Antibiotics and Infection

Introduction

The incidence of post-operative wound complications in elective orthopaedic foot and ankle (F&A) surgery is low with reported rates between 0.07% and 6.5%. Rates of infection for ankle arthroplasty range from 1.1% – 8.9%; this is higher than reported rates for hip/knee replacement. Post-operative wound complications with deep infection may result in malunions, non-unions, amputation, sepsis and increased mortality.

 

Risk Factors

Independent risk factors include:

  • Age > 60y
  • Smoking / vaping
  • Tourniquet time > 90 mins

Systemic risk factors include:

  • Diabetes
  • Vascular compromise
  • Inflammatory arthritis
  • Immuno-suppressive medication

 

Prevention

A randomised comparison of 2% Chlorhexidine vs immersion in 70% alcohol showed no difference in terms of colony forming unit counts following skin preparation. Chlorhexidine 0.5%/70% alcohol and iodine 1%/70% alcohol both decreased the amount of positive cultures in elective foot surgery with no significant difference between the two. Evidence shows that early post-operative bathing or showering has no bearing on infection rate. Without antibiotic prophylaxis infection rate was 2.3% compared to 1.2% in the group receiving antibiotic prophylaxis. The most commonly encountered pathogens were coagulase -ve and +ve Staphylococcus. Higher infection rates when patients received both pre- and post-operative antibiotics in comparison to those who received pre-operative antibiotics alone meaning there is no additional benefit in adding post-operative antibiotics in addition to pre-op antibiotics. Moreover extending antibiotic use is associated with infection with resistant organisms and associated with increased risk of Clostridium Difficile.

Although studies have not shown a benefit, administering antibiotics prior to tourniquet inflation is accepted practice.

No significant difference in bacterial pathogen yield from biopsy based on antibiotic exposure for osteomyelitis. 

When combined with aggressive irrigation and debridement, the use of polymethylmethacrylate antibiotic-loaded cement appears to be a beneficial adjunctive therapy

 

Management

History and examination should identify:

  • Pain, poor wound healing post-op, fever, rigors, general malaise
  • Tenderness, swelling, redness, wound breakdown, discharge, exposed metalwork
  • Pain out of proportion to the observed tissue insult must always raise the question of necrotising fasciitis

Blood tests should include:

  • WCC, CRP, ESR, and blood cultures if pyrexia present

Imaging:

  • Plain radiographs
  • MRI with fat suppression and STIR sequences

Identification of pathogen:

  • Superficial wound swabs of infected wounds
  • Aspiration of joint – blood culture bottles, molecular analysis
  • Deep samples. Infection should always be considered in cases of non-union and there should be a low threshold for taking fluid / tissue samples

Timing of surgery:

  • Once the diagnosis of infection has been made, debridement should be considered
  • Consider removal of foreign body material (sutures) if superficial infection
  • Infected non-unions may require hardware retention and suppressive antibiotics until healing has occurred
  • Ankle arthroplasty infection has poor results of Debridement and Implant Retention (DAIR) when compared to knee/hip arthroplasty; better results are obtained with two-stage revision with cement spacer techniques

 

References

  • Wiewiorski M, Barg A, Hoerterer H, Voellmy T, henniger H, Valderrabano V. Risk Factors for Wound complications in Patients After Elective Orthopaedic Foot and Ankle Surgery. Foot and Ankle International 2015, 36(5) 479-487
  • Chang A, Hughes A, du Moulin W, Mukerjee C, Molnar R. Randomised comparison of two skin preparation methods in foot and ankle surgery. Foot Ankle Surg. 2016;22(3):170-175
  • Modha MRK, Morriss-Roberts C, Smither M, Larholt J, Reilly I. Antibiotic prophylaxis in foot and ankle surgery: a systematic review of the literature. J Foot Ankle Res. 2018;11:61
  • Ellington K, Raikin S, Bemenderfer TB. What Strategies Can Be Implemented to Help Isolate the Causative Organism in Patients With Infection of the Foot and Ankle? Foot Ankle Int. 2019;40(1_suppl):33S-38S
  • Lipsky BA, Berendt AR, Cornia PB, et al; Infectious Diseases Society of America. 2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections. ClinInfectDis. 2012;54(12):e132–e173