SPINE Volume 39, Number 10, pp E630-E636 ©2014, Lippincott Williams & Wilkins

DIAGNOSTICS

Is It Possible to Evaluate the Parameters of Cervical Sagittal Alignment on Cervical Computed Tomographic Scans? Hyo Sub Jun, MD,* In Bok Chang, MD, PhD,* Joon Ho Song, MD, PhD,* Tae Hwan Kim, MD,† Moon Soo Park, MD, PhD,† Seok Woo Kim, MD, PhD,† and Jae Keun Oh, MD*

Study Design. Retrospective study. Objective. The purpose of this study was to analyze the relationship of the parameters of cervical sagittal alignment between those obtained from cervical CT and those obtained from radiography, as well as to determine which parameter would help predict physiological lordosis of the cervical spine. Summary of Background Data. Sagittal balance in the cervical spine is as important as the pelvic incidence and is related to the concept of T1 slope. However, many articles including this article based on unclear cervical x-ray radiographs could weakly explain the parameters. To overcome the fundamental limitation of x-ray radiographs, Hallym University Sacred Heart Hospital reported the strong correlation between T1 slope and cervical lordosis on the cervical dimensional CT scans like result by checking by the cervical x-ray radiographs. Methods. A retrospective analysis of data from 50 asymptomatic adults in whom both cervical CT scans and cervical radiograph were obtained at the same time. The T1 slope, Cobb angle C2–C7, neck tilt, and thoracic inlet angle (TIA) obtained from the CT scans and radiographs were assessed. Results. The T1 slope on x-ray was significantly correlated with the T1 slope on CT. The mean of the T1 slope on x-ray was larger than the mean of the T1 slope on CT (3.3° ± 6.1°). More cervical spine lordosis was evident on the cervical radiograph than on the cervical CT scan (5.93° ± 9.0°). No significant difference was seen between the TIA on x-ray and the TIA on CT (TIA on x-ray − TIA on CT, −0.1 ± 7.6, P = 0.959).

From the Departments of *Neurosurgery and †Orthopedics, Hallym University Sacred Heart Hospital, Anyang, Korea. Acknowledgment date: October 28, 2013. First revision date: January 2, 2014. Second revision date: February 5, 2014. Acceptance date: February 6, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No relevant financial activities outside the submitted work. Address correspondence and reprint requests to Jae Keun Oh, MD, Department of Neurosurgery, Hallym University Sacred Heart Hospital, 896 Pyeongchon-dong, Dongan-gu, Anyang-si, Gyeonggi-do 421-070, Korea; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000281

E630

Conclusion. This difference may be due to the differing effect of gravity upon the spine between the upright versus the supine position. Accordingly, TIA and T1 slope may be used as a guide for the assessment of sagittal balance of the cervical spine. Key words: T1 slope, cervical sagittal alignment, thoracic inlet angle, CT scan. Level of Evidence: N/A Spine 2014;39:E630–E636

T

he sagittal balance of the physiologically upright spine maintains alignment with a minimum of energy expenditure against the global axis of gravity.1–6 Imbalance of the spine in the sagittal plane is an important factor for the development of clinical symptoms, degenerative disease, and in the planning of perioperative care.7 Many studies have reported that the pelvic incidence (PI), a constant morphological parameter in an individual, had a significant influence on the orientation parameters of the lumbar spine or the thoracic spine such as lumbar lordosis and thoracic kyphosis.2–5,8–10 Sagittal balance in the cervical spine is increasingly important in common with the PI and is related to the concept of T1 slope.11 Updated parameters include thoracic inlet angle (TIA), neck tilt (NT), and T1 slope. It has been shown that these parameters affect the alignment of the cervical spine. The T1 slope is a landmark of overall spinal sagittal balance and is as critical an issue as the relationship between the PI and lumbar lordosis.12,13 Lee et al5 reported that the TI alignment was significantly correlated with the craniocervical sagittal balance by using x-ray measurement. To preserve physiological NT around 44°, large TIA increased T1 slope and cervical lordosis and vice versa. TIA and T1 slope can be used as parameters to predict physiological alignment of the cervical spine. The T1 slope, to the best of our knowledge, is a newly studied concept. Even in studies dedicated in the analysis of the TIA and the first thoracic spine, the T1 slope, obtained from an upright plain radiograph of the cervical spine, cannot be measured accurately enough due to the anatomical interference of the shoulder contour density especially in obese people with thick thoraces. Most of the prior research collected

www.spinejournal.com

May 2014

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131263_LR E630

09/04/14 11:51 PM

DIAGNOSTICS T1 slope data from unclear x-ray radiographs. To overcome the fundamental limitations of x-ray radiographs, Park et al14 reported the cervical dimensional CT scans of asymptomatic subjects. They reported the change in NT due to aging as well as the T1 slope, C2–C7 angle, sagittal vertical axis C2–C7. However, the values presented in their study were obtained in the supine position, not in the upright position. To the best of our knowledge, none have reported the relationship of the parameters of cervical sagittal alignment between cervical CT data and radiographical data. The purpose of this study is to analyze the relationship of the parameters of cervical sagittal alignment between those obtained from cervical CT and those from radiograph, as well as to determine which parameter would help predict physiological lordosis of the cervical spine.

MATERIALS AND METHODS A retrospective analysis of data from 50 asymptomatic adults, aged between 24 and 80 years, who visited our ENT outpatient department between January 2010 and September 2012, have never been diagnosed with or treated for a spinal problem, and had both cervical CT scans and cervical radiograph obtained at the same time, was done. The male to female ratio was 30:20 and the mean age was 47.84 ± 15.5. Standing lateral radiograph of the cervical spine was obtained with the subject in a comfortable upright position, the upper extremities positioned naturally at the side of the body, and a horizontal gaze parallel to the Frankfurt horizontal plane. The radiograph covered an area from the orbit to the T3 vertebra vertically and from the maxilla to the occiput horizontally.15 The cervical CT scans (Brilliance CT 64-channel scanner; Philips Electronics, Cleveland, OH) were obtained intertemporally with the subject in a comfortable supine position and gazing at the ceiling. Data from both imaging techniques that were analyzed included the T1 slope, C2–C7 angle, NT, and TIA.

Cervical Parameters Thoracic Inlet Angle, NT, T1 Slope, and C2–C7 Angle As a constant morphological parameter not influenced by posture, the TIA was defined as an angle formed by a line from the center of the T1 upper endplate (T1UEP) vertical to the T1UEP and a line connecting the center of the T1UEP and the upper end of the sternum (Figures 1, 2). As an orientation parameter influenced by posture, the T1 slope was defined as an angle formed between the horizontal plane and the T1UEP. NT was defined as an angle formed by a vertical line passing through the upper end of the sternum and a line connecting the center of the T1UEP and the upper end of the sternum. Geometrically, the formula “TIA = T1S + NT” was derived (Figure 1), similar to “PI = SS (sacral slope) + pelvic tilt.”5,16 The C2–C7 angle was measured by formal Cobb methods that checked the angle between the horizontal line of C2 lower endplate and the horizontal line of C7 lower endplate.9 The radiographical parameters were measured using standard techniques recommended by the Scoliosis Research Society. Spine

Parameters of Cervical Sagittal Alignment on Cervical CT Scan • Jun et al

Statistical Analysis The picture archiving and communication system (PView; INFINITT, Seoul, Korea) was determined by 2 independent observers for the measurement. After agreement between the observers, each parameter was independently measured twice by 2 spinal surgeons from the neurosurgery department and the linear correlation coefficient was analyzed. The correlations of the various parameters between those obtained from the cervical CT scan and those from the radiograph were analyzed using the Pearson correlation coefficient, paired t test and linear regression models. The SPSS version 19.0 (IBM SPSS, Armonk, NY) was used for statistical analysis and a P < 0.05 was considered significant.

RESULT Cervical Parameters

The mean TIA on x-ray (TIAX) was 75.09° ± 8.1° (range, 58.0°–92.74°) and the mean T1 slope on x-ray (T1SX) was 25.97° ± 5.9° (range, 13.4°–40.63°). The mean NT on x-ray (NTX) was 48.7° ± 7.9° (range, 13.5°–40.6°). The mean TIAX was 74.7° ± 8.4° (range, 54.4°–92.5°). The mean TIA on CT (TIACT) was 74.7° ± 9.0° (range, 54.4°–92.5°). The mean T1 slope on CT (T1SCT) was 22.7° ± 7.2° (range, 6.3°– 37.4°). The mean NT on CT (NTCT) was 52.03° ± 7.41° (range, 35.4°–65.7°). The mean C2–C7 angle on x-ray (C27 alignmentX) was 17.3° ± 9.3° (range, 2.3°–35.0°). The mean C2–C7 angle on CT (C27 alignmentCT) was 11.35° ± 9.3° (range, 2.0°–37.0°). All the parameters of the TI alignment showed a normal distribution (Table 1).

Correlations of the Parameters

The TIAX had significant correlations with the age (r = 0.386), T1SX (r = 0.435), and NTX (r = 0.746). The TIAX had no significant correlation with the C27 alignmentX. The TIACT had significant correlations with the age (r = 0.379), T1SCT (r = 0.607), NTCT (r = 0.624), and C27 alignmentCT (r = 0.412). The TIACT had no significant correlation with the C27 alignment. Also, it demonstrated significant correlation between the T1SX and the T1SCT(r = 0.582).

Figure 1. Schematic drawing of the cervical parameters. www.spinejournal.com

E631

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131263_LR E631

09/04/14 11:51 PM

DIAGNOSTICS

Parameters of Cervical Sagittal Alignment on Cervical CT Scan • Jun et al

Figure 2. Schematic drawing of the cervical parameters. A, Parameters on radiograph. B, Parameters on CT scan. a denotes neck tilt shown on radiograph (neck tilt X); b, T1SX; c, (TIAX); d, C2–C7 angle shown on radiograph (C27 alignmentX); e, Neck tilt shown on CT scan (neck tilt CT); f, T1SCT; g, TIACT; h, C2–C7 angle shown on CT scan (C27 alignmentCT). T1SX indicates T1 slope on x-ray; T1SCT, T1 slope on CT; TIAX, thoracic inlet angle on x-ray; TIACT, thoracic inlet angle on CT.

The T1SX had significant correlations with the C27 alignmentCT (r = 0.508) and the TIACT (r = 0.351). The NTX had significant correlations with the NTCT (r = 0.585) and the TIACT (r = 0.410). The C27 alignmentX had significant correlations with the T1 slope CT (r = 0.407), C27 alignmentCT (r = 0.602), and TIACT (r = 0.341). The TIAX had significant correlations with the T1SCT (r = 0.323), NTCT (r = 0.448), and TIACT (r = 0.627) (Table 2). With the paired t test, the difference of the mean between the T1SX and the T1SCT (T1SX − T1SCT) was 3.3° ± 6.1°. The difference of the mean between the NTX and the NTCT (NTX − NTCT) was −3.3° ± 7.0°. The difference of mean between the C27 alignmentX and the C27 alignmentCT (C27 alignmentX − C27 alignmentCT) was 5.93° ± 9.0°.

No significant difference was seen between the TIAX and the TIACT (TIAX − TIACT, −0.1 ± 7.6, P = 0.959) (Table 1).

Linear Regression Model With a linear regression analysis, statistically significant linear regression models were established by using the following formulae: [T1SCT = 3.876 + (0.725 × T1SX)]; [NTCT = 25.365 + (0.547 × NTX)]; [C27 alignmentCT = −0.164 + (0.667 × C27 alignmentX)]; and [TIACT = 24.545 + (0.72 × TIAX)] (Figure 3).

DISCUSSION Alteration of the normal cervical lordosis, thoracic kyphosis, and lumbar lordosis has been associated with pain and accelerated disc degeneration.17–20 Thus, questions pertaining to

TABLE 1. Mean, SD, Paired t Test of the Cervical Parameters Radiographical Value (Mean ± SD)

CT Value (Mean ± SD)

Paired Difference of Mean (Radiographical Values − CT Value)

P

T1 slope

25.97° ± 5.9°

22.7° ± 7.2°

3.27°

0.000

NT

48.7° ± 7.9°

52.03° ± 7.4°

−3.32°

0.002

C2–C7 angle

17.3° ± 9.3°

11.35° ± 9.3°

5.92°

0.000

TIA

75.09° ± 8.1°

74.7° ± 9.0°

7.57°

0.959

CT indicates computed tomography; SD, standard deviation; TIA, thoracic inlet angle.

E632

www.spinejournal.com

May 2014

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131263_LR E632

09/04/14 11:51 PM

DIAGNOSTICS

Parameters of Cervical Sagittal Alignment on Cervical CT Scan • Jun et al

TABLE 2. Pearson Correlation Coefficient and P Value Correlations Age

T1SX

NTX

C27 alignmentX

TIAX

T1SCT

NTCT

C27 alignmentCT

TIACT

1

0.162

0.293*

0.245

0.386*

0.228

0.240

0.164

0.379†

0.261

0.039

0.086

0.006

0.112

0.094

0.225

0.007

50

50

50

50

50

50

50

50

1

−0.276

0.510†

0.435†

0.582†

−0.144

0.508†

0.351*

0.053

0.000

0.002

0.000

0.320

0.000

0.012

50

50

50

50

50

50

50

1

0.093

0.746†

−0.086

0.585†

−0.150

0.410†

0.520

0.000

0.554

0.000

0.298

0.003

50

50

50

50

50

50

1

0.266

0.407†

0.016

0.602†

0.341*

0.062

0.003

0.912

0.000

0.015

50

50

50

50

50

1

0.323*

0.448†

0.212

0.627†

0.022

0.001

0.140

0.000

50

50

50

50

1

−0.242

0.648†

0.607†

0.090

0.000

0.000

50

50

50

1

−0.134

0.624†

0.353

0.000

50

50

1

0.412†

Age Pearson correlation P (2-tailed) N

50

T1SX Pearson correlation P (2-tailed) N

50

NTX Pearson correlation P (2-tailed) N

50

C27 alignmentX Pearson correlation P (2-tailed) N

50

TIAX Pearson correlation P (2-tailed) N

50

T1SCT Pearson correlation P (2-tailed) N

50

NTCT Pearson correlation P (2-tailed) N

50

C27 alignmentCT Pearson correlation P (2-tailed) N

0.003 50

50

TIACT Pearson correlation

1

P (2-tailed) N

50

*Correlation is significant at the 0.05 level (2-tailed). †Correlation is significant at the 0.01 level (2-tailed). T1SX indicates T1 slope on x-ray; T1SCT, T1 slope on CT; TIAX, thoracic inlet angle on x-ray; TIACT, thoracic inlet angle on CT; CT, computed tomography; NTX, neck tilt on x-ray.

Spine

www.spinejournal.com

E633

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131263_LR E633

09/04/14 11:51 PM

DIAGNOSTICS

Parameters of Cervical Sagittal Alignment on Cervical CT Scan • Jun et al

Figure 3. Linear regression analysis of the parameters showed statistically significant relationships between the radiographical and CT parameters. A, T1 slope. B, NT. C, C2–C7 angle. D, TIA. CT computed tomography; TIA, thoracic inlet angle; NT, neck tilt; T1SCT indicates T1 slope on CT; NTCT, neck tilt on CT; C27 alignmentCT, C2–C7 angle on CT; TIACT, thoracic inlet angle on CT.

the proper assessment of the normal spine in the sagittal plane remain a topic of discussion among various authors. The T1 slope and the other cervical parameters have been identified as the radiographical parameters that were highly correlated with the cervical sagittal balance. Lee et al5 reported that the TIA and T1 slope could be used to predict physiological alignment of the cervical spine on radiograph. Although T1 slope is influenced by aging or posture, it is not a constant parameter. On the contrary, TIA does not change with position or increase of thoracic kyphosis under any condition, similar to the PI of the pelvis. They concluded that the C2–C7 angle increases with increasing T1 slope by radiography. Articles, including this article, obtained data from unclear cervical x-ray radiographs and as a result, could only weakly explain the T1 slope, NT, and TIA because of the nonvisualization of the sternum tip contour in targeted patients. This means that it is difficult to justify the relationship between the T1 slope and cervical lordosis.12,13 Park et al14 assessed the sagittal parameters of the cervical spine using CT scans in supine position and concluded that the C2–C7 angle increased as the E634

T1 slope got higher. They also reconfirmed that the TIA can be considered as a fixed reference value. We compared the various cervical parameters obtained from cervical x-ray radiographs in the upright position and those from cervical CT scans in the supine position, with both radiographs being obtained at the same time. The Pearson correlation coefficient and linear regression models in this study found that the TIAX was strongly correlated with TIACT and that the T1SX was strongly correlated with T1SCT. In addition, significant correlation was observed between (NTX: NTCT) and (C27 alignmentX: C27 alignmentCT). According to the formula used in previous articles, TIA = T1S + NT, we reconfirmed that a large TIA increases the T1S and finally, increases the cervical lordosis (= C2–C7 angle) in both radiographical and CT data. The parameters obtained from the cervical CT scan in the supine position can be used to predict the parameters obtained from the upright position cervical radiograph. Also, we could figure out the difference between these 2 ways of the parameter. The analysis of the paired t test in this study found that the mean of the T1SX was larger than

www.spinejournal.com

May 2014

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131263_LR E634

09/04/14 11:51 PM

DIAGNOSTICS the mean of the T1SCT (3.3° ± 6.1°) and the mean of the NTX was smaller than NTCT (−3.3° ± 7.0°). A greater cervical spine lordosis was seen in the radiographical data than the CT data (C27 alignmentX − C27 alignmentCT : 5.9° ± 9.0°). This difference may be due to the differing effect of gravity upon the spine between the upright versus the supine position. We noticed the decided difference between the 2 parameters. It can help to make an accurate estimate. No significant difference between the TIAX (75.09° ± 8.1°) and the TIACT (74.7° ± 9.0°) (TIAX − TIACT, −0.1 ± 7.6, P = 0.959) was seen. We were able to reconfirm that the TIA was a constant morphological parameter in this study. The TIA was a constant parameter because, anatomically, the cervical spine is placed on top of the TI, a fixed circular bony structure without range of motion that is composed of the T1 vertebral body, the first ribs on both sides and the upper part of the sternum.16 The sagittal balance of the cervical spine adjusts and can be influenced by the shape and orientation of T1 to obtain a balanced upright posture and proper horizontal gaze like the PI in the pelvis. The TIAX and TIACT may be important anatomical landmarks that can be used to predict, as well as important morphological parameters that can affect the physiological sagittal alignment of the cervical spine. Anterior cervical fusion surgery is performed in the supine position and the reconstruction of lordosis during fusion surgery is also performed in the lying position. Each of the cervical sagittal parameter obtained from the radiograph in the upright position can be estimated using the corresponding parameters obtained from the CT scan in the supine position. Knowing the differences in the various cervical sagittal parameters between those from the radiograph and those from the CT scan, a spinal surgeon can make the proper fusion angle for optimal cervical sagittal balance in the upright position even if the surgery was done in the lying position. This could result in better postoperative outcomes than those without optimal fusion angle. A limitation of this study is the uneven distribution of age and sex of the cohort. To estimate the result for a normative cohort, we excluded individuals with degenerative change in the cervical spine or global sagittal imbalance and included only 50 individuals. Additional study with a larger number of cases will be needed to be able to make an age, bodyweight, height, and sex-matched controlled investigation and confirm the result of this study. Also, an active discussion about the T1 slope and cervical sagittal alignment is in progress. So, there is no “gold standard” yet. Additional investigation of cervical alignment is necessary. For example, the in vivo angle in cadaveric study may help to explain the relationship between T1 slope and cervical sagittal alignment and set the “gold standard” of cervical sagittal parameters.

CONCLUSION We could reconfirm that large TIA increase T1S and finally increase cervical lordosis (= C2–C7 angle) in the data of both radiograph and CT scan. We also reconfirmed that the Spine

Parameters of Cervical Sagittal Alignment on Cervical CT Scan • Jun et al

TIA was a constant morphological parameter. The mean of the T1SX was larger than the mean of the T1SCT (3.3°) and the mean of the NTX was smaller than the NTCT (−3.30°). More cervical spine lordosis was found on radiograph than on CT scan (C27 alignmentX − C27 alignmentCT: 5.9°). We think that the difference in the degree of cervical spine lordosis seen between the radiograph and CT scan may be due to the differing effect of gravity upon the spine between the upright versus the supine position. One of the principle goals of cervical fusion or reconstructive spine surgery is to restore the correct alignment and balance of the cervical spine. The TIA and T1S may be used as a guide for the assessment of sagittal balance of the cervical spine or in the reconstruction of lordosis during fusion surgery.

➢ Key Points ‰ The strong correlation between T1 slope and cervical lordosis on the cervical dimensional CT scans like result by checking by the cervical x-ray radiographs. ‰ The T1SX was significantly correlated with the T1SCT. The mean of the T1SX was larger than the mean of the T1SCT (3.3° ± 6.1°). ‰ More cervical spine lordosis was evident on the cervical radiograph than on the cervical CT scan (5.93° ± 9.0°). ‰ No significant difference was seen between the TIAX and the TIACT (TIAX − TIACT, −0.1 ± 7.6, P = 0.959). ‰ TIA and T1S may be used as a guide for the assessment of sagittal balance of the cervical spine.

References

1. Duval-Beaupere G, Schmidt C, Cosson P. A Barycentremetric study of the sagittal shape of spine and pelvis: the conditions required for an economic standing position. Ann Biomed Eng 1992;20: 451–62. 2. Legaye J, Duval-Beaupere G, Hecquet J, et al. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J 1998;7:99–103. 3. Vaz G, Roussouly P, Berthonnaud E, et al. Sagittal morphology and equilibrium of pelvis and spine. Eur Spine J 2002;11:80–7. 4. Berthonnaud E, Dimnet J, Roussouly P, et al. Analysis of the sagittal balance of the spine and pelvis using shape and orientation parameters. J Spinal Disord Tech 2005;18:40–7. 5. Lee SH, Kim KT, Seo EM, et al. The influence of thoracic inlet alignment on the craniocervical sagittal balance in asymptomatic adults. J Spinal Disord Tech 2012;25:E41–7. 6. Vital JM, Senegas J. Anatomical bases of the study of the constraints to which the cervical spine is subject in the sagittal plane. A study of the center of gravity of the head. Surg Radiol Anat 1986;8: 169–73. 7. Ferrara LA. The biomechanics of cervical spondylosis. Adv Orthop 2012;2012:493605. 8. Roussouly P, Gollogly S, Berthonnaud E, et al. Classification of the normal variation in the sagittal alignment of the human lumbar www.spinejournal.com

E635

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131263_LR E635

09/04/14 11:51 PM

DIAGNOSTICS

9. 10. 11. 12. 13. 14.

spine and pelvis in the standing position. Spine (Phila Pa 1976) 2005;30:346–53. Vialle R, Levassor N, Rillardon L, et al. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. J Bone Joint Surg Am 2005;87:260–7. Boulay C, Tardieu C, Hecquet J, et al. Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis. Eur Spine J 2006;15:415–22. Johnson GM. The correlation between surface measurement of head and neck posture and the anatomic position of the upper cervical vertebrae. Spine (Phila Pa 1976) 1998;23:921–7. Gelb DE, Lenke LG, Bridwell KH, et al. An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976) 1995;20:1351–8. Jang JS, Lee SH, Min JH, et al. Surgical treatment of failed back surgery syndrome due to sagittal imbalance. Spine (Phila Pa 1976) 2007;32:3081–7. Park JH, Cho CB, Song JH, et al. T1 slope and cervical sagittal alignment on cervical CT radiographs of asymptomatic persons. J Korean Neurosurg Soc 2013;53:356–9.

E636

Parameters of Cervical Sagittal Alignment on Cervical CT Scan • Jun et al

15. Lundstrom A, Lundstrom F. The Frankfort horizontal as a basis for cephalometric analysis. Am J Orthod Dentofacial Orthop 1995;107:537–40. 16. Urschel HC Jr. Anatomy of the thoracic outlet. Thorac Surg Clin 2007;17:511–20. 17. Boseker EH, Moe JH, Winter RB, et al. Determination of “normal” thoracic kyphosis: a roentgenographic study of 121 “normal” children. J Pediatr Orthop 2000;20:796–8. 18. Jackson RP, McManus AC. Radiographic analysis of sagittal plane alignment and balance in standing volunteers and patients with low back pain matched for age, sex, and size. A prospective controlled clinical study. Spine (Phila Pa 1976) 1994;19: 1611–8. 19. Knott PT, Mardjetko SM, Techy F. The use of the T1 sagittal angle in predicting overall sagittal balance of the spine. Spine J 2010;10:994–8. 20. Rose PS, Bridwell KH, Lenke LG, et al. Role of pelvic incidence, thoracic kyphosis, and patient factors on sagittal plane correction following pedicle subtraction osteotomy. Spine (Phila Pa 1976) 2009;34:785–91.

www.spinejournal.com

May 2014

Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE131263_LR E636

09/04/14 11:51 PM

Is It Possible to Evaluate the Parameters of Cervical Sagittal Alignment on Cervical CT scan?

Study Design. Retrospective analysis of existing cervical radiographsObjective. The purpose of this study was to analyze the relationship of the param...
1MB Sizes 0 Downloads 3 Views