Inter- and intra-observer reliability of a smartphone application for measuring hallux valgus angles

doi:10.1016/j.fas.2012.08.004

Foot and Ankle Surgery

Volume 19, Issue 1, March 2013, Pages 18-21

https://doi.org/10.1016/j.fas.2012.08.004 Get rights and content

Abstract

Background

Measurement of radiological angles can be useful in the planning of the management of patients with hallux valgus. A smartphone application offers an alternative way of measuring these angles in a clinic setting. We compared the reliability (inter- and intra-observer) of this method to the use of PACS.

Methods

Radiographs of 30 feet from new patients referred with hallux valgus were examined and angles (HVA, IMA, and DMAA) recorded using the smartphone application and PACS.

Results

The smartphone application provided good inter-observer reliability for HVA and IMA (r = 0.93 and r = 0.79 respectively). Intra-observer reliability for HVA and IMA was also found to be good (r = 0.93–0.97 r = 0.82–0.93 respectively). The inter- and intra-observer reliability for using this method to measure DMAA fell below useful levels (r < 0.60 in each case).

Conclusions

This smartphone application provides a reliable method to measure HVA and IMA but we would not recommend it to measure DMAA.

Introduction

Various angles can be measured from foot radiographs. In the setting of hallux valgus, these angles may be used to guide appropriate management decisions and to measure postoperative outcomes. Commonly measured angles are the hallux valgus angle (HVA), intermetatarsal angle (IMA) and distal metatarsal articular angle (DMAA).

Traditionally, angles were assessed using a goniometer to measure incident angles between axes drawn on radiographs in marker pen. In the past few years, the use of computer workstations to view digital radiographs using picture archive and communication systems (PACS) has become widespread. Consequently, standard practice currently involves measuring angles using digital tools within the PACS software. Previous studies have validated digital measurements to be of equivalent or improved reliability to the traditional goniometer technique [1], [2], [3], [4]. More recently, an accelerometer-based angle measuring application (Hallux Angles App Version 1.0, Ockendon.net/WG Healthcare, October 2010) has been developed for the smartphone device. This software uses the inbuilt camera, accelerometer and display unit of the smartphone to allow the user to measure angles from either traditional or digitally displayed radiographs. It may represent a useful alternative to PACS software angle measurement, for situations in which PACS angle measuring tools are not available, or when the object radiographs are in hard copy rather than digitally displayed format.

This study assesses the reliability of the commonly used PACS software angle measuring lines and the newer accelerometer-based smartphone application for the measurement of angles from foot radiographs.

Section snippets

Objectives

The objective of this study was to compare the inter- and intra-observer reliability between computer-assisted measurements using PACS software, and an accelerometer-based smartphone application, for radiographic angles in hallux valgus (HVA, IMA and DMAA).

Study design

This observational study was conducted at South Devon Healthcare NHS Foundation Trust.

Selection of radiographs

Radiographs of thirty consecutive patients referred to our institute between January and March 2011 with a provisional diagnosis of hallux valgus were selected. Weight-bearing dorsoplantar foot views were taken using a standardised technique, with the beam centred on the midfoot and a 15° tilt of the X-ray tube towards the ankle. All patient identifying data was removed from radiographs, and radiographs were

Interobserver reliability

Intraclass correlation coefficients and 95% confidence intervals are shown in Table 1. For HVA and IMA measurements, excellent interobserver agreement was seen with both methods. Interobserver agreement was lower for measurement of DMAA using both techniques. For all angles there was a trend towards lower interobserver reliability when using the smartphone accelerometer angle measuring tool.

Intraobserver reliability

Intraclass correlation coefficients (ICC) and 95% confidence intervals are shown in Table 2. For HVA and

Discussion

Measuring a three-dimensional structure using two-dimensional images has inherent problems and these exist regardless of the tool used for measurement. In addition, error may be further compounded by poor image quality and image exposure. Despite this, radiographic angles are commonly used to guide decision making regarding appropriate management of hallux valgus. For example, a large HVA is unlikely to be fully corrected by a distal metatarsal osteotomy procedure. Therefore, a more proximal

Conclusions

This study provides independent non-manufacturer data that validate the smartphone hallux valgus angles application as a reliable tool for the measurement of HVA and IMA. DMAA measurements are less reliable and therefore not recommended. Use of the PACS measuring tool, where available, seems to be superior but this application provides comparable results and may be used in situations where hard-copies or imported images need to be assessed.

Conflict of interests

The authors have no conflicts to declare. None of the authors has any association with the designers of the smartphone application or WG Healthcare. No outside funding or support was provided for this work.

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There are more references available in the full text version of this article.

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Inter- and intra-observer reliability of a smartphone application for measuring hallux valgus angles

Abstract

Background

Methods

Results

Conclusions

Introduction

Section snippets

Objectives

Study design

Selection of radiographs

Interobserver reliability

Intraobserver reliability

Discussion

Conclusions

Conflict of interests

Journal of Foot and Ankle Surgery

Comparison between manual and computer assisted measurements of hallux valgus parameters

Foot and Ankle International

Goniometric versus computerised angle measurement in assessing hallux valgus

Foot and Ankle International

Radiographic angles in hallux valgus: differences between measurements made manually and with a computerised program

Foot and Ankle International

Angular measurements in the evaluation of hallux valgus deformities: a report of the ad hoc committee of the American Orthopaedic Foot and Ankle Society on angular measurements

Foot and Ankle International