Wound healing. Tensile strength vs healing time for wounds closed under tension.

OBJECTIVES

To measure tensile strength of wounds closed with and without tension in rats, delineating the postoperative time interval when tensile strength is equal. To study patterns of growth in tensile strength.

DESIGN

Transverse incisions on the backs of control rats were closed with minimal tension. In experimental animals, after excision of skin from the back, wounds were closed with closing tensions in excess of 70 g. Animals were killed at designated healing intervals for tensile-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 from 94 animals were available for breakload testing.

INTERVENTION

Closing tensions were measured for transverse incisions on the backs of control 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 tension showed significantly higher tensile strength on 7, 10, 14, 21. Polynomial regression suggests a cubic relationship between healing time and tensile strength.

CONCLUSIONS

Results suggest that tensile strength of wounds closed under tension exceeds that of tensionless wounds as early as day 7 following surgery. This study also illustrates the 2 periods of rapid increase in wound tensile strength that probably coincide with specific stages of wound healing.