Microscopic Transoral Odontoidectomy Combined With Posterior Occipital-cervical Fusion In In The Treatment Of Basilar Invagination Syndrome

Objective:To report the surgical method and clinical curative effect ofmicroscopic transoral odontoidectomy combined with occipital-cervicalfusion in the treatment of basilar invagination syndrome.Method:From September2007to September2012,15patients withirreducible basilar invagination operated by microscopic transoralodontoidectomy combined with occipital-cervical fusion were collectedin the Division2of orthopedics of Fujian Provincial Hospital.There were9men and6women,ranging from32to57years old,with the average of45.9.10patients with basilar invagination suffered from occipital-atlasfusion and atlanto-axial dislocation,and5patients with basilarinvagination suffered from Klipple-Feil syndrome.All patients showeddifferent degrees of pyramidal tract syndrome.Pre-operation imagingshowed the odontoids inbursted foramen magnum,and the tips ofodontoids extended above the chamberlain line more than15mm,resulting in obviously compression of the spinal cord from theventral aspect.The cervicomedullary angle of all patients were95°~ 126°,with the average of112.6±9.2°.The symptoms of all patients didnot improve after the treatment of skull traction, and2cases becameworse.All patients were operated by combining transoral odontoidectomywith occipital-cervical fusion with intraoperative neuro-physiologicalmonitoring.Among them,4cases were operated by the traditionaltransoral approach;11cases were operated by microscopic transoralapproach.To measure parameters of these patients on CL, ML, WL, Klausheight index, extension cord angle and clivus canal angle before and afteroperation according to each patient imaging data and compared it withpaired T test statistics. The Japanese Orthopedic Association(JOA) wasused for evaluating spinal cord funcion of each patient.Surgicalcomplications and graft-bone fusion were also recorded.Result:All patients were achieved satisfied followed-up.The followed-uptime of all patients ranged from12months to20months,with the averageof16months. The imaging parameters of these patients on CL, ML, WL,Klaus height index, cervicomedullary angle and clivus canal angle beforeoperation were15～20mm、10～16mm、13～19mm、10～23mm、95～126°、105～128°respectively. And after operation it were-5～-2mm、-7～-3mm、-5～2mm、30.5～42.5mm、152～175°、131～146°respectively.Compared to preoperative imaging parameters, postoperativeimaging parameters were improved obviously.There were obviousstatistical significance in imaging parameters of these patients before and after operation(p<0.01). The mean JOA scores of preoperation and lastfollowed-up after operation were6.5±1.6、14.1±1.2respectively. Theimprovement ratio was71.5%. then the curative effects were showed:exellent in5cases, good in9cases, common in1case and no poor cases.And the rate of excellent and good of the clinical result was93.3%.Therewere no obvious decline phenomenon on amplitudes of SEP and MEPunder intraoperative neuro-physiological monitoring. All patients showedno complications,such as vertebral-artery injury,leakage of cerebrospinalfluid,infection,failure of graft-bone fusion, spinal cord and nerve rootinjury,etc.4cases operated by the traditional transoral procedureperformed with temporomandibular joint pain,while11cases operated bymicroscopic transoral approach did not appear the complicationsabove.The graft-bone of all postoperative patients were ranging from5months to13months,with the average of8.5months.Conclusion:Transoral odontoidectomy combined with posterioroccipital-cervical fusion was an effective method for treatment on seriousbasilar invagination with the indications of ventraldecompression,resulting in the remarkable redress of theoccipital-cervical malformation and the obvious improvement of spinalcord function since thorough decompression. With the help of themicroscope and intraoperative Neuro-physiological monitoring,the surgical procedure were safe and had few complications.