Methodological and statistical approaches for the assessment of foot shape using three-dimensional foot scanning: a scoping review

Abstract

Objective: The objectives of this study were to: (i) review and provide a narrative synthesis of three-dimensional (3D) foot surface scanning methodological and statistical analysis protocols, and (ii) develop a set of recommendations for standardising the reporting of 3D foot scanning approaches.

Methods: A systematic search of the SCOPUS, ProQuest, and Web of Science databases were conducted to identify papers reporting 3D foot scanning protocols and analysis techniques. To be included, studies were required to be published in English, have more than ten participants, and involve the use of static 3D surface scans of the foot. Papers were excluded if they reported two-dimensional footprints only, 3D scans that did not include the medial arch, dynamic scans, or derived foot data from a full body scan.

Results: The search yielded 78 relevant studies from 17 different countries. The available evidence showed a large variation in scanning protocols. The subcategories displaying the most variation included scanner specifications (model, type, accuracy, resolution, capture duration), scanning conditions (markers, weightbearing, number of scans), foot measurements and definitions used, and statistical analysis approaches. A 16-item checklist was developed to improve the consistency of reporting of future 3D scanning studies.

Conclusion: 3D foot scanning methodological and statistical analysis protocol consistency and reporting has been lacking in the literature to date. Improved reporting of the included subcategories could assist in data pooling and facilitate collaboration between researchers. As a result, larger sample sizes and diversification of population groups could be obtained to vastly improve the quantification of foot shape and inform the development of orthotic and footwear interventions and products.

Fig. 1

Flowchart of included studies

Fig. 2

Frequency of reported 3D foot scan dimensions from the included papers

Fig. 3

The most frequently reported 3D foot scan dimensions from the included papers. A: foot length (FL), B: ball width, C: ball girth, D: instep height, E: heel width, F: length to first metatarsal head, G: instep girth

Fig. 4

The INFOOT USB scanning system (IFU-S-01, I-Ware Laboratory Co., Ltd, Japan), the most frequently reported 3D scanner from the included papers

Fig. 5

Diagrammatic representations of the most frequently reported 3D foot scanning postures from the included papers. A: half-weightbearing (bipedal), B: fully weightbearing (unipedal), C: non-weightbearing, D: partial weightbearing (seated), E: partial weightbearing, seated, inclined plane

Fig. 6

The use of principal components analysis of 3D point cloud data to identify shape differences between females and males. Image adapted from Stankovic et al. (J Foot Ankle Res 2018;11:8)