| [Research background]At present,the anatomical study of the perioral region focuses more on muscles and blood vessels and less on the peripheral nerve distribution.This is mainly because the tissues in the perioral region are dense,especially of the upper and lower lips,and the nerves distributed here are the distal ends of the peripheral nerves,and it is very difficult to separate them from the dense tissue in gross anatomy.However,the perioral region is a common area of surgical operation.For plastic surgeons,a better understanding of the distribution of nerves in the perioral region would lead to a better and more specific implementation of surgery.[Objective]A modified Sihler' s staining technique was used to stain the peripheral nerves while making the perioral tissue transparent,so as to better understand the distribution and courses of the peripheral nerves and the spatial structural relationship between nerve branches in the perioral region.[Materials and methods]Two fresh elderly male cadavers without facial deformities were selected.The soft tissues of the lip and cheek were cut and fixed with 10%formalin solution for 1 month,and then dyed with Sihler' s stain(Maceration and depigmentation,Decalcification,Staining,Destaining,Neutralization,clearing)to observe the distribution and courses of the peripheral nerves.[Results]1.The infraorbital nerve(ION):after emerging from the infraorbital foramen,the infraorbital nerve traveled in a tortuous path and divided into the inferior palpebral(IP),external nasal(EN),internal nasal(IN),medial superior labial(SLm),and lateral superior labial(SL1)branches.The EN branch sent out secondary branches in its course and distribute in the upper,middle,and low aspects to innervate the ala nasi area.The IN branch traveled along the ala nasi to the nostril sill and turned upward to innervate the philtrum and vestibular areas of the nose.The SLm and SL1 branches entered the upper lip from the upper and lateral directions,respectively.Consistent with the superficial muscle distribution in the upper lip,the SLm branch moved inward and downward along the philtral ridge,and the SL1 branch moved inward and downward directly to the edge of the vermilion border of the lip.Moreover,the SLm branch traveled from the infraorbital foramen to the superficial layer of the orbicularis oris muscle,while some of the SLl branch fibers ran in the deep layer of the orbicularis oris muscle.The infraorbital nerves on both facial halves were symmetrical and the fine terminal rami did not cross the midline of the face.2.Facial nerve branches(FN):the zygomatic and buccal branches of the FN moved in an angled straight line from the lateral edge of the infraorbital nerve to innervate the upper lip.The nerve fibers ended in the upper part of the upper lip and in the lateral edge of the ala nasi and were mostly located superficial to the infraorbital nerve.The marginal mandibular branch of the FN ran into the lower lip from the lateral edge of the mental nerve in an angled straight line and divided into several branches distributed in the lower lip and chin.The nerve fibers distributed in the lower lip were consistent with the depressor labii inferioris muscle,and the nerve fibers distributed in the chin had a scattered distribution in the mentalis muscle.The nerve endings of the zygomatic and marginal mandibular branches were few in the lower part of the upper lip and in the lateral oral commissure.The facial nerves on both facial halves were asymmetrical their branching patterns.The fine terminal rami did not cross the midline of the face.3.Mental nerve(MN):after emerging from the mental foramen,the mental nerve travels tortuous paths and divides into the angular(A,mouth corner region),medial inferior labial(ILm,medial half of the lower lip),lateral inferior labial(IL1,lateral half of the lower lip),and mental(M,mental region)branches.The mental nerves on both facial halves were symmetrical and the fine terminal rami did not cross the midline of the face.4.Buccal nerve(BN):the BN traveled in the deeper layer of the cheek,gave off superficial branches and deep branches.The superficial branches anastomosed with the buccal branch of the FN to forms CBN.The deep branches distributed in the upper lip,lower lip and the corner of the mouth.This research suggested that there were two cases of the buccal nerve distributions in the upper lip:1.The BN went forward to the oral commissure and divided into several branches to innervate the corner of the mouth,upper lip,lower lip.The superficial branch that anastomoses with the buccal branch of the facial nerve on the surface of the buccal muscle.The branch to the upper lip traveled in the deep layer of the muscle in the inferior part of the upper lip;2.The BN traveled to the oral commissure and divided into several branches to innervate the corner of the mouth,upper lip,and lower lip.The branch to the upper lip anastomosed and traveled with the buccal branch of the FN and innervated the superficial layer of the muscle in the superior part of the upper lip.5.Spatial communication between the FN branches and trigeminal nerve branches:this research suggested three types of communication between the FN branches and trigeminal nerve branches:a spatial crossover relationship,an anastomotic relationship,and a communicating relationship where the nerve branches intersected and shared a length of myelin sheath.The relationship between the BN and the buccal branch of the FN was anastomotic.The relationship between the branches of the FN were anastomotic.The relationship between the infraorbital nerve and the branches of the FN and that between the mental nerve and the branches of the FN were mostly crossover.[Conclusions]Using modified Sihler' s staining technique,we vitrified the surrounding tissues while staining the peripheral nerves in the perioral region.The three-dimensional distribution and movement of the facial nerve and trigeminal nerve branches,along with the spatial structural relationship between these nerve branches were clearly displayed.It could serve as a guide for studying the physiological function of the facial nerve,local anesthesia,surgical operation,and local injection of botulinum toxin.[Research background]The corner of the mouth is the junction of the upper and lower lips where the skin joins the oral mucosa and forms an oral commissure.The oral commissure has diverse shapes,with great individual differences and dynamic and static changes.The anatomy of the surrounding muscles is complicated,which makes it difficult for us to find the corresponding anatomical reconstruction basis when performing surgery in the corner of the mouth.Can we find some anatomical features from these complex relationships and provide some new ideas for clinical surgery?[Objective]To find the anatomical features of the muscles at the corner of the mouth using iodine staining,micro-computed tomography scanning,and gross anatomy and to guide the surgical repair of macrostomia.[Materials and methods]1.Lip-cheek tissues were cut from aborted fetuses without facial deformity,the tissues were fixed in formaldehyde solution for 24hours,then soaked into the Lugol's solution for 7days.Finally,the two specimens were studied through Micro-CT scanning and clear images were acquired.Save the images as Dicom format and import into Mimics for observing and editing the running course of small muscle fibers,and a three-dimensional structure model of the muscles at the corner of the mouth was established.Then the results of CT scanning were verified by gross anatomy of the oral commissure in 2 fresh adult male cadavers.2.Based on the anatomy of the pars marginalis of the orbicularis oris muscle and the buccinator muscle,the methods of muscle reconstruction in the repair of macrostomia were improved.The pars peripheralis and pars marginalis flaps of the orbicularis oris muscle were separated at the upper and lower cleft edges.First,the pars peripheral is flaps were sutured end-to-end to close the cleft.Second,the pars marginal is flap in the lower cleft edge was sutured upwards and outwards and fixed in the deep layer of the pars peripheral flaps.Finally,according to the position of the contralateral corner of the mouth,the pars marginalis flap in the upper cleft edge was laid over the lower lip muscle to construct a new oral commissure.(Results]1.The results of anatomy:The specimen soaked in Lugol's solution exhibited clear muscle fibers upon imaging.In the 2D slice images,the muscle fibers show up as bright white filaments.By reviewing continuously obtained images,the orbicularis oris muscles were observed to be divided into two parts:the pars marginalis and the pars peripheralis.The former is a bundle of muscle fibers located in the vermilion border of the lip,while the latter has a flat-fan shape and is located in the deep layer of the upper lip.the muscle fibers of the pars marginalis were connected with the buccinator muscles.The 3D model of muscles clearly indicated a spatial relationship between the two.The muscle fibers of the pars marginalis travel inward and downward along the red lip margin towards the oral cavity from the vermilion tubercle to the mouth corner before finally integrating into the muscle fibers of the buccinator muscles at the mouth corner.The gross anatomy verified the findings of Micro-CT scanning.2.The results of clinic operation:In total,17 patients underwent modified muscle reconstruction to repair macrostomia.All incision wounds were primary healing,and the oral commissure curled inward towards the oral cavity in postoperative patients,which showed a more natural-appearing oral commissure in dynamic and static situations.[Conclusions]Based on the anatomical characteristics of the pars marginalis of the orbicularis oris muscle and the buccinator muscle,a modified three-dimensional muscle reconstruction method was performed in the repair of macrostomia,and the reconstructed oral commissure curled inward towards the oral cavity,providing a more natural appearance. |
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