• View in gallery

    Procedure to determine the bunion angle. A, Draw a line along the edge of the great toe. B, Draw a line along the medial edge of the forefoot. C, Use the ‘angle' function in Kinovea software to measure the angle between the two lines.

  • 1. 

    Sutherland JM, Mok J & Liu G: Cost-utility study of the economics of bunion correction surgery. Foot Ankle Int 40: 336, 2019.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 2. 

    Sutherland JM, Wing K & Penner M: Quantifying patient-reported disability and health while waiting for bunion surgery. Foot Ankle Int 39: 1047, 2018.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 3. 

    Coughlin MJ & Jones CP: Hallux valgus: demographics, etiology, and radiographic assessment. Foot Ankle Int 28: 759, 2007.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 4. 

    Menz HB & Lord SR: Gait instability in older people with hallux valgus. Foot Ankle Int 26: 483, 2005.

  • 5. 

    Everhart JS: Hallux valgus correction: the best technique is still up for debate: commentary on an article by Alexej Barg, MD, et al: ‘Unfavorable outcomes following surgical treatment of hallux valgus deformity. A systematic literature review.' J Bone Joint Surg Am 100: e124, 2018.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. 

    Lee SY, Chung CY & Park MS: Radiographic measurements associated with the natural progression of the hallux valgus during at least 2 years of follow-up. Foot Ankle Int 39: 463, 2018.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 7. 

    Ortiz C, Wagner P & Vela O et al.: “Angle to be corrected” in preoperative evaluation for hallux valgus surgery. Foot Ankle Int 37: 172, 2016.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 8. 

    Heineman N, Xi Y & Zhang L: Hallux valgus evaluation on MRI: can measurements validated on radiographs be used? J Foot Ankle Surg 57: 305, 2018.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 9. 

    Nix S, Russell T & Vicenzino B et al.: Validity and reliability of hallux valgus angle measured on digital photographs. J Orthop Sport Phys Ther 42: 642, 2012.

    • Crossref
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 10. 

    Garrow AP, Papageorgiou A & Silman AJ et al.: The grading of hallux valgus: the Manchester Scale. JAPMA 91: 74, 2001.

  • 11. 

    Menz HB & Munteanu SE: Radiographic validation of the Manchester scale for the classification of hallux valgus deformity. Rheumatology 44: 1061, 2005.

  • 12. 

    Menz HB, Fotoohabadi MR & Wee E et al.: Validity of self-assessment of hallux valgus using the Manchester scale. BMC Musculoskelet Disord 11: 215, 2010.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 13. 

    Klein C, Kinz W & Zembsch A et al.: The hallux valgus angle of the margo medialis pedis as an alternative to the measurement of the metatarsophalangeal hallux valgus angle. BMC Musculoskelet Disord 15: 133, 2014.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 14. 

    Yamaguchi S, Sadamasu A & Kimura S et al.: Nonradiographic measurement of hallux valgus angle using self-photography. J Orthop Sports PhysTher 49: 80, 2019.

  • 15. 

    Shah A, Rowlands M & Patel A et al.: Ubersense: using a free video analysis app to evaluate and improve microsurgical skills. Plast Reconstr Surg 134: 338e, 2014.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 16. 

    Weiler R: Übersense coach app for sport medicine? slow motion video analysis (mobile app user guide). Br J Sports Med 50: 255, 2016.

  • 17. 

    Faber FWM, Kleinrensink GJ & Mulder PGH et al.: Mobility of the first tarsometatarsal joint in hallux valgus patients: a radiographic analysis. Foot Ankle Int 22: 965, 2001.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18. 

    Nix S, Smith M & Vicenzino B: Prevalence of hallux valgus in the general population: a systematic review and meta-analysis. J Foot Ankle Res 3: 21, 2010.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 19. 

    Haley SM & Fragala-Pinkham MA: Interpreting change scores of tests and measures used in physical therapy. Phys Ther 86: 735, 2006.

  • 20. 

    Singh G: Determination of cutoff score for a diagnostic test. Internet J Lab Med 2: 4, 2006.

  • 21. 

    Nixon DC, McCormick JJ & Johnson JE et al.: PROMIS pain interference and physical function scores correlate with the foot and ankle ability measure (FAAM) in patients with hallux valgus. Clin Orthop Relat Res 475: 2775, 2017.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation

A Clinician-Free Method Using Top-View Photography for Screening and Monitoring Hallux Valgus

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Background

Hallux valgus is a progressive foot deformity that commonly affects middle-aged women. The aim of this study was to develop a novel method using only top-view photographs to assess hallux valgus severity.

Methods

A top-view digital photograph was taken of each foot of 70 female participants. Two straight lines were drawn along the medial edge of the great toe and forefoot, and the included angle (termed bunion angle) was measured using a free software program. Each foot was also assessed by a clinician using the Manchester scale as no (grade 1), mild (grade 2), moderate (grade 3), or severe (grade 4) deformity.

Results

The mean bunion angles of the 140 feet were 6.7°, 13.5°, and 16.2° for Manchester grades 1, 2, and 3, respectively (no foot was in grade 4). The reliability was excellent for both intrarater (intraclass correlation coefficient [ICC] = 0.93–0.95) and interrater (ICC = 0.90) assessments. Receiver operating characteristic curves determined the optimal bunion angle cutoff value for screening hallux valgus to be 9°, which gives 89.2% sensitivity and 74.2% specificity.

Conclusions

The bunion angle is a reliable, clinician-free method that can potentially be integrated into a smartphone app for easy and inexpensive self-assessment of hallux valgus.

Background

Hallux valgus is a progressive foot deformity that commonly affects middle-aged women. The aim of this study was to develop a novel method using only top-view photographs to assess hallux valgus severity.

Methods

A top-view digital photograph was taken of each foot of 70 female participants. Two straight lines were drawn along the medial edge of the great toe and forefoot, and the included angle (termed bunion angle) was measured using a free software program. Each foot was also assessed by a clinician using the Manchester scale as no (grade 1), mild (grade 2), moderate (grade 3), or severe (grade 4) deformity.

Results

The mean bunion angles of the 140 feet were 6.7°, 13.5°, and 16.2° for Manchester grades 1, 2, and 3, respectively (no foot was in grade 4). The reliability was excellent for both intrarater (intraclass correlation coefficient [ICC] = 0.93–0.95) and interrater (ICC = 0.90) assessments. Receiver operating characteristic curves determined the optimal bunion angle cutoff value for screening hallux valgus to be 9°, which gives 89.2% sensitivity and 74.2% specificity.

Conclusions

The bunion angle is a reliable, clinician-free method that can potentially be integrated into a smartphone app for easy and inexpensive self-assessment of hallux valgus.

Hallux valgus, also referred to as bunion, is a common foot deformity affecting the great toe that is characterized by lateral deviation of the hallux and medial deviation of the first metatarsal.1-6 The severity of hallux valgus can be quantified from radiographic or magnetic resonance images by measuring the hallux angle and sometimes also the intermetatarsal angle.7,8 Nix and colleagues9 developed a method that does not require medical imaging and uses only photographs to measure the hallux angle with good validity and reliability. However, their method requires visual determination of the bisection points of specific bones and, therefore, is not practical for use by those without good knowledge of foot anatomy and clinical experience. Garrow and colleagues10 developed the Manchester scale to visually compare and grade the severity of hallux valgus into four categories (grade 1: no deformity, grade 2: mild deformity, grade 3: moderate deformity, grade 4: severe deformity). Although the reliability of the Manchester scale is high11 and can be used for self-assessing,12 this method has reduced continuous data to categorical data and, therefore, may not be ideal for clinics that are collecting and monitoring quantifiable indicators. Klein and colleagues13 proposed a method to quantify the hallux angle between a line joining the ball of the great toe to the most medial side of the great toe and the margo medialis pedis line along the medial border of the foot from the heel to the ball of the great toe. This new measurement of the hallux angle is approximately 4.8° systematically smaller than radiographic methods and can be used as a conservative estimate. Similarly, Yamaguchi and colleagues14 compared the hallux angle measured using self-photography versus radiography and reported a systematic 5° error. In these earlier studies,13,14 we believe that the position of the medial heel or the border of the foot is a lot more medial than the first metatarsal bone observed in radiographic images. Thus, it is unavoidable that the medial border of the foot will always make an angle with the longitudinal axis of the first metatarsal, reducing the hallux valgus measurement value systematically.

For a tool to be useful for screening and home monitoring, it should be easily accessible, inexpensive, and preferably self-administered. The photographic method developed by Nix and colleagues9 requires the image to be taken from a specific position (15° from the vertical, at a distance of 100 cm), which is rather difficult to replicate when one takes photographs of his or her own foot using a smartphone. The method by Klein et al13 may be inconvenient because a metal strip is always required to indicate the line projecting from the medial heel to the ball of the great toe. To facilitate mass screening by mapping hallux valgus angles from a photograph into an algorithm using a smartphone app, new approaches using top-view photographs of the foot without strict requirements of camera position or extra tools will be beneficial.

The aim of the present study was to develop a novel method using only top-view photographs to assess hallux valgus severity. To avoid confusion with the hallux valgus angle measured from radiographs in previous studies, we use the new term bunion angle to indicate the angle between two lines on the medial border of the first proximal phalange and the first metatarsal. We hypothesize that the method has good intrarater and interrater reliability, with an intraclass correlation coefficient (ICC) greater than 0.85. If the hypothesis is confirmed, bunion angle evaluation can be combined with a free video analysis app in the future.15,16 Potential applications of the bunion angle include facilitating health-care professionals to assess patients in primary care, providing a quick and easy screening tool in the community, and allowing self-assessment by patients and caregivers at home.

Materials and Methods

Participants

This study was part of a larger-scale study on clinical foot assessment approved by the SingHealth Centralised Institutional Review Board (Singapore). All of the methods were performed in accordance with the relevant guidelines and regulations. The work was performed at Singapore General Hospital, Singapore. Sample size was calculated with an effect size of d = 0.71 as determined from a study of first-ray range of motion in patients with hallux valgus using radiography.17 With α = 0.05 and power = 0.80, 64 participants are needed for the 2-tailed independent t test. Seventy women (mean ± SD: age, 30.3 ± 7.7 years; height, 160.0 ± 6.1 cm; body mass, 57.7 ± 11.3 kg) provided written informed consent to participate during the study period (February to June 2018). The exclusion criteria were 1) any foot injury that resulted in 7 days or more of rest in the past 6 months, 2) previous foot surgery, 3) any rheumatic or connective tissue conditions, or 4) pregnancy. We targeted only female participants because hallux valgus deformity is more prevalent in women.18

Procedures

The participants were instructed to stand naturally with their body weight equally distributed. Both feet were evaluated with the Manchester scale by a qualified podiatric physician (M.L.H.) with 9 years of clinical experience.10 A top-view unilateral digital photograph was obtained for each foot by a podiatric physician (Fig. 1). This type of digital photograph is not a form of specialized clinical imaging but a common photograph that anyone can take using a digital camera or mobile device. All of the digital photographs were captured by a Canon digital camera (PowerShot 2500; Canon Inc, Tokyo, Japan) and saved in JPEG format (4,608 × 3,456 pixels). Digital photographs of 140 feet (70 left and 70 right) were analyzed in a randomized order by two independent assessors (J.W.P. and Y.Y.L.) with no formal clinical training. Each assessor measured the bunion angles on two occasions, at least 1 week apart, using free software (Kinovea, Version 0.8.15, available for download at http://www.kinovea.org). To quantify the bunion angle, two lines were drawn by manually inserting straight lines in the Kinovea software. The first line was drawn along the edge of the great toe, and the second line along the medial edge of the forefoot. The bunion angle was measured as the angle between the two lines (Fig. 1).

Figure 1.
Figure 1.

Procedure to determine the bunion angle. A, Draw a line along the edge of the great toe. B, Draw a line along the medial edge of the forefoot. C, Use the ‘angle' function in Kinovea software to measure the angle between the two lines.

Citation: Journal of the American Podiatric Medical Association 111, 5; 10.7547/19-167

Statistical Analysis

Intrarater reliability for each assessor (first and second measurement sets) and interrater reliability (first measurement set of each assessor) were tested using ICCs (ICC[2,1] and ICC[2,2]) using IBM SPSS Statistics for Windows, Version 24.0 (IBM Corp, Armonk, New York). Similar to previous work on hallux valgus angle reliability,9 the standard error of measurement (SEM) and minimal detectable change (MDC) at the 90% confidence interval (CI) were calculated from the ICC results using the following formulas: and . We decided to use the MDC at the 90% CI because this level seems to be the most common standard used in the literature regarding physical therapy.19

The mean ± SD bunion angle measured by one assessor (M.L.H.) for each of the four grades in the Manchester scale are reported. Analysis of variance was conducted to show the effect of Manchester grading on bunion angle. If a significant grade effect was found, post hoc t tests were conducted for pairwise comparison. Statistical significance was set at P = .05 level.

To determine a cutoff value of the bunion angle for screening purposes, a receiver operating characteristic curve was used20 to determine how well the test performs at selected cutoff values at every 0.5° between the mean bunion angle values of Manchester grades 1 and 2. For each selected cutoff value, sensitivity, which is the percentage of cases (Manchester grades 2 and 3) being classified as cases by the bunion angle value, and specificity, which is the percentage of noncases (Manchester grade 1) being classified as noncases by the bunion angle value, were reported. We started from the lowest selected cutoff values with the highest sensitivity and moved forward to higher cutoff values until the gained specificity value did not outweigh the reduced sensitivity anymore.

Results

Bunion Angle

The 140 feet showed various degrees of deformity as measured by bunion angles and graded using the Manchester scale (Table 1). No foot was assessed as grade 4 (severe deformity). Analysis of variance reveals a significant effect of Manchester grading on bunion angle (P < .001), and post hoc t tests revealed that the bunion angles in grade 2 (ie, 13.5°) and grade 3 (ie, 16.2°) were significantly greater than that in grade 1 (ie, 6.7°) (P < .001). Among individuals with mild-to-moderate deformity, with the numbers available, no significant difference could be detected between grades 2 and 3 (P = .375).

Table 1.

Number of Feet and Bunion Angle by Manchester Grade

Table 1.

Reliability

For intrarater reliability of two sets of measurements, the ICC[2,1] values were 0.93 (95% CI, 0.91–0.95) for assessor 1 and 0.95 (95% CI, 0.94–0.97) for assessor 2. The corresponding values for SEM were 3.6° and 2.4°, and for MDC were 8.7° and 5.6°. Between the two independent assessors, the ICC[2,2] for interrater reliability was 0.90 (95% CI, 0.83–0.93), and the corresponding values for SEM and MDC were 4.0° and 9.4°, respectively. Because all of the ICC values are greater than 0.85, we accepted the hypothesis that the method has good intrarater and interrater reliability.

Cutoff Value

Table 2 shows the sensitivity and specificity of the new test with different cutoff values. Based on the receiver operating characteristic curve, a cutoff value of 9° was selected for screening purposes, as moving this up to 9.5° gained only 4.6% in specificity, which did not outweigh the loss of sensitivity, which was 5.4%.

Table 2.

Sensitivity and Specificity of the New Test with Different Cutoff Values

Table 2.

Discussion

In this study, we established a clinician-free method using only top-view photographs for screening and monitoring hallux valgus severity with a new quantity bunion angle. This new method requires only simple procedures using free software to draw two lines on a photograph to measure the included angle, and it can be performed by anyone with minimal training and little anatomical knowledge. In the future, the method developed in the present study can be combined with a free video analysis app such as Ubersense15,16 for quick and easy assessment. The cost is low and almost free for individuals who have access to a smartphone with a photograph-taking function and installed with a free video analysis app.14 Theoretically, a lay person can perform a self-check to monitor the severity of hallux valgus anywhere at their own convenient time, reducing the burden on the health-care system in terms of manpower cost and the number of radiographs required.

In clinical practice, surgeons tend to assess hallux valgus severity radiographically as angles, and nonsurgical podiatric physicians tend to use the Manchester categorial grading. The severity of hallux valgus is most often quantified by the hallux angle, which is the angle between the longitudinal axis of the first metatarsal and that of the first proximal phalanx, and sometimes also the intermetatarsal angle, which is the angle between the first and second metatarsal shaft.7 The bunion angle presented herein can serve as a common measurement for foot health professionals to assess and communicate with one another and with their patients. It is not our intention for the bunion angle to replace radiologic assessment. Instead, the bunion angle is a simple assessment tool at an early stage to aid referral to secondary care. Furthermore, there are clinics without direct access to radiography services and podiatric physicians who do not have access to order radiographs. Hence, the bunion angle method, which does not depend on radiography, may facilitate the communication between foot and ankle surgeons and podiatric physicians.

Based on the data presented in this study, we propose the reference range of the bunion angle to be within 9° as measured by this newly proposed method. However, this bunion angle value has to be interpreted with care because it is not the same as the hallux valgus angle measured based on the bony alignments as shown in radiographs. Using the Manchester scale10 to measure and grade the severity of hallux valgus, Menz and Munteanu11 reported that the hallux abductus angles measured from radiographs were approximately 11° (grade 1), 17° (grade 2), 25° (grade 3), and 40° (grade 4). When interpreted clinically, care should be taken to consider the medial bulge of the abductor hallucis muscle when assessing the severity of the bunion angle.

The bunion angle method developed in this study is highly reliable and can successfully differentiate between individuals with (grades 2 and 3) and without (grade 1) hallux valgus deformity. This method, however, cannot clearly distinguish the subtle differences associated with various degrees of severity from grade 2 (mild) to grade 3 (moderate). Perhaps one of the reasons contributing to measurement error of the bunion angle could be the prominence of the abductor hallucis muscle (the muscle medial to the arch region). If this foot muscle is very prominent (especially in patients with flat feet), it can distort the medial aspect of the foot (ie, cause the medial edge of the forefoot to appear more medial than the actual shaft of the first metatarsal) and, therefore, underestimate the bunion angle.

As a starting point, this study recruited only female participants because hallux valgus deformity is more prevalent in women.18 Because good reliability has been demonstrated, the next step is to extend data collection to other populations, including men, children, and individuals with progressive foot deformities (eg, patients with rheumatoid arthritis or diabetes mellitus). In this study, we did not plan to include radiographic measurements to avoid unnecessary radioactive exposure to the participants. Because we have now shown high intrarater and interrater reliability, future studies can validate these bunion angle measurements with conventional hallux valgus angle measured with radiographs on a limited number of participants. The sample size will be calculated from the data obtained from this study. We expect that there will be a systematic difference between the bunion angle and the hallux valgus angle, but this difference could be smaller than the 4.8° reported by Klein et al13 and the 5° reported by Yamaguchi et al.14 In these two previous studies, the position of the medial heel or border of the foot is much more medial than the first metatarsal bone observed on radiographic images. Thus, it is unavoidable that the medial border of the foot will always make an angle with the longitudinal axis of the first metatarsal, reducing the hallux valgus measurement value systematically. In the present study, the line drawn along the medial edge of the forefoot is more parallel to the longitudinal axis of the first metatarsal, thus providing a better estimate of the hallux valgus angle as measured on radiography. The present study serves as the initial step to explore the use of bunion angle in quantifying hallux valgus severity. Further studies are needed to correlate the bunion angle presented in this study with the radiologic angles, in particular, hallux valgus angles. From the radiograph, it might also be possible to determine an offset adjustment to remove the systematic difference between the bunion angle and the conventional hallux valgus angle.

The proposed bunion angle method can be integrated into a smartphone app for larger-scale and multicenter trials to obtain reference data for different populations. In a systematic review and meta-analysis, Nix and colleagues18 summarized that across many countries the prevalence of hallux valgus deformity consistently increases with age and is higher in females than in males. To guide clinical decision making, it will be useful to establish a large set of reference data across different age groups, sexes, and races. The new bunion angle method proposed herein will be ideal for population study because it is low cost, easy to implement, and does not expose individuals to radiation. A recent study21 reported that the pain and physical function scores measured by the Patient-Reported Outcome Measurement Information System (PROMIS) correlate well with the Foot and Ankle Ability Measure Activities of Daily Living score. PROMIS can be self-administrated, and, therefore, if this is incorporated into the bunion angle measurement method presented in this study, the new method can be used to monitor the progress of hallux valgus on not only first-ray alignment but also pain and physical function. Future work is warranted to develop an app once the effectiveness of bunion angle and other associated measures are established. Caution should be taken because patients may not use the app in an appropriate way, leading to anxiety and unnecessary referrals.

Finally, we presented the SWOT (strengths, weaknesses, opportunities, and threats) analysis of the new method described herein (Table 3). This method is suitable for self-monitoring at home and for primary care because it is inexpensive, easy to administer, and reliable. Compared with radiography and magnetic resonance imaging, measuring the bunion angle does not expose the individual to radiation and, therefore, can be a safe and useful tool for community screening at low medical and labor cost. Although the bunion angle can successfully differentiate between individuals with and without hallux valgus deformity, the present method cannot clearly distinguish the subtle differences between mild and moderate severity. Further development of this method via mobile phones and apps can potentially enhance public health screening and improve health management. As technology advances, there is also a possibility of causing paranoia if misused. We should also remain cautious not to use bunion angle as an alternative to medical imaging.

Table 3.

SWOT (Strengths, Weaknesses, Opportunities, and Threats) Analysis of the New Bunion Angle Method for Hallux Valgus Screening and Monitoring

Table 3.

Conclusions

This study developed a clinician-free method for measuring the bunion angle on top-view digital images by assessors with no clinical training. The key strengths of this new method include excellent intrarater and interrater reliability, successful differentiation between individuals with and without hallux valgus deformity, low cost, and safe without any need for clinical expertise or medical equipment. Given that the bunion angle provides a good estimate of the severity of hallux valgus, this method can potentially be integrated into a smartphone app for easy assessment of hallux valgus severity. This new method can facilitate assessment in primary care, can aid referral to secondary care, and is a simple tool for community screening and self-monitoring at home. The present study serves as the initial step to explore use of the bunion angle in quantifying hallux valgus severity. Further studies are needed to correlate the bunion angle with the radiologic angles and to determine an offset adjustment for removing the systematic difference between the bunion angle and the conventional hallux valgus angle.

Financial Disclosure: This research is supported by the Ministry of Education, Singapore, under its Academic Research Fund Tier 1 (2015-T1-002-052). Mr. Pan is supported by the China Scholarship Council.

References

  • 1. 

    Sutherland JM, Mok J & Liu G: Cost-utility study of the economics of bunion correction surgery. Foot Ankle Int 40: 336, 2019.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 2. 

    Sutherland JM, Wing K & Penner M: Quantifying patient-reported disability and health while waiting for bunion surgery. Foot Ankle Int 39: 1047, 2018.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 3. 

    Coughlin MJ & Jones CP: Hallux valgus: demographics, etiology, and radiographic assessment. Foot Ankle Int 28: 759, 2007.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 4. 

    Menz HB & Lord SR: Gait instability in older people with hallux valgus. Foot Ankle Int 26: 483, 2005.

  • 5. 

    Everhart JS: Hallux valgus correction: the best technique is still up for debate: commentary on an article by Alexej Barg, MD, et al: ‘Unfavorable outcomes following surgical treatment of hallux valgus deformity. A systematic literature review.' J Bone Joint Surg Am 100: e124, 2018.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. 

    Lee SY, Chung CY & Park MS: Radiographic measurements associated with the natural progression of the hallux valgus during at least 2 years of follow-up. Foot Ankle Int 39: 463, 2018.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 7. 

    Ortiz C, Wagner P & Vela O et al.: “Angle to be corrected” in preoperative evaluation for hallux valgus surgery. Foot Ankle Int 37: 172, 2016.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 8. 

    Heineman N, Xi Y & Zhang L: Hallux valgus evaluation on MRI: can measurements validated on radiographs be used? J Foot Ankle Surg 57: 305, 2018.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 9. 

    Nix S, Russell T & Vicenzino B et al.: Validity and reliability of hallux valgus angle measured on digital photographs. J Orthop Sport Phys Ther 42: 642, 2012.

    • Crossref
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 10. 

    Garrow AP, Papageorgiou A & Silman AJ et al.: The grading of hallux valgus: the Manchester Scale. JAPMA 91: 74, 2001.

  • 11. 

    Menz HB & Munteanu SE: Radiographic validation of the Manchester scale for the classification of hallux valgus deformity. Rheumatology 44: 1061, 2005.

  • 12. 

    Menz HB, Fotoohabadi MR & Wee E et al.: Validity of self-assessment of hallux valgus using the Manchester scale. BMC Musculoskelet Disord 11: 215, 2010.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 13. 

    Klein C, Kinz W & Zembsch A et al.: The hallux valgus angle of the margo medialis pedis as an alternative to the measurement of the metatarsophalangeal hallux valgus angle. BMC Musculoskelet Disord 15: 133, 2014.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 14. 

    Yamaguchi S, Sadamasu A & Kimura S et al.: Nonradiographic measurement of hallux valgus angle using self-photography. J Orthop Sports PhysTher 49: 80, 2019.

  • 15. 

    Shah A, Rowlands M & Patel A et al.: Ubersense: using a free video analysis app to evaluate and improve microsurgical skills. Plast Reconstr Surg 134: 338e, 2014.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 16. 

    Weiler R: Übersense coach app for sport medicine? slow motion video analysis (mobile app user guide). Br J Sports Med 50: 255, 2016.

  • 17. 

    Faber FWM, Kleinrensink GJ & Mulder PGH et al.: Mobility of the first tarsometatarsal joint in hallux valgus patients: a radiographic analysis. Foot Ankle Int 22: 965, 2001.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18. 

    Nix S, Smith M & Vicenzino B: Prevalence of hallux valgus in the general population: a systematic review and meta-analysis. J Foot Ankle Res 3: 21, 2010.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation
  • 19. 

    Haley SM & Fragala-Pinkham MA: Interpreting change scores of tests and measures used in physical therapy. Phys Ther 86: 735, 2006.

  • 20. 

    Singh G: Determination of cutoff score for a diagnostic test. Internet J Lab Med 2: 4, 2006.

  • 21. 

    Nixon DC, McCormick JJ & Johnson JE et al.: PROMIS pain interference and physical function scores correlate with the foot and ankle ability measure (FAAM) in patients with hallux valgus. Clin Orthop Relat Res 475: 2775, 2017.

    • Crossref
    • PubMed
    • Web of Science
    • Search Google Scholar
    • Export Citation

National Centre for Sport and Exercise Medicine, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, United Kingdom.

Podiatry Department, Singapore General Hospital, Singapore.

School of Health Sciences, University of South Australia, Adelaide, Australia.

Physical Education and Sports Science Academic Group, Nanyang Technological University, Singapore.

Private practice podiatric physician, Singapore.

Corresponding author: Pui Wah Kong, PhD, Physical Education and Sports Science Academic Group, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore. (E-mail: puiwah.kong@nie.edu.sg)

Conflict of Interest: None reported.