2000 WILLIAM J. STICKEL SILVER AWARD
Effect of Cast and Noncast Foot Orthoses on Plantar Pressure and Force During Normal Gait Anthony Redmond, MSc, DPodM* Peter S.B. Lumb, B App Sc (Hons) Pod† Karl Landorf, Dip App Sc (Pod), Grad Dip Ed‡
A variety of plantar pressure and force measures were explored in 22 healthy individuals with excessive pronation. The measures were obtained while the subjects wore a thin-soled athletic shoe alone, a modified Root foot orthosis made from a neutral cast, and a flat noncast insole with a 6° varus rearfoot post. The data obtained from subjects wearing the noncast insole differed only minimally from those obtained while they were wearing the shoe only. In contrast, the modified Root orthosis had a profound effect on foot function. Heel forces and pressures were reduced, and the rearfoot contact area was increased. Measures of force in the midfoot demonstrated substantial increases in load in this region, but the increase in area associated with the contoured device resulted in no increase in midfoot pressure measurements. Forefoot pressures were reduced both medially and laterally with the cast device in place. (J Am Podiatr Med Assoc 90(9): 441-449, 2000)
A wide range of foot orthoses have been used for the management of lower-limb and foot pathologies since the late 19th century.1-4 In the latter part of the 20th century, significant developments in the understanding of the theory of foot function have led to a range of more sophisticated orthotic devices such as the University of California Biomechanics Laboratory (UC-BL) orthosis5 and the Root-style functional foot orthosis and its derivatives.6-8 The experience of most practitioners suggests that such devices help control foot pathology and associated symptoms. It must be recognized, however, that in spite of the anecdotal evidence, little scientific scrutiny has been *Lecturer, Division of Podiatry, University of Western Sydney, PO Box 555, Campbelltown, New South Wales 2560, Australia. †Private practice, Peakhurst, New South Wales, Australia. ‡Lecturer, Division of Podiatry, University of Western Sydney, Campbelltown, New South Wales, Australia.
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applied to determining the efficacy of the different types of orthoses in discrete conditions. Furthermore, the mode of action of foot orthoses is still poorly understood from a scientific point of view. Landorf and Keenan,9 in a recent comprehensive review, provided a useful summary of the evidence relating to the efficacy of foot orthoses. This review highlights the fact that while some inroads are being made into the investigation of the efficacy of foot orthoses, more information is needed before the effects of orthotic therapy can be adequately understood. Running parallel to this obvious need for research on the clinical effectiveness of orthoses is an urgent need for data relating to the mechanism of action and the physical consequences of orthotic therapy. A number of eminent, thoughtful, and articulate podiatrists have published a great deal of theory in the podiatric literature of the past 20 years, presenting compelling
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and coherent explanations for a variety of aspects of foot function and therapeutic mechanisms. It could be argued, however, that while the theory has contributed positively to the development of the current understanding of the mechanics of foot function—and, by extension, the interventions based on that function— there has been little emphasis on the testing of that theory through rigorous scientific experimental work. The net result is a range of competing theories but an inadequate body of hard data against which these promising theories can be tested. It is conceded, given the current level of technology, that the precise investigation of the complex intrinsic function of the foot is extremely difficult in living humans, but the need for such work is of paramount importance. This study was intended to address this lack of scientific data and focuses on the measurable consequences of altering foot function, with inferences drawn from these objective measures where appropriate. This study was performed to investigate the pressures and forces at the interface of the foot and the footwear or an intervening orthosis in order to determine the effect of orthotic intervention on the foot during normal walking. Several previous studies have investigated pressures and timing in the barefoot state and with various orthoses in place, using either platform-based systems or in-shoe systems.10-18 The effects of custom-molded orthoses on foot pressures have also been investigated by Bennett et al19 and Reed et al,20 although these data were confined mainly to peak pressures and the timing of events using a discrete sensor system. In 1991, McPoil and Cornwall21 also reported a single-subject evaluation of a rigid functional orthosis and a soft orthosis. The current study presents comprehensive data on a range of measures using two types of orthoses and for a shoeonly control state in a substantially larger sample.
Materials and Methods Subjects The study group consisted of 22 subjects (mean age, 24 years) with excessive pronation, but who were otherwise healthy. Subjects were chosen who were without significant congenital or traumatic foot or lower-limb pathology. Each potential participant was assessed for foot type according to the descriptions published in 1991 by Dahle et al22; those who were identified as having an excessively pronated, hypermobile foot type were included in the study. Prior to commencement of the study, approval was received from the Ethics Review Committee (Human Subjects) of the University of Western Sydney–Macarthur.
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Analysis Equipment The PEDAR (Novel Gmbh, Munich, Germany) in-shoe measurement system, with a sampling rate of 50 Hz, was used to collect plantar pressure and force data for each participant. A 10-m walkway was used at the gait-analysis facility at the University of Western Sydney, and participants completed three laps of the walkway in each test state. Acceleration, deceleration, and turning steps were eliminated during the data preparation following the test, yielding a mean of 14 steps per participant in each test state.
Footwear and Foot Orthoses The participants were assessed wearing, in random order, 1) a Dunlop Volley (Pacific Dunlop Ltd, Melbourne, Victoria) athletic shoe only, 2) a noncast insole in the athletic shoe, and 3) a modified Root foot orthosis in the athletic shoe. Dunlop Volley shoes with the insoles removed were chosen because their thin soles and lightweight construction were considered to have minimal influence on the interaction of the foot, the orthosis, and the in-shoe measurement system. Each subject was fitted with footwear of an appropriate size. The noncast insole consisted of a thin, non-shock-attenuating card template with a 6° rearfoot varus wedge made from high-density (400 kg/m3) ethyl-vinyl acetate. The modified Root foot orthosis was fabricated from a neutral cast of the foot obtained using the method described by Philps,23 whereby the subject was in a prone position, the talonavicular joint was palpated for maximum congruency, and the forefoot was stabilized against the rearfoot in the direction of pronation. The positive cast was balanced with the calcaneal bisection in a vertically oriented position. The device consisted of a 4mm, high-density polypropylene shell with a thin polyvinyl chloride top cover. Finally, an extrinsic 6° varus rearfoot post, also in high-density ethyl-vinyl acetate, was added. The degree of posting was standardized to limit the possibility of variation in prescription influencing the outcome; however, it is acknowledged that individual subjects will respond differently to a uniform degree of posting.
Procedure Potential subjects had their foot type assessed to identify hypermobile, excessively pronated feet. The variables of talonavicular bulging, arch height, resting calcaneal eversion, internal leg rotation, and forefoot abduction were included in the assessment. A nonweightbearing neutral plaster cast of each foot of each
Journal of the American Podiatric Medical Association
of the 22 subjects who met the study criteria was taken to be used for the construction of the modified Root foot orthosis. At this stage, a template was also made for the subsequent construction of the noncast insole. At a follow-up appointment, measurements were obtained using the PEDAR system while the participant completed three full lengths of a 9-m walkway in each of the three test states. All tests were performed with the individuals walking at their own comfortable pace. The order of the shoe-only and the two orthosis test states was randomly determined. Subjects were given a minimal acclimatization period for the two orthosis test states. Data from each test phase were entered into an IBM personal computer and were subsequently prepared and manipulated using the Novelwin software package, version 08.7 (Novel Gmbh, Munich, Germany). After the data had been prepared, a Novel percent mask was applied, dividing the foot into anatomically and functionally relevant regions, according to consistent proportional areas of each footprint (Fig. 1). Data from all mask areas except the lateral digits are presented in the “Results” section. Data from the lateral digits yielded low values, which proved highly variable. The potential error coupled with the limited importance of the lateral digit mask area led to its exclusion from the subsequent analysis.
Hallux
Lateral Digits
Data Analysis Raw data were exported from the Novel software into Microsoft Excel (Microsoft Corp, Redmond, Washington), and final statistical analysis was performed in SPSS for Windows, version 9.0 (SPSS Inc, Chicago, Illinois). The data were explored using appropriate descriptive and graphic techniques and each data set was examined for a normal distribution prior to conducting any inferential analysis. Some data (eg, maximum force and peak pressure in several mask areas) were negatively skewed, and all such skewed data were log10 transformed prior to analysis. Repeated measures analysis of variance was performed on all normal or normalized data sets, with adjusted pairwise comparisons to determine the significant interactions. Peak pressure at the medial forefoot and maximum force at the heel could not be transformed to a normal distribution and were analyzed using a Friedman nonparametric comparison of ranks. In these cases, the pairwise comparisons of potentially significant relationships employed the Wilcoxon signed rank test with a Bonferroni correction for multiple comparisons. The observed power was calculated for each of the variables. Statistically significant results for pressure and force data in the heel and midfoot mask areas all had powers above .98. Power for significant results in other mask areas ranged between .99 and .58. Statistical power was low (< .36) for all nonsignificant interactions. Data were analyzed for the following measures of function: maximum force, force-time integral, peak pressure, pressure-time integral, maximum mean pressure, and contact area.
Results Medial Forefoot
Lateral Forefoot
Midfoot
Prior to the full analysis, data for the left and right limbs were tested to determine whether any systematic differences could be detected. Ten combinations of variables and masks were selected and tested using Student t-tests. No significant differences were found between any of the right/left test pairs. Subsequently, all right and left data were pooled, yielding a sample size of 44. The results are presented by mask region, as this represents a functionally coherent template for the data and the subsequent discussion.
Heel
Heel
Figure 1. The six areas defined by the percent mask.
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The maximum force at the heel was approximately 42 N less in the foot orthosis state than in the other two
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states (8% reduction), and the force-time integral was similarly reduced (11%) (Table 1). All pressure-related variables were significantly lower in the foot orthosis state (14% to 21%), both as a consequence of the decreased force and owing to the significant increase in area associated with the foot orthosis.
Midfoot Both orthoses altered the maximum force occurring in the midfoot mask area (Table 2). The noncast insoles were associated with a moderate 39.1-N (20%) decrease in midfoot maximum force, while the foot orthosis increased the maximum force in the midfoot by 38.9 N when compared with the shoe-only state. The force-time integral was not significantly lowered
in the noncast insole state when compared with the shoe-only state, as the contact time for this area increased slightly. In contrast, the foot orthosis was associated with a highly significant 284.6-N • s (54%) increase in the force-time integral at the midfoot as the force applied, and the duration of application, both increased significantly. Pressure-related variables were lower in the orthosis states, despite the increased force with the foot orthosis because of an increase in the contact area of the midfoot in both orthosis states (pressure equals force divided by area). Contact area in the noncast insole increased by 5.7 cm2 (16%) and in the foot orthosis by 13.1 cm2 (38%). Consequently, peak pressure fell 33.4 kPa (15%) and 55.0 kPa (25%) in the noncast insole and foot orthosis states, respectively. The pres-
Table 1. Data for the Heel Mask Area Shoe Only
Noncast Insole
Foot Orthosis
544.5
543.8
501.9
Foot orthosis v shoe only (P = .001); foot orthosis v noncast insole (P = .001)
1436.2
1488.9
1285.0
Foot orthosis v shoe only (P = .03); foot orthosis v noncast insole (P = .016)
Peak pressure (kPa)
283.8
278.6
220.6
Foot orthosis v shoe only (P < .001); foot orthosis v noncast insole (P < .001)
Maximum mean pressure (kPa)
140.0
140.3
119.2
Foot orthosis v shoe only (P < .001); foot orthosis v noncast insole (P < .001)
Pressure-time integral (kPa • s)
783.0
796.0
640.0
Foot orthosis v shoe only (P < .001); foot orthosis v noncast insole (P < .001)
41.3
41.3
42.9
Foot orthosis v shoe only (P < .048); foot orthosis v noncast insole (P < .013)
Shoe Only
Noncast Insole
Foot Orthosis
Maximum force (N)
195.3
156.2
234.2
Foot orthosis v shoe only (P < .001); foot orthosis v noncast insole (P < .001); noncast insole v shoe only (P < .001)
Force-time integral (N • s)
527.7
454.4
812.3
Foot orthosis v shoe only (P = .001); foot orthosis v noncast insole (P = .001)
Peak pressure (kPa)
220.2
186.8
165.2
Foot orthosis v shoe only (P < .001); foot orthosis v noncast insole (P < .03); noncast insole v shoe only (P < .03)
Maximum mean pressure (kPa)
80.3
63.9
60.5
Pressure-time integral (kPa • s)
710.9
641.7
643.9
34.9
40.6
48.0
Maximum force (N) Force-time integral (N • s)
Contact area (cm2)
Statistically Significant Relationships
Table 2. Data for the Midfoot Mask Area
Contact area (cm2)
444
Statistically Significant Relationships
Foot orthosis v shoe only (P < .001); noncast insole v shoe only (P < .001) Not significant Foot orthosis v shoe only (P < .001); foot orthosis v noncast insole (P < .001); noncast insole v shoe only (P < .001)
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sure-time integral also fell slightly, although not significantly, in both orthosis states.
Lateral Forefoot Lateral forefoot maximum forces were altered from the shoe-only state by only 3.0 N with the addition of the 6° varus post noncast insole orthosis (Table 3). The maximum force in this area was reduced by 30.0 N (7%) in the case of the foot orthosis. Force-time integral results were similar, with the force-time integral essentially unchanged in the noncast insole state, and reduced by a significant 337.8 N • s (24%) in the foot orthosis state. Peak pressure was not significantly different in the three test states, but both types of orthoses significantly reduced the pressure-time integral. The noncast insole reduced the lateral forefoot pressure-time integral by 131.2 kPa • s (12%) and the foot orthosis reduced the pressure-time integral by 215.9 kPa • s(19%). As would be expected from devices that are cut posterior to the metatarsophalangeal joints, no significant differences were noted in the lateral forefoot contact area among the three states.
Medial Forefoot Maximum force in the medial forefoot was not significantly affected by the addition of orthoses to the footwear (Table 4). There was a trend toward a decrease in medial forefoot maximum force in the foot orthosis state, but this was not significant. The forcetime integral was, however, significantly reduced in the foot orthosis state compared with the other two states, falling 128.2 N • s (27%) from the shoe-only state. Peak pressures followed a similar pattern to the maximum force data, with a slight but insignificant reduction in the foot orthosis state. The pressure-time integral followed the trend seen in the force-time integral data for this mask and was 160.1 kPa (19%) lower in the foot orthosis state than in the shoe-only state. As with results in the lateral forefoot, the contact area was similar across all three states.
Hallux There were no significant differences for the hallux in any of the pressure or force variables among the test states except for a marked 31% increase in peak pres-
Table 3. Data for the Lateral Forefoot Mask Area Shoe Only Maximum force (N)
Noncast Insole
Foot Orthosis
Statistically Significant Relationships
426.9
429.9
396.9
1394.7
1317.0
1056.9
Peak pressure (kPa)
326.3
295.9
322.5
Maximum mean pressure (kPa)
158.5
155.3
145.6
Foot orthosis v shoe only (P = .02)
Pressure-time integral (kPa • s)
1107.7
976.5
891.8
Shoe only v foot orthosis (P = .002); shoe only v noncast insole (P < .008)
28.3
28.5
28.6
Force-time integral (N • s)
Contact area (cm2)
Foot orthosis v noncast insole (P = .02) Foot orthosis v shoe only (P = .001); foot orthosis v noncast insole (P = .008) Not significant
Not significant
Table 4. Data for the Medial Forefoot Mask Area Shoe Only
Noncast Insole
Foot Orthosis
Statistically Significant Relationships
Maximum force (N)
188.5
190.0
173.2
Not significant
Force-time integral (N • s)
468.5
423.5
340.3
Foot orthosis v shoe only (P < .001)
Peak pressure (kPa)
325.9
302.5
320.4
Not significant
Maximum mean pressure (kPa)
177.3
171.1
161.6
Not significant
Pressure-time integral (kPa • s)
840.1
760.0
680.0
Shoe only v foot orthosis (P = .001)
11.6
11.9
11.6
Contact area (cm2)
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Not significant
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sure, from 268.4 to 350.4 kPa, in the foot orthosis state (Table 5). Further examination of the data suggested that while there was an overall increase in peak pressure across the whole sample, there were in fact two apparent subgroups who responded differently to the foot orthosis intervention. In one group, peak pressures remained similar or fell, while a second apparently distinct group demonstrated increases of up to 125%. The anomalous subgroup has since been recalled for further investigation, and a secondary study is now under way to attempt to determine the factors underlying the hallux response to foot orthoses. Until these studies are complete, it would not be appropriate to speculate further; in the meantime, however, these anomalies should be considered when interpreting the statistically nonsignificant findings of the homogeneous hallux data presented here.
Discussion The contoured, modified Root foot orthosis appears to affect the heel during gait by reducing the forces acting through the tissues in the area and also by spreading the applied load over a greater area. The reduction in peak heel pressures is in general agreement with the data of Albert and Rinoie,17 although the actual values obtained in the current study were higher in both the shoe-only and orthosis states, and the magnitude of the differences was substantially less. If it is assumed that the body mass remains essentially constant during the course of the trials, the observed reduction in force is likely to be a product of some attenuation of the rapid deceleration of heel strike. The force and pressure data are valuable, particularly when the substantial improvements in the foot orthosis state are compared with the minimal change associated with the noncast insole orthosis. This may suggest that the contoured orthosis may be preferable to flat noncast insoles in conditions where
reduction of force or pressure in the heel is required. The effects of adding an arch support to a flat noncast insole type of device are unknown, and further investigations are required to determine whether a custommade cast device is necessary when prescribing a contoured device, or whether off-the-shelf contoured insoles may have similar effects at the heel. It should also be noted that pathologies at the heel might be associated with causes other than direct local pressure or force, and that in these cases in particular, therapy with the flat noncast insole may not be contraindicated. The effect of the cast orthosis on the midfoot is profound. The 20% increase in maximum force and the 54% increase in force-time integral suggest that much of the effect of the cast device is derived from direct loading of the midfoot area. This loading also appears to be applied for a longer period, as the contoured arch of the modified Root orthosis maintains this part of the foot in weightbearing contact for a greater proportion of the stance phase. The closely fitted contours of the cast device result in those forces being spread evenly over the arch area with no significant change in pressure measures such as peak pressure and pressure-time integral and, hence, little risk of the subsequent development of superficial responses such as callus formation or ulceration. However, the finding that the foot orthosis loads an area that in evolutionary terms is not developed for direct weightbearing may have implications regarding the continuous and long-term use of such devices. This study suggests that while the intended effect of the modified Root orthosis is not simply to provide arch support, a significant proportion of its effect may be derived precisely from that fundamental arch-supporting function. The lateral and medial forefoot appear to respond similarly to the effects of the orthoses. The noncast insole had little effect on either medial or lateral measures of force. The pressure-time integral was slightly
Table 5. Data for the Hallux Mask Area Shoe Only
Noncast Insole
Foot Orthosis
Maximum force (N)
148.9
159.9
161.4
Not significant
Force-time integral (N â&#x20AC;˘ s)
294.9
317.7
304.6
Not significant
Peak pressure (kPa)
268.4
297.5
350.4
Foot orthosis v shoe only (P = .002); foot orthosis v noncast insole (P = .006)
Statistically Significant Relationships
Maximum mean pressure (kPa)
140.3
148.4
152.8
Not significant
Pressure-time integral (kPa â&#x20AC;˘ s)
752.9
684.7
726.3
Not significant
11.4
11.6
11.3
Not significant
Contact area (cm2)
446
Journal of the American Podiatric Medical Association
reduced in the lateral forefoot, but this effect was not substantial. Despite some theories regarding the mode of action of the noncast insole, there was no evidence of a shift in force laterally with the introduction of the wedged noncast insole. This finding is in agreement with the findings of Miller et al,24 who have previously questioned the existence of a mediolateral shift in ground-reaction force associated with rigid orthoses. In the case of the foot orthosis, the force and pressure measures fell on both the lateral and medial sides of the forefoot. There was a slightly greater reduction on the medial side than on the lateral side, but the compelling finding again is that the cast foot orthosis appears to act more through a shift of force posteriorly into the arch area than through a medialto-lateral shift in force. This could suggest that the effectiveness of this type of device in symptom relief and enhanced comfort in the forefoot may again be as much a product of its arch-supporting role as its effect on frontal-plane mechanics. Study of the timing of the loading of the foot following orthotic intervention, as discussed by Reed et al,20 supports the findings of the present study in this respect. The effect of either of the orthosis types on the lateral digits was minimal and so variable as to be effectively meaningless. The noncast insole orthosis also appeared to have no significant effect on any of the variables measured at the hallux. Conversely, the foot orthosis appeared to have some marked effects at the hallux, but not the effects that would have been predicted. As noted in the “Results” section, there was a varied and disturbingly unpredictable response to the cast foot orthosis. In those subjects in whom substantial increases in peak pressure were noted in the hallux region, these appeared on visual inspection of the graphic output to be confined to the first interphalangeal joints. Until the ongoing follow-up investigations are more advanced, it will not be possible to hypothesize in any informed way regarding these findings, but the effects of the foot orthosis on the sagittal-plane function of the first ray appear to present a promising line of inquiry. The data obtained during the course of this study are broadly in agreement with values reported in the current literature. There is a great deal of variation in the existing published values, and the inconsistent reporting of results relating to measures such as pressure-time integrals unfortunately precludes accurate cross-checking of such data. For more commonly reported values such as peak pressure, the data in this study are comparable with, but toward the low end of, reported values. This could result from some pressure reduction associated with even the thin-soled athletic shoe, variations between measuring systems,
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and the makeup of the sample. Nevertheless, the results clearly demonstrate that orthoses have the ability to alter foot function selectively. There remains a great deal more to learn about the mechanism by which orthoses may exert that effect, but the results in this instance appear clear. The effects of the two types of orthoses are significantly different in many respects and present a range of choices for the practitioner in making treatment decisions. Furthermore, the degree of observed difference between the results obtained from the two orthoses types appears to call into question the use of noncast insoles either as a test device or as an interim device prior to the later introduction of cast devices. In particular, the importance of the arch contour in the cast device cannot be dismissed, as it appears that this feature assists in decreasing loads and altering timings around the heel and forefoot, transferring these loads toward the arch. The changes in timing associated with foot orthotic therapies also warrant further investigation, as the sequence and duration of loading in the various segments are likely to alter profoundly the overall foot mechanics. This study employed a moderate sample size for this type of experiment (N = 44). The amount and complexity of the data and the associated analysis precludes the use of samples much larger than that reported on here, and 44 limbs can be considered a satisfactory sample. It would be useful, however, to compare these data with data from repeated experiments prior to making broad generalizations regarding the effects of foot orthoses on foot function.
Limitations of the Study The participants in this study had only a minimal period of acclimatization prior to the start of the testing process. It is likely that a longer acclimatization period may produce some differences in the subsequent results as the dynamic foot adapts over time to the intrusion of the orthotic device. The first ray follow-up study mentioned previously in the hallux results section is also being performed to examine the differences between the measures obtained at the first appointment and measures derived after a longer period of acclimatization. These data are not yet available but will be published in the future. This study divided the foot into six mask areas. The use of more mask areas may be considered desirable, as this increases the definition in terms of the components of foot function. However, adding more masks significantly affects the reliability of the data because the ratio of mask size to individual sensor size decreases. For the purposes of this study, six
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mask areas were considered to be an acceptable compromise, based on the resolution of the PEDAR system and the nature of the study. It should also be noted that the forces and pressures measured by in-shoe systems are not true vertical forces or pressures. Because the insole is forced to conform to variations in the contour of the shoe or orthosis, the recorded values represent resultant forces and pressures. As current in-shoe systems such as PEDAR are not able to measure the shear component of such forces, small degrees of error are inevitable with such systems. Finally, it must be acknowledged that any proposed relationships between measures such as plantar force or pressures and subsequent pathology remain theoretical. All of the participants in this study had pronated feet but were asymptomatic, and the degree to which the objective measures may correlate with the clinical evaluation of the resolution of symptoms has not been established. Consequently, comprehensive trials in clinical groups are essential in the future evaluation of foot orthotic therapies.
Conclusion The data presented here provide a clear picture of the implications of intrinsic foot function at the interface between the foot and the orthosis, and the foot and the shoe, in healthy young adults. The cast foot orthosis had a more profound effect on the foot than the flat noncast insole device tested in this study. Indeed, the effects of the noncast insole device were limited to decreasing the forces experienced in the medial arch area and to minor changes in forefoot loading. The amount of posting applied to the noncast insole (6°) was thought to be adequate to promote a measurable response, if one were evident while remaining within a clinically appropriate range. The results obtained from the foot orthosis data are in agreement with many of the theoretical explanations for this type of device, particularly with regard to their effects on the rearfoot and midfoot. The cast foot orthosis device appears to both reduce the loading of the rearfoot and increase the area over which the load is applied. On the basis of findings such as this, the role of contoured devices in managing heel pathology looks promising. Much remains to be discovered with regard to the effects of orthoses on the forefoot, and this study serves in part to highlight how superficial is our knowledge of foot function. Foot orthoses are widely used, and there is some evidence supporting their clinical effectiveness for a number of conditions. However, there is some potential for harm with any
448
treatment, and until more is understood about the effects of orthoses on the forefoot, some caution should be exercised in their use. Finally, the increased arch loading associated with the cast orthoses cannot be dismissed. While there is no doubt that today’s foot orthoses are substantially more sophisticated than the traditional arch support, there is some evidence that a significant part of the benefit to be derived from cast orthotic devices comes from precisely this capacity to support the medial arch and hence transfer load away from a painful forefoot or heel. This study serves to provide some useful scientific data regarding some of the consequences of foot orthotic therapy. It raises some interesting questions, suggests caution in some areas, and provides some of the theories of foot function with a more substantial base. Acknowledgment. Artisan Orthotic Laboratory, Perth, Western Australia, Australia, for its contribution of the cast functional orthoses used in this study; Amanda Taylor for preparing and exporting the raw data and the preliminary analyses. This study was supported in part by the Summer Scholarships program of the University of Western Sydney–Macarthur.
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19. B ENNETT PJ, M ISKEWITCH V, D UPLOCK LR: Quantitative analysis of the effects of custom-molded orthoses. JAPMA 86: 307, 1996. 20. REED L, BENNETT PJ, WHITHAM D: “Changes in Foot Function Using Two Orthotic Techniques: Root and Blake Devices,” in Proceedings of the 17th Australian Podiatry Conference, Vol 1, ed by AM Keenan, HB Menz, p 193, Australian Podiatry Council, Melbourne, 1996. 21. M C P OIL TG, C ORNWALL MW: Rigid versus soft foot orthoses: a single subject design. JAPMA 81: 638, 1991. 22. DAHLE LK, MUELLER M, DELITTO A, ET AL: Visual assessment of foot type and relationship of foot type to lower extremity injury. J Orthop Sports Phys Ther 14: 70, 1991. 23. PHILPS JW: The Functional Foot Orthosis, Churchill Livingstone, Edinburgh, 1995. 24. M ILLER CD, L ASKOWSKI ER, S UMAN VJ: Effect of corrective rearfoot orthotic devices on ground reaction forces during ambulation. Mayo Clin Proc 71: 757, 1996.
ERRATUM In “A Case of Peroneal Neuropathy–Induced Footdrop: Correlated and Compensatory Lower-Extremity Function” by Tracey C. Vlahovic, BS, Carla E. Ribeiro, BS, BA, Bradley M. Lamm, BS, et al, September 2000, page 418, Figure 7 A and B, the y-axis should read “Moment (N • m/kg),” not “Angle (°).”
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