| The transoral approach is the simplest and commonly used approach for ventral, medial extradural lesions of the craniovertebral junction, which was first described in1917by Kanaval to take out the bullet compressing the ventral cervical spine. Compared with other approaches, the3major advantages of transoral approach were described as below, direct lesions, lack of important blood vessels and nervus, avoid bilateral traction of the important structures. Numerous modifications have been used to extend the transoral exposure to the upper cervical spine. Mandibuloglossotomy was described by Kocher in1911for tumors of the posterior pharynx and the base of the tongue. Trotter extended the exposure by splitting the tongue sagittally in the median raphae, creating the "median(anterior) translingual pharyngotomy approach", which was re-introduced by Martin et al. in1961as the "median labiomandibular glossotomy." Delgado et al. described the resection of the chordomas in the clivus and upper cervical spine by mandibuloglossotomy in1981. Wood et al. introduced the technique combined with mandibulotomy, glossotomy and palatomy in1980. In the year of2008, Youssef et al. summarized the exposure ranges and the operative distances of the standard transoral approach and its modifications after reviewing the literatures. During the procedure of transoral approach to deal with the lesion of upper cervical spine, the vertebral artery was the most vulnerable blood vessel, if the vertebral artery was injured during the surgery, the central nervous system would be damaged, even death sometimes. As a result, define the distance between the bilateral vertebral arteries as the safe zone of the surgery was reasonable and nessecery. However, the lining of vertebral arteries was mentioned neither in Youssef’s nor in the past literatures. In our study, anatomical research was performed in6fresh cadaver specimens to cervical spine, in order to supply anatomic foundations for the transoral approach with mandibulutomy and mandibuloglossotomy.Objectives1. Simulated the procedure of mandibulotomy in6fresh cadaver specimens to upper cervical spine, to observe the anatomical structures on the way layer by layer, to measure the anatomical data, to supply anatomical foundations for not only finishing mandibulotomy safely, effectly and rapidly, but also for decreasing the complications.2. Splitted the tongue from the midline on the basis of mandibulotomy (mandibuloglossotomy) in the cadaver specimens, to observe the anatomical structures on the way layer by layer, to measure the anatomical data, to supply anatomical foundations for not only finishing mandibuloglossotomy safely, effectly and rapidly, but also for decreasing the complications as well.Materials and Methods1. Materials6fresh cadaver specimens, including4males and2females, were used in this study(supplied by anatomical department of Southern Medical University, stored in the freezer at the temperature of minus twenty degrees centigrade and auto defrosted at room temperature before the research). From the whole head to at least the first thoracic vertebra were included in all specimens, though the arteries of all heads had not been poured into red emulsion, the vertebral arteries were engorged perfectly through anatomy. The death reason, birthplace and age of the cadavers were unknown, we examined the cadavers before dissection to exclude the congenital deformities, cancer and fractures.2. Equipments Surgical instruments, Codman retractor, vernier caliper(the accuracy of measurements is0.02mm), the compass, the protractor,2kirschner wires.3. Methods (1) After auto defrosting, the cadaveric heads were fixed on the table to make sure the heads were slightly retroverted, we drafted the oral cavity by Codman retractor and exposed posterior pharyngeal wall after mouthwashing.(2) Touched tuberculum anterius atlantis after the posterior pharyngeal wall was exposed, considered it as the marking point, incised the posterior pharyngeal wall longitudinally, then incised the mucosa, constrictor naris and fascia praevertebralis layer by layer.(3) Striped the soft tissue from the tuberculum anterius atlantis, vertebral body of axis to the atlantoaxial lateral mass bilaterally.(4) Splitted the lip and mandibular from the midline and then tracted bilaterally, the integrity of the tongue was kept. Using the spatula to press the body of the tongue caudally, went on stripping and exposing caudally and laterally to the processus transversus of the cervical spine. Exposed the vertebral artery carefully in the space between the processus transversuses of2vertebral bodies. The range of exposure was measured and the rostral and caudal limits of expoxure were recorded, the distances between the vertebral artery of each side to the midline and the vertical depth between the vertebral artery of each side to the fore-teeth of the two approaches were measured. Besides, the exploratory operational range and reconstractive operational range were described. The exploratory operational range(EOR) stood for largest exploratory range of this particular approach, meanwhile, the reconstructive operational range(ROR) stood for the longest segments of cervical spine screw-plate system to regain stability under this particular approach.(5) From the midline, splitted the body of the tongue to the cartilage epiglottica and lingual bone caudally, then tracted bilaterally. Using the spatula to press the muscle of floor of mouth caudally, went on stripping and exposing caudally and laterally to the processus transversus of the cervical spine. Exposed the vertebral artery carefully in the space between the processus transversuses of2vertebral bodies. The range of exposure was measured and the rostral and caudal limits of expoxure were recorded, the distances between the vertebral artery of each side to the midline and the vertical depth between the vertebral artery of each side to the fore-teeth of the two approaches were measured. Besides, the exploratory operational range and reconstractive operational range were described and recorded again.4. Data and statistical analysis Every parameter measured for3times and calculated the mean. Paired t-test was performed with SPSS13.0software package, if there wasn’t statistical significant difference between the left side and the right side(p>0.05), the statistics of the two sides would be combined.Results1. Measurement of the soft tissue of the posterior pharyngeal wall To measure the thickness of the soft tissue from the mucosa membrane of the posterior pharyngeal wall to the bony marking point of each vertebral body. The thickness to the tuberculum anterius atlantis was (6.03±1.57)mm,(5.16±0.95)mm to the anterior surface of the body of axis,(4.72±0.94)mm to the anterior surface of the body of the third cervical spine,(5.00±0.97)mm to the anterior surface of the body of the fourth cervical spine,(5.63±0.48)mm to the anterior surface of the body of the fifth cervical spine, the results of atlas and axis corresponded with that of Ai Fuzhi et al. and Wang Zhiyun et al., the soft tissue from the mucosa membrane of the posterior pharyngeal wall to the vertebral body consisted of mucosa, constrictor naris, fascia buccopharyngeal, fascia praevertebralis and ligamenta longitudinale anterius. Retropharyngeal space was the space between fascia buccopharyngeal and fascia praevertebralis, which was consisted with loose connective tissue, the tiny branches of arteriae palatine ascendens and arteriae pharyngea ascendens, which crawled across the musculi constrictor pharyngis superior, and venae pharyngeae lined inside it. Retrocardiac space was the space between fascia praevertebralis and musculi longus capitis, musculi longus colli. At the level of anterior surface of the third cervical spine, the musculi constrictor pharyngis was consisted of musculi constrictor pharyngis medius and musculi constrictor pharyngis inferior, beneath the level of the fourth cervical spine, the musculi constrictor pharymgis was musculi constrictor pharyngis inferior. Splitted the fascia praevertebralis to expose retrocardiac space, the musculi longus capitis and musculi longus colli existed here, the musculi longus capitis laid anteriorly to the musculi longus colli, there were unequal numbers of tiny blood vessels crawled on the posterior surface of the musculi longus colli, the distribution feature of these blood vessels was "sparse medially and dense bilaterally." 2. EOR and ROR In our study, the range of exposure consisted of the record of rostral limit, caudal limit of expoxure and the measurement of the angle of exposure sagitally. The exposure angle of mandibulotomy was63.67°±3.50°, meanwhile, the exposure angle of mandibuloglossotomy was74.14°±1.47°, which was10.47°larger than mandibulotomy caudally. According to paired-t test, there was significant difference between the exposure angles of mandibulotomy and mandibuloglossotomy(p<0.05). In spite of mandibulotomy or mandibuloglossotomy, there were tiny differences among the rostral and caudal limits of each specimen, except for the rostral limit of specimen2was the end of clivus, the rostral limit of all the other specimens was the lower1/3of clivus. Similar to the rostral limit, except for the caudal limit of specimen4was the superior endplate of the fourth cervical spine, the caudal limit of all the other specimens ranged from the inferior endplate of the fourth cervical spine to the superior endplate of the fifth cervical spine. Specimen4was a young male with small oral fissure, the subtotal ectomy could be done in the lower half of axis and the third cervical spine, the screws could be twisted into the higher half of axis and the superior edge of the fourth cervical spine in order to regain stability. In specimen1, specimen3and specimen6, the subtotal ectomy could be done in the lower half of axis, the third cervical spine and the higher half of the fourth cervical spine, the screws could be twisted into the higher half of axis and the lower half of the fourth cervical spine in order to regain stability. In specimen2and specimen5, the subtotal ectomy could be done in the lower half of axis, the third cervical spine and the fourth cervical spine, the screws could be twisted into the higher half of axis and the superior edge of the fifth cervical spine in order to regain stability. With the approach of mandibuloglossotomy, except for the caudal limit of specimen4was the middle1/3of the fifth cervical spine, the caudal limits of all the other specimens extended one vertebral body lower than those of mandibulotomy, ranged from the inferior endplate of the fourth cervical spine to the superior endplate of the fourth cervical spine. To sum up, the range of exposure of mandibulotomy was the lower1/3of clivus to C4/5intervertebral space, meanwhile, the range of exposure of mandibuloglossotomy was the lower1/3of clivus to C5/6intervertebral space. In one hand, the least EOR of mandibulotomy was the lower1/3of clivus to the superior endplate of the fourth cervical spine, the least ROR of mandibulotomy was the lower half of axis to the superior endplate of the fourth cervical spine, the largest EOR of mandibulotomy was the lower1/3of clivus to the superior endplate of the fifth cervical spine, the largest ROR of mandibulotomy was the lower half of axis to the superior endplate of the fifth cervical spine. On the other hand, the least EOR of mandibuloglossotomy was the lower1/3of clivus to the superior endplate of the fifth cervical spine, the least ROR of mandibulotomy was the lower half of axis to the superior endplate of the fifth cervical spine, the largest EOR of mandibulotomy was the lower1/3of clivus to the superior endplate of the sixth cervical spine, the largest ROR of mandibulotomy was the lower half of axis to the superior endplate of the sixth cervical spine.3. Anatomic parameters of vertebral artery The scholars had accepted that the vertebral artery was consisted of five segments, which were known as segment V1to V5, among them, segment V1to V4lined extracranially and segment V5lined extracranially endocranially. Normally, the vertebral artery runs in the foramina transversariums of every cervical spine expect for the seventh one on both sides, in our study, vertebral arteries could be seen above the level of the foramina transversarium of the fifth cervical spine in all6cadaver specimens. Wang Zhiyun et al. and Shui Tao et al. had done exhaustive research on segment V3to V5, and had gained detailed anatomic data. The description of the lining character and measurement of anatomic data of segment V3of mandibulotomy and mandibuloglossotomy was the research point of our study. Paired t-test was performed by SPSS13.0software package, there was no significant difference between the left side and the right side(p>0.05), so the statistics of the two sides were combined. The distance between the vertebral artery to the midline at the level of C2/3intervertebral space was(16.88±0.75)mm, the distance between the vertebral artery to the midline at the level of C3/4intervertebral space was (16.48±1.47)mm, the distance between the vertebral artery to the midline at the level of C4/5intervertebral space was (16.30±1.09)mm. Meanwhile, the vertical depth between the vertebral artery to the fore-teeth at the level of C2/3intervertebral space was (96.44±3.59)mm, the vertical depth between the vertebral artery to the fore-teeth at the level of C3/4intervertebral space was (97.94±4.51)mm, the vertical depth between the vertebral artery to the fore-teeth at the level of C4/5intervertebral space was (99.83±4.77)mm sequencely.Conclusions1. The transoral approach with mandibulotomy and mandibuloglossotomy are safe and effect approach to deal with the patients with limiting of mouth opening caused by congenital small oral fissure, derangement of temporomandibular joint and rheumatoid arthritis, thus, the long segmental ventral decompression of cervical spinal cord at the level of craniocervical junction, medial and inferior cervical spine at the same time.2. In one hand, in the approach of mandibulotomy, the caudal limit was C4/5intervertebral space according to press the body of tongue with spatula, the explore of the lower1/3of clivus to C4/5intervertebral space and the operation of the ventral side of bulbus medullae to the fifth cervical spinal cord. To lift the handle grip of the spatula in order to press the body of the tongue harder, we could reach the middle, even lower1/3of the fifth vertebral body at the level of anterior surface of vertebral body and middle1/3of C6cervical spinal cord at the level of spinal cord, which was similar as the explore of the lower1/3of clivus to C5/6intervertebral space and the operation of the ventral side of bulbus medullae to the sixth cervical spinal cord. On the other hand, though the splitted tongue was sewed up during surgery, the patients’ function of dyslalia, manducation and deglutition could be affected after the operation. To sum up, in allusion to the long segmental ventral decompression of cervical spinal cord above the level of the middle of C6spinal cord, the glossotomy was not necessary, meanwhile, in allusion to the long segmental ventral decompression of cervical spinal cord beneath the level of the middle of C6spinal cord, even lifting the handle grip of the spatula could not work out, glossotomy would be a good try. |
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