762113
research-article2018
FAIXXX10.1177/1071100718762113Foot & Ankle Internationalde Cesar Netto et al
Article
Correlation of Clinical Evaluation and Radiographic Hindfoot Alignment in Stage II Adult-Acquired Flatfoot Deformity
Foot & Ankle International® 1–9 © The Author(s) 2018 Reprints and permissions: sagepub.com/journalsPermissions.nav https://doi.org/10.1177/1071100718762113 DOI: 10.1177/1071100718762113 journals.sagepub.com/home/fai
Cesar de Cesar Netto, MD, PhD1 , Grace C. Kunas, BA1, Dylan Soukup, BS1, Anca Marinescu, BA1, and Scott J. Ellis, MD1
Abstract Background: Previous work has demonstrated that the amount of radiographic hindfoot correction required at the time of adult-acquired flatfoot deformity (AAFD) operative treatment can be predicted by the amount of radiographic deformity present before surgery. Successful outcomes after reconstruction are closely correlated with hindfoot valgus correction. However, it is not clear if differences exist between clinical and radiographic assessment of hindfoot valgus. The purpose of this study was to evaluate the correlation between radiographic and clinical evaluation of hindfoot alignment in patients with stage II AAFD. Methods: Twenty-nine patients (30 feet) with stage II AAFD, 17 men and 12 women, mean age of 51 (range, 20-71) years, were prospectively recruited. In a controlled and standardized fashion, bilateral weightbearing radiographic hindfoot alignment views were taken. Radiographic parameters were measured by 2 blinded and independent readers: hindfoot alignment angle (HAA) and hindfoot moment arm (HMA). Clinical photographs of hindfoot alignment were taken in 3 different vertical camera angulations (0, 20, and 40 degrees). Pictures were assessed by the same readers for standing tibiocalcaneal angle (STCA) and resting calcaneal stance position (RCSP). Intra- and interobserver reliability were assessed by Pearson/Spearman’s and intraclass correlation coefficient (ICC), respectively. Relationship between clinical and radiographic hindfoot alignment was evaluated by a linear regression model. Comparison between the different angles (RCSP, STCA, and HAA) was performed using the Wilcoxon rank-sum test. P values of less than .05 were considered significant. Results: We found overall almost perfect intraobserver (range, 0.91-0.99) and interobserver reliability (range, 0.740.98) for all measures. Mean value and confidence interval (CI) for RCSP and STCA were 10.8 degrees (CI, 10.1-11.5) and 12.6 degrees (CI, 11.7-13.4), respectively. The position of the camera did not influence readings of clinical alignment (P > .05). The mean HMA was 18.7 mm (CI, 16.3-21.1 mm), and the mean HAA was 23.5 degrees (CI, 21.1-26.0). Clinical and radiographic hindfoot alignment were found to significantly correlate (P < .05). However, the radiographic HAA demonstrated increased valgus compared to both clinical alignment measurements, with a mean difference of 12.8 degrees from the RCSP (CI, 11.0-14.5, P < .0001) and 11.0 degrees from the STCA (CI, 9.2-12.8, P < .0001). Conclusion: We found significant correlation between radiographic and clinical hindfoot alignment in patients with stage II AAFD. However, radiographic measurements of HAA demonstrated significantly more pronounced valgus alignment than the clinical evaluation. The results of our study suggest that clinical evaluation of hindfoot alignment in patients with AAFD potentially underestimates the bony valgus deformity. One should consider these findings when using clinical evaluation in the treatment algorithm of flatfoot patients. Level of Evidence: Level II, prospective comparative study. Keywords: adult-acquired flatfoot deformity, flatfoot, hindfoot alignment, hindfoot valgus, measurement reliability Adult-acquired flatfoot deformity (AAFD) occurs most commonly secondary to combined dysfunction of the posterior tibial tendon (PTT) and plantar ligaments of the foot. It is clinically characterized by symptomatic collapse of the medial longitudinal arch, forefoot abduction at the talonavicular joint, and hindfoot valgus.5,15,24 The evaluation of the hindfoot
1
Hospital for Special Surgery, New York, NY, USA
Corresponding Author: Scott J. Ellis, MD, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA. Email:
[email protected]
2 valgus alignment in patients with AAFD is part of the staging and operative planning of the disease5,21,22,28,29 and usually involves clinical and radiographic evaluation in the standing position.2,3 Different clinical and radiographic assessment modalities have been proposed in the literature.7,10,11,20,33 Clinical evaluation of hindfoot coronal alignment is performed through observation of surface landmarks, including the skin, the Achilles tendon, and bony prominences. It represents an attempt to predict the bone alignment of the hindfoot. It has been shown to be unreliable even when performed by experienced observers, with or without the use of goniometers.2,18,23,36 Radiographic assessment can potentially better demonstrate the true bone alignment of the hindfoot. However, measurement of radiographic parameters of the foot and ankle on conventional radiographs is significantly influenced by misalignment, overlapping and enlargement of bone structures due to the projectional nature of the images.4,32,37 Controlling for correct and reliable positioning of the foot and ankle during acquisition of the images represents a challenge and an important limitation of any radiographic measurement studies.32 Williamson et al38 proposed a new radiographic parameter in the assessment of hindfoot alignment of patients with stage II AAFD. The hindfoot alignment angle (HAA) takes into consideration specific bony anatomical landmarks to define the axis of the calcaneus, including the lateral wall of the calcaneal tuberosity laterally and the sustentaculum tali medially. The landmarks are easily assessed and optimize the intraobserver and interobserver reliability of the measurement. The authors also demonstrated that the HAA represented an adequate tool in the differentiation between flatfoot and normal patients and that the angle correlated significantly with the hindfoot moment arm, as described by Saltzman and el-Khoury.33 Successful clinical outcomes after AAFD reconstruction are closely correlated with adequate hindfoot valgus correction.9,13 However, it is not clear if differences exist between clinical and radiographic assessment of hindfoot valgus.35 The development of standardized clinical and radiographic measurement tools to optimize the evaluation of hindfoot alignment would allow more accurate assessment of treatment outcomes. The purpose of this study was to assess whether in a controlled and prospective evaluation, accounting for standardized positioning of the lower extremity, there would be significant correlation between clinical and radiographic hindfoot alignment measurements, using the HAA, in patients with stage II AAFD.
Methods Institutional review board approval was obtained for this prospective comparative study, which complied with the Declaration of Helsinki and the Health Insurance Portability
Foot & Ankle International 00(0) and Accountability Act (HIPAA). All participants signed a written informed consent.
Study Design We prospectively recruited consecutive patients from February 2015 through October 2015. The inclusion criteria consisted of a clinical diagnosis of symptomatic stage II AAFD, indication for operative treatment, an age of 18 years or older, the ability to communicate effectively with clinical study personnel, and the ability to stand still for acquisition of weightbearing clinical pictures and radiographic studies. We excluded patients with major arthritic findings in the subtalar, talonavicular, and/or calcaneocuboid joints; pregnant women; patients with prior operative procedures in the affected foot and ankle; and patients with clinical pictures and/or radiographic studies that did not fulfill necessary quality for assessment.
Patients Twenty-nine patients (30 feet, 12 right side and 18 left side) were included in the study. The cohort consisted of 17 men and 12 women, with a mean age of 51 years (range, 20-71 years) and a mean body mass index (BMI) of 28.6 kg/m2 (range, 21.137.8 kg/m2). A CONSORT diagram of screened, excluded, and included patients is presented in Figure 1.
Clinical Evaluation All patients were clinically evaluated and diagnosed with stage II AAFD. A series of clinical photographs were taken. Patients were instructed to stand in a comfortable natural stance position, facing away from the camera and with hands hanging by the side of the body. The feet were maintained shoulder-width apart with relaxed longitudinal arches. The medial border of each foot was positioned over 2 parallel lines that were drawn into the floor, controlling for rotational misalignment. With the medial aspect of the back of the heels along the predefined lines, the camera was positioned at a distance of 110 cm from the foot (110 cm heel-to-lens distance), to mimic the distance used in the patient positioning during acquisition of the radiographic images, and was horizontally centered in the midline of the body. The camera was then adjusted to 3 clinically relevant vertical angles representing the positioning of the feet in the floor level (0 degrees), the same angulation used for a Saltzman radiographic view (20 degrees), and a comfortable positioning for a clinician to be seated observing the hindfoot alignment (40 degrees) (Figure 2): •• Ground-level view: camera positioned at ground level, with 0 degrees of vertical angulation
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Figure 1. CONSORT diagram demonstrating screened, excluded, and included patients.
Figure 2. Hindfoot alignment clinical pictures with 3 different vertical camera angulations: ground level or 0 degrees (A), Saltzman view level or 20 degrees (B), and seated observer level or 40 degrees (C).
•• Simulated Saltzman hindfoot alignment view: camera positioned 40 cm off ground, vertically centered on the ankle joint (distal tilt of 20 degrees) •• Seated physician view: camera positioned 92 cm off ground, vertically centered on the ankles (distal tilt of 40 degrees)
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From each photo, 2 clinical hindfoot alignment measurements were performed (Figure 3): 18
•• Standing tibiocalcaneal angle (STCA) cc
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Lines 1 and 2: 2 lines parallel to the floor, connecting the medial and lateral edges of the leg, were drawn. Line 1 was positioned halfway between the knee and medial malleolus and line 2 halfway between line 1 and the medial malleolus. Line 3: the perpendicular bisector of lines 1 and 2 was marked.
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Line 4: a line connecting the most medial aspect of the medial malleolus to the most lateral aspect of the lateral malleolus was drawn. Line 5: a line parallel to the floor connecting the medial and lateral borders of the lowest discernable level of the heel was marked. Line 6: a line connecting the midpoints of lines 4 and 5 was drawn. STCA measurement: angle between lines 3 and 6.
•• Resting calcaneal stance position (RCSP)17,25 cc
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Line 1: a line perpendicular to the floor was drawn. Line 2: a line connecting the most medial aspect of the medial malleolus to the most lateral aspect of the lateral malleolus was marked. Line 3: a line parallel to the floor connecting the medial and lateral borders of the lowest discernable level of the heel was marked.
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Figure 3. Examples of clinical hindfoot alignment measurements. Standing tibiocalcaneal angle (STCA), represented by angle α (A), and resting calcaneal stance position (RCSP), represented by angle β (B).
Figure 4. Examples of radiographic hindfoot alignment measurements. Hindfoot alignment angle (HAA), represented by angle α (A), and hindfoot moment arm (HMA) (B). cc
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Line 4: a line connecting the midpoints of lines 2 and 3 was drawn. RCSP measurement: angle between lines 1 and 4.
•• HAA, as described by Williamson et al38: cc
Radiographic Evaluation All patients had a hindfoot alignment view obtained,33 with the x-ray beam pointed 20 degrees down, centered on the ankles, and the film positioned perpendicular to beam. The same 2 parallel lines used for clinical alignment evaluation were used during acquisition of radiographic images. The medial border of each foot was positioned over the lines to control for rotational misalignment. From each image, 2 hindfoot alignment measurements were performed (Figure 4):
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Tibial axis line was marked using a perpendicular bisector of the width of the tibial shaft at 2 different levels, 100 mm and 150 mm proximal to the tibial plafond. The calcaneal axis was determined by the bisecting line of the angle formed by 2 lines representing the lateral and medial osseous contours of the calcaneus. The line for the lateral osseous contour was drawn between the most lateral aspect of the lateral process on the calcaneal tuberosity and the most superior and lateral discernable aspect of the calcaneus. The line for the medial osseous contour was drawn from the most medial
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Table 1. Mean Value (Degrees) and Standard Deviation for Both Standing Tibiocalcaneal Angle (STCA) and Resting Calcaneal Stance Position (RCSP) Measured in Different Vertical Camera Angulations (0, 20, and 40 Degrees). Vertical Camera Angulation Clinical Hindfoot Alignment
0 Degrees
20 Degrees
40 Degrees
P Value
RCSP STCA
11.5 ± 4.2 12.4 ± 5.0
10.8 ± 4.5 12.4 ± 5.4
10.2 ± 5.2 12.6 ± 6.7
.09 .92
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aspect of the medial process of the calcaneal tuberosity to the most inferomedial discernable aspect of the sustentaculum tali. The HAA was defined as the angle between the tibial axis and calcaneal axis lines.
•• Hindfoot moment arm (HMA), as described by Saltzman and el-Khoury33: cc cc
Tibial axis was drawn as previously described. The HMA was defined as the distance connecting the most inferior aspect of the calcaneus to the tibial axis line.
Measurements Radiographic and clinical pictures were transferred digitally into dedicated software (ImageJ; National Institutes of Health, Bethesda, MD) for computer-based measurements. Image annotations were removed, and each study was assigned a unique and random number. After completion of a mentored training protocol, to learn how to use the software and how to perform the measurements, 2 readers performed all measurements in an independent, random, and blinded fashion. For assessment of intraobserver reliability, both observers performed a second set of measurements 1 month after the first assessment was completed, minimizing the memory bias.
Statistical Analysis Data analysis was performed with JMP Pro version 12.2.0 (SAS Institute, Marlow-Buckinghamshire, UK). Data from each type of measurement were initially evaluated for normality with the Shapiro-Wilk W test. The intraobserver reliability for both readers was calculated using the Pearson or Spearman correlation test and 95% confidence interval (CI). Interobserver reliability was assessed using the intraclass correlation coefficient (ICC), with consideration of the amount by which bias and interaction factors can reduce the ICC. Correlations of 0.81 to 0.99 were considered almost perfect; 0.61 to 0.80, substantial; 0.41 to 0.60, moderate; 0.21 to 0.40, fair; and slight if equal or inferior to 0.20.14,26 A linear regression model was used to assess the relationship between clinical and radiographic hindfoot
alignment. Comparison between the different angles (RCSP, STCA, and HAA) was performed using Wilcoxon ranksum test and nonparametric comparison for each pair by the Wilcoxon method. P values of less than .05 were considered significant.
Results Data for both clinical measurements were found to follow a nonnormal distribution in the Shapiro-Wilk W test (P < .05). Radiographic measurements followed a normal distribution using the same statistical method (P > .05). The intraobserver agreement was almost perfect for STCA (Spearman’s P = .93; CI, 0.90-0.95), RCSP (Spearman’s P = .91; CI, 0.88-0.94), HMA (Pearson’s r = 0.99; CI, 0.97-0.99), and HAA (Pearson’s r = 0.95; CI, 0.89-0.97). The interobserver agreement for clinical alignment measurements was almost perfect for STCA (ICC = 0.86) and substantial for RCSP (ICC = 0.74). Almost perfect agreement was also found for radiographic alignment measurements HMA (ICC = 0.98) and HAA (ICC = 0.94). The mean values and CIs for the RCSP and STCA were respectively 10.8 degrees (CI, 10.1-11.5) and 12.6 degrees (CI, 11.7-13.4). Mean value and standard deviation for both STCA and RCSP, measured in different vertical camera angulations, are presented in Table 1. The position of the camera in 0, 20, and 40 degrees of vertical angulation did not significantly influence readings of clinical hindfoot alignment (P > .05). Regarding radiographic alignment, the mean HMA was 18.7 mm (CI, 16.3-21.1 mm), and the mean HAA was 23.5 degrees (CI, 21.1-26.0). Significant correlation (P < .05) was found when comparing clinical hindfoot alignment, for both STCA and RCSP, and radiographic hindfoot alignment (HMA and HAA), in all different vertical camera angulations (0, 20, and 40 degrees). R2, intercept, and P values are presented in Table 2. However, when comparing RCSP, STCA, and HAA, significant differences were found between the groups (P < .0001) (Figure 5). The radiographic HAA was found to be significantly more valgus compared to both clinical alignment measurements, with a mean difference of 12.8 degrees
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Table 2. R2, Parameter Estimate, Intercept, and P Values for Linear Regression Models Evaluating the Correlation Between Clinical Hindfoot Alignment (in 3 Different Vertical Camera Angulations of 0, 20, and 40 Degrees) and Radiographic Hindfoot Alignment. Hindfoot Moment Arm Clinical Hindfoot Resting calcaneal stance position 0 degrees 20 degrees 40 degrees Standing tibiocalcaneal angle 0 degrees 20 degrees 40 degrees
Hindfoot Alignment Angle
R2
Parameter Estimate
Intercept
P Value
R2
Parameter Estimate
Intercept
0.1 0.1 0.1
0.7 0.8 0.7
11.1 10.5 11.9
.02a .002a .003a
0.1 0.2 0.2
0.8 0.9 0.8
14.6 14.3 15.8
0.1 0.1 0.1
0.7 0.6 0.4
10.3 10.8 13.8
.006a .003a .02a
0.2 0.2 0.2
0.9 0.8 0.6
12.3 13.0 16.3
P Value .007a .001a .00090a .0002a
