Improved Techniques In The Correction Of Orbital Hypertolerism In Rabbit Models And Clinical Applications

Orbital hypertelorism is a congenital condition in which the interorbital distance iswider than normal. Orbital hypertelorism is a sign, not a diagnosis, of a deformity andis found in craniofacial congenital clefts, as described by Tessier 0-14. It is also foundin some congenital syndromes such as Apert's or Crouzon syndrome. In acquireddeformities in which enlargement of the orbital distance is produced by trauma ortumor (0.5-0.8 million a year), the term orbital hypertelorism is not acceptablebecause there is displacement of the internal orbital walls and orbital content, but notof the orbit as a unit. The aim for the operation is to obtain a normal aestheticappearance, which minimizes the psychologic problemsof the patient. As proposed byTessier in 1967, on the basis of the interorbital distance, divided orbital hypertelorisminto three degrees, and report his first intracranial approach operation for third degreeorbital hypertelorism correction first time. It has been recognized the landmark ofcontemporary craniofacial surgery. The correction of third degree orbitalhypertelorism is always the most difficult and arguable operation in craniofacialsurgery. Intracranial-extracranial approach operation becomes the classic method inorbital hypertelorism correction. But, there are some defects in it. Relapse ofmalformations after operation is one of the common complications. The technics ofthis operation had becoming more and more consummate in the last 30 yearsdepended on develop of materials and computer techniques. M.H.Moor, doctor of Australian cranio-facial unit, used tissue expansion of adjacent and distant soft tissueto reconstruct rare orbital hypertelorism first time (1992). At the initial surgery, via acoronal incision, a 70cc expander was inserted subperiosteaUy in the region of thezygomatic arch and body. Six weeks later after expansion was completed, heunderwent transcranial correcton of the orbital hypertelorism. Orbital translocationwas achived without tension, allowing accurate localization of the orbital soft tissues.As proposed by Moor, successful bone grafting demands an adequate surroundingvascularity and soft tissue envelope free from tension, conditions frequently deficientin the cleft tissues. Tissue expansion provides for both increased vascularity and atension-free environment into which bone graft can be placed. Indeed, sequentialtissue expansion may be the ideal adjunct to the required staged bone grafting andosteotomy. Based on these results and experiences, we established and evaluated theplastic and reconstructive models of orbital hypertelorism in rabbit first time, andexplored the effect of para-orbital soft-tissue expansion before orbital osteotomiesand medial translocation by combined intracranial-extracranial approach in rabbitmodels. We applicated these improved techniques include para-robital soft-tissueexpansion in two patients in clinic to prevent relapse of malformations of orbitalhypertelorism after operation. The patients are followed by three diamensionscomputer tomography (CT) for more than 2 years.Objective1,To establish the correction models of orbital hypertelorism in rabbit. Givepara-orbital osteotomies and medial translocation. Interorbital distanse (IOD) andHealing of the bone between orbital were studied with gross measurement and X-rayexamination before and after operation and 12 weeks later.2,Investigate the effect of para-orbital soft-tissue expansion before orbitalosteotomies and medial translocation by combined intracranial-extracranial approach.IOD and healing of the bone between orbital were studied with gross measurement,X-ray, and histological examination before and after operation and 12 weeks later.3,Applied para-orbital soft-tissue expansion technique in 2 orbital hypertelorismpatients based on the experiences of rabbit operations. To explore the effect of para-orbital soft-tissue expansion before orbital osteotomies and medial translocationby combined intracranial-extracranial approach.Methods1,16 New Zealand rabbits were given para-orbital osteotomies and medialtranslocation by combined intracranial-extracranial approach. The coronary, palpebral,and nasofrontal incisions are necessary to expose the craniofacial skeleton. Leavingthe periosteum intact in the frontal area as far as 0.5-1.0 cm from the orbital rim andcontinuing underthe periosteum in the orbital and malar regions. The bone blocks tobe resected can be performed by an ethmoidofrontal resection with a frontal crown toprovide a base for bone graft fixation. A resection of the ethmoid cells leaving acentral T shape in the nasofrontal area to rebuild the dorsum of the nose, and 0.5cmbone graft were resected beside the T shape. Osteotomies separate the whole orbitfrom the skull and facial bones in order to mobilize the orbit medially. Finally, fixthese bone graft with steel wire. IOD and Healing of the bone between orbital werestudied with gross measurement and X-ray examination before and after operationand 12 weeks later.IOD were measured by vernier caliper before and after operation, IOD is the distancebetween lacrimonasal crests. Execute the rabbits 12 weeks after operation, andmeasure IOD again. Give X-ray examination before and after operation and 12 weekslater. Make histological examination to the bone between the orbits after execution.2,16 New Zealand rabbits were divided into two groups randomly. In experimentalgroup, para-orbital soft-tissue expansion was given before orbital osteotomies andmedial translocation, a 30ml expander was inserted subperiosteally in the region ofthe zygomatic arch and pars temporalis.10 ml water injected through the spigot of theexpander a week. No soft-tissue expansion in the contrast experimental group. 12weeks after the correction operation, IOD and healing of the bone between orbitalwere studied with gross measurement, X-ray, and histological examination before andafter operation and 12 weeks later.In experimental group, para-orbital soft-tissue expansions were given before orbitalosteotomies and medial translocation. 30ml tissue expanders with remote reservoir domes were used in all instances. Put the expanders under periosteum around theorbit. Inflation begins after the operation; the amount of fluid injected isindividualized about 30 ml. Orbital osteotomies and medial translocation 2 weeksafter the last inflation.3,Tissue expansion in the region of the zygomatic and temporal has been used 3weeks before traditional intracranial-extracranial approach orbital osteotomies andmedial translocation in two patients. At the intial surgery, via a coronal incision, a100ml expander was inserted subperiosteally in the region of the zygomatic arch andpars temporalis. Avoid damage branches of facial nerve in this operation. 10-15 mlwater injected through the spigot of the expander 2 or 3 days. Three weeks later afterexpansion was completed, the first patient expanded to 112ml, and the second patientexpanded to 82ml. They underwented improved technique correction of orbitalhypertelorism. Classic osteotomy includes total resection of the ethmoid, the nasalseptum, and the central area of the frontal process of the maxilla. We modified theprinciples of this technique, changing the line of osteotomies to avoid bone graftsdrift, which in our opinion are the main problem in the final result. The design of theosteotomy is for 4 objects: (1) Resection of the abnomal part between orbits, includesthe ethmoid, the nasal septum, and the central area of the frontal process of themaxilla. (2) Three-dimensional osteotomy based on functional orbit. (3) Orbit medialtranslocation. (4) Bone graft in the lateral orbtit and rebuild the dorsum of thenose.we had no special difficulty in moving the orbial cavities, even by nore than0.3cm. The skin resection depends on the amount of displacement of the orbit, andalso depending on what the deformity of the base of the nose. The healing of the bonebetween orbital were studied with measurement of interorbital distance andthree-dimensional CT.Results1,The average IOD of the rabbits is 2.39cm before operation and 1.15cm afteroperation. 12 weeks after operation, the average IOD of the rabbits recurred to1.36cm. The relapse is significant, P＜0.001 ((?)±s, n=16).. 2,At the 12th week after correction operation, the IOD of the para-orbital soft-tissueexpansion group were 1.15cm and were 1.34 cm in the other group on average. Thereis significant difference in statistics, P=0.045＜0.05 ((?)±s, n=8). More new bonewas observed in the non-soft-tissue-expansion group.3,The two patients have no complications such as blindness or corneal ulcerations,no metabolic and pulmonary problems. The healing of the bone between orbital werestudied with measurement of interorbital distance and three-dimensional CT. Theinter-orbital distance of the two patients decreased from 4.4cm and 3.2cm to 2.0cmand 1.4cm. The intercanthal distance decreased from 6.7cm and 4.8cm to 5.0cm and3.8cm.Conclusion1,Rabbits have hemispheroid orbits and very like human's position. We can applyorbital osteotomy and medial translocation conveniently. The healing of bone afterosteotomy is very fast in 4-6 month old rabbits. We can observe the bone grafts afterosteotomy conveniently. There is significant relapse of the IOD after the orbitalosteotomies and medial translocation by combined intracranial-extracranial approachin rabbit models. Rabbit is ideal model used for orbital osteotomy operations.2,The para-orbital soft-tissue expansion technique may be an effective technique forthe stability of the corrected IOD in orbital hypertelorism. Lack of soft tissue aroundorbit can result in relapse after hypertelorism correction. The para-orbital soft-tissueexpansion technique may help prevent the relapse of orbital hypertelorism aftercorrection.3,The para-orbital soft-tissue expansion technique may be an effective technique forthe stability of the corrected interorbital distance in orbital hypertelorism. Preparatoryexpansion of these distant soft tissues, ideally in a subperiosteal plane, permitstension-free bony shift, the potential for accurate repositioning of those importantperiorbital soft tissue landmarks (medial and lateral canthi) and the production of anappropriately orientated and functional eyelid reconstruction. Exsect the soft tissuebetween orbitals thoroughly and fix the medial canthi ligaments firmly can acquired perfect external appearance after operation. Long-term follow-up with subsequentfacial growth is not available, but in the presence of an underlying stable facialskeleton, soft tissue contracture would not be anticipated.