Osteomyocutaneous flap as a preclinical composite tissue allograft: swine model.

Composite tissue allotransplantation (CTA) constitutes one of the last frontiers of microsurgery. Prior to its clinical application, the long-term efficacy of modern immunotherapy must be tested in a pre-clinical CTA model. Based on the concept of osteomyocutaneous forearm flap, we developed a CTA flap model in swine. After identifying the vascular territory of the flaps in six pigs (vascular casting), flaps were transplanted from mismatched donor to recipient pigs (n = 6). Rejection was assessed daily by visual inspection and histopathology of biopsy specimens. Recipient pigs were able to ambulate immediately following surgery. There were no flap failures owing to technical or surgical complications. Rejection occurred over a period of 7 days as manifested by edema, cellular infiltration, epidermalysis, and thrombosis. This pre-clinical flap model is excellent for evaluating the effectiveness of modern immunotherapy because it is anatomically and immunologically relevant and because the minimal morbidity caused to the animal permits long-term studies.

Swine composite tissue allotransplant model for preclinical hand transplant studies.

Our laboratory previously developed and used an orthotopic radial forelimb osteomyocutaneous flap in the pig as a preclinical composite tissue allograft (CTA) model. To ensure that it mimicked the clinical situation as closely as possible we developed this model taking many immunologic and reconstructive considerations into account. While our original pig CTA model was ideal for studying the methods of preventing skin, muscle, bone, vessel and nerve rejection, and systemic toxicity, it did not include specialized tissues/structures of a joint and digit. Therefore, we were unable to evaluate rejection of these specialized tissues and their functional properties. Recognizing the importance of assessing joint rejection and function in hand transplantation research we developed a new swine forelimb CTA model that included the animal's medial digit. The present study describes the anatomy and the transplantation technique used in this new preclinical CTA model. We transplanted a radial osteomyocutaneous flap that included the medial digit between two size- (17-21 kg) and age- (6-8-week) matched farm pigs. We removed the digit from the recipient pig's forelimb in continuity with a section of the radial bone and replaced it with the same structure transplanted from a donor pig. After transplantation, a full-length cast was placed on the recipient pig's operated limb and changes in flap color, temperature and the presence of edema were monitored continuously for 6 h, and then regularly at predetermined intervals over 4 days. No weight bearing restrictions were placed on the animal's operated limb. After 4 days, the animal was euthanized. Direct visual monitoring of the allograft during 4 days revealed it was viable with no signs of graft failure due to technical complications associated with the transplant procedure. Upon waking from anesthesia, the animal stood and wandered freely about its cage with no apparent difficulty. Based on the animal's high level of activity at this time, we concluded that the procedure caused it minimal morbidity. At 4 days after the operation, early signs of rejection (skin erythema and edema) were observed. By incorporating a digit into our original CTA pig forelimb model we have made it a better model for performing preclinical hand transplant studies. The added advantage of being able to assess methods of preventing rejection in the specialized joint/digital tissues (articular cartilage, digital flexor and extensor systems, the nail complex) and assess long-term function of these structures is important. The fact that the procedure does not cause major morbidity to the animal makes it possible to conduct long-term graft survival and functional studies.

Long-term survival of an extremity composite tissue allograft with FK506-mycophenolate mofetil therapy.

BACKGROUND: High-dose tacrolimus (FK506) monotherapy has significantly prolonged rat hindlimb allograft survival. With an eye toward direct clinical application, we used a large-animal extremity composite tissue allograft model to assess the antirejection efficacy and systemic toxicity of combination FK506-mycophenolate mofetil (MMF) treatment. METHODS: Radial forelimb osteomyocutaneous flap transplants were performed between size-matched outbred pigs assigned to one of two groups: 5 control pigs received no immunosuppression and 9 animals received a once-daily oral FK506-MMF-prednisone regimen. Rejection was assessed by visual inspection of flap skin and was correlated with serial histopathologic examination of skin biopsy specimens. RESULTS: In all control pigs the flap was completely rejected on day 7. Of the 9 pigs receiving treatment, 3 died from pneumonia on days 29, 30, and 83 without signs of rejection and another died from gastric rupture on day 42 with persistent mild rejection. The remaining 5 animals were free of rejection at the end of the 90-day follow-up period (P < 0.005 vs controls). Overall, 5 pigs had pneumonia, 4 septic arthritis, 3 toe abscesses, and 5 diarrhea and decreased weight gain. CONCLUSIONS: Combination oral FK506-MMF treatment provided a superior antirejection effect but more produced more toxicity than that previously demonstrated with cyclosporin A-MMF therapy in our model. Our results suggest that reduction of FK506 or MMF doses might decrease both infectious and drug-specific side effects while still providing adequate prophylaxis against rejection.

Scoring of skin rejection in a swine composite tissue allograft model.

BACKGROUND: For the first time, we define and correlate visual and histologic grading systems of composite tissue allograft (CTA) skin rejection in a large-animal model and determine the utility of these grading systems for early diagnosis and monitoring of rejection. MATERIALS AND METHODS: Sixteen pairs of outbred swine underwent transplant of a forelimb osteomyocutaneous free flap. Group I (n = 6) did not receive immunosuppressive therapy. Group II (n = 10) received oral cyclosporin A, mycophenolate mofetil, and prednisone. The flap was visually inspected and protocol skin biopsies were taken at frequent intervals over a 90-day period. Visual Grades 0 (no rejection) to 4 (severe rejection) were assigned based on skin color, bleeding from biopsy site, and blister formation. Histologic Grades 0 to 4 were assigned based on the degree of vasculitis, folliculitis, dermal inflammation, and epidermal degeneration present. RESULTS: All Group I animals progressively rejected their graft by Day 7. Group II grafts survived from 19 and 90 days; 93% of 115 biopsy specimens were read to be within +/-1 histologic score of their assigned flap visual grade. Visual assessment carried an 8% false positive and 39% false negative rate with regard to biopsy-proven rejection. However, 81% of missed rejection specimens were histologic Grade 1. Biopsy, when visually indicated, would detect all rejection episodes when histologically Grade 1 or 2 and still potentially reversible. CONCLUSIONS: Visual scoring of CTA skin serves as a useful tool for initially detecting rejection, but repeated histologic evaluation is necessary for monitoring the subsequent course of the graft.

Long-term composite tissue allograft survival in a porcine model with cyclosporine/mycophenolate mofetil therapy.

BACKGROUND: Low-dose cyclosporine (CsA)/mycophenolate mofetil (MMF) therapy has significantly reduced the frequency of rejection and drug-induced side effects in rat hindlimb allograft recipients. With an eye toward direct clinical application, we developed a large-animal extremity composite tissue allograft model to assess the antirejection efficacy and systemic toxicity of combination CsA/MMF treatment. METHODS: Radial forelimb osteomyocutaneous flap transplants were performed between size-matched, outbred pigs assigned to one of two groups: 5 control pigs received no immunosuppression, and 10 pigs received a once-daily oral CsA/MMF/prednisone regimen. Rejection was assessed by visual inspection of flap skin and correlated with serial histopathologic examination of skin biopsies. RESULTS: In all control pigs, the flap was completely rejected on day 7. Of the 10 pigs receiving treatment, one died from pneumonia and an another from an anesthetic complication on days 19 and 30, respectively, without signs of rejection. Two flaps were lost on days 25 and 29 from severe rejection. Three pigs were free of rejection at the end of the 90-day follow-up period, and three had stable mild-to-moderate rejection at 90 days (P= 0.0007 vs. controls). White blood cell and platelet counts, serum creatinine values, and liver function tests remained normal in all animals receiving immunosuppressive therapy. CONCLUSIONS: Our results, to our knowledge, demonstrate for the first time that rejection can be significantly delayed in a large-animal composite tissue allograft model including skin using only orally administered agents dosed according to clinically relevant strategies without significant drug-specific systemic side effects.

Nonmicrosurgical use of an osteocutaneous parascapular flap for reconstruction of a complex hand defect.

We describe the nonmicrosurgical use of an osteocutaneous parascapular flap as a new application in reconstructive hand surgery for reconstruction of a complex hand defect resulting from a gunshot injury. This technique, namely the transaxillary parascapular flap, is easy to perform and does not require the sophisticated equipment and expertise of microsurgery. This is an important advantage, especially for developing countries in which microsurgical facilities are limited.

Ketanserin accelerates wound epithelialization and neovascularization.

We investigated the acute effects of topical ketanserin, a 5-HT(2) (serotonin) receptor blocker, on wound epithelialization and vascularization with the use of the hairless mouse ear model. Varying concentrations of Ketanserin (0%, 0.2%, 2.0%, 20% weight/volume) were administered to standardized full-thickness skin wounds on the dorsum of the hairless mouse ear immediately after surgery and daily thereafter. With the use of video microscopy and computer-assisted planimetry, vascularization and epithelialization were traced every third day until the wounds were fully healed. Arteriole diameters at selected sites near the skin wound were measured before wound creation and after wounding. It was concluded that topically administered ketanserin significantly accelerates both the vascular (p < 0.001 at 2% and 20% concentrations) and epithelial (p < 0.001 at 20% concentration) rates of wound healing in full-thickness nonpathologic skin wounds. Vasodilation of terminal arterioles was not a major response to Ketanserin. Faster epithelialization was possibly due to direct effect of ketanserin on epithelial cells.

Tissue expansion-assisted prefabrication of the forehead flap for nasal reconstruction.

A new technique for nasal reconstruction is described. This method--expansion-assisted flap prefabrication--is essentially a simultaneous application of pretransfer grafting and tissue-expansion procedures for creating custom-made forehead flaps to meet varying requirements of nasal reconstruction. We have applied this new technique on seven patients, with full-thickness nasal defects during a 3-year period. Results from these patients are presented with a review of different use of flap prefabrication principles in nasal reconstruction.

The split-lip advancement technique (SLAT) for the treatment of congenital sinuses of the lower lip.

In this paper we present 7 cases of Van der Woude syndrome and describe a new surgical technique for the treatment of congenital sinuses of the lower lip. Our technique is essentially a new modification of the elastic lip flap technique of Goldstein. We term this procedure the split-lip advancement technique, in which two opposite labial artery--based flaps including the whole thickness of the vermilion and the mucosal surface of the lip are used to repair the median defect that resulted from excision of the sinuses. To our knowledge, there have been no reports of the use of this technique in the treatment of congenital sinuses of the lower lip.

Intra-operative tunnel expansion to prevent tunnel compression following latissimus dorsi muscle transfers.

The intra-operative tunnel expansion technique is described to prevent tunnel compression following muscle transfers. The results of ten cases of latissimus dorsi transfer using this new technique are reported.

A new design of the cross-finger flap: the C-ring flap.

A new cross-finger flap, the C-ring flap, is described for repair of degloved amputation stumps and dorsal and volar defects of the fingers. The C-ring flap is an axial pattern cross-finger flap based on one digital vascular bundle either distally or proximally. We used this flap in 12 cases with different types of finger defects. The results were satisfactory. We conclude that the C-ring cross-finger flap had distinct advantages over standard cross-finger flaps. These advantages are discussed.

Eminectomy for the treatment of chronic subluxation and recurrent dislocation of the temporomandibular joint and a new method of patient evaluation.

We have performed this technique bilaterally on 39 patients with chronic subluxation and 13 patients with recurrent dislocation since 1985 and have had good results with patient satisfaction. These patients had significantly higher articular eminences than normal control individuals. Also, we have used echography as a new application of an old technique, to evaluate the patients objectively in the preoperative and postoperative periods.