PODIATRIC RESEARCH FROM THE UNITED KINGDOM
Effect of Orthotic Therapy on Claw Toe Loading Results of Significance Testing at Pressure Sensor Units Penny J. Claisse, BSc(Hons)* Jodi Binning, MSc† Julia Potter, PhD‡
This study demonstrates the effect of orthotic therapy for toe deformity on toe and metatarsal head pressures using a new analysis method facilitated by an in-shoe pressure-measurement system’s ability to export detailed data. Plantar pressure–time integrals in 11 individuals (22 feet) with claw deformity of the lesser toes were measured with and without toe props. Differences in pressure–time integrals at every individual sensor unit were then calculated for the two conditions, and significance was tested using the paired t-test. Plantar surface charts with contours of equal significant pressure–time integral change showed significant reduction under 17 second toes (77%), 22 third toes (100%), 15 fourth toes (68%), 13 second metatarsal heads (59%), 16 third metatarsal heads (73%), and 16 fourth metatarsal heads (73%). All 22 feet showed increases under the prop in the area of the third toe sulcus. This innovative approach to plantar pressure analysis could improve access to data that show significant pressure–time integral changes and, therefore, could advance the clinical application of plantar pressure measurement. (J Am Podiatr Med Assoc 94(3): 246-254, 2004)
Detailed analysis of plantar pressure measurements is a powerful and efficient technique complementary to the evaluation of foot function and therapeutic intervention. Current definition of plantar areas is by *Mid Hampshire Primary Care Trust and North Hampshire Primary Care Trust, Andover War Memorial Hospital, Andover, England. †New Generation Project, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, England. ‡Podiatry Research Group, School of Health Professions and Rehabilitation Sciences, University of Southampton, Southampton, England. Corresponding author: Penny J. Claisse, BSc(Hons), Mid Hampshire Primary Care Trust and North Hampshire Primary Care Trust, Andover War Memorial Hospital, Charlton Road, Andover, Hampshire SP10 3LB, England (e-mail: penny. claisse@btinternet.com).
246
subdivision into regions or “masks” yielding mean pressure values for comparison between areas of the foot, different conditions, and subjects.1, 2 However, interstudy comparability can be reduced by the use of widely varying masking methods, including subjective operator selection3 and predetermined software algorithm application.1 Small structures, deformities, and lesions are difficult to mask accurately,4, 5 and valuable individual sensor unit data are lost to artificially applied averaging and smoothing.4 An alternative analysis method is presented here. This analysis is driven by the requirement to increase definition of the significant plantar pressure changes closely associated with individual toes and metatarsal heads for clinical assessment of orthotic efficacy. We explore the use of pressure data from individ-
May/June 2004 • Vol 94 • No 3 • Journal of the American Podiatric Medical Association
ual sensor units to assess the effect of toe props on claw toes. Claw toe deformity is common in the adult population, particularly in the elderly,6 and is strongly associated with diabetic peripheral neuropathy1 and rheumatoid arthritis.7 Abnormal claw toe and metatarsal area loading has been reported in diabetes mellitus,8 and high plantar pressures over bony prominences have been linked to ulceration,9 necessitating cautious orthotic therapy for patients with this condition. Current conservative management is aimed at palliative treatment of painful lesions and functional correction,10 particularly when surgery is not advisable or acceptable to the patient. Use of silicone plantar props under claw toes to deflect pressure is a routine clinical option, although there is no objective research evidence to support it.11 Previous research includes a single-subject study12 using the F-Scan (Tekscan, Boston, Massachusetts) in-shoe measurement system that showed a trend in peak pressure reduction under callused apices of claw toes with silicone toe props. Peak pressures have been widely used as the primary measurement variable, possibly reflecting ease of measurement and analysis13 rather than significant correlation with pathology.9, 14 However, pressure–time integrals, combining time and magnitude of pressure, are thought to have a greater role in lesion pathogenesis.1, 15, 16 As the F-Scan system has a high sensor density (a maximum of 960 sensor units per sensor insole in a 0.5-cm grid), it provides a high spatial resolution that avoids the loss of small features owing to pressure averaging,4, 17 making it well suited for the analysis of toe and metatarsal head pressures.18 The F-Scan system has been thoroughly appraised elsewhere.18-21 Potential sources of measurement variability have been attributed to the inherent physical characteristics of the F-Scan sensors, ie, problems inherent to ink-based force-sensing resistors, especially when incorporated into a thin, flexible, polymer insole.18 The most accurate measurements have been obtained in initial loading sequences,18, 19 particularly under the metatarsal area.21 Sensor reliability is decreased by performing measurements on different days and by taking the sensor insole in and out of the shoe between trials.19 The consensus is that although improvements in accuracy and reliability are desirable, valuable quantitative information can be obtained when using the system in controlled comparative clinical studies by taking the limitations of the system into account in the study design.18-21 In the literature, orthotic efficacy has been demonstrated with the F-Scan using different materials and for different pathologies by masking forefoot plantar areas,19, 22-24 but significant pressure reduction was
not demonstrated under specific anatomical structures, such as a single toe or metatarsal head. It is proposed here that the F-Scan’s high spatial resolution and ability to easily export raw data for every sensor unit can be used to reveal not only detailed pressure–time integral changes but also those with statistical significance. Following the measurement of a subject’s plantar pressure–time integrals with and without an orthosis, there is an option to test the differences between the two sets of data obtained from every individual F-Scan system sensor unit for significance using the paired t-test in a spreadsheet. In this study, the data were further used to isolate the significant (P < .01) pressure–time integral changes and to provide surface charts for each foot that show contours of equal (significant) pressure–time integral change, coupled with graduated coloring of the magnitude of the (significant) pressure–time integral change. The aim of this study was to investigate the effect of prefabricated Hydrogel (Luga Suministos Medicos, Madrid, Spain) props on toes and metatarsal heads in subjects with claw toes by comparing pressure–time integrals derived from individual sensors of the F-Scan system.
Materials and Methods Subjects Eleven individuals (ten women and one man) aged 60 to 80 years with clawed lesser toes and in good health were selected opportunistically from a local National Health Service podiatry clinic. Exclusion criteria were previous foot operations, ulceration, diabetes mellitus, rheumatoid arthritis, blindness, and inability to walk unaided or to understand written or verbal instructions. Ethical approval was obtained before the start of the study from Southampton and South West Hampshire Local Research Ethics Committee, and informed consent was obtained from each participant.
Apparatus The F-Scan system, version 3.848, was used to measure in-shoe plantar pressures during the stance phase (sampling frequency, 50 Hz). The subjects were fitted with a pair of prefabricated Hydrogel natural silicone toe props (small, medium, or large).
Procedure The same researcher (P.J.C.) conducted all procedures and measurements. Presence of claw toe and
Journal of the American Podiatric Medical Association • Vol 94 • No 3 • May/June 2004
247
weight were recorded for each subject. A claw toe was defined as a toe that had an extended metatarsophalangeal joint, a flexed proximal interphalangeal joint, and a flexed distal interphalangeal joint.25 Subjects used their own comfortable, flat, laced shoes. One pair of F-Scan sensor insoles was issued per patient, and each insole was trimmed, inserted, and taped into the shoe before testing. Sensor insoles remained in the shoes until data collection was completed to avoid deformation by folding or crinkling. Toe props were carefully fitted to avoid the toe pulps and the metatarsal area. Nylon shoe liners (Boots Group PLC, Nottingham, England) were worn over the foot and toe prop to prevent foot-sensor adherence. A practice walk was made in an oval trajectory on a standard 9-m surface for six gait cycles 5 min before testing to allow for sensor moisture and temperature adjustment and subject familiarization with the equipment and procedure. Sensor calibration followed the system manufacturer’s method by loading each foot sequentially. Subjects walked at a comfortable self-selected speed for three trials (of typically eight right steps and eight left steps per trial) for each condition, with recording starting after one full gait cycle. The two conditions, ie, with the toe prop (prop) and without the toe prop (control), were recorded in random order to minimize series bias. A final trial, with an identical condition to the first, was run to assess sensor durability. Measurement protocols were developed from system manufacturer’s guidelines combined with recommendations from previous research using the F-Scan.18-24, 26
Data Analysis The F-Scan software was used to automatically calculate the pressure–time integrals, and the graphics option was used to identify the stance phase in all steps. The first left and right footsteps, where the subject might have accelerated, and the last left and right footsteps, where slowing down might have occurred, were excluded from each of the three trials for all subjects, feet, and conditions. Raw pressure–time integral data for all individual sensor units of the F-Scan sensor insole for each remaining step were downloaded into individual spreadsheets for each footstep. These were combined into single multisheet workbooks, one for each left and each right foot per subject (ie, 22 workbooks, each with typically 18 worksheets [footsteps] for the prop condition and 18 for the control condition). Within each workbook, the rows and columns containing no data were deleted across all worksheets to reflect the
248
individual trimming of the physical sensors for each subject’s foot. The rows and columns were also sized across all worksheets to the 0.5-cm spacing of the actual F-Scan sensor units. Following these two simple edits, all of the worksheets in every workbook overlaid perfectly with each other (ie, the same cells had nonzero pressure–time integral data on every worksheet). Also, when printed, the worksheets were easily matched to the actual sensor/sensor unit (ie, the nonzero cells matched the sensor units on the sensor unit remaining after trimming). Once the worksheets were overlaid correctly, multisheet data analysis was used to calculate means and SDs for each individual sensor unit position across all toe prop steps and, separately, for control steps for each subject, foot, and condition. Pressure–time integral data from individual sensor units were then subjected to a paired t-test in which each toe prop step sensor unit was matched with the equivalent control step sensor unit. This was done for each subject and foot. Because the paired t-test analysis is comparative and intrasubject, this pairing approach eliminates all variability effects of the F-Scan sensor that are purely linear with respect to footstep cycles.18 The paired t-test was chosen because nonparametric tests on such a small sample (typically n = 18) have little validity, whereas the unchecked assumption of data normality within the paired t-test is justified by the robust design of the test and the high confidence level used. A final worksheet was then constructed in each workbook that included the mean pressure–time integral differences (in kilopascal seconds) for each individual sensor unit where P < .01. The high confidence level (99%) was chosen because it eliminated all the noise but none of the pressure–time integral change data in the treatment area, thus providing visual clarity and detailing to anatomical structures. Surface charts from these final worksheets showed contours of equal (significant) pressure–time integral change and (manually) graduated coloring of the magnitude of the (significant) pressure–time integral change. Similar surface charts of mean absolute pressure–time integral values for each subject, foot, and condition were used to identify the individual sensor units recording the maximum absolute pressure–time integral values under each toe and metatarsal head and for confirmation of the anatomical and toe prop locations. To further test sensor reliability, maximum force data (in newtons) for each subject, foot, and step from the first and final trials (ie, with similar conditions) were matched step for step, and differences
May/June 2004 • Vol 94 • No 3 • Journal of the American Podiatric Medical Association
were analyzed using the paired t-test. Maximum force data were chosen for this variability test because the F-Scan sensor units are actually force transducers (the F-Scan software calculates pressures, pressure–time integrals, etc), and the maximum measurement is likely to vary first.
Results Detailed surface charts of significant (P < .01) pressure–time integral changes due to toe props were successfully obtained for the plantar surfaces of all subjects. Surface charts of the left and right feet of a typical subject indicated significant pressure–time integral reductions under the second and third toe apices and the second to fifth metatarsal heads (Fig. 1). Significant pressure–time integral increases were located over a surface area physical shape and in a location consistent with the toe prop in the toe sulci, with the greatest increases under the third toe sulcus. Table 1 and Figure 2 show the absolute highest mean pressure–time integral values obtained from a single sensor unit across all three trials under each toe and metatarsal head of the left foot of the same typical subject represented in Figure 1 for the toe prop and control conditions. Comparison of Figures 1 and 2 shows that only pressure–time integral differences between conditions that exceeded the SD within conditions (Fig. 2) passed the paired t-test filter and appeared as significant (P < .01) changes surface-charted in Figure 1. These changes included the pressure–time integral reductions of 99.8% under the third toe and 26.5% under the third metatarsal head but excluded the decreases under the first toe and metatarsal head and the increases under the fourth and fifth toes. Claw toe deformity was positively identified in the third toe of all 22 feet and in the fourth toe of 15 feet (not including the typical subject in Figs. 1 and 2). The second toe of 17 feet (including the typical subject in Figs. 1 and 2) exhibited a partial deformity. Analysis of paired t-tested surface charts from all 22 feet of the 11 subjects indicated that significant pressure–time integral reduction with props occurred under lesser toe apices ranked in order 3>2>4>5 (100% to 9%) and under lesser metatarsal heads 3=4>2>5 (73% to 32%) (Table 2 and Fig. 3). Significant pressure–time integral increases were observed under all toe props. Thirty percent of the feet showed pressure–time integral increases under the first toe proximal phalanx and the first metatarsal head. The results of the paired t-tests for maximum force variability from individual feet varied widely
(average P = .43). Across all 22 feet, the average maximum force (660 N) increased from the first to the final trial by only 1.0% (6.60 N), with an SD of 2.85% (18.85 N), again demonstrating no significant usagebased sensor variability. This study demonstrated significant (P < .01) differences in toe and metatarsal head plantar pressure–time integrals between individuals wearing prefabricated silicone toe props and the same individuals not wearing the props; therefore, the null hypothesis was rejected.
Discussion Analysis Method In contrast to previous plantar pressure studies1, 5, 14, 19, 21, 22, 24, 27, 28 that used the masking technique to provide pooled sensor data for analysis, this study directly targeted individual sensor units as a data source. This approach extended the options for data analysis so that detailed data could be presented not only in tables and bar charts but also in a surfacechart format. This format allowed clear visualization of the pressure–time integral changes specific not only to individual toe apices and metatarsal heads but also to the toe prop and its close perimeters. The full extent and range of these pressure–time integral changes have thus been made available for visual examination and were not lost to artificial averaging and smoothing within a mask. The surface charts presented only the pressure–time integral differences that had already passed the significance test. Although statistical significance cannot be equated with clinical significance, the identification of significant, detailed changes attributable to the intervention is a definite clinical benefit. The scope of this analysis method could be developed further by using a software solution to increase the efficiency and capacity of the extensive data handling required for multiple F-Scan frame analysis. This would facilitate the measurement of other variables, including peak pressure, pressure duration, and loading rate, thus enhancing the value of this study. Application of the method to other foot areas and orthotic therapies would also be accelerated. In addition, the process of matching the precise location of anatomical plantar landmarks to individual sensor units on the F-Scan sensor insole has been identified recently as a potential source of error.29 The accuracy of this process could be improved by using inked footprint impressions so that the used sensor showed exactly where plantar landmarks and
Journal of the American Podiatric Medical Association • Vol 94 • No 3 • May/June 2004
249
50 to 55 45 to 50 40 to 45 35 to 40 30 to 35 25 to 30 20 to 25 15 to 20 10 to 15 5 to 10 0 to 5 –5 to 0 –10 to –5 –15 to –10 –20 to –15 –25 to –20 –30 to –25 –35 to –30 –40 to –35 –45 to –40 –50 to –45 –55 to –50
Pressure– Time Integral Changes (kPa sec)
Figure 1. Excel (Microsoft Corp, Redmond, Washington) surface charts of significant (P < .01) mean pressure–time integral changes between toe prop and control conditions for each F-Scan insole sensor unit under the left and right feet of a typical subject. The F-Scan sensor units are located at the corners of each square in the surface charts. If P ≥ .01, the value zero was charted and the square was colored white to give greater definition to the changes with a higher level of significance. Significant (P < .01) pressure–time integral reductions are represented in shades of blue and are positioned under the second and third toe apices and the second to fifth metatarsal heads. Significant (P < .01) pressure–time integral increases, represented in yellow through red, correspond to the position of the toe prop in the toe sulci.
250
May/June 2004 • Vol 94 • No 3 • Journal of the American Podiatric Medical Association
Table 1. Absolute Highest Mean Pressure–Time Integral (PTI) Values Obtained for a Single Sensor Unit Across All Three Trials Under Each Toe and Metatarsal Head of the Left Foot of a Typical Subject for the Toe Prop and Control Conditions 1
Toe and Metatarsal Head Number 2 3 4
5
Cell (sensor unit) number Absolute highest mean PTI for control on toe Absolute highest mean PTI for prop on toe Highest mean PTI difference (control – prop) on toe PTI SD for control on toe PTI SD for prop on toe
N5 53.29 47.75 –5.54 17.15 12.71
G3 29.70 3.35 –26.35 8.35 1.59
E5 53.08 0.08 –53.00 12.13 0.23
C10 26.73 29.22 2.49 5.25 3.39
C13 29.93 40.84 10.92 8.91 8.03
Cell (sensor unit) number Absolute highest mean PTI for control on metatarsal head Absolute highest mean PTI for prop on metatarsal head Highest mean PTI difference (control – prop) on metatarsal head PTI SD for control on metatarsal head PTI SD for prop on metatarsal head
N14 33.49 28.20 –5.29 13.74 12.41
I14 52.24 42.75 –9.50 6.05 4.90
F16 75.95 55.84 –20.11 4.83 5.55
D17 67.93 52.98 –14.95 5.88 5.84
B19 52.05 42.10 –9.94 5.76 5.26
Note: Data are given in kilopascal seconds.
the prop impacted. Matching of individual sensor units to spreadsheet cells has already been shown to be reliable. The applicability of the technique to other pressure-measurement systems is unknown and awaits confirmation. Redmond et al,27 using the Pedar in-
Control on toe Control on metatarsal head
shoe measurement system (Novel GmbH, Munich, Germany), recently commented that a requirement for more mask areas to further define foot function had to be weighed against the resulting ratio of mask size to sensor number in the Pedar in-shoe measurement system, thus decreasing data reliability. It is
Prop on toe Prop on metatarsal head
Difference on toe Difference on metatarsal head
80 -
Pressure–Time Integral (kPa sec)
60 -
40 -
20 -
0-
–20 -
–40 -
–60 1
2
3 Toe and Metatarsal Head Number
4
5
Figure 2. Absolute highest mean pressure–time integral values obtained for a single sensor unit across all three trials under each toe and metatarsal head of the left foot of a typical subject for the toe prop and control conditions. The data are given in Table 1, and the SDs are shown as error bars.
Journal of the American Podiatric Medical Association • Vol 94 • No 3 • May/June 2004
251
Table 2. Feet (All Subjects) with Significant (P < .01) Pressure–Time Integral (PTI) Changes Under Specific Toe Apices and Metatarsal Heads 1 Number of toes with PTI reduction Number of toes with PTI increase Number of metatarsal heads with PTI reduction Number of metatarsal heads with PTI increase
3 6 7 8
proposed that the analysis method reported here using the F-Scan increased sensitivity and definition without compromising reliability.
Plantar Pressures The results of this study demonstrate that significant (P < .01) pressure–time integral reduction was most reliably achieved over the second and third toe apices and the third and fourth metatarsal heads with toe props. Significant pressure–time integral increases were consistently observed over an area occupied by the toe prop. This objective study confirms previous subjective observations10, 11 and the findings of a single-subject study12 of pressure reduction by toe props. Increases over first toes and first and second metatarsal areas may have reflected medial effects of the prop loading these feet through the first and second
Increases
Toes with reduction
Toes with increase
Toe and Metatarsal Head Number 2 3 4 17 0 13 6
22 0 16 2
15 0 16 0
5 2 0 7 1
metatarsals, as described by Hughes et al.4 This observation illustrates the potential use of this analysis method to identify possible transfer lesion sites due to orthotic intervention. Clinical management, therefore, could be effectively risk-assessed, and preventive pressure relief or deflection could be targeted to a specific coexisting deformity. Possible correlation of pain relief and lesion regression with plantar pressure reduction during toe prop use deserves exploration. Individuals with claw toes often report severe pain and calluses,4 and the role of pressure–time integrals in lesion pathogenesis may depend on whether low pressure is applied for a long time or high pressure is applied for a short time.13 Determination of the individual contributions of magnitude of pressure and the length of time it is applied in different parts of the stance phase to pressure–time integral reduction were studied by
Metatarsal heads with reduction
Metatarsal heads with increase
50 -
25 -
Feet (%)
0-
–25 -
Reductions
–50 -
–75 -
–100 1
2
3 Toe and Metatarsal Head Number
4
5
Figure 3. Percentage of feet (all subjects) with significant (P < .01) pressure–time integral changes under specific toe apices and metatarsal heads (the actual numbers are given in Table 2).
252
May/June 2004 • Vol 94 • No 3 • Journal of the American Podiatric Medical Association
Raspovic et al,26 who reported that temporal loading was unaffected.
high-pressure loading of small structures be prevented by risk-assessed therapy of any coexisting deformity.
Increase in Contact Area
Acknowledgment. Michael Claisse, BSc(Hons), for advice on statistical analysis using Excel and Hans Bakker, Director at Canonbury Products Limited, Brackley, Northamptonshire, England, for the supply of Hydrogel natural silicone toe props.
Hughes et al4 stated that if the toe contact area is reduced, the load-bearing area is further decreased, resulting in more pressure over the metatarsal heads. In this study, the greatest pressure–time integral increases were under the prop and the greatest reductions were under the metatarsals and toes adjacent to the prop, suggesting an increased contact area attributable to the prop and arguably underscoring its orthotic efficacy.21, 26
Validity and Reliability F-Scan force sensor variability under cyclic loading was previously reported18, 28 to increase output force approximately linearly with increasing load cycles for a low number of cycles (n < 100). Results of the present study of maximum force variability suggest that variation was insignificant. The surface-chart analysis in the present study is comparative and intrasubject, with a pairing approach that eliminates FScan sensor variability that is linear with respect to footstep cycles. Normal intrasubject step-to-step variability suggested by Akhlaghi et al30 was accounted for by avoidance of subjective step selection and by sequential step comparison of multiple steps.1, 19 Intersubject variation may have been influenced by the different types of shoes worn by subjects and by individual foot deformities with their associated compensations, but this analysis method, which is primarily intrasubject, made these variations less relevant.
Conclusion A new method of plantar pressure analysis has been explored that capitalizes on the F-Scan’s high spatial resolution and its facility to export raw data for every sensor unit. Clear identification of significant, detailed pressure–time integral changes attributable to an intervention has been made possible by innovative exploitation of current technology. Further software developments for automating data analysis are required before this powerful analysis method is applied in the clinical environment. This first application in a small comparative study of toe and metatarsal head pressures supports evidence-based use of prefabricated silicone toe props in the management of claw toes. It is recommended that
References 1. C AVANAGH PR, U LBRECHT JS: Clinical plantar pressure measurement in diabetes: rationale and methodology. The Foot 4: 123, 1994. 2. B ARNETT S: International protocol guidelines for plantar pressure measurement. Diabet Foot 1: 137, 1998. 3. ROSENBAUM D, BECKER HP: Plantar pressure distribution measurements: technical background and clinical applications. J Foot Ankle Surg 3: 1, 1997. 4. H UGHES J, C LARK P, K LENERMAN L: The importance of the toes in walking. J Bone Joint Surg Br 72: 245, 1993. 5. METAXIOTIS D, ACCLES W, PAPPAS A, ET AL: Dynamic pedobarography in operative management of cavovarus foot deformity. Foot Ankle Int 21: 935, 2000. 6. H UNG L, H O Y, L EUNG P: Survey of foot deformities in 166 geriatric patients. Foot Ankle 5: 156, 1995. 7. D’A MICO JC: The pathomechanics of adult rheumatoid arthritis affecting the foot. JAPA 66: 227, 1976. 8. B ETTS RP, F RANKS CI, D UCKWORTH T: “Foot Pressure Studies: Normal and Pathologic Gait Analyses,” in Disorders of the Foot and Ankle, 2nd Ed, Vol 1, ed by MH Jahss, p 484, WB Saunders, Philadelphia, 1991. 9. BOULTON AJM: “The Importance of Abnormal Foot Pressures and Gait in the Causation of Foot Ulcers,” in The Foot in Diabetes: Proceedings of the First National Conference on the Diabetic Foot, Malvern, May 1986, ed by H Connor, AJM Boulton, JD Ward, p 11, Wiley, Chichester, England, 1987. 10. KIPPEN C: A literature review of non-surgical techniques used by chiropodists for correcting lesser toe pathologies. J Br Podiatr Med 47: 137, 1992. 11. KIPPEN C: High intensive treatment/management: a clinical survey. Chiropodist 38: 293, 1983. 12. C AMMISS M: Pressure Loads Associated with Clawed Digits [thesis], University of Southampton, Southampton, England, 1999. 13. P OTTER J, P OTTER M: Effect of callus on peak plantar pressures. The Foot 10: 23, 2000. 14. HODGE MC, BACH TM, CARTER GM: Orthotic management of plantar pressure and pain in rheumatoid arthritis. Clin Biomech 14: 567, 1999. 15. SOAMES RW: Foot pressure patterns during gait. J Biomed Eng 7: 120, 1985. 16. F ULLER EA: “Computerized Gait Evaluation,” in Clinical Biomechanics of the Lower Extremities, ed by RL Valmassy, p 180, CV Mosby, St Louis, 1996. 17. O RLIN MN, M C P OIL TG: Plantar pressure assessment. Phys Ther 80: 399, 2000. 18. WOODBURN J, HELLIWELL PS: Observations on the F-Scan in-shoe pressure measuring system. Clin Biomech 11: 301, 1996. 19. ROSE N, FELWELL LA, CRACCHIOLO A: A method for mea-
Journal of the American Podiatric Medical Association • Vol 94 • No 3 • May/June 2004
253
20.
21. 22.
23.
24.
254
suring foot pressures using a high resolution, computerized insole sensor: the effect of heel wedges on plantar pressure distribution and centre of force. Foot Ankle 13: 263, 1992. M UELLER MJ, S TRUBE MJ: Generalizability of in-shoe peak pressure measures using the F-scan system. Clin Biomech 11: 159, 1996. AHRONI JH, BOYKO EJ, FORSBERG R: Reliability of F-Scan in-shoe measurements. Foot Ankle Int 19: 668, 1998. ALBERT S, RINOIE C: Effect of custom othotics on plantar pressure distribution in the pronated diabetic foot. J Foot Ankle Surg 33: 598, 1994. HAYDA R, TREMAINE D, BANCO BS, ET AL: Effect of metatarsal pads and their positioning: a quantitative assessment. Foot Ankle Int 15: 56, 1994. BROWN M, RUDICEL S, ESQUENAZI A: Measurement of dynamic pressures at the shoe-foot interface during normal walking with various foot orthoses using the FSCAN system. Foot Ankle Int 17: 152, 1996.
25. BRAHMS MA: “The Small Toes,” in Disorders of the Foot and Ankle, Vol 1, ed by MH Jahss, p 622, WB Saunders, Philadelphia, 1982. 26. RASPOVIC A, NEWCOMBE L, LLOYD J, ET AL: Effect of customised insoles on vertical plantar pressures in sites of previous neuropathic ulceration in the diabetic foot. The Foot 10: 133, 2000. 27. R EDMOND A, L UMB PS, L ANDORF K: Effect of cast and noncast foot orthoses on plantar pressure and force during normal gait. JAPMA 90: 441, 2000. 28. CAVANAGH PR: In-shoe plantar pressure measurement of the first metatarsophalangeal joint in asymptomatic patients [letter]. Foot Ankle Int 16: 53, 1995. 29. U RRY SR, W EARING SC: The accuracy of footprint contact area measurements: relevance to the design and performance of pressure platforms. The Foot 11: 151, 2001. 30. AKHLAGHI F, DAW J, PEPPER M, ET AL: In-shoe step to step pressure variations. The Foot 4: 62, 1994.
May/June 2004 • Vol 94 • No 3 • Journal of the American Podiatric Medical Association