Causes of Undermining in Wounds
Primary Pathophysiologic Mechanisms
Undermining in wounds develops primarily through contiguous spread of infection along fascial planes and tissue compartments, combined with ischemic tissue necrosis from compartmental pressure exceeding capillary perfusion pressure. 1
Infection-Related Causes
Bacterial invasion spreads along anatomic planes: Microorganisms migrate contiguously from the wound surface to subcutaneous tissues, including fascia, tendons, muscle, joints, and bone, creating undermined pockets as infection tracks along these structures 1
Compartmental anatomy facilitates proximal spread: The foot's rigid but intercommunicating compartments foster infection spread, with tendons within compartments serving as conduits for bacterial migration from higher to lower pressure areas 1
Inflammatory pressure causes tissue necrosis: The inflammatory response induced by infection increases compartmental pressure beyond capillary pressure, leading to ischemic tissue necrosis that creates undermined spaces 1
Necrotizing fasciitis demonstrates extensive undermining: During surgical exploration of necrotizing infections, extensive undermining of surrounding tissues is characteristically present, with tissue planes easily dissected with a gloved finger or blunt instrument due to fascial destruction 1
Vascular Insufficiency
Peripheral arterial disease limits tissue perfusion: Limb ischemia increases the risk of wounds becoming infected and adversely affects infection outcomes, creating devitalized tissue that separates from viable tissue to form undermined areas 1
Reduced blood flow creates zones of necrosis: Inadequate blood supply prevents migration of phagocytic cells and antibiotic delivery, allowing bacterial proliferation in poorly perfused tissue planes that become undermined 1
Wound-Specific Risk Factors
Deep, long-standing, or recurrent wounds: These characteristics predispose to undermining development through chronic infection and tissue destruction 1
Traumatic wound etiology: Wounds caused by trauma are more likely to develop undermining compared to other wound types 1
Pressure ulcers with devitalized tissue: Lower temperature at the wound edge compared to the wound bed (detected by thermography) predicts undermining development within one week, with a relative risk of 4.0 2
Clinical Indicators of Undermining
Secondary signs of diabetic foot infection include: Non-purulent secretions, friable and discolored granulation tissue, wound undermining itself, and foul odor 1
Undermining measurement is part of wound assessment: The DFI Wound Score includes undermining depth as a prognostic indicator, with undermining <2mm scoring 3 points, 2-5mm scoring 5 points, and >5mm scoring 8 points 1
Common Clinical Pitfalls
Superficial wound cultures miss deep infection: Bacteriologic characteristics of superficial wounds do not necessarily indicate deep-tissue infection that causes undermining; deep tissue or bone specimens are required for accurate diagnosis 1
Delayed recognition allows progression: Failure to probe wounds and assess for undermining early allows continued bacterial spread along tissue planes 1
Inadequate debridement perpetuates undermining: Leaving devitalized tissue in undermined spaces maintains the infection and prevents healing 3