COMPARISON OF DERMAL AND EPITHELIAL APPROACHES TO LASER-TISSUE SOLDERING FOR SKIN FLAP CLOSURE

Background and Objective: Prior studies of laser tissue soldering (LTS ) of epithelial skin have shown poor wound strength in the short-term; however, we hypothesize that greater tensile strength and healing pro perties will result from directing laser energy to the dermal aspect o f the skin. The current study compares wound strength and histology in a rat skin flap model of epithelial and dermally applied LTS. Study D esign/Materials and Methods: Skin flaps (2.5 x 4 cm) were raised and b isected on the dorsum of Sprague-Dawley rats. The center line of bisec tion was closed from a dermal approach by LTS (LTS-D, diode laser 15.9 W/cm(2) + Columbia solder), the upper incision by epithelial LTS (LTS -E), and the lower incision by suturing (7-0 Vicryl). Wound skin strip s (1-2 mm x 10 mm) were studied immediately (N = 14) and at 3 (N = 57) , 7 (N = 31), and 10 (N = 28) days postoperatively and were subjected to tensiometric analysis. Histologic staining with hematoxylin and eos in and Mallory's trichrome methods were used to define wound architect ure. Results: No wound dehiscences were noted in any group. Greater im mediate tensile strength was noted in wounds closed by LTS-D (521 +/- 61 g/cm(2)) versus LTS-E (342 +/- 65 g/cm(2)); however, this differenc e was not statistically significant (P = .08). By 3 days, both LTS-D ( 476 +/- 55 g/cm(2)) and LTS-E (205 +/- 37 g/cm(2)) maintained their in itial strength; however, LTS-D and sutured (436 +/- 49 g/cm(2)) wounds were stronger (P < .05) than LTS-E. At 7 and 10 days, LTS-D (2,433 +/ - 346 g/cm(2) and 3,100 +/- 390 g/cm(2)) showed superior tensile stren gth (P <.05) compared to both LTS-E (1,542 +/- 128 g/cm(2) and 2,081 /- 219 g/cm(2)) and suturing (1,342 +/- 119 g/cm(2) and 1,661 +/- 115 g/cm(2)). Histologic analysis of LTS-D wounds at 3 days showed full-th ickness tissue apposition, complete epithelialization, and minimal inf lammation or thermal injury. At 7 days, solder was present in the woun ds. In contrast, LTS-E wounds at 3 days displayed lack of epithelializ ation secondary to thermal injury and partial-thickness tissue apposit ion. However by 7 days, epithelialization was complete with moderate s carring, and no solder was seen. Sutured samples appeared similar to L TS-D, except for poorer tissue apposition at the hypodermis. Conclusio n: Our results show that skin flap wound healing after dermal LTS is s uperior to epithelial LTS and emphasizes the importance of site specif icity in the utilization of this operative technique in reconstructive surgery. (C) 1998 Wiley-Liss, Inc.