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research-article2014

FAIXXX10.1177/1071100714558846Foot & Ankle InternationalWilliamson et al

Article

New Radiographic Parameter Assessing Hindfoot Alignment in Stage II Adult-Acquired Flatfoot Deformity

Foot & Ankle International® 2015, Vol. 36(4) 417­–423 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1071100714558846 fai.sagepub.com

Emilie R. C. Williamson, BS1, Jeremy Y. Chan, MD1, Jayme C. Burket, PhD1, Jonathan T. Deland, MD1, and Scott J. Ellis, MD1

Abstract Background: The hindfoot moment arm is a reliable measurement of hindfoot valgus deformity in stage II adult-acquired flatfoot deformity (AAFD) and can be used to guide intraoperative correction of the hindfoot. There is currently little understanding of how the hindfoot moment arm relates to angular measurements of hindfoot alignment. The purpose of this study was to develop a new hindfoot alignment angle that can reliably quantify hindfoot valgus in patients with AAFD and to establish the relationship of this angle with the hindfoot moment arm. Methods: Preoperative hindfoot alignment radiographs were reviewed for 10 consecutive patients (10 feet) who were indicated for reconstruction for stage II AAFD. A second group of 10 patients (10 feet) without flatfoot were identified to serve as normal controls. The hindfoot moment arm and the new hindfoot alignment angle were measured in blinded fashion by 2 readers. Reliability was assessed using intraclass correlation coefficients (ICCs). The difference in angle between normal and flatfoot patients was assessed with a Mann-Whitney U test. A linear regression model was used to assess the relationship between hindfoot moment arm and the new hindfoot alignment angle. Results: Intra- and interrater reliability for the hindfoot alignment angle was excellent (ICC = 0.979 and 0.965, respectively). Flatfoot patients had greater mean angles than did normal patients (22.5 ± 4.9 vs 5.6 ± 5.4 degrees, P < .001). The hindfoot moment arm was correlated significantly with the hindfoot alignment angle (P < .001), increasing by 0.81 mm for every degree increase in angle (adjusted R2 = 0.9046). Conclusion: These results indicate that the new hindfoot alignment angle is a reliable measure of hindfoot valgus and can differentiate between flatfoot and normal patients. In addition, the strong linear relationship between the hindfoot alignment angle and moment arm may allow for the use of this angle in the intraoperative correction of hindfoot valgus. Level of Evidence: Level III, retrospective case control study. Keywords: adult-acquired flatfoot deformity, hindfoot alignment, hindfoot valgus, flatfoot reconstruction Adult-acquired flatfoot deformity (AAFD) is a complex combination of multiple deformities and may be subdivided into stages.4 Plain radiographs are a common and useful tool implemented to assess AAFD before, during, and after surgery. However, difficulty still remains in radiographically quantifying the deformity in a clinically relevant way, particularly given that the location and severity of deformity can vary considerably between patients. This variation requires different types and amounts of accessory procedures once surgery is indicated. The medializing calcaneal osteotomy (MCO) has been shown to correct the valgus hindfoot alignment typically seen in AAFD and deliver clinically satisfactory results in patients with stage II AAFD.3,10 Medializing calcaneal osteotomy has also been found to be the main predictor of correction in hindfoot valgus alignment following flatfoot

reconstruction as measured by the change in hindfoot moment arm.3 The hindfoot alignment moment arm is well described, reliable, and frequently used1-3,13 but proves to be tedious and implicates the use of the moment arm as opposed to an angle. Furthermore, the moment arm is less able to account for what is seen when clinically examining patients. Unfortunately, there is currently little understanding of how the hindfoot moment arm relates to angular measurements of hindfoot alignment, which are more commonly 1

Department of Foot and Ankle Surgery, Hospital for Special Surgery, New York, NY, USA Corresponding Author: Scott J. Ellis, MD, Department of Foot and Ankle Surgery, Hospital for Special Surgery, 535 East 70th St, New York, NY, 10021, USA. Email: [email protected]

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Table 1.  Demographic Variables and Flatfoot Radiographic Parameters. Normal

Flatfoot



Demographic

No. of Subjects

Parameter ± SD

No. of Subjects

Parameter ± SD

a

10 10 10

29.1 ± 8.3 22.0 ± 2.4 40%

10 10 10

53.4 ± 8.0 25.9 ±5.1 70%

10 10 10 10

12.1 ± 6.1 26.3 ± 3.4 0.2 ± 4.9 20.0 ± 3.1

10 10 10 10

29.5 ± 6.5 39.5 ± 7.0 –22.5 ± 6.9 15.8 ± 2.9

Age, y Body mass indexa Sexc Flatfoot parameter   AP TN coverage, dega   AP TN uncoverage %a   L talo–first MA, dega   Calcaneal pitcha

P Value .0003b .0539 .389   .0002b .0003b .0002b .0113b

AP TN coverage, anteroposterior talonavicular coverage angle; AP TN uncoverage %, anteroposterior talonavicular uncoverage percentage; L talo–first MA, lateral talo–1st metatarsal angle; SD, standard deviation. a Numerical variable. b Only P values less than .05 were considered significant. c Categorical variable, represented as the percentage of female subjects in the group.

used in practice and may be more intuitive in clinical and surgical settings. Some studies have investigated an angle between the tibial axis and the calcaneus to measure a hindfoot valgus angle, but these angles are not representative of a calcaneal axis drawn down the center of the calcaneal tuberosity analogous to what is more typically observed on physical examination.2,5 Also, the angles previously studied have not been investigated with regard to flatfoot vs normal patients. The purpose of this study was therefore to develop a new hindfoot alignment angle measured on the hindfoot alignment view13 that can reliably quantify hindfoot valgus in patients with AAFD and to establish the relationship of this angle with the hindfoot moment arm. We hypothesized that there would be a linear correlation between the hindfoot moment arm and this new hindfoot alignment angle and that this angle could differentiate between normal and flatfoot patients. We anticipate that in building on previous work, a relationship between the hindfoot alignment angle and moment arm may allow for the use of this parameter and an algebraic equation to quantify the intraoperative correction of hindfoot valgus through MCO.

Methods Ten consecutive patients with preoperative hindfoot alignment views who underwent flatfoot reconstruction for stage II AAFD by 2 surgeons, fellowship trained in foot and ankle surgery, were identified (JD, SE). The patients had surgery between January 2010 and April 2012 and were identified through the Foot and Ankle Registry at the investigators’ institution. Ten healthy patients without a history of foot and ankle pain, pathology, deformity, or previous injury or surgery were recruited as controls. Their

radiographs had been taken between April 2010 and June 2011. A hindfoot alignment view, capturing both feet, was taken of these control patients in identical fashion as that in the study group. Other standard radiographs were taken of both groups as described below. The study was approved by the institutional review board at the investigators’ institution. Demographic data collected for both groups included age, sex, body mass index (BMI), and the date of preoperative radiograph. The flatfoot cohort included 3 men and 7 women (5 left, 5 right) with a mean age of 53.4 years (range, 38.5-63.5 years) and a mean body mass index (BMI) of 25.9 kg/m2 (range, 18.4-34.6 kg/m2). The control group (10 feet) included 6 men and 4 women (5 left, 5 right) with a mean age of 29.1 years (range, 21.5-47.1 years) and a mean BMI of 22.0 kg/m2 (range, 18.8-26.5 kg/m2). There was no significant difference between flatfoot and normal patients in terms of BMI (P = .054) or sex (P = .385). Compared with normal patients, however, flatfoot patients were older (P < .001) (Table 1).

Radiographic Parameters The amount of hindfoot valgus was measured for the hindfoot moment arm13 and the new hindfoot alignment angle using a picture archiving and communication system (PACS; Philips Medical Systems, Best, Netherlands) for all patients in this study. The new hindfoot alignment angle was defined as the angle formed by the intersection of the longitudinal axis of the tibial shaft13 and the axis of the calcaneal tuberosity. The calcaneal axis was determined by bisecting 2 transversals between 2 lines adapted to the lateral and medial osseous contours of the calcaneus. The line adapted to the lateral osseous contour was drawn between the most lateral

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Figure 1.  The hindfoot alignment angle was defined as the angle formed by the intersection between the tibial axis and the calcaneal axis. Flatfoot patient: (a) The tibial axis was draw as defined by Saltzman and el-Khoury13 by bisecting 2 pairs of points on the tibial shaft cortex drawn 100 mm and 150 mm proximal to the tibial plafond. A line connecting the bisection marks was extended inferiorly and was defined as the tibial axis (line A). (b, c) The calcaneal axis was determined by bisecting 2 transversals between 2 lines adapted to the lateral and medial osseous contours of the calcaneus. (b) The line adapted to the lateral osseous contour (line B) was drawn between the most lateral aspect of the lateral process on the calcaneal tuberosity (point B1) and the most superior and lateral discernable aspect of the calcaneus (point B2). The line adapted to the medial osseous contour (line C) was drawn from the most medial aspect of the medial process of the calcaneal tuberosity (point C1) to the most inferomedial discernable aspect of the sustentaculum tali (point C2). (c) The transversals (line D1 and line D2) were drawn with equal consecutive interior angles (angles α). That is to say that line D1 and line D2 are parallel and form all equal angles (α) at the intersection points with line B and line C. The segments of line D1 with a single hatch mark are congruent. The segments of line D2 with a double hatch mark are congruent. (d) Line E demonstrates the calcaneal axis, which is a bisector of the transversal lines D and thus a bisector between the medial and lateral osseous contours of the calcaneus.

aspect of the lateral process on the calcaneal tuberosity and the most superior and lateral discernable aspect of the calcaneus. The line adapted to the medial osseous contour was drawn from the most medial aspect of the medial process of the calcaneal tuberosity to the most inferomedial discernable aspect of the sustentaculum tali. The transversals were drawn with equal consecutive interior angles (Figures 1 and 2). The new angular measurements were made on 2 separate occasions by 2 independent investigators in a blinded fashion. The investigators were simultaneously instructed by a surgeon, fellowship trained in foot and ankle surgery. Each investigator then practiced taking the measurements on sample radiographs while being observed. Each radiograph was removed of any patient identifiers, and the order was randomized prior to taking measurements. The

investigators were also unaware of the other investigator’s measurements or their own previous measurements. Each set of measurements was taken at least a day apart to ensure that the previous hindfoot alignment angle measurements were not remembered. The hindfoot moment arm measurements were made by a single investigator on only one occasion given that its reliability has already been established (Figure 3).13 Four other traditional flatfoot radiographic parameters were measured by 1 investigator using PACS, including anteroposterior (AP) talonavicular coverage angle, AP talonavicular uncoverage percent, lateral talo–first metatarsal angle, and calcaneal pitch. These traditional measurements were taken to confirm the differentiation of patients into flatfoot and control groups by comparing with previously established and validated norms.6,14

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Figure 2.  Simplified depiction of the hindfoot alignment angle measurements taken on (a) flatfoot patients and (b) the normal control patients.

Statistical Analysis Data analysis was performed with the help of a statistician using SAS version 9.3 (SAS Institute, Cary, North Carolina) with a level of significance set at α = 0.05. The primary objectives of this study were the measurement of the new hindfoot alignment angle and the moment arm. Intrarater and interrater reliabilities for the new hindfoot alignment angle were determined by calculating intraclass correlation coefficients (ICCs) and 95% confidence intervals. The reliability within and between raters was found to be excellent, and thus the first rater was used for all further analyses. A linear regression model was used to assess the relationship between the hindfoot moment arm and the new hindfoot alignment angle as well as to determine if the relationship between the angle and moment arm differed in flatfoot vs normal patients. The difference in angle between normal and flatfoot patients was assessed with a MannWhitney U test. Differences in patient demographic features between normal and flatfoot patients were assessed with a MannWhitney U test (for age, BMI, calcaneal pitch, talonavicular coverage angle, talonavicular uncoverage percent, and lateral talo–first metatarsal angle) and a Fisher exact test (for sex). Patient demographics are reported as mean ± standard deviation for continuous variables. Frequency and percentage are reported for categorical variables (Table 1).

Figure 3.  The hindfoot moment arm as defined by Saltzman and el-Khoury.13 The tibial axis was drawn by bisecting 2 pairs of points on the tibial shaft cortex drawn 100 mm and 150 mm proximal to the tibial plafond. A line connecting the bisection marks was extended inferiorly and was defined as the tibial axis. The moment arm was defined as the distance connecting the most inferior aspect of the calcaneus to the tibial axis line.

Results Radiographically, the flatfoot patients had a smaller calcaneal pitch (P = .011), a greater talonavicular coverage angle (P < .001), a higher talonavicular uncoverage percent (P < .001), and a decreased lateral talo–first metatarsal angle (P < .001). The average values for the calcaneal pitch, talonavicular coverage angle, talonavicular uncoverage percent, and lateral talo–first metatarsal angle fell within those ranges previous identified for control and flatfoot groups.6,14 Intra- and interrater reliability for the hindfoot alignment angle was excellent (intrarater ICC = 0.979 [95% CI, 0.9480.992]; interrater ICC = 0.965 [95% CI, 0.913-0.986]). In addition, flatfoot patients had greater mean angles than did normal patients (22.5 ± 4.9 vs 5.6 ± 5.4 degrees, P < .001) (Table 2). The hindfoot moment arm was correlated significantly with the hindfoot alignment angle (P < .001), increasing by 0.81 mm for every degree increase in angle (adjusted R2 = 0.9046) (Figure 4). Finally, there was no significant difference in the relationship between the angle and moment arm in the flatfoot vs normal cohorts. The difference in the moment arm between flatfoot and normal patients was explained by the difference in angle (P = .297).

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Williamson et al Table 2.  Hinfoot Alignment Angle and Moment Arm Measurements. Hindfoot Alignment Angle, deg Patient No. Normal   1   2    3    4   5   6   7    8    9  10 Flatfoot  11  12  13  14  15  16  17  18  19  20

R1M1

R1M2

–0.3 4.1 –1.3 15.2 3.1 8.1 3.2 11.4 10.2 2.6

–1.1 2 –3.7 14.8 5.9 8.1 3.5 10.5 11.6 4.4

27.3 25.4 19.9 15.7 24.3 16.1 22.6 17.5 20.7 25.9

28.6 27.8 24.8 16.0 27.3 16.8 25.3 16.7 16.7 23.7



R2M2

Moment Arm, mm

0.5 4.8 1.2 15.3 7.5 6.0 2.9 12.6 12.5 4.3

–0.8 5.2 0.9 16.7 6.8 8.6 6.4 13.7 13.7 3.2

–9 0.5 –9.1 7.5 2.6 3.1 0.3 6.6 5.0 –1.7

28.8 25.7 26.6 16.2 23.1 20.5 18.7 19.4 16.5 21.9

22.2 25.8 24.5 19.1 11.9 16.3 21.5 17.2 11.6 24.0

16.1 19.7 15.3 8.7 18.6 7.0 16.4 9.2 12.8 15.0

R2M1

Hindfoot alignment angle measurements (R1M1, R1M2, R2M1, R2M2) were done using the newly defined parameter. R1M1, rater 1, first measurment; R1M2, rater 1, second measurement; R2M1, rater 2, first measuremnet; R2M2, rater 2, second measurement.

Discussion The new hindfoot alignment angle developed in the current study was both reliable and differed between flatfoot and control, which supports the use of the angle in both research and clinical practice to assess hindfoot valgus and flatfoot deformity. It serves as a tool that theoretically more closely mimics physical examination findings and shows good linear correlation with the hindfoot moment arm, arguably the current gold standard. The findings in this study also suggest that it could be used as a tool to adjust intraoperative hindfoot valgus correction based on previous work.3 One limitation to the study was the difference in mean age and BMI between normal and flatfoot patients. Although the BMI was notably higher in the AAFD group, it did not reach significance. Age, however, did. These differences can be directly attributed to the fact that normal, healthy volunteers were chosen as controls and were consistently younger and weighed less than the patients with AAFD, who generally range in age from 45 to 65 years in the literature9 and, in general, are heavier.4 While these factors may

contribute to the development of AAFD, they do not appear to influence the reliability of the hindfoot alignment tested and would not alter surgical management in terms of the type and amount of correction needed. We also do not believe that they alter the conclusions that can be drawn. The usefulness of this new hindfoot alignment angle was the primary driving point in its development, since it is more clinically applicable than the previously defined moment arm.13 For example, when examining a patient clinically, it is customary to describe or quantify the amount of hindfoot valgus (or varus) in degrees and not in millimeters or moment arm. Similarly, when examining the amount of hindfoot valgus at the time of surgery in the supine patient, it is clinically more feasible to assess the angle of the heel with respect to the leg. Other angles have been previously assessed. In a hindfoot alignment measurement, Buck et al2 used either the medial or lateral osseous contours of the calcaneus to separately compare with the tibial axis to define a hindfoot angle. It is our belief that using both the medial and lateral osseous contours to create a mid-calcaneal axis more accurately captures the tilt of the calcaneus. This is because the medial and lateral osseous contours are often not parallel, thus creating different angles when combined with the tibial axis individually. That said, Buck et al discovered that the angle formed by the medial calcaneal osseous contour and the tibial axis was the most reliable hindfoot alignment measurement in their study. Presumably, the use of both osseous contours in our angular measurements would be similarly constant. Measurements in that study were not compared between flatfoot and control. In another hindfoot alignment measurement by Johnson et al,8 it was determined that the posterior portion of the calcaneus is the most important structure for determining the calcaneal axis, thus supporting our use of the calcaneal tuberosity for calcaneal alignment. The alignment of the calcaneal tuberosity was determined by imposing a best-fit ellipse over the x-ray and using the axis of the ellipse to represent the axis of the calcaneus. Although this is a reliable measure of hindfoot alignment, the use of a best-fit ellipse is not as clinically relevant as our hindfoot alignment angle. When looking at radiographs clinically, we find that drawing an angle may be more intuitively performed using the hindfoot alignment angle as we have defined, rather than an elliptical axis, and can be done easily with the aid of widely used PACS software. Robinson et al12 used a different method of defining the calcaneal axis. Their method involved a superior 50%-50% horizontal line division and an inferior 40%-60% horizontal line division forming the calcaneal axis, which they describe as corresponding to the line drawn on the surface bisecting the posterior rearfoot. Our axis is the bisector of both transversals that are based off of the medial and lateral osseous contours, not horizontal lines. We believe that our angle is

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Figure 4.  A linear regression model for the hindfoot alignment angle in relation to the hindfoot moment arm is shown. This figure depicts the strong positive linear relationship between hindfoot alignment angle and hindfoot moment arm (P < .0001). We found an increase in moment arm by 0.81 mm for every degree increase in angle (adjusted R2 = 0.9046).

superior in a clinical setting because it has the potential for application intraoperatively and is more relevant to the current literature, which relies on lines representative of the calcaneus osseous contours.2,5,7 Hirschmann et al7 evaluated the difference in computed tomography (CT) measurements of the hindfoot in upright weight-bearing and non–weight-bearing positions. The tibial axis was defined as the line perpendicular to the midportion of the tibiotalar joint surface, and the calcaneal axis was defined by the medial osseous contour. Although no significant difference was found between upright weight bearing and non–weight bearing for their hindfoot alignment angle, it was concluded that the alignment of the hindfoot does change significantly in the upright weight-bearing CT, allowing for more relevant clinical assessment of potential hindfoot deformity.7 The hindfoot alignment view used in this study13 is also taken in weightbearing stance.7 Reilingh et al12 assessed the differences in reliability between various radiographic measurements of the hindfoot. For hindfoot alignment, the 40%-60% line as described by Robinson et al11 was used. In addition, the group studied the parameters in both bilateral and unilateral stance. They concluded that the long axial view produces measurements that are more reliable than those of the hindfoot alignment view. Furthermore, there was not a greater reliability achieved with a unilateral weight-bearing stance as was anticipated. While our study implemented the hindfoot alignment view as opposed to the long axial view, we found both the interrater and intrarater reliability to be excellent. The hindfoot alignment view taken in our

practice captures both feet. Future studies should be performed to compare our angle between the hindfoot alignment and long axial views. Future studies are also necessary to correlate this hindfoot angular measurement to angles obtained on clinical, physical examination. It would also be worthwhile to see if a close comparison exists between this new angle and the angle created with the calcaneal axis defined by simply drawing a single line up the calcaneal tuberosity on the hindfoot alignment view radiographs that estimates its axis. Finally, the use of our proposed angle both before and after surgery would be beneficial to see if the change in hindfoot alignment is detectable or correlates with the amount of MCO performed intraoperatively. Unfortunately, there is no true intraoperative equivalent to the hindfoot alignment view, and thus the hindfoot alignment angle is limited to pre and postoperative radiographs. For normal asymptomatic patients, the average moment arm was 3.2 mm in varus.13 Following the study by Chan et al,3 which found a linear relationship between the change in hindfoot moment arm and the amount of MCO that must be performed to achieve this change, we implemented our study results with their linear equation to develop an equation describing the relationship between our hindfoot alignment angle and the amount of MCO needed to achieve the ideal hindfoot alignment. The final equation we developed relating hindfoot alignment angle and the amount of MCO was as follows: Change in hindfoot alignment angle (degrees) = 1.88 × amount of MCO (mm) – 1.42.

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Williamson et al It would be worth investigating this relationship further in a prospective manner to assess the validity, ideally comparing pre- and postoperative hindfoot alignment view radiographs and analyzing the preoperative hindfoot alignment angle, the amount of MCO performed, and the resulting hindfoot alignment. In conclusion, the new hindfoot alignment angle was a reliable measurement of flatfoot deformity in patients with AAFD, distinguished between flatfoot and normal patients, and was linearly correlated to the hindfoot moment arm. The new hindfoot alignment angle gave a more clinically relevant sense of the angle of deformity as opposed to the less intuitive moment arm and may ultimately prove useful in flatfoot reconstruction. Declaration of Conflicting Interests The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Scott J. Ellis, MD, received payments for teaching for Integra and paid consulting for Treace Medical Concepts (outside the submitted work).

Funding The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

References 1. Arangio G, Rogman A, Reed JF III. Hindfoot alignment valgus moment arm increases in adult flatfoot with Achilles tendon contracture. Foot Ankle Int. 2009;30(11):1078-1082. 2. Buck FM, Hoffmann A, Mamisch-Saupe N, Espinosa N, Resnick D, Hodler J. Hindfoot alignment measurements: rotation-stability of measurement techniques on hindfoot

alignment view and long axial view radiographs. AJR Am J Roentgenol. 2011;197(3):578-582. 3. Chan JY, Williams BR, Nair P, et al. The contribution of medializing calcaneal osteotomy on hindfoot alignment in the reconstruction of the stage II adult acquired flatfoot deformity. Foot Ankle Int. 2013;34(2):159-166. 4. Deland JT. Adult-acquired flatfoot deformity. J Am Acad Orthop Surg. 2008;16(7):399-406. 5. Donovan A, Rosenberg ZS. Extraarticular lateral hindfoot impingement with posterior tibial tendon tear: MRI correlation. AJR Am J Roentgenol. 2009;193(3):672-678. 6. Ellis SJ, Yu JC, Williams BR, Lee C, Chiu YL, Deland JT. New radiographic parameters assessing forefoot abduction in the adult acquired flatfoot deformity. Foot Ankle Int. 2009;30(12):1168-1176. 7. Hirschmann A, Pfirrmann CW, Klammer G, Espinosa N, Buck FM. Upright cone CT of the hindfoot: comparison of the non-weight-bearing with the upright weight-bearing position. Eur Radiol. 2014;24(3):553-558. 8. Johnson JE, Lamdan R, Granberry WF, Harris GF, Carrera GF. Hindfoot coronal alignment: a modified radiographic method. Foot Ankle Int. 1999;20(12):818-825. 9. Lee MS, Vanore JV, Thomas JL, et al; Clinical Practice Guideline Adult Flatfoot Panel. Diagnosis and treatment of adult flatfoot. J Foot Ankle Surg. 2005;44(2):78-113. 10. Myerson MS, Badekas A, Schon LC. Treatment of stage II posterior tibial tendon deficiency with flexor digitorum longus tendon transfer and calcaneal osteotomy. Foot Ankle Int. 2004;25(7):445-450. 11. Reilingh ML, Beimers L, Tuijthof GJ, Stufkens SA, Maas M, van Dijk CN. Measuring hindfoot alignment radiographically: the long axial view is more reliable than the hindfoot alignment view. Skeletal Radiol. 2010;39(11):1103-1108. 12. Robinson I, Dyson R, Halson-Brown S. Reliability of clinical and radiographic measurement of rearfoot alignment in a patient population. Foot. 2001;11(1):2-9. 13. Saltzman CL, el-Khoury GY. The hindfoot alignment view. Foot Ankle Int. 1995;16(9):572-576. 14. Younger AS, Sawatzky B, Dryden P. Radiographic assessment of adult flatfoot. Foot Ankle Int. 2005;26(10):820-825.

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New radiographic parameter assessing hindfoot alignment in stage II adult-acquired flatfoot deformity.

The hindfoot moment arm is a reliable measurement of hindfoot valgus deformity in stage II adult-acquired flatfoot deformity (AAFD) and can be used to...
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