New experimantal composite flap model in rats: Gluteus maximus-tensor fascia lata osteomuscle flap

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  • NEW EXPERIMANTAL COMPOSITE FLAP MODEL IN RATS:GLUTEUS MAXIMUS-TENSOR FASCIA LATA OSTEOMUSCLE FLAP

    SERDAR NASIR, M.D.,1* ASIM AYDIN, M.D.,1

    AYCAN KAYIKCIOGLU, M.D.,2 CENK SOKMENSUER, M.D.,3 AND

    AZEM COBANER, M.D.4

    Experimental animal models need to be developed forstudies of composite flaps that have often recently been usedfor defects of both bone and soft tissues. A consistentanatomy, simple surgical technique, and reliable blood floware essential for the success of experimental flap studies.Here we propose a gluteus maximus-tensor fascia lata os-teomuscle flap in rats as a model of these qualities. Gluteusmaximus and tensor fascia lata muscles and the adjacentiliac bone segment were combined as a lateral circumflexfemoral artery-based flap. To test the reliability of this com-posite flap, three types of composite tissues were harvestedand replaced: osteomusculocutaneous flap, osteomuscleflap, and osteomuscle composite graft. The osteomusculo-cutaneous flap was elevated by including a skin island overthe gluteal region. The osteomuscle graft was formed bydeliberately dividing the vascular pedicle of the osteomuscleflap. Direct observation revealed complete necrosis ofthe skin islands in all osteomusculocutaneous flaps.Microangiography of the flap demonstrated that both mus-

    cles and the attached bone were supplied by the pedicle. Dyestudies with nitro blue tetrazolium (NBT) and India ink dem-onstrated dye uptake2 in both muscle and bone componentsin osteomuscle flaps. Histological examinations also dem-onstrated the viability of both tissues only in the flap group.Bone scintigraphy performed in flaps on postoperative day 7demonstrated radionuclide uptake, confirming perfusion ofthe bony segment. The gluteus maximus-tensor fascia lataosteomuscle flap is a reliable and simple model for com-posite flap studies that offers the following advantages: 1) itis a new composite flap which includes bone, 2) it can bedissected easily with the naked eye, without using themicroscope, 3) it has a long pedicle for flap displacement,and 4) it is a small animal model.

    2003 Wiley-Liss, Inc.MICROSURGERY 23:582588 2003

    Osteomuscle flaps have been used in the reconstructionof complex defects after either tumor extirpation or se-vere trauma.17 Clinical applications of osteomucleflaps have fueled an interest in the biology of these flaps,particularly the mechanisms by which the bone cellsurvives and heals bone defects with a resistance to ra-diotherapy.8 Further investigations of osteogenic, oste-oinductive, and osteoconductive substances are alsobeing conducted. For this reason, experimental flap re-search is still needed for the proper use of composite

    flaps in reconstructive surgery.911 Therefore, some ex-perimental flap models were described in small ani-mals.1217

    Rats are preferred for their affordability, easy han-dling, and robustness. On the other hand, the maindisadvantage of small animal flap studies is the re-quirement of tedious dissection under a microscope.Extended surgery and anesthesia time by using a mi-croscope in studies with large numbers of animalsmay become frustrating. Increased working time mightcause the animals to die. An easily and quickly dis-sected flap, by obviating the need for surgical expertise,would let researchers focus on the main theme of theirstudy.

    Although many muscle and myocutaneous flapmodels were described,19,20 only four osteomusculocu-taneous flap models were reported in the rat: the saph-enous artery flap,12 the iliac osteomusculocutaneousflap,13 the thigh flap,14 and the acromiotrapezius flap.15

    The purpose of this study was to describe an osteo-musculocutaneous flap model in rats which can be dis-sected quickly with the naked eye for smoothercomposite flap studies.

    1Department of Plastic and Reconstructive Surgery, Suleyman Demirel Uni-versity School of Medicine, Isparta, Turkey

    2Department of Plastic and Reconstructive Surgery, Hacettepe UniversitySchool of Medicine, Ankara, Turkey

    3Department of Pathology, Hacettepe University School of Medicine, Ankara,Turkey

    4Nuclear Medicine, Antalya, Turkey

    *Correspondence to: Dr. Serdar Nasr, _Istiklal mahallesi 105. cad. No: 62Daire:1 4 Isparta, Turkey. E-mail: snasir@med.sdu.edu.tr

    Received 26 May 2003; Accepted 8 July 2003

    Published online in12 Wiley InterScience (www.interscience.wiley.com). DOI:10.1002/micr.10212

    2003 Wiley-Liss, Inc.

  • MATERIALS AND METHODS

    Animal Care

    In total, 40 adult Wistar rats weighing 200250 gwere used in this study. This study was conductedaccording to the guidelines of the University AnimalCare Committee. All animals were kept in individualcages in a room with standard environmental condi-tions. The animals were fed ad libidum. Operations wereperformed under ketamine (90 mg/kg) and xylazine (10mg/kg) anesthesia. Supplementary doses were given asnecessary.

    Surgery

    Rats were divided into three groups: anatomic study,flap group, and graft group.

    Anatomic Studies (n= 10)

    Animals were dissected for vascular anatomy of thegluteus maximus3 and tensor fascia lata (TFL) muscles,and the branching pattern of their pedicle and lateralfemoral circumflex artery. Dissection of the vascularpedicle was carried from distal to proximal, until theorigins of the vessels from the abdominal aorta, andinferior vena cava were identified. A laparatomywas performed to measure the diameter and the lengthof the vascular pedicle. Dimension and weight of thegluteus maximus tensor fascia lata muscles were alsomeasured.

    Flap Group (n= 20)

    Two types of flaps were designed: an osteomuscu-locutaneous flap (n = 10) and a osteomuscle flap (n =10). For the former type, a skin island was planned,measuring about 3 3 cm over the gluteus maximusmuscle, extending from the dorsal midline to the ante-rior axillary line, and from the hip joint to the superiorventral spine of the iliac bone (Fig. 1A). Following in-cision of the skin island and stitching it to the underlyinggluteus maximus muscle to avoid stretching of skinperforators, the gluteus maximus muscle was dividedfrom its insertion to the hip joint. Then the muscle wasdissected anteriorly, including the inseparably unitedtensor fascia lata muscle. The fascia in the mid-dorsalside of the rat was incised parallel to the vertebrae up tothe superior ventral spine of the iliac bone. Then thegluteus maximus muscle was divided from the thighfascia anteriorly and the biceps femoris muscle posteri-orly. The Iliac bone osteotomy was planned withoutdisrupting the muscle-bone connection. A portion of

    iliac crest measuring 1 1 cm was included in the flap.Consequently the flap was elevated over the lateralfemoral circumflex artery that enters the flap betweenthe rectus femoris and iliacus. All components of theosteomusculocutaneous flap, including the gluteusmaximus muscle, tensor fascia lata muscle, iliac bonesegment with its muscle cuff, and the overlying skin is-land, were elevated on the lateral femoral circumflexvascular vessels as a single unit (Fig. 1BD). The othertype of flap was the osteomuscle flap comprising onlymuscle and bone without including a skin island. Theisland flaps were replaced.

    Composite Graft Group (n= 10)

    The osteomuscle flap as previously described waselevated, and then the vascular pedicle was divided inthe zone between the rectus femoris and iliacus muscle.Thus, muscle and iliac bone segment were replaced.

    Assessment of Flap Viability

    Direct observation. The survival of the skin islandwas evaluated on postoperative day 7 by gross inspec-tion of the flap color compared with normal skin.21

    Microangiography. Microangiography was applied todelineate the vascularization of the osteomuscle flap intwo animals on postoperative day 7. After cannulatingthe abdominal aorta, 50 cc of the mixture (at 70C) thatwas made of 50 g of silver oxide, 5 g of gelatin, and 100 ccof the isotonic was injected with a syringe. The flaps werestored in an animal refrigerator at 4C for 4 h. Then allflaps underwent radiography with an animal soft X-raymachine, using Microvision-C mammography film.

    Dye studies. Nitroblue tetrazolium staining was usedfor muscle viability on postoperative day 7. Accord-ingly, muscle tissues from three animals of each groupwere sliced into 0.5-cm pieces and were held for 30 minat 37C in buffered nitroblue tetrazolium. Ischemic in-jury between flap and graft groups was compared ac-cording to stain quality with nitro blue tetrazolium

    5(NBT).Viability of bone was evaluated by the presence of

    dye in the vessels after India ink injection. Followingcannulation of the abdominal aorta in three animalsfrom the ostemuscle flap group with a 24-gauge cathe-ter, 5 ml of India ink were injected. The bone segment ofthe flap was divided, decalcified, stained with hema-toxylin-eosin, and examined under light microscopy for

    New Experimental Composite Flap Model in Rats 583

  • the presence of India ink in blood vessels of the bonemarrow and cortex.

    Bone scintigraphy. In the flap group, three animalsunderwent radionuclide bone scintigraphy on post-operative day 7. After the animals were anesthetized,1 mCi6 of techenitium-99m methilene diphosphonate wasinjected via the external jugular vein. Approximately 4 hafter the injection, scanning was carried out using a

    gamma camera with a low-energy, general-purposeparallel-hole collimator.17

    Histology. On postoperative day 7, the animals in theflap and graft groups were killed with an overdose ofinhaled ether. Flaps and grafts were harvested andplaced in 10% buffered formalin. Bone segments weredecalcified in a mixture of formalin, formic acid, andconcentrated hydrochloric acid. The bone and musclesections stained with H&E were evaluated.

    RESULTS

    Anatomic Studies

    The g

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