Interpretation and limitations
Take first with sterile technique; negative fluid culture does not exclude infected tissue, especially after prior antibiotics.
03Five deep microbiology specimens
Why
Sample independent implant, bone or tissue sites.
Interpretation and limitations
Use separate instruments and no-touch technique; concordant organisms carry greater meaning than one pooled or superficial specimen.
04Two histology specimens
Why
Demonstrate tissue infection and exclude mimics in chronic or uncertain disease.
Interpretation and limitations
Send representative interface or bone and alert pathology if tumour, crystal or unusual organisms are possible.
05Imaging for residual anatomy
Why
Map abscess, bone involvement, implant stability and soft-tissue extent.
Treatment approach
01EmergencyResuscitate and operateFirst stepSepsis, necrotising infection, neurovascular threat or rapidly destructive closed-space infection is present.+
1Take rapid blood cultures, start intravenous therapy and mobilise theatre and critical care concurrently.
2Expose the entire threatened anatomy, obtain deep samples and drain or excise all non-viable infected tissue.
3Restore perfusion, decompress compartments and stabilise unsafe bone with relevant specialist teams.
4Leave a documented re-look threshold and treat deterioration as incomplete source control.
02PlannedProtect microbiology and reconstructionThe patient is stable and a deep infection operation can be deliberately designed.+
1Withhold empirical antibiotics, review imaging, implants, union, perfusion and soft-tissue cover and agree the surgical endpoint.
Regimens, contraindications and interactions
Covers likely organisms during early culture incubation while surgery reduces bacterial burden and removes avascular tissue.
Empirical treatment after operative sampling
Immediately after pre-irrigation fluid and deep tissue specimens are secured, give the complete adult agent, route, dose and interval from the trust's anatomical infection protocol; review at 48 hours against preliminary cultures and the operation performed.
Account for allergy, renal and liver function, previous isolates, healthcare exposure and local resistance; do not conceal poor source control with escalating breadth, and record exact timing relative to samples.
Completes eradication or a documented suppression goal after microbiology and source anatomy are known.
Organism-directed continuation
Prescribe the narrowest active regimen with exact route, frequency, monitoring and stop or review date agreed by infection specialists, using a reliable oral agent when appropriate and linking duration to retained implants, bone involvement, drainage and response.
Review absorption, pregnancy, renal and hepatic adjustment, marrow toxicity, QT risk and drug interactions; biofilm-active combinations require specific indication and must not be used as unsupported monotherapy.
Complications, monitoring and follow-up
Record postoperative observations, perfusion, neurological findings, pain and urine output through the source-control response.
Inspect wounds and drains for ongoing purulence, necrosis, dehiscence and tissue viability at a specified time.
Track blood-culture clearance, CRP direction and all deep culture and histology results with named ownership.
Monitor renal, hepatic and marrow indices and agent-specific interactions throughout antimicrobial treatment.
Reassess implant stability, union, dead space and soft-tissue coverage rather than following the incision alone.
Measure range, strength, loading, mobility and return-to-function goals through rehabilitation.
Special situations
Irrigation volume is not adequacy
Litres of fluid cannot compensate for missed loculations, necrotic tissue, sequestrum or an unstable infected implant.
Samples need independence
Five pots are meaningful only when each represents a distinct site obtained with a fresh instrument before cross-contamination.
A drain is not source control
Tubing removes future fluid but cannot debride biofilm, dead fascia or an inaccessible abscess recess.
Retention is an active choice
Leaving metalwork requires documented stability, timing, tissue and antimicrobial logic rather than fear of reconstruction.
Failure points back to anatomy
When appropriate drugs do not improve physiology and pain, retained source is more urgent than a longer calendar course.
Culture follow-up is a clinical task
Late-growing organisms and final susceptibilities require an accountable clinician after discharge.
Common pitfalls
01
Describing limited lavage as definitive treatment when necrotic tissue or biofilm remains.
02
Taking one swab after irrigation instead of independent pre-treatment deep specimens.
03
Delaying antibiotics in sepsis to preserve perfect theatre cultures.
04
Starting antibiotics in a stable planned case before obtainable sampling.
05
Broadening treatment for non-response without reassessing drainage, perfusion and implants.
06
Discharging without assigning ownership of cultures, wound review and antimicrobial monitoring.
Document postoperative weight-bearing, wound and drain plan, thrombosis prevention, analgesia, rehabilitation, laboratory monitoring and the named team responsible for culture follow-up.
Persistent fever, pain, CRP rise, positive blood cultures or ongoing drainage after surgery indicates inadequate source control, another focus or ineffective therapy until investigated.
A prosthesis, fracture fixation, unstable bone, poor perfusion or major soft-tissue defect changes the operation and requires implant, vascular and reconstructive expertise rather than isolated lavage.
Interpretation and limitations
Use modality for the question, but do not postpone emergency decompression or debridement for non-essential imaging.
06Serial clinical and CRP response
Why
Detect failure after source control.
Interpretation and limitations
Trend pain, function, fever and wound alongside CRP; an isolated value neither proves clearance nor mandates reoperation.
07Culture and susceptibility review
Why
Convert empirical therapy into the narrowest effective plan.
Interpretation and limitations
Review at 48 hours and again at final results, reconciling contaminants, separate sites, histology and the retained anatomy.
2
Take pre-irrigation fluid, five separate deep cultures and indicated histology before antimicrobials.
3Debride to viable tissue, manage dead space, implant stability and coverage and document any retained risk.
4Start empirical therapy after samples and review at 48 hours with preliminary culture results.
03FailureReturn to anatomy before escalationEscalationClinical, wound, inflammatory or bloodstream response is inadequate after washout.+
1Re-examine the whole patient and verify culture, dose, perfusion, drainage, implant and wound findings.
2Image for retained or new collections only when it does not delay necessary re-exploration.
3Repeat washout or radical debridement and obtain new deep specimens when residual burden is likely.
4Revise antimicrobials from new source evidence and restore rehabilitation once control is demonstrated.