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172. Primary and Revision Suboccipital Decompression for Adult Chiari I Malformation: Analysis of Long-Term Outcomes in 393 Patients
Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S predicted FEV1 and FVC were plotted as function of time for each of the following surgical approaches: 1) ASF, 2) PSF 3) VATS þ PSF, and 4) VATSþASF. An exponential decay model was used to evaluate the initial post-operative lung function, maximal pulmonary recovery (plateau), and rate of pulmonary improvement. Statistical significance was achieved at p!0.05. Percent Predicted FEV1
Percent Predicted FVC
100
% FEV1
100
*
90
% FVC
80
70
70
60 50 40 0
*
90
80
* p<0.05 10
20
30
POST-OP (MONTHS) LENKE 123 PSF LENKE 5 ASF ALL CURVES VATS + PSF ALL CURVES VATS-I
60 50
* p<0.05 0
10
20
30
POST-OP (MONTHS) LENKE 123 PSF LENKE 5 ASF ALL CURVES VATS + PSF ALL CURVES VATS-I
Figure.
RESULTS: The number of patients in each surgical subgroup was as follows: 37 ASF (Lenke 5), 70 PSF (Lenke 1-3), 71 VATSþPSF, and 79 VATSþASF. The statistical model matched pulmonary function recovery for each surgical approach (R250.90-0.99). Surgical approach did not significantly affect the initial post-operative lung function or the rate of pulmonary recovery. There was, however, a trend towards VATS procedures having worse pulmonary outcomes initially and a slower respiratory recovery as compared to ASF or PSF (p50.08). Maximal pulmonary recovery for percent-predicted FEV1 was highest with ASF and lowest with VATSþASF (figure 1, p!0.05). Similarly, maximal pulmonary recovery for percent-predicted FVC was highest with ASF, followed by PSF, VATSþPSF, and VATSþASF (figure 2, p!0.05). CONCLUSIONS: ASF for thoracolumbar scoliosis offers maximal pulmonary function recovery at 2 years compared to other surgical approaches. There was a trend towards VATS procedures having worse outcomes at the outset with slower respiratory recovery as compared to ASF or PSF. Despite prior literature indicating small, but significant pulmonary decline for surgical procedures impacting the chest wall in AIS, the authors found no significant pulmonary decline for any procedure type. This data indicates little impact on pulmonary function for VATS procedures for thoracic scoliosis and for open approaches for thoracolumbar curve types. VATS procedures were associated with a slower rate of recovery in the first year, which resolved by 2 years follow-up. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
89S
STUDY DESIGN/SETTING: Retrospective review of single institution experience. PATIENT SAMPLE: Two hundred thirty-eight consecutive patients undergoing resection of intradural tumor at a single institution. OUTCOME MEASURES: Length of hospitalization, Surgical site infection, Incisional CSF leak, Discharge to inpatient rehab, Median MMS at last follow-up. METHODS: We retrospectively reviewed the records of 238 consecutive patients undergoing resection of intradural tumor at a single institution. The incidence of subsequent progressive kyphosis or scoliosis, peri-operative morbidity, and neurological outcome were compared between laminoplasty and laminectomy cohorts. RESULTS: One hundred eighty patients underwent laminectomy (LM) and 58 underwent laminoplasty (LP). Patients were 46 6 19 years-old with median modified McCormick Score (MMS) of 2. Tumors were intramedullary in 102 (43%) and extramedullary in 136 (57%). All baseline clinical, radiographic, and operative variables were similar between the LP and LM cohorts (Table 1). LP was associated with a decreased mean length of hospitalization (5 vs 7 days, p50.002) and trend of decreased incisional CSF leak (3% vs 9%, p50.14). Following LP vs. LM, 5 (9%) vs. 21 (12%) patient developed progressive deformity (p50.728) a mean of 14 months after surgery (Figure 1). Incidence of progressive deformity was also similar between LP vs. LM in patients !18 years of age (43% vs 36%), with preoperative scoliosis or loss of cervical/lumbar lordosis (28% vs 22%), or with intramedullary tumors (11% vs 11%). CONCLUSIONS: In our experience, laminoplasty for the resection of intradural spinal tumor was not associated with a decreased incidence of short-term progressive spinal deformity or improved neurological function. However, laminoplasty was associated with a three-fold reduction in incisional CSF leak. Longer-term follow-up is warranted to definitively assess the long-term effect of laminoplasty.
doi: 10.1016/j.spinee.2009.08.208
171. Progressive Spinal Deformity Following Laminoplasty vs. Laminectomy for Resection of Intradural Spinal Tumors: Analysis of 238 Patients Matthew McGirt, MD, Giannina Garces-Ambrossi, BASC, Scott Parker, BASC, Daniel Sciubba, MD, Ali Bydon, MD, Jean-Paul Wolinsky, MD, Ziya Gokaslan, MD, *Timothy Witham, MD; Johns Hopkins University, Baltimore, MD, USA BACKGROUND CONTEXT: Gross total resection of intradural spinal cord tumors can be achieved in the majority of cases with preservation of long-term neurological function. However, post-operative progressive spinal deformity complicates outcome in a subset of patients after surgery. PURPOSE: We set out to determine whether the use of laminoplasty (LP) versus laminectomy (LM) has reduced the incidence of subsequent spinal deformity following intradural tumor resection at our institution.
Figure. Following laminoplasty (LP) vs. laminectomy (LM), 5 (9%) vs. 21 (12%) patients developed progressive deformity (p50.728) a mean of 14 months after surgery.
FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2009.08.209
172. Primary and Revision Suboccipital Decompression for Adult Chiari I Malformation: Analysis of Long-Term Outcomes in 393 Patients Matthew McGirt, MD1, Giannina Garces-Ambrossi, BASC1, *Frank Attenello, BASC1, Scott Parker, BASC1, Arielle Stewart1,
90S
Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S 1
George Jallo, MD , Ziya Gokaslan, MD1, Jon Weingart, MD1; 1Johns Hopkins University, Baltimore, MD, USA BACKGROUND CONTEXT: Primary treatment for Chiari-I malformation is suboccipital decompression, after which the majority of patients experience symptomatic relief. However, symptom recurrence has been reported in up to one-third of patients. It is unclear which subgroups are most likely to experience treatment failure. PURPOSE: We set out to characterize incidence, time-course, and factors associated with symptom recurrence, syrinx progression, and need for revision surgery after decompression for Chiari-I malformation. STUDY DESIGN/SETTING: Retrospective review of a single institution experience. PATIENT SAMPLE: All adult patients undergoing first-time or revision suboccipital decompression for Chiari-I malformation over 14-year period. OUTCOME MEASURES: Improvement in headache and brainstem symptoms, Syrinx improvement, Recurrence of symptoms postoperatively. METHODS: We retrospectively reviewed all adult patients undergoing first-time or revision suboccipital decompression for Chiari-I malformation
over 14-year period. Incidence, time course, and factors associated with symptom recurrence were assessed via Kaplan-Meier analysis and multivariate logistic-regression analysis. RESULTS: Three hundred ninety-three adults (37.8 6 11.3 years, 59male) were followed for mean of 2 years (334 primary,59 revision decompression). Presenting symptoms included brainstem/cranial nerve symptoms in 263 (78.7%) patients, suboccipital headache in 257 (66%), sensory deficits in 138 (41%), and motor deficits in 55 (16.5%), Table 1. After first-time decompression, 155 (46.4%) patients experienced headache improvement and 174 (52%) improvement in brainstem symptoms (Figure 1). Frontal headache was the least likely symptom to improve (p50.0078, HR50.578), (Figure 2). Syrinx improvement occurred in 44 (47%) patients. Twenty-three (7%) patients required revision decompression for marked symptom recurrence. Pre-operative symptoms most likely to recur were apnea (p50.0047, HR52.11) and vertigo (p50.05, HR52.19), (Figure 3a & 3b, respectively). Patients experiencing post-operative CSF leak were more likely to experience recurrence of pre-operative symptoms (p50.019, HR53.37), (Figure 4). Use of duraplasty for closure was associated with decreased likelihood of symptomatic recurrence (p50.034, HR50.4),(Figure 5). Of the patients undergoing revision decompression, 15 (47%) experienced headache improvement and 26 (62%)experienced improvement in brainstem symptoms (Figure 6). CONCLUSIONS: In our experience, most adult patients with headache or brainstem symptoms improve after suboccipital decompression, and !10% require revision surgery. While the majority of patients improve after revision decompression, response rate is less than primary revision. Frontal headache, apnea, and vertigo were symptoms more refractory to hindbrain decompression. Lack of duraplasty and CSF leak may be associated with increased treatment failure.
Figure 1. After first-time decompression, 155 (46.4%) patients experienced headache improvement and 174 (52%) patients experienced improvement in brainstem symptoms.
Figure 2. Frontal headache was the least likely symptom to improve (p50.0078, HR50.578).
Figure 3. Pre-operative symptoms most likely to recur were apnea (p50.0047, HR52.11) and vertigo (p50.05,HR52.19).
Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S
91S
Friday, November 13, 2009 4:10–5:10 PM Focused Paper Presentations 2: Trauma 173. Unilateral Posterior Atlantoaxial Transarticular Screw Fixation in Patients with Atlantoaxial Instability: Comparison with Bilateral Method Hyoung-Joon Chun, MD1, Cheol-Su Jwa2, Hyun Jong Hong3, Koang Hum Bak, MD, PhD4; 1Department of Neurosurgery, Hanyang University Medical Center, Seoul, South Korea; 2Department of Neurosurgery, National Medical Center, Selou, South Korea; 3Department of Neurosurgery, Hanyang University Medical Center, Gyeonggi-do, South Korea; 4Seoul, South Korea
Figure 4. Patients experiencing post-operative CSF leak were more likely to experience recurrence of pre-operative symptoms (p50.019, HR53.37).
Figure 5. Use of duraplasty for closure was associated with decreased likelihood of symptomatic recurrence (p50.034, HR50.4).
Figure 6. Of the patients undergoing revision decompression, 15 (47%) experienced headache improvement and 26 (62%) experienced improvement in brainstem symptoms.
FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2009.08.210
BACKGROUND CONTEXT: Simultaneous bilateral posterior transarticular screw fixation (TAF) and bone grafting with wire loop provides immediate, rigid internal fixation for atlantoaxial instability (AAI). It is the most effective biomechanical technique to attain C1-2 stability, and is superior to conventional wiring methods by virtue of more rigid fixation. Solid atlantoaxial fusion has been reported in 80 to 100% of patients who were treated with this method. However, bilateral TAF across the C1-2 may be contraindicated or impossible in up to 20% of patients because of its structural disfigurements such as anomalous course of the vertebral artery (VA), comminuted fractures of C-1 or C-2, or other pathological processes. PURPOSE: The purpose of this study is, therefore, to assess the durability and safety of unilateral TAF with posterior wiring by means of comparison with bilateral TAF. STUDY DESIGN/SETTING: When encountering with these situations, unilateral TAF could be alternative method of C1-2 arthrodesis for managing AAI. PATIENT SAMPLE: Between January 2003 and December 2007, 54 consecutive patients underwent TAF (were surgically managed) for the AAI. The pathologic conditions responsible for the AAI included rheumatoid arthritis in 41 patients, os odontoideum in 6, non-union of a Type II odontoid fracture in 5, hemangioblastoma in one and atlantoaxial subluxation in one, respectively. These fifty-four patients were divided into two groups, according to the surgical methods, i.e. bilateral TAF vs. unilateral TAF. OUTCOME MEASURES: Plain cervical radiographs were serially surveiled at immediate, 1, 3 and 6 months postoperatively to define bone fusion from ADI. The judgment of bone fusion was evaluated at 6 months postoperatively regaredless of overall follow-up period. METHODS: Preoperative studies including cervical x-ray, three dimensional computed tomogram, CT angiogram, and magnetic resonance image were checked. The atlanto-dental interval (ADI) was measured in preoperative period, immediate postoperatively, and postoperative 1, 3 and 6 months. RESULTS: The mean ADI in unilateral group was measured as 2.63 mm in immediate postoperatively, 2.61 mm in 1 month, 2.64 mm in 3 months and 2.61 mm in 6 months postoperatively. The mean ADI of bilateral group was also measured as following; 2.76 mm in immediate postoperative, 2.71 mm in 1 month, 2.73 mm in 3 months, 2.73 mm in 6 months postoperatively. Comparison of ADI measurement showed no significant difference in both groups, and moreover fusion rate was 100% in bilateral and 96.3% in unilateral group (p50.317). CONCLUSIONS: Even though bilateral TAF is best option for AAI in biomechanical perspectives, unilateral screw fixation also can be a useful alternative in otherwise dangerous or infeasible cases through bilateral screw placement. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2009.08.212
Percent Predicted FVC
100
% FEV1
100
*
90
% FVC
80
70
70
60 50 40 0
*
90
80
* p<0.05 10
20
30
POST-OP (MONTHS) LENKE 123 PSF LENKE 5 ASF ALL CURVES VATS + PSF ALL CURVES VATS-I
60 50
* p<0.05 0
10
20
30
POST-OP (MONTHS) LENKE 123 PSF LENKE 5 ASF ALL CURVES VATS + PSF ALL CURVES VATS-I
Figure.
RESULTS: The number of patients in each surgical subgroup was as follows: 37 ASF (Lenke 5), 70 PSF (Lenke 1-3), 71 VATSþPSF, and 79 VATSþASF. The statistical model matched pulmonary function recovery for each surgical approach (R250.90-0.99). Surgical approach did not significantly affect the initial post-operative lung function or the rate of pulmonary recovery. There was, however, a trend towards VATS procedures having worse pulmonary outcomes initially and a slower respiratory recovery as compared to ASF or PSF (p50.08). Maximal pulmonary recovery for percent-predicted FEV1 was highest with ASF and lowest with VATSþASF (figure 1, p!0.05). Similarly, maximal pulmonary recovery for percent-predicted FVC was highest with ASF, followed by PSF, VATSþPSF, and VATSþASF (figure 2, p!0.05). CONCLUSIONS: ASF for thoracolumbar scoliosis offers maximal pulmonary function recovery at 2 years compared to other surgical approaches. There was a trend towards VATS procedures having worse outcomes at the outset with slower respiratory recovery as compared to ASF or PSF. Despite prior literature indicating small, but significant pulmonary decline for surgical procedures impacting the chest wall in AIS, the authors found no significant pulmonary decline for any procedure type. This data indicates little impact on pulmonary function for VATS procedures for thoracic scoliosis and for open approaches for thoracolumbar curve types. VATS procedures were associated with a slower rate of recovery in the first year, which resolved by 2 years follow-up. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
89S
STUDY DESIGN/SETTING: Retrospective review of single institution experience. PATIENT SAMPLE: Two hundred thirty-eight consecutive patients undergoing resection of intradural tumor at a single institution. OUTCOME MEASURES: Length of hospitalization, Surgical site infection, Incisional CSF leak, Discharge to inpatient rehab, Median MMS at last follow-up. METHODS: We retrospectively reviewed the records of 238 consecutive patients undergoing resection of intradural tumor at a single institution. The incidence of subsequent progressive kyphosis or scoliosis, peri-operative morbidity, and neurological outcome were compared between laminoplasty and laminectomy cohorts. RESULTS: One hundred eighty patients underwent laminectomy (LM) and 58 underwent laminoplasty (LP). Patients were 46 6 19 years-old with median modified McCormick Score (MMS) of 2. Tumors were intramedullary in 102 (43%) and extramedullary in 136 (57%). All baseline clinical, radiographic, and operative variables were similar between the LP and LM cohorts (Table 1). LP was associated with a decreased mean length of hospitalization (5 vs 7 days, p50.002) and trend of decreased incisional CSF leak (3% vs 9%, p50.14). Following LP vs. LM, 5 (9%) vs. 21 (12%) patient developed progressive deformity (p50.728) a mean of 14 months after surgery (Figure 1). Incidence of progressive deformity was also similar between LP vs. LM in patients !18 years of age (43% vs 36%), with preoperative scoliosis or loss of cervical/lumbar lordosis (28% vs 22%), or with intramedullary tumors (11% vs 11%). CONCLUSIONS: In our experience, laminoplasty for the resection of intradural spinal tumor was not associated with a decreased incidence of short-term progressive spinal deformity or improved neurological function. However, laminoplasty was associated with a three-fold reduction in incisional CSF leak. Longer-term follow-up is warranted to definitively assess the long-term effect of laminoplasty.
doi: 10.1016/j.spinee.2009.08.208
171. Progressive Spinal Deformity Following Laminoplasty vs. Laminectomy for Resection of Intradural Spinal Tumors: Analysis of 238 Patients Matthew McGirt, MD, Giannina Garces-Ambrossi, BASC, Scott Parker, BASC, Daniel Sciubba, MD, Ali Bydon, MD, Jean-Paul Wolinsky, MD, Ziya Gokaslan, MD, *Timothy Witham, MD; Johns Hopkins University, Baltimore, MD, USA BACKGROUND CONTEXT: Gross total resection of intradural spinal cord tumors can be achieved in the majority of cases with preservation of long-term neurological function. However, post-operative progressive spinal deformity complicates outcome in a subset of patients after surgery. PURPOSE: We set out to determine whether the use of laminoplasty (LP) versus laminectomy (LM) has reduced the incidence of subsequent spinal deformity following intradural tumor resection at our institution.
Figure. Following laminoplasty (LP) vs. laminectomy (LM), 5 (9%) vs. 21 (12%) patients developed progressive deformity (p50.728) a mean of 14 months after surgery.
FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2009.08.209
172. Primary and Revision Suboccipital Decompression for Adult Chiari I Malformation: Analysis of Long-Term Outcomes in 393 Patients Matthew McGirt, MD1, Giannina Garces-Ambrossi, BASC1, *Frank Attenello, BASC1, Scott Parker, BASC1, Arielle Stewart1,
90S
Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S 1
George Jallo, MD , Ziya Gokaslan, MD1, Jon Weingart, MD1; 1Johns Hopkins University, Baltimore, MD, USA BACKGROUND CONTEXT: Primary treatment for Chiari-I malformation is suboccipital decompression, after which the majority of patients experience symptomatic relief. However, symptom recurrence has been reported in up to one-third of patients. It is unclear which subgroups are most likely to experience treatment failure. PURPOSE: We set out to characterize incidence, time-course, and factors associated with symptom recurrence, syrinx progression, and need for revision surgery after decompression for Chiari-I malformation. STUDY DESIGN/SETTING: Retrospective review of a single institution experience. PATIENT SAMPLE: All adult patients undergoing first-time or revision suboccipital decompression for Chiari-I malformation over 14-year period. OUTCOME MEASURES: Improvement in headache and brainstem symptoms, Syrinx improvement, Recurrence of symptoms postoperatively. METHODS: We retrospectively reviewed all adult patients undergoing first-time or revision suboccipital decompression for Chiari-I malformation
over 14-year period. Incidence, time course, and factors associated with symptom recurrence were assessed via Kaplan-Meier analysis and multivariate logistic-regression analysis. RESULTS: Three hundred ninety-three adults (37.8 6 11.3 years, 59male) were followed for mean of 2 years (334 primary,59 revision decompression). Presenting symptoms included brainstem/cranial nerve symptoms in 263 (78.7%) patients, suboccipital headache in 257 (66%), sensory deficits in 138 (41%), and motor deficits in 55 (16.5%), Table 1. After first-time decompression, 155 (46.4%) patients experienced headache improvement and 174 (52%) improvement in brainstem symptoms (Figure 1). Frontal headache was the least likely symptom to improve (p50.0078, HR50.578), (Figure 2). Syrinx improvement occurred in 44 (47%) patients. Twenty-three (7%) patients required revision decompression for marked symptom recurrence. Pre-operative symptoms most likely to recur were apnea (p50.0047, HR52.11) and vertigo (p50.05, HR52.19), (Figure 3a & 3b, respectively). Patients experiencing post-operative CSF leak were more likely to experience recurrence of pre-operative symptoms (p50.019, HR53.37), (Figure 4). Use of duraplasty for closure was associated with decreased likelihood of symptomatic recurrence (p50.034, HR50.4),(Figure 5). Of the patients undergoing revision decompression, 15 (47%) experienced headache improvement and 26 (62%)experienced improvement in brainstem symptoms (Figure 6). CONCLUSIONS: In our experience, most adult patients with headache or brainstem symptoms improve after suboccipital decompression, and !10% require revision surgery. While the majority of patients improve after revision decompression, response rate is less than primary revision. Frontal headache, apnea, and vertigo were symptoms more refractory to hindbrain decompression. Lack of duraplasty and CSF leak may be associated with increased treatment failure.
Figure 1. After first-time decompression, 155 (46.4%) patients experienced headache improvement and 174 (52%) patients experienced improvement in brainstem symptoms.
Figure 2. Frontal headache was the least likely symptom to improve (p50.0078, HR50.578).
Figure 3. Pre-operative symptoms most likely to recur were apnea (p50.0047, HR52.11) and vertigo (p50.05,HR52.19).
Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S
91S
Friday, November 13, 2009 4:10–5:10 PM Focused Paper Presentations 2: Trauma 173. Unilateral Posterior Atlantoaxial Transarticular Screw Fixation in Patients with Atlantoaxial Instability: Comparison with Bilateral Method Hyoung-Joon Chun, MD1, Cheol-Su Jwa2, Hyun Jong Hong3, Koang Hum Bak, MD, PhD4; 1Department of Neurosurgery, Hanyang University Medical Center, Seoul, South Korea; 2Department of Neurosurgery, National Medical Center, Selou, South Korea; 3Department of Neurosurgery, Hanyang University Medical Center, Gyeonggi-do, South Korea; 4Seoul, South Korea
Figure 4. Patients experiencing post-operative CSF leak were more likely to experience recurrence of pre-operative symptoms (p50.019, HR53.37).
Figure 5. Use of duraplasty for closure was associated with decreased likelihood of symptomatic recurrence (p50.034, HR50.4).
Figure 6. Of the patients undergoing revision decompression, 15 (47%) experienced headache improvement and 26 (62%) experienced improvement in brainstem symptoms.
FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2009.08.210
BACKGROUND CONTEXT: Simultaneous bilateral posterior transarticular screw fixation (TAF) and bone grafting with wire loop provides immediate, rigid internal fixation for atlantoaxial instability (AAI). It is the most effective biomechanical technique to attain C1-2 stability, and is superior to conventional wiring methods by virtue of more rigid fixation. Solid atlantoaxial fusion has been reported in 80 to 100% of patients who were treated with this method. However, bilateral TAF across the C1-2 may be contraindicated or impossible in up to 20% of patients because of its structural disfigurements such as anomalous course of the vertebral artery (VA), comminuted fractures of C-1 or C-2, or other pathological processes. PURPOSE: The purpose of this study is, therefore, to assess the durability and safety of unilateral TAF with posterior wiring by means of comparison with bilateral TAF. STUDY DESIGN/SETTING: When encountering with these situations, unilateral TAF could be alternative method of C1-2 arthrodesis for managing AAI. PATIENT SAMPLE: Between January 2003 and December 2007, 54 consecutive patients underwent TAF (were surgically managed) for the AAI. The pathologic conditions responsible for the AAI included rheumatoid arthritis in 41 patients, os odontoideum in 6, non-union of a Type II odontoid fracture in 5, hemangioblastoma in one and atlantoaxial subluxation in one, respectively. These fifty-four patients were divided into two groups, according to the surgical methods, i.e. bilateral TAF vs. unilateral TAF. OUTCOME MEASURES: Plain cervical radiographs were serially surveiled at immediate, 1, 3 and 6 months postoperatively to define bone fusion from ADI. The judgment of bone fusion was evaluated at 6 months postoperatively regaredless of overall follow-up period. METHODS: Preoperative studies including cervical x-ray, three dimensional computed tomogram, CT angiogram, and magnetic resonance image were checked. The atlanto-dental interval (ADI) was measured in preoperative period, immediate postoperatively, and postoperative 1, 3 and 6 months. RESULTS: The mean ADI in unilateral group was measured as 2.63 mm in immediate postoperatively, 2.61 mm in 1 month, 2.64 mm in 3 months and 2.61 mm in 6 months postoperatively. The mean ADI of bilateral group was also measured as following; 2.76 mm in immediate postoperative, 2.71 mm in 1 month, 2.73 mm in 3 months, 2.73 mm in 6 months postoperatively. Comparison of ADI measurement showed no significant difference in both groups, and moreover fusion rate was 100% in bilateral and 96.3% in unilateral group (p50.317). CONCLUSIONS: Even though bilateral TAF is best option for AAI in biomechanical perspectives, unilateral screw fixation also can be a useful alternative in otherwise dangerous or infeasible cases through bilateral screw placement. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2009.08.212