Accelerated closure of biopsy-type wounds by mechanical stimulation

An Overlooked but Effective Wound Care Methodology: Hydromechanical Therapy Revisited

Chronic wounds are frequently difficult, expensive to treat, and pose a significant burden on both the patient’s quality of life and health care system. Their recalcitrance to treatment stems from multiple factors, particularly the presence of bacterial biofilms within the wound bed. However, a commonly overlooked modality in the field of wound care, pressurized irrigation, offers an inexpensive mechanical debridement force capable of dislodging these biofilms that contribute to delayed healing of chronic wounds. We present here a single clinical case of a difficult nonhealing wound that had previously failed 3 months of negative-pressure wound therapy, a much more expensive modality. This chronic plantar foot wound was treated with daily application of hydromechanical therapy using tap water at home. It achieved a stable granulation surface, and with a small skin graft, healing with no recurrence seen at 15-month follow-up. We speculate that a combination of tissue stimulation and disruption of the wound surface biofilm contribute to improved healing, supporting a reevaluation for the use of pressurized irrigation in the treatment of chronic wounds.

The hypothesis of 'biophysical matrix contraction': wound contraction revisited

Wound contraction is an orchestrated phenomenon that contributes to closure of wounds that heal by secondary intention. However, excessive and premature contraction results in scarring. Although the exact mechanism of contraction is unknown, the wound closure process is accompanied by and followed by changes in the physical and mechanical properties of the wound and periwound tissues during the biological transformation. Transforming growth factor-beta (TGF-beta) induces a contractile phenotype in the cellular-extracellular matrix. Meanwhile, various external and internal mechanical stresses lead to microdeformations of the wound milieu with resultant upregulation of TGF-beta. Furthermore, the mechanical strain exerted on collagen fibres and other piezoelectric tissues leads to development of piezoelectric current in the wound site, which acts synergistically with TGF-beta. TGF-beta and mechanical strain regulate the orientation of collagen fibres parallel with the skin surface, which minimises the induction of piezoelectricity through the action of internal forces because of improper angulation of collagen fibres and these forces. The resulting dominance of external forces guides the contractile activity towards restoration of the original unwounded tissue architecture and functional activity of the previously wounded milieu. The aforementioned contractile activity proceeds into the remodelling phase of wound healing as the level of TGF-beta is reduced and myofibroblasts undergo apoptosis.

Superficial topography of wound: A determinant of underlying biological events?

Three-dimensional configuration of wounds varies considerably according to the etiology. Wounding of skin is proceeded by release of dermal pretension. Subsequent disruption of physical equilibrium with resulting development of force vectors alters the primary shape of wound to maintain a new dynamic physical equilibrium. This leads to the development of stress-relaxation and stress-concentration areas throughout the wound milieu. Mechanical strain produces piezoelectric current which is maximal in stress-relaxation regions due to lower tissue stiffness and higher mobility. Early surge in the tissue level of TGF-beta would be exaggerated through synergistic interaction with piezoelectric current in stress-relaxation areas. Subsequently, fibroblasts migrate to these areas due to galvanotaxis. The gradual dissipation of tissue tension, due to irreversible loss of viscous strain, reduces the synergistic action of TGF-beta and piezoelectricity. However, a similar pattern of activity of TGF-beta due to the polarized migration of fibroblasts, which are the main source of TGF-beta during secondary surge, may be continued. It seems that a biological-mechanical continuum exists for wounds so that even the superficial topography of wounds may affect the underlying biological activity and final healing outcome during healing of dermal wounds.