| Background:Facial paralysis is syndrome of autokinetic movement and functional incapacitation in emotional expression caused by surgical trauma,edema, inflammation,tumor and operation in which make irreversibility injury of facial nerve.Injury of facial nerve ultimately induces facial muscles to myatrophy, denaturation and nonfunctioning fibrous tissue.Patients with facial paralysis may experience several limitations.They may have difficulty with speech,eating and may experience drooling.Furthermore,these patients may have significant ophthalmic complications from loss of the blink reflex,upper and lower eyelid retraction and lagophthalmos.It is our challenging goal as reconstructive surgeon to reestablish facial symmetry,tone and coordinated animation of the paralyzed face.Several procedures to restore facial function had been advocated in the past.Complicated reconstruction of late facial palsy may need rectification many times.It is badly in need of uncovering ideal donor site to simultaneously repair upper 1/3 and lower 2/3 facial muscle function.With the development of microsurgical technique,neurovascular free-muscle transferd to treat facial paralysis has been a favourite procedure for facial animation. The donor sites include temporalis,latissimus dorsi muscle,gracilis,serratus anterior muscle,sternocleidomastoid,pectoralis minor and caput breve musculi bicipitis femoris.Wang wei utilized one-stage microvascular free transfer of the split latissimus dorsi muscle for reanimation of long-standing facial paralysis.The procedure was focused on the distortion of commissure.It was evaluated regarding symmetry and balance of facial tone at rest,sufficient muscle power upon voluntary contraction,synchronicity and naturalness of expression upon emotional facial movements,especially upon smiling,and given a score according to the Harii's Grading Scale.As a result,the operation provided a natural or near-natural smile.To overcome drawbacks of the two-stage method,Da Ping Yang used split rectus femoris muscle to reconstruct symmetric smile.To sum up,there is a broad spectrum of dynamic and static reconstructive techniques available to reanimate the paralyzed face,part of them was limited to clinical application.Although voluntary movement may be improved,no method restores the lost spontaneous involuntary movement associated with emotion.The suitability of each restorative technique is related to the location,cause,duration of the facial nerve injury and prognosis of the patients.Furtheremore,anatomy of donor muscle flap has intimate correlation with the effect of reconstruction.The latissimus dorsi muscle and serratus anterior muscle are not only characterized by oblique muscle fiber but also have abundant blood supply and long nerve pedicle.According to the reports,rectus femoris muscle and gracilis are more suitable to reconstruction of facial paralysis,in which consist of segmented distribution of vascular nerve. However,there are some unfavourable factors such as clumsy flap and hematoma muscle,which need surgical revision.Enough petty musle flap units profit to facial muscles reconstruction.So,the microdissection of latissimus dorsi muscle,serratus anterior muscle,rectus femoris muscle and gracilis is necessary.The clinical effect of surgical recovery from facial paralysis is influenced by many factors,among which blood supply of donor muscle plays an important role. Intramuscularly vascular anastomotic mode and blood-supply area irritating are mainly based on the range of perfused ink in blood vessel.Stereophotograph of micro-angioarchitecture can be demonstrated by scanning electron microscope. Vascular injection of a radiopaque medium is a rapid and precise technique,and the modified vascular injection technique with gelatin lead-oxide mixture,in particular, can provide excellent 2D images of the blood vessels subjected to X-ray.But the two-dimensional images cannot display the three-dimensional distribution and relationship of the intramuscularly blood vessels.The combination of anatomy, imageology,and computer technique makes it possible for 3D visualization of blood vessels.Focusing on the design of segmented muscle flaps,the methods of perfusing with red latex,modern technique in imageology and computer image processing are utilized to reconstruct of 3D models of intramuscularly blood vessels.The post-operated effect of surgical repairing facial paralysis is interesting to both the doctor and patients.In the procedure of muscle transfer,excess or poor contraction force of the donor muscle has disadvantages to expressional symmetry. Although the size and constriction of segmental muscle flaps have influences on the effect of reconstruction,it is hard to estimate pre-operation.Finite element analysis is the most effect method in simulating the contraction of soft tissue.Kober displayed the action of masticatory muscles with ANSYS software.Zhou Yiyi established the finite element models of eyeball and ocular muscles,exerted outside forces on the structure for nonlinear computation and got the distributions of displacement,stress and strain,discussed the relationship among eye's structure,outside force and move. The results corresponded with the basic theory of ophthalmologyand imulae their loads and movements according to their normal or abnormal status.By the methods of computer tomography,image processing,3D reconstruction wih CAD modeling and FEA,the construction of finite element model of complex transplanted muscleskin of lower face drived by constriction and displacement can be completed,and we will testify whether it can analyse the size and constraction of segmented muscle flap or not during sham operated.Objective:1.To provide morphology basis of latissimus dorsi muscle,serratus anterior muscle,rectus femoris muscle,gracilis and get segmental and combined muscle flaps.2.To explore the 3D model and design of segmented latissimus dorsi muscle, rectus femoris muscle,and gracilis muscle flaps.3.To set up finite element model of complex transplanted-muscle and skin of lower face driving by facial muscles,simulate and analyse the muscle contraction and displacement during sham operated.Method:1.Microdissection:The morphological features of latissimus dorsi muscle, serratus anterior muscle,rectus femoris muscle,gracilis were observed and measured on 20 adult cadavers,the following indexes were observed:distribution pattern of the intramuscularly artery,separated length of nerve branch,the relationship between the intramuscularly artery and nerve branch.The length and outside diameter of the artery and nerve branch were measured.2.3D reconstruction of artery in donor muscle,mark of nerve branch and design of segmented muscle flap:first,2 fresh adult cadaver specimens were perfused with modified lead oxide-gelatine mixture,then subjected to CT,and then the latissimus dorsi muscle,rectus femoris muscle,gracilis were dissected,scaned by computer tomography again.The images of CT scanning of the latissimus dorsi muscle,rectus femoris muscle and gracilis were digitally analyzed using MIMICS 10.0 software. The CT images were firstly segmented by using segmentation tools,such as thresholding,region growing,dynamic region growing,Boolean operations,edit masks to extract different tissues.Then the 3D models of latissimus dorsi muscle, rectus femoris muscle,gracilis and their arteries were reconstructed.The nerve branchs were marked according the microdissection to get 3D models of the muscles and intramuscular blood vessels and nerve branch.The 3D models of segmented muscle flaps were designed in 3D space,and the length,width and thickness of the neurovascular pedicle were measured.3.Finite element analysis:The dicom data of head and face got by computerized tomography was imported to Mimics10.0.Subdivision and 3D model of the skin of lower face was reconstructed.Subsequently,the 3D model of lower face and the model of transplanted-musle were calculated by lap joint.After seting up compound solid model of transplanted-muscle and skin of lower face,choosed the type of the unite,attribute of materials,divided free mesh and built finite element model of transplanted-muscle and skin of lower face.The efficacy of the finite element model was testified,exerted constrained condition by loaded with 27N muscle force and 8mm displacement in lenth wise.Then the effect of muscle constriction was observed,the area of cross section of transplanted-muscle was estimated in order to get good results in muscle transfer for facial paralysis.Results:1.Microdissection of latissimus dorsi muscle,serratus anterior muscle,rectus femoris muscle and gracilis:①The length of latissimus dorsi artery was 25.0±5.8 mm.The length of medial branch of latissimus dorsi artery was 24.8±6.0 mm and its origin outside diameter was 1.5±0.2 mm.The length of lateral branch of latissimus dorsi artery was 30.4±8.1 mm and its origin outside diameter was 1.8±0.3 mm.There were two types of artery attribution:balanced type and plumatus type.The segmented artery attributed to the segmented muscle flap.It consisted of the first medial segment,the second medial segment,the third medial segment,the first lateral segment,the second lateral segment,the third lateral segment,the fourth lateral segment.The outside diameter of segmental artery was over 0.5 mm and the medial segmented arteries were longer than lateral arteries.The thoracodorsal nerve had two funicles that independently innervated to the medial and lateral portions of the muscle at inferior angle of scapula.The rate of comitant relationship between artery and nerve branch was over 90%.②The muscle bundle of serratus anterior muscle was 25.7±2.9 mm,6.0±0.7 mm in width and thickness at starting point,while at the insertion was 20.7±3.0 mm and 7.9±0.7 mm.62.5 percent cases were consistently supplied by a single dominant branch of the thoracodorsal artery and innervated by the long thoracic nerve and 37.5%specimens were supplied by two branches of the thoracodorsal artery.The first and second serratus artery was respectively 2.0±0.5 mm,1.5±0.4 mm in outside diameter and 50.0±5.2 mm,57.1±6.3 mm in length.The laterigrade branch of long thoracic nerve was 3-10.The distance between lateral thoracic artery and long thoracic nerve was 48.0±6.3 mm,while it was 0-3.3 mm in distance between the terminal of long thoracic nerve and serratus artery.③The rectus femoris muscle consisted of three intramuscular vascular patterns: The rectus femoris muscle received a single vascular pedicle(5 percent),a dominant vascular pedicle,inferior artery of rectus femoris muscle(80 percent),or two dominant vascular pedicles,the superior artery or middle artery and inferior artery of rectus femoris muscle(15 percent).The rectus femoris nerve was 14.8±1.3 (12.7-17.9) cm in length and 1.6±0.2 mm in outside diameter.The superficial branch and deep branch of rectus femoris nerve was accompanied with anterior branch and posterior branch of rectus femoris inferior artery at the middle part of rectus femoris. 75 percent of specimens had middle neurovascular branch.④The blood supply of upper and middle 1/3 part of gracilis muscle came from deep femoral artery.The gracilis branch of deep femoral artery was 3.0(2.2～4.3) mm in origin diameter and 132.9(120.0～155.6) mm in length.The gracilis nerve was 1.9±0.3(1.3-2.6) mm in transverse diameter and 5.7±0.5(4.3-6.9) cm in length.The separated length of anterior gracilis nerve branch was 8.6±1.4(6.6-11.7) cm and the posterior gracilis nerve branch was 9.4±1.4(6.8-12.8) cm.There were 2 neurovascular tracts in 40 percents specimen and above 3 neurovascular tracts in 45 percents specimen.2.3D reconstruction of artery in donor muscle,mark of nerve branch and design of segmented muscle flap:①The transverse images of modified lead-oxide filled arteries had a distinct rim and a steady density.There were no obvious constructed defects like"burring","vacuolus"in the 2D images.The thresholding-based segmentation of the blood vessels was simple and accurate.Minute blood vessel in 0.5 mm can be displayed,segmented and measured.②the 3D model of artery were very clear,smooth and continuous.The modality,spatial location and the adjacent relationship of arteries and nerve branch were perfectly visualized.The 3D model also displayed the branching,distribution of the nerve branchs and their relationship with aretry.All reconstructed structures could be displayed separately,in a group or as a whole.They could also be shown in different color modes,transparent styles and various vascular densities by adjusting parameters.③The 3D models of segmented muscle flaps in latissimus dorsi muscle,rectus femoris muscle and gracilis displayed intramuscularly pedicle of blood supply,nerve branch and morphous of the muscle flap.The 3D model of segmented latissimus dorsi muscle flap demonstrated segmented artery of medial branch and lateral branch.It also reflected three-dimensional morphous of the muscle flap,in which the superior part of the first and second lateral segmented muscle flaps were thicker than the middle and inferior parts,and the medial part of the first segmented muscle flap was thinner than the second and the third segmented muscle flaps.The rectus femoris muscle was split into 2-3 segmented muscle flaps and the middle sub-muscle flap was shorter and thinner than the others.The gracilis can be split to anterior and posterior muscle flaps.3.The compound transplanted muscle and inferior prosopo-skin 3D finite element model consisted of donor muscle and inferior prosopo-skin,which had good geometric similarity with the entity image.The model can be rotated and zoomed arbitrarily,added and regulated the muscle.It had well arranged 2978 nodes and 10666 units,among them including 564 nodes and 1918 units.Loading with 27N,the biggest displacement in length was 3.9047 mm,while Loading with 8mm,the biggest muscle force was 55.431N,which whould get from transplanted muscle with 149.8mm area of cross section.Conclusions:1.Having an intimate knowledge of microanatomy about the latissimus dorsi muscle,serratus anterior muscle,rectus femoris muscle and gracilis had helpful for reconstruction of facial muscle with segmented units of these muscles.①With the pedicle of the segmented vascular nerve,the latissimus dorsi muscle was split to double sub-muscle flaps with single pedicle or double pedicles or three sub-muscle flaps with one pedicle.②With the pedicle of serratus anterior artery,serratus anterior muscle was split to 4-5 fascicularis muscle flaps.With the pedicle of latissimus dorsi artery,the combined latissimus dorsi muscle and serratus anterior muscle flap was designed.③The rectus femoris can be split to 2-3 segmented muscle flaps with the pedicle of rectus femoris nerve and artery.④The gracilis was split to 2-3 segmented muscle flaps with the pedicle of gracilis nerve and artery.2.The carboxymethyl cellulose-lead oxide was favourable material in blood vessel perfusion.With the arteriography and MIMICS software,3D reconstruction of intramuscularly artery had been succeeded.The 3D model of segmented latissimus dorsi muscle,rectus femoris muscle and the gracilis muscle flap can be used for design of muscle transfer.3.The complex 3D finite element model of the transfer-muscle and lower skin of face based on entity image and preoperative plan had good geometric similarity and mechanics similarity.It can be applied to quantify the design of pre-operation and evaluate the effect of free muscle transfer for the treatment of long-standing facial paralysis. |
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