WOUND-HEALING - TENSILE-STRENGTH VS HEALING TIME FOR WOUNDS CLOSED UNDER TENSION

Objectives: To measure tensile strength of wounds closed with and with out tension in rats, delineating the postoperative time interval when tensile strength is equal. To study patterns of growth in tensile stre ngth. Design: Transverse incisions on the backs of control rats were c losed with minimal tension. In experimental animals, after excision of skin from the back, wounds were closed with closing tensions in exces s of 70 g. Animals were killed at designated healing intervals for ten sile-strength testing of wounds. Subjects: One hundred Sprague-Dawley rats were divided into 5 groups, days 5, 7, 10, 14, and 21, with equal numbers of control and experimental animals in each group. Wounds fro m 94 animals were available for break-load testing. Intervention: Clos ing tensions were measured for transverse incisions on the backs of co ntrol animals before closure and after removal of 50 to 60 mm of skin from the backs of experimental animals. Results: Tensile strength was not significantly different on day 5. However, wounds closed under ten sion showed significantly higher tensile strength on days 7, 10: 14, a nd 21. Polynomial regression suggests a cubic relationship between hea ling time and tensile strength. Conclusions: Results suggest that tens ile strength of wounds closed under tension exceeds that of tensionles s wounds as early as day 7 following surgery. This study also illustra tes the 2 periods of rapid increase in wound tensile strength that pro bably coincide with specific stages of wound healing.