The Clinical Application Of Mimics With CTA Assisting In The Accurate Preoperative Design Of Perforator Flap

Objective:To explore the clinical effect of Mimics with computed tomography angiography(CTA)assisting in the transplantation of perforator flap and the factors influencing the size of flap design,and compare the similarities and differences between traditional cloth sample and Materialise’s interactive medical image control system(Mimics)software design to provide effective theoretical basis for clinical preoperative accurate perforator flap design and individualized evaluation of treatment outcomes.Methods:Between January 2017 and December 2018,40 patients with skin and soft tissue defects due to limbs trauma who were about to undergo perforator flap surgery,20 of them had approximately planar wound surface and 20 of them had obvious radian surface.There were 27 males and 13 females,with an average age of 32.2 years(range,2-60 years).The time from post-traumatic admission to flap repair was 3-80 days(mean,20.8 days).The causes of injury included machine injury in 21 cases,traffic accident in 13 cases,heavy crush injury in 4 cases,fall injury in 1 case and treadmill abrasion in 1 case.The wounds were located at the dorsum of hand in 8 cases,the wrist in 5 cases,the forearm in 11 cases,the leg in 7 cases,the ankle in 1 case and the foot in 8 cases.All wounds in the recipient site were combined with the exposure of bone,muscle tendon,blood vessel or nerve.The size of wounds ranged from 6.0 cm×4.0 cm to 29.0 cm×7.0 cm.Preoperative CTA examination was performed to select the appropriate perforator and donor site.Computed Tomography is used to scan the recipient site preoperatively.After scanning,CTA and CT data were imported into the Imaging system In DICOM(Digital Imaging and Communications in Medicine)format,followed by Mimics20.0 system.After data import,the Mimics operation interface is divided into four parts:the coronal plane image on the upper left,the horizontal plane image on the upper right,the sagittal plane image on the lower left,and the 3D image displayed after 3D reconstruction of the tissue on the lower right.(1)three-dimensional reconstruction of the receiving area:on the operating interface of Mimics software,threshold segmentation was started,pixel gray value was adjusted,and all the bone,blood vessels,muscle,fat and skin in the horizontal image were covered to reconstruct the three-dimensional image of the receiving area.Then the 3D reconstruction data were saved in Parts format and imported into the 3-matic software.Mark was used to fill the defect area at the 3-matic interface.After successful filling,the contour of the defect area of soft tissue could be generated.After a series of operations,the defect area of soft tissue could be generated separately.The length and width of the defect area can be measured respectively,and the surface area and volume of the defect area can be calculated automatically by using the software.The thickness of the skin flap in the donor area can be measured by using the measurement tool provided by the software,and the defect area with thickness can be generated.Then the length and width of the defect area can be measured respectively,and the surface area and volume of the defect area can be automatically measured by the software.(2)establishment of three-dimensional visualization of the source of perforating blood vessels:on the Mimics software operating interface,threshold segmentation is started,pixel gray value is adjusted,and the threshold displayed by the blood vessels is selected to generate 3d images of the blood vessels.Then,the desired blood vessel regions are segmented and selected one by one.(3)muscle building:first,establish a new mask,find the starting and ending points of muscles in the horizontal image,mark the muscle boundary from the starting point to the muscle stopping point,then generate muscle images at all levels of the horizontal image,generate 3d images and conduct virtualization,and judge the direction of blood vessels.Results:All the 40 cases successfully established three-dimensional visualization models of recipient area,perforating vessel and muscle.Defects in the recipient area include thickness without thickness and thickness with three-dimensional visualization models of perforating vessels and muscles clearly showing their distribution,walking,type and perforating branches in the skin surface.We found that when the wound surface of the affected area was approximately flat,there was no statistical difference between the surface area of the traditional layout design and the Mimics design(P>0.05),and the thickness of the flap had no significant impact on the flap design.When the shape of the wound in the receiving area was significantly curved,there was a statistical difference between the surface area of the traditional cloth sample design and the Mimics design(P<0.05).The thickness of the flap and the wound curvature affected the design of the flap size in the donor area,and the donor and receiving area could not completely match.In 40 cases of skin flaps,76 perforating vessels were found in the preoperative three-dimensional reconstruction,including 58 perforating vessels of musculocutaneous and 18 perforating vessels of intermuscular space.During the operation,76 perforating vessels were found,including 58 musculocutaneous perforating vessels and 18 intermuscular perforating vessels.Preoperative and intraoperative outcomes of three-dimensional reconstruction of perforator blood vessels were evaluated by kappa coherence test,and the three-dimensional reconstruction of perforator blood vessels was consistent with intraoperative detection,with kappa coherence test=1.In the 40 cases,there are 38 cases anterolateral femoral flaps and 2 lateral upper arm flaps.The minimum area of the flap was 7.0*4.5cm2 and the maximum area was 31.0*7.0cm2.There were 38 cases with a single flap and 2 cases with split flap.The donor sites in 35 cases were directly sutured and skin grafting was performed in 5 cases.There is no additional damage to the second donor region due to mismatch of the recipient region.There was no vascular crisis in 40 cases.All flaps survived successfully after 8 weeks of follow-up.The patients were followed up for 3-6 months(3.8 months on average)after surgery.The color and texture of the flap were excellent,and the shape of the flap donor and recipient area was satisfactory.All the skin flaps survived successfully after the operation,and the recipient and donor areas of the skin flaps all healed in one stage.Conclusions:1.When the wound surface of the recipient site is approximately planar,the thickness of the flap in the donor site has no significant influence on the design of the flap size.2.When the wound surface in the recipient site has an obvious radian,both radian wound and skin flap thickness affect the design of skin flap size.The larger the radian,the thicker the skin flap is,and a larger area of skin flap is needed to cover the same wound surface.3.Three-dimensional perforating vessels can accurately determine the course of the vessel and provide a basis for clinical blood vessel separation.4.Mimics combined with CTA can realize accurate preoperative evaluation of perforator flap and realize the personalized design.