Application of vacuum sealing drainage in open ankle fracture and dislocation / 中国骨伤

<p><b>OBJECTIVE</b>To investigate therapeutic effects of vacuum sealing drainage (VSD) in the treatment of soft tissue defect combined with tendon and bone exposure.</p><p><b>METHODS</b>From October 2007 to February 2011, 397 patients (412 feet) with open ankle fracture and dislocation combined with soft tissue defected were treated by VSD. There were 301 males and 96 females with an average age of 36 years (ranging age from 20 to 73 years). According to AO classification, 74 feet were type I, 211 feet were type II, 108 feet were type III and 19 feet were type IV. The mean time from injury to operation was 5.6 h ( 2 to 12 h). The mean treatment time of was 10 months (4 to 19 months).</p><p><b>RESULTS</b>One hundred and forty-one patients were primarily healed, 97 patients were sutured at stage II. Split-thick skin grafting was performed at stage II was performed in 103 patients; free flap transplantation was performed in 25 patients. Three of the 34 patients with infection were removed steel plate; Eviscerate flap coverage wound was performed in 14 patients caused by the first metatarsal bone exposure; Toe amputation were performed in 22 cases caused by toes necrosis. Tarsometatarasl joints perforators' surgery was performed in 10 patients with forefeet necrosis. Thirty hundred and six patients were followed up from 3 to 20 months (averaged 10 months). The wounds healed well.</p><p><b>CONCLUSION</b>VSD for soft tissue defects caused by ankle injury is a simple and effective method, but can not replace debridement and transfer flap.</p>

Evaluation of the surgical treatment of Lisfranc injuries / 中国骨伤

<p><b>OBJECTIVE</b>To study the clinical results of surgical treatment for Lisfranc fracture-dislocation.</p><p><b>METHODS</b>From January 2003 to September 2009, 57 patients with Lisfranc injuries were treated by surgical operation included 41 males and 16 females with an average age of 33.8 years old ranging from 20 to 64 years. According to Myerson's classification, there were 31 cases of middle column injuries, 15 cases of medial-middle column injuries and 11 cases of three-column injuries. Among them, 25 patients accepted the emergency operation (<24 hours) and 32 patients were treated in average 7 days (3 to 11 days) after injury.</p><p><b>RESULTS</b>All the wounds were healed primarily with a mean operative time of 50 min (30 to 70 min). All patients were followed up for 4 to 70 months (averaged 35 months). The total AOFAS scores (American Orthopaedic Foot and Ankle Society) was in averaged of(84.73 +/- 14.26). All the patients returned to normal daily life after a mean time of 5.1 months (3 to 12 months). The average AOFAS scores of 52 anatomical reduction cases was (87.63 +/- 13.71), 5 non-anatomical reduction cases was (74.31 +/- 21.96), 26 multiple column trauma cases was (76.58 +/- 11.51). Complications of osteoarthritis occurred in 8 cases, confirming it was the main complication of these injuries.</p><p><b>CONCLUSION</b>Lisfranc injuries can be surgically treated well. Reduction of the middle column is the key to reestablishment the stability of the tarsometatarsal joint complex. The quality of the reduction correlated with treatment outcome.</p>

Proximal femoral nail for the treatment of unstable intertrochanteric femoral fractures / 中国骨伤

<p><b>OBJECTIVE</b>To investigate the clinical results of the proximal femoral nail antirotation (PFNA) system in the treatment of unstable intertrochanteric femoral fractures.</p><p><b>METHODS</b>From September 2006 to September 2009, 90 patients (40 males and 50 females, ranged in age from 64 to 95 years with an average of 73.2 years with unstable intertrochanteric femoral fractures were surgically treated with PFNA. Fifty patients had the fractures in the right hip, and 40 patients had the fractures in the left hip. The fractures were classified according to the AO classification: 11 patients were type A2.1, 21 patients were type A2.2,25 patients were type A2.3 9 patients were type A3.1,6 patients were A3.2 and 18 patients were A3.3. The patients underwent surgery within a mean of 3.2 days(ranged,2 to 20.1 days) from injury. The mean hospital stay was 12.8 days(ranged,7 to 24 days). Closed reduction was achieved in all the patients. Harris hip score were used for the evaluation of clinical effects.</p><p><b>RESULTS</b>The mean operation time was 36.8 min (ranged, 23 to 110 min) and the mean blood loss was 150 mi (ranged, 100 to 500 ml). The mean follow-up period was 12 months (ranged, 6 to 24 months). All the patients had fracture union. Sixty-nine patients got excellent reduction, 14 good and 7 bad. The mean collodiaphysial angle was 135.60 (ranged, 1260 to 1470). Postoperative complications included secondary varus in 2 patients,calcification at the tip of the greater trochanter in 5 patients, medial thigh pain in 7 patients,and screw cut-out in 1 petient. Ten patients had femoral shortness (mean 9.3 mm,ranging from 8 to 14 mm). The mean Harris hip score was (80.5 +/- 9.8). According to Harris hip scores evaluation system, 26 patients reached an excellent result, 37 good, 18 poor and 9 bad.</p><p><b>CONCLUSION</b>Due to advantages of high union rate, short operation time, and early postoperative mobilization, PFNA osteosynthesis is an idea method for surgical treatment of unstable intertrochanteric femoral fractures.</p>

Feasibility study on posterior laminar screw fixation techniques in the axis / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To get morphologic parameters of Chinese adults through observation and measurement on axial laminas, to evaluate the feasibility of placing axial laminar screws and to introduce the technique.</p><p><b>METHODS</b>Relative parameters of 28 sets of fresh Chinese adults'axial specimens, including distance from the superior and inferior entry points of axial laminar screws to the superior margins of axial laminas, superior, middle, inferior thickness and height of the axial laminas, length and angle of the axial laminar screw trajectories, distance from the entry points of axial laminar screws to the transverse foramen and central points of the inferior articular process, were measured with a digital caliper and a goniometer. Data were statistically analyzed.</p><p><b>RESULTS</b>Averagely, distance from the superior and inferior entry points of axial laminar screws to the superior margins of axial laminas was 5 mm and 9 mm, superior, middle, inferior thickness and the height of the axial laminas were 3.2 mm, 6.7 mm, 5.5 mm and 12.8 mm respectively, and the length of the superior and inferior axial laminar screw trajectories was 26.2 mm and 25.5 mm, respectively.</p><p><b>CONCLUSIONS</b>It is feasible and reliable to apply posterior laminar screw fixation techniques to the axes of Chinese adults. Also the C2 laminar screw fixation technique can be taken as a supplementary to conventional posterior screw fixations of C2.</p>

Operative treatment of old acetabular fractures / 中国骨伤

<p><b>OBJECTIVE</b>To explore the operative methods and effects of treatment of old acetabular fractures.</p><p><b>METHODS</b>From October 2001 to October 2007, 26 patients with old acetabular fractures were treated with operation including 21 males and 5 females with an average age of 34 years ranging from 18 to 65 years. On the basis of the three-dimensional computed tomography, all cases were diagnosed and classified according to Letourne-Judet classification, 9 cases were posterior wall fracture, 3 cases were lateropulsition fracture, 7 cases were lateropulsition and posterior wall fracture, 2 cases were posterior column and posterior wall fracture, 2 were T-shape fracture, 3 were dual column fracture. These patients were treated through the anterior,posterior, combined anterior-posterior approaches. The time from injured to operation was 33 to 141 days (averaged 36.4 days). All the fractures were fixed with screws and AO reconstruction plates.</p><p><b>RESULTS</b>All patients were followed up for 6 to 96 months, with an average time of 32.4 months. Evaluated according to Matta criteria, the results of scores was (5.04 +/- 1.04) on pain, (5.23 +/- 0.76) on range of motion, (4.92 +/- 1.16) on walking,and tatal (5.06 +/- 0.99) on average; The functional results of hip joints were excellent in 6 cases, good in 10 cases, fair in 6 cases, and poor in 4 cases. Sciatic nerve injury was found in 2 patients,lateral femoral cutaneus nerve injury in 3 patients, necrosis of femoral head in 1 patient,infection in 1 patient, and ectopic bone formation in 6 patients.</p><p><b>CONCLUSION</b>Good clinical results can be obtained by careful selection of operative indications of old acetabular fractures in combination with proper operative approach and correct reduction and fixation.</p>

Application of the pedicle screws for cervicothoracic fracture-dislocation / 中国骨伤

<p><b>OBJECTIVE</b>To explore pedicle screw implantation for fracture-dislocation injuries at cervicothoracic junction (C6-T2).</p><p><b>METHODS</b>Pedicle screw implantation was used for twenty-six patients with cervicothoracic fracture-dislocation from May 2001 to Jan 2008. There were 17 males and 9 females with an average of 48.5 years (range,20 to 75 years). Single posterior pedicle screw fixation was performed for 17 cases, and posterior screw fixation combined with anterior reduction and plate fixation for the other nine. The accuracy of the pedicle screws were evaluated by CT views after surgery. Complications and neurological recovery were also recorded after the procedures.</p><p><b>RESULTS</b>All subjects were followed up from 3 to 74 months with average 36.5 months. Four cases of complete paraplegia died of cardiovascular or pulmonary failure within half a year after surgery. There were 104 pedicle screws implanted totallythe including 74 pedicle screws in cervical vertebrae, 16 at C5, 16 at C6, 42 at C7, and 30 pedicle screws in upper thoracic vertebrae,in which 22 at T1, 8 at T2. No injury of spinal cord, nerve roots and vertebral artery was found during operation. Eleven screws (14.9%) were perforated out of the pedicles in cervical spine, in which 7(9.5%) through lateral cortex, 1 (1.4%) through the superior and 3 (4.1%) through the inferior. Three screws (10%) were perforated in upper thoracic spine, in which 2 (6.7%) by lateral cortex and 1(3.3%) by the medial (within 2 mm). Bony fusion was achieved for all cases and all internal fixator was good except 1 screw broken at C5. JOA score increased from preoperative (7.5 +/- 2.0) to postoperative (14.5 +/- 2.3) evaluated in 6 months after operation,with statistic difference (t = 6.34, P < 0.05). Neurological improvement was gotten in all patients according to ASIA classification but three cases who suffered from complete neurological injuries.</p><p><b>CONCLUSION</b>Implantation of pedicle screws at cervicothoracic junction can be safe and reliable if the urgeonis familiar with the local anatomy of cervicothoracic spine, and the technique for implantation of the screws. Related radiological parameters should be measured for each subject before the operation in attempt to get a therapy individually.</p>

Analysis of safety and effect of reconstructing anterior and middle columns by single posterior approach in treating lumbar burst fractures / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To explore the safety and effect of the technique of reconstructing anterior and middle columns by posterior approach in treating lumbar burst fractures.</p><p><b>METHODS</b>From July 2005 to January 2007, 22 cases (18 males and 4 females, aged 28-57 years, 42.7 years on average) of lumbar burst fractures were treated with surgical procedures in our hospital. Based on the routine posterior approach, one of the transverse processes of the injured vertebra was incised to get access to the lateral side of the injured vetebral body. After all the displaced fracture fragments were cleared away and the spinal canal was decompressed, the titanium mesh packed with autografts was implanted from the lateral side to reconstruct the anterior and middle columns. The adjacent above and below segments of the vetebral body were fixed with transpedicular screws. The operation time, intraoperative blood loss, vertebral height, degree of kyphotic deformity and comprised spinal canal were documented.</p><p><b>RESULTS</b>The average operation time was 3.5 hours (ranging 2.8-5.8 hours) and the average blood loss was 820 ml (ranging 650-2 100 ml). All the cases were followed up for 17.2 months on average ( ranging 12-28 months). The height of the injured vetebral body was restored from 24 % (12%- 45%) preoperatively to 96% (95%-99%) postoperatively (P less than 0.05). The natural spinal curvatures and spinal canal were restored. Three cases were involved in transient iatrogenic nerve root injury and 1 case was involved in the loosening of the connected rod of the pedicle screw system 3 months postoperatively.</p><p><b>CONCLUSIONS</b>The technique of implanting the titanium mesh by posterior approach is effective and safe enough to reconstruct the anterior and middle columns in treating lumbar burst fractures.</p>

Comparison study of biomechanical test among fixation techniques of three types screw of posterior approach for C2 / 中国骨伤

<p><b>OBJECTIVE</b>To evaluate the screw pull-out strength of posterior C2 when the screw is fixed to C2 through the trans-pedicle or lateral mass or trans-laminar unicortically or bicortically,so as to provide biomechanical basis for the clinical application of posterior C2 screw fixation technique.</p><p><b>METHODS</b>The pedicle screw,the lateral mass screw or the laminar screw was separately anchored into 30 fresh C2 specimens unicortically or bicortically. The screw pull-out strength of different fixation was tested and compared with the others.</p><p><b>RESULTS</b>The average pull-out strength of C2 bicortical pedicle screw was (1255.8 +/- 381.9) N, the strongest during all the methods. The mean pull-out strength of C2 unicortical pedicle screw, C2 bicortical lateral mass screw and C2 bicortical laminar screw were (901.8 +/- 373.3) N, (776.1 +/- 306.8) N and (640.8 +/- 302.9) N respectively,with no statistical difference.</p><p><b>CONCLUSION</b>Pedicle screw should be the first choice for the posterior fixation on axis. C2 lateral mass screw fixation and C2 laminar screw fixation can be another supplement choice and the screw had better be placed bicortically.</p>

Analysis of safety and effect of the technique of reconstructing anterior and middle columns by single posterior approach / 中国骨伤

<p><b>OBJECTIVE</b>To explore the safety and effect of the technique of reconstructing anterior and middle column by posterior approach in treatment of lumbar burst fractures.</p><p><b>METHODS</b>From July 2005 to January 2007, 22 patients of lumbar burst fractures (18 males and 4 females, the age was from 28- to 57-years-old with an average of 42.7 years) were treated as the following surgical procedures: based on the routinal posterior approach, one of the transverse process of the injured vertebral was incised to get access to the lateral side of the injured vertebral body. After cleaning of all the displaced fracture fragments and decompressing the spinal canal, the titanium mesh packed with autografts were implanted from lateral side to reconstruct the anterior and middle column. The above and below adjacent vertebral body were fixed by transpedicular screws. The operative time, intraoperative blood loss, vertebral height, degree of kyphotic deformity and comprised spinal canal were recorded.</p><p><b>RESULTS</b>The average operative time was 3.5 h (2.8-5.8 h) and the average blood loss was 820 ml (650-2100 ml). All the patients were followed up with an average 17.2 months (from 12 to 28 months). The height of the injured vertebral body were restored from (23.70 +/- 9.31)% preoperative to (95.77 +/- 1.93 )% postoperative (P<0.05). The natural spinal curvatures and spinal canal were restored. Three cases were involved in transient iatrogenic nerve root injury. And 1 case was involved in the loosening of the connected rod of the pedicle screw system at 3 months after operation.</p><p><b>CONCLUSION</b>The technique of implanting the titanium mesh by posterior approach was effective and safe enough to reconstruct the anterior and middle column in treating lumbar burst fracture. With this technique, good results could be achieved.</p>

The feasibilty study of posterior laminar screw fixation techniques in axis / 中国骨伤

<p><b>OBJECTIVE</b>Observation and measurement were done on axial laminar to get the parameters of morphology in Chinese. To evaluate the possibility of the placement of axial laminar screw.</p><p><b>METHODS</b>The relative parameters of 28 sets of fresh Chinese adults' axial specimens were measured with a digital caliper, a goniometer and imageology, including the distance from superior and inferior the anchor point of the axial laminar screw to superior margin of the axial laminar, the superior,middle and inferior thickness of axial laminar, the height of axial laminar, the length and the angle of the axial laminar screw trajectory, the distance from the anchor point of the axial laminar screw to hole of vertebral artery and the central point of inferior articular process and so on. The data were statistically analyzed.</p><p><b>RESULTS</b>The distance from superior and inferior the anchoi point of the axial laminar screw to superior margin of the axial laminar was 4 mm and 8 mm respectively. The superior, middle and inferior thickness of axial laminar was 3.2, 6.7, 5.5 mm respectively. The height of axial laminar was 12.8 mm. The superior and inferior length of axial laminar screw trajectory was 26.2 mm and 25.5 mm respectively.</p><p><b>CONCLUSION</b>It is feasible and reliable for posterior laminar screw fixation techniques of axis in Chinese. C2 laminar screw fixation techniques could be used as a supplementary method for conventional posterior screw fixation techniques of C2.</p>

All pedicle screws technique applied to the treatment of idiopathic scoliosis / 中国骨伤

<p><b>OBJECTIVE</b>To Analyze the therapeutic efficacy of all pedicle screws technique applied to the treatment of idiopathic scoliosis and evaluate its safety.</p><p><b>METHODS</b>From June 2002 to October 2005, 56 patients with idiopathic scoliosis were treated with all pedicle screws technique, including 11 males and 45 females, ranging in age from 8 to 22 years. According to Lenke classification, 29 patients were Type 1, 6 patients were Type 2, 8 patients were Type 3, 2 patients were Type 4, 8 patients were Type 5, and 3 patients were Type 6. Cobb angles ranged from 45 degrees to 85 degrees (mean 62.45 degrees).</p><p><b>RESULTS</b>The mean operation time was 3 hours and 20 minutes, and the average amount of bleeding was 600 ml. There were 425 pedicle screws inserted including 244 in thoracic, and 181 in lumbar, the positions of which were evaluated by CT. Nine screws were inserted with perforating through the medial wall of the pedicles. All the patients were followed up for 5 to 40 months (mean 22.5 months). The mean Cobb angle was corrected from 62 degrees preoperatively to 18 degrees postoperatively,and the average correction rate was 72.5%. No spinal nerves injury was found after operation, and superficial infection occurred in 2 patients but recovered after dressing change. All the patients got satisfactory spinal fusion and remained partly spinal mobility with fewer complications.</p><p><b>CONCLUSION</b>The application of all pedicles screws technique with familar with pedicular anatomy of scoliosis by imaging examination could gain a satisfactory effect of correction with less complications.</p>

Anterior decompression and reconstruction for the treatment of burst thoracolumbar fractures with anterior and median column injury / 中国骨伤

<p><b>OBJECTIVE</b>To explore the treatment of anterior decompression and reconstruction for burst thoracolumbar fractures with anterior and median column injury and to evaluate the therapeutic effect.</p><p><b>METHODS</b>Thirty-four patients suffering from burst thoracolumbar fractures with anterior and median column injury (male 22 and female 12, aged from 20 to 63,with an average of 40.5 years) were treated by anterior decompression and reconstruction from May 2001 to October 2006. Operative duration, bleeding and the neurological function of patients were recorded.</p><p><b>RESULTS</b>All the patients were followed up from 3 to 60 months and the average time was 24.5 months. Operative duration was (178 +/- 65) min. The volume of bleeding was (1 750 +/- 950) ml and the volume of autotransfusion was (950 +/- 750) ml. Cobb angle were corrected from 27.0 degrees +/- 6.5 degrees to 3.0 degrees +/- 1.5 degrees. All fractures obtained fusion. No failure of internal fixation and formation of false joint happened.</p><p><b>CONCLUSION</b>The technique of anterior decompression and reconstruction for burst thoracolumbar fractures with anterior and median column injury is effective, with which the decompression and reconstruction of the spinal stability can be performed under direct vision at one stage, and the sagittal alignment can be corrected at the same time. The procedure will be more smoothly by the application of the intraoperative autotransfusion.</p>

Pedicle lag screw for the treatment of indicated Hangman fractures / 中国骨伤

<p><b>OBJECTIVE</b>To define the indication of C2 pedicle lag screw to treat Hangman fractures and evaluate its results.</p><p><b>METHODS</b>Twenty-eight patients with Hangman fractures were enrolled from July 2003 to June 2007. Six, 17 and 5 patients classified as type I , II and IIa injuries respectively according to Levine-Edwards classification and graded as D spinal injury in 3 cases and E in 7 cases according to Frankel scale. The entry points of screws were located at middle point of lateral mass. The direction of screw is determined based on the direction of the medial and superior border of C2 pedicle, usually 25 degrees to 30 degrees cephalad to the transverse plane and 30 degrees to 35 degrees medial to the sagittal plane. The length of screws range from 24 to 30 mm.</p><p><b>RESULTS</b>There were no vertebra artery injuries or other complications during the operation. A mean follow-up time was 20 months (4 to 48 months). All cases gained bony union at the 6th postoperative month with complete neurological function recovery. The range of neck rotation was restored normal without cervicle spinal instability and lag screws loosing found.</p><p><b>CONCLUSION</b>Single segmental pedicle lag screw internal fixation provides instantly stability to Hangman fracture and scarcely affects the physiological functions of upper cervicle spine. With appropriate indications of the techniques should be reducible Hangman fracture.</p>

Anatomic comparison of transarticular screws with lateral mass screws in cervical vertebrae / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To compare the potential incidence of nerve root (ventral and dorsal ramus) injury caused by cervical transarticular screws and Roy-Camille lateral mass screws.</p><p><b>METHODS</b>Insertion techniques with Klekamp transarticular screws and Roy-Camille lateral mass screws were respectively performed in this study. Each technique involved four specimens and 40 screws, which were inserted from C(3) to C(7). And 20-mm-long screws were used to overpenetrate the ventral cortex. The anterolateral aspect of the cervical spine was carefully dissected to allow observation of the screw-ramus relationship.</p><p><b>RESULTS</b>The overall percentage of nerve invasion was significantly lower with Klekamp (45%) technique than with Roy-Camille (85%) technique (P less than 0.05). The largest percentage of nerve invasion for Klekamp transarticular screws was found at the dorsal ramus (25%), followed by the ventral ramus (15%) and the bifurcation of the ventral dorsal ramus (5%). The largest percentage of nerve invasion for Roy-Camille lateral mass screws was found at the ventral ramus (80%).</p><p><b>CONCLUSION</b>The potential risk of nerve root invasion is lower with Klekamp transarticular screws than with Roy-Camille lateral mass screws.</p>

The assessment of accuracy and safety of thoracic pedicle screw placement in the fracture of thoracic spine / 中华外科杂志

<p><b>OBJECTIVE</b>To investigate the accuracy and safety of pedicle screw placement in the fracture of thoracic spine.</p><p><b>METHODS</b>On the basis of imaging for the fracture of thoracic spine of 50 cases, the screw prick point, angle, depth and diameter were measured and defined on the thoracic vertebrae pedicle by CT thin-slice scan in standard prone in all cases. The accuracy and safety of screws placement was evaluated with X-ray and CT thin-slice scan in all cases postoperative.</p><p><b>RESULTS</b>Among of 240 thoracic pedicle screws that were inserted in 50 cases, 220 screws (91.7%) were fully contained within the cortical boundaries of the pedicle, 20 screws (8.3%) were misplaced, 7 screws (2.9%) laterally, 5 screws (2.1%) anterolateral and 2 (0.8%) of it demonstrated aortic abutment, 3 screws (1.3%) caudad perforations of the pedicle, 3 screws (1.3%) expended the wall of the pedicle to inside, 2 screws (0.8%) were misplaced in vertebral canal according to X ray and CT thin-slice scan. When comparing screws in different part of thoracic, there was a significant difference.</p><p><b>CONCLUSIONS</b>Preoperative CT measurement of the thoracic pedicle in the treatment of thoracic fracture can provide important data. It is important factors for thoracic pedicle screws that can be placed safety with guided by intraoperative fluoroscopic imaging and anatomic landmarks. CT thin-slice scan can evaluate accuracy misplace of thoracic pedicle screws, and show anatomic place surroundings of thoracic pedicle screws postoperative. More misplaced screws are seen proximally.</p>

Four-point internal fixation technique for traumatic atlantoaxial instability / 中华创伤杂志

Objective To explore the clinical effect and application value of four-point internal fixation technique (internal fixation of C_1-C_2 transarticular screws combined with Apofix laminar clamp technique) for traumatic atlantoaxial instability.Methods A total of 16 patients with traumatic atlanto- axial instability,who had reducible atlantoaxial dislocation with reduction after traction and irreducible at- lantoaxial dislocation with traction reduction after anterior laxation,were treated with four-point internal fixation technique using autologous bone grafts.Results All patients' symptoms were improved to some extent,and no severe complications,such as injury of nerve blood vessels were found.All patients were followed up for 8-26 months (average 16 months).Bony fusion was obtained in all cases.The spinal cord function improvement was marked in 5 cases (31%),good in 8(50%),mild in 2(13%),but un- changed in 1 (6%).No deterioration occurred in all cases.There was no loosening or breakage of screws and clamps.Conclusion Fixation of C_1-C_2 transarticular screws combined with Apofix laminar clamp technique can atlain four-point internal fixation,and can provide three-dimensional stability of atlantoaxial complex and excellent biomechanics environment for bony fusion if the structure of the posterior arch of C_1-C_2 is intact.