Smarter Infection Control for Post-Surgical Site Infections

In small animal surgery, SSI incidence ranges from 0.8 to 18.1%, and in equine patients, from 5 to 30%.1 As many as 18.2% of dogs experience SSI after orthopedic surgeries, and those with metallic implants are nearly 6 times more likely to develop SSI.3 Even up to 81% of clean orthopedic surgeries with strict adherence to sterile practices have some type of contamination.3  

Along with all the factors that affect infection risk, surgeons using implants must also contend with biofilms that form almost immediately.4 Fibroblasts and other host cells adhere to the extracellular matrix that forms on the implant; however, staphylococci can also adhere, spawning a biofilm nearly impenetrable to the host immune system and systemic antibiotics. 4,5   Surgical site infection, especially after implants are placed, prevents healing, hinders implant integration, and may cause premature implant failure.3  

Any tool that delivers effective antimicrobial control and doesn’t drive systemic antibiotic resistance or harmful side effects will help prevent and treat SSI.5 That’s a win for pets, their owners, and the veterinary care team. 

Clinicians have used cement spacers or beads (which require removal during a subsequent surgery), biodegradable collagen sponges, and biocompatible bone as carriers of locally-eluting antibiotics to prevent and treat local infections.2 They achieve high local antibiotic concentrations, prolong antimicrobial half-life, and demonstrate consistent elution activity.6  

Bone cements include polymethylmethacrylate (PMMA), calcium sulfate, and hydroxyapatite.4 PMMA provides physical support and can be mixed with antibiotics before polymerization; however, it is non-biodegradable and requires heat-stable antibiotics.4, 6 It may weaken when combined with certain antibiotics, become a nidus for bacterial colonization, or cause systemic effects.4,6  

Calcium sulfate and hydroxyapatite are mixed with water, are biocompatible, and don’t undergo heating or require removal.4,6 Calcium sulfate reliably releases antibiotics and disrupts biofilm in vitro; however, it may cause persistent drainage, ossification, or hypercalcemia.6 Hydroxyapatite’s porous surface promotes healing and bone formation; however, it slowly degrades, limiting consistent antibiotic release and may allow for bacterial colonization.6  

Both provide a physical base for cells to attach and start repairing tissues.  Orthomix bone graft uses cancellous bone, while CollaVET resorbable collagen contains purified Type 1 collagen in foam, sponge, and fibrillar matrices.