Objective assessment of foot radiographs: technique and normative values for the medial column
Creators: name: Reinhart, Glenn
name: Friebele, Jill
name: F. Kamalei Cruz
name: Tabaie, Sean
name: Davids, Jon R.
name: Vedant Kulkarni
name: Bagley, Anita
name: Cung, Nina Q.
Publisher: name: F1000Research
Year: 2017

description: INTRODUCTION: Weight-bearing foot radiographs are critical to the understanding of foot deformity in children with cerebral palsy.  A mechanical model divides the foot into two columns (medial and lateral) and three segments (hindfoot, midfoot, forefoot)<sup>1</sup>. The medial column consists of the talus, navicular, cuneiforms, and first through third metatarsals. Breakdown of the medial column is a feature of equinoplanovalgus foot deformity, frequently seen in children with cerebral palsy. Establishing methods to precisely characterize this breakdown would be valuable in the assessment and management of foot deformity in this population. Previous work has validated quantitative radiographic measures of the overall alignment of the medial column based upon three segments: AP talo -1<sup>st</sup> metatarsal, AP talo-navicular, and Lateral talo-1<sup>st</sup> metatarsal. However, techniques for an objective assessment of the individual components (“sub-segmental”) of medial column alignment of the foot have not yet been described. <br> <br>CLINICAL SIGNIFICANCE: The goals of the current study are to develop and validate additional radiographic measures of medial column foot alignment in children and to establish normative values for these new measures.<br> <br>METHODS: Standing Anterior-Posterior (AP) and Lateral radiographs of the unaffected/normal feet of 20 children (mean age 11.3 years) were analyzed. Three validated measures along with seven new measures of medial column segmental alignment were calculated. Previously validated measures included: AP talo-1<sup>st</sup> metatarsal, AP talo-navicular, and Lateral talo-1<sup>st</sup> metatarsal. The new measures included: 1) AP naviculo-cuneiform, 2) AP Cuneiform-1<sup>st</sup> metatarsal, 3) AP 1<sup>st</sup> metatarsal-proximal phalanx, 4) Lateral talo-navicular, 5) Lateral naviculo-cuneiform, 6) Lateral cuneiform-1<sup>st</sup> metatarsal, and 7) Talar pitch. Standard techniques were used to describe the longitudinal axis of each bone. Measurements were performed on all feet by an experienced Orthopaedic Surgeon and medical student. Intra- and inter-observer reliability were measured by intra-class correlation coefficients. Normative values for medial column alignment angles were calculated from feet of 20 children, using mean and standard deviations.    <br> <br>RESULTS : Intra-observer reliability, based upon repeated measurements of feet from 10 children by a surgeon, was good across all radiographic measures (0.78 to 0.99). However, inter-observer reliability was variable as both the surgeon and medical student performed repeated measurements of feet from 20 children. Inter-rater reliability was good for the previously validated measures (AP talo-1<sup>st</sup> metatarsal, AP talo-navicular, Lateral talo-1<sup>st</sup> metatarsal) and three new measures (AP cuneiform-1<sup>st</sup> metatarsal, AP 1<sup>st</sup> metatarsal-proximal phalanx, Talar pitch; 0.78 to 0.89), yet poor to moderate for the rest of the measures (Lateral naviculo-cuneiform, AP naviculo-cuneiform, Lateral cuneiform-1<sup>st</sup> metatarsal, Lateral talo-navicular; -0.089 to 0.697). Normative values and standard deviations are shown in Table 1.<br><br>DISCUSSION: The technique for an objective radiographic assessment of the sub-segmental components of medial column alignment of the foot showed good reliability for <i>some</i>, but not <i>all</i> of the measurements. The new seven sub-segmental relationships of bones in the midfoot were not statistically significant and exhibited poor to moderate inter-rater reliability. However, when the techniques were performed by an individual examiner, the results were consistent and reliable. We believe that there is some clinical value in performing a series of repeated measurements in order to analyze medial column alignment. The radiographic measures developed in this study will help clinicians better understand medial column alignment in a more detailed quantitative and qualitative manner.