| Background and objective: Myocutaneous flaps were more and more used in esophageal surgery. And many authors have used and researched pectoralis major myocutaneous flap (PMMF) and latissimus dorsi myocutaneous flap (LDMF)and platysma myocutaneous flap(PMF) to reconstruct esophagus. PMMF and LDMF are bulky and clumsy fur growth, musculocutaneous flap(MCF) was easy to necrosis and being fistula after esophageal reconstruction. But PMF is thin and broad and rich in blood supply, offers the advantages of having an extensively available scope, being a simple procedure,causing mild trauma,and having a high survival rate and little complication for reconstruction on tissue defect of buccal cavity maxillofacial region as well as stenosis and defect of cervical esophgus., more and more application were used in fields of hypopharynx and occluslf surface and esophagus surgery. Malignant tumor was likely to develop recurrence and metastasis , combined therapy such as radiotherapy and chemotherapy are often required after surgical treatment .Few authors reported radiotherapeutic effection on myocutaneous flap (MF). Wang ZH studied the effect of radiotherapy after tumour resection in head and neck, and believed that flaps had well radiation tolerance after reconstruction. As far as know, no report on radiotherapeutic tolerance of PMF after esophageal reconstruction has been found. We did the experiment on adult dogs with cervical esophageal defect reconstructed using PMF, to explore the radiotherapeutic tolerance of platysma myocutaneous flap and the aftermath of radiotherapy on PMF after esophageal reconstruction in dogs.Methods: Twelve healthy adult dogs accepted perfect general anaesthesia and tracheal intubation before the experiment. Left lateral wall of dog's cervical esophagus was resected with length wise, and the defect of 3×4 cm was created. PMF which slightly exceeded the esophageal defect, introversed for esophageal reconstruction after designing and taking from the aboral of incision. Dogs with PMF imbedding esophagus were divided into three groups at random according to prophylactic irradiation (4800cGy),radical cure radiation dose(6400cGy) and control group. And 4 weeks postoperatively, all radiotherapy dogs received external radiotherapy of 400cGy from 8MV accelerator linear per two days. Parameters were designed as such : radiational field X×Y=6×7cm, target skin distance 100cm, complete penetration, and the dose rate was 200cGy per minute. Ingestion capability and Metatrophia as well as body weight were surveyed before and after irradiation. And early radiotherapeutic reaction of esophageal mucosa and PMF were surveyed by esophagoscopy and classified grade respectively. Stoma condition were viewed with barium swallow esophagogram and esophagoscopy before and after radiotherapy . Incision condition and fur of cervical skin was conveyed after 12 weeks at the end of the irradiation. And PMF condition and changing was observed after killing the dogs. We tested esophageal pressure referenced the measurement method of central venous pressure test. The relationship of esophageal perimeter , pressure and esophageal volume was tested in order to know esophageal compliance and stenosis index. The yield strength, intensive strength, maximum load, elastic module, rupture intensity and other biomechanics characters were detected with RG1-5A computer controlled electron almighty experiment machine. Poxyproline content of PMF WAS measured by chromometry. Tissue structres and arrangement of collagen by light microscopy after HE stain and Vans Gieons collagen stain was observed. The ultrastructure on epithelial cells and fibroblast and blood vessel endotheliumwas examined by Fhilip TECNI-10 transmission electron microscope.Results: 1. All the dogs' ingestion were no significant changing during whole experiment period. No predominant change on diet after radiotherapy than preradiation. And on the first day of irradiation, all the dogs' ingestion and drinking had no remarkable change ,but inappetence developed on the next day , began to recover on the third day, and had a normal intake of food till the end of the experiment. The body weight had no statistical loss. 2. In the early days of irradiation ,mild flare and congestion in esophagoscopy were found both in esophagus and flaps. And there were no hair, might flare and desquamation of skin in radiation area , but the esophagus around the stoma were manifest congestion and hydropsia . No necrosis, perforation, obviously swelling ,nor congestion occurred during the rediotherapy. The PMFs' incidence of acute radioreaction were obviously lower than in the contiguous esophageal mucosa ,which appearing later and mighter, and can completely resolution when radiatherapy finished. while a little hair grew in flaps as though indogs skin with unirradiation . 3. Stoma condition around myocutaneous flaps were no manifest stenosis and extravasation from stoma viewed with barium swallow before and after irradiation. And barium passed smoothly while esophageal wall with PMF were slightly rigidity and peristalsis loss as well as limited expand. 4. PMF showed light cystic distention when we injected water into esophagus in zero pressure, and the expansion degree were similar among the three groups. 5. After being killed , dogs' PMF stoma were completely healed, while dividing line was definite, fur growthed obviously. 6. Compliance an content of oxyproline of PMF , esophageal perimeter and pressure and volume, biomechanics had no signifant difference among these three group dogs . 7. Light microscope showed no significant difference of the PMF tissue structure among the three group . No obviously infection cells appeared in bilateralis of stoma, skin's structure had no obviously change, keeping cutinization. No special change was found in fibroblast, vascullar endothelial cell , acanthocyte, basement cell, accessory structure ,and folliculus disposition. After PMF radiotherapy, the alignment of PMF collagen were lest but larger than cervical skin wounds while the PMF's other structures had no manifest change after irradiation. The PMF's alignment among the three groups wre similar, well arranged in general. 8. Eelectronic microscope examination showed that all PMF kept a great quantity micro-filament and melanosome, cutinization in cuticular plate, cell-cell junction compact, many junctional complex , fibroblast and endothelialcell's ultramicrostructure were no obviously difference.Conclusion: 1.The PMFs' occurence of acute radioreaction after reconstruction of esophagus were obviously lower than in esophageal mucous tissue and cervical skin, appearing later and milder, and can completely resolution when radiatherapy finished. 2. PMF took well, fur grew well and hold cuticularization. And no contraction after irradiation. 3. No prominent change on the compliance of PMF, nor the esophageal perimeter, pressure, biomechanics and the content of oxyproline of PMF after radiation. 4.The histologic structure and ultrastructure had no apparent change after radiotherapy. In all, reconstructed esophsgus with Platysma myocutaneous flaps in these dogs might tolerate prophylactic and radical cure dose radiotherapy. |
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