Study On Anatomy Of Medial Canthus Related To Medial Canthus Relaxation And Its Clinical Application

BackgroundLower eyelid relaxation correction is a kind of surgery to correct lower eyelid ectopia through surgical intervention of lower eyelid skin,muscle,supporting ligament and other soft tissues,so as to improve the normal eyelid relationship,and to ameliorate symptoms of eyes.With the aggravation of the aging society and the improvement of the requirements for the quality of life of the elderly,the demand for eyelid relaxation correction surgery is gradually increasing,which greatly improves the market potential of eyelid aestheti surgery.At present,the surgical approach orthopaedic surgeons mostly useing to correct lower eyelid relaxation is to deal with the lateral canthus,such as lateral fixation or lateral canthopexy.However,for patients with medial canthus relaxation,deal with the lateral canthus merely may lead to lateral lacrimal punctum malposition,excessively high of the lateral canthus angle,too large inclination Angle of the palpebral fissure and undercorrection,which may aggravate the medial canthus relaxation in the long run.In recent years,the treatment of lower eyelid relaxation by orthoplasty of medial canthus alone or combined with lateral canthopexy has got well curative effect.However,at present,there are relatively few literatures on the anatomy of the medial canthus among scholars from domestic and abroad,especially fewer literatures on the anatomy and histology related to the relaxation of the medial canthus,with insufficient understanding of the relaxation and few surgical approach,resulting in great difficulty in correction of the relaxation of the medial canthus,big trauma,complex operation and many complications.The purpose of this study is to clarify the relationship between the tissue structures of the medial canthus and analyze the main factors to maintain the stability of the medial canthus through the analysis of the anatomical and histological of specimens,and the measurement clinical observation data of specimens.The characteristics of histological changes at the middle and old age levels were compared and analyzed,and the clinical data of medial relaxation were collected for statistical calculation,so as to analyze the causes of medial relaxation and explore new approach of medial relaxation correction surgery,so as to provide a scientific basis for the construction of a safe path for medial canthus correction surgery.Methods1.Gross Anatomical StudyTwelve head cadavers of Chinese Han adults fixed with formaldehyde were selected(24 cases in total,all of which were fixed with 10% formalin,including 8 males and 4females,aged 40-78 years old)(by Naval Military Medical University)Provided by the Department of Anatomy).For 6 specimens(a total of 12 cases,8 males and 4 females),the orbital specimens below the eyebrow arch and above the infraorbital foramen were intercepted.The gross specimens were grouped according to age,with 4 middle-aged cases(age: 40-60 years old)and 8 elderly cases(age: 60-78 years old,subject to the age limit of specimens,young specimens are extremely difficult to obtain).The specimens subjected to layer-by-layer elaborate anatomical study.First,observe the interrelationship among the punctum,tarsal plate,tarsal plate-medial canthal tendon extension fiber(TP-MCT extension fiber),and meidal canthal tendon(MCT),and observe the lacrimal duct system,orbicularis oculi muscle(OOM),medial rectus muscle through further dissection to illustrate the relationship between muscle,Check ligament and other supporting structures relative to the MCT.At the same time,apply an lateral force to the tarsal plate to simulate the relaxation of the medial canthus,observe the elastic deformation of the fibers at the extension of TP-MCT extension fiber and the MCT,the MCT and the fibrous ligament at the nasal attachment of the MCT with mechanical changes,and observe the fibers.The elasticity of connective tissue is further analyzed for the attribution of aging.2.Histology StudySix specimens(a total of 12 cases,4 males and 8 females)were grouped according to age,with 6 middle-aged cases and 6 old-aged cases.Perform general anatomy of the medial canthus in vitro.Partial specimens were taken from the punctum(tarbium-fibrous attachment),the middle section of the TP-MCT extension fiber,the fusion of the medial canthal angle tissue,the middle section of the MCT,the anterior lacrimal crest,and the posterior lacrimal crest.Histological sections were stained with HE,Masson,elastin and fibrin to observe the changes of microstructure,histological composition and related proteins with aging from the histological level.3.Comparative study of medial canthal relaxation in middle-aged and elderly peopleVolunteers are recruited and divided into middle-aged(aged 40-60 years old)and elderly(aged 60 years and older).The distance from fusion point of the MCT-periosteum to the medial canthal angle,the fusion point of the MCT-periosteum to punctum and the distance between the medial canthal angle and the punctum,and the medial canthal relaxation assessment method is used to collect the above data,and the horizontal and vertical contrast analysis of the changes in the degree of relaxation of the key segments of the medial canthal after being stretched and The rate of change of the laxity of the medial canthus at different stages of the two age levels;the snap-test and the medial canthal traction test were used to evaluate the lower eyelid laxity of the subjects at the same time.4.Comparative study of medial canthal relaxation in middle-aged and elderly peopleBased on the above anatomical and histological results,elaborated description of the medial canthal space structure,especially the location of important structures,to design the surgical approach and path,and explore some clinical work.Results1.Anatomical StudyThrough the layer-by-layer anatomical observation and study of the medial canthus of the specimens,it was found that:(1)The fibrous tissues from the nasal tarsal plate and the medial edge of the tarsal plate are fan-shaped,that is,TP-MCT extension fiber.The superficial layer is the orbicularis oculi muscle,and the deep layer is the lacrimal duct.They are easily separated.This fiber runs to the medial side and merges with the MCT at the medial canthal angle.The function of the fiber at the extension of the tarsal plate and medial canthal is to suspend the tarsal plate on the MCT.The tissue is relatively loose,easy to be stretched,and charactrised by relatively high texture and organization loose.(2)The starting part of the medial canthal tendon at the medial canthal angle consists of the TP-MCT extension fiber,the medial rectus fascia sheath(Check ligament),orbital septum,Lockwood’s ligament,palpebral sac fascia and other supporting structures.Converging,walking towards the nose in a cone shape.The medial canthal ligament is divided into superficial and deep parts.The superficial part is attached to the anterior lacrimal ridge of the nasal bone and the frontal process of the maxilla,and the deep part stops at the posterior lacrimal ridge and surrounds the lacrimal sac.The MCT is attached to the upper and lower orbicularis muscles,which fix the fascia ligament tissue in the medial canthal area fixed on the periosteum.The MCT of middle-aged and elderly specimens are relatively inelastic,with dense tissues and not easy to stretch.(3)After anatomy,it was found that the lacrimal punctum is located on the inner side of the nasal border of the tarsal plate,deep in the extension of the TP-MCT extension fiber,close to the conjunctiva,the lacrimal duct sneaks inward on the superficial surface of the conjunctiva,and the upper and lower lacrimal ducts converge into Common lacrimal duct,the common lacrimal duct merges into the lacrimal sac between the superficial and deep surface of the medial canthal tendon,and the superficial branch of the MCT is closely related to the lacrimal duct and lacrimal sac.2.Histology section(1)The TP-MCT extension fiber are located on the superficial surface of the lacrimal duct,the medial side of the tarsal plate,and stop at the medial canthal angle.It is composed of fibers and muscle cells from the nasal tarsal plate and the lateral edge of the tarsal plate.It is rich in orbicularis oculi muscle(OOM)cells,collagen fiber bundles,and elastic fiber filaments,which are both tough and elastic.(2)Lacrimal duct and lacrimal sac: The lacrimal duct is located on the inner side of the tarsal plate,the deep fiber surface of the extension,the vertical part and the horizontal part are close to the conjunctival surface,and at the lacrimal caruncle,the upper and lower lacrimal ducts are close to each other and converge into the main lacrimal duct.,Into the lacrimal sac.There are circular thick layers of collagen fibers and orbicularis oculi muscle,a little elastin to protect the lacrimal duct.The so-called Horner muscle runs deep behind the canthal tendon in the posterior wall.The surrounding muscle cells,the surface and deep Horner muscle of the lacrimal sac,and the cilia in the lumen together play the role of suction by the tear pump and drainage of tear fluid.(3)The fusion of the MCT is located on the inner side of the lacrimal caruncle,and it wraps the lacrimal sac in a triangle shape.It contains a large number of muscle cells,thick collagen fibers,elastic filaments interspersed,the deep fibers of the MCT are more slender,dense and fine,divided into two layers,shallow and deep,the shallow layer is thinner,located on the superficial surface of the front wall of the lacrimal sac,and the deep layer is thicker,Close to the posterior wall of the lacrimal sac;the superficial fiber is thicker and slightly sparse,and it is not composed of pure connective tissue,which is consistent with the stout collagen fibers of the MCT.(4)The anterior OOM cells are loose,and more lymphatic ducts and blood vessels can be seen in the gap.The muscle cells at the TP-MCT extension fiber are relatively loosely arranged,the collagen fibers are slightly thin,and the mesh-like connective tissue contained is relatively abundant,the MCT muscle cells are densely arranged,the collagen fibers are thicker,and the mesh-like connective tissue is less.The aging soft tissue collagen and elastin are relatively sparse,and the broken fiber ends can be found more easily,and the lymphatic vessels are denser than those in the middle-aged group.3.Comparative observation of medial canthal relaxation in middle-aged and old peopleAfter clinical data collection,using independent sample t-test,the results showed: the distance from the punctum to the medial canthal angle in the middle-aged group and the elderly group is D1,the distance from the medial canthal angle to the fusion of the medial canthal periosteum D3,and the medial canthal angle to the periosteum after stretching.There was no statistically significant difference in the distance between the fusion point D4,the distance from the lacrimal punctum to the medial canthal periosteum fusion D5,and the distance D8 from the medial canthal angle to the medial canthal periosteum fusion before and after stretching,while the distance from the lacrimal point to the medial canthal angle D2 after stretching There are statistically significant differences in the distance between the lacrimal punctum and the fusion of the medial canthal periosteum after stretching D6,the distance from the lacrimal punctum to the medial canthal angle before and after stretching D7,and the distance between the lacrimal punctum and the fusion site of medial canthal periosteum D9 before and after stretching.The snap-back test of elderly patients with medial canthal looseness shows that the rebound speed is slow.In severe cases,the blepharoplasty is separated at the beginning of the rebound,and it fits and recovers after blinking.3.Design surgical approachThis subject designs surgical plans on the basis of anatomy and histology:Option 1: Transcutaneous double small incision method: Step(1)Make a 0.5cm small skin incision 2mm below the eyelid gray line and lateral the lacrimal punctum and 0.5cm small skin incision in the middle of the medial canthal tendon,and 4-0 double needle suture on the nasal side Insert the needle into the upper edge of the tarsal plate,sneak into the superficial fibrous layer or subcutaneous layer at the extension of the tarsal-inner canthal tendon,and take out the needle at the TP-MCT extension fiber at the medial canthal angle.The subcutaneous layer between the submarginal incision and the fusion of the MCT strenuously forms a subcutaneous tunnel,and the appropriate length of autologous tissue is used to suture and fix the tarsal plate and the medial canthal tendon;step(2)cross the needle through the fusion site and insert it inside The upper edge of the superficial part of the canthal tendon sneaks,and the needle is drawn at the periosteum of the anterior lacrimal crest to correct laxity without valgus or mild to moderate laxity.Option 2: Deep fixation through three small incisions of the skin: Step(1)Make a0.5cm small incision the 2mm below the eyelid gray line and lateral the lacrimal punctum.Make a 0.5cm small incision on the skin edge of the medial canthal horn and the upper edge of the fusion of the MCT periosteum.A small incision is made in the superficial fibrous layer or subcutaneous layer of the TP-MCT extension fiber,to the fusion of the MCT and the needle,knotted and fixed,pay attention to stay away from the lacrimal caruncle,close to the skin,or make an incision under the eyelid margin.The subcutaneous layer is struggling to form a subcutaneous tunnel between the incision and the fusion of the MCT beneath the medial canthal angle,and the appropriate length of autologous tissue is used to suture and fix the tarsal plate and medial tendon fusion;step(2)The needle is inserted obliquely upwards and inward at the fusion site,sneaking in the meridian The deep upper edge of the medial canthal tendon is needled at the canthal tendon-periosteal fusion in the posterior crest,which is used to correct severe laxity.ConclusionsBy research,we have found that the key cause of medial canthal relaxation is the relaxation of the extending fibers between the tarsus plate and the MCT.General anatomical experimental studies have found that the fibers here are relatively loose,easy to be stretched,and have a looser texture.They contain muscle cells and collagen.Fibers and elastic fibers,with aging phenomena such as breakage of elastic fibers and collagen fibers may occur.The MCT also contains the above three components,but the muscle cells and fibers are densely arranged,and the fibrous tissue is thick and deformed when stretched.It is not obvious.In clinical studies,we further confirmed that this is the key part of relaxation;at the same time,we have described the spatial anatomy of the medial canthus in detail through layer-by-layer anatomy.When designing and implementing an improved surgical plan,the surgeon has a level in mind.We preliminarily imagined two surgical approaches:(1)fixation via the tarsal plate-fusion of the MCT-superficial periosteal attachment of the MCT;(2)fusion of the tarsal plate-fusion of the MCT-deep MCT fixation of periosteal fusion.The two programs can not only ensure the efficiency and effect of the operation,but also protect the important lacrimal duct,extend the indications for the operation of the inner canthus,and have certain clinical research and clinical practical application value.