- Email: [email protected]
Treatment of odontoid fractures with single anterior screw fixation
Journal of Clinical Neuroscience 14 (2007) 824–830 www.elsevier.com/locate/jocn
Clinical study
Treatment of odontoid fractures with single anterior screw fixation Kyung-Jin Song a, Kwang-Bok Lee a
b,*
, Ki-Nam Kim
a
Department of Orthopedic Surgery, College of Medicine, Institute for Medical Science, Chonbuk National University Hospital, Jeonju, Korea b Department of Orthopedic Surgery, College of Medicine, Institute for Medical Science, Cheju National University Hospital, 154, Samdo2-dong, Jeju-shi, Cheju, 690-716, Korea Received 4 April 2006; accepted 7 June 2006
Abstract We evaluate the efficacy and safety of single anterior screw fixation in the treatment of types II and III (Anderson and D’Alonzo classification) odontoid process fractures, and analyse our surgical results. From May 1996 to October 2003, 16 patients underwent single anterior screw fixation for type II (n = 12) and III (n = 4) odontoid process fractures and had at least 1 year follow-up. We analyzed sex, age, associated injuries, and complications. The radiographic findings, including union rate, union time, changes of fracture shape and metal migration, were evaluated and modified Robinson criteria were used for clinical assessment. Of 16 patients, 15 (94%) achieved bony union at an average of 13.8 weeks. One patient required a secondary posterior procedure after anterior screw fixation. A full range of cervical motion was maintained in 12 patients, a limitation of <25% in three, and of >25% in one. There were no major complications related to the operative technique, including neurologic deterioration or wound infection. We conclude that single anterior screw fixation is clinically and radiologically effective and safe for type II and III odontoid process fractures. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Odontoid fracture; Anterior screw fixation; Fusion rate; Complications
1. Introduction Odontoid fractures comprise 10–15% of cervical spine fractures, and are becoming more common, mostly due to traffic accidents, with injuries of the head and neck. The neurological symptoms vary, from disturbance of sensory or motor function of the upper extremities, to quadriplegia, and require accurate diagnosis and treatment. It is reported that the nonunion rate for odontoid fractures is 4–64%1 depending on the fracture site and the method of treatment. Non-surgical treatment with cervical collar or halo-vest may provide stable support in type II fractures. Posterior fixation of C1–2 achieves a higher fusion rate compared to conservative treatment, but is a challenging surgical technique and results in limitation of
cervical range of motion after surgery. However, direct anterior screw fixation preserves rotatory motion of the cervical spine, with immediate stabilization of the spine using a simple surgical technique.2 The authors investigated the preoperative and postoperative clinical findings and radiographs, of patients with type II and type III odontoid fractures (based on the Anderson and D’Alonzo classification3) treated with anterior screw fixation to evaluate fracture alignment, union rates, radiologic and clinical outcomes, range of motion of the cervical spine, and complications. We discuss the safety and efficacy of this surgical technique. 2. Materials and methods 2.1. Patients
*
Corresponding author. Tel.: +82 64 750 1119; fax: +82 64 726 0173. E-mail address: [email protected] (K.-B. Lee).
0967-5868/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2006.06.016
This study included 16 patients, with type II and type III odontoid process fractures using the Anderson and
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
D’Alonzo classification who were treated with single anterior screw fixation, from May 1996 to October 2003. Type II fractures, and type III fractures where the fracture line starts from the base of the odontoid process to the body of C2, met the inclusion criteria. Exclusion criteria included two patients with pure type III fractures, two with type II or III fractures where the fracture line extended to the antero-inferior aspect of the C2 body, and one patient lost to follow-up. In total, 16 of 21 patient were included in the study. There were 13 male and three female patients. The age at operation ranged from 15–70 years, 36.3 years average. The cause of fracture included three falls, eight motor vehicle accidents and five pedestrian accidents. The fractures were associated with three thoracolumbar fractures, one spinous process fracture and one clavicle fracture (Table 1). Twelve patients had type II fractures, and four type III. The patterns of fractures were 10 transverse and two spiral (posterior oblique) type II fractures and two transverse and two vertical type III fractures (Table 2). Follow-up data were available for 16 patients. In all cases, the patients underwent reduction using skull traction and anterior single screw fixation, performed via cannulated screw. Variables in surgical technique were removed by all procedures being performed by a single surgeon.
Table 2 Pattern of fractures of the 16 patients according to the Anderson and D’Alonzo classification1
Transverse Spiral (posterior oblique) Total
Type II
Type III
10 2 12
2 2 4
surgery, as well as at the last follow-up. There were three criteria for radiologic fusion; the fracture line should not be visible, no angular deformity should develop, and no motion should be detected at the fracture site on the flexion-extension radiographs. The degree of displacement and angulation were measured to assess the degree of correction and fixation achieved. The range of motion of the cervical spine was measured at the last follow-up. Sex, average age, associated injuries and complications were recorded. In addition, a mal-union (angular deformity) group was included in the union group but reviewed seperately.
Table 3 Modified Robinson’s criteria4 used to assess clinical outcome Excellent
No pain and able to return to normal activities of daily living
Good
Only slight discomfort Occasional use of non-narcotic pain medication Slight reduction in activity
Fair
Mild or moderate pain necessitating immobilization in a soft collar Use of non-narcotic pain medication Limitation of activity
Poor
No relief of pain despite use of narcotic medication Severe limitation of activity
2.2. Method The follow-up period ranged from 12–88 months. The average follow-up was 41.5 months. The patients were reviewed at 4 weeks, 8 weeks, 12 weeks and then every 3 months for 12 months post-surgery. After 1 year, the outcomes were verified by radiological and physical examination every 6 months. On radiological evaluation, the fusion rate and time were examined. Anteroposterior, lateral and open-mouth radiographs were obtained before and after
825
Table 1 Summary of patients Case no.
Age
Sex
Cause
Type
Frankel grade
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
22 21 18 60 54 51 24 24 27 40 36 15 23 55 41 70
F M M M M M M M M M M M M F F M
MVA Pedes Pedes MVA MVA MVA Fall Pedes Pedes MVA Pedes Fall MVA MVA Fall MVA
II II II III III II III II II III II II II II II II
E E E E D!E E E E E E E E E E E E
MVA = motor vehicle accident, Pedes = pedestrian accident.
Complication
Non-union
Mal-union Mal-union
ROM
X-ray result
Clinical result
Associated injury
Full Full Full Full Full Full Full Full 60°rotation Full Full Full Full 60° rotation Full 40° rotation
Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion
Excellent Excellent Excellent Good Good Good Good Excellent Good Good Good Excellent Excellent Good Good Fair
Y N Y Y Y N N N N N N N N Y N
826
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
For clinical outcome evaluation, a modification of Robinson’s criteria,4 based on the status of fusion, the degree of pain relief, the neurological status, and the activities of daily living, was used (Table 3). 2.3. Surgical technique Under general anesthesia with nasal intubation, patients were placed in a supine position. Reduction was
achieved with skull traction under controlled anteroposterior and lateral fluoroscopes. The cervical spine was extended as much as possible within the confines of the fracture. The anterior approach of Southwick and Robinson4 was used in all cases and all patients were approached from the left side in order to prevent recurrent laryngeal nerve injury. Before the operation, the thyroid and cricoid cartilage was marked in order to identify the C5–C6 disc space and then a skin incision was made
Fig. 1. (A,B) Pre-operative open mouth and lateral x-rays showing type III (combined type II or III) odontoid process fracture. (C,D) Post-operative open mouth and lateral x-rays showing internal fixation with a single cannulated screw across the dens fracture. (E,F) Open mouth and lateral roentgenograms at 12 weeks after surgery showing bony unioin of the fracture site.
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
between them. Dissecting soft tissue carefully, the carotid artery was laterally retracted, and the trachea and esophagus was medially retracted, from the midline of the anterior border of the sternocleidomatoid muscle. After the anterior cervical spine was exposed, the anterior longitudinal ligament was divided axially and the anterior inferior margin of the C2 body was exposed. Biplanar intraoperative fluoroscopy was used, and with lateral fluoroscopic guidance, the guide wire was inserted from the anterior-inferior margin of the C2 body to the posterior odontoid process. The guide wire was inserted centrally so that reduction of the fracture was maintained. A
827
4.0 mm cannulated screw was inserted after only tapping the entry portal. The cannulated screw was cautiously inserted until it reached the posterior cortex of the odontoid process, avoiding proximal migration of the guide pin to prevent cord injury. 3. Results 3.1. Radiologic evaluation Bony fusion was radiologically evident in 15 of 16 patients (Fig. 1), achieved within an average 13.8 weeks
Fig. 2. (A,B) Preoperative lateral and open mouth x-ray of a 27-year-old man showing a type II odontoid process fracture. (C,D) Post-operative anterior and lateral views showing internal fixation with a single cannulated screw across the fracture. (E,F) 12 weeks later, there was non-union of the odontoid process.
828
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
(minimum 8 weeks, maximum 6 months). Two of the 15 fused patients had mal-union. One had no significant limitation of range of motion in the cervical spine, but the other showed distal migration of the screw and an anterior angular deformity, with more than 25% limited range of motion. No further surgical intervention was used for this patient who then underwent rehabilitation therapy. A patient with non-union (Fig. 2) was reoperated 3 months after surgery, by a posterior fixation (Gallie fusion) technique (Fig. 3), and ended up with satisfactory fusion. 3.2. Clinical outcome Thirteen patients had a normal range of motion in the cervical spine, two (1 mal-union, 1 non-union) had about 25% limited range of motion and one (mal-union) had more than 25% limited range of motion in the cervical spine. Six patients achieved clinically excellent outcomes, nine good and one fair outcome: thus, 94% with good or better clinical outcome in total (Table 1). 3.3. Complications There was one distal migration of the screw, two malunions, and one non-union. One patient had neurological deterioration with numbness of the forearm, but recovered after surgery. 4. Discussion Both conservative and surgical treatments can be used for odontoid process fractures, but conservative treatment results in an approximatley 25% non-union rate,5 as it is difficult to obtain stable support solely with a Halo-vest or cervical collar.6 In many patients, posterior atlanto-axial fusion with wiring and cortico-cancellous bone graft is performed as it is a simple surgical technique with high fusion
rates.7,8 This gives a satisfactory outcome, but there remains motion at the fracture site, even after fusion of C1–2, and it is reported that the non-union rate is up to 54%, due to the inflow of synovial fluid around the intact transverse ligament and alar ligament.9,10 Also, atlanto-axial posterior fusion causes about 50% of rotation limitation and about 30% of bending motion limitation, and, especially if there is an atlas ring fracture (approximately 16% of all C2 fractures), the fusion should be extended to the occiput.6 To overcome these limitations, Bo¨hler11 and Naknishi12 performed anterior fixation with two lag screws. This technique preserves the motion segment at C1–2 with a simple fixation technique and less damage to the soft tissues compared to posterior fixation; however, this technique is not useful for oblique fractures, since the compression force is not applied to the fractured segment, and is also technically demanding. The patient with a short neck or upper thoracic lordosis cannot be treated, and a fluoroscope is required throughout the operation. If the patient has cervical stenosis, there is a possibility of spinal cord injury due to hyperextension. Nielsen et al.13 reported an approximate 71% fusion rate with anterior screw fixation for odontoid process fractures, and Henry et al.14 reported a 92% fusion rate for anterior screw fixation with 81 patients, which shows the efficacy of anterior fixation; only two patients were reoperated with posterior fusion. Esses and Bednar15 introduced anterior single screw fixation; it has been said that when the distal segment of the fracture is small, it is technically demanding to obtain proper fixation, but they achieved satisfactory clinical outcomes and reported better biomechanical fixation with a single screw fixation compared to double screw fixation. In this study, the authors obtained 94% fusion rate at an average of 13.8 weeks, with anterior single screw fixation, which is similar to the outcomes with double screw fixation. As for rotatory and bending motion limitation after the operation, 13 patients
Fig. 3. (A,B) The revised 3-month post-operative lateral and open mouth x-rays showing the Gallie type posterior C1–2 arthrodesis.
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
(81%) showed normal range of motion and two (12.5%) showed less than 25% limitation. This is a better clinical outcome than that achieved using the posterior fixation technique reported by McGraw et al.6 Prudent selection of patients is important for success.16 The grade of atlantal transverse ligament damage must be considered in treating acute odontoid process fractures; if this ligament is damaged, atlanto-axial stability is not achieved using single screw fixation and fusion alone.17 The atlantal transverse ligament integrity can be assessed with radiologic or open-mouth images, or with CT scan, and more clearly with MRI, although specificity is relatively low. There have been reports of atlantal transverse ligament damage with odontoid process fractures, but this is infrequent.16 In this study, there was no delayed atlanto-axial instability due to ruptured atlantal transverse ligament. To confirm this, radiological and open mouth x-rays as well as CT scans, were performed on all patients. In addition to atlantal transverse ligament integrity, the type of odontoid process fracture is another factor influencing the success rate of surgery.18 The indication for anterior fixation of the odontoid process in types II and III fractures, is a fracture line facing downward posteriorly and obliquely. It is a contraindication if the fracture line is facing downward and anteriorly or if the oblique fracture line is in the sagittal plane.19,20 This is because mal-alignment of the screw may occur due to torsional forces during screw insertion, and also because it is not easy to obtain sufficient space for proper screw fixation in the posterior part of the odontoid process.21 In patients with transverse fracture, the threads of the screw take most of the load during extension and bending, and thus the stability of the fixation can be maintained, unless the screw is bent or fractured. After biomechanical research of anterior screw fixation, Sasso et al.22 reported that double screw fixation is no stronger than single screw fixation, and gives only about 50% stability of the intact odontoid process. This shows that it is more important to accurately identify the fracture line than relying on the number of screws used for fixation. In this study, the authors achieved 94% fusion rate with single screw fixation, which was thought to be due to the lag effect obtained during the cannulated screw insertion, by penetrating the far cortex of the odontoid process. Except for the one non-union, the high fusion rate in the other 15 patients was due to accurate reduction of the fracture line. It is still controversial whether age should be regarded as an exclusion criteria for this procedure, but Subach et al.20 reported that it is not appropriate to perform this technique on patients over 60 years, as it is difficult to maintain extension during surgery due to degeneration of the spine. However, Berlemann et al.23 and Guiot et al.24 reported that conservative treatment of fractures with more than 6 mm migration in patients over 65 years had a high non-union rate, while anterior fixation gave
829
satisfactory results (90% fusion rate), and it would be more efficient to perform this technique on elderly patients than other conservative measures. In this study, there were two patients over 60 years; one took 12 weeks for fusion with good clinical outcome, and the other had mal-union with distal migration of the screw, as well as anterior angulation. Data is limited to analyse the relationship between age and clinical outcome, and it is necessary to be cautious about applying these for clinical decisions. Studies with larger patient groups are required to identify the relationship between age, other factors, and clinical results. 5. Conclusion Anterior screw fixation, with a high fusion rate (94%) and a low complication rate, represents a highly effective surgical treatment for odontoid process fractures. However, careful preoperative planning is necessary to avoid technical pitfalls and achieve good clinical outcomes. References 1. Schweigel JF. Management of the fractured odontoid with halo thoracic bracing. Spine 1987;12:838–9. 2. Graziano G, Jaggers C, Branch CL. A comparative study of fixation techniques for type II fractures of the odontoid process. Spine 1993;18:2383–7. 3. Anderson LD, D’Alonzo RT. Fractures of the odontoid process of the axis. J Bone Joint Surg 1974;56-A:1663–74. 4. Robinson RA, Smith GW. Anterolateral cervical disc removal and interbody fusion for cervical disc syndrome. Bull Johns Hopkins Hosp 1955;96:223–4. 5. Fujji E, Kobayashi K, Hirabayashi K. Treatment in fractures of the odontoid process. Spine 1988;13:604–9. 6. McGraw RW, Rusch RM. Atlanto-axial arthrodesis. J Bone and Joint Surg 1973;55-B:482–8. 7. Brooks AL, Jenkin EB. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg 1978;60-A:279–84. 8. Griswold DM, Albright JA. Atlanto-axial fusion for instability. J Bone and Joint Surg 1978;60-A:285–92. 9. Schatzker J, Rorabeck CH. Fractures of the dens. an analysis of thirty-seven cases. J Bone Joint Surg 1971;53-B:392–404. 10. Sowthwick WO. Management of fractures of the dens, odontoid process. J Bone Joint Surg 1980;62-A:482–6. 11. Bohler J. Anterior stabilization for acute fractures and nonunion of the dens. J Bone Joint Surg 1982;64-A:18–27. 12. Nakanishi T, Sasaki T. Internal fixation for the odontoid fractures. Orthop Trans 1977;59:940–3. 13. Nielsen OJ, Edal AL. Anterior screw fixation of fractures of the dens axis. Ugeskr Laeger 2001;163:2140–3. 14. Henry AD, Bohly J. Fixation of odontoid fractures by an anterior screw. J Bone Joint Surg 1999;81-B:472–7. 15. Esses SI, Bednar D. Screw fixation of odontoid fractures and nonunion. Spine 1991;16:483–5. 16. Lee S-C, Chen J-F. Management of acute odontoid fractures with single anterior screw fixation. J Clin Neurosci 2004;11:890–5. 17. Greene KA, Dickman CA. Transverse atlantal ligament disruption associated with odontoid fractures. Spine 1994;19:2307–14. 18. Sasso R, Doherty BJ, Crawford MJ. Biomechanics of odontoid fracture fixation. Comparison of the one and two-screw technique. Spine 1993;18:1950–3.
830
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
19. Max A, Christian E, Michael C. Fractures of the odontoid process. Treatment with anterior screw fixation. Spine 1989;14: 1065–70. 20. Subach BR, Morone MA, Haid RW. Management of acute odontoid fractures with single-screw anterior fixation. Neurosurgery 1999;45: 812–9. 21. Dickman CA, Marciano FF. Principles of Spinal Surgery, Vol. 1. New York: McGraw-Hill; 1996., pp.123–39.
22. Sasso R, Doherty BJ. Biomechanics of odontoid fracture fixation. Spine 1993;18:1950–3. 23. Berlemann U, Schwarzenbach O. Dens fractures in the elderly. Results of anterior screw fixation in 19 elderly patients. Acta Orthop Scand 1997;68:319–24. 24. Guiot B, Fessler RG. Complex atlantoaxial fractures. J Neurosurg 1999;91:139–43.
Clinical study
Treatment of odontoid fractures with single anterior screw fixation Kyung-Jin Song a, Kwang-Bok Lee a
b,*
, Ki-Nam Kim
a
Department of Orthopedic Surgery, College of Medicine, Institute for Medical Science, Chonbuk National University Hospital, Jeonju, Korea b Department of Orthopedic Surgery, College of Medicine, Institute for Medical Science, Cheju National University Hospital, 154, Samdo2-dong, Jeju-shi, Cheju, 690-716, Korea Received 4 April 2006; accepted 7 June 2006
Abstract We evaluate the efficacy and safety of single anterior screw fixation in the treatment of types II and III (Anderson and D’Alonzo classification) odontoid process fractures, and analyse our surgical results. From May 1996 to October 2003, 16 patients underwent single anterior screw fixation for type II (n = 12) and III (n = 4) odontoid process fractures and had at least 1 year follow-up. We analyzed sex, age, associated injuries, and complications. The radiographic findings, including union rate, union time, changes of fracture shape and metal migration, were evaluated and modified Robinson criteria were used for clinical assessment. Of 16 patients, 15 (94%) achieved bony union at an average of 13.8 weeks. One patient required a secondary posterior procedure after anterior screw fixation. A full range of cervical motion was maintained in 12 patients, a limitation of <25% in three, and of >25% in one. There were no major complications related to the operative technique, including neurologic deterioration or wound infection. We conclude that single anterior screw fixation is clinically and radiologically effective and safe for type II and III odontoid process fractures. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Odontoid fracture; Anterior screw fixation; Fusion rate; Complications
1. Introduction Odontoid fractures comprise 10–15% of cervical spine fractures, and are becoming more common, mostly due to traffic accidents, with injuries of the head and neck. The neurological symptoms vary, from disturbance of sensory or motor function of the upper extremities, to quadriplegia, and require accurate diagnosis and treatment. It is reported that the nonunion rate for odontoid fractures is 4–64%1 depending on the fracture site and the method of treatment. Non-surgical treatment with cervical collar or halo-vest may provide stable support in type II fractures. Posterior fixation of C1–2 achieves a higher fusion rate compared to conservative treatment, but is a challenging surgical technique and results in limitation of
cervical range of motion after surgery. However, direct anterior screw fixation preserves rotatory motion of the cervical spine, with immediate stabilization of the spine using a simple surgical technique.2 The authors investigated the preoperative and postoperative clinical findings and radiographs, of patients with type II and type III odontoid fractures (based on the Anderson and D’Alonzo classification3) treated with anterior screw fixation to evaluate fracture alignment, union rates, radiologic and clinical outcomes, range of motion of the cervical spine, and complications. We discuss the safety and efficacy of this surgical technique. 2. Materials and methods 2.1. Patients
*
Corresponding author. Tel.: +82 64 750 1119; fax: +82 64 726 0173. E-mail address: [email protected] (K.-B. Lee).
0967-5868/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2006.06.016
This study included 16 patients, with type II and type III odontoid process fractures using the Anderson and
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
D’Alonzo classification who were treated with single anterior screw fixation, from May 1996 to October 2003. Type II fractures, and type III fractures where the fracture line starts from the base of the odontoid process to the body of C2, met the inclusion criteria. Exclusion criteria included two patients with pure type III fractures, two with type II or III fractures where the fracture line extended to the antero-inferior aspect of the C2 body, and one patient lost to follow-up. In total, 16 of 21 patient were included in the study. There were 13 male and three female patients. The age at operation ranged from 15–70 years, 36.3 years average. The cause of fracture included three falls, eight motor vehicle accidents and five pedestrian accidents. The fractures were associated with three thoracolumbar fractures, one spinous process fracture and one clavicle fracture (Table 1). Twelve patients had type II fractures, and four type III. The patterns of fractures were 10 transverse and two spiral (posterior oblique) type II fractures and two transverse and two vertical type III fractures (Table 2). Follow-up data were available for 16 patients. In all cases, the patients underwent reduction using skull traction and anterior single screw fixation, performed via cannulated screw. Variables in surgical technique were removed by all procedures being performed by a single surgeon.
Table 2 Pattern of fractures of the 16 patients according to the Anderson and D’Alonzo classification1
Transverse Spiral (posterior oblique) Total
Type II
Type III
10 2 12
2 2 4
surgery, as well as at the last follow-up. There were three criteria for radiologic fusion; the fracture line should not be visible, no angular deformity should develop, and no motion should be detected at the fracture site on the flexion-extension radiographs. The degree of displacement and angulation were measured to assess the degree of correction and fixation achieved. The range of motion of the cervical spine was measured at the last follow-up. Sex, average age, associated injuries and complications were recorded. In addition, a mal-union (angular deformity) group was included in the union group but reviewed seperately.
Table 3 Modified Robinson’s criteria4 used to assess clinical outcome Excellent
No pain and able to return to normal activities of daily living
Good
Only slight discomfort Occasional use of non-narcotic pain medication Slight reduction in activity
Fair
Mild or moderate pain necessitating immobilization in a soft collar Use of non-narcotic pain medication Limitation of activity
Poor
No relief of pain despite use of narcotic medication Severe limitation of activity
2.2. Method The follow-up period ranged from 12–88 months. The average follow-up was 41.5 months. The patients were reviewed at 4 weeks, 8 weeks, 12 weeks and then every 3 months for 12 months post-surgery. After 1 year, the outcomes were verified by radiological and physical examination every 6 months. On radiological evaluation, the fusion rate and time were examined. Anteroposterior, lateral and open-mouth radiographs were obtained before and after
825
Table 1 Summary of patients Case no.
Age
Sex
Cause
Type
Frankel grade
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
22 21 18 60 54 51 24 24 27 40 36 15 23 55 41 70
F M M M M M M M M M M M M F F M
MVA Pedes Pedes MVA MVA MVA Fall Pedes Pedes MVA Pedes Fall MVA MVA Fall MVA
II II II III III II III II II III II II II II II II
E E E E D!E E E E E E E E E E E E
MVA = motor vehicle accident, Pedes = pedestrian accident.
Complication
Non-union
Mal-union Mal-union
ROM
X-ray result
Clinical result
Associated injury
Full Full Full Full Full Full Full Full 60°rotation Full Full Full Full 60° rotation Full 40° rotation
Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion Fusion
Excellent Excellent Excellent Good Good Good Good Excellent Good Good Good Excellent Excellent Good Good Fair
Y N Y Y Y N N N N N N N N Y N
826
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
For clinical outcome evaluation, a modification of Robinson’s criteria,4 based on the status of fusion, the degree of pain relief, the neurological status, and the activities of daily living, was used (Table 3). 2.3. Surgical technique Under general anesthesia with nasal intubation, patients were placed in a supine position. Reduction was
achieved with skull traction under controlled anteroposterior and lateral fluoroscopes. The cervical spine was extended as much as possible within the confines of the fracture. The anterior approach of Southwick and Robinson4 was used in all cases and all patients were approached from the left side in order to prevent recurrent laryngeal nerve injury. Before the operation, the thyroid and cricoid cartilage was marked in order to identify the C5–C6 disc space and then a skin incision was made
Fig. 1. (A,B) Pre-operative open mouth and lateral x-rays showing type III (combined type II or III) odontoid process fracture. (C,D) Post-operative open mouth and lateral x-rays showing internal fixation with a single cannulated screw across the dens fracture. (E,F) Open mouth and lateral roentgenograms at 12 weeks after surgery showing bony unioin of the fracture site.
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
between them. Dissecting soft tissue carefully, the carotid artery was laterally retracted, and the trachea and esophagus was medially retracted, from the midline of the anterior border of the sternocleidomatoid muscle. After the anterior cervical spine was exposed, the anterior longitudinal ligament was divided axially and the anterior inferior margin of the C2 body was exposed. Biplanar intraoperative fluoroscopy was used, and with lateral fluoroscopic guidance, the guide wire was inserted from the anterior-inferior margin of the C2 body to the posterior odontoid process. The guide wire was inserted centrally so that reduction of the fracture was maintained. A
827
4.0 mm cannulated screw was inserted after only tapping the entry portal. The cannulated screw was cautiously inserted until it reached the posterior cortex of the odontoid process, avoiding proximal migration of the guide pin to prevent cord injury. 3. Results 3.1. Radiologic evaluation Bony fusion was radiologically evident in 15 of 16 patients (Fig. 1), achieved within an average 13.8 weeks
Fig. 2. (A,B) Preoperative lateral and open mouth x-ray of a 27-year-old man showing a type II odontoid process fracture. (C,D) Post-operative anterior and lateral views showing internal fixation with a single cannulated screw across the fracture. (E,F) 12 weeks later, there was non-union of the odontoid process.
828
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
(minimum 8 weeks, maximum 6 months). Two of the 15 fused patients had mal-union. One had no significant limitation of range of motion in the cervical spine, but the other showed distal migration of the screw and an anterior angular deformity, with more than 25% limited range of motion. No further surgical intervention was used for this patient who then underwent rehabilitation therapy. A patient with non-union (Fig. 2) was reoperated 3 months after surgery, by a posterior fixation (Gallie fusion) technique (Fig. 3), and ended up with satisfactory fusion. 3.2. Clinical outcome Thirteen patients had a normal range of motion in the cervical spine, two (1 mal-union, 1 non-union) had about 25% limited range of motion and one (mal-union) had more than 25% limited range of motion in the cervical spine. Six patients achieved clinically excellent outcomes, nine good and one fair outcome: thus, 94% with good or better clinical outcome in total (Table 1). 3.3. Complications There was one distal migration of the screw, two malunions, and one non-union. One patient had neurological deterioration with numbness of the forearm, but recovered after surgery. 4. Discussion Both conservative and surgical treatments can be used for odontoid process fractures, but conservative treatment results in an approximatley 25% non-union rate,5 as it is difficult to obtain stable support solely with a Halo-vest or cervical collar.6 In many patients, posterior atlanto-axial fusion with wiring and cortico-cancellous bone graft is performed as it is a simple surgical technique with high fusion
rates.7,8 This gives a satisfactory outcome, but there remains motion at the fracture site, even after fusion of C1–2, and it is reported that the non-union rate is up to 54%, due to the inflow of synovial fluid around the intact transverse ligament and alar ligament.9,10 Also, atlanto-axial posterior fusion causes about 50% of rotation limitation and about 30% of bending motion limitation, and, especially if there is an atlas ring fracture (approximately 16% of all C2 fractures), the fusion should be extended to the occiput.6 To overcome these limitations, Bo¨hler11 and Naknishi12 performed anterior fixation with two lag screws. This technique preserves the motion segment at C1–2 with a simple fixation technique and less damage to the soft tissues compared to posterior fixation; however, this technique is not useful for oblique fractures, since the compression force is not applied to the fractured segment, and is also technically demanding. The patient with a short neck or upper thoracic lordosis cannot be treated, and a fluoroscope is required throughout the operation. If the patient has cervical stenosis, there is a possibility of spinal cord injury due to hyperextension. Nielsen et al.13 reported an approximate 71% fusion rate with anterior screw fixation for odontoid process fractures, and Henry et al.14 reported a 92% fusion rate for anterior screw fixation with 81 patients, which shows the efficacy of anterior fixation; only two patients were reoperated with posterior fusion. Esses and Bednar15 introduced anterior single screw fixation; it has been said that when the distal segment of the fracture is small, it is technically demanding to obtain proper fixation, but they achieved satisfactory clinical outcomes and reported better biomechanical fixation with a single screw fixation compared to double screw fixation. In this study, the authors obtained 94% fusion rate at an average of 13.8 weeks, with anterior single screw fixation, which is similar to the outcomes with double screw fixation. As for rotatory and bending motion limitation after the operation, 13 patients
Fig. 3. (A,B) The revised 3-month post-operative lateral and open mouth x-rays showing the Gallie type posterior C1–2 arthrodesis.
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
(81%) showed normal range of motion and two (12.5%) showed less than 25% limitation. This is a better clinical outcome than that achieved using the posterior fixation technique reported by McGraw et al.6 Prudent selection of patients is important for success.16 The grade of atlantal transverse ligament damage must be considered in treating acute odontoid process fractures; if this ligament is damaged, atlanto-axial stability is not achieved using single screw fixation and fusion alone.17 The atlantal transverse ligament integrity can be assessed with radiologic or open-mouth images, or with CT scan, and more clearly with MRI, although specificity is relatively low. There have been reports of atlantal transverse ligament damage with odontoid process fractures, but this is infrequent.16 In this study, there was no delayed atlanto-axial instability due to ruptured atlantal transverse ligament. To confirm this, radiological and open mouth x-rays as well as CT scans, were performed on all patients. In addition to atlantal transverse ligament integrity, the type of odontoid process fracture is another factor influencing the success rate of surgery.18 The indication for anterior fixation of the odontoid process in types II and III fractures, is a fracture line facing downward posteriorly and obliquely. It is a contraindication if the fracture line is facing downward and anteriorly or if the oblique fracture line is in the sagittal plane.19,20 This is because mal-alignment of the screw may occur due to torsional forces during screw insertion, and also because it is not easy to obtain sufficient space for proper screw fixation in the posterior part of the odontoid process.21 In patients with transverse fracture, the threads of the screw take most of the load during extension and bending, and thus the stability of the fixation can be maintained, unless the screw is bent or fractured. After biomechanical research of anterior screw fixation, Sasso et al.22 reported that double screw fixation is no stronger than single screw fixation, and gives only about 50% stability of the intact odontoid process. This shows that it is more important to accurately identify the fracture line than relying on the number of screws used for fixation. In this study, the authors achieved 94% fusion rate with single screw fixation, which was thought to be due to the lag effect obtained during the cannulated screw insertion, by penetrating the far cortex of the odontoid process. Except for the one non-union, the high fusion rate in the other 15 patients was due to accurate reduction of the fracture line. It is still controversial whether age should be regarded as an exclusion criteria for this procedure, but Subach et al.20 reported that it is not appropriate to perform this technique on patients over 60 years, as it is difficult to maintain extension during surgery due to degeneration of the spine. However, Berlemann et al.23 and Guiot et al.24 reported that conservative treatment of fractures with more than 6 mm migration in patients over 65 years had a high non-union rate, while anterior fixation gave
829
satisfactory results (90% fusion rate), and it would be more efficient to perform this technique on elderly patients than other conservative measures. In this study, there were two patients over 60 years; one took 12 weeks for fusion with good clinical outcome, and the other had mal-union with distal migration of the screw, as well as anterior angulation. Data is limited to analyse the relationship between age and clinical outcome, and it is necessary to be cautious about applying these for clinical decisions. Studies with larger patient groups are required to identify the relationship between age, other factors, and clinical results. 5. Conclusion Anterior screw fixation, with a high fusion rate (94%) and a low complication rate, represents a highly effective surgical treatment for odontoid process fractures. However, careful preoperative planning is necessary to avoid technical pitfalls and achieve good clinical outcomes. References 1. Schweigel JF. Management of the fractured odontoid with halo thoracic bracing. Spine 1987;12:838–9. 2. Graziano G, Jaggers C, Branch CL. A comparative study of fixation techniques for type II fractures of the odontoid process. Spine 1993;18:2383–7. 3. Anderson LD, D’Alonzo RT. Fractures of the odontoid process of the axis. J Bone Joint Surg 1974;56-A:1663–74. 4. Robinson RA, Smith GW. Anterolateral cervical disc removal and interbody fusion for cervical disc syndrome. Bull Johns Hopkins Hosp 1955;96:223–4. 5. Fujji E, Kobayashi K, Hirabayashi K. Treatment in fractures of the odontoid process. Spine 1988;13:604–9. 6. McGraw RW, Rusch RM. Atlanto-axial arthrodesis. J Bone and Joint Surg 1973;55-B:482–8. 7. Brooks AL, Jenkin EB. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg 1978;60-A:279–84. 8. Griswold DM, Albright JA. Atlanto-axial fusion for instability. J Bone and Joint Surg 1978;60-A:285–92. 9. Schatzker J, Rorabeck CH. Fractures of the dens. an analysis of thirty-seven cases. J Bone Joint Surg 1971;53-B:392–404. 10. Sowthwick WO. Management of fractures of the dens, odontoid process. J Bone Joint Surg 1980;62-A:482–6. 11. Bohler J. Anterior stabilization for acute fractures and nonunion of the dens. J Bone Joint Surg 1982;64-A:18–27. 12. Nakanishi T, Sasaki T. Internal fixation for the odontoid fractures. Orthop Trans 1977;59:940–3. 13. Nielsen OJ, Edal AL. Anterior screw fixation of fractures of the dens axis. Ugeskr Laeger 2001;163:2140–3. 14. Henry AD, Bohly J. Fixation of odontoid fractures by an anterior screw. J Bone Joint Surg 1999;81-B:472–7. 15. Esses SI, Bednar D. Screw fixation of odontoid fractures and nonunion. Spine 1991;16:483–5. 16. Lee S-C, Chen J-F. Management of acute odontoid fractures with single anterior screw fixation. J Clin Neurosci 2004;11:890–5. 17. Greene KA, Dickman CA. Transverse atlantal ligament disruption associated with odontoid fractures. Spine 1994;19:2307–14. 18. Sasso R, Doherty BJ, Crawford MJ. Biomechanics of odontoid fracture fixation. Comparison of the one and two-screw technique. Spine 1993;18:1950–3.
830
K.-J. Song et al. / Journal of Clinical Neuroscience 14 (2007) 824–830
19. Max A, Christian E, Michael C. Fractures of the odontoid process. Treatment with anterior screw fixation. Spine 1989;14: 1065–70. 20. Subach BR, Morone MA, Haid RW. Management of acute odontoid fractures with single-screw anterior fixation. Neurosurgery 1999;45: 812–9. 21. Dickman CA, Marciano FF. Principles of Spinal Surgery, Vol. 1. New York: McGraw-Hill; 1996., pp.123–39.
22. Sasso R, Doherty BJ. Biomechanics of odontoid fracture fixation. Spine 1993;18:1950–3. 23. Berlemann U, Schwarzenbach O. Dens fractures in the elderly. Results of anterior screw fixation in 19 elderly patients. Acta Orthop Scand 1997;68:319–24. 24. Guiot B, Fessler RG. Complex atlantoaxial fractures. J Neurosurg 1999;91:139–43.