- Email: [email protected]
Radiographic Angles in Hallux Valgus: Comparison between Manual and Computer-Assisted Measurements
The Journal of Foot & Ankle Surgery 49 (2010) 523–528
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Radiographic Angles in Hallux Valgus: Comparison between Manual and Computer-Assisted Measurements Subodh Srivastava, FRCS (Orth & trauma) 1, Nachiappan Chockalingam, PhD 2, Tarek El Fakhri, FRCS 3 1 Orthopaedic Surgeon and Visiting Fellow, Faculty of Health, Staffordshire University, Stoke on Trent, UK; Orthopaedic Surgeon and Visiting Fellow, Orthopaedics & trauma, Mid Staffordshire NHS Foundation Trust, Stafford, UK 2 Professor of Clinical Biomechanics, Faculty of Health, Staffordshire University, Stoke on Trent, UK 3 Consultant Orthopaedic Surgeon, Orthopaedics & trauma, Mid Staffordshire NHS Foundation Trust, Stafford, UK
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 5 Keywords: radiographic angles hallux valgus manual and computer-assisted measurement technical error of measurement
Radiographic angles are used to assess the severity of hallux valgus deformity, in preoperative planning, assessing postoperative outcomes, and in comparing results between interventions. The manual method to measure these angles has been shown to be prone to errors and to be time consuming. Computer programs are now available to assist in angular measurements. This study was undertaken to compare the reliability and time taken between the 2 methods. A total of 30 radiographs were used from a population of patients with hallux valgus deformity. The radiographs were digitized for computer-assisted measurements. The technical error of measurement (TEM) was calculated for intra- and interobserver data to assess the error in angular measurement with both methods. The technical error of measurement was lower with the computer-assisted method, suggesting that this method is more reliable. Furthermore, the time taken was also reduced with this method.) Ó 2010 by the American College of Foot and Ankle Surgeons. All rights reserved.
Radiographic angles are used to assess the severity of hallux valgus deformity, and in selecting type of surgical procedure for correction, assessing postoperative outcomes, and comparing results with other studies. The radiographic angles commonly measured are hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), and interphalangeal angle (IPA). The manual method to measure these angles on weight-bearing radiographs involves identifying anatomical landmarks, using marker pens, and measuring angles with a goniometer. This method is prone to errors, and can be time consuming and arduous, especially measurements done after surgery (1–5). These errors can be reduced by using standardized technique for performing weight-bearing anteroposterior radiographs and by defining reference points for first metatarsal axis and other anatomical landmarks (6). Digital workstations are now being widely used to view and store digitized images of radiographs. Computer software is available to aid in the measurement of radiographic angles. Angular measurements of digitized images using computer software has been reported by various authors for Cobb angle in spine x-rays (7, 8), and for angles in hallux valgus (9–11). Financial Disclosure: None reported. Conflict of Interest: None reported. Address correspondence to: Subodh Srivastava, FRCS (Orth & Trauma), Faculty of Health, Staffordshire University, West view, Newcastle Road, Loggerheads, Shropshire TF9 4PH, UK. E-mail address: [email protected] (S. Srivastava).
In this study, we used specifically designed software for computerassisted measurements of 4 radiographic angles on anteroposterior radiographs of the foot. We hypothesize that this would remove intrinsic errors seen with the manual method, improve reliability, decrease the time spent to obtain measurements, and be user friendly. Objectives The main objective of this study was to compare the inter- and intraobserver reliability between manual measurements using marker pen and goniometer, and computer-assisted measurements of digitized images using software, for radiographic angles in hallux valgus (HVA, IMA, DMAA, and IPA). The secondary objective was to compare the time taken between these 2 methods. Methods Study design This observational study was conducted at Stafford General Hospitals NHS Trust, after approval from the local research and ethics committee (LREC). Selection of radiographs Thirty radiographs performed preoperatively for patients with hallux valgus deformity seen in an outpatient clinic in January 2007 were used in this study. The radiographs had been taken using standard technique with the patients weight bearing, 15-degree angulation of the x-ray tube toward the ankle, and centered on the midfoot.
1067-2516/$ - see front matter Ó 2010 by the American College of Foot and Ankle Surgeons. All rights reserved. doi:10.1053/j.jfas.2010.07.012
524
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
All identifying information of patients was removed and copies of radiographs used had no further patient data. Digitized images of radiographs The radiographs were digitized using a digital camera and the images were stored electronically. The distance between camera and radiographs, lighting, and zoom were kept the same for all images. Angles measured The following 4 angles were measured: HVA: The angle between the longitudinal axes of the first metatarsal and proximal phalanx of the first toe. IMA: The angle between the longitudinal axes of the first and second metatarsals. DMAA: The angle between the longitudinal axis of the first metatarsal and a line through the distal articular surface of the first metatarsal. IPA: The angle between the longitudinal axes of the proximal and distal phalanx of the first toe.
Observers The radiographs and digitized images were assessed by 3 observers: 1 orthopedic surgeon with special interest in foot and ankle 1 orthopedic surgeon (general) 1 trainee in orthopedics and trauma We felt that computer-assisted measurements with the specifically designed software would be reliable with skilled and experienced observers, as well as observers with little or no experience in performing angular measurements in hallux valgus, and hence we used observers with different levels of experience. The study was planned to include 4 observers; however, one of the observers (junior trainee) left the hospital for further training, and could not complete the observations. The measurements carried out by this observer were excluded from the study. Group A: Manual measurements Manual measurements were completed using marker pen and goniometer. Reference points were made in the first metatarsal, second metatarsal, proximal phalanx, and distal phalanx of the first toe and distal articular surface of the first metatarsal, using guidelines published by the ad hoc committee of the American Orthopaedic Foot and Ankle Society (AOFAS) on angular measurements (12). The axes were then drawn in the respective bones and angles measured using a goniometer (Table 1 and Fig. 1). All the observers were given a sheet outlining the guidelines and a demonstration was provided on performing the angular measurements, with special emphasis on the placement of reference points. The observers were also given an opportunity to take readings on a few radiographs and seek any clarification regarding the manual method of angular measurement (Fig. 2).
The software then automatically computes the various axes and measures the 4 angles (HVA, IMA, DMAA, and IPA). The software was demonstrated and all the observers had an opportunity to use this technique on the computer a few times before the measurements were recorded (Fig. 3). Collection of data The 3 observers reviewed the radiographs and digitized images 3 separate times at 1-week intervals. The order of the images was changed on each reading and the measurements were done alternating between methods as follows: Week Week Week Week Week Week
1: 2: 3: 4: 5: 6:
manual measurement computer-assisted measurement manual measurement computer-assisted measurement manual measurement computer-assisted measurement
None of the observers had access to their previous measurements or measurements of the other observers. All the measurements were recorded on Excel sheets electronically. A total of 1080 measurements were recorded in each group (30 images 4 angles 3 observers 3 readings). The data were analyzed after the 3 observers completed all the measurements using both methods. The time taken to complete the measurements by both methods was recorded for all 3 observers. Analysis of data The means and standard deviations of the 3 readings of the 4 angles, done by each examiner for all 30 images by both methods, were calculated. The intra- and interobserver errors of measurement were calculated using technical error of measurement (TEM), a standard method reported in the literature (13, 14). The TEM was estimated using the following formula: ffi vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 3 u u PK u MðnÞ 7 1 uPN 6 6 PK 7 u MðnÞ2 7 u 16 K 4 1 5 u u t NðK 1Þ where N is the number of subjects (in this study, number of radiographs), M(n) is the nth replicate of measurement, and K is the number of determinations. This formula provides an estimate of measurement error in the units of measurement of the variable (in this study in degrees). The measurement error is less if the TEM with a measurement technique is low, indicating greater reliability. The reliability coefficient (R), which is not estimated in degrees, is estimated using the following formula: R ¼ 1 – ([TEM ]2/[SD ]2). This coefficient (R) ranges on a scale from 0 to 1, and gives an estimation of error in the inter- and intraobserver measurement variance. If the R is 0.8, then the data are 80% error free. Time taken to perform the measurements by the 2 methods was noted. The mean time taken to measure the 4 angles on each image was calculated and comparison done between the 2 methods.
Results
Group B: Computer-assisted measurements
Intraobserver data The computer-assisted measurements were performed using a computer and special software developed locally (MATLAB; The Math Works Inc., Natick, MA). The reference points were placed with a mouse by the observers, using the following guide: - metaphyseal-diaphyseal junction proximally and distally in the first metatarsal, second metatarsal, and proximal and distal phalanx of the first toe - the medial and lateral limits of the distal articular surface of the first metatarsal
The intraobserver error was assessed by calculating the TEM for the 3 observers (Table 2). The intraobserver error was less with the computer-assisted method for all 4 angles, including the DMAA. The TEM (observer 1) improved from 2.32 to 2.24 for HVA, 1.9 to 1.33 for IMA, 3.9 to 2.97 for DMAA, and 2.03 to 1.84 for IPA. Furthermore, the
Table 1 American Orthopaedic Foot and Ankle Society criteria for reference points The reference point should be placed as close as possible to the diaphysis. The midpoint on the transverse line joining the reference points proximally and distally is taken and joined to give the longitudinal axis. First metatarsal reference points The reference points should be located in the metaphyseal/ diaphyseal region 1–2 cm proximal to the distal articular surface and 1–2 cm distal to the proximal articular surface. The 1-cm range allows for various sized feet. Second metatarsal reference points The reference points should be located in the metaphyseal/ diaphyseal region 1–2 cm proximal to the distal articular surface and 1–2 cm distal to the proximal articular surface. First toe, proximal phalanx The proximal phalanx is substantially shorter, which leaves more room for errors in angular measurement. They recommended metaphyseal/ reference points diaphyseal reference points 0.5 to 1.0 cm proximal or distal to the articular surfaces. Similar points can be placed on the distal phalanx of first toe.
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
525
Fig. 1. The location of reference points for the first metatarsal. Fig. 2. A sample radiograph with manual measurements.
error was reduced for the other 2 observers, including observer 3 who had the least experience and skill level in performing angular measurements for hallux valgus. The reliability coefficient (R) was calculated using the TEM for all 3 observers (Table 3). The R was higher than 0.97 for all 3 observers, suggesting that more than 97% of measurements were error free. Interobserver data The mean of the 3 measurements by each observer were taken to calculate the TEM by the 2 methods (Table 4). The TEM was reduced with computer-assisted measurements for all 4 angles. The error in measurement was highest for DMAA by both methods, reflecting the problems encountered in measuring this angle. The lowest error was for the IMA by both methods (TEM of 1.37 and 1.19 for IMA versus 2.17 and 3.38 for DMAA by manual and computer-assisted methods respectively). The reliability coefficient was calculated using the TEM for the 2 methods (Table 5). The R was consistently higher than 0.98 with both methods, suggesting that more than 98% of measurements were error free. Time taken for measurements with both methods The time taken to measure the 4 angles (HVA, IMA, DMAA, and IPA) on each image by the 3 observers using both methods was
recorded on all 3 sets of readings. The mean time taken was calculated and is presented in Table 6. The time taken was greater with the manual method for all 3 observers. Among the 3 observers, observer 1 (most skilled) took the least time and observer 3 (least skilled) took the most time to complete measurements on each image. With repeated measurements, the time taken was reduced and on the third set of manual measurement, all 3 observers recorded less time. The computer-assisted method greatly reduced the time taken to perform angular measurements, with less time taken for the third set, as observers became familiar with the software used. The time taken to do measurements was almost similar for all 3 examiners in the third set irrespective of the level of skill and experience. Discussion Radiographic angles are measured to assess severity of deformity, choose type of surgical procedure, assess postoperative correction, and compare results. The use of angular measurements is based on the belief that they are reliable, repeatable, and provide a constant value for comparison with other studies. The traditional method of measuring angles on plain radiographs is by using marker pens, placing reference points, identifying axis of the respective bones, and measuring angles with a protractor or goniometer.
526
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
Table 3 The R value for the 3 observers, intraobserver data Intraobserver data R value (reliability coefficient) Angle
HVA IMA DMAA IPA
Observer 1
Observer 2
Observer 3
Manual
Computer
Manual
Computer
Manual
Computer
0.98 0.99 0.96 0.98
0.99 0.99 0.97 0.96
0.98 0.99 0.98 0.99
0.99 0.99 0.98 0.99
0.99 0.98 0.96 0.98
0.99 0.98 0.97 0.99
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle.
Fig. 3. A sample digitized image with computer-assisted measurements.
The manual method, however, is prone to errors and various studies have evaluated intraobserver and interobserver measurement error. The DMAA is particularly prone to measurement error, and is related to difficulty in identifying the limits of the articular surface (15, 16). More recently, Robinson et al (17) observed that the DMAA varies significantly in a linear pattern with axial rotation of the first metatarsal, suggesting the inaccuracy of extrapolating the DMAA from plain anteroposterior radiographs. The errors can be reduced by standardizing the technique of weight-bearing radiographs (18) and having specific guidance for placement of reference points (6). The AOFAS guideline for placement of reference points at the metaphyseal-diaphyseal junction of first metatarsal, second metatarsal, and proximal phalanx are widely used (12). Shima et al (19) evaluated radiographs before and after Table 2 Intraobserver error (TEM) in angular measurements: manual versus computer-assisted method Intraobserver error (TEM) Angle
HVA IMA DMAA IPA
Observer 1
Observer 2
a proximal crescentic osteotomy performed for the treatment of hallux valgus. A line connecting the centers of the first metatarsal head and the proximal articular surface of the first metatarsal to define its longitudinal axis gave the best intraobserver and interobserver reliability for the measurement of the hallux valgus and intermetatarsal angles. However, there are sources of intrinsic error with the manual method, such as the use of variable-width marker pens, inaccuracy of protractors, error in approximating the angle, and difficulty in redrawing lines in the event of a mistake in placement of the reference points. The manual method can be time consuming and arduous as well. Although digital radiography is now available in more centers and is replacing conventional radiography, the computer workstation is used to store, view, and retrieve images among other routine work in clinics. In this context, customized computer software creates the opportunity for quick, easy, and reliable measurements. Various authors have explored the use of digital imaging in orthopedic settings. Early in the implementation of digital imaging, Ackerman et al (20) compared digital with analog reading for fracture detection and found that sensitivity and specificity were better with analog films. Observers noted that workstations were cumbersome and slow, and there was degradation in image quality. However, computers and digital imaging technology have improved, and digital radiography is now accepted and is rapidly replacing standard radiography. Hamers et al (21) reported their institution’s clinical experience with digital radiography and found that 3 of the 6 radiologists preferred the digital system and 3 had no preference. Grainger et al (22) evaluated a digital semiautomated system for the radiological assessment of distal radial fractures. They found improved intra- and interobserver agreement in measuring parameters such as radial angle, length, and dorsal shift. Angular measurements of digitized images using computer software have been reported by various authors for Cobb angle in spine x-rays. Shea et al (7) did a study that compared manual with computer-assisted measurement of Cobb angle to assess deformity in scoliosis patients. The intraobserver variability was 3.3 degrees for the manual set, and 2.6 degrees for the digitized images. The study concluded that
Table 4 Interobserver error (TEM) in angular measurements: manual versus computer-assisted method Interobserver error (TEM)
Observer3
Manual
Computer
Manual
Computer
Manual
Computer
Angle
Manual
Computer
2.32 1.9 3.9 2.03
2.24 1.33 2.97 1.84
2.64 2.27 3.04 2.52
1.58 1.33 2.76 1.61
2.52 2.51 4.07 2.98
1.68 1.6 3.68 2.18
HVA IMA DMAA IPA
2.49 1.37 3.38 2.23
1.59 1.19 2.17 1.98
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle; TEM, technical error of measurement.
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle; TEM, technical error of measurement.
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
Table 5 R value (reliability coefficient) for interobserver data Interobserver data R value Angle
Manual
Computer
HVA IMA DMAA IPA
0.97 0.98 0.96 0.99
0.99 0.98 0.98 0.99
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle.
using a computer might reduce intrinsic measurement errors with the manual technique using marker pens and protractors. Chockalingam et al (8) devised a study to develop a computerized method for measuring and quantifying the magnitude of spinal curvature. A computer program was developed to assess the spinal deformity and measure the Cobb angle on digitally scanned images. The reliability was assessed using TEM and R. The mean inter- and intraobserver errors in measurement were considerably lower with computer-assisted measurements. Furthermore, the results were similar for all the observers, suggesting that accurate and reliable measurements were possible, even if the assessor is not highly skilled or experienced. Angular measurements of digitized images using computer software have been reported by various authors for angles in hallux valgus (9–11). None of these studies have evaluated the inter- and intraobserver reliability for all 4 angles and compared time taken between the 2 methods. Our hypothesis was that with use of computer software specifically designed for angular measurements in hallux valgus, measurement error would be reduced. Furthermore, the technique would be quick and easy to use, and be reliable in the hands of inexperienced observers as well. Intra- and interobserver error and time taken for measurement In this study, the TEM was measured to assess the error in measurement of radiographic angles. The intraobserver error and interobserver error were less with the computer-assisted method for all 4 angles, including the DMAA. Furthermore, the error was reduced for all 3 observers, including observer 3 who had the least experience and skill level in performing angular measurements for hallux valgus (Tables 1 and 3). None of the previous studies have assessed the ease of use and compared the time taken between the 2 methods. In this study, the time taken to perform angular measurements by the 2 methods was compared (Table 5). The computer-assisted method was found to be quick and easy to use by all 3 observers, and in the third set of measurements, all observers had recorded almost similar times. Comparison with previous studies Panchbhavi and Trevino (9) did a study to compare inter- and intraobserver reliability in measuring 3 angles (HVA, IMA, and DMAA) by manual and computer-assisted methods. No difference was noted between the 2 methods. This was attributed to the small number of Table 6 Mean time taken for angular measurements Mean time taken for angular measurements on an image (minutes) Observer
1 2 3
Manual
527
radiographs and fewer angles measured (20 radiographs and 3 angles versus 30 radiographs and 4 angles in this study). Panchbhavi and Trevino (9) also commented that the software used was probably not user friendly and observers were not used to working with digital images resulting in a long learning curve. Over the years, computer workstations have become more widely available and health professionals use digital images much more commonly. Furthermore, the software used in this study was specially designed to measure angles in the foot. Farber et al (10) looked at the reliability in measuring HVA and IMA and compared the 2 methods. The computerized method gave better overall reliability with interobserver agreement (measurement within 2 degrees), improving from 66% with plain films to 80% with digital workstation. The IMA was similarly more reliable with the computer-assisted method. Their findings were similar to the observations in the present study; the only difference being that all 3 observers in the study were highly experienced foot and ankle surgeons who were used to performing manual measurements routinely. In the present study, the observers had different levels of experience, and the reliability improved with the computer-assisted method for the least-skilled observer as well. Furthermore, the study did not look at the DMAA and IPA and did not compare the time taken between the 2 methods. Piqué-Vidal et al (11) looked at all 4 angles but did not evaluate the interobserver reliability. Manual measurements were made by an orthopedic surgeon, and angular measurements of digitized images were performed by an independent technician, trained to use the computer software (Autocad 2000, Autodesk Inc., San Rafael, CA). A total of 176 weight-bearing radiographs were used. The intraobserver reliability was evaluated and better results were noted with the computer-assisted method. The software used in the present study was designed specifically to measure the radiographic angles in hallux valgus. The computer program was developed using MATLAB. The technique involves placement of relevant reference points on the digital image using the mouse by the observer. All the other steps (joining the reference points, identifying the longitudinal axis, and measuring the angles) are performed by the software. This eliminates the intrinsic errors associated with manual methods such as use of variable-width marker pens, inaccurate protractors, and errors in estimating angles with varying protractors. This is reflected in the reduced error (both intra- and interobserver error) with the computer-assisted method in this study for all 4 angles, irrespective of the skill level of the observer. Furthermore, the software is easy to use, with a small learning curve, resulting in reduced time taken to complete angular measurements and almost similar findings for observers with varying experience by the third reading. This would be relevant in the clinical setting, in providing clinicians the opportunity to measure the angles quickly in outpatients where time constraints are often present. In conclusion, many different angles and other critera, such as sesamoid position, are used to assess hallux valgus deformity, of which the most commonly used angles are HVA, IMA, DMAA, and IPA. The manual method using specific guidelines such as those outlined by AOFAS and computer-assisted methods using available software are currently accepted as standard techniques. This project was undertaken as a pilot study to assess the role of computer-assisted measurements in patients with hallux valgus deformity. Specially designed software was used to measure 4 angles in 30 radiographs. The results suggest the following:
Computer
1st set
2nd set
3rd set
1st set
2nd set
3rd set
1.8 2.2 3.0
1.5 2.0 2.8
1.4 1.8 2.5
0.5 0.8 1.0
0.4 0.6 0.8
0.4 0.5 0.6
The measurement error can be reduced with the computerassisted method The measurement error is reduced irrespective of experience and skill level with the computer-assisted method
528
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
The time taken with the computer-assisted method is less Overall, the computer-assisted method was found to be more reliable and user friendly A limitation of this study was that a small number of radiographs were used and the digitized images were taken using a digital camera. The same camera was used and all parameters such as lighting and zoom were kept constant, but some variability in images is possible. Further studies need to be undertaken with larger numbers of radiographs to firmly establish the benefit of computer-assisted methods. Furthermore, special software that can assess all possible radiographic parameters in hallux valgus would be vastly helpful to the clinician. Although a comparison of different types of software currently available to perform angular measurements would be interesting, a study to establish correlation between improvement in radiographic angles in hallux valgus and improvement in symptoms of patients would be very useful for the clinician. Acknowledgment The authors acknowledge the technical assistance provided by Dr Chi-Wen Lung. References 1. Saltzman C, Brandser E, Berbaum K, DeGnore L, Holmes J, Katcherian D, Teadsall R, Alexander I. Reliability of standard foot radiographic measurements. Foot Ankle 15:661–665, 1994. 2. Resch S, Ryd L, Stenstorm A, Johnson K, Raynisson K. Measuring hallux valgus: a comparision of conventional radiography and clinical parameters with regard to measurement accuracy. Foot Ankle 16:267–270, 1995. 3. Schneider W, Knahr K. Metatarsophalangeal and intermetetarsal angle: different values and interpretation of postoperative results dependent on the technique of measurement. Foot Ankle 19:532–536, 1998. 4. Coughlin MJ, Freund E. The reliability of angular measurements in hallux valgus deformities. Foot Ankle 22:369–379, 2001. 5. Condon F, Kaliszer M, Conhyea D, O'Donnell T, Shaju A, Masterson E. The first metatarsal angle in hallux valgus: an analysis of measurement reliability and the error involved. Foot Ankle 22:717–721, 2002.
6. Schneider W, Csepan R, Kasparek M, Pinggera O, Knahr K. Intra and interobserver repeatability of radiographic measurements in hallux surgery. Acta Orthop Scand 6:670–673, 2002. 7. Shea KG, Stevens PM, Nelson M, Smith JT, Masters KS, Yandow S. A comparision of manual versus computer-assisted radiographic measurement. Intraobserver measurement variability for Cobb angles. Spine 23:551–555, 1998. 8. Chockalingam N, Dangerfield PH, Giakas G, Cochrane T, Dorgan JC. Computer assisted Cobb measurement of scoliosis. Eur Spine J 11:353–357, 2002. 9. Panchbhavi VK, Trevino S. Comparision between manual and computer assisted measurements of hallux valgus parameters. Foot Ankle 25:709–711, 2004. 10. Farber DC, DeOrio JK, Steel MW. Goniometric versus computerised angle measurement in assessing hallux valgus. Foot Ankle 26:234–238, 2005. 11. Piqué-Vidal C, Maled-Garcia I, Arabi-Moreno J, B-Stat JV. Radiographic angles in hallux valgus: differences between measurements made manually and with a computerised program. Foot Ankle 27:175–180, 2006. 12. Coughlin MJ, Saltzman CL, Nunley JA. Angular measurements in the evaluation of halluxvalgus deformities: A report of the Ad Hoc committee of the American Orthopaedic Foot and Ankle Society on angular measurements. Foot Ankle 23:68– 74, 2002. 13. Mueller WH, Martorell R. Reliability and accuracy of measurement. In Anthropometric Standardisation Reference Manual, pp 83–86, edited by TG Lohman, AF Roache, R Martorell, editors, Human Kinetics Books, Champaign, IL, 1988. 14. Ulijaszek S, Lourie J. Intra and inter observer error in measurement. In Anthropometry: The Individual and the Population, pp 30–55, edited by S Ulijasezek, Cambridge University Press, , 1994. 15. Vittetoe D, Saltzman C, Krieg J, Brown T. Reliability and validity of distal metatarsal articular angle. Foot Ankle 15:541–547, 1994. 16. Chi TD, Davitt J, Younger A, Holt S, Sangeorzan BJ. Intra- and Inter-observer reliability of the distal metatarsal articular angle in hallux valgus. Foot Ankle 22:722–726, 2002. 17. Robinson AH, Cullen NP, Chhaya NC, Sri-Ram K, Lynch A. Variation of the distal metatarsal articular angle with axial rotation and inclination of the first metatarsal. Foot Ankle Int 27(12):1036–1040, 2006. 18. Smith RW, Reynolds JC, Stewart MJ. Hallux valgus assessment: report of research committee of American Orthopaedic Foot and Ankle Society. Foot Ankle 5:92–103, 1984. 19. Shima H, Okuda R, Yasuda T, Jotoku T, Kitano N, Kinoshita M. Radiographic measurements in patients with hallux valgus before and after proximal crescentic osteotomy. J Bone Joint Surg Am A91(6):1369–1376, 2009. 20. Ackerman SJ, Gitlin JN, Gayler RW, Flagle CD, Bryan RN. Reciever operating characteristic analysis of fracture and pneumonia detection: comparision of laserdigitised workstation images and conventional analog radiographs. Radiology 186:263–268, 1993. 21. Hamers S, Freyschmidt J, Neitzel U. Digital radiography with a large-scale electronic flat-panel dtector vs screen film radiography: observer preference in clinical skeletal diagnostics. Eur Radiol 11:1753–1759, 2001. 22. Grainger J, Duryea J, Elliott JM, Genant HK. The evaluation of a new digital semi-automated system for the radiological assessment of distal radial fractures. Skeletal Radiol 31:457–463, 2002.
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Radiographic Angles in Hallux Valgus: Comparison between Manual and Computer-Assisted Measurements Subodh Srivastava, FRCS (Orth & trauma) 1, Nachiappan Chockalingam, PhD 2, Tarek El Fakhri, FRCS 3 1 Orthopaedic Surgeon and Visiting Fellow, Faculty of Health, Staffordshire University, Stoke on Trent, UK; Orthopaedic Surgeon and Visiting Fellow, Orthopaedics & trauma, Mid Staffordshire NHS Foundation Trust, Stafford, UK 2 Professor of Clinical Biomechanics, Faculty of Health, Staffordshire University, Stoke on Trent, UK 3 Consultant Orthopaedic Surgeon, Orthopaedics & trauma, Mid Staffordshire NHS Foundation Trust, Stafford, UK
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 5 Keywords: radiographic angles hallux valgus manual and computer-assisted measurement technical error of measurement
Radiographic angles are used to assess the severity of hallux valgus deformity, in preoperative planning, assessing postoperative outcomes, and in comparing results between interventions. The manual method to measure these angles has been shown to be prone to errors and to be time consuming. Computer programs are now available to assist in angular measurements. This study was undertaken to compare the reliability and time taken between the 2 methods. A total of 30 radiographs were used from a population of patients with hallux valgus deformity. The radiographs were digitized for computer-assisted measurements. The technical error of measurement (TEM) was calculated for intra- and interobserver data to assess the error in angular measurement with both methods. The technical error of measurement was lower with the computer-assisted method, suggesting that this method is more reliable. Furthermore, the time taken was also reduced with this method.) Ó 2010 by the American College of Foot and Ankle Surgeons. All rights reserved.
Radiographic angles are used to assess the severity of hallux valgus deformity, and in selecting type of surgical procedure for correction, assessing postoperative outcomes, and comparing results with other studies. The radiographic angles commonly measured are hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), and interphalangeal angle (IPA). The manual method to measure these angles on weight-bearing radiographs involves identifying anatomical landmarks, using marker pens, and measuring angles with a goniometer. This method is prone to errors, and can be time consuming and arduous, especially measurements done after surgery (1–5). These errors can be reduced by using standardized technique for performing weight-bearing anteroposterior radiographs and by defining reference points for first metatarsal axis and other anatomical landmarks (6). Digital workstations are now being widely used to view and store digitized images of radiographs. Computer software is available to aid in the measurement of radiographic angles. Angular measurements of digitized images using computer software has been reported by various authors for Cobb angle in spine x-rays (7, 8), and for angles in hallux valgus (9–11). Financial Disclosure: None reported. Conflict of Interest: None reported. Address correspondence to: Subodh Srivastava, FRCS (Orth & Trauma), Faculty of Health, Staffordshire University, West view, Newcastle Road, Loggerheads, Shropshire TF9 4PH, UK. E-mail address: [email protected] (S. Srivastava).
In this study, we used specifically designed software for computerassisted measurements of 4 radiographic angles on anteroposterior radiographs of the foot. We hypothesize that this would remove intrinsic errors seen with the manual method, improve reliability, decrease the time spent to obtain measurements, and be user friendly. Objectives The main objective of this study was to compare the inter- and intraobserver reliability between manual measurements using marker pen and goniometer, and computer-assisted measurements of digitized images using software, for radiographic angles in hallux valgus (HVA, IMA, DMAA, and IPA). The secondary objective was to compare the time taken between these 2 methods. Methods Study design This observational study was conducted at Stafford General Hospitals NHS Trust, after approval from the local research and ethics committee (LREC). Selection of radiographs Thirty radiographs performed preoperatively for patients with hallux valgus deformity seen in an outpatient clinic in January 2007 were used in this study. The radiographs had been taken using standard technique with the patients weight bearing, 15-degree angulation of the x-ray tube toward the ankle, and centered on the midfoot.
1067-2516/$ - see front matter Ó 2010 by the American College of Foot and Ankle Surgeons. All rights reserved. doi:10.1053/j.jfas.2010.07.012
524
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
All identifying information of patients was removed and copies of radiographs used had no further patient data. Digitized images of radiographs The radiographs were digitized using a digital camera and the images were stored electronically. The distance between camera and radiographs, lighting, and zoom were kept the same for all images. Angles measured The following 4 angles were measured: HVA: The angle between the longitudinal axes of the first metatarsal and proximal phalanx of the first toe. IMA: The angle between the longitudinal axes of the first and second metatarsals. DMAA: The angle between the longitudinal axis of the first metatarsal and a line through the distal articular surface of the first metatarsal. IPA: The angle between the longitudinal axes of the proximal and distal phalanx of the first toe.
Observers The radiographs and digitized images were assessed by 3 observers: 1 orthopedic surgeon with special interest in foot and ankle 1 orthopedic surgeon (general) 1 trainee in orthopedics and trauma We felt that computer-assisted measurements with the specifically designed software would be reliable with skilled and experienced observers, as well as observers with little or no experience in performing angular measurements in hallux valgus, and hence we used observers with different levels of experience. The study was planned to include 4 observers; however, one of the observers (junior trainee) left the hospital for further training, and could not complete the observations. The measurements carried out by this observer were excluded from the study. Group A: Manual measurements Manual measurements were completed using marker pen and goniometer. Reference points were made in the first metatarsal, second metatarsal, proximal phalanx, and distal phalanx of the first toe and distal articular surface of the first metatarsal, using guidelines published by the ad hoc committee of the American Orthopaedic Foot and Ankle Society (AOFAS) on angular measurements (12). The axes were then drawn in the respective bones and angles measured using a goniometer (Table 1 and Fig. 1). All the observers were given a sheet outlining the guidelines and a demonstration was provided on performing the angular measurements, with special emphasis on the placement of reference points. The observers were also given an opportunity to take readings on a few radiographs and seek any clarification regarding the manual method of angular measurement (Fig. 2).
The software then automatically computes the various axes and measures the 4 angles (HVA, IMA, DMAA, and IPA). The software was demonstrated and all the observers had an opportunity to use this technique on the computer a few times before the measurements were recorded (Fig. 3). Collection of data The 3 observers reviewed the radiographs and digitized images 3 separate times at 1-week intervals. The order of the images was changed on each reading and the measurements were done alternating between methods as follows: Week Week Week Week Week Week
1: 2: 3: 4: 5: 6:
manual measurement computer-assisted measurement manual measurement computer-assisted measurement manual measurement computer-assisted measurement
None of the observers had access to their previous measurements or measurements of the other observers. All the measurements were recorded on Excel sheets electronically. A total of 1080 measurements were recorded in each group (30 images 4 angles 3 observers 3 readings). The data were analyzed after the 3 observers completed all the measurements using both methods. The time taken to complete the measurements by both methods was recorded for all 3 observers. Analysis of data The means and standard deviations of the 3 readings of the 4 angles, done by each examiner for all 30 images by both methods, were calculated. The intra- and interobserver errors of measurement were calculated using technical error of measurement (TEM), a standard method reported in the literature (13, 14). The TEM was estimated using the following formula: ffi vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 3 u u PK u MðnÞ 7 1 uPN 6 6 PK 7 u MðnÞ2 7 u 16 K 4 1 5 u u t NðK 1Þ where N is the number of subjects (in this study, number of radiographs), M(n) is the nth replicate of measurement, and K is the number of determinations. This formula provides an estimate of measurement error in the units of measurement of the variable (in this study in degrees). The measurement error is less if the TEM with a measurement technique is low, indicating greater reliability. The reliability coefficient (R), which is not estimated in degrees, is estimated using the following formula: R ¼ 1 – ([TEM ]2/[SD ]2). This coefficient (R) ranges on a scale from 0 to 1, and gives an estimation of error in the inter- and intraobserver measurement variance. If the R is 0.8, then the data are 80% error free. Time taken to perform the measurements by the 2 methods was noted. The mean time taken to measure the 4 angles on each image was calculated and comparison done between the 2 methods.
Results
Group B: Computer-assisted measurements
Intraobserver data The computer-assisted measurements were performed using a computer and special software developed locally (MATLAB; The Math Works Inc., Natick, MA). The reference points were placed with a mouse by the observers, using the following guide: - metaphyseal-diaphyseal junction proximally and distally in the first metatarsal, second metatarsal, and proximal and distal phalanx of the first toe - the medial and lateral limits of the distal articular surface of the first metatarsal
The intraobserver error was assessed by calculating the TEM for the 3 observers (Table 2). The intraobserver error was less with the computer-assisted method for all 4 angles, including the DMAA. The TEM (observer 1) improved from 2.32 to 2.24 for HVA, 1.9 to 1.33 for IMA, 3.9 to 2.97 for DMAA, and 2.03 to 1.84 for IPA. Furthermore, the
Table 1 American Orthopaedic Foot and Ankle Society criteria for reference points The reference point should be placed as close as possible to the diaphysis. The midpoint on the transverse line joining the reference points proximally and distally is taken and joined to give the longitudinal axis. First metatarsal reference points The reference points should be located in the metaphyseal/ diaphyseal region 1–2 cm proximal to the distal articular surface and 1–2 cm distal to the proximal articular surface. The 1-cm range allows for various sized feet. Second metatarsal reference points The reference points should be located in the metaphyseal/ diaphyseal region 1–2 cm proximal to the distal articular surface and 1–2 cm distal to the proximal articular surface. First toe, proximal phalanx The proximal phalanx is substantially shorter, which leaves more room for errors in angular measurement. They recommended metaphyseal/ reference points diaphyseal reference points 0.5 to 1.0 cm proximal or distal to the articular surfaces. Similar points can be placed on the distal phalanx of first toe.
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
525
Fig. 1. The location of reference points for the first metatarsal. Fig. 2. A sample radiograph with manual measurements.
error was reduced for the other 2 observers, including observer 3 who had the least experience and skill level in performing angular measurements for hallux valgus. The reliability coefficient (R) was calculated using the TEM for all 3 observers (Table 3). The R was higher than 0.97 for all 3 observers, suggesting that more than 97% of measurements were error free. Interobserver data The mean of the 3 measurements by each observer were taken to calculate the TEM by the 2 methods (Table 4). The TEM was reduced with computer-assisted measurements for all 4 angles. The error in measurement was highest for DMAA by both methods, reflecting the problems encountered in measuring this angle. The lowest error was for the IMA by both methods (TEM of 1.37 and 1.19 for IMA versus 2.17 and 3.38 for DMAA by manual and computer-assisted methods respectively). The reliability coefficient was calculated using the TEM for the 2 methods (Table 5). The R was consistently higher than 0.98 with both methods, suggesting that more than 98% of measurements were error free. Time taken for measurements with both methods The time taken to measure the 4 angles (HVA, IMA, DMAA, and IPA) on each image by the 3 observers using both methods was
recorded on all 3 sets of readings. The mean time taken was calculated and is presented in Table 6. The time taken was greater with the manual method for all 3 observers. Among the 3 observers, observer 1 (most skilled) took the least time and observer 3 (least skilled) took the most time to complete measurements on each image. With repeated measurements, the time taken was reduced and on the third set of manual measurement, all 3 observers recorded less time. The computer-assisted method greatly reduced the time taken to perform angular measurements, with less time taken for the third set, as observers became familiar with the software used. The time taken to do measurements was almost similar for all 3 examiners in the third set irrespective of the level of skill and experience. Discussion Radiographic angles are measured to assess severity of deformity, choose type of surgical procedure, assess postoperative correction, and compare results. The use of angular measurements is based on the belief that they are reliable, repeatable, and provide a constant value for comparison with other studies. The traditional method of measuring angles on plain radiographs is by using marker pens, placing reference points, identifying axis of the respective bones, and measuring angles with a protractor or goniometer.
526
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
Table 3 The R value for the 3 observers, intraobserver data Intraobserver data R value (reliability coefficient) Angle
HVA IMA DMAA IPA
Observer 1
Observer 2
Observer 3
Manual
Computer
Manual
Computer
Manual
Computer
0.98 0.99 0.96 0.98
0.99 0.99 0.97 0.96
0.98 0.99 0.98 0.99
0.99 0.99 0.98 0.99
0.99 0.98 0.96 0.98
0.99 0.98 0.97 0.99
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle.
Fig. 3. A sample digitized image with computer-assisted measurements.
The manual method, however, is prone to errors and various studies have evaluated intraobserver and interobserver measurement error. The DMAA is particularly prone to measurement error, and is related to difficulty in identifying the limits of the articular surface (15, 16). More recently, Robinson et al (17) observed that the DMAA varies significantly in a linear pattern with axial rotation of the first metatarsal, suggesting the inaccuracy of extrapolating the DMAA from plain anteroposterior radiographs. The errors can be reduced by standardizing the technique of weight-bearing radiographs (18) and having specific guidance for placement of reference points (6). The AOFAS guideline for placement of reference points at the metaphyseal-diaphyseal junction of first metatarsal, second metatarsal, and proximal phalanx are widely used (12). Shima et al (19) evaluated radiographs before and after Table 2 Intraobserver error (TEM) in angular measurements: manual versus computer-assisted method Intraobserver error (TEM) Angle
HVA IMA DMAA IPA
Observer 1
Observer 2
a proximal crescentic osteotomy performed for the treatment of hallux valgus. A line connecting the centers of the first metatarsal head and the proximal articular surface of the first metatarsal to define its longitudinal axis gave the best intraobserver and interobserver reliability for the measurement of the hallux valgus and intermetatarsal angles. However, there are sources of intrinsic error with the manual method, such as the use of variable-width marker pens, inaccuracy of protractors, error in approximating the angle, and difficulty in redrawing lines in the event of a mistake in placement of the reference points. The manual method can be time consuming and arduous as well. Although digital radiography is now available in more centers and is replacing conventional radiography, the computer workstation is used to store, view, and retrieve images among other routine work in clinics. In this context, customized computer software creates the opportunity for quick, easy, and reliable measurements. Various authors have explored the use of digital imaging in orthopedic settings. Early in the implementation of digital imaging, Ackerman et al (20) compared digital with analog reading for fracture detection and found that sensitivity and specificity were better with analog films. Observers noted that workstations were cumbersome and slow, and there was degradation in image quality. However, computers and digital imaging technology have improved, and digital radiography is now accepted and is rapidly replacing standard radiography. Hamers et al (21) reported their institution’s clinical experience with digital radiography and found that 3 of the 6 radiologists preferred the digital system and 3 had no preference. Grainger et al (22) evaluated a digital semiautomated system for the radiological assessment of distal radial fractures. They found improved intra- and interobserver agreement in measuring parameters such as radial angle, length, and dorsal shift. Angular measurements of digitized images using computer software have been reported by various authors for Cobb angle in spine x-rays. Shea et al (7) did a study that compared manual with computer-assisted measurement of Cobb angle to assess deformity in scoliosis patients. The intraobserver variability was 3.3 degrees for the manual set, and 2.6 degrees for the digitized images. The study concluded that
Table 4 Interobserver error (TEM) in angular measurements: manual versus computer-assisted method Interobserver error (TEM)
Observer3
Manual
Computer
Manual
Computer
Manual
Computer
Angle
Manual
Computer
2.32 1.9 3.9 2.03
2.24 1.33 2.97 1.84
2.64 2.27 3.04 2.52
1.58 1.33 2.76 1.61
2.52 2.51 4.07 2.98
1.68 1.6 3.68 2.18
HVA IMA DMAA IPA
2.49 1.37 3.38 2.23
1.59 1.19 2.17 1.98
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle; TEM, technical error of measurement.
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle; TEM, technical error of measurement.
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
Table 5 R value (reliability coefficient) for interobserver data Interobserver data R value Angle
Manual
Computer
HVA IMA DMAA IPA
0.97 0.98 0.96 0.99
0.99 0.98 0.98 0.99
Abbreviations: DMAA, distal metatarsal articular angle; HVA, hallux valgus angle; IMA, intermetatarsal angle; IPA, interphalangeal angle.
using a computer might reduce intrinsic measurement errors with the manual technique using marker pens and protractors. Chockalingam et al (8) devised a study to develop a computerized method for measuring and quantifying the magnitude of spinal curvature. A computer program was developed to assess the spinal deformity and measure the Cobb angle on digitally scanned images. The reliability was assessed using TEM and R. The mean inter- and intraobserver errors in measurement were considerably lower with computer-assisted measurements. Furthermore, the results were similar for all the observers, suggesting that accurate and reliable measurements were possible, even if the assessor is not highly skilled or experienced. Angular measurements of digitized images using computer software have been reported by various authors for angles in hallux valgus (9–11). None of these studies have evaluated the inter- and intraobserver reliability for all 4 angles and compared time taken between the 2 methods. Our hypothesis was that with use of computer software specifically designed for angular measurements in hallux valgus, measurement error would be reduced. Furthermore, the technique would be quick and easy to use, and be reliable in the hands of inexperienced observers as well. Intra- and interobserver error and time taken for measurement In this study, the TEM was measured to assess the error in measurement of radiographic angles. The intraobserver error and interobserver error were less with the computer-assisted method for all 4 angles, including the DMAA. Furthermore, the error was reduced for all 3 observers, including observer 3 who had the least experience and skill level in performing angular measurements for hallux valgus (Tables 1 and 3). None of the previous studies have assessed the ease of use and compared the time taken between the 2 methods. In this study, the time taken to perform angular measurements by the 2 methods was compared (Table 5). The computer-assisted method was found to be quick and easy to use by all 3 observers, and in the third set of measurements, all observers had recorded almost similar times. Comparison with previous studies Panchbhavi and Trevino (9) did a study to compare inter- and intraobserver reliability in measuring 3 angles (HVA, IMA, and DMAA) by manual and computer-assisted methods. No difference was noted between the 2 methods. This was attributed to the small number of Table 6 Mean time taken for angular measurements Mean time taken for angular measurements on an image (minutes) Observer
1 2 3
Manual
527
radiographs and fewer angles measured (20 radiographs and 3 angles versus 30 radiographs and 4 angles in this study). Panchbhavi and Trevino (9) also commented that the software used was probably not user friendly and observers were not used to working with digital images resulting in a long learning curve. Over the years, computer workstations have become more widely available and health professionals use digital images much more commonly. Furthermore, the software used in this study was specially designed to measure angles in the foot. Farber et al (10) looked at the reliability in measuring HVA and IMA and compared the 2 methods. The computerized method gave better overall reliability with interobserver agreement (measurement within 2 degrees), improving from 66% with plain films to 80% with digital workstation. The IMA was similarly more reliable with the computer-assisted method. Their findings were similar to the observations in the present study; the only difference being that all 3 observers in the study were highly experienced foot and ankle surgeons who were used to performing manual measurements routinely. In the present study, the observers had different levels of experience, and the reliability improved with the computer-assisted method for the least-skilled observer as well. Furthermore, the study did not look at the DMAA and IPA and did not compare the time taken between the 2 methods. Piqué-Vidal et al (11) looked at all 4 angles but did not evaluate the interobserver reliability. Manual measurements were made by an orthopedic surgeon, and angular measurements of digitized images were performed by an independent technician, trained to use the computer software (Autocad 2000, Autodesk Inc., San Rafael, CA). A total of 176 weight-bearing radiographs were used. The intraobserver reliability was evaluated and better results were noted with the computer-assisted method. The software used in the present study was designed specifically to measure the radiographic angles in hallux valgus. The computer program was developed using MATLAB. The technique involves placement of relevant reference points on the digital image using the mouse by the observer. All the other steps (joining the reference points, identifying the longitudinal axis, and measuring the angles) are performed by the software. This eliminates the intrinsic errors associated with manual methods such as use of variable-width marker pens, inaccurate protractors, and errors in estimating angles with varying protractors. This is reflected in the reduced error (both intra- and interobserver error) with the computer-assisted method in this study for all 4 angles, irrespective of the skill level of the observer. Furthermore, the software is easy to use, with a small learning curve, resulting in reduced time taken to complete angular measurements and almost similar findings for observers with varying experience by the third reading. This would be relevant in the clinical setting, in providing clinicians the opportunity to measure the angles quickly in outpatients where time constraints are often present. In conclusion, many different angles and other critera, such as sesamoid position, are used to assess hallux valgus deformity, of which the most commonly used angles are HVA, IMA, DMAA, and IPA. The manual method using specific guidelines such as those outlined by AOFAS and computer-assisted methods using available software are currently accepted as standard techniques. This project was undertaken as a pilot study to assess the role of computer-assisted measurements in patients with hallux valgus deformity. Specially designed software was used to measure 4 angles in 30 radiographs. The results suggest the following:
Computer
1st set
2nd set
3rd set
1st set
2nd set
3rd set
1.8 2.2 3.0
1.5 2.0 2.8
1.4 1.8 2.5
0.5 0.8 1.0
0.4 0.6 0.8
0.4 0.5 0.6
The measurement error can be reduced with the computerassisted method The measurement error is reduced irrespective of experience and skill level with the computer-assisted method
528
S. Srivastava et al. / The Journal of Foot & Ankle Surgery 49 (2010) 523–528
The time taken with the computer-assisted method is less Overall, the computer-assisted method was found to be more reliable and user friendly A limitation of this study was that a small number of radiographs were used and the digitized images were taken using a digital camera. The same camera was used and all parameters such as lighting and zoom were kept constant, but some variability in images is possible. Further studies need to be undertaken with larger numbers of radiographs to firmly establish the benefit of computer-assisted methods. Furthermore, special software that can assess all possible radiographic parameters in hallux valgus would be vastly helpful to the clinician. Although a comparison of different types of software currently available to perform angular measurements would be interesting, a study to establish correlation between improvement in radiographic angles in hallux valgus and improvement in symptoms of patients would be very useful for the clinician. Acknowledgment The authors acknowledge the technical assistance provided by Dr Chi-Wen Lung. References 1. Saltzman C, Brandser E, Berbaum K, DeGnore L, Holmes J, Katcherian D, Teadsall R, Alexander I. Reliability of standard foot radiographic measurements. Foot Ankle 15:661–665, 1994. 2. Resch S, Ryd L, Stenstorm A, Johnson K, Raynisson K. Measuring hallux valgus: a comparision of conventional radiography and clinical parameters with regard to measurement accuracy. Foot Ankle 16:267–270, 1995. 3. Schneider W, Knahr K. Metatarsophalangeal and intermetetarsal angle: different values and interpretation of postoperative results dependent on the technique of measurement. Foot Ankle 19:532–536, 1998. 4. Coughlin MJ, Freund E. The reliability of angular measurements in hallux valgus deformities. Foot Ankle 22:369–379, 2001. 5. Condon F, Kaliszer M, Conhyea D, O'Donnell T, Shaju A, Masterson E. The first metatarsal angle in hallux valgus: an analysis of measurement reliability and the error involved. Foot Ankle 22:717–721, 2002.
6. Schneider W, Csepan R, Kasparek M, Pinggera O, Knahr K. Intra and interobserver repeatability of radiographic measurements in hallux surgery. Acta Orthop Scand 6:670–673, 2002. 7. Shea KG, Stevens PM, Nelson M, Smith JT, Masters KS, Yandow S. A comparision of manual versus computer-assisted radiographic measurement. Intraobserver measurement variability for Cobb angles. Spine 23:551–555, 1998. 8. Chockalingam N, Dangerfield PH, Giakas G, Cochrane T, Dorgan JC. Computer assisted Cobb measurement of scoliosis. Eur Spine J 11:353–357, 2002. 9. Panchbhavi VK, Trevino S. Comparision between manual and computer assisted measurements of hallux valgus parameters. Foot Ankle 25:709–711, 2004. 10. Farber DC, DeOrio JK, Steel MW. Goniometric versus computerised angle measurement in assessing hallux valgus. Foot Ankle 26:234–238, 2005. 11. Piqué-Vidal C, Maled-Garcia I, Arabi-Moreno J, B-Stat JV. Radiographic angles in hallux valgus: differences between measurements made manually and with a computerised program. Foot Ankle 27:175–180, 2006. 12. Coughlin MJ, Saltzman CL, Nunley JA. Angular measurements in the evaluation of halluxvalgus deformities: A report of the Ad Hoc committee of the American Orthopaedic Foot and Ankle Society on angular measurements. Foot Ankle 23:68– 74, 2002. 13. Mueller WH, Martorell R. Reliability and accuracy of measurement. In Anthropometric Standardisation Reference Manual, pp 83–86, edited by TG Lohman, AF Roache, R Martorell, editors, Human Kinetics Books, Champaign, IL, 1988. 14. Ulijaszek S, Lourie J. Intra and inter observer error in measurement. In Anthropometry: The Individual and the Population, pp 30–55, edited by S Ulijasezek, Cambridge University Press, , 1994. 15. Vittetoe D, Saltzman C, Krieg J, Brown T. Reliability and validity of distal metatarsal articular angle. Foot Ankle 15:541–547, 1994. 16. Chi TD, Davitt J, Younger A, Holt S, Sangeorzan BJ. Intra- and Inter-observer reliability of the distal metatarsal articular angle in hallux valgus. Foot Ankle 22:722–726, 2002. 17. Robinson AH, Cullen NP, Chhaya NC, Sri-Ram K, Lynch A. Variation of the distal metatarsal articular angle with axial rotation and inclination of the first metatarsal. Foot Ankle Int 27(12):1036–1040, 2006. 18. Smith RW, Reynolds JC, Stewart MJ. Hallux valgus assessment: report of research committee of American Orthopaedic Foot and Ankle Society. Foot Ankle 5:92–103, 1984. 19. Shima H, Okuda R, Yasuda T, Jotoku T, Kitano N, Kinoshita M. Radiographic measurements in patients with hallux valgus before and after proximal crescentic osteotomy. J Bone Joint Surg Am A91(6):1369–1376, 2009. 20. Ackerman SJ, Gitlin JN, Gayler RW, Flagle CD, Bryan RN. Reciever operating characteristic analysis of fracture and pneumonia detection: comparision of laserdigitised workstation images and conventional analog radiographs. Radiology 186:263–268, 1993. 21. Hamers S, Freyschmidt J, Neitzel U. Digital radiography with a large-scale electronic flat-panel dtector vs screen film radiography: observer preference in clinical skeletal diagnostics. Eur Radiol 11:1753–1759, 2001. 22. Grainger J, Duryea J, Elliott JM, Genant HK. The evaluation of a new digital semi-automated system for the radiological assessment of distal radial fractures. Skeletal Radiol 31:457–463, 2002.