Computer-Aided Design of Customized Foot Orthoses: Reproducibility and Effect of Method Used to Obtain Foot Shape

doi:10.1016/j.apmr.2011.12.019

Archives of Physical Medicine and Rehabilitation

Volume 93, Issue 5, May 2012, Pages 863-870

https://doi.org/10.1016/j.apmr.2011.12.019 Get rights and content

Abstract

Telfer S, Gibson KS, Hennessy K, Steultjens MP, Woodburn J. Computer-aided design of customized foot orthoses: reproducibility and effect of method used to obtain foot shape.

Objective

To determine, for a number of techniques used to obtain foot shape based around plaster casting, foam box impressions, and 3-dimensional scanning, (1) the effect the technique has on the overall reproducibility of custom foot orthoses (FOs) in terms of inter- and intracaster reliability and (2) the reproducibility of FO design by using computer-aided design (CAD) software in terms of inter- and intra-CAD operator reliability for all these techniques.

Design

Cross-sectional study.

Setting

University laboratory.

Participants

Convenience sample of individuals (N=22) with noncavus foot types.

Interventions

Not applicable.

Main Outcome Measures

Parameters of the FO design (length, width at forefoot, width at rearfoot, and peak medial arch height), the forefoot to rearfoot angle of the foot shape, and overall volume match between device designs.

Results

For intra- and intercaster reliability of the different methods of obtaining the foot shape, all methods fell below the reproducibility quality threshold for the medial arch height of the device, and volume matching was <80% for all methods. The more experienced CAD operator was able to achieve excellent reliability (intraclass correlation coefficients >0.75) for all variables with the exception of forefoot to rearfoot angle, with overall volume matches of >87% of the devices.

Conclusions

None of the techniques for obtaining foot shape met all the criteria for excellent reproducibility, with the peak arch height being particularly variable. Additional variability is added at the CAD stage of the FO design process, although with adequate operator experience good to excellent reproducibility may be achieved at this stage. Taking only basic linear or angular measurement parameters from the device may fail to fully capture the variability in FO design.

Section snippets

Methods

Before the commencement of this study, ethical approval was awarded by the institutional ethics committee (application reference number B10/56) and all participants gave informed, written consent. A convenience sample of healthy subjects was recruited, with the sample size being determined by the time and cost constraints of the study. Potential participants were excluded if they had a rigid cavus foot, based on clinical assessment by a qualified podiatrist. All randomization orders for testing

Results

Twenty-two healthy participants, 10 men and 12 women, with mean age ± SD of 42.8±11.4 years, mean height ± SD of 1.72±0.1m, and mean weight ± SD of 75.2±13.5kg were recruited.

The forefoot to rearfoot angle could not be accurately determined from the scans of the foam box impressions; therefore, these measures have been omitted from the analysis for both foam box techniques. ICC values falling below the predetermined quality threshold of .75 for excellent agreement have been bolded in Table 2,

Discussion

Intracaster correlations were in line with those previously reported in the literature. Laughton et al¹⁴ investigated the use of 4 methods including plaster casting, sitting foam impression, and a partial weight-bearing scan and found all intrarater ICCs for rearfoot and forefoot widths to be above 0.9. Forefoot to rearfoot angle and medial arch height ICCs were lower; however, higher values for the plaster cast forefoot to rearfoot angle were reported compared with those presented here.

Conclusions

This study investigated 6 commonly used techniques for capturing foot shape, and none met all the criteria for excellent reproducibility. The peak arch height of the final device was particularly variable, with significant differences between most of the methods. The results for volume matching also suggest that taking simple linear or angular measures from the device may not fully capture the variability associated with the shape of the FO. Further variability is added to the overall process

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The external shape of the foot and ankle can provide indications about its underlying health and function, and it is important when designing orthotic interventions for pathologies affecting the lower limb. Until recently, assessing the overall shape of the foot has been a largely subjective task, with only a few linear or circumferential measurements used, or time-consuming and unreliable plaster casts required to capture the full shape of the foot. 3D surface scanning allows a detailed digital model of the whole foot and ankle to be easily captured, and this model can subsequently be utilized and analyzed in numerous ways. Many technologies fall under the umbrella of 3D surface scanning, and several have been shown to be fast, accurate, and reproducible in the context of foot and ankle research. Given this, 3D surface scanning is being increasingly utilized in studies involving custom footwear and orthotics. The technology lends itself to capturing large sets of data and has been employed in several epidemiological studies. This chapter covers the development of 3D surface scanning, its foot and ankle biomechanics-related applications, and potential future uses.
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A foot orthosis is a simple intervention that is often prescribed for a variety of musculoskeletal conditions affecting the foot and other parts of the body. These are used to alter the interface between the foot and the shoe as well as to change some aspect of foot and ankle biomechanics during activities of daily living, such as walking and running. This chapter will describe the design of these devices, their common features, and the materials used in their construction. Kinematic, kinetic, and other biomechanical effects of foot orthoses on the foot and ankle will be reviewed, along with common conditions for which they are prescribed together with their proposed mechanisms of action. Potential areas of future research will be discussed.
Are custom-made foot orthoses of any interest on the treatment of foot pain for prolonged standing workers?
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Citation Excerpt :
This is why Tsung et al. (2004) recommend that feet be scanned in semi-weight-bearing condition as a compromise solution so that the FO give enough support to the arches while avoiding the pain and discomfort that would occur were the FO too rigid (Salles and Gyi, 2013; CHEN et al., 1994). Nevertheless, the design and manufacturing processes of general foot orthoses present many variability factors connected to the techniques used to obtain foot shape (Telfer et al., 2012) or the practitioner-specific manufacturing processes (Chevalier and Chockalingam, 2012). Prolonged standing (Freitas et al., 2005), fatigue (Garcia et al., 2015; Ochsendorf et al., 2000) and pain (Pradels et al., 2011) all affect postural activity.
The prolonged standing position is an important factor in the onset of foot musculoskeletal disorders among workers. Safety shoes, designed to protect against the physical constraints of the work environment, do not address this issue to date.
The goal of this study is to assess the possible benefits of custom-made foot orthoses among prolonged standing workers.
repeated measures without control group.
Thirty-four standing workers who suffer from foot pain volunteered for the study. Custom-made foot orthoses, designed by a podiatrist, were 3D-printed and distributed to each volunteer. Static balance as well as static and dynamic plantar pressure measurements were carried out with sensors inserted in the safety shoes, before and after three weeks of wearing foot orthoses daily. A questionnaire on pain and comfort was also distributed before and after treatment.
Feelings of pain, discomfort and heavy legs were found to be significantly reduced after wearing 3D-printed orthoses (p<0.05). Additionally, in static and dynamic conditions, a significant decrease in mean peak pressure in the rearfoot area was observed along with a significant increase in mean peak pressure in the midfoot area (p<0.05). There was also a significant improvement of balance in the medial-lateral direction.
Custom-made orthoses significantly increase the well-being of standing workers in our experimental testing conditions. The custom-made shape allows for a better balanced distribution of foot peak pressure thanks to its support and stimulation of the foot arches particularly through a shift of pressure from the heel to the midfoot.
Effect of lateral wedged insoles on the knee internal contact forces in medial knee osteoarthritis
2019, Gait and Posture
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A soft thermoplastic polylactic acid material (soft-PLA) was chosen for its material properties (www.orbi-tech.de; density: 1.35 g/cm3, tensile strength: 16 MPa, strain at yield: 290%, Young’s modulus: 380 MPa, shore hardness: 92 A) and capability to produce semi-rigid devices. Previous successful studies have been conducted adopting the same material and a similar workflow [19,20]. All data were collected at the Human Performance Laboratory at Glasgow Caledonian University.
Lateral wedge insoles (LWIs) are non-surgical interventions used in medial knee osteoarthritis (KOA) aiming at restoring correct joint biomechanics. However, the mechanical efficacy of LWIs, based on modulation of the external knee adduction moment, is partially proved and high variability in response to these devices was observed.
The principal aim of the study was to employ subject-specific musculoskeletal models to investigate the immediate effect of LWIs on the medial compressive force (MCF) in a population with medial KOA and varus alignment.
Fifteen adults (8 healthy controls age 56±3.4, BMI 25.2±2.2, hip-knee-ankle angle −1.3±2.3; and 7 KOA participants age 62±6.6, BMI 31.7±3.9, hip-knee-ankle angle 6.3±2) were recruited. Subject-specific LWIs were designed in CAD based on shape capture of the foot and manufactured via 3D printing. The required degree of heel post was added to the orthotic shell to create insoles with 0°, 5° and 10° of lateral wedge. Gait data were collected for each condition and a musculoskeletal model implemented in the Anybody Modeling System estimated the CFs normalised per bodyweight. The effect of the LWIs with respect to the baseline on the peak and the impulse of the MCF were tested with a Wilcoxon non-parametric test for paired samples.
For the KOA group, LWIs did not reduce significantly the impulse and the peak of the MCF. No dose-response trend according to the degree of wedging was observed. A high inter-subject variability was found: the impulse of the MCF varied between −12%, +10%, the peak between −5%, +7%. Moreover, LWIs had no consistent effect on shifting the load from the medial to the lateral compartment.
Subject-specific response to LWIs in a cohort of medial KOA patients was observed. Further studies are necessary to maximise the mechanical effect of LWIs on restoring normal knee joint mechanics.
Comparison of plantar pressure distribution in CAD–CAM and prefabricated foot orthoses in patients with flexible flatfeet
2017, Foot
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Compared to traditional methods, this technology has resolved problems such as casting, cast modification, therapist measurement errors, and time-consuming processes. This method also facilitates the process of making foot orthoses [5–7]. Foot orthoses efficacy may be affected by construction method, design, type and material [2].
The effect of foot orthoses on plantar pressure distribution has been proven by researchers but there are some controversies about advantages of custom-made foot orthoses to less expensive prefabricated foot orthoses.
Nineteen flatfeet adults between 18 and 45 participated in this study. CAD–CAM foot orthoses were made for these patients according to their foot scan. Prefabricated foot orthoses were prepared according to their foot size. Plantar pressure, force and contact area were measured using pedar^®-x in-shoe system wearing shoe alone, wearing CAD–CAM foot orthoses and wearing prefabricated foot orthoses. Repeated measures ANOVA model with post-hoc, Bonferroni comparison were used to test differences.
CAD–CAM and prefabricated foot orthoses both decreased pressure and force under 2nd, 3–5 metatarsal and heel regions comparing to shoe alone condition. CAD–CAM foot orthosis increased pressure under lateral toe region in comparison to shoe alone and prefabricated foot orthosis. Both foot orthoses increased pressure and contact area in medial midfoot region comparing to shoe alone condition. Increased forces were seen at hallux and lateral toes by prefabricated foot orthoses in comparison with CAD–CAM foot orthoses and control condition, respectively.
According to the results, both foot orthoses could decrease the pressure under heel and metatarsal area. It seems that the special design of CAD–CAM foot orthoses could not make great differences in plantar pressure distribution in this sample. Further research is required to determine whether these results are associated with different scan systems or design software.
Comparing the effectiveness of computer-aided design/computer-aided manufacturing (CAD/CAM) of insoles manufactured from foam box cast versus direct scans on patient-reported outcome measures: a protocol for a double-blinded, randomised controlled trial
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: Funded in part through the European Commission Framework Seven Program (grant no. NMP2-SE-2009-228893) as part of the A-Footprint project (http://www.afootprint.eu).

: No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.

: Reprints are not available from the author.

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Original articleComputer-Aided Design of Customized Foot Orthoses: Reproducibility and Effect of Method Used to Obtain Foot Shape

Abstract

Objective

Design

Setting

Participants

Interventions

Main Outcome Measures

Results

Conclusions

Section snippets

Methods

Results

Discussion

Conclusions

Gait Posture

Dimensional accuracy of ankle-foot orthoses constructed by rapid customization and manufacturing framework

J Rehabil Res Dev

The use of CAD/CAM technology in prosthetics and orthotics— current clinical models and a view to the future

J Rehabil Res Dev

Mass customization of foot orthoses for rheumatoid arthritis using selective laser sintering

IEEE Trans Biomed Eng

Advanced trans-tibial socket fabrication using selective laser sintering

Prosthet Orthot Int

An experimental and theoretical framework for manufacturing prosthetic sockets for transtibial amputees

IEEE Trans Biomed Eng

The modern era of orthotics

Prosthet Orthot Int

Variability of neutral-position casting of the foot

J Am Podiatr Med Assoc

Original article
Computer-Aided Design of Customized Foot Orthoses: Reproducibility and Effect of Method Used to Obtain Foot Shape