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Dose–response effects of customised foot orthoses on lower limb kinematics and kinetics in pronated foot type
Journal of Biomechanics 46 (2013) 1489–1495
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Dose–response effects of customised foot orthoses on lower limb kinematics and kinetics in pronated foot type Scott Telfer n, Mandy Abbott, Martijn P.M. Steultjens, James Woodburn Institute for Applied Health Research, School of Health and Life Sciences, Glasgow Caledonian University, UK
art ic l e i nf o
a b s t r a c t
Article history: Accepted 30 March 2013
Despite the widespread use of customised foot orthoses (FOs) for the pronated foot type there is a lack of reliable information on the dose–response effect on lower limb mechanics. This study investigated these effects in subjects with normal and pronated foot types. Customised FOs were administered to 12 participants with symptomatic pronated foot type and 12 age and gender matched controls. A computeraided design (CAD) software was used to design nine FOs per participant with dose incrementally changed by varying only the rearfoot post angle. This was done in 21 increments from 61 lateral to 101 medial posting. A 3D printing method was used to manufacture the FOs. Quantification of the dose– response effect was performed using three-dimensional gait analyses for selected rearfoot and knee kinematics and kinetics. Under these experimental conditions, significant and linear effects of posting were seen for the peak (po 0.001) and mean (po0.001) rearfoot eversions, peak (p¼ 0.003) and mean (po 0.001) ankle eversion moments and peak (p¼0.017) and mean (p¼0.005) knee adduction moment variables. Group effects were observed for the peak (p ¼0.007) and mean (p¼ 0.007) forefoot abduction and for the peak (p ¼0.007) knee adduction moment. A significant interaction between posting and group was seen for internal tibial rotation (p ¼0.004). These data indicate that a dose–response effect, with a linear trend for both the rearfoot and knee, exists for customised FOs used to treat pronated foot type. & 2013 Elsevier Ltd. All rights reserved.
Keywords: Foot Orthoses Gait analysis Multisegment foot 3D printing
1. Introduction Foot orthoses (FOs) are an effective intervention to reduce rearfoot eversion (Cheung et al., 2011). The biomechanical mode-ofaction is achieved by incorporating medial wedges (or posts) and/or a contoured medial longitudinal arch on the FO (Brown et al., 1995; Nawoczenski et al., 1995; Woodburn et al., 2003; Nester et al., 2003; MacLean et al., 2006; Davis et al., 2008). These components have been used alone or in combination on flat insoles, pre-fabricated, and custom-made FOs (Eng and Pierrynowski, 1994; Stacoff et al., 2000; Mündermaan et al., 2003; Nigg et al., 2003; Nester et al., 2003; Woodburn et al., 2003; Ferber and Benson, 2011). Their design specifications provide the indicative dose either through the height or angle of the wedge or arch contour (Johanson et al., 1994; Nawoczenski et al., 1995; Stacoff et al., 2000; MacLean et al., 2006; Zifchock and Davis, 2008). Using calcaneal eversion as a proxy measurement of foot pronation, a recent meta-analysis has demonstrated that FOs are an effective anti-pronation intervention (Cheung et al., 2011). n Corresponding author at: Institute for Applied Health Research, School of Health and Life Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, UK. Tel.: +44 141 331 8475. E-mail addresses: [email protected], [email protected] (S. Telfer).
0021-9290/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbiomech.2013.03.036
The outcome is a kinematic measurement and mechanical or therapeutic targets have included reduced peak eversion (or subterms such as pronation) (Bates et al., 1979; Johanson et al., 1994; Brown et al., 1995; Leung et al., 1998; Genova and Gross, 2000; Stacoff et al., 2000; Williams et al., 2003; Mündermaan et al., 2003; MacLean et al., 2006; Zifchock and Davis, 2008; Eslami et al., 2009; Ferber and Benson, 2011), and eversion/inversion moment (Novick and Kelley, 1990; Mündermaan et al., 2003; Williams et al., 2003; MacLean et al., 2006). It should be noted however that the mean reduction in rearfoot eversion determined by the metaanalysis was around 21, and it has been questioned whether changes of this magnitude are a sufficient change to alter the basic biomechanics of gait (Nigg, 2001). Whilst efficacy has been demonstrated for a single dose, to the best of our knowledge there is no reliable information on the dose–response effect of antipronation FOs on lower limb kinematics and kinetics. The lack of evidence for dose–response is not surprising. These studies are difficult and costly to conduct. The largest potential barrier is hand fabrication and the ability to control and standardise the dose of the anti-pronation orthotic components such as medial heel wedges. These can now be largely overcome with advances in computer-aided design and manufacturing technologies (CAD/CAM). Components such as medial heel wedges and arch height can be specified within 7 11/1 mm. These components
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Fig. 1. Extrinsic rearfoot posting in computer aided design foot orthoses (FOs), left: laterally posted FO (green); centre: neutrally posted FO; and right: medially posted FO (green). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
can be incrementally changed on multiple CAD designs for the same standard or subject-specific FO shell. The level of customisation required to achieve an optimised mechanical response associated with therapeutic benefit is poorly understood (Menz, 2009). Reliable data on dose–response may form the basis of determining how much FO customisation is necessary to treat pronated foot type, and in addition may enable a better understanding of any potentially beneficial or harmful mechanical response at the rearfoot as well as the knee and hip where effects have been previously demonstrated (Mündermaan et al., 2003; Williams et al., 2003; Eslami et al., 2009; Chen et al., 2010). This study aims to investigate the dose–response effect of customised FOs on lower limb and foot mechanics in subjects with normal and pronated foot types. The study will exploit new capabilities in CAD-CAM technologies to incrementally change the dose of the external rearfoot post-design feature (Fig. 1). Our primary hypothesis is that by progressively altering the angle of the rearfoot post on a personalised FO design, there will be a significant and linear effect on the kinematics and kinetics of the lower limb during the stance phase. In addition, we hypothesise that there will be significant differences in response between symptomatic pronated foot types and asymptomatic normal foot types.
2. Materials and methods 2.1. Participants Ethical approval for this study was granted by the local National Health Service Ethics Committee (reference: 10/S0703/73). In total 24 participants were enroled in the study, 12 in the patient group and 12 age and gender matched controls. Group demographics are presented in Table 1. All participants provided informed, written consent upon enrolment into the study. Potential participants were recruited from local podiatry centres. Participants were eligible for inclusion if they had a pronated foot type as defined by the Foot Posture Index (FPI) (Redmond et al., 2006), a relaxed calcaneal stance position (RCSP) 441 everted; a current history of self-reported foot and ankle pain; and where their foot condition indicated a custom FO treatment. Control participants were eligible for inclusion if they had a normal foot type as defined by the FPI, a RCSP ≤41 everted, and no current or significant past-history of a diagnosable musculoskeletal, rheumatological or orthopaedic disorder of the lower limb or foot.
2.2. Foot orthoses All FOs used in this study were 3/4 length semi-rigid devices which were designed, based on a 3D surface scan of the foot, using an OrthoModel software (Delcam, Birmingham, UK) through a previously described and validated protocol (Telfer et al., 2012a). FOs were fabricated using a three-dimensional (3D) printing system (RapMan; Bits from Bytes, Clevedon, UK) in polylactide (PLA). Preliminary testing for this study showed that the PLA devices were of similar flexibility ( o 10% difference) to equivalent polypropylene devices based on arch displacement under a standard load.
Table 1 Participant demographics for patient and control groups.
Gender Age (years) Weight (kg) Height (m) Relaxed calcaneal stance position (deg) Foot posture index
Patient
Control
6F/6M 287 7.3 72.8 7 12.3 1.737 0.07 6.8 7 0.7 6.8 7 0.9
6F/6M 31.7 7 10 70.37 9.1 1.69 7 0.09 2.7 7 1.4 1.8 7 0.9
Reported as mean 7 SD
2.3. Protocol Participants were assessed by a UK Health and Care Professions Council registered podiatrist (MA) to ensure they met the inclusion criteria. Weightbearing 3D surface scans of both feet were taken with the foot held in a subtalar joint neutral position. The 3D scan file was uploaded to the CAD software and participant-specific FOs designed and manufactured as described above. The FO devices were fitted to the patient by the podiatrist to ensure satisfactory immediate fit and comfort for use. A schedule was provided to standardise FO device accommodation and use over a 14-day period. Nine variations on the original FO CAD design for one foot – the symptomatic side for the patient group if they had unilateral pain or randomly chosen for those with bilateral pain and controls – were produced and manufactured. In these variations on the original design, the level of the external rearfoot post was varied from 61 lateral to 101 medial in 21 increments. Approximately 2 weeks after fitting and having successfully introduced the original pair of FOs into daily wear, the participant returned to the laboratory for the main evaluation. Retroflective markers were attached to their test leg and pelvis in order to define a unilateral marker model which included the pelvis, thigh, shank, rearfoot, forefoot and full foot segments. A full description of the marker model is provided in the Supplementary materials. Footwear was standardised, with all participants wearing a modified pair of neutrally posted training shoes with holes cut at relevant landmarks to allow the markers to be directly attached to the foot. The trainers also had zips sewn into the sides to allow the trainers to be donned and doffed without requiring the removal of markers from the foot as this has previously been demonstrated to be the source of error in this type of experiment (Telfer et al., 2010). Further information on the footwear used is also provided in the Supplementary materials. For all gait trials, a 12 camera motion capture system (Qualysis AB, Gothenburg, Sweden) was used to track the retroreflective markers at a frequency of 120 Hz, and a force plate embedded into the walkway was used to measure ground reaction forces at 2400 Hz. A static trial was recorded with the participant standing barefoot followed by anatomical markers being removed. Walking trials were repeated for shod only and the nine FO conditions. The non-test foot used the same FO designed to the previously determined prescription during all FO test conditions. The testing order was randomised for each participant to avoid order effects, and researchers and participants were blinded to the posting level of the FO during testing and data processing. Participants were given time to acclimatize to each new condition until they were comfortable and a consistent gait pattern was visually observed by the researchers. They were then asked to walk along the motion capture walkway until at least seven clean strikes on the force plate with the foot of interest were recorded. Walking speed was controlled to 7 5% of the participant's predetermined self selected speed and trials outside these limits rejected. To reduce potential fatigue effects, a rest period of approximately 2 min was given after each set of walking trials while the FO was changed.
S. Telfer et al. / Journal of Biomechanics 46 (2013) 1489–1495
2.4. Analysis A core set of clinically meaningful kinematic and kinetic variables were identified as those which form mechanical therapeutic targets for FO interventions, and the analysis was limited to these variables. These were: the peak and mean rearfoot (RF) eversions; peak and mean external ankle eversion moments; peak and mean forefoot (FF) abductions; peak and mean internal tibial rotations; peak knee external adduction moment during the first 50% of stance phase (1KAM); peak knee external adduction moment during final 50% of stance phase (2KAM); and mean knee external adduction moment (mean KAM). All data processing was carried out using a Visual 3D software (C-Motion Inc., Germantown, MD). The mean of the final five walking trials from each test condition with complete marker tracking was used in the analysis. Data were low pass filtered at 6 Hz (Winter, 1990). Kinematic variables were anatomically referenced to the proximal segment with the exception of internal tibial rotation which was referenced to the rearfoot. Kinetic variables were anatomically referenced to the proximal segment. For analysis, all variables were defined relative to the shod condition, which was considered the baseline for this study. The two way mixed effect ANOVAs were performed to determine if the effects of the FO posting and the foot type were significant at α ¼ 0.05 level. Where significant effects of the FO was found, linear, quadratic and cubic contrasts were tested to determine if there was a linear trend to the effect.
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Significant, linear main effects (P o0.001) were found for posting level in both the RF eversion peak and RF eversion mean, with a mean reduction of 0.261 (SD 0.11) and 0.281 (SD 0.141) per 21 of posting in the medial direction respectively. No effect was found for the group. Similarly, the ankle eversion moment peak and mean were significantly affected by posting level (p ¼0.003 and po 0.001), with FOs reducing the moments by 1.1% (SD 1.1%) and 2.3% (SD 2.1%) per 21 of posting in the medial direction respectively. Significant main effects were found at the knee for posting level in 2KAM and mean KAM (p ¼0.017 and p ¼0.005 respectively), along with a significant group effect for 2KAM. Posting effects for 2KAM were equivalent to increases of 1.1% (SD 1.1%) for the patient group and 0.9% (SD 1.1%) for the control group per 21 of posting in the medial direction, and for mean KAM a 1.4% (SD 1.1%) increase per 21 medial posting in the medial direction. Motion/moment time curves and individual participant responses for variables which were found to show a significant linear effect are provided in Supplementary materials.
3. Results
4. Discussion
The full results for all variables tested are presented in Table 2 and significant results are presented graphically in Figs. 2 and 3 for kinematic and kinetic results respectively. The only significant interaction between posting level and group was for internal tibial rotation mean (p¼ 0.004; linearity p¼ 0.003). The FF adduction peak and mean showed significant main effects for the group (both p ¼0.007), and FF adduction mean also showed significant main effects for posting level (p ¼0.049), however this trend was non-significant for linear, quadratic or cubic contrasts.
The aim of this study was to investigate the dose–response effect of custom FOs on lower limb mechanics in pronated foot type. Our findings suggest that when the rearfoot post of a custom FO is incrementally changed there is a linear mechanical response observed at the rearfoot and knee joint. Moreover, this response can be observed in both individuals with and without pronated foot type. These results confirm and extend our knowledge and understanding of the mechanical effects of custom FOs for pronated foot type.
Table 2 Two way mixed effects ANOVA for kinematic and kinetic variables.
Peak RF eversion
Mean RF eversion
Peak FF abduction
Mean FF abduction
Peak internal tibial rotation
Mean internal tibial rotation
Peak ankle eversion moment
Mean ankle eversion moment
Peak KAM (1st)
Peak KAM (2nd)
Mean KAM
Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group
Wilks' Lambda
F
p-value
Partial eta squared
Best contrast
Trend per 21 posting lateral to medial
0.087 – 0.721 0.114 – 0.724 0.509 – 0.572 0.413 – 0.641 0.616 – 0.501 0.475 – 0.278 0.271 – 0.689 0.202 – 0.425 0.436 – 0.815 0.348 – 0.563 0.284 – 0.751
19.748 1.704 0.725 14.503 5.402 0.716 1.806 8.756 1.404 2.662 8.679 1.05 1.169 1.735 1.867 2.074 3.261 4.876 5.054 0.032 0.845 7.419 0.01 2.538 2.424 0.713 0.426 3.51 8.89 1.456 4.721 4.016 0.621
o0.001 0.205 0.668 o0.001 0.364 0.675 0.154 0.007 0.272 0.049 0.007 0.444 0.377 0.201 0.141 0.106 0.085 0.004 0.003 0.86 0.579 o0.001 0.92 0.057 0.066 0.408 0.888 0.017 0.007 0.253 0.005 0.058 0.748
0.913 0.072 0.279 0.886 0.038 0.276 0.491 0.285 0.428 0.587 0.283 0.359 0.384 0.073 0.499 0.525 0.129 0.722 0.729 0.001 0.311 0.789 40.001 0.575 0.564 0.031 0.185 0.652 0.288 0.437 0.716 0.154 0.249
Linear (Po 0.001) – – Linear (Po 0.001) – – – – – Cubic (p ¼ 0.251) – – – – – – – Linear (p¼ 0.003) Linear (po 0.001) – – Linear (po 0.001) – – – – – Linear (po 0.001) – – Linear (po 0.001) – –
−0.261 – – −0.281 – – – – – – – – – – – – – – −0.02 (% BW H) – – −0.016 (% BW H) – – – – – 0.018 (C); 0.015 (P); % BW H – – 0.015 (% BW H) –
Significant values have been highlighted in bold. RF: rearfoot; FF: forefoot; KAM: external knee adduction moment; C: control group; and P: patient group.
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Fig. 2. Kinematic results, RF: rearfoot; FF: forefoot; tib rot: tibial rotation; SE: standard error; nL: degrees laterally posted; 0N: neutrally posted; and nM: degrees medially posted.
Reducing calcaneal eversion is a viable and achievable biomechanical target (Cheung et al., 2011). Although current evidence for a link between increased motion control for individuals with pronated foot types and reduced injury rates in sports is weak (Ryan et al., 2011), in inflammatory conditions such as rheumatoid arthritis it has been strongly hypothesised that the acquired flat foot and excessive rearfoot motion regularly seen in these patients (Turner et al., 2008; Woodburn et al., 2002a) are related to ultrasound and MRI confirmed features of joint and tendon damage, particularly those involved in controlling the frontal plane motion of the foot (Dubbeldam et al., 2013; Woodburn et al., 2002b). While the direction of cause and effect has not been fully determined, there is good evidence from randomised controlled trials that an early intervention using customised FO devices results in reduced abnormal kinematics and improved patient reported outcomes (Hennessy et al., 2012; Woodburn et al., 2003). The findings from the present study suggest that there may be a potential to optimise FO design for biomechanical outcomes using dose response information at the individual patient level. Customised FOs have been shown to alter frontal plane rearfoot kinematics (Brown et al., 1995; Genova and Gross, 2000; Branthwaite et al., 2004; Woodburn et al., 2003; Davis et al., 2008; Zifchock and Davis., 2008) and frontal plane ankle complex kinetics (Pascual Huerta et al., 2009; Nester et al., 2003) during
walking. This study provides a new evidence of a clear and linear “dose–response” effect for external rearfoot posts around the frontal plane of the ankle complex. Previous studies have reported unsystematic rearfoot eversion responses to FO interventions (Stacoff et al., 2000). While there was some variation in the dose responses found in the present study, there was a consistent direction of effect across all participants and the majority (485%) showed a dose response within 0.151 of the mean (see Supplementary materials). The neutrally posted devices tended to reduce rearfoot eversion by approximately 21, which is in line with recent metaanalysis results (Cheung et al., 2011), with the 81 and 101 medially posted devices achieving reductions for peak rearfoot eversion of up to 41 in the group with pronated foot type. The overall range of the dose response for kinematic variables across the FO conditions around the neutral posting response was 2–2.51. Whether this potential range is clinically relevant in terms of preventing and treating impairments associated with pronated foot type is unclear. Based on existing knowledge, we would have expected the laterally posted devices to have shown an increase in rearfoot eversion variables, both kinematic and kinetic (Nester et al., 2003). The results presented here demonstrate that for this type of device this was not the case. Our hypothesis for this unexpected result is that, beyond the effects of posting, the contoured medial arch of the orthoses provided a significant support to the foot which
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Fig. 3. Results for kinetic variables, KAM: knee adduction moment; % BW H: % bodyweight multipled by height; SE: standard error; nL: degrees laterally posted; 0N: neutrally posted; nM: degrees medially posted; C: control group; and P: patient group.
prevented deformation of the medial longitudinal arch during dynamic function and thus reduced overall levels of pronation. The similar trends for both peak and mean variables suggest that the effect of the FO is to control and support the position of the foot throughout the full stance phase and this is also demonstrated in the motion time curves (see Supplementary materials). Functionally, we would expect the trend seen for reduced kinematic rearfoot eversion to be mirrored by similar trends for ankle eversion moment across the full stance phase and this was supported by the findings from this study. It should be noted that the between subject variability seen for kinetic measurements was generally larger than for kinematic measurements, and this may reflect the increased difficultly in reliably measuring these variables. Further work is required to determine if the relative reductions in eversion moments seen are clinically relevant. Recent work by Liu et al. (2012) has suggested that individual variability relating to the effect of FOs on tibial rotation which has been noted in a number of previous studies (McPoil and Cornwall, 2000; Mündermaan et al., 2003; Stacoff et al., 2000), may be due to the orthotic effects being accommodated at the ankle rather than the subtalar joint. This is supported by the lack of a systematic main effect of posting level on internal tibial rotation that was found in the current study, with our results suggesting that foot type does not allow individuals who respond to FO interventions by reducing internal tibial rotation to be identified. This study suggests that customised FOs of this type have a significant effect on the external knee adduction moment, with MKAM and 2KAM both increasing with medial posting. In the control group, even the laterally posted devices tended to cause increases in these variables. Elevated KAMs have been linked to the development and progression of medial compartment knee osteoarthritis (Miyazaki et al., 2002) and indeed the aim of many
FO interventions for this disease is based around unloading the medial compartment (Hinman et al., 2012). The proposed mechanism for these interventions is that the centre of pressure is shifted laterally, reducing the knee adduction moment arm (Gélis et al., 2008), however the most commonly used devices for this purpose are full length flat wedges without a medial arch support (Bennell et al., 2011). Clinicians should be aware that when prescribing the type of FO used in the current study for foot or ankle problems, an unintended consequence may be the device's tendency to increase the KAM, particularly in normal foot types, and that the KAM will further increase with greater levels of medial posting. Furthermore, these results suggest that the mechanical effects and outcome of this FO should be investigated in medial knee osteoarthritis patients who have normal foot types. The test devices used in the study were customised to the participant; however the use of CAD meant that the modifications could be made in a highly repeatable manner. The use of recently developed low cost printing systems for fabricating FOs has previously been proposed (Telfer et al., 2012b) however to our knowledge this is the first study to utilise the technique for a research study involving a patient group. There are a number of limitations with this study. Primary among these was the fact that only short term FO mechanical response was tested. There is some evidence, particularly at the knee, that biomechanical effects of orthotic interventions may change over wear periods of several weeks (Turpin et al., 2012). The participants in this study did wear the pre-test devices for a period of at least 1 week prior to the main evaluation, so arguably they were familiarised to wearing FOs, however it is unclear whether the variations on this design which were evaluated in the gait laboratory would have had different effects on the participant over an extended period of wear. Other limitations are related to well-recognised sources of measurement error associated with multi-segmented foot kinematics.
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These include the natural variation in gait (White et al., 1999) and the use of skin mounted markers (Nester et al., 2007). Holes were also cut in the shoes, including one at the heel counter, to allow markers to be attached directly to the foot and this may have affected the mechanical properties of the footwear. The markers remained in-situ between test-conditions in a single session to limit intra-subject variation. As this was an exploratory study, a large number of variables were tested. While the majority of significant results were consistent (for example both mean and peak rearfoot eversion showed similar trends) and were supported by previous reports in the literature, it is possible that some significant findings are due to chance. This study tested 3/4 length semi-rigid FOs produced using a CAD software, and caution is advised before extrapolating these results to other types of FO with different design features. Further research is required to determine the biomechanical response in other postural and pathological foot types and under different test conditions such as running. In conclusion, this study has demonstrated that, at a group level, there is a strong linear dose–response effect for frontal plane kinematics of the rearfoot, and frontal plane kinetics of the ankle and knee. There were significant differences between groups at the knee and forefoot.
Conflict of interest statement The authors declare that they have no conflict of interest relating to the material presented in this article.
Acknowledgements This work was funded through the European Commission Framework Seven Program (Grant No. NMP2-SE-2009-228893) as part of the A-FOOTPRINT Project (www.afootprint.eu). The funders had no input in the study design, collection, analysis and interpretation of data; the writing of the manuscript; or the decision to submit for publication.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.jbiomech.2013.03.036.
References Bates, B.T., Osternig, L.R., Mason, B., James, L.S., 1979. Foot orthotic devices to modify selected aspects of lower extremity mechanics. American Journal of Sports Medicine 7, 338–342. Bennell, K.L., Bowles, K.-A., Payne, C., Cicuttini, F., Williamson, E., Forbes, A., Hanna, F., Davies-Tuck, M., Harris, A., Hinman, R.S., 2011. Lateral wedge insoles for medial knee osteoarthritis: 12 month randomised controlled trial. British Medical Journal 342, d2912. Branthwaite, H.R., Payton, C.J., Chockalingam, N., 2004. The effect of simple insoles on three-dimensional foot motion during normal walking. Clinical Biomechanics 19, 972–977. Brown, G.P., Donatelli, R., Catlin, P.A., Wooden, M.J., 1995. The effect of two types of foot orthoses on rearfoot mechanics. Journal of Orthopaedic and Sports Physical Therapy 21, 258–267. Chen, Y.C., Lou, S.Z., Huang, C.Y., Su, F.C., 2010. Effects of foot orthoses on gait patterns of flat feet patients. Clinical Biomechanics 25, 265–270. Cheung, R.T., Chung, R.C., Ng, G.Y., 2011. Efficacies of different external controls for excessive foot pronation: a meta analysis. British Journal of Sports Medicine 45, 743–751. Davis, I.S., Zifchock, R.A., Deleo, A.T., 2008. A comparison of rearfoot motion control and comfort between custom and semicustom foot orthotic devices. Journal of the American Podiartic Medicine Association 98, 394–403. Dubbeldam, R., Baan, H., Nene, A.V., Drossaers-Bakker, K,W., van-de-Laar, M.A., Hermens, H.J., Buurke, J.H., 2013. Foot and ankle kinematics in rheumatoid
arthritis: influence of foot and ankle joint and leg tendon pathologies. Arthritis Care and Research 65, 503–511. Eng, J.J., Pierrynowski, M.R., 1994. The effect of soft foot orthotics on threedimensional lower-limb kinematics during walking and running. Physical Therapy 74, 836–844. Eslami, M., Begon, M., Hinse, S., Sadeghi, H., Popov, P., Allard, P., 2009. Effect of foot orthoses on magnitude and timing of rearfoot and tibial motions, ground reaction force and knee moment during running. Journal of Science and Medicine in Sport 12, 679–684. Ferber, R., Benson, B., 2011. Changes in multi-segment foot biomechanics with a heat-mouldable semi-custom foot orthotic device. Journal of Foot and Ankle Research 21, 18. Gélis, A., Coudeyre, E., Hudry, C., Pelissier, J., Revel, M., Rannou, F., 2008. Is there an evidence-based efficacy for the use of foot orthotics in knee and hip osteoarthritis? Elaboration of French clinical practice guidelines. Joint Bone Spine 75, 714–720. Genova, J.M., Gross, M.T., 2000. Effect of foot orthotics on calcaneal eversion during standing and treadmill walking for subjects with abnormal pronation. Journal of Orthopaedic and Sports Physical Therapy 30, 664–675. Hennessy, K., Woodburn, J., Steultjens, M.P., 2012. Custom foot orthoses for rheumatoid arthritis: a systematic review. Arthritis Care and Research 64, 311–320. Hinman, R.S., Bowles, K.A., Metcalf, B.B., Wrigley, T.V., Bennell, K.L., 2012. Lateral wedge insoles for medial knee osteoarthritis: effects on lower limb frontal biomechanics. Clinical Biomechanics 27, 27–33. Pascual Huerta, J., Ropa Moreno, J.M., Kirby, K.A., García Carmona, F.J., Orejana García, A.M., 2009. Effect of 7-degree rearfoot varus and valgus wedging on rearfoot kinematics and kinetics during the stance phase of walking. Journal of the American Podiatric Medical Association 99, 415–421. Johanson, M.A., Donatelli, R., Wooden, M.J., Andrew, P.D., Cummings, G.S., 1994. Effects of three different posting methods on controlling abnormal subtalar pronation. Physical Therapy 74, 149–158. Leung, A.K., Mak, A.F., Evans, J.H., 1998. Biomedical gait evaluation of the immediate effect of orthotic treatment for flexible flat foot. Prosthetics and Orthotics International 22, 25–34. Liu, A., Nester, C.J., Jones, R.K., Lundgren, P., Lundberg, A., Arndt, A., Wolf, P., 2012. Effect of an antipronation foot orthosis on ankle and subtalar kinematics. Medicine and Science in Sports and Exercise 44, 2384–2391. MacLean, C., Davis, I.M., Hamill, J., 2006. Influence of a custom foot orthotic intervention on lower extremity dynamics in healthy runners. Clinical Biomechanics 21, 623–630. McPoil, T.G., Cornwall, M.W., 2000. The effect of foot orthoses on transverse tibial rotation during walking. Journal of the American Podiatric Medical Association 90, 2–11. Menz, H.B., 2009. Foot orthoses: how much customisation is necessary? Journal of Foot and Ankle Research 2, 23. Miyazaki, T., Wada, M., Kawahara, H., Sato, M., Baba, H., Shimada, S., 2002. Dynamic load at baseline can predict radiographic disease progression in medial compartment knee osteoarthritis. Annals of Rheumatic Disease 61, 617–622. Mündermaan, A., Nigg, B.M., Humble, R.N., Stefanyshyn, D.J., 2003. Foot orthotics affect lower extremity kinematics and kinetics during running. Clinical Biomechanics 18, 254–262. Nawoczenski, D.A., Cook, T.M., Saltzman, C.L., 1995. The effect of foot orthotics on three-dimensional kinematics of the leg and rearfoot during running. Journal of Orthopaedic and Sports Physical Therapy 21, 317–327. Nester, C.J., van der Linden, M.L., Bowker, P., 2003. Effect of foot orthoses on the kinematics and kinetics of normal walking gait. Gait and Posture 17, 180–187. Nester, C.J., Jones, R.K., Liu, A., Howard, D., Lundberg, A., Arndt, A., Lundgren, P., Stacoff, A., Wolf, P., 2007. Foot kinematics during walking measured using bone and surface mounted markers. Journal of Biomechanics 40, 3412–3423. Nigg, B.M., 2001. The role of impact forces and foot pronation: a new paradigm. Clinical Journal of Sport Medicine 11, 2–9. Nigg, B.M., Stergiou, P., Cole, G., Stefanyshyn, D., Mündermaan, A., Humble, N., 2003. Effect of shoe inserts on kinematics, centre of pressure, and leg joint moments during running. Medical Science in Sports and Exercise 35, 314–319. Novick, A., Kelley, D.L., 1990. Position and movement changes of the foot with orthotic intervention during the loading response of gait. Journal of Orthopaedic and Sports Physical Therapy 11, 301–312. Redmond, A.C., Crosbie, J., Ouvrier, R.A., 2006. Development and validation of a novel rating system for scoring standing foot posture: the foot posture index. Clinical Biomechanics 21, 89–98. Ryan, M.B., Valiant, G.A., McDonald, K., Taunton, J.E., 2011. The effect of three different levels of footwear stability on pain outcomes in women runners: a randomised control trial. British Journal of Sports Medicine 45, 715–721. Stacoff, A., Reinschmidt, C., Nigg, B.M., van den Bogert, A.J., Lundberg, A., Denoth, J., Stüssi, E., 2000. Effects of foot orthoses on skeletal motion during running. Clinical Biomechanics 15, 54–64. Telfer, S., Gibson, K.S., Hennessy, K., Steultjens, M.P., Woodburn, J., 2012a. Computer-aided design of customized foot orthoses: reproducibility and effect of method used to obtain foot shape. Archives of Physical Medicine and Rehabilitation 93, 863–870. Telfer, S., Morlan, G., Hyslop, E., Semple, R., Rafferty, D., Woodburn, J., 2010. A novel device for improving marker placement accuracy. Gait and Posture 32, 536–539.
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Telfer, S., Pallari, J., Munguia, J., Dalgarno, K., McGeough, M., Woodburn, J., 2012b. Embracing additive manufacture: implications for foot and ankle orthosis design. BMC Musculoskeletal Disorders 13, 84. Turner, D.E., Helliwell, P.S., Siegel, K.L., Woodburn, J., 2008. Biomechanics of the foot in rheumatoid arthritis: identifying abnormal function and the factors associated with localised disease “impact”. Clinical Biomechanics 23, 93–100. Turpin, K.M., De Vincenzo, A., Apps, A.M., Cooney, T., MacKenzie, M.D., Chang, R., Hunt, M.A., 2012. Biomechanical and clinical outcomes with shock absorbinginsoles in patients with knee osteoarthritis: immediate effects and changes after one month of wear. Archives of Physical and Medicine and Rehabilitation 93, 503–508. White, R., Agouris, I., Selbie, R.D., Kirkpatrick, M., 1999. The variability of force platform data in normal and cerebral palsy gait. Clinical Biomechanics 14, 185–192. Winter, D.A., 1990. The Biomechanics and Motor Control of Human Movement. John Wiley and Sons Ltd., New York.
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Woodburn, J., Helliwell, P.S., Barker, S., 2002a. Three-dimensional kinematics at the ankle joint complex in rheumatoid arthritis patients with painful valgus deformity of the rearfoot. Rheumatology 41, 1406–1412. Woodburn, J., Udupa, J.K., Hirsch, B.E., Wakefield, R.J., Helliwell, P.S., Reay, N., O'Connor, P., Budgen, A., Emery, P., 2002b. The geometric architecture of the subtalar and midtarsal joints in rheumatoid arthritis based on magnetic resonance imaging. Arthritis and Rheumatism 46, 3168–3177. Woodburn, J., Helliwell, P.S., Barker, S., 2003. Changes in 3D joint kinematics support the continuous use of orthoses in the management of painful rearfoot deformity in rheumatoid arthritis. Journal of Rheumatology 30, 2356–2364. Williams, D.S., Davis, I.M., Baitch, S.P., 2003. Effect of inverted orthoses on lowerextremity mechanics in runners. Medicine and Science in Sports and Exercise 35, 2060–2068. Zifchock, R.A., Davis, I., 2008. A comparison of semi-custom and custom foot orthotic devices in high- and low-arched individuals during walking. Clinical Biomechanics 23, 1287–1293.
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Dose–response effects of customised foot orthoses on lower limb kinematics and kinetics in pronated foot type Scott Telfer n, Mandy Abbott, Martijn P.M. Steultjens, James Woodburn Institute for Applied Health Research, School of Health and Life Sciences, Glasgow Caledonian University, UK
art ic l e i nf o
a b s t r a c t
Article history: Accepted 30 March 2013
Despite the widespread use of customised foot orthoses (FOs) for the pronated foot type there is a lack of reliable information on the dose–response effect on lower limb mechanics. This study investigated these effects in subjects with normal and pronated foot types. Customised FOs were administered to 12 participants with symptomatic pronated foot type and 12 age and gender matched controls. A computeraided design (CAD) software was used to design nine FOs per participant with dose incrementally changed by varying only the rearfoot post angle. This was done in 21 increments from 61 lateral to 101 medial posting. A 3D printing method was used to manufacture the FOs. Quantification of the dose– response effect was performed using three-dimensional gait analyses for selected rearfoot and knee kinematics and kinetics. Under these experimental conditions, significant and linear effects of posting were seen for the peak (po 0.001) and mean (po0.001) rearfoot eversions, peak (p¼ 0.003) and mean (po 0.001) ankle eversion moments and peak (p¼0.017) and mean (p¼0.005) knee adduction moment variables. Group effects were observed for the peak (p ¼0.007) and mean (p¼ 0.007) forefoot abduction and for the peak (p ¼0.007) knee adduction moment. A significant interaction between posting and group was seen for internal tibial rotation (p ¼0.004). These data indicate that a dose–response effect, with a linear trend for both the rearfoot and knee, exists for customised FOs used to treat pronated foot type. & 2013 Elsevier Ltd. All rights reserved.
Keywords: Foot Orthoses Gait analysis Multisegment foot 3D printing
1. Introduction Foot orthoses (FOs) are an effective intervention to reduce rearfoot eversion (Cheung et al., 2011). The biomechanical mode-ofaction is achieved by incorporating medial wedges (or posts) and/or a contoured medial longitudinal arch on the FO (Brown et al., 1995; Nawoczenski et al., 1995; Woodburn et al., 2003; Nester et al., 2003; MacLean et al., 2006; Davis et al., 2008). These components have been used alone or in combination on flat insoles, pre-fabricated, and custom-made FOs (Eng and Pierrynowski, 1994; Stacoff et al., 2000; Mündermaan et al., 2003; Nigg et al., 2003; Nester et al., 2003; Woodburn et al., 2003; Ferber and Benson, 2011). Their design specifications provide the indicative dose either through the height or angle of the wedge or arch contour (Johanson et al., 1994; Nawoczenski et al., 1995; Stacoff et al., 2000; MacLean et al., 2006; Zifchock and Davis, 2008). Using calcaneal eversion as a proxy measurement of foot pronation, a recent meta-analysis has demonstrated that FOs are an effective anti-pronation intervention (Cheung et al., 2011). n Corresponding author at: Institute for Applied Health Research, School of Health and Life Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, UK. Tel.: +44 141 331 8475. E-mail addresses: [email protected], [email protected] (S. Telfer).
0021-9290/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbiomech.2013.03.036
The outcome is a kinematic measurement and mechanical or therapeutic targets have included reduced peak eversion (or subterms such as pronation) (Bates et al., 1979; Johanson et al., 1994; Brown et al., 1995; Leung et al., 1998; Genova and Gross, 2000; Stacoff et al., 2000; Williams et al., 2003; Mündermaan et al., 2003; MacLean et al., 2006; Zifchock and Davis, 2008; Eslami et al., 2009; Ferber and Benson, 2011), and eversion/inversion moment (Novick and Kelley, 1990; Mündermaan et al., 2003; Williams et al., 2003; MacLean et al., 2006). It should be noted however that the mean reduction in rearfoot eversion determined by the metaanalysis was around 21, and it has been questioned whether changes of this magnitude are a sufficient change to alter the basic biomechanics of gait (Nigg, 2001). Whilst efficacy has been demonstrated for a single dose, to the best of our knowledge there is no reliable information on the dose–response effect of antipronation FOs on lower limb kinematics and kinetics. The lack of evidence for dose–response is not surprising. These studies are difficult and costly to conduct. The largest potential barrier is hand fabrication and the ability to control and standardise the dose of the anti-pronation orthotic components such as medial heel wedges. These can now be largely overcome with advances in computer-aided design and manufacturing technologies (CAD/CAM). Components such as medial heel wedges and arch height can be specified within 7 11/1 mm. These components
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Fig. 1. Extrinsic rearfoot posting in computer aided design foot orthoses (FOs), left: laterally posted FO (green); centre: neutrally posted FO; and right: medially posted FO (green). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
can be incrementally changed on multiple CAD designs for the same standard or subject-specific FO shell. The level of customisation required to achieve an optimised mechanical response associated with therapeutic benefit is poorly understood (Menz, 2009). Reliable data on dose–response may form the basis of determining how much FO customisation is necessary to treat pronated foot type, and in addition may enable a better understanding of any potentially beneficial or harmful mechanical response at the rearfoot as well as the knee and hip where effects have been previously demonstrated (Mündermaan et al., 2003; Williams et al., 2003; Eslami et al., 2009; Chen et al., 2010). This study aims to investigate the dose–response effect of customised FOs on lower limb and foot mechanics in subjects with normal and pronated foot types. The study will exploit new capabilities in CAD-CAM technologies to incrementally change the dose of the external rearfoot post-design feature (Fig. 1). Our primary hypothesis is that by progressively altering the angle of the rearfoot post on a personalised FO design, there will be a significant and linear effect on the kinematics and kinetics of the lower limb during the stance phase. In addition, we hypothesise that there will be significant differences in response between symptomatic pronated foot types and asymptomatic normal foot types.
2. Materials and methods 2.1. Participants Ethical approval for this study was granted by the local National Health Service Ethics Committee (reference: 10/S0703/73). In total 24 participants were enroled in the study, 12 in the patient group and 12 age and gender matched controls. Group demographics are presented in Table 1. All participants provided informed, written consent upon enrolment into the study. Potential participants were recruited from local podiatry centres. Participants were eligible for inclusion if they had a pronated foot type as defined by the Foot Posture Index (FPI) (Redmond et al., 2006), a relaxed calcaneal stance position (RCSP) 441 everted; a current history of self-reported foot and ankle pain; and where their foot condition indicated a custom FO treatment. Control participants were eligible for inclusion if they had a normal foot type as defined by the FPI, a RCSP ≤41 everted, and no current or significant past-history of a diagnosable musculoskeletal, rheumatological or orthopaedic disorder of the lower limb or foot.
2.2. Foot orthoses All FOs used in this study were 3/4 length semi-rigid devices which were designed, based on a 3D surface scan of the foot, using an OrthoModel software (Delcam, Birmingham, UK) through a previously described and validated protocol (Telfer et al., 2012a). FOs were fabricated using a three-dimensional (3D) printing system (RapMan; Bits from Bytes, Clevedon, UK) in polylactide (PLA). Preliminary testing for this study showed that the PLA devices were of similar flexibility ( o 10% difference) to equivalent polypropylene devices based on arch displacement under a standard load.
Table 1 Participant demographics for patient and control groups.
Gender Age (years) Weight (kg) Height (m) Relaxed calcaneal stance position (deg) Foot posture index
Patient
Control
6F/6M 287 7.3 72.8 7 12.3 1.737 0.07 6.8 7 0.7 6.8 7 0.9
6F/6M 31.7 7 10 70.37 9.1 1.69 7 0.09 2.7 7 1.4 1.8 7 0.9
Reported as mean 7 SD
2.3. Protocol Participants were assessed by a UK Health and Care Professions Council registered podiatrist (MA) to ensure they met the inclusion criteria. Weightbearing 3D surface scans of both feet were taken with the foot held in a subtalar joint neutral position. The 3D scan file was uploaded to the CAD software and participant-specific FOs designed and manufactured as described above. The FO devices were fitted to the patient by the podiatrist to ensure satisfactory immediate fit and comfort for use. A schedule was provided to standardise FO device accommodation and use over a 14-day period. Nine variations on the original FO CAD design for one foot – the symptomatic side for the patient group if they had unilateral pain or randomly chosen for those with bilateral pain and controls – were produced and manufactured. In these variations on the original design, the level of the external rearfoot post was varied from 61 lateral to 101 medial in 21 increments. Approximately 2 weeks after fitting and having successfully introduced the original pair of FOs into daily wear, the participant returned to the laboratory for the main evaluation. Retroflective markers were attached to their test leg and pelvis in order to define a unilateral marker model which included the pelvis, thigh, shank, rearfoot, forefoot and full foot segments. A full description of the marker model is provided in the Supplementary materials. Footwear was standardised, with all participants wearing a modified pair of neutrally posted training shoes with holes cut at relevant landmarks to allow the markers to be directly attached to the foot. The trainers also had zips sewn into the sides to allow the trainers to be donned and doffed without requiring the removal of markers from the foot as this has previously been demonstrated to be the source of error in this type of experiment (Telfer et al., 2010). Further information on the footwear used is also provided in the Supplementary materials. For all gait trials, a 12 camera motion capture system (Qualysis AB, Gothenburg, Sweden) was used to track the retroreflective markers at a frequency of 120 Hz, and a force plate embedded into the walkway was used to measure ground reaction forces at 2400 Hz. A static trial was recorded with the participant standing barefoot followed by anatomical markers being removed. Walking trials were repeated for shod only and the nine FO conditions. The non-test foot used the same FO designed to the previously determined prescription during all FO test conditions. The testing order was randomised for each participant to avoid order effects, and researchers and participants were blinded to the posting level of the FO during testing and data processing. Participants were given time to acclimatize to each new condition until they were comfortable and a consistent gait pattern was visually observed by the researchers. They were then asked to walk along the motion capture walkway until at least seven clean strikes on the force plate with the foot of interest were recorded. Walking speed was controlled to 7 5% of the participant's predetermined self selected speed and trials outside these limits rejected. To reduce potential fatigue effects, a rest period of approximately 2 min was given after each set of walking trials while the FO was changed.
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2.4. Analysis A core set of clinically meaningful kinematic and kinetic variables were identified as those which form mechanical therapeutic targets for FO interventions, and the analysis was limited to these variables. These were: the peak and mean rearfoot (RF) eversions; peak and mean external ankle eversion moments; peak and mean forefoot (FF) abductions; peak and mean internal tibial rotations; peak knee external adduction moment during the first 50% of stance phase (1KAM); peak knee external adduction moment during final 50% of stance phase (2KAM); and mean knee external adduction moment (mean KAM). All data processing was carried out using a Visual 3D software (C-Motion Inc., Germantown, MD). The mean of the final five walking trials from each test condition with complete marker tracking was used in the analysis. Data were low pass filtered at 6 Hz (Winter, 1990). Kinematic variables were anatomically referenced to the proximal segment with the exception of internal tibial rotation which was referenced to the rearfoot. Kinetic variables were anatomically referenced to the proximal segment. For analysis, all variables were defined relative to the shod condition, which was considered the baseline for this study. The two way mixed effect ANOVAs were performed to determine if the effects of the FO posting and the foot type were significant at α ¼ 0.05 level. Where significant effects of the FO was found, linear, quadratic and cubic contrasts were tested to determine if there was a linear trend to the effect.
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Significant, linear main effects (P o0.001) were found for posting level in both the RF eversion peak and RF eversion mean, with a mean reduction of 0.261 (SD 0.11) and 0.281 (SD 0.141) per 21 of posting in the medial direction respectively. No effect was found for the group. Similarly, the ankle eversion moment peak and mean were significantly affected by posting level (p ¼0.003 and po 0.001), with FOs reducing the moments by 1.1% (SD 1.1%) and 2.3% (SD 2.1%) per 21 of posting in the medial direction respectively. Significant main effects were found at the knee for posting level in 2KAM and mean KAM (p ¼0.017 and p ¼0.005 respectively), along with a significant group effect for 2KAM. Posting effects for 2KAM were equivalent to increases of 1.1% (SD 1.1%) for the patient group and 0.9% (SD 1.1%) for the control group per 21 of posting in the medial direction, and for mean KAM a 1.4% (SD 1.1%) increase per 21 medial posting in the medial direction. Motion/moment time curves and individual participant responses for variables which were found to show a significant linear effect are provided in Supplementary materials.
3. Results
4. Discussion
The full results for all variables tested are presented in Table 2 and significant results are presented graphically in Figs. 2 and 3 for kinematic and kinetic results respectively. The only significant interaction between posting level and group was for internal tibial rotation mean (p¼ 0.004; linearity p¼ 0.003). The FF adduction peak and mean showed significant main effects for the group (both p ¼0.007), and FF adduction mean also showed significant main effects for posting level (p ¼0.049), however this trend was non-significant for linear, quadratic or cubic contrasts.
The aim of this study was to investigate the dose–response effect of custom FOs on lower limb mechanics in pronated foot type. Our findings suggest that when the rearfoot post of a custom FO is incrementally changed there is a linear mechanical response observed at the rearfoot and knee joint. Moreover, this response can be observed in both individuals with and without pronated foot type. These results confirm and extend our knowledge and understanding of the mechanical effects of custom FOs for pronated foot type.
Table 2 Two way mixed effects ANOVA for kinematic and kinetic variables.
Peak RF eversion
Mean RF eversion
Peak FF abduction
Mean FF abduction
Peak internal tibial rotation
Mean internal tibial rotation
Peak ankle eversion moment
Mean ankle eversion moment
Peak KAM (1st)
Peak KAM (2nd)
Mean KAM
Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group Posting Group
Wilks' Lambda
F
p-value
Partial eta squared
Best contrast
Trend per 21 posting lateral to medial
0.087 – 0.721 0.114 – 0.724 0.509 – 0.572 0.413 – 0.641 0.616 – 0.501 0.475 – 0.278 0.271 – 0.689 0.202 – 0.425 0.436 – 0.815 0.348 – 0.563 0.284 – 0.751
19.748 1.704 0.725 14.503 5.402 0.716 1.806 8.756 1.404 2.662 8.679 1.05 1.169 1.735 1.867 2.074 3.261 4.876 5.054 0.032 0.845 7.419 0.01 2.538 2.424 0.713 0.426 3.51 8.89 1.456 4.721 4.016 0.621
o0.001 0.205 0.668 o0.001 0.364 0.675 0.154 0.007 0.272 0.049 0.007 0.444 0.377 0.201 0.141 0.106 0.085 0.004 0.003 0.86 0.579 o0.001 0.92 0.057 0.066 0.408 0.888 0.017 0.007 0.253 0.005 0.058 0.748
0.913 0.072 0.279 0.886 0.038 0.276 0.491 0.285 0.428 0.587 0.283 0.359 0.384 0.073 0.499 0.525 0.129 0.722 0.729 0.001 0.311 0.789 40.001 0.575 0.564 0.031 0.185 0.652 0.288 0.437 0.716 0.154 0.249
Linear (Po 0.001) – – Linear (Po 0.001) – – – – – Cubic (p ¼ 0.251) – – – – – – – Linear (p¼ 0.003) Linear (po 0.001) – – Linear (po 0.001) – – – – – Linear (po 0.001) – – Linear (po 0.001) – –
−0.261 – – −0.281 – – – – – – – – – – – – – – −0.02 (% BW H) – – −0.016 (% BW H) – – – – – 0.018 (C); 0.015 (P); % BW H – – 0.015 (% BW H) –
Significant values have been highlighted in bold. RF: rearfoot; FF: forefoot; KAM: external knee adduction moment; C: control group; and P: patient group.
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Fig. 2. Kinematic results, RF: rearfoot; FF: forefoot; tib rot: tibial rotation; SE: standard error; nL: degrees laterally posted; 0N: neutrally posted; and nM: degrees medially posted.
Reducing calcaneal eversion is a viable and achievable biomechanical target (Cheung et al., 2011). Although current evidence for a link between increased motion control for individuals with pronated foot types and reduced injury rates in sports is weak (Ryan et al., 2011), in inflammatory conditions such as rheumatoid arthritis it has been strongly hypothesised that the acquired flat foot and excessive rearfoot motion regularly seen in these patients (Turner et al., 2008; Woodburn et al., 2002a) are related to ultrasound and MRI confirmed features of joint and tendon damage, particularly those involved in controlling the frontal plane motion of the foot (Dubbeldam et al., 2013; Woodburn et al., 2002b). While the direction of cause and effect has not been fully determined, there is good evidence from randomised controlled trials that an early intervention using customised FO devices results in reduced abnormal kinematics and improved patient reported outcomes (Hennessy et al., 2012; Woodburn et al., 2003). The findings from the present study suggest that there may be a potential to optimise FO design for biomechanical outcomes using dose response information at the individual patient level. Customised FOs have been shown to alter frontal plane rearfoot kinematics (Brown et al., 1995; Genova and Gross, 2000; Branthwaite et al., 2004; Woodburn et al., 2003; Davis et al., 2008; Zifchock and Davis., 2008) and frontal plane ankle complex kinetics (Pascual Huerta et al., 2009; Nester et al., 2003) during
walking. This study provides a new evidence of a clear and linear “dose–response” effect for external rearfoot posts around the frontal plane of the ankle complex. Previous studies have reported unsystematic rearfoot eversion responses to FO interventions (Stacoff et al., 2000). While there was some variation in the dose responses found in the present study, there was a consistent direction of effect across all participants and the majority (485%) showed a dose response within 0.151 of the mean (see Supplementary materials). The neutrally posted devices tended to reduce rearfoot eversion by approximately 21, which is in line with recent metaanalysis results (Cheung et al., 2011), with the 81 and 101 medially posted devices achieving reductions for peak rearfoot eversion of up to 41 in the group with pronated foot type. The overall range of the dose response for kinematic variables across the FO conditions around the neutral posting response was 2–2.51. Whether this potential range is clinically relevant in terms of preventing and treating impairments associated with pronated foot type is unclear. Based on existing knowledge, we would have expected the laterally posted devices to have shown an increase in rearfoot eversion variables, both kinematic and kinetic (Nester et al., 2003). The results presented here demonstrate that for this type of device this was not the case. Our hypothesis for this unexpected result is that, beyond the effects of posting, the contoured medial arch of the orthoses provided a significant support to the foot which
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Fig. 3. Results for kinetic variables, KAM: knee adduction moment; % BW H: % bodyweight multipled by height; SE: standard error; nL: degrees laterally posted; 0N: neutrally posted; nM: degrees medially posted; C: control group; and P: patient group.
prevented deformation of the medial longitudinal arch during dynamic function and thus reduced overall levels of pronation. The similar trends for both peak and mean variables suggest that the effect of the FO is to control and support the position of the foot throughout the full stance phase and this is also demonstrated in the motion time curves (see Supplementary materials). Functionally, we would expect the trend seen for reduced kinematic rearfoot eversion to be mirrored by similar trends for ankle eversion moment across the full stance phase and this was supported by the findings from this study. It should be noted that the between subject variability seen for kinetic measurements was generally larger than for kinematic measurements, and this may reflect the increased difficultly in reliably measuring these variables. Further work is required to determine if the relative reductions in eversion moments seen are clinically relevant. Recent work by Liu et al. (2012) has suggested that individual variability relating to the effect of FOs on tibial rotation which has been noted in a number of previous studies (McPoil and Cornwall, 2000; Mündermaan et al., 2003; Stacoff et al., 2000), may be due to the orthotic effects being accommodated at the ankle rather than the subtalar joint. This is supported by the lack of a systematic main effect of posting level on internal tibial rotation that was found in the current study, with our results suggesting that foot type does not allow individuals who respond to FO interventions by reducing internal tibial rotation to be identified. This study suggests that customised FOs of this type have a significant effect on the external knee adduction moment, with MKAM and 2KAM both increasing with medial posting. In the control group, even the laterally posted devices tended to cause increases in these variables. Elevated KAMs have been linked to the development and progression of medial compartment knee osteoarthritis (Miyazaki et al., 2002) and indeed the aim of many
FO interventions for this disease is based around unloading the medial compartment (Hinman et al., 2012). The proposed mechanism for these interventions is that the centre of pressure is shifted laterally, reducing the knee adduction moment arm (Gélis et al., 2008), however the most commonly used devices for this purpose are full length flat wedges without a medial arch support (Bennell et al., 2011). Clinicians should be aware that when prescribing the type of FO used in the current study for foot or ankle problems, an unintended consequence may be the device's tendency to increase the KAM, particularly in normal foot types, and that the KAM will further increase with greater levels of medial posting. Furthermore, these results suggest that the mechanical effects and outcome of this FO should be investigated in medial knee osteoarthritis patients who have normal foot types. The test devices used in the study were customised to the participant; however the use of CAD meant that the modifications could be made in a highly repeatable manner. The use of recently developed low cost printing systems for fabricating FOs has previously been proposed (Telfer et al., 2012b) however to our knowledge this is the first study to utilise the technique for a research study involving a patient group. There are a number of limitations with this study. Primary among these was the fact that only short term FO mechanical response was tested. There is some evidence, particularly at the knee, that biomechanical effects of orthotic interventions may change over wear periods of several weeks (Turpin et al., 2012). The participants in this study did wear the pre-test devices for a period of at least 1 week prior to the main evaluation, so arguably they were familiarised to wearing FOs, however it is unclear whether the variations on this design which were evaluated in the gait laboratory would have had different effects on the participant over an extended period of wear. Other limitations are related to well-recognised sources of measurement error associated with multi-segmented foot kinematics.
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These include the natural variation in gait (White et al., 1999) and the use of skin mounted markers (Nester et al., 2007). Holes were also cut in the shoes, including one at the heel counter, to allow markers to be attached directly to the foot and this may have affected the mechanical properties of the footwear. The markers remained in-situ between test-conditions in a single session to limit intra-subject variation. As this was an exploratory study, a large number of variables were tested. While the majority of significant results were consistent (for example both mean and peak rearfoot eversion showed similar trends) and were supported by previous reports in the literature, it is possible that some significant findings are due to chance. This study tested 3/4 length semi-rigid FOs produced using a CAD software, and caution is advised before extrapolating these results to other types of FO with different design features. Further research is required to determine the biomechanical response in other postural and pathological foot types and under different test conditions such as running. In conclusion, this study has demonstrated that, at a group level, there is a strong linear dose–response effect for frontal plane kinematics of the rearfoot, and frontal plane kinetics of the ankle and knee. There were significant differences between groups at the knee and forefoot.
Conflict of interest statement The authors declare that they have no conflict of interest relating to the material presented in this article.
Acknowledgements This work was funded through the European Commission Framework Seven Program (Grant No. NMP2-SE-2009-228893) as part of the A-FOOTPRINT Project (www.afootprint.eu). The funders had no input in the study design, collection, analysis and interpretation of data; the writing of the manuscript; or the decision to submit for publication.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.jbiomech.2013.03.036.
References Bates, B.T., Osternig, L.R., Mason, B., James, L.S., 1979. Foot orthotic devices to modify selected aspects of lower extremity mechanics. American Journal of Sports Medicine 7, 338–342. Bennell, K.L., Bowles, K.-A., Payne, C., Cicuttini, F., Williamson, E., Forbes, A., Hanna, F., Davies-Tuck, M., Harris, A., Hinman, R.S., 2011. Lateral wedge insoles for medial knee osteoarthritis: 12 month randomised controlled trial. British Medical Journal 342, d2912. Branthwaite, H.R., Payton, C.J., Chockalingam, N., 2004. The effect of simple insoles on three-dimensional foot motion during normal walking. Clinical Biomechanics 19, 972–977. Brown, G.P., Donatelli, R., Catlin, P.A., Wooden, M.J., 1995. The effect of two types of foot orthoses on rearfoot mechanics. Journal of Orthopaedic and Sports Physical Therapy 21, 258–267. Chen, Y.C., Lou, S.Z., Huang, C.Y., Su, F.C., 2010. Effects of foot orthoses on gait patterns of flat feet patients. Clinical Biomechanics 25, 265–270. Cheung, R.T., Chung, R.C., Ng, G.Y., 2011. Efficacies of different external controls for excessive foot pronation: a meta analysis. British Journal of Sports Medicine 45, 743–751. Davis, I.S., Zifchock, R.A., Deleo, A.T., 2008. A comparison of rearfoot motion control and comfort between custom and semicustom foot orthotic devices. Journal of the American Podiartic Medicine Association 98, 394–403. Dubbeldam, R., Baan, H., Nene, A.V., Drossaers-Bakker, K,W., van-de-Laar, M.A., Hermens, H.J., Buurke, J.H., 2013. Foot and ankle kinematics in rheumatoid
arthritis: influence of foot and ankle joint and leg tendon pathologies. Arthritis Care and Research 65, 503–511. Eng, J.J., Pierrynowski, M.R., 1994. The effect of soft foot orthotics on threedimensional lower-limb kinematics during walking and running. Physical Therapy 74, 836–844. Eslami, M., Begon, M., Hinse, S., Sadeghi, H., Popov, P., Allard, P., 2009. Effect of foot orthoses on magnitude and timing of rearfoot and tibial motions, ground reaction force and knee moment during running. Journal of Science and Medicine in Sport 12, 679–684. Ferber, R., Benson, B., 2011. Changes in multi-segment foot biomechanics with a heat-mouldable semi-custom foot orthotic device. Journal of Foot and Ankle Research 21, 18. Gélis, A., Coudeyre, E., Hudry, C., Pelissier, J., Revel, M., Rannou, F., 2008. Is there an evidence-based efficacy for the use of foot orthotics in knee and hip osteoarthritis? Elaboration of French clinical practice guidelines. Joint Bone Spine 75, 714–720. Genova, J.M., Gross, M.T., 2000. Effect of foot orthotics on calcaneal eversion during standing and treadmill walking for subjects with abnormal pronation. Journal of Orthopaedic and Sports Physical Therapy 30, 664–675. Hennessy, K., Woodburn, J., Steultjens, M.P., 2012. Custom foot orthoses for rheumatoid arthritis: a systematic review. Arthritis Care and Research 64, 311–320. Hinman, R.S., Bowles, K.A., Metcalf, B.B., Wrigley, T.V., Bennell, K.L., 2012. Lateral wedge insoles for medial knee osteoarthritis: effects on lower limb frontal biomechanics. Clinical Biomechanics 27, 27–33. Pascual Huerta, J., Ropa Moreno, J.M., Kirby, K.A., García Carmona, F.J., Orejana García, A.M., 2009. Effect of 7-degree rearfoot varus and valgus wedging on rearfoot kinematics and kinetics during the stance phase of walking. Journal of the American Podiatric Medical Association 99, 415–421. Johanson, M.A., Donatelli, R., Wooden, M.J., Andrew, P.D., Cummings, G.S., 1994. Effects of three different posting methods on controlling abnormal subtalar pronation. Physical Therapy 74, 149–158. Leung, A.K., Mak, A.F., Evans, J.H., 1998. Biomedical gait evaluation of the immediate effect of orthotic treatment for flexible flat foot. Prosthetics and Orthotics International 22, 25–34. Liu, A., Nester, C.J., Jones, R.K., Lundgren, P., Lundberg, A., Arndt, A., Wolf, P., 2012. Effect of an antipronation foot orthosis on ankle and subtalar kinematics. Medicine and Science in Sports and Exercise 44, 2384–2391. MacLean, C., Davis, I.M., Hamill, J., 2006. Influence of a custom foot orthotic intervention on lower extremity dynamics in healthy runners. Clinical Biomechanics 21, 623–630. McPoil, T.G., Cornwall, M.W., 2000. The effect of foot orthoses on transverse tibial rotation during walking. Journal of the American Podiatric Medical Association 90, 2–11. Menz, H.B., 2009. Foot orthoses: how much customisation is necessary? Journal of Foot and Ankle Research 2, 23. Miyazaki, T., Wada, M., Kawahara, H., Sato, M., Baba, H., Shimada, S., 2002. Dynamic load at baseline can predict radiographic disease progression in medial compartment knee osteoarthritis. Annals of Rheumatic Disease 61, 617–622. Mündermaan, A., Nigg, B.M., Humble, R.N., Stefanyshyn, D.J., 2003. Foot orthotics affect lower extremity kinematics and kinetics during running. Clinical Biomechanics 18, 254–262. Nawoczenski, D.A., Cook, T.M., Saltzman, C.L., 1995. The effect of foot orthotics on three-dimensional kinematics of the leg and rearfoot during running. Journal of Orthopaedic and Sports Physical Therapy 21, 317–327. Nester, C.J., van der Linden, M.L., Bowker, P., 2003. Effect of foot orthoses on the kinematics and kinetics of normal walking gait. Gait and Posture 17, 180–187. Nester, C.J., Jones, R.K., Liu, A., Howard, D., Lundberg, A., Arndt, A., Lundgren, P., Stacoff, A., Wolf, P., 2007. Foot kinematics during walking measured using bone and surface mounted markers. Journal of Biomechanics 40, 3412–3423. Nigg, B.M., 2001. The role of impact forces and foot pronation: a new paradigm. Clinical Journal of Sport Medicine 11, 2–9. Nigg, B.M., Stergiou, P., Cole, G., Stefanyshyn, D., Mündermaan, A., Humble, N., 2003. Effect of shoe inserts on kinematics, centre of pressure, and leg joint moments during running. Medical Science in Sports and Exercise 35, 314–319. Novick, A., Kelley, D.L., 1990. Position and movement changes of the foot with orthotic intervention during the loading response of gait. Journal of Orthopaedic and Sports Physical Therapy 11, 301–312. Redmond, A.C., Crosbie, J., Ouvrier, R.A., 2006. Development and validation of a novel rating system for scoring standing foot posture: the foot posture index. Clinical Biomechanics 21, 89–98. Ryan, M.B., Valiant, G.A., McDonald, K., Taunton, J.E., 2011. The effect of three different levels of footwear stability on pain outcomes in women runners: a randomised control trial. British Journal of Sports Medicine 45, 715–721. Stacoff, A., Reinschmidt, C., Nigg, B.M., van den Bogert, A.J., Lundberg, A., Denoth, J., Stüssi, E., 2000. Effects of foot orthoses on skeletal motion during running. Clinical Biomechanics 15, 54–64. Telfer, S., Gibson, K.S., Hennessy, K., Steultjens, M.P., Woodburn, J., 2012a. Computer-aided design of customized foot orthoses: reproducibility and effect of method used to obtain foot shape. Archives of Physical Medicine and Rehabilitation 93, 863–870. Telfer, S., Morlan, G., Hyslop, E., Semple, R., Rafferty, D., Woodburn, J., 2010. A novel device for improving marker placement accuracy. Gait and Posture 32, 536–539.
S. Telfer et al. / Journal of Biomechanics 46 (2013) 1489–1495
Telfer, S., Pallari, J., Munguia, J., Dalgarno, K., McGeough, M., Woodburn, J., 2012b. Embracing additive manufacture: implications for foot and ankle orthosis design. BMC Musculoskeletal Disorders 13, 84. Turner, D.E., Helliwell, P.S., Siegel, K.L., Woodburn, J., 2008. Biomechanics of the foot in rheumatoid arthritis: identifying abnormal function and the factors associated with localised disease “impact”. Clinical Biomechanics 23, 93–100. Turpin, K.M., De Vincenzo, A., Apps, A.M., Cooney, T., MacKenzie, M.D., Chang, R., Hunt, M.A., 2012. Biomechanical and clinical outcomes with shock absorbinginsoles in patients with knee osteoarthritis: immediate effects and changes after one month of wear. Archives of Physical and Medicine and Rehabilitation 93, 503–508. White, R., Agouris, I., Selbie, R.D., Kirkpatrick, M., 1999. The variability of force platform data in normal and cerebral palsy gait. Clinical Biomechanics 14, 185–192. Winter, D.A., 1990. The Biomechanics and Motor Control of Human Movement. John Wiley and Sons Ltd., New York.
1495
Woodburn, J., Helliwell, P.S., Barker, S., 2002a. Three-dimensional kinematics at the ankle joint complex in rheumatoid arthritis patients with painful valgus deformity of the rearfoot. Rheumatology 41, 1406–1412. Woodburn, J., Udupa, J.K., Hirsch, B.E., Wakefield, R.J., Helliwell, P.S., Reay, N., O'Connor, P., Budgen, A., Emery, P., 2002b. The geometric architecture of the subtalar and midtarsal joints in rheumatoid arthritis based on magnetic resonance imaging. Arthritis and Rheumatism 46, 3168–3177. Woodburn, J., Helliwell, P.S., Barker, S., 2003. Changes in 3D joint kinematics support the continuous use of orthoses in the management of painful rearfoot deformity in rheumatoid arthritis. Journal of Rheumatology 30, 2356–2364. Williams, D.S., Davis, I.M., Baitch, S.P., 2003. Effect of inverted orthoses on lowerextremity mechanics in runners. Medicine and Science in Sports and Exercise 35, 2060–2068. Zifchock, R.A., Davis, I., 2008. A comparison of semi-custom and custom foot orthotic devices in high- and low-arched individuals during walking. Clinical Biomechanics 23, 1287–1293.