| BackgroundVarious surgical techniques have been proposed for perineal reconstruction, one of which is the use of cutaneous thigh flap based on pudendal neurovascular bundle (Pudendal thigh perforator flap, PTPF). A perforator flap can be defined as a free flap consisting of skin, subcutaneous fat and the nourishing by transmuscular perforator vessels which is freed by a careful dissection from the underlying muscle. It was first described and successfully performed for perineal reconstuction by Wee and Joseph in1989, based on their neurovascular studies of the upper thigh, medial groin, and perineum in female fresh cadavers. Superiority of this technique was apparent as it was simple, reliable, less flap loss, flap retained sensory innervations and was able to hide the scars in the groin crease. In female, there was less incidence of postoperative vaginal stenosis and natural angle of intercourse. Bai Jin et al in2008further characterized our knowledge of perforating vessels, venous returns and the cutaneous nerve innervations in the perineum through their microdissection fresh cadaver study which enabled a better designing of PTPF. A more precise knowledge of the anatomy of the perforating vessels in the perineum have reduced the overall rate of vascular complications in the flap reconstruction of perineum, however, there are individual anatomical variations and its implication in flap loss is still a big fear for reconstructive surgeons.Precise location and anatomy of the perforating vessels in PTPF is essential for flap survival. Traditional clinical training on flap anatomy is based on textbooks,2dimensional pictures and cadavers does help reducing this risk, however, a more precise three dimensional visualization of the anatomy of PTPF and its neurovascular components of the individual surgical candidate is desirable and the use of CT angiography (320-row multidetector computed tomography angiography) and3D reconstruction technology to design the PTPF’s pedicle, such as described in this article, makes it possible.ObjectThe objective of this study is to determine the quantity, position, and caliber of perforating vessels in the perineum, and to provide ananatomic basis for designing perineal perforator flaps. To provide a body surface position method to help design pudental thigh perforator flap’s pedicle by using320-row multidetector competed tomography angiography and3D reconstruction.MethodTen adult cadavers (20sides) fixed in10%formalin were dissected in this study. Red latex was infused from the external iliac artery and radial artery, using a modified lead oxide-gelatin infusion technique. Cadavers were dissected with an operating microscope (×10).Structures of artery and venous were measured using a sliding caliper (accurate to0.2mm). The border of the examined area was:inferior, the imaginary line between the2ischiadic tuberosities; superior,3cm above the superior margin of pubic symphysis; medial, the lateral margin of the scrotum (labium); and lateral, interfemusplica.Patient data of our department were reviewed retrospectively. We have compared two groups who received perineum reconstruction using PTPF between2008-2012. Case group consisted of18patients who had perineum reconstruction using PTPF, with the aid of preoperative localization of superficial external pudendal artery using contrast-enhanced CT angiography and then3D image reconstruction. Indications for their surgeries were pseudohermaphroditism (2females and2male), congenital vaginal atresia (21females), and perineum tumors (9males-2lymphangioma,3basal cell carcinoma and2Paget disease,6females-1lymphangioma,2basal cell carcinoma,3Paget disease), divided into2groups randomly. The mean patient age was30.4years and the mean height was164.4cm. Four of the pseudohermaphrodite patients had endocrinological disorders and they were taking regular medications. All male patients were smokers but all female patients were non-smokers. Patients were instructed to quit smoking for at least2weeks preoperatively. Control group consisted of20patients who had perineum reconstruction using PTPF without the aid of the above imaging technology.Computer tomography angiographies (320-row MDCT scanner, Aquilion ONE, Toshiba Medical Systems, Otawara, Japan) were performed using a standardized protocol in our Radiology Department. The CT Scanner has320detector rows (each0.5mm wide) with a rotation time of350ms (with a temporal resolution of175ms for half reconstruction). A single rotation of the gantry could obtain320slices of CT images from a16cm volume area without a helical scan. Therefore, sub-second times grants MDCT to capture a high-definition three-dimensional (3D)-CT image. In addition, the intermittent scan during contrast infusion allows the reconstruction of dynamic3D-CT images. Scanning was performed during the intravenous administration of80-90ml of the contrast material (Ultravist370, Bayer Schering, Germany) using an automated injector device at a rate of4.0ml s-1. The imaging voltage and current were controlled at120kV, and350mA, and gantry rotation time was0.5s. The generated images were transferred into a computer and were then interpreted using Vitrea software (Vitreasoft, Vitreastation, Tokyo, Japan) to regenerate the final dynamic3D Volume-rendering image. All cross sectional images were displayed in sagittal, coronal, transverse planes and these were reconstructed to create the3D map.Information of the vessels obtained from angiographic images was also used for pre-operative planning. The point at which the perineum perforators branched from the superficial external pudendal artery were chosen to be the rotating point of the flap and its distances from the anterior superior iliac spine and the mid-pubic symphysis were also measured. This rotation point was marked on the body surface and the PTPF was designed and fashioned.Standard axial PTPF was designed with flap centering on the superficial pudendal artery. Point at which the superficial pudendal artery branched was localised by using the measurement of its distance from the ASIS and Midpoint pubic symphisis using a straight ruler and the pelvic measurement feet. The common ruler’s zero point was fixed on the middle of pubic symphysis with the length of measurement above, and the pelvic measurement feet’s zero point was fixed on the anterior superior iliac spine with the length of measurement above, and the other side of each ruler intersected on one point.Surgery was performed with patients in the lithotomy position. The sizes of the flaps ranged from9×4cm to15×5cm, depending on the size of the defect and the length of the required pedicle. Following the skin incision, flap was carefully elevated with particular care to not damage the axial blood supply, the perforators of superior pudendal artery. The flap was observed for10minutes to ascertain the adequacy of its blood supply and it is then positioned to cover the surgical defect.Patients received follow up observation up to8months after the surgery.ResultThere were4constant perforating arteries in the perineum:inguinal and perineal perforating branches of the superficial external pudendal artery, a perforating branch of the lateral branch of the posterior scrotal (pudendal) artery, and a perforating branch of the anterior cutaneous branch of theobturator artery. These perforating arteries and accompanying veins macthed up with each other and formed the upper, middle, and lower parts of the vascular anastomosis in deep fascia above the adductor wall. There were4 important cutaneous nerves in the region originating from the following nerves:the genitofemoral nerve, ilioinguinal nerve, posterior scrotum (labium) major nerve, and rami perineal esnervicutaneifemorisposterioris.The branch originated from the superficial external pudendal artery, and traveled medially. The branch typically originated from the inferior side of the great saphenous vein, and extended horizontally. It gave rise to many willow-like branches to supply the upper perineal region. After entering the scrotum (labium) from the lateral upper side, the branch turned inferiorly. The length of the artery was5.37±0.16cm. It supplied the upper one third of the scrotum (labium). The main stem anastomosed with the medial and posterior scrotal (labial) arteries.All patients were followed up (mean13.2months; range8to22months), and the flap sensation was assessed by self questionnaires and at the time of physical examinations. All38flaps were deemed viable at the completion of surgery. All patients in the case group recovered except2patient loss of flap sensation. In control group5patients had partial flap necrosis (both healed by secondary intention) and4patients had a temporary loss of sensation of the flap (spontaneously recovered after6months). Compare to control group, case group took on average11.54minutes less operative time, which could be confirmed by the non-paired t test with significance level<0.01(Table1). Besides, comparison of between the two groups also proved better postoperation satisfactions from the case group, as indicated by lower rates of sense loss, partial necrosis and complications (p<0.05).ConclusionThe perineum has abundant blood supply, venous return, and innervation. Due to its covert location and manuevor ability, perforator flaps from this region are good sources of donor tissue for perineal reconstruction.Preoperative assessment of the PTPF’s vascular anatomy using320-row MDCT angiography is a useful non-invasive procedure that allows surgeons to accurately visualize the vascular anatomy of PTPF and in creating a surgical plan. |
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