ORIGINAL ARTICLE
Three-dimensional Computed Tomography for Determination of Femoral Anteversion in a Cerebral Palsy Model Anthony I. Riccio, MD,* CDR Joseph Carney, MD, USN,w LCDR Nathan Hammel, MD, USN,w Mark Stanley, MD,w Jeffrey Cassidy, MD,z and Jon R. Davids, MDy
Background: Previous investigation has proven 3-dimensional (3D) computed tomography (CT) to be a poor method of assessing femoral anteversion in patients with cerebral palsy. However, new advancements in CT software yield the potential to improve upon those dated results. Methods: CT was performed on 9 femoral models with varying amounts of anteversion (20 to 60 degrees) and varying neck-shaft angles (120 to 160 degrees). Each model was scanned in 2 holding devices. One holder placed the femur in an ideal position relative to the gantry. The other placed the femur in flexion, adduction, and internal rotation simulating a common lower extremity posture in cerebral palsy. Femoral anteversion was measured on 3D reconstructions by 4 observers on 2 separate occasions. Interobserver and intraobserver reliability, accuracy, and the effect of increasing neck-shaft angle of the measurements were examined and compared with previously published data using the same models. Results: Pearson correlation coefficients between first and second measurements by the same examiner were all above 0.96 regardless of positioning of the femur in the gantry. The correlation coefficients among all examiners were 0.97 regardless of positioning of the femur in the gantry. Accuracy in measurements was comparable using 3D CT techniques with mean differences between the normal and cerebral palsy-positioned models of 10 degrees from the standard measurement. The Fisher exact test was used to compare the proportions placed into these 3 categories on the basis of the CT assessment. Again, an a of r0.05 was considered indicative of a significant difference. FIGURE 2. Computed tomography produced 3-dimensional shaded surface display of femur model.
tween the femoral neck and the femoral condyles was measured digitally with one line connecting the posterior condyles and the other line paralleling the mid portion of the neck (Fig. 3). This angle for each model was measured on an AGFA picture archiving system by 4 examiners on 2 separate occasions. The examiners consisted of 1 orthopaedic pediatric staff surgeon, 1 musculoskeletal radiology staff, and a resident from each program.
Statistical Methods The intraobserver and interobserver reliability of the 2D and 3D techniques for measurement of both the normally aligned and the cerebral palsy positioned models were assessed by calculating the Pearson correlation coefficients and the mean differences (and SDs) between measurements within and between examiners with comparison using t test analysis. The accuracy of the various CT measurement techniques under the various conditions was determined
RESULTS 3D CT Intraobserver Reliability The correlation coefficients between the first and second femoral anteversion measurements by the same examiner (intraobserver reliability) were all above 0.96 (excellent correlation) for the 3D scans regardless of the position of the femur in the scanner when using the newer generation 3D CT software technology. The corresponding femoral anteversion mean differences between first and second measurements were 2.4 degrees (SD = 2.1 degrees) for the normal positioned femurs and 2.0 degrees (SD = 2.4 degrees) for the cerebral palsy-positioned femurs (P = 0.321).
3D CT Interobserver Reliability The correlation coefficients among examiners measuring femoral anteversion were all above 0.97 (excellent correlation) for the 3D scans regardless of the position of the femur in the scanner when using the newer generation 3D CT software technology. The corresponding femoral anteversion mean differences among examiners were 3.3 degrees (SD = 1.9 degrees) for the normal positioned femurs and 3.2 degrees (SD = 1.4 degrees) for the cerebral palsy-positioned femurs (P = 0.886). Interobserver reliability for the 2D CT technique was described in the senior author’s previous work.32
Accuracy
FIGURE 3. Measurement of femoral anteversion on 3-dimensional computed tomography image by determining angle between the femoral neck and the femoral condyles. Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
Femoral anteversion measurement, as evaluated on a continuous scale, of the optimally and suboptimally positioned femurs was accurate when using the newer generation 3D CT software. The absolute femoral anteversion mean difference was 3.6 degrees (SD = 3.3 degrees) between the direct measurements of femoral anteversion and the optimally positioned femurs measured with the 3D CT technique, and 3.0 degrees (SD = 3.1 degrees) between the direct measurements of femoral anteversion and the suboptimally positioned femurs measured with the 3D CT technique (P = 0.228). As evaluated on a clinical categorical scale, the accuracy of the 3D CT for determining femoral anteversion in optimal alignment compared with the suboptimal alignwww.pedorthopaedics.com |
169
J Pediatr Orthop
Riccio et al
FIGURE 4. Accuracy of 3-dimensional computed tomography with postimaging processing for determining femoral anteversion in normal alignment compared with typical cerebral palsy alignment. Values are number of measurements falling within the clinical accuracy categories. No significant difference was found between measurement categories when comparing the 2 positions. (P = 0.907).
ment was comparable with no significant difference found between measurement categories (P = 0.907) (Fig. 4). Cerebral palsy alignment significantly compromised the accuracy of the 2D technique, with only one 2D measurement falling within 5 degrees of the standard measurements. When evaluating the accuracy of 2D CT femoral anteversion measurement compared with the 3D measurement technique, the 3D technique was found to be significantly more accurate using the clinical categorical scale in measuring the typical cerebral palsy positioned femurs (P < 0.0001) (Fig. 5).
DISCUSSION Techniques for accurately assessing femoral anteversion in children with cerebral palsy affected hips have
FIGURE 5. Accuracy of 2-dimensional computed tomography versus 3-dimensional computed tomography for determining femoral anteversion in typical cerebral palsy alignment. Values are number of measurements falling within the clinical accuracy categories. Three-dimensional computed tomography with postimaging processing was found to be significantly more accurate when comparing clinical accuracy measurement categories between the 2 techniques (P < 0.0001).
170 | www.pedorthopaedics.com
Volume 35, Number 2, March 2015
not been found to be consistently accurate to date. CT has long been considered the best method to determine anteversion in children with cerebral palsy, yet limitations with this technique exist. In a previous publication by the senior author it was established that cerebral palsy patients with the typical flexed, adducted, and internally rotated posture of the hip present challenges in accurately determining femoral anteversion angles due to suboptimal positioning in the scanner that cannot be remedied with early-generation 3D CT systems.32 Recently, newer reconstruction software systems have become available for CT that provide the radiologist and clinician with the ability to subtract and manipulate images in a potentially more accurate manner with 3D output. Using the newly available reconstruction software for modern CT, we demonstrated near-perfect interobserver and intraobserver reliability with an accuracy throughout femoral architecture and femur positioning within 1 SD of the actual measurement of the femoral anteversion. Further, there was a statistical accuracy advantage of the 3D measurements over the historical 2D modeling when the femur was held in an abnormal position relative to the gantry replicating a common set of contractures in cerebral palsy. These findings represent an advancement in evaluating femoral anteversion in cerebral palsy patients that has not been previously described. In this study, intraobserver and interobserver reliability was found to be excellent for the 3D CT technique when assessing femoral anteversion regardless of the position of the femurs in the scanner, femoral anteversion angle, or the neck-shaft angle. Furthermore, measurement of femoral anteversion using the 3D technique in this study was accurate regardless of positioning of the femurs, severity of femoral anteversion, or abnormality of the neck-shaft angle of the femurs when evaluated both on a continuous scale and when evaluated with a clinical categorical scale. When evaluating accuracy using the clinical categorical scale, the 3D CT technique was accurate in determining femoral anteversion angles regardless of patient positioning (Fig. 4). Furthermore, the 3D CT technique was significantly more accurate in determining femoral anteversion angles in the cerebral palsypositioned femurs than the 2D CT technique (Fig. 5). As radiation exposure to pediatric patients is always a concern, it should be noted that the generation of 3D imaging does not impart any increased radiation dose upon the patient in comparison with standard 2D imaging. At our institution, all CT studies are obtained using volumetric scanning. Every extremity examination is therefore performed using a 0.6 mm spiral acquisition. The data obtained may then be reconstructed in any manner the radiologist chooses. As image processing occurs following standard data acquisition, the radiation dose to the patient is equivalent regardless of whether only 2D images are obtained or the data are formatted into axial, sagittal, and coronal images with 3D reconstructions. Furthermore, as the generation of 3D images is performed by data manipulation, obtaining these images at our institution is at no increased cost to the patient or the institution. Understandably, this may vary Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 35, Number 2, March 2015
from institution to institution based upon whether those facilities bill for the increased time it takes their radiation technologists to format 3D reconstructions. The authors do acknowledge certain limitations in this study. Models used in this research endeavor were cast from adult femurs. The casting may have provided for better-developed anatomic landmarks than pediatric femurs and therefore, when evaluating the cerebral palsy patient femur anatomic landmarks may be more challenging to decipher than our models creating potentially less accuracy and reliability in the method than we found. However, it can be argued that no other currently well-accepted diagnostic evaluation technique can provide better visualization of the 3D contour of the femur bone than 3D CT imaging. Another potential limitation is that image manipulation requires specific software, which can be a limitation for clinical applicability in certain treatment centers. However, the software used in this study is widely available and expected to grow in use rather than decrease in use as health care systems evolve. We conclude that despite the inability to position a child optimally in a CT scanner, a 3D reconstruction with postimaging processing to align the femur along its axis for measurement of anteversion is superior in utilizing sequential 2D reconstructions. The technique is highly accurate and possesses near-perfect reliability. We therefore recommend 3D reconstructions with appropriate postimaging processing when evaluating femoral anteversion angles in children with contractures who cannot be positioned acceptably in the CT scanner. REFERENCES 1. Aktas S, Aiona M, Orendurff M. Evaluation of rotational gait abnormality in patients with cerebral palsy. J Pediatr Orthop. 2000;20:217–220. 2. Gage JR, DeLuca PA, Renshaw TS. Gait analysis: principle and applications with emphasis on its use in cerebral palsy. Instr Course Lect. 1996;45:491–507. 3. Ruwe PA, Gage JR, Ozonoff MB, et al. Clinical determination of femoral anteversion. A comparison with established techniques. J Bone Joint Surg Am. 1992;74:820–830. 4. Fabry G, MacEwen GD, Shands AR Jr. Torsion of the femur. A follow-up study in normal and abnormal conditions. J Bone Joint Surg Am. 1973;55:1726–1738. 5. Beals RK. Developmental changes in the femur and acetabulum in spastic paraplegia and diplegia. Dev Med Child Neurol. 1969;11: 303–313. 6. Staheli LT, Duncan WR, Schaefer E. Growth alternations in the hemiplegic child. A study of femoral anteversion, neck-shaft angle, hip rotation, C.E. angle, limb length and circumference in 50 hemiplegic children. Clin Orthop. 1968;60:205–212. 7. Gelberman RH, Cohen MS, Desai SS, et al. Femoral anteversion. A clinical assessment of idiopathic intoeing gait in children. J Bone Joint Surg Br. 1987;69:75–79. 8. Staheli LT, Corbett M, Wyss C, et al. Lower-extremity rotational problems in children. Normal values to guide management. J Bone Joint Surg Am. 1985;67:39–47.
Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
3D CT for Determination of Femoral Anteversion
9. Dunlap K, Shands AR Jr, Hollister LC Jr, et al. A new method for determination of torsion of the femur. J Bone Joint Surg Am. 1953; 35:289–311. 10. Kay RM, Jaki KA, Skaggs DL. The effect of femoral rotation on the projected femoral neck-shaft angle. J Pediatr Orthop. 2000;20: 736–739. 11. Kingsley PC, Olmsted KL. A study to determine the angle of anteversion of the neck of the femur. J Bone Joint Surg Am. 1948; 30:745–751. 12. Magilligan DJ. Calculation of the angle of anteversion by means of horizontal lateral roentgenography. J Bone Joint Surg Am. 1956; 38:1231–1246. 13. Rogers SP. A method for determining the angle of torsion of the neck of the femur. J Bone Joint Surg. 1931;13:821–824. 14. Ryder CT, Crane L. Measuring femoral anteversion: the problem and a method. J Bone Joint Surg Am. 1953;35:321–328. 15. Shands AR Jr, Steele MK. Torsion of the femur. A follow-up report on the use of the Dunlap method for its determination. J Bone Joint Surg Am. 1958;40:803–816. 16. Hermann KL, Egund N. CT measurement of anteversion in the femoral neck. The influence of femur positioning. Acta Radiol. 1997;38:527–532. 17. Hernandez RJ, Tachdjian MO, Poznanski AK, et al. CT determination of femoral torsion. AJR Am J Roentgenol. 1981;137:91–101. 18. Hoiseth A, Reikeras O, Fonstelien E. Evaluation of three methods for measurement of femoral neck anteversion. Femoral neck anteversion, definition, measuring methods and errors. Acta Radiol. 1989;30:69–73. 19. Hoiseth A, Reikeras O, Fonstelien E. Basic concepts of femoral neck anteversion: comparison of two definitions. Br J Radiol. 1989;62: 114–116. 20. Mahboubi S, Horstmann H. Femoral torsion: CT measurement. Radiology. 1986;160:843–844. 21. Murphy SB, Simon SR, Kijewski PK, et al. Femoral anteversion. J Bone Joint Surg Am. 1987;69:1169–1176. 22. Reikeras O, Bjerkreim I. Idiopathic increased anteversion of the femoral neck. Radiological and clinical study in non-operated and operated patients. Acta Orthop Scand. 1982;53:839–845. 23. Sugano N, Noble PC, Kamaric E. A comparison of alternative methods of measuring femoral anteversion. J Comput Assist Tomogr. 1998;22:610–614. 24. Weiner DS, Cook AJ, Hoyt WA Jr, et al. Computed tomography in the measurement of femoral anteversion. Orthopedics. 1978;1:299–306. 25. Abel MF, Sutherland DH, Wenger DR, et al. Evaluation of CT scans and three-dimensional reformatted images for quantitative assessment of the hip. J Pediatr Orthop. 1994;14:48–53. 26. Lausten GS, Jorgensen F, Boesen J. Measurement of anteversion of the femoral neck. Ultrasound and computerized tomography compared. J Bone Joint Surg Br. 1989;71:237–239. 27. Miller F, Liang Y, Merlo M, et al. Measuring anteversion and femoral neck-shaft angle in cerebral palsy. Dev Med Child Neurol. 1997;39:113–118. 28. Miller F, Merlo M, Liang Y, et al. Femoral version and neckshaft angle. J Pediatr Orthop. 1993;13:382–388. 29. Bobroff ED, Chambers HG, Sartoris DJ, et al. Femoral anteversion and neck-shaft angle in children with cerebral palsy. Clin Orthop. 1999;364:194–204. 30. Abel MF, Wenger DR, Mubarak SJ, et al. Quantitative analysis of hip dysplasia in cerebral palsy: a study of radiographs and threedimensional reformatted images. J Pediatr Orthop. 1994;14:283–289. 31. Mubarak SJ, Valencia FG, Wenger DR. One-stage correction of the spastic dislocated hip. Use of pericapsular acetabuloplasty to improve coverage. J Bone Joint Surg Am. 1992;74:1347–1357. 32. Davids JR, Marshall AD, Blocker ER, et al. Femoral anteversion in children with cerebral palsy: assessment with two and threedimensional computed tomography scans. J Bone Joint Surg Am. 2003;85:481–488.
www.pedorthopaedics.com |
171
Three-dimensional Computed Tomography for Determination of Femoral Anteversion in a Cerebral Palsy Model Anthony I. Riccio, MD,* CDR Joseph Carney, MD, USN,w LCDR Nathan Hammel, MD, USN,w Mark Stanley, MD,w Jeffrey Cassidy, MD,z and Jon R. Davids, MDy
Background: Previous investigation has proven 3-dimensional (3D) computed tomography (CT) to be a poor method of assessing femoral anteversion in patients with cerebral palsy. However, new advancements in CT software yield the potential to improve upon those dated results. Methods: CT was performed on 9 femoral models with varying amounts of anteversion (20 to 60 degrees) and varying neck-shaft angles (120 to 160 degrees). Each model was scanned in 2 holding devices. One holder placed the femur in an ideal position relative to the gantry. The other placed the femur in flexion, adduction, and internal rotation simulating a common lower extremity posture in cerebral palsy. Femoral anteversion was measured on 3D reconstructions by 4 observers on 2 separate occasions. Interobserver and intraobserver reliability, accuracy, and the effect of increasing neck-shaft angle of the measurements were examined and compared with previously published data using the same models. Results: Pearson correlation coefficients between first and second measurements by the same examiner were all above 0.96 regardless of positioning of the femur in the gantry. The correlation coefficients among all examiners were 0.97 regardless of positioning of the femur in the gantry. Accuracy in measurements was comparable using 3D CT techniques with mean differences between the normal and cerebral palsy-positioned models of 10 degrees from the standard measurement. The Fisher exact test was used to compare the proportions placed into these 3 categories on the basis of the CT assessment. Again, an a of r0.05 was considered indicative of a significant difference. FIGURE 2. Computed tomography produced 3-dimensional shaded surface display of femur model.
tween the femoral neck and the femoral condyles was measured digitally with one line connecting the posterior condyles and the other line paralleling the mid portion of the neck (Fig. 3). This angle for each model was measured on an AGFA picture archiving system by 4 examiners on 2 separate occasions. The examiners consisted of 1 orthopaedic pediatric staff surgeon, 1 musculoskeletal radiology staff, and a resident from each program.
Statistical Methods The intraobserver and interobserver reliability of the 2D and 3D techniques for measurement of both the normally aligned and the cerebral palsy positioned models were assessed by calculating the Pearson correlation coefficients and the mean differences (and SDs) between measurements within and between examiners with comparison using t test analysis. The accuracy of the various CT measurement techniques under the various conditions was determined
RESULTS 3D CT Intraobserver Reliability The correlation coefficients between the first and second femoral anteversion measurements by the same examiner (intraobserver reliability) were all above 0.96 (excellent correlation) for the 3D scans regardless of the position of the femur in the scanner when using the newer generation 3D CT software technology. The corresponding femoral anteversion mean differences between first and second measurements were 2.4 degrees (SD = 2.1 degrees) for the normal positioned femurs and 2.0 degrees (SD = 2.4 degrees) for the cerebral palsy-positioned femurs (P = 0.321).
3D CT Interobserver Reliability The correlation coefficients among examiners measuring femoral anteversion were all above 0.97 (excellent correlation) for the 3D scans regardless of the position of the femur in the scanner when using the newer generation 3D CT software technology. The corresponding femoral anteversion mean differences among examiners were 3.3 degrees (SD = 1.9 degrees) for the normal positioned femurs and 3.2 degrees (SD = 1.4 degrees) for the cerebral palsy-positioned femurs (P = 0.886). Interobserver reliability for the 2D CT technique was described in the senior author’s previous work.32
Accuracy
FIGURE 3. Measurement of femoral anteversion on 3-dimensional computed tomography image by determining angle between the femoral neck and the femoral condyles. Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
Femoral anteversion measurement, as evaluated on a continuous scale, of the optimally and suboptimally positioned femurs was accurate when using the newer generation 3D CT software. The absolute femoral anteversion mean difference was 3.6 degrees (SD = 3.3 degrees) between the direct measurements of femoral anteversion and the optimally positioned femurs measured with the 3D CT technique, and 3.0 degrees (SD = 3.1 degrees) between the direct measurements of femoral anteversion and the suboptimally positioned femurs measured with the 3D CT technique (P = 0.228). As evaluated on a clinical categorical scale, the accuracy of the 3D CT for determining femoral anteversion in optimal alignment compared with the suboptimal alignwww.pedorthopaedics.com |
169
J Pediatr Orthop
Riccio et al
FIGURE 4. Accuracy of 3-dimensional computed tomography with postimaging processing for determining femoral anteversion in normal alignment compared with typical cerebral palsy alignment. Values are number of measurements falling within the clinical accuracy categories. No significant difference was found between measurement categories when comparing the 2 positions. (P = 0.907).
ment was comparable with no significant difference found between measurement categories (P = 0.907) (Fig. 4). Cerebral palsy alignment significantly compromised the accuracy of the 2D technique, with only one 2D measurement falling within 5 degrees of the standard measurements. When evaluating the accuracy of 2D CT femoral anteversion measurement compared with the 3D measurement technique, the 3D technique was found to be significantly more accurate using the clinical categorical scale in measuring the typical cerebral palsy positioned femurs (P < 0.0001) (Fig. 5).
DISCUSSION Techniques for accurately assessing femoral anteversion in children with cerebral palsy affected hips have
FIGURE 5. Accuracy of 2-dimensional computed tomography versus 3-dimensional computed tomography for determining femoral anteversion in typical cerebral palsy alignment. Values are number of measurements falling within the clinical accuracy categories. Three-dimensional computed tomography with postimaging processing was found to be significantly more accurate when comparing clinical accuracy measurement categories between the 2 techniques (P < 0.0001).
170 | www.pedorthopaedics.com
Volume 35, Number 2, March 2015
not been found to be consistently accurate to date. CT has long been considered the best method to determine anteversion in children with cerebral palsy, yet limitations with this technique exist. In a previous publication by the senior author it was established that cerebral palsy patients with the typical flexed, adducted, and internally rotated posture of the hip present challenges in accurately determining femoral anteversion angles due to suboptimal positioning in the scanner that cannot be remedied with early-generation 3D CT systems.32 Recently, newer reconstruction software systems have become available for CT that provide the radiologist and clinician with the ability to subtract and manipulate images in a potentially more accurate manner with 3D output. Using the newly available reconstruction software for modern CT, we demonstrated near-perfect interobserver and intraobserver reliability with an accuracy throughout femoral architecture and femur positioning within 1 SD of the actual measurement of the femoral anteversion. Further, there was a statistical accuracy advantage of the 3D measurements over the historical 2D modeling when the femur was held in an abnormal position relative to the gantry replicating a common set of contractures in cerebral palsy. These findings represent an advancement in evaluating femoral anteversion in cerebral palsy patients that has not been previously described. In this study, intraobserver and interobserver reliability was found to be excellent for the 3D CT technique when assessing femoral anteversion regardless of the position of the femurs in the scanner, femoral anteversion angle, or the neck-shaft angle. Furthermore, measurement of femoral anteversion using the 3D technique in this study was accurate regardless of positioning of the femurs, severity of femoral anteversion, or abnormality of the neck-shaft angle of the femurs when evaluated both on a continuous scale and when evaluated with a clinical categorical scale. When evaluating accuracy using the clinical categorical scale, the 3D CT technique was accurate in determining femoral anteversion angles regardless of patient positioning (Fig. 4). Furthermore, the 3D CT technique was significantly more accurate in determining femoral anteversion angles in the cerebral palsypositioned femurs than the 2D CT technique (Fig. 5). As radiation exposure to pediatric patients is always a concern, it should be noted that the generation of 3D imaging does not impart any increased radiation dose upon the patient in comparison with standard 2D imaging. At our institution, all CT studies are obtained using volumetric scanning. Every extremity examination is therefore performed using a 0.6 mm spiral acquisition. The data obtained may then be reconstructed in any manner the radiologist chooses. As image processing occurs following standard data acquisition, the radiation dose to the patient is equivalent regardless of whether only 2D images are obtained or the data are formatted into axial, sagittal, and coronal images with 3D reconstructions. Furthermore, as the generation of 3D images is performed by data manipulation, obtaining these images at our institution is at no increased cost to the patient or the institution. Understandably, this may vary Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 35, Number 2, March 2015
from institution to institution based upon whether those facilities bill for the increased time it takes their radiation technologists to format 3D reconstructions. The authors do acknowledge certain limitations in this study. Models used in this research endeavor were cast from adult femurs. The casting may have provided for better-developed anatomic landmarks than pediatric femurs and therefore, when evaluating the cerebral palsy patient femur anatomic landmarks may be more challenging to decipher than our models creating potentially less accuracy and reliability in the method than we found. However, it can be argued that no other currently well-accepted diagnostic evaluation technique can provide better visualization of the 3D contour of the femur bone than 3D CT imaging. Another potential limitation is that image manipulation requires specific software, which can be a limitation for clinical applicability in certain treatment centers. However, the software used in this study is widely available and expected to grow in use rather than decrease in use as health care systems evolve. We conclude that despite the inability to position a child optimally in a CT scanner, a 3D reconstruction with postimaging processing to align the femur along its axis for measurement of anteversion is superior in utilizing sequential 2D reconstructions. The technique is highly accurate and possesses near-perfect reliability. We therefore recommend 3D reconstructions with appropriate postimaging processing when evaluating femoral anteversion angles in children with contractures who cannot be positioned acceptably in the CT scanner. REFERENCES 1. Aktas S, Aiona M, Orendurff M. Evaluation of rotational gait abnormality in patients with cerebral palsy. J Pediatr Orthop. 2000;20:217–220. 2. Gage JR, DeLuca PA, Renshaw TS. Gait analysis: principle and applications with emphasis on its use in cerebral palsy. Instr Course Lect. 1996;45:491–507. 3. Ruwe PA, Gage JR, Ozonoff MB, et al. Clinical determination of femoral anteversion. A comparison with established techniques. J Bone Joint Surg Am. 1992;74:820–830. 4. Fabry G, MacEwen GD, Shands AR Jr. Torsion of the femur. A follow-up study in normal and abnormal conditions. J Bone Joint Surg Am. 1973;55:1726–1738. 5. Beals RK. Developmental changes in the femur and acetabulum in spastic paraplegia and diplegia. Dev Med Child Neurol. 1969;11: 303–313. 6. Staheli LT, Duncan WR, Schaefer E. Growth alternations in the hemiplegic child. A study of femoral anteversion, neck-shaft angle, hip rotation, C.E. angle, limb length and circumference in 50 hemiplegic children. Clin Orthop. 1968;60:205–212. 7. Gelberman RH, Cohen MS, Desai SS, et al. Femoral anteversion. A clinical assessment of idiopathic intoeing gait in children. J Bone Joint Surg Br. 1987;69:75–79. 8. Staheli LT, Corbett M, Wyss C, et al. Lower-extremity rotational problems in children. Normal values to guide management. J Bone Joint Surg Am. 1985;67:39–47.
Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
3D CT for Determination of Femoral Anteversion
9. Dunlap K, Shands AR Jr, Hollister LC Jr, et al. A new method for determination of torsion of the femur. J Bone Joint Surg Am. 1953; 35:289–311. 10. Kay RM, Jaki KA, Skaggs DL. The effect of femoral rotation on the projected femoral neck-shaft angle. J Pediatr Orthop. 2000;20: 736–739. 11. Kingsley PC, Olmsted KL. A study to determine the angle of anteversion of the neck of the femur. J Bone Joint Surg Am. 1948; 30:745–751. 12. Magilligan DJ. Calculation of the angle of anteversion by means of horizontal lateral roentgenography. J Bone Joint Surg Am. 1956; 38:1231–1246. 13. Rogers SP. A method for determining the angle of torsion of the neck of the femur. J Bone Joint Surg. 1931;13:821–824. 14. Ryder CT, Crane L. Measuring femoral anteversion: the problem and a method. J Bone Joint Surg Am. 1953;35:321–328. 15. Shands AR Jr, Steele MK. Torsion of the femur. A follow-up report on the use of the Dunlap method for its determination. J Bone Joint Surg Am. 1958;40:803–816. 16. Hermann KL, Egund N. CT measurement of anteversion in the femoral neck. The influence of femur positioning. Acta Radiol. 1997;38:527–532. 17. Hernandez RJ, Tachdjian MO, Poznanski AK, et al. CT determination of femoral torsion. AJR Am J Roentgenol. 1981;137:91–101. 18. Hoiseth A, Reikeras O, Fonstelien E. Evaluation of three methods for measurement of femoral neck anteversion. Femoral neck anteversion, definition, measuring methods and errors. Acta Radiol. 1989;30:69–73. 19. Hoiseth A, Reikeras O, Fonstelien E. Basic concepts of femoral neck anteversion: comparison of two definitions. Br J Radiol. 1989;62: 114–116. 20. Mahboubi S, Horstmann H. Femoral torsion: CT measurement. Radiology. 1986;160:843–844. 21. Murphy SB, Simon SR, Kijewski PK, et al. Femoral anteversion. J Bone Joint Surg Am. 1987;69:1169–1176. 22. Reikeras O, Bjerkreim I. Idiopathic increased anteversion of the femoral neck. Radiological and clinical study in non-operated and operated patients. Acta Orthop Scand. 1982;53:839–845. 23. Sugano N, Noble PC, Kamaric E. A comparison of alternative methods of measuring femoral anteversion. J Comput Assist Tomogr. 1998;22:610–614. 24. Weiner DS, Cook AJ, Hoyt WA Jr, et al. Computed tomography in the measurement of femoral anteversion. Orthopedics. 1978;1:299–306. 25. Abel MF, Sutherland DH, Wenger DR, et al. Evaluation of CT scans and three-dimensional reformatted images for quantitative assessment of the hip. J Pediatr Orthop. 1994;14:48–53. 26. Lausten GS, Jorgensen F, Boesen J. Measurement of anteversion of the femoral neck. Ultrasound and computerized tomography compared. J Bone Joint Surg Br. 1989;71:237–239. 27. Miller F, Liang Y, Merlo M, et al. Measuring anteversion and femoral neck-shaft angle in cerebral palsy. Dev Med Child Neurol. 1997;39:113–118. 28. Miller F, Merlo M, Liang Y, et al. Femoral version and neckshaft angle. J Pediatr Orthop. 1993;13:382–388. 29. Bobroff ED, Chambers HG, Sartoris DJ, et al. Femoral anteversion and neck-shaft angle in children with cerebral palsy. Clin Orthop. 1999;364:194–204. 30. Abel MF, Wenger DR, Mubarak SJ, et al. Quantitative analysis of hip dysplasia in cerebral palsy: a study of radiographs and threedimensional reformatted images. J Pediatr Orthop. 1994;14:283–289. 31. Mubarak SJ, Valencia FG, Wenger DR. One-stage correction of the spastic dislocated hip. Use of pericapsular acetabuloplasty to improve coverage. J Bone Joint Surg Am. 1992;74:1347–1357. 32. Davids JR, Marshall AD, Blocker ER, et al. Femoral anteversion in children with cerebral palsy: assessment with two and threedimensional computed tomography scans. J Bone Joint Surg Am. 2003;85:481–488.
www.pedorthopaedics.com |
171
