Anatomic And Clinical Study In Exposure And Fixation Of Craniovertebral Junction Though Transoral Approach

BackgroundThe malformation, injury, inflammation and tumor of atlantoaxial joint usually cause disability, or even dislocation of atlantoaxial articulation. The former can lead to fateful acute spine cord injury, and the latter release normally cause chronic upper cervical myelopathy, both of these results needed surgical therapy. Posterior approach operation was adopted in the past time, but it can not afford satisfied reduction for irreducible atlantoaxial dislocation. The routine method to deal with this kind of patients is to resect odontoid process and solution the scar before the posterior approach operation. However, after transoralpharyngeal resection of odontoid process, the patient's body need to be turned from supine to pronate, the spine cord could subject to high risk of fateful injury under this disability circumstance. A new kind of transoralpharyngeal atlantoaxial reduction plate (TARP) system, which was designed and exploited by Dr. Yin Qing-shui, et al, make a great achievement to solve this problem. The TARP system can reduce the dislocated atlantoaxial joint by distinctive mechanism after solution and decompression by transoralpharyngeal approach, and then fix the atlantoaxial articulation in normal anatomic position. This system creatively perform the decompression, replacement and fixation of atlantoaxial jointat one-stage transoralpharyngeal operation, which can avoid the risk in turning body and surgical trauma of posterior operation effectively. Whereas, there is seldom anatomic report about the ventral structure of atlantoaxial articulation and transoralpharyngeal approach plate. This study aimed to prove anatomy evidence of transoralpharyngeal atlantoaxial reduction plate fix operation, and to assist more effective exposure, more successfully reduction, less surgical trauma, and less surgical course.Craniovertebral junction (CVJ) is a special area, where is complicated structure, multiple pathological changes, and deep seated location. Epidural ailment of this area usually cause the ventral compression to brainstem and upper cervical spine cord. But this area is normally thought as a restricted zone, because of the hardness of exposure, difficulty of operation, and the high risk of surgery. The normal approaches are very long and the drawing of brain can not be avoided, which always lead to edema and trauma of brain tissue. Furthermore, the ailments on the midline of the cranial bases, (includes: clivus, ventral brainstem, foramen magnum, anterior part of atlantoaxial articulation, and ventral upper cervical spine) can hardly be exposed by these approaches. There is a large cavity of mouth before this area, and no important structure on transoral approach. Therefore, the transoral approach can reach and resect the tumour on cranial bases directedly, avoiding the influence of brainstem. So this approach is a suitable method to settle cranial-cervical junction ailment. Simple transoral approach can not expose the upper two-third of the clivus. To achieve more satisfied exposure, extensive transoralpharyngeal approach is imperative. Another aim of this study is to afford anatomy evidence of extensive transoral approach, to observe the hierarchical structure, blood vessel, nerves, and variation of anatomic structure, and to compare the different degree of exposure between the simple transoral approach and extensive transoral approach.Objective:1. Imitating of the transoralpharyngeal atlantoaxial reduction plate fix operation on cadavers, and measurement of the important anatomic data in this operation, so as to assist the surgeons to know how they can get more effective exposure, more successfully reduction, less surgical trauma, and less surgical course.2. Measurement of the osseous structure on atlas and axis, and statistic analysis of these results, so as to prove suggestion about how to improve the parameter of plate, screws, and operating instruments in transoralpharyngeal atlantoaxial reduction plate system.3. Imitating of the extensive transoralpharyngeal approach operation on cadavers, and measurement of the important anatomic data in this operation, in order to evaluate the amplification of exposure in extensive transoral approach, and to guide surgeons which approach is more directly and effectively to deal with those ailments located from clivus to upper cervical.4. To review the patients who had been performed TARP system operation, in order to summarize the indication, therapeutic effect, and experience of this kind of operation.Materials and Methods:1. TARP and all the screws were made from titanium-aluminum-vanadium alloy (T16AI4V) and operating instruments were made from medical stainless steel. The design scheme was completed by Dr. Yin Qing-shui, et al. The company was responsible for manufacture of the plate and the operating instruments.2. Thirty cadaveric bodys soaked by formalin and six fresh cadaveric heads were used in this study (supplied by anatomic department of NanFang medical university), the arteriors of all these specimens had been poured into red emulsion, but birthplace and age of all these specimens are unknown.3. transoralpharyngeal approach anatomy: According to the normal procedure of transoralpharyngeal approach operation, these cadaveric heads were fixed on the table, and then, we drafted the oral cavity by Codman retracter and exposed posterior pharyngeal wall. All layers of anatomic structures were observed and measured, which have relationship with TARP operation. We used the software: SPSS 10.0 to study all the data of important structures, and figured out the "safe region" in TARP immobilization, moreover afford parameter for plate, screws, and operating instruments of TARP system.4. Extensive transoral approach anatomy: Extend incision on the base of foregoing transoralpharyngeal approach surgery. Each specimen was tested in the following two steps: (1) extensive discision of soft palate and hard palate; (2) extensive discision of maxillary bone. Important data of both steps were measured, and the different exposed ranges of the two kinds of approach as were compared.5. To review the ten patients who had been performed TARP system operation, and to compare and analyse the symptoms, signs, and image document in perioperation.Results:1. Measurement of transoralpharyngeal approach is compose of two parties: the depth and the width: (1) the depth is 94.56 + 5.30(78.53—105.13)mm from incisor teeth to the deepest bone structure, and is 103.84 + 6.18(91.38 ~ 116.11)mm from incisor teeth to spine cord surface; (2) the incision of this approach ranges anterior foramen magnum to upper C3 body, the length wise is 52. 1±3.5 (44. 3~62. 0) mm, the width of exposure after the soft tissue being tracted is 33.6+5.4 (29.5~38.7)mm.2. The safe range of transoralpharyngeal approach is limited by the vertebral artery, which lies besides body of vertebra. We measured the distance from inner marginto the midline of cervical vertebra, and proved both sides of this figure is symmetrical by analysis of SPSS 10.0. The maximum distance is 25.46+45(21.91~26.70) mm lies on transverse foramen lever of atlas, while the minimum distance is 15.91+131 (1297~18.73)mmlies on C2/3 joint lever, and the distance is 19.65+266 (13.8~27.4) mm at atlantoaxial joint level, the distance is 202+456(17.87~24.02) mm at transverse foramen lever of axis.3. The upper end of incision extend more 12.5mm in extensive discision of soft palate and hard palate approach than in simple transoralpharyngeal approach, and the incision extend 22.0mm in extensive discision of maxillary bone approach, by which we can deal with ailment range from top of clivus to upper of the third cervical body.4. All the symptoms and signs of the patients who had performed TARP system operation were satisfactorily relieved. Furthmore, all of these patients' atlantoaxial articular were anatomic reduced after operation, affirmed by image documents.Conclusions:1. Simple anatomic texture, less important structure, clear bone structure, and direct decompression are virtues of the transoralpharyngeal approach operation. TARP system is well designed, and it can perform solution and reduction in one-stage for unreduciable atlantoaxial dislocation patients, avoiding the possibility of fateful hurt to spine cord in the period of turning patients' body.2. In extensive discission of soft palate and hard palate approach operation, the exposure can extend from anterior foramen magnum to inferior one/third of clivus, large enough for clinical requirement, while there is less anatomic layers and less trauma in this approach. In extensive discision of maxillary bone (LeFort I osteotomy) approach operation, the whole clivus is encluded in field of view, and the ailment range from sphenoid sinus lever in superior clivus to superior part ofthe third cervical body, however, the maxillary arteries situate in canalis pterygopalatinus of both sides are the most important structure in this approach. 3. Shorter operation course, less bleeding, less trauma, and less loss of cervical function are merits of TARP system operation, which were proved by clinical cases. This operation is confirmed to be a original, pragmatic, and available modus operandi, and to achieve the clinical requirement of reduction in operation and maintenance of normal anatomic position after operation.