UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl)
Improving footwear to prevent ulcer recurrence in diabetes: Analysis of
adherence and pressure reduction
Waaijman, R.
Publication date
2013
Link to publication
Citation for published version (APA):
Waaijman, R. (2013). Improving footwear to prevent ulcer recurrence in diabetes: Analysis of
adherence and pressure reduction.
General rights
It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons).
Disclaimer/Complaints regulations
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.
Chapter 5
Diabetic Medicine 2012; 29: 1542–1549
© Reprinted with permission from Wiley-BlackwellRoelof Waaijman
Mark L.J. Arts
Rob Haspels
Tessa E. Busch-Westbroek
Frans Nollet
Sicco A. Bus
PRESSURE-REDUCTION AND PRESERVATION IN
CUSTOM-MADE FOOTWEAR OF PATIENTS WITH DIABETES AND A
HISTORY OF PLANTAR ULCERATION
ABSTRACT
Aims: To assess the value of using in-shoe plantar pressure analysis to improve and
preserve the offloading properties of custom-made footwear in patients with diabetes.
Methods: Dynamic in-shoe plantar pressures were measured in new custom-made
footwear of 117 patients with diabetes, neuropathy and a healed plantar foot ulcer. In 85 of these patients, high peak pressure locations (peak pressure >200kPa) were targeted for pressure reduction (goal: >25% relief or below an absolute level of 200 kPa) by modifying the footwear. After each of a maximum three rounds of modifica-tions pressures were measured. In a subgroup of 32 patients, pressures were measured and, if needed, footwear was modified at 3-monthly visits for 1 year. Pressures were compared to those measured in 32 control patients who had no footwear modifications based on pressure analysis.
Results: At the previous ulcer location and the highest and second highest pressure
locations, peak pressures were significantly reduced with 23%, 21%, and 15%, respec-tively, after footwear modification. These lowered pressures were maintained or fur-ther reduced over time and were significantly lower, by 24-28%, compared with pres-sures in the control group.
Conclusion: The offloading capacity of custom-made footwear for high-risk patients
can be effectively improved and preserved using in-shoe plantar pressure analysis as guidance tool for footwear modification. This provides a useful approach to obtain bet-ter offloading footwear that may reduce the risk for pressure-related diabetic foot ul-cers.
5
INTRODUCTION
Foot ulceration is a serious long term complication in patients with diabetes mellitus and polyneuropathy, which significantly increases the risk of infection and lower limb amputation1-3. The lifetime risk of developing an ulcer is 15-25%4. About half of all
ul-cers occur on the plantar foot surface5. Loss of protective sensation and high levels of
plantar foot pressure during ambulation are the main causative factors6-9. To prevent
ulceration, custom-made footwear is often prescribed to patients at high-risk for ul-ceration, and acts primarily by redistributing and relieving high plantar pressure levels. Despite this goal, objective evaluation of the pressure-relieving properties of custom-made footwear is still not common in diabetic foot practice. Footwear is mostly evalu-ated based on clinical experience and a trial-and-error approach. Feedback from the patient is limited due to the presence of neuropathy. Therefore, variability may exist in the offloading properties of this footwear, which several biomechanical studies show to be the case10, 11. Consequently, the offloading capacity of this footwear may often be
in-sufficient, which could be one of the factors that may explain the high recurrence rates of ulceration 1.
Offloading may be improved by modifying the patients’ footwear after delivery using objective measurement tools. A recent proof-of-principle study showed that in-shoe plantar pressure analysis is a valuable and efficient tool to guide footwear modifica-tion and achieve better offloading footwear12. This study was, however, conducted in a
relatively small and heterogeneous sample of patients, different footwear conditions, and in a setting where time was not constrained. Confirmation of these results in a large homogenous group of high-risk patients and footwear conditions, and in a time-con-strained clinical setting is required.
Another important aspect in footwear evaluation is the preservation of offloading prop-erties over time since only then a sustained reduction in the risk for ulceration may be assured. Wear and tear of the footwear or changes in foot shape could influence the pressure-relieving effects of custom-made footwear over time13-16. Therefore, to
main-tain proper offloading, repeated in-shoe pressure assessments and (if needed) addi-tional footwear modifications may be required.
For these reasons, we aimed to assess (1) the value of using in-shoe plantar pressure analysis for evaluating and improving the offloading properties of newly prescribed cus-tom-made footwear in patients with diabetes, neuropathy and a recently healed plantar ulcer, and (2) to determine in these patients whether improved offloading results can be maintained over a 1-year period when compared to a control group of patients wearing custom-made footwear that is not modified based on in-shoe pressure analysis.
PATIENTS AND METHODS
Subjects
± SD age of 63.3 ± 10.1 years) with duration of 17.7 ± 14.1 years were included. All patients were consecutively recruited from the outpatient foot clinics of 10 hospitals in the Netherlands, which all participated in a trial on the effectiveness of custom-made footwear in preventing diabetic foot ulcer recurrence (DIAbetic Foot Orthopaedic Shoe (DIAFOS) trial, trial register: NTR1091). All patients had loss of protective sensation as confirmed by the inability to sense the pressure of a 10-g Semmes Weinstein monofila-ment at one or more of three plantar foot sites, or a vibration perception threshold at the hallux >25V7. Most patients had one or more foot deformities, including
claw/ham-mer toes, hallux valgus, Charcot midfoot deformity, prominent metatarsal heads, and partial foot amputation. Each patient had a healed plantar ulcer during the previous 18 months. For the first study objective (improving offloading), data were collected in 85 of the total 117 patients. For the second study objective (preserving offloading), data were collected in the first 32 of these 85 patients who had completed one year follow-up (experimental group) and in 32 patients who were measured for in-shoe plantar pres-sure in their custom-made footwear, but had no modifications to the footwear based on these pressures (control group). Written informed consent was obtained from each patient before inclusion in the study, which was approved by the Local Research Ethics Committee.
Footwear
Patients wore newly prescribed fully custom-made footwear (i.e. custom-made insoles in custom-made shoes, also referred to as ‘orthopaedic footwear’ in some countries, N = 95) or semi custom-made footwear (i.e. custom-made insoles in off-the-shelf extra depth shoes, also referred to as ‘semi-orthopaedic footwear’, N = 22). The footwear was prescribed by a rehabilitation specialist and manufactured by a shoe technician work-ing in each of the centres. Each team had a minimum of 4 years experience in diabetic foot practice. Although not enforced by any protocol, footwear design mostly followed the Delphi-based algorithm published by Dahmen and colleagues17. The footwear was
generally manufactured from a plaster cast or foam mould of the foot. Blueprints were commonly used to identify target regions of high pressure for footwear design. The foot-wear generally had a stiffened rubber outsole with roller configuration. Custom-made insoles consisted of multi-density layered materials, with mouldable cork or multiform base and an open or closed-cell material top cover.
Instrumentation
In-shoe plantar pressures were measured using the Pedar-X system (Novel, Munich, Germany). This system consists of flexible 2-mm-thick insoles with 99 sensors which independently measure the normal pressure at a sample frequency of 50 Hz. The in-soles were placed between the sock and the insole of the shoe. Multiple insole sizes were available to accommodate different foot sizes. Each pair of Pedar insoles was cali-brated each 3 months using a calibration device and guidelines from the manufacturer.
Protocol
In-shoe plantar pressures were measured while walking at a self-chosen comfortable speed along a minimum 10-m long walkway. Walking speed was measured using a stopwatch and kept constant during subsequent measurements in the same session or
5
during follow-up measurements (maximum 5% deviation in average walking speed). Aminimum of 20 midgait steps per foot were collected per measurement18. Patients were
provided with thin seamless socks during the measurement sessions.
The protocol used for evaluating and modifying the footwear is shown in Figure 1. In-shoe plantar pressures were measured in the footwear as delivered (entry visit, base-line assessment). Based on the average peak pressure pictures obtained over multiple foot steps, regions of interest were selected (peak pressure was the parameter used throughout the study)19. These included the previous ulcer location and, if present, per
foot the two highest peak pressure locations in the midfoot and forefoot with peak pres-sure >200 kPa. In the 85 patients assessed for offloading improvement, the footwear was subsequently modified by the shoe technician with the goal to reduce peak pres-sure at the regions of interest. Choice of modification to the shoes or insoles was left to the shoe technician and/or rehabilitation specialist. Multiple modifications were al-lowed at once.
Criteria for successful improvement in offloading were defined. These were a peak pressure reduction at the region of interest of 25% compared to baseline levels or a reduction to an absolute level below 200 kPa. Using in-shoe pressure within this con-text as a surrogate indicator for risk of foot ulceration, both criteria were considered to be indicative of a relevant reduction in risk of ulceration12, 20. If the criteria were not
met, a maximum of two subsequent rounds of footwear modifications and in-shoe pres-sure meapres-surements were applied. If the criteria were eventually not met, offloading improvement was considered as a failure.
Follow-up in-shoe pressures were measured at 3-monthly intervals (Figure 1). The re-gions of interest that were defined at baseline were also the rere-gions of interest during follow-up. In the 32 experimental group patients in-shoe pressure was measured and the footwear was modified if the criteria for successful offloading were not yet achieved at entry visit (0 months) or when, compared to the final pressure measured at entry, peak pressure at the region of interest had increased with 5% or more. After each round of footwear modifications, in-shoe pressures were measured, similar to how this oc-curred at entry.
Footwear modifications in the control group between study visits based on normal practice were identified by asking the patient about visits to the shoe technician. If con-firmed, the shoe technician was asked about modifications made and details were re-corded.
Data analysis and statistics
During the testing sessions, data analysis was done on-screen from the peak pressure distribution pictures of the foot. After the testing session, formal data analysis was con-ducted by masking the regions of interest in the pressure pictures and calculating mean peak pressures for each mask using Novel multimask software (Novel, Munich, Ger-many).
Figure 1. Flow diagram of the footwear modification protocol used at entry and at each follow-up assessment. The regions of interest (ROI) were the previous ulcer location (PUL) and the two highest peak pressure locations in the midfoot and forefoot with peak pressure >200 kPa (HPL1 and HPL2). PP, peak pressure; FU, follow-up; wrt, with respect to.
High-pressure locations may shift from the region of interest to neighbouring (anatomi-cal) regions as a result of modifying the footwear. To assess this possible effect, change in peak pressure after all rounds of footwear modifications was calculated in each of 10 masked foot regions: lateral and medial heel, medial and lateral midfoot, metatarsal 1, metatarsals 2-3, metatarsals 4-5, hallux, toes 2-3, and toes 4-5. These transfer pressure effects were considered excessive when peak pressure increase was more than 25 kPa, more than 25%, and when peak pressures reached a level >200 kPa
Descriptive analyses were done using SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). Outcomes for offloading at entry and follow-up pressure measurement were modelled by multilevel linear regression analysis using MLwiN software, version 2.23 (Institute
5
of Education, University of London, London, UK). The foot pressure data were nested atfour levels - participating centre (fourth level), patient (third), foot (second), and time (first) - to determine and (if needed) account for dependency of the data on these fac-tors21. To analyse footwear modification effects, in-shoe peak pressure was regressed
on the variable ‘time’ (pre-modification, post-modification), and on the covariate ‘type of footwear’ (fully custom-made or semi custom-made). To analyse follow-up effects, in-shoe peak pressure was regressed on the variables ‘study group’ (experimental, con-trol), ‘time’ (each 3-month visit), and their interaction.
RESULTS
The previous ulcer location and the two highest peak pressure locations are shown in Table 1. A peak pressure >200 kPa at the previous ulcer location was found in 27 pa-tients, a peak pressure <200 kPa in 49 patients of 85 patients assessed for offloading improvement. These groups were analysed separately. In nine patients, the previous ulcer location was amputated.
Table 1. Anatomical locations of the previous ulcer and, the two highest peak pressures per foot in the 85 patients assessed for offloading improvement.
Region Previous ulcer location Highest and second highest peak pressure location
Hallux 15 (1) 33 Toes 2-3 17 (4) 1 Toes 4-5 2 (1) 0 Metatarsal 1 23 (2) 53 Metatarsal 2-3 15 (1) 90 Metatarsal 4-5 11 (0) 19 Midfoot medial 1 (0) 4 Midfoot lateral 1 (0) 2 Total 85 (9) 202
Data are expressed as n with the number of amputations of that region in between brackets.
Table 2 shows the outcomes for offloading improvement at entry. In-shoe peak pressure was reduced significantly after modifying the footwear with 23% at the previous ulcer location with peak pressure >200 kPa, with 21% at the highest peak pressure location, and with 15% at the second highest peak pressure location (P < 0.01). To achieve these results, on average 1.4 (SD 0.7) rounds of footwear modifications were needed. In 64% of the cases, one round of footwear modifications was used. In both footwear types, modifications were made to the shoes and insoles. The modifications applied most were the removal of material in the insole at the region of interest (33% of all modifications), replacement of the insole top cover (20%), softening of material in the insole at the region of interest (16%), placement of a metatarsal pad or bar (16%), and the adjust-ment of the pivot point in the outsole roller (6%). Successful offloading was achieved in 51-59% of these regions, dependent on location. At the previous ulcer location with peak pressure <200 kPa, peak pressures could not be further reduced by modifying the footwear (in 60% of cases one round of modification was applied, in 40% the footwear
was not modified). None of the outcomes was dependent on type of footwear or partici-pating centre. Excessive build-up of peak pressure in neighbouring regions was present in 2% of cases.
Table 3 shows the outcomes for the follow-up pressure analysis. No significant differen-ces were present between the two study groups in patient characteristics and baseline in-shoe pressures. Figure 2 shows the course of peak pressure over one year for the two study groups. For this analysis, all regions of interest with a peak pressure >200 kPa were pooled. After modification at entry, the difference between study groups for these pooled regions was significant, and this difference increased over time. Peak pressure reduced significantly over time in the experimental group (βtime = -5 kPa/follow-up; 95% CI, -8.6 to -0.7; P < 0.01), but not in the control group (βtime = -1 kPa/follow-up; 95% CI, -6.6 to 3.9; non-significant). For the previous ulcer location with baseline peak pressure <200 kPa, mean peak pressure did not change significantly over time in either study group. At 3 months follow-up, in 58% of the cases one round of footwear modifications was applied and in 28% of cases no modifications were made. At 12 months follow-up, these percentages were 20% and 78%, respectively. Successful offloading was achieved in 64% of the regions of interest with baseline peak pressure >200 kPa after 3 months follow-up and in 81% after 12 months follow-up. In four of the 32 control group pa-tients, the footwear was modified between visits at a single occasion during follow-up. None of the outcomes in either group during follow-up was dependent on participating centre.
Figure 2. Mean in-shoe peak pressure measured at entry and at 3-monthly intervals over the course of 1 year follow-up in the experimental group (E, closed symbols) and the control group (C, open symbols) for all regions of interest with peak pressure >200kPa (ROI>200) and the previous ulcer location with peak pressure <200kPa (PUL<200).
5
Table 2. R esults f or in-shoe pr essur e offloading at entr y in 85 patients . Measur ed in-shoe peak pr essur e (kP a)Modelled in-shoe peak pr
essur e (kP a) Region of inter est n Baseline Aft er footw ear modification β0 β1 Suc cessful optimization No . of r ounds of modifications Mean (SD) Mean (SD) Mean (SE) Mean (SE) % Mean (SD) PUL <200 49 123 (43) 127 (46) 123 (6.3)** ns 94 0.6 (0.5) PUL >200 27 287 (79) 221 (49) 287 (12.5)** -66 (12.4)** 59 1.4 (0.6) HPL1 123 277 (67) 220 (61) 276 (6.3)** -57 (3.9)** 59 1.5 (0.8) HPL2 79 247 (44) 210 (44) 246 (5.8)** -38 (3.9)** 51 1.4 (0.8) Measur ed in-shoe peak pr essur es ar e sho wn f or base line and f or final in-shoe pr essur e asse ssment (aft er all r ounds of modific ations). Abbr eviations: PUL <200 , PUL >200 , all pr evious ulc er loc ations wit h measur ed peak pr essur es be lo w and abo ve 20 0kP a, re spectiv ely; HPL1 and HPL2, highe st and sec ond -highe st peak pr essur e loc ation wit h peak pr essur e >200 kP a, r espectiv ely; SD , st andar d deviation; SE, st andar d err or . Regr ession mode l: out come v ariable = β 0 + β opt * time, in w hic h β 0 = int er cept; β 1 = r egr
ession slope; time = bef
or e (0) and aft er (1) f oot w ear modific ation. Signific anc e: ns, not signific ant , ** P<0.01
Table 3. R esults f or in-shoe pr essur e offloading during f ollo w-up asse ssments. Measur ed in-shoe peak pr essur e (kP a) Suc cessful impr ov ement Rounds of modifications (n) Region of inter est Stud y gr oup Befor e footw ear modification Aft er footw ear modification 0 months 3 months 1 y ear 0 months 3 months 1 y ear n Mean (SD) Mean (SD) % % % Mean (SD) Mean (SD) Mean (SD) PUL <200 Contr ol 17 127 (40) 100 100 100 RO I>200 78 272 (55) 0 21 23 PUL <200 Experimental 20 130 (41) 133 (42) 95 100 100 0.7 (0.5) 0.1 (0.3) 0.1 (0.2) RO I>200 95 265 (51) 213 (45) 53 64 81 1.6 (0.8) 1.0 (0.8) 0.3 (0.5) Results of multile vel linear r egr ession model. β0 βstud y gr oup βtime kP a (SE) kP a (SE) kP a/follo w -up (SE) PUL <200 130 (5.9)** ns ns No Int er action RO I>200 268 (8.2)** -64 (10.8)** -3 (1.4)* Int er action eff ect Measur ed in-shoe peak pr essur es f or ar e sho wn bot h study gr oups bef or e an y modific ation and f or t he e xperiment al gr oup aft er all r ounds of modific ations. PUL <200 , all pr evious ulc er loc ations wit h measur ed peak pr essur es be lo w 200 kP a; R OI>200 , all r egions of int er est wit h measur ed peak pr essur e abo ve 200 kP a; SD , st andar d deviation; SE, st andar d err or . Regr ession mode l: out come variable = β0 + βstudy gr oup * study gr oup + βtime * time, in w hic h β0 = int er cept; βstudy gr oup and, βtime = r egr ession slope; study gr oup = c ontr ol gr oup (0) or e xperiment al gr oup (1); time = f ollo
w-up visit (0, 3, 6, 9 and 12 mont
hs). Signific anc e: ns, not signific ant , * P<0.05 ** P<0.01.
5
DISCUSSION
This study shows that plantar pressures at high-pressure regions can be reduced to substantial degrees after modifying custom-made footwear based on in-shoe pressure analysis. At the most at-risk foot location, the previous ulcer location, peak pressures above 200kPa were reduced with a mean 23%. However, when peak pressures at the previous ulcer location were below 200 kPa, further pressure reduction proved elu-sive, suggesting that sufficiently offloaded conditions were already present. Improved offloading was maintained and even further improved over a 12-month follow-up pe-riod, and was significantly better that footwear that was not modified based on in-shoe pressure analysis. In only 2% of regions neighbouring the regions of interest, excessive build of pressure was found. In the majority of high-pressure regions (53%), successful offloading was achieved according to the set criteria, and this improved to 64% after 3 months and to 81% after 1 year. This provides a valuable objective approach to achieve and preserve better offloading custom-made footwear. Whether this will reduce the risk for pressure-related plantar foot ulcers in patients with diabetes remains to be in-vestigated.
The offloading results at entry confirm recent findings from a similar but smaller study12. This study reported a mean 30% peak pressure relief after footwear
modifica-tion and a 100% success rate using similar criteria. The lower current success rates may be because more regions of interest per foot were selected. This may have reduced the chance for success in each region of interest, because of pressure redistribution effects or because a certain region was given priority for clinical reasons. In 63% of the failed offloading attempts, the maximum three rounds of modifications were not used. This may have been caused by time constraints in busy outpatient clinic or by the fear for in-creasing pressure in an already offloaded region. This adds to the lower success rate in the current study. These factors may also explain the lower mean number of modifica-tion rounds in the current study (1.4) compared to the previous study (1.8). Neverthe-less, both studies lead to the conclusion that in-shoe pressure analysis is a valuable tool to achieve better offloading footwear.
During follow-up, in-shoe peak pressures were further reduced by modifying the foot-wear. Fewer rounds of modifications were needed at each subsequent follow-up visit. The ‘saw tooth’ pattern of peak pressure change in the first 6 months (Figure 2), showed that improved results could not be preserved in the short run without further modi-fication of the footwear. These results support the long-term pressure monitoring at 3-monthly intervals. At each follow-up stage, in-shoe peak pressures were significantly lower in the experimental group than in the control group, in which peak pressures did not change over 12 months time. Wear and tear of the footwear was expected to increase peak pressures over time in the control group22, 23, despite that results on this
aspect are still inconclusive14, 24. Clearly, more research on the mechanisms of in-shoe
pressure change, or the lack thereof, over time is required to better clarify the follow-up pressure results in this study.
The majority of previous ulcer locations (64%) showed baseline peak pressures below 200 kPa and further pressure relief was not possible by modification of the footwear. The mean measured in-shoe peak pressure of 127 kPa in these cases was low. This
sug-gests that, for the previous ulcer location, the footwear was already sufficiently offload-ed, maybe because this location is an important and clear target in footwear design. In contrast, in 85 patients, 229 regions of interest with peak pressures >200 kPa were identified. Among these regions were many less clear targets, supporting the use of ob-jective evaluation tools. Risk for ulceration may be increased at these high-pressure lo-cations20, 25. Therefore, offloading was considered insufficient in these cases and in need
for improvement. The lack of a structured and evidence-based protocol for footwear de-sign and manufacturing may be an underlying cause. Footwear prescription and evalu-ation is in many ways still more an art than a science, and this may introduce variability in design and in offloading efficacy of footwear prescriptions10, 26. Better offloading can
be achieved with the use of quantitative computer-assisted approaches in footwear de-sign and manufacturing, which may reduce variability27. However, an individual-based
approach in footwear evaluation seems necessary. The current approach can be helpful in this regard, and seems to be independent of the clinical team (albeit having ample experience) and type of custom-made footwear used, which improves external validity. This study was limited in some aspects. First, data on ulcer recurrence rates were not available for this study. Therefore offloading success could not be associated with ulcer recurrence data. Success criteria were based on common sense and indications of clini-cally relevant pressure reduction that may prevent ulcer recurrence20, 28. Future studies,
such as our DIAFOS trial, should confirm if using such criteria can prevent plantar foot ulcer recurrence. Second, successful offloading did not necessarily imply optimal foot-wear. Further modification or other footwear designs may have further reduced pres-sure. However, our goal was to test a clinically feasible approach and, therefore, the number of modification rounds was limited to three. Finally, we did not use standard-ized protocols for modifying the footwear because of a lack of guidelines. This could af-fect the reproducibility of the results. Future investigations should focus on developing evidence-based guidelines for effective footwear designs and modifications.
In conclusion, we found that the majority of high-risk regions, whether predictable or not from foot screening, can be offloaded to a substantial degree using in-shoe plan-tar pressure analysis as guidance tool for modifying custom-made footwear. These im-proved conditions could be maintained and even further imim-proved over time using the same approach. This provides a useful objective approach for clinical practice to achieve and preserve better offloading footwear that may reduce the risk for pressure-related plantar foot ulcers in patients with diabetic.
5
Acknowledgements
In the DIAFOS trial, the Academic Medical Center collaborates with 9 other multidisci-plinary diabetic foot centres and 9 orthopaedic footwear companies in the Netherlands. The authors like to acknowledge the contribution of M. de Haart in project management and R. Keukenkamp in data collection (both Academic Medical Centre, Amsterdam) as welll as the following persons in recruitment of patients and prescription, manufac-turing, and modification of custom-made footwear: P. J. A. Mooren (AcademicMedical Centre, Amsterdam), J. W. E. Verlouw, I. Ruijs and H. van Wessel (Maxima Medical Cen-tre, Veldhoven), J. P. J. Bakker and C. van den Eijnde (Medical Centre Alkmaar), D. Wever and H. Wessendorf (Medisch Spectrum Twente, Enschede), R. Dahmen and B. Koomen (Slotervaart Hospital, Amsterdam), J. G. van Baal (Ziekenhuisgroep Twente, Almelo), J. Harlaar, V. de Groot and J. Pulles (VU Medical Centre, Amsterdam), W. P. Polomski, R. Lever and G. du Mont (Spaarne Hospital, Hoofddorp), H. G. A. Hacking and J. de Bruin (St Antonius Hospital, Nieuwegein), and H. Berendsen and W. Custers (Reinier de Graaf Gasthuis, Delft).
The DIAFOS trial was supported by project grants from the Dutch Diabetes Research Foundation (project 2007.00.067), the Dutch Foundation for the Development of Ortho-pedic Footwear Technology (OFOM), and the Dutch Organization for Health Research and Development (ZonMw, project 14350054).
REFERENCES
1. Boulton AJ, Kirsner RS, Vileikyte L. Clinical practice. Neuropathic diabetic foot ulcers. N Engl J Med 2004; 351: 48-55.
2. Pound N, Chipchase S, Treece K, Game F, Jeffcoate W. Ulcer-free survival following manage-ment of foot ulcers in diabetes. Diabet Med 2005; 22: 1306-1309.
3. Reiber GE, Vileikyte L, Boyko EJ, del AM, Smith DG, Lavery LA, Boulton AJ. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care 1999; 22: 157-162.
4. Singh N, Armstrong DG, Lipsky BA. Preventing foot ulcers in patients with diabetes. JAMA 2005; 293: 217-228.
5. Prompers L, Huijberts M, Apelqvist J, Jude E, Piaggesi A, Bakker K, Edmonds M, Holstein P, Jirkovska A, Mauricio D, Ragnarson TG, Reike H, Spraul M, Uccioli L, Urbancic V, Van AK, Van BJ, Van MF, Schaper N. High prevalence of ischaemia, infection and serious comorbidity in patients with diabetic foot disease in Europe. Baseline results from the Eurodiale study. Diabetologia 2007; 50: 18-25.
6. Frykberg RG, Lavery LA, Pham H, Harvey C, Harkless L, Veves. A Role of neuropathy and high foot pressures in diabetic foot ulceration. Diabetes Care 1998; 21: 1714-1719.
7. Pham H, Armstrong DG, Harvey C, Harkless LB, Giurini JM, Veves A. Screening techniques to identify people at high risk for diabetic foot ulceration: a prospective multicenter trial. Diabetes Care 2000; 23: 606-611.
8. Veves A, Murray HJ, Young MJ, Boulton AJ. The risk of foot ulceration in diabetic patients with high foot pressure: a prospective study. Diabetologia 1992; 35: 660-663.
9. Boulton AJ, Hardisty CA, Betts RP, Franks CI, Worth RC, Ward JD, Duckworth T. Dynamic foot pressure and other studies as diagnostic and management aids in diabetic neuropathy. Dia-betes Care 1983; 6: 26-33.
10. Bus SA, Ulbrecht JS, Cavanagh PR. Pressure relief and load redistribution by custom-ma-de insoles in diabetic patients with neuropathy and foot custom-ma-deformity. Clin Biomech (Bristol , Avon) 2004; 19: 629-638.
11. Guldemond NA, Leffers P, Schaper NC, Sanders AP, Nieman FH, Walenkamp GH. Comparison of foot orthoses made by podiatrists, pedorthists and orthotists regarding plantar pressure reduction in The Netherlands. BMC Musculoskelet Disord 2005; 6: 61.
12. Bus SA, Haspels R, Busch-Westbroek TE. Evaluation and optimization of therapeutic foot-wear for neuropathic diabetic foot patients using in-shoe plantar pressure analysis. Diabe-tes Care 2011; 34: 1595-1600.
13. Brodsky JW, Pollo FE, Cheleuitte D, Baum BS. Physical properties, durability, and energy-dissipation function of dual-density orthotic materials used in insoles for diabetic patients. Foot Ankle Int 2007; 28: 880-889.
14. Lobmann R, Kayser R, Kasten G, Kasten U, Kluge K, Neumann W, Lehnert H. Effects of pre-ventative footwear on foot pressure as determined by pedobarography in diabetic patients: a prospective study. Diabet Med 2001; 18: 314-319.
15. Grimm A, Kastenbauer T, Sauseng S, Sokol G, Irsigler K. Progression and distribution of plan-tar pressure in Type 2 diabetic patients. Diabetes Nutr Metab 2004; 17: 108-113.
5
abnormalities in neuropathic diabetic subjects. Diabetes Res 1987; 5: 73-77.
17. Dahmen R, van der Wilden GJ, Lankhorst GJ, Boers M. Delphi process yielded consensus on terminology and research agenda for therapeutic footwear for neuropathic foot. J Clin Epi-demiol 2008; 61: 819-826.
18. Arts ML, Bus SA. Twelve steps per foot are recommended for valid and reliable in-shoe plan-tar pressure data in neuropathic diabetic patients wearing custom made footwear. Clin Bio-mech 2011; 26: 880-884.
19. Waaijman R, Bus SA. The interdependency of peak pressure and pressure-time integral in pressure studies on diabetic footwear: no need to report both parameters. Gait Posture 2012; 35: 1-5.
20. Owings TM, Apelqvist J, Stenstrom A, Becker M, Bus SA, Kalpen A, Ulbrecht JS, Cavanagh PR. Plantar pressures in diabetic patients with foot ulcers which have remained healed. Diabet Med 2009; 26: 1141-1146.
21. Goldstein H. Multilivel Statistical Models. London: Edward Arnold, 2003.
22. Foto JG, Birke JA. Evaluation of multidensity orthotic materials used in footwear for patients with diabetes. Foot Ankle Int 1998; 19: 836-841.
23. Paton J, Bruce G, Jones R, Stenhouse E. Effectiveness of insoles used for the prevention of ulceration in the neuropathic diabetic foot: a systematic review. J Diabetes Complications 2011; 25: 52-62.
24. Donaghue VM, Sarnow MR, Giurini JM, Chrzan JS, Habershaw GM, Veves A. Longitudinal in-shoe foot pressure relief achieved by specially designed footwear in high risk diabetic pa-tients. Diabetes Res Clin Pract 1996; 31: 109-114.
25. Cavanagh PR. Therapeutic footwear for people with diabetes. Diabetes Metab Res Rev 2004; 20 Suppl 1: S51-S55.
26. Mueller MJ. Application of plantar pressure assessment in footwear and insert design. J Or-thop Sports Phys Ther 1999; 29: 747-755.
27. Owings TM, Woerner JL, Frampton JD, Cavanagh PR, Botek G. Custom therapeutic insoles based on both foot shape and plantar pressure measurement provide enhanced pressure relief. Diabetes Care 2008; 31: 839-844.
28. Mueller MJ, Smith KE, Commean PK, Robertson DD, Johnson JE. Use of computed tomograp-hy and plantar pressure measurement for management of neuropathic ulcers in patients with diabetes. Phys Ther 1999; 79: 296-307.
