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Use of a three-curved rocker sole shoe modification to improve intermittent claudication calf pain — A pilot study
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Use of a three-curved rocker sole shoe modification to improve intermittent claudication calf pain — A pilot study Stephen William Hutchins, PhD, Gwen Lawrence, BSc(Hons), Stephen Blair, FRCS, Andrey Aksenov, MSc, and Richard Jones, PhD
This was a pilot study utilizing hospital-based walking trials to compare two footwear conditions. Two pairs of identical therapeutic shoes were ordered for volunteer claudicant subjects. One pair was adapted with a specifically designed threecurve rocker sole. Volunteer claudicant subjects (n = 8, mean age 66 +/- 9.9 years) with stable pain-free distances of 10 – 400 meters to calf claudication pain were recruited into the study. Walking trials were used to compare differences in both the pain-free distance to claudication and the intensity of the calf pain once claudicating exhibited by each subject while walking separately with the two footwear conditions during the same clinical session. The results demonstrated that claudicant pain-free walking distance was increased, and the intensity of claudication calf pain reduced when walking with the rocker-soled in comparison with baseline. A specifically designed rocker sole has the potential to offer a reduction in the intensity of calf pain experienced by claudicants. A more extensive study is planned to determine the efficacy of this new footwear adaptation when the footwear is worn for extended periods. (J Vasc Nurs 2012;30:11-20)
Subjects with intermittent claudication (IC) suffer from an inability to walk long distances without experiencing claudication pain in the calf region. IC is a vascular condition that limits the distance patients can walk before experiencing pain in the lower limbs. The word "claudication" is derived from the Latin claudicare, meaning to limp.1 The distance that can be covered before pain commences varies greatly from patient to patient and depends on the severity of the underlying condition. Symptoms mainly occur in the calf, though the thigh and gluteal musculature may also be affected. The symptoms usually disappear after From the Centre for Health Sport and Rehabilitation Research, The University of Salford, Manchester, United Kingdom; Department of Vascular Surgery, Wirral University Hospital NHS Trust, Wirral, United Kingdom. Corresponding author: Stephen W. Hutchins, PhD, Department of Prosthetics, Orthotics and Podiatry, The University of Salford, Manchester, UK (E-mail: [email protected]). Conflict of Interest: A United Kingdom patent application has been submitted by the lead author for the three-curve rocker profile design. Centre for Health Sport and Rehabilitation Research, The University of Salford, Manchester, United Kingdom. This work was funded by the NHS North West Research under the R&D Training Fellowship Scheme, UK and their support for this research is gratefully acknowledged. This paper is our original work and has not been published anywhere else, electronically or in print, nor has it been submitted elsewhere simultaneously for publication. 1062-0303/$36.00 Copyright Ó 2012 by the Society for Vascular Nursing, Inc. doi:10.1016/j.jvn.2011.11.003
a period of rest. McDermott et al (2001) used a flow diagram to classify patients with peripheral vascular disease and leg pain as claudicants (i.e., those patients with intermittent claudication).2 Indicative symptoms were stated as:
Pain in the calf region of the leg Pain that did not resolve with continued walking Pain that went away within 10 minutes of rest. The severity of peripheral artery disease (PAD) may be divided into the Fontaine stages, introduced by Rene Fontaine in 1954 for ischemia.3,4 Subjects with IC fall into one of the 2 subcategories (Stage 11a - severe pain when walking relatively short distances (IC), with pain triggered by walking ‘‘after a distance of > 150 m’’; Stage 11b - severe pain when walking relatively short distances (IC), with pain triggered by walking ‘‘after a distance < 150 m).’’ The condition is caused by PAD in the lower limbs, which limits blood flow. This is secondary in most cases to arteriosclerosis obliterans, a disease adversely affecting the composition of the artery walls. Calf-muscle pain is the most common symptom, usually due to a diseased superficial femoral artery.5 Approximately 40% of patients diagnosed with PAD suffer from IC.6 Because PAD is age related, and because the proportion of the population over 65 years of age is increasing, it can be expected that the prevalence of patients with PAD will increase. Intermittent claudication is most common in men over 60, and 5% of the population develop IC at 50 years of age or over.7 The incidence increases with age due to the progression of disease of the vascular system, which affects the efficiency of the vascular supply to the lower limbs.8 This was confirmed by Leng et al (1995)9 who stated the incidence rate was 4% in the over-55 age range. The reduction in walking capacity experienced by patients with IC can result in a high degree of limitation in mental and physical functioning and in performance of a social role.10
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Current conservative treatment regimes include discontinuation of smoking, walking exercises and optimal drug control of concomitant factors. Structured and supervised PAD rehabilitation involving exercise is a highly efficacious treatment for IC and may be regarded as the current ‘‘gold standard’’ among conservative treatment options.11 Surgical bypass procedures have been the gold standard for surgical treatment of extensive PAD, but percutaneous transluminal angioplasty (PTA) is the most widely applied surgical treatment.12 An adjuvant benefit of PTA over best medical therapy13 and also supervised exercise14,15 in the treatment of IC has also been demonstrated. Approximately 75% of claudicants remain stable in the long term.16 However, claudicant symptoms may fail to improve as significantly as expected, even though they have followed gold standard treatments, such as supervised exercise therapy, especially if the patient continues to smoke and has a high bodymass index (BMI).17 One potential alternative form of treatment could therefore be the use of footwear adaptations. However, there is no current level-1 evidence to support the use of orthotic modifications over or in conjunction with supervised exercise, or indeed other treatment options for claudicants. The purpose of this study was to provide initial evidence by means of a pilot study, about whether the use of a footwear adaptation in the form of a specifically designed rocker sole could potentially increase the distance to claudication (known as the claudication distance) and also to analyze the effect it would have on the intensity of pain while claudicating when worn by volunteer claudicants. The use of footwear adaptations in the treatment of IC has previously been limited to studies involving the use of heel elevators18 or the addition of traditional "angled" rocker soles to footwear.19 The potential efficacy of adding bilateral heel elevators to the shoes of patients with IC arose because they would theoretically place the ankle in an equinous position by altering the pitch of the shoes. However, the results showed no significant improvement in pain-free walking distance in those patients tested and, as such, this type of intervention was not recommended. One published study has used rocker soles to help reduce claudication calf pain.19 However, variable results were demonstrated in increasing the pain-free walking distance for IC subjects. The authors recommended further development of alternative rocker shapes to potentially increase claudication distance. Commercially available footwear such as Masai Barefoot Technology (MBT) shoes are designed with a multicurved rocker profile in the sole and heel, but they are designed to make certain muscles such as the gastrocnemius work harder during walking in comparison with more conventional footwear.20,21 If footwear could be designed to achieve the opposite effect to reduce the symptoms of calf pain associated with IC by incorporating a different multicurved rocker profile to that used in MBT footwear, then this could serve as an adjunct therapy to the alternative treatments currently available. An alternative orthotic intervention could potentially involve the use of thermoplastic cosmetic ankle-foot orthoses (AFOs) designed to prevent ankle joint motion. However, due to the potential loss of the calf-pump mechanism during ambulation when walking with fixed-angle AFOs, these were discounted for use in this pilot study. Therapeutic shoes have demonstrated efficacy in prophylactically protecting the foot in those patients with diabetes mellitus
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and lower limb vascular disease who are at risk of ulceration from excessive plantar pressures in association with total contact inlays.22 Rocker-soled shoes have also been shown to redistribute foot plantar pressures in those patients at risk of tissue stress due to vascular disease because of increased loading of the forefoot structures.23 This paper therefore presents the results of a pilot study designed to give an initial indication of the potential of a threecurve rocker sole added to the base of off-the-shelf (OTS) therapeutic shoes in producing an increase in the pain-free walking distance of claudicants and also a reduction in the intensity of calf-claudication pain. The hypothesis was that when claudicants walked with a specifically designed rocker-soled shoe, symptoms of claudication pain would be reduced in comparison with walking with an identical un-adapted shoe, and the claudication distance would be increased.
METHODS Volunteer claudicants were recruited into this study via attendance at the Lifestyle Management Clinic in the Vascular Department at Wirral University Hospitals NHS Trust, Merseyside, United Kingdom, under the care of a consultant vascular surgeon and a specialist vascular nurse. Approval was granted by the Wirral Hospitals Local Research and Ethics Committee. A patient information sheet (Appendix A) and consent form were inspected and approved for publication. Volunteer subjects were recruited from the lifestylemanagement clinic led by a specialist vascular nurse. They were included in the study if evidence in the clinical notes showed that they had PAD in the femoral artery or more distally and that they showed evidence of claudication pain in the calf area after having walked only within the range of 10 m – 400 m before the onset of calf pain. Subjects who experienced pain in the thighs or buttocks were excluded from the study. Subjects who could not read/write English were not excluded; however, all subjects were over 55 years of age and were able to give informed consent to volunteer for the study. Claudicants were monitored in the clinic for a minimum of 3 months prior to being recruited to ensure that their pain-free walking distance via walking tests had stabilized and also that their ABI had not altered and was not being further improved following daily walking exercise. Subjects were excluded if they had any peripheral neuropathy due to diabetes mellitus; however, other diabetic subjects were not excluded. Further details of the inclusion and exclusion criteria for volunteers in this study are shown in Table 1. All 8 volunteer claudicants recruited had been prescribed aspirin (75 mg) and were receiving statin therapy. One subject suffered from diabetes mellitus. All subjects recruited were in the Fontaine Stage 11a category for IC. Each subject was measured to ascertain their shoe size and width fitting by the same registered (certified) orthotist. Two pairs of stock therapeutic shoes (C. Hanley and Co., Northampton, United Kingdom) were reserved for each subject, 1 for use as a baseline control shoe (Figure 1), and the other to be adapted with a three-curve rocker profile (Figure 2). All shoes were adapted by the same technician using the same materials. The control shoe and the rocker shoe were identical prior to the rocker
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TABLE 1 INCLUSION AND EXCLUSION CRITERIA Inclusion Criteria
Exclusion Criteria
Evidence of claudication pain in one or both calf regions Evidence that both claudication distance and lower limb vascular status were historically stable for at least 3 months and were not being improved significantly by daily walking exercise A documented claudication distance of between 10 m and 400 m and an ankle brachial pressure index (ABPI) of 0.8 or less in the affected lower limb/s Presence of demonstrable claudication with a sudden onset of pain in either one or both calf muscles following painfree ambulation There was no history of lower limb joint replacement
Evidence of lower limb pain during rest A documented history of cerebral vascular accident (CVA) or any other pathology that adversely affected walking pattern or balance
sole was added in order to isolate the effect of the rocker profile during the walking trials. It was thought that had the patient worn their own shoes as a control condition, then other parameters, such as the fit of the shoe, its length and the style and design of the upper and materials used, would negate the possibility of a direct comparison. Any demonstrated alterations to the symptoms associated with intermittent claudication would then result from the alteration to the sole and heel in comparison with an identical shoe, rather than to a change in the shoe, and would negate any influences associated with alteration to shoe fit and style (especially the way in which it held the foot in the shoe). The results of a previous study involving healthy volunteer subjects when walking with this rocker sole adaptation,24 demonstrated that it significantly reduced the power generation and absorption at the ankle required to walk at self-selected walking speeds. The rocker profile was specifically designed to place the foot into relative plantar flexion during stance phase of gait in comparison with baseline walking while simultaneously reducing sagittal plane ankle motion (Figure 3). The radius of the 3 curves comprising the rocker profile were designed to be centered on the sagittal plane centers of the ankle, hip and knee, respectively, during the transition through stance phase of gait. This method placed the deepest part of the rocker sole directly underneath the ankle joint and enticed the shoe to roll gently forwards. This would theoretically reduce the extent of work done by the muscles acting anteriorly and posteriorly on each joint in turn by reducing the externally applied moments acting on them. This was because the line of action of the ground reaction force passed closer to the anatomical joint centers in comparison with an unadapted shoe. In this way, the lower limb muscles acting on these joints would feasibly require a lower oxygen demand (although that was not tested). Physiologically, the shoe was designed to potentially reduce the work that needed to be done by the lower limb muscles during ambulation (in particular the gastrocnemius medial and lateral
The presence of gross foot deformities that would prevent fitting of the shoes used in the study The presence of orthopedic or neurological impairments that adversely affected their gait, including the presence of a leg-length discrepancy. Claudication pain in the thighs or ankles head), while still allowing the calf-pump mechanism to provide venous return up the leg. It is known that the most efficient position for a muscle to provide contractile force is at its resting length (i.e., not lengthened or shortened). For the gastrocnemius, the resting length is when the ankle is at 90 degrees (i.e., neither plantarflexed or dorsiflexed).25 Analysis of the effect of the threecurve rocker profile on ankle angles during ambulation by 12 healthy subjects demonstrated that it placed the ankle in a mean position of 1 degree of plantarflexion at mid stance (50% of stance phase of gait) in comparison with 5 degrees of dorsiflexion in an identical unadapted shoe.24 It therefore placed the ankle into a position relatively plantarflexed by 6 degrees than in an unadapted shoe at that point in the gait cycle, and thus nearer to the most efficient point in the range of motion (ROM) of the gastrocnemius. In addition, it also reduced the moment arm of the externally applied ground reaction force acting at the ankle. This meant that less concentric contraction would be needed during the propulsive phase. Physiologically, the moment lever arm from the ankle joint center to the Achilles tendon position is at its most advantageous position between 0 and 8 degrees of plantarflexion, making the muscle action more efficient by requiring less force generation to provide the same moment around the ankle.26,27 The threecurve rocker sole addition therefore achieved this. All subjects were tested while walking along a flat, level hospital corridor at their self-selected comfortable walking speed from a fixed starting position. The hospital corridor chosen for the study was straight, flat and uninterrupted. Volunteer subjects walked with a vascular specialist nurse in attendance. The first of the 2 walking trials was randomized for each volunteer subject as either the baseline shoe condition or the rocker profile shoe to neutralize any carryover effects. However, such carryover effects have been proven in the literature to be negligible for other rocker profiles.28-31 A 5-minute period of acclimatization to the shoe was allowed before each walking test. This was done by asking the patient to stand initially to ensure that the shoes were comfortable and to test the fit. Then slow, short steps
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Figure 1. Baseline unadapted shoe.
Figure 2. The three-curve rocker profile.
were allowed in the clinic room to make sure that the shoes did not slip at the back, were secured correctly, and the subject could walk safely in them without feeling unsteady. Volunteer subjects were asked to rest for 20 minutes before commencing the short period of acclimatization and each walk. This 20-minute rest to recuperate before each walking trial was necessary to ensure their lower limb oxygen levels were at baseline resting level along with their arterial pressure immediately prior to walking. This was done following evidence in the literature that indicated that 20 minutes’ rest was more than adequate to facilitate return to baseline values.32 Neither the lower limb O2 levels nor the arterial pressure were measured during the walking trials. The subjects were then invited to commence their walk at their self-selected comfortable walking speed. At the point of sudden onset of claudication pain, subjects were asked to walk immediately around in a circle and walk back along the same corridor to the starting position or until they felt they had to stop. This enabled an estimation of the effect of the three-curve rocker profile on the intensity of claudication pain in comparison with the baseline condition. All subjects were able to walk back to the starting position without pausing or stopping and were asked to sit and rest once they had arrived back at the starting position. It was decided not to formally test patients
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Figure 3. Illustration of curve parameters for the three-curve rocker design used in this study.
to determine their maximum walking distance (MWD) before having to stop, because it was thought that the IC distance (ICD) could be accurately documented and measured using the instant that sudden onset of calf pain occurred. This could not be controlled by the volunteer subject. The MWD was thought to be more subjective by involving input from the volunteer. Using a visual analogue scale (VAS), as shown in Figures 4 and 5, the subjects were asked to give an indication of the intensity of their calf claudication pain experienced while walking back to their original starting position for both test conditions. This was therefore assessed when walking with both the baseline unadapted shoe and the rocker profile condition. By using the sliding mechanism on the scale, they arrived at a position that reflected their pain level during claudication. A reading from the scale on the reverse side of the VAS between 1 and 10 (10 being the worst pain) was recorded. The subjects were unaware of the results and only saw the indicators on the front face of the VAS. None of the subjects reported any discomfort or unsteadiness when wearing the shoes, and no problems with acceptability of the adapted shoes by the volunteers were reported. The precise total distance to claudication was measured using a pedometer/stepometer. (Figure 6: Model - ‘‘MiniMeasure,’’ Trumeter, Leeds, United Kingdom). The distance to the onset of claudication was recorded in meters. The walking trials for both conditions (baseline versus threecurve rocker profile) were randomized and took place during the same clinical session to provide an optimal comparison between the 2 test conditions in preference to inter-day testing.33,34
RESULTS Eight patients undertook the pilot walking trials. Seven patients were male, and 1 was female. Table 2 shows the demographics for the volunteer claudicant group. Primary outcome measures were pain-free walking distance to the onset of calf claudication pain and the severity of pain once claudicating for either test condition. All data were analyzed using SPSS (version 13.0) with a repeated measures analysis of variance. The significance level was
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Figure 4. The VAS mechanism as seen by the volunteer subjects.
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Figure 6. Claudication distance measuring device.
TABLE 2 VOLUNTEER CLAUDICANT DEMOGRAPHICS Parameter
Value
Gender Age Height Mass
7 Male; 1 Female 66 +/ 9.9 years 1.73 +/ 0.1 m 87.7 +/ 17.2 kg
Figure 5. The VAS sliding mechanism showing the numerical scale.
set at P < 0.05 with post-hoc Bonferroni correction used to reduce the chance of type 1 errors.
Claudication distance All claudicants tested (n = 8) demonstrated a significant increase (P = 0.01) in pain-free claudication distance when walking with the three-curve rocker profile adaptation in comparison with baseline. Figure 7 illustrates a comparison of the improvement in the claudication distance achieved when wearing the three-curve rocker test condition. The mean claudication distance increased from 31.59 m to 66.40 m; a mean increase of 34.81 m.
Intensity of claudication pain The intensity of calf pain once claudicating demonstrated a statistically significant reduction (P = 0.00) when walking with the three-curve rocker profile in comparison with baseline (Figure 8). All claudicants registered a reduction in the severity of claudication pain based on the VAS scale. The claudication pain in all cases occurred in the same area of the calf for both test conditions. The mean pain reduction as indicated by the VAS scoring was reduced from a value of 7.75 on a scale of 1 to 10 in severity of pain. Volunteer claudicants indicated a mean reduction of 3.3
from their pain score for the baseline condition while claudicating. The VAS calf pain score while wearing the baseline unadapted shoes was remarkably consistent (mean 7.75, standard deviation (SD) 0.87). The mean VAS calf pain score when walking with the rocker-soled shoes was 4.41 (SD 1.64). The results therefore demonstrated that walking with the three-curve rocker profile condition increased the pain-free walking distance to claudication in all subjects tested (P = 0.008) and substantially decreased the severity of calf pain once claudication had commenced (P = 0.002). A summary table with the mean findings is shown in Table 3.
DISCUSSION This pilot study was designed to gain a first indication of the clinical relevance of adding a rocker sole profile to footwear to potentially reduce the intensity of calf claudication pain and to increase the pain-free ICD. It was also designed to indicate the subject numbers required for a randomized controlled clinical trial. All claudicants demonstrated an increased ICD with the rocker-soled shoe. All of the claudicants who volunteered for the study also regarded the cosmetic appearance of the threecurve rocker acceptable, and none of the subjects reported any feeling of unsteadiness or discomfort during the walking trials. In addition, no subjects reported discomfort in the hips or back
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TABLE 3 SUMMARY OF RESULTS Claudication Distance (m)
Figure 7. Comparison of walking distance for volunteer claudicants during the three-curve rocker-profile test condition in comparison with baseline.
Patient Number
Baseline
Three-Curve Rocker
1 2 3 4 5 6 7 8
30.64 49.68 56.94 14.48 11 101.1 36.03 81.88 47.72 31.59
43.17 58.6 99.71 19.74 23.86 130.28 69.24 86.66 66.4 35.7
Mean Standard Deviation
VAS Claudication Pain Scores
Patient Number
Figure 8. VAS pain score reductions demonstrated during walking trials.
during the walking trials, and no long-term complications are envisioned. Biomechanical analysis of this three-curve rocker profile in a previous study, along with healthy subjects walking in shoes adapted with it under gait laboratory conditions, demonstrated a reduction in the sagittal plane power absorption and power generation required to walk at the ankle and the knee in comparison with an unadapted shoe.24 It was anticipated that such a reduction would translate into increased pain-free walking distance by claudicants. The important finding for this study was that biomechanically modifying claudicant gait via the application of a specific rocker profile resulted in a significantly increased ICD in all the subjects as well as a substantial reduction in the intensity of their pain levels once claudicating. The walking tests utilized a long, straight hospital corridor. Although it is conceded that treadmill testing is currently the most widely used measurement technique for repeated measurement of ICD and MWD, constant-load treadmill walking tests have been shown by some researchers to be more variable than walking tests.35,36 Furthermore, the magnitude and variability of MWD and ICD change with test familiarization and habituation. Level-treadmill tests have been shown to underesti-
1 2 3 4 5 6 7 8 Mean Standard Deviation
VAS Score Baseline
VAS Score Rocker Condition
6.4 8.1 8.4 8.1 8.5 6.6 7.3 8.6 7.75 0.87
5.4 3.3 5.1 3.2 4.5 2.7 3.4 7.7 4.41 1.54
mate the maximum walking distance by over 40% in comparison with active walking on a level surface.37,38 The use of walking along a level surface was therefore thought to be an appropriate alternative means of assessing individual patients for this study, although it is appreciated that treadmills can also simulate uphill walking and are routinely used in clinical practice. Walking on inclined surfaces would theoretically produce calf-pain symptoms earlier than walking on a flat surface, and this needs to be investigated in a future study of participants walking on various slopes under controlled conditions with the 2 test-shoe conditions described in this study. The results nevertheless gave the authors an indication of the number of volunteer subjects required for, and the confidence to
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proceed to, a randomized controlled trial for claudicants walking with a three-curve rocker sole profile added to their footwear during their daily activities. The encouraging finding of significant reduction in the intensity of the calf pain once claudicating indicated that the gastrocnemius muscle may have been offloaded due to the fact that the three-curve rocker sole is designed to facilitate a gentle forward roll of the foot during stance without being too unstable; it is also designed to position the muscle in a more advantageous position during mid- to late-stance phase of gait when in contact with the ground during the propulsion phase. However, this probable unloading effect is yet unproven. A further study is also planned to investigate this phenomenon. No adverse reactions were reported during these walking tests, and none were encountered during a previous study. Therefore, It would be interesting to investigate the alteration in severity of claudication pain and the achievable walking distance achieved by claudicants following a randomized controlled trial while they were walking with the profile over an extended period. Increased habituation may also alter the pain-free walking distance, but the long-term effects of the rocker-soled shoe on gait parameters are yet also unknown. The pain-free ICD was quantified as a primary outcome measure to enable a direct comparison of data relating to the sudden onset of pain. This was an outcome measure that could be accurately quantified and not easily controlled by the volunteer claudicant and therefore not subjective. The MWD was not included as a primary outcome measure in preference to the severity of the pain while claudicating. It is, however, conceded that this parameter is one that is routinely measured.
Limitations of the study The limitations of this study are the limited number of subjects (n = 8) included in the study and therefore the lack of available data produced to perform extensive statistical analysis based on the results, because the data may not have had a normal distribution. It was not therefore possible, for instance, to link severity of disease to potential improvement of symptoms when walking with the rocker-sole profile added to the base of the shoe. Both the patient and the investigators were also unblinded. Another limitation was the decision not to analyze the MWD of the volunteer claudicants. However, all the subjects who volunteered for the study were able to walk without stopping back to the original starting point after experiencing claudication pain.
CONCLUSION This pilot study demonstrated the potential for an adapted shoe to help reduce the intensity of claudication calf pain and to enable claudicants to walk further before experiencing calf pain. Further research is therefore warranted to develop rockersole profiles to be added to footwear to help reduce the symptoms experienced by claudicants and possibly other patient groups, such as those with Achilles tendonitis.
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ACKNOWLEDGMENTS This work was funded by the NHS Executive North West, UK under the R&D Training Fellowship scheme and their assistance in producing this work is gratefully acknowledged. The sponsors were not involved in any aspect of the study.
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ric plantarflexion: in vivo observations in man. J Physiol 1998;510(3):977-85. Myers KA, Long JT, Klein JP, et al. Biomechanical implications of the negative heel rocker sole shoe: Gait kinematics and kinetics. Gait Posture 2006;24(3):323-30. Brown D, Wertsch J, Harris G, et al. Effect of rocker soles on plantar pressures. Arch Phys Med Rehabil 2004;85: 81-6. Wertsch JJ, Harris GF, Janisse DJ, et al. Effect of double rocker, toe-only and heel rocker soles (abstract). Am J Phys Med Rehabil 2000;79:218. Van Bogart J, Long J, Klein J, et al. Effects of the toe-only rocker on gait kinematics and kinetics in able-bodied persons. IEEE Tansactions on Neural Systems and Rehab Eng 2005;13(4):542-50. Comerota A, Throm B, Kelly P, et al. Tissue (muscle) oxygen saturation (StO2): A new measure of symptomatic lower-extremity arterial disease. J Vasc Surg 2003;38(4): 724-9. Kadaba MP, Ramkrishnan HJ, Wooten ME, et al. Repeatability of kinematic kinetic and electromyographic data in normal adult gait. J Orthop Res 1989;7(6):849-60. Winter D, Yack H. EMG profiles during normal human walking: stride to stride and inter-subject variability. Electroencephalogr Clin Neurophysiol 1987;67(5):402-11. Gardner AW, Skinner JS, Cantwell BW, et al. Progressive versus single-stage treadmill tests for evaluation of claudication. Med Sci Sports Exerc 1991;23:402-8. Labs KH, Nehler MR, Roessner M, et al. Reliability of treadmill testing in peripheral arterial disease: a comparison of a constant load with a graded load treadmill protocol. Vasc Med 1999;4:239-46. Gardner AW, Skinner JS, Smith LK. Effects of handrail support on claudication and hemodynamic responses to single-stage and progressive treadmill protocols in peripheral vascular occlusive disease. Am J Cardiol 1991;68: 99-105. Labs KH, Dormandy JA, Jaeger KA, et al. Transatlantic Conference on Clinical Trial Guidelines in Peripheral Arterial Disease: clinical trial methodology. Basel PAD Clinical Trial Methodology Group. Circulation 1999;100: 75-81.
APPENDIX A. PATIENT INFORMATION SHEET 1. Project Title The use of rocker (clog-shaped) soles to shoes in the treatment of patients with pain in the lower limb when walking (those with intermittent claudication).
2. You are being invited to take part in a research study. Before you decide it is important for you to understand why the research is being done and what it will involve. Please take time to read the following information carefully and discuss it with fiends, relatives and your GP if you wish. Ask us if there is anything that is not clear or if you would like more information. Please take time to decide whether or
not you wish to take part. Consumers for ethics in research (CERES) publish a leaflet entitled ‘‘Medical Research and you.’’ This leaflet gives more information about medical research and looks at some questions you may want to ask. A copy may be obtained from: CERES, PO Box 1365, London, N16 0BW. Thank you for reading this. 3. The Purpose of the Study. The purpose of the study is to try to find out if the addition of a rocker sole (which looks like a clogg-shape) to patients who experience leg pain can help them walk better and potentially further. Patients who get a pain in the calf when they have walked a certain distance may well benefit from this alteration to their shoes.
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4. Why have you been asked? You have been chosen for the project because you suffer from leg pain on walking due to intermittent claudication, and have got to a stage where the distance you can walk without pain in the leg does not vary much. It is hoped to test at least 50 patients. 5. Do you have to take part? It is up to you to decide whether or not to take part. If you decide to take part, you will be given this patient information sheet to keep, and be asked to sign a consent form. If you decide to take part you are still free to withdraw at any time and without giving a reason. This will not affect the standard of care you receive. 6. What will happen to you if you take part? The study will last for three years but your help in the project will only be required over a three-month period which will entail a number of visits to Arrowe Park Hospital and possibly the gait laboratory in The University of Salford. The visit to the gait laboratory will only be offered to a small number of patients. You will only be involved over four separate days within a three-month period at Arrowe Park Hospital. Depending on whether or not you are selected and agree to travel to Salford there may be an additional day involved. During these four or five days you will be involved in the following activities: Visit 1: Arrowe Park Hospital During the first day you will initially be assessed as being suitable for the project. We will need to watch you walking to make sure that you do not have a limp due to conditions other than intermittent claudication, and that your overall condition will allow you to walk certain distances (between 15 and 400 yards) to the onset of pain due to intermittent claudication in your lower leg. We will do this at Arrowe Park Hospital. You will then be measured for a pair of made-tomeasure shoes, which you may keep after the testing. There will be no charge for the shoes. The shoes will be used to allow us to conveniently add the rocker-sole shape to the footwear. The rocker sole will be removed afterwards at the end of the final testing period if you wish. Visit 2: Arrowe Park Hospital On this visit, you will be supplied with the specially made shoes and asked to walk a short distance to make sure they are comfortable. On this visit, we will also ask you to walk along a long flat corridor to measure the distance you can walk until the onset of pain in your lower leg whilst wearing the made to measure shoes. After a short period of rest we will ask you to walk along the same corridor wearing the same pair of shoes, but with the rocker shape added. We hope this will allow you to walk a lot further before experiencing the calf pain. The study method will be to simply see if the addition of the rocker sole helps you walk further before the onset of pain in your leg than without it added on the same pair of shoes.
7. What do you have to do? There are no lifestyle or dietary restrictions. You can do all your normal activities such as
8.
9.
10.
11. 12.
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driving or taking part in sport. If you are on regular medication we would wish you to continue taking it. What is the procedure that is being tested? The rocker sole is a profiled shape added to the bottom of the sole of a shoe. It is designed to reduce the work done by the calf muscles when walking. It encourages the foot to roll forwards instead of using the calf muscles so much, and as such theoretically reduces the work done by the calf muscles in walking a set distance. We are hoping to test the theory that rocker soles help patients with pain in the lower limb to walk further before the onset of pain because the calf muscles should not have to work so hard. What are the alternatives for diagnosis or treatment? You will already have been diagnosed as having intermittent claudication to be included in the study. Alternative forms of treatment apart from using rocker soles include exercise regimes, drug therapy and in some cases, surgery. What are the side effects of taking part? There should be no side effects of taking part. Indeed, we hope to prove that the addition of rocker soles will be of benefit to you. However, we will not insist that you continue wearing the rocker-soled shoes should they prove to be beneficial. We will remove the rocker soled shape from the bottom of the shoes for you should you wish us to do so, and you may keep the shoes once the testing has been completed. There will be no charge for the shoes or alterations done to them. What are the possible disadvantages of taking part? There should be no disadvantages of taking part. What are the possible benefits of taking part? We hope that the treatment will help you. However, this can not be guaranteed. The information we get from this study may help us to treat future patients with intermittent claudication more effectively. What if new information becomes available? Sometimes, during the course of a research project, new information becomes available about the treatment that is being studied. If this happens, your research fellow will tell you about it and discuss with you whether you want to continue in the study. If you decide to withdraw your research fellow will make arrangements for your care to continue. If you decide to continue in the study you will be asked to sign an updated consent form.
Also, on receiving new information your research fellow might consider it to be in your best interests to withdraw you from the study. He/she will explain the reasons and arrange for your care to continue.
14. What happens when the research study stops? The treatment should be available on the NHS if you decide to continue with the addition of rocker soles to your shoes. It is unlikely however that they will pay for an additional pair of made-to-measure shoes unless you have a foot problem. They will, however, be able to add rocker soles onto a suitable pair of your own shoes free of charge.
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15. What if something goes wrong? Complaints as to your treatment by members of staff in the NHS or University of Salford will be handled by an independent person who will investigate the facts. If you are harmed by taking part in this research project, there are no special compensation arrangements. If you are harmed due to someone’s negligence, then you may have grounds for a legal action but you may have to pay for it. Regardless of this, if you wish to complain about any aspect of the way you have been approached or treated during the course of this study, the normal National Health Service complaints mechanisms may be available to you. 16. Will my taking part in this study be kept confidential? All information, which will be collected about you during the course of the research, will be kept strictly confidential. Any information about you which leaves the hospital/ university will have your name and address removed so that you cannot be recognised from it. Your GP will be notified of your participation in the trial, along with any medical practitioners not involved in the research who may be treating you. Do you agree to this? Yes/No 17. What will happen to the results of the research study? The results will be published in a research paper and will be used to write a PhD Thesis. The results are likely to be published at the end of the four-year period i.e. June 2003. You will be informed where and when the results
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are published. (You will not be identified in any publication/thesis). 18. Who is organising and funding the research? The research is being funded by N.H.S. Executive North West Research and Development Directorate. The funding body will pay for the salary replacement costs of the Research Fellow for an equivalent of two days per week for the duration of the study. The research Fellow will be organising the study and will involve colleagues at the University of Salford and other departments such as the Appliance Office and Orthopaedic and Surgical Directorate at Arrowe Park Hospital. 19. Who has reviewed the study? The study has been reviewed by the N.H.S. Executive North West Research and Development Directorate, and has been sent for peer review by two independent experts. The Wirral Health Authority Research Ethics Committee and The University of Salford Ethics Committee have also reviewed the study. Please contact Stephen Hutchins at The University of Salford: telephone number 0161 295 2320 or Mrs Lord, Appliance Officer, Arrowe Park Hospital on 0151 604 7092. Thank you for taking part in the study. April 2000 No. 1 You will be given a copy of the information sheet and a signed consent form to keep.
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Use of a three-curved rocker sole shoe modification to improve intermittent claudication calf pain — A pilot study Stephen William Hutchins, PhD, Gwen Lawrence, BSc(Hons), Stephen Blair, FRCS, Andrey Aksenov, MSc, and Richard Jones, PhD
This was a pilot study utilizing hospital-based walking trials to compare two footwear conditions. Two pairs of identical therapeutic shoes were ordered for volunteer claudicant subjects. One pair was adapted with a specifically designed threecurve rocker sole. Volunteer claudicant subjects (n = 8, mean age 66 +/- 9.9 years) with stable pain-free distances of 10 – 400 meters to calf claudication pain were recruited into the study. Walking trials were used to compare differences in both the pain-free distance to claudication and the intensity of the calf pain once claudicating exhibited by each subject while walking separately with the two footwear conditions during the same clinical session. The results demonstrated that claudicant pain-free walking distance was increased, and the intensity of claudication calf pain reduced when walking with the rocker-soled in comparison with baseline. A specifically designed rocker sole has the potential to offer a reduction in the intensity of calf pain experienced by claudicants. A more extensive study is planned to determine the efficacy of this new footwear adaptation when the footwear is worn for extended periods. (J Vasc Nurs 2012;30:11-20)
Subjects with intermittent claudication (IC) suffer from an inability to walk long distances without experiencing claudication pain in the calf region. IC is a vascular condition that limits the distance patients can walk before experiencing pain in the lower limbs. The word "claudication" is derived from the Latin claudicare, meaning to limp.1 The distance that can be covered before pain commences varies greatly from patient to patient and depends on the severity of the underlying condition. Symptoms mainly occur in the calf, though the thigh and gluteal musculature may also be affected. The symptoms usually disappear after From the Centre for Health Sport and Rehabilitation Research, The University of Salford, Manchester, United Kingdom; Department of Vascular Surgery, Wirral University Hospital NHS Trust, Wirral, United Kingdom. Corresponding author: Stephen W. Hutchins, PhD, Department of Prosthetics, Orthotics and Podiatry, The University of Salford, Manchester, UK (E-mail: [email protected]). Conflict of Interest: A United Kingdom patent application has been submitted by the lead author for the three-curve rocker profile design. Centre for Health Sport and Rehabilitation Research, The University of Salford, Manchester, United Kingdom. This work was funded by the NHS North West Research under the R&D Training Fellowship Scheme, UK and their support for this research is gratefully acknowledged. This paper is our original work and has not been published anywhere else, electronically or in print, nor has it been submitted elsewhere simultaneously for publication. 1062-0303/$36.00 Copyright Ó 2012 by the Society for Vascular Nursing, Inc. doi:10.1016/j.jvn.2011.11.003
a period of rest. McDermott et al (2001) used a flow diagram to classify patients with peripheral vascular disease and leg pain as claudicants (i.e., those patients with intermittent claudication).2 Indicative symptoms were stated as:
Pain in the calf region of the leg Pain that did not resolve with continued walking Pain that went away within 10 minutes of rest. The severity of peripheral artery disease (PAD) may be divided into the Fontaine stages, introduced by Rene Fontaine in 1954 for ischemia.3,4 Subjects with IC fall into one of the 2 subcategories (Stage 11a - severe pain when walking relatively short distances (IC), with pain triggered by walking ‘‘after a distance of > 150 m’’; Stage 11b - severe pain when walking relatively short distances (IC), with pain triggered by walking ‘‘after a distance < 150 m).’’ The condition is caused by PAD in the lower limbs, which limits blood flow. This is secondary in most cases to arteriosclerosis obliterans, a disease adversely affecting the composition of the artery walls. Calf-muscle pain is the most common symptom, usually due to a diseased superficial femoral artery.5 Approximately 40% of patients diagnosed with PAD suffer from IC.6 Because PAD is age related, and because the proportion of the population over 65 years of age is increasing, it can be expected that the prevalence of patients with PAD will increase. Intermittent claudication is most common in men over 60, and 5% of the population develop IC at 50 years of age or over.7 The incidence increases with age due to the progression of disease of the vascular system, which affects the efficiency of the vascular supply to the lower limbs.8 This was confirmed by Leng et al (1995)9 who stated the incidence rate was 4% in the over-55 age range. The reduction in walking capacity experienced by patients with IC can result in a high degree of limitation in mental and physical functioning and in performance of a social role.10
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Current conservative treatment regimes include discontinuation of smoking, walking exercises and optimal drug control of concomitant factors. Structured and supervised PAD rehabilitation involving exercise is a highly efficacious treatment for IC and may be regarded as the current ‘‘gold standard’’ among conservative treatment options.11 Surgical bypass procedures have been the gold standard for surgical treatment of extensive PAD, but percutaneous transluminal angioplasty (PTA) is the most widely applied surgical treatment.12 An adjuvant benefit of PTA over best medical therapy13 and also supervised exercise14,15 in the treatment of IC has also been demonstrated. Approximately 75% of claudicants remain stable in the long term.16 However, claudicant symptoms may fail to improve as significantly as expected, even though they have followed gold standard treatments, such as supervised exercise therapy, especially if the patient continues to smoke and has a high bodymass index (BMI).17 One potential alternative form of treatment could therefore be the use of footwear adaptations. However, there is no current level-1 evidence to support the use of orthotic modifications over or in conjunction with supervised exercise, or indeed other treatment options for claudicants. The purpose of this study was to provide initial evidence by means of a pilot study, about whether the use of a footwear adaptation in the form of a specifically designed rocker sole could potentially increase the distance to claudication (known as the claudication distance) and also to analyze the effect it would have on the intensity of pain while claudicating when worn by volunteer claudicants. The use of footwear adaptations in the treatment of IC has previously been limited to studies involving the use of heel elevators18 or the addition of traditional "angled" rocker soles to footwear.19 The potential efficacy of adding bilateral heel elevators to the shoes of patients with IC arose because they would theoretically place the ankle in an equinous position by altering the pitch of the shoes. However, the results showed no significant improvement in pain-free walking distance in those patients tested and, as such, this type of intervention was not recommended. One published study has used rocker soles to help reduce claudication calf pain.19 However, variable results were demonstrated in increasing the pain-free walking distance for IC subjects. The authors recommended further development of alternative rocker shapes to potentially increase claudication distance. Commercially available footwear such as Masai Barefoot Technology (MBT) shoes are designed with a multicurved rocker profile in the sole and heel, but they are designed to make certain muscles such as the gastrocnemius work harder during walking in comparison with more conventional footwear.20,21 If footwear could be designed to achieve the opposite effect to reduce the symptoms of calf pain associated with IC by incorporating a different multicurved rocker profile to that used in MBT footwear, then this could serve as an adjunct therapy to the alternative treatments currently available. An alternative orthotic intervention could potentially involve the use of thermoplastic cosmetic ankle-foot orthoses (AFOs) designed to prevent ankle joint motion. However, due to the potential loss of the calf-pump mechanism during ambulation when walking with fixed-angle AFOs, these were discounted for use in this pilot study. Therapeutic shoes have demonstrated efficacy in prophylactically protecting the foot in those patients with diabetes mellitus
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and lower limb vascular disease who are at risk of ulceration from excessive plantar pressures in association with total contact inlays.22 Rocker-soled shoes have also been shown to redistribute foot plantar pressures in those patients at risk of tissue stress due to vascular disease because of increased loading of the forefoot structures.23 This paper therefore presents the results of a pilot study designed to give an initial indication of the potential of a threecurve rocker sole added to the base of off-the-shelf (OTS) therapeutic shoes in producing an increase in the pain-free walking distance of claudicants and also a reduction in the intensity of calf-claudication pain. The hypothesis was that when claudicants walked with a specifically designed rocker-soled shoe, symptoms of claudication pain would be reduced in comparison with walking with an identical un-adapted shoe, and the claudication distance would be increased.
METHODS Volunteer claudicants were recruited into this study via attendance at the Lifestyle Management Clinic in the Vascular Department at Wirral University Hospitals NHS Trust, Merseyside, United Kingdom, under the care of a consultant vascular surgeon and a specialist vascular nurse. Approval was granted by the Wirral Hospitals Local Research and Ethics Committee. A patient information sheet (Appendix A) and consent form were inspected and approved for publication. Volunteer subjects were recruited from the lifestylemanagement clinic led by a specialist vascular nurse. They were included in the study if evidence in the clinical notes showed that they had PAD in the femoral artery or more distally and that they showed evidence of claudication pain in the calf area after having walked only within the range of 10 m – 400 m before the onset of calf pain. Subjects who experienced pain in the thighs or buttocks were excluded from the study. Subjects who could not read/write English were not excluded; however, all subjects were over 55 years of age and were able to give informed consent to volunteer for the study. Claudicants were monitored in the clinic for a minimum of 3 months prior to being recruited to ensure that their pain-free walking distance via walking tests had stabilized and also that their ABI had not altered and was not being further improved following daily walking exercise. Subjects were excluded if they had any peripheral neuropathy due to diabetes mellitus; however, other diabetic subjects were not excluded. Further details of the inclusion and exclusion criteria for volunteers in this study are shown in Table 1. All 8 volunteer claudicants recruited had been prescribed aspirin (75 mg) and were receiving statin therapy. One subject suffered from diabetes mellitus. All subjects recruited were in the Fontaine Stage 11a category for IC. Each subject was measured to ascertain their shoe size and width fitting by the same registered (certified) orthotist. Two pairs of stock therapeutic shoes (C. Hanley and Co., Northampton, United Kingdom) were reserved for each subject, 1 for use as a baseline control shoe (Figure 1), and the other to be adapted with a three-curve rocker profile (Figure 2). All shoes were adapted by the same technician using the same materials. The control shoe and the rocker shoe were identical prior to the rocker
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TABLE 1 INCLUSION AND EXCLUSION CRITERIA Inclusion Criteria
Exclusion Criteria
Evidence of claudication pain in one or both calf regions Evidence that both claudication distance and lower limb vascular status were historically stable for at least 3 months and were not being improved significantly by daily walking exercise A documented claudication distance of between 10 m and 400 m and an ankle brachial pressure index (ABPI) of 0.8 or less in the affected lower limb/s Presence of demonstrable claudication with a sudden onset of pain in either one or both calf muscles following painfree ambulation There was no history of lower limb joint replacement
Evidence of lower limb pain during rest A documented history of cerebral vascular accident (CVA) or any other pathology that adversely affected walking pattern or balance
sole was added in order to isolate the effect of the rocker profile during the walking trials. It was thought that had the patient worn their own shoes as a control condition, then other parameters, such as the fit of the shoe, its length and the style and design of the upper and materials used, would negate the possibility of a direct comparison. Any demonstrated alterations to the symptoms associated with intermittent claudication would then result from the alteration to the sole and heel in comparison with an identical shoe, rather than to a change in the shoe, and would negate any influences associated with alteration to shoe fit and style (especially the way in which it held the foot in the shoe). The results of a previous study involving healthy volunteer subjects when walking with this rocker sole adaptation,24 demonstrated that it significantly reduced the power generation and absorption at the ankle required to walk at self-selected walking speeds. The rocker profile was specifically designed to place the foot into relative plantar flexion during stance phase of gait in comparison with baseline walking while simultaneously reducing sagittal plane ankle motion (Figure 3). The radius of the 3 curves comprising the rocker profile were designed to be centered on the sagittal plane centers of the ankle, hip and knee, respectively, during the transition through stance phase of gait. This method placed the deepest part of the rocker sole directly underneath the ankle joint and enticed the shoe to roll gently forwards. This would theoretically reduce the extent of work done by the muscles acting anteriorly and posteriorly on each joint in turn by reducing the externally applied moments acting on them. This was because the line of action of the ground reaction force passed closer to the anatomical joint centers in comparison with an unadapted shoe. In this way, the lower limb muscles acting on these joints would feasibly require a lower oxygen demand (although that was not tested). Physiologically, the shoe was designed to potentially reduce the work that needed to be done by the lower limb muscles during ambulation (in particular the gastrocnemius medial and lateral
The presence of gross foot deformities that would prevent fitting of the shoes used in the study The presence of orthopedic or neurological impairments that adversely affected their gait, including the presence of a leg-length discrepancy. Claudication pain in the thighs or ankles head), while still allowing the calf-pump mechanism to provide venous return up the leg. It is known that the most efficient position for a muscle to provide contractile force is at its resting length (i.e., not lengthened or shortened). For the gastrocnemius, the resting length is when the ankle is at 90 degrees (i.e., neither plantarflexed or dorsiflexed).25 Analysis of the effect of the threecurve rocker profile on ankle angles during ambulation by 12 healthy subjects demonstrated that it placed the ankle in a mean position of 1 degree of plantarflexion at mid stance (50% of stance phase of gait) in comparison with 5 degrees of dorsiflexion in an identical unadapted shoe.24 It therefore placed the ankle into a position relatively plantarflexed by 6 degrees than in an unadapted shoe at that point in the gait cycle, and thus nearer to the most efficient point in the range of motion (ROM) of the gastrocnemius. In addition, it also reduced the moment arm of the externally applied ground reaction force acting at the ankle. This meant that less concentric contraction would be needed during the propulsive phase. Physiologically, the moment lever arm from the ankle joint center to the Achilles tendon position is at its most advantageous position between 0 and 8 degrees of plantarflexion, making the muscle action more efficient by requiring less force generation to provide the same moment around the ankle.26,27 The threecurve rocker sole addition therefore achieved this. All subjects were tested while walking along a flat, level hospital corridor at their self-selected comfortable walking speed from a fixed starting position. The hospital corridor chosen for the study was straight, flat and uninterrupted. Volunteer subjects walked with a vascular specialist nurse in attendance. The first of the 2 walking trials was randomized for each volunteer subject as either the baseline shoe condition or the rocker profile shoe to neutralize any carryover effects. However, such carryover effects have been proven in the literature to be negligible for other rocker profiles.28-31 A 5-minute period of acclimatization to the shoe was allowed before each walking test. This was done by asking the patient to stand initially to ensure that the shoes were comfortable and to test the fit. Then slow, short steps
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Figure 1. Baseline unadapted shoe.
Figure 2. The three-curve rocker profile.
were allowed in the clinic room to make sure that the shoes did not slip at the back, were secured correctly, and the subject could walk safely in them without feeling unsteady. Volunteer subjects were asked to rest for 20 minutes before commencing the short period of acclimatization and each walk. This 20-minute rest to recuperate before each walking trial was necessary to ensure their lower limb oxygen levels were at baseline resting level along with their arterial pressure immediately prior to walking. This was done following evidence in the literature that indicated that 20 minutes’ rest was more than adequate to facilitate return to baseline values.32 Neither the lower limb O2 levels nor the arterial pressure were measured during the walking trials. The subjects were then invited to commence their walk at their self-selected comfortable walking speed. At the point of sudden onset of claudication pain, subjects were asked to walk immediately around in a circle and walk back along the same corridor to the starting position or until they felt they had to stop. This enabled an estimation of the effect of the three-curve rocker profile on the intensity of claudication pain in comparison with the baseline condition. All subjects were able to walk back to the starting position without pausing or stopping and were asked to sit and rest once they had arrived back at the starting position. It was decided not to formally test patients
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Figure 3. Illustration of curve parameters for the three-curve rocker design used in this study.
to determine their maximum walking distance (MWD) before having to stop, because it was thought that the IC distance (ICD) could be accurately documented and measured using the instant that sudden onset of calf pain occurred. This could not be controlled by the volunteer subject. The MWD was thought to be more subjective by involving input from the volunteer. Using a visual analogue scale (VAS), as shown in Figures 4 and 5, the subjects were asked to give an indication of the intensity of their calf claudication pain experienced while walking back to their original starting position for both test conditions. This was therefore assessed when walking with both the baseline unadapted shoe and the rocker profile condition. By using the sliding mechanism on the scale, they arrived at a position that reflected their pain level during claudication. A reading from the scale on the reverse side of the VAS between 1 and 10 (10 being the worst pain) was recorded. The subjects were unaware of the results and only saw the indicators on the front face of the VAS. None of the subjects reported any discomfort or unsteadiness when wearing the shoes, and no problems with acceptability of the adapted shoes by the volunteers were reported. The precise total distance to claudication was measured using a pedometer/stepometer. (Figure 6: Model - ‘‘MiniMeasure,’’ Trumeter, Leeds, United Kingdom). The distance to the onset of claudication was recorded in meters. The walking trials for both conditions (baseline versus threecurve rocker profile) were randomized and took place during the same clinical session to provide an optimal comparison between the 2 test conditions in preference to inter-day testing.33,34
RESULTS Eight patients undertook the pilot walking trials. Seven patients were male, and 1 was female. Table 2 shows the demographics for the volunteer claudicant group. Primary outcome measures were pain-free walking distance to the onset of calf claudication pain and the severity of pain once claudicating for either test condition. All data were analyzed using SPSS (version 13.0) with a repeated measures analysis of variance. The significance level was
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Figure 4. The VAS mechanism as seen by the volunteer subjects.
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Figure 6. Claudication distance measuring device.
TABLE 2 VOLUNTEER CLAUDICANT DEMOGRAPHICS Parameter
Value
Gender Age Height Mass
7 Male; 1 Female 66 +/ 9.9 years 1.73 +/ 0.1 m 87.7 +/ 17.2 kg
Figure 5. The VAS sliding mechanism showing the numerical scale.
set at P < 0.05 with post-hoc Bonferroni correction used to reduce the chance of type 1 errors.
Claudication distance All claudicants tested (n = 8) demonstrated a significant increase (P = 0.01) in pain-free claudication distance when walking with the three-curve rocker profile adaptation in comparison with baseline. Figure 7 illustrates a comparison of the improvement in the claudication distance achieved when wearing the three-curve rocker test condition. The mean claudication distance increased from 31.59 m to 66.40 m; a mean increase of 34.81 m.
Intensity of claudication pain The intensity of calf pain once claudicating demonstrated a statistically significant reduction (P = 0.00) when walking with the three-curve rocker profile in comparison with baseline (Figure 8). All claudicants registered a reduction in the severity of claudication pain based on the VAS scale. The claudication pain in all cases occurred in the same area of the calf for both test conditions. The mean pain reduction as indicated by the VAS scoring was reduced from a value of 7.75 on a scale of 1 to 10 in severity of pain. Volunteer claudicants indicated a mean reduction of 3.3
from their pain score for the baseline condition while claudicating. The VAS calf pain score while wearing the baseline unadapted shoes was remarkably consistent (mean 7.75, standard deviation (SD) 0.87). The mean VAS calf pain score when walking with the rocker-soled shoes was 4.41 (SD 1.64). The results therefore demonstrated that walking with the three-curve rocker profile condition increased the pain-free walking distance to claudication in all subjects tested (P = 0.008) and substantially decreased the severity of calf pain once claudication had commenced (P = 0.002). A summary table with the mean findings is shown in Table 3.
DISCUSSION This pilot study was designed to gain a first indication of the clinical relevance of adding a rocker sole profile to footwear to potentially reduce the intensity of calf claudication pain and to increase the pain-free ICD. It was also designed to indicate the subject numbers required for a randomized controlled clinical trial. All claudicants demonstrated an increased ICD with the rocker-soled shoe. All of the claudicants who volunteered for the study also regarded the cosmetic appearance of the threecurve rocker acceptable, and none of the subjects reported any feeling of unsteadiness or discomfort during the walking trials. In addition, no subjects reported discomfort in the hips or back
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TABLE 3 SUMMARY OF RESULTS Claudication Distance (m)
Figure 7. Comparison of walking distance for volunteer claudicants during the three-curve rocker-profile test condition in comparison with baseline.
Patient Number
Baseline
Three-Curve Rocker
1 2 3 4 5 6 7 8
30.64 49.68 56.94 14.48 11 101.1 36.03 81.88 47.72 31.59
43.17 58.6 99.71 19.74 23.86 130.28 69.24 86.66 66.4 35.7
Mean Standard Deviation
VAS Claudication Pain Scores
Patient Number
Figure 8. VAS pain score reductions demonstrated during walking trials.
during the walking trials, and no long-term complications are envisioned. Biomechanical analysis of this three-curve rocker profile in a previous study, along with healthy subjects walking in shoes adapted with it under gait laboratory conditions, demonstrated a reduction in the sagittal plane power absorption and power generation required to walk at the ankle and the knee in comparison with an unadapted shoe.24 It was anticipated that such a reduction would translate into increased pain-free walking distance by claudicants. The important finding for this study was that biomechanically modifying claudicant gait via the application of a specific rocker profile resulted in a significantly increased ICD in all the subjects as well as a substantial reduction in the intensity of their pain levels once claudicating. The walking tests utilized a long, straight hospital corridor. Although it is conceded that treadmill testing is currently the most widely used measurement technique for repeated measurement of ICD and MWD, constant-load treadmill walking tests have been shown by some researchers to be more variable than walking tests.35,36 Furthermore, the magnitude and variability of MWD and ICD change with test familiarization and habituation. Level-treadmill tests have been shown to underesti-
1 2 3 4 5 6 7 8 Mean Standard Deviation
VAS Score Baseline
VAS Score Rocker Condition
6.4 8.1 8.4 8.1 8.5 6.6 7.3 8.6 7.75 0.87
5.4 3.3 5.1 3.2 4.5 2.7 3.4 7.7 4.41 1.54
mate the maximum walking distance by over 40% in comparison with active walking on a level surface.37,38 The use of walking along a level surface was therefore thought to be an appropriate alternative means of assessing individual patients for this study, although it is appreciated that treadmills can also simulate uphill walking and are routinely used in clinical practice. Walking on inclined surfaces would theoretically produce calf-pain symptoms earlier than walking on a flat surface, and this needs to be investigated in a future study of participants walking on various slopes under controlled conditions with the 2 test-shoe conditions described in this study. The results nevertheless gave the authors an indication of the number of volunteer subjects required for, and the confidence to
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proceed to, a randomized controlled trial for claudicants walking with a three-curve rocker sole profile added to their footwear during their daily activities. The encouraging finding of significant reduction in the intensity of the calf pain once claudicating indicated that the gastrocnemius muscle may have been offloaded due to the fact that the three-curve rocker sole is designed to facilitate a gentle forward roll of the foot during stance without being too unstable; it is also designed to position the muscle in a more advantageous position during mid- to late-stance phase of gait when in contact with the ground during the propulsion phase. However, this probable unloading effect is yet unproven. A further study is also planned to investigate this phenomenon. No adverse reactions were reported during these walking tests, and none were encountered during a previous study. Therefore, It would be interesting to investigate the alteration in severity of claudication pain and the achievable walking distance achieved by claudicants following a randomized controlled trial while they were walking with the profile over an extended period. Increased habituation may also alter the pain-free walking distance, but the long-term effects of the rocker-soled shoe on gait parameters are yet also unknown. The pain-free ICD was quantified as a primary outcome measure to enable a direct comparison of data relating to the sudden onset of pain. This was an outcome measure that could be accurately quantified and not easily controlled by the volunteer claudicant and therefore not subjective. The MWD was not included as a primary outcome measure in preference to the severity of the pain while claudicating. It is, however, conceded that this parameter is one that is routinely measured.
Limitations of the study The limitations of this study are the limited number of subjects (n = 8) included in the study and therefore the lack of available data produced to perform extensive statistical analysis based on the results, because the data may not have had a normal distribution. It was not therefore possible, for instance, to link severity of disease to potential improvement of symptoms when walking with the rocker-sole profile added to the base of the shoe. Both the patient and the investigators were also unblinded. Another limitation was the decision not to analyze the MWD of the volunteer claudicants. However, all the subjects who volunteered for the study were able to walk without stopping back to the original starting point after experiencing claudication pain.
CONCLUSION This pilot study demonstrated the potential for an adapted shoe to help reduce the intensity of claudication calf pain and to enable claudicants to walk further before experiencing calf pain. Further research is therefore warranted to develop rockersole profiles to be added to footwear to help reduce the symptoms experienced by claudicants and possibly other patient groups, such as those with Achilles tendonitis.
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ACKNOWLEDGMENTS This work was funded by the NHS Executive North West, UK under the R&D Training Fellowship scheme and their assistance in producing this work is gratefully acknowledged. The sponsors were not involved in any aspect of the study.
REFERENCES 1. Bick C. Intermittent Claudication. Nursing Standard 2003; 17(42):45-52. 2. McDermot M, Greenland P. Leg symptoms in peripheral arterial disease: Associated clinical characteristics and functional improvement. JAMA 2001;28:1599-606. 3. Fontaine R, Kim M, Kieny R. ‘‘Die chirugische Behandlung der peripheren Durchblutungsst€ orungen. (Surgical treatment of peripheral circulation disorders)’’ (in German). Helvetica Chirurgica Acta 1954;21(5/6):499-533. 4. Norgren L, Hiatt WR, Dormandy JA. Inter-society consensus for the management of peripheral arterial disease (TASC II). TASC II Guidelines. Eur J Vasc Endovasc Surg 2007;33(1): S1-75. 5. Murray M, Guten G, Sepic S, et al. Function of the triceps surae during gait. Compensatory mechanisms for unilateral loss. J Bone Joint Surg Am 1978;60(4):473-6. 6. Kupecz D. Intermittent claudication treatment. Nurse Pract 2000;25(5):112-5. 7. Fowkes F, Houslee E. The Edinburgh Artery Study; prevalence of asymptomatic and symptomatic peripheral arterial disease in the general population. Int J Epidemiol 1991; 20(2):384-92. 8. Caspary L. Epidemiology of vascular disease. Dis Manag Health Out 1997;2(1):9-17. 9. Leng G, Fowkes F. The Edinburgh Claudication Questionnaire: an improved version of the WHO/Rose questionnaire for use in epidemiological surveys. J. Epidemiol 1992; 45(10):1101-9. 10. Brevetti G, Barletta G. Quality of life in patients with intermittent claudication. Int Angiol 1995;14(1):109. 11. Degischer S, Labs KH, Hochstrasser J, et al. Physical training for intermittent claudication: A comparison of structured rehabilitation versus home-based training. Vasc Med 2002; 7(2):109-15. 12. Learmouth C, Stessor R. Surgery in obliterative arterial disease. Br Med Bull 1952;8:375-8. 13. Nylænde M, Kroese AJ, Morken B, et al. Beneficial effects of 1-year optimal medical treatment with and without additional PTA on inflammatory markers of atherosclerosis in patients with PAD. Results from the Oslo Balloon Angioplasty versus Conservative Treatment (OBACT) study. Vasc Med 2007;12(4):275-83. 14. The MIMIC Trial Participants. The adjuvant benefit of angioplasty in patients with mild to moderate intermittent claudication (MIMIC) managed by supervised exercise, smoking cessation advice and best medical therapy: Results from two randomised trials for stenotic femoropopliteal and aortoiliac arterial disease. Eur J Vasc Endovasc Surg 2008; 36(6):680-8.
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15. Mazari FAK, Gulati S, Rahman MNA, et al. Early outcomes from a randomized, controlled trial of supervised exercise, angioplasty, and combined therapy in intermittent claudication. Ann Vasc Surg 2010;24(1):69-79. 16. Dean SM. Pharmacologic treatment for intermittent claudication. Vasc Med 2002;7:301-9. 17. Kruidenier LM, Nicola€ı SPA, ten Bosch JA, et al. Predictors of walking distance after supervised exercise therapy in patients with intermittent claudication. Eur J Vasc Endovasc Surg 2009;38(4):449-55. 18. Chavatzas D, Jaimieson C. The doubtful place of the raised heel in patients with intermittent claudication of the leg. Br J Surg 1974;61:299-300. 19. Richardson J. Rocker-soled shoes and walking distance in patients with calf claudication. Arch Phys Med Rehab 1991;72:554-8. 20. Romkes J, Rudmann C, Brunner R. Changes in gait and EMG when walking with the Masai Barefoot Technique. Clin Biomech 2006;21(1):75-81. 21. Nigg B, Hintzen S, Ferber R. Effect of an unstable shoe construction on lower extremity gait characteristics. Clin Biomech 2006;21(1):82-8. 22. Burns J, Wegener C, Begg L, et al. Randomized trial of custom orthoses and footwear on foot pain and plantar pressure in diabetic peripheral arterial disease. Diabet Med 2009; 26(9):893-9. 23. Hutchins S, Bowker P, Geary N, Richards J. The biomechanics and clinical efficacy of footwear adapted with rocker profiles - evidence in the literature. Foot 2009; 19(3):165-70. 24. Hutchins SW. The effects of rocker sole profiles on gait: implications for claudicants. Stephen William Hutchins, PhD Thesis, Healthcare Professions University of Salford (2007). Source Record Number: 921830, Source: SAL LMS DS. 25. Narici MV, Binzoni T, Hiltbrand E, et al. In vivo human gastrocnemius architecture with changing joint angle at rest and during graded isometric contraction. J Physiol 1996;496(1): 287-97. 26. Sheehan FT. In vivo quantification of the Achilles tendon moment arm. Foot Ankle Res 2008;1(1):2. 27. Maganaris CN, Baltzopoulus V, Sargeant A. Changes in Achilles tendon moment arm from rest to maximum isomet-
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APPENDIX A. PATIENT INFORMATION SHEET 1. Project Title The use of rocker (clog-shaped) soles to shoes in the treatment of patients with pain in the lower limb when walking (those with intermittent claudication).
2. You are being invited to take part in a research study. Before you decide it is important for you to understand why the research is being done and what it will involve. Please take time to read the following information carefully and discuss it with fiends, relatives and your GP if you wish. Ask us if there is anything that is not clear or if you would like more information. Please take time to decide whether or
not you wish to take part. Consumers for ethics in research (CERES) publish a leaflet entitled ‘‘Medical Research and you.’’ This leaflet gives more information about medical research and looks at some questions you may want to ask. A copy may be obtained from: CERES, PO Box 1365, London, N16 0BW. Thank you for reading this. 3. The Purpose of the Study. The purpose of the study is to try to find out if the addition of a rocker sole (which looks like a clogg-shape) to patients who experience leg pain can help them walk better and potentially further. Patients who get a pain in the calf when they have walked a certain distance may well benefit from this alteration to their shoes.
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4. Why have you been asked? You have been chosen for the project because you suffer from leg pain on walking due to intermittent claudication, and have got to a stage where the distance you can walk without pain in the leg does not vary much. It is hoped to test at least 50 patients. 5. Do you have to take part? It is up to you to decide whether or not to take part. If you decide to take part, you will be given this patient information sheet to keep, and be asked to sign a consent form. If you decide to take part you are still free to withdraw at any time and without giving a reason. This will not affect the standard of care you receive. 6. What will happen to you if you take part? The study will last for three years but your help in the project will only be required over a three-month period which will entail a number of visits to Arrowe Park Hospital and possibly the gait laboratory in The University of Salford. The visit to the gait laboratory will only be offered to a small number of patients. You will only be involved over four separate days within a three-month period at Arrowe Park Hospital. Depending on whether or not you are selected and agree to travel to Salford there may be an additional day involved. During these four or five days you will be involved in the following activities: Visit 1: Arrowe Park Hospital During the first day you will initially be assessed as being suitable for the project. We will need to watch you walking to make sure that you do not have a limp due to conditions other than intermittent claudication, and that your overall condition will allow you to walk certain distances (between 15 and 400 yards) to the onset of pain due to intermittent claudication in your lower leg. We will do this at Arrowe Park Hospital. You will then be measured for a pair of made-tomeasure shoes, which you may keep after the testing. There will be no charge for the shoes. The shoes will be used to allow us to conveniently add the rocker-sole shape to the footwear. The rocker sole will be removed afterwards at the end of the final testing period if you wish. Visit 2: Arrowe Park Hospital On this visit, you will be supplied with the specially made shoes and asked to walk a short distance to make sure they are comfortable. On this visit, we will also ask you to walk along a long flat corridor to measure the distance you can walk until the onset of pain in your lower leg whilst wearing the made to measure shoes. After a short period of rest we will ask you to walk along the same corridor wearing the same pair of shoes, but with the rocker shape added. We hope this will allow you to walk a lot further before experiencing the calf pain. The study method will be to simply see if the addition of the rocker sole helps you walk further before the onset of pain in your leg than without it added on the same pair of shoes.
7. What do you have to do? There are no lifestyle or dietary restrictions. You can do all your normal activities such as
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driving or taking part in sport. If you are on regular medication we would wish you to continue taking it. What is the procedure that is being tested? The rocker sole is a profiled shape added to the bottom of the sole of a shoe. It is designed to reduce the work done by the calf muscles when walking. It encourages the foot to roll forwards instead of using the calf muscles so much, and as such theoretically reduces the work done by the calf muscles in walking a set distance. We are hoping to test the theory that rocker soles help patients with pain in the lower limb to walk further before the onset of pain because the calf muscles should not have to work so hard. What are the alternatives for diagnosis or treatment? You will already have been diagnosed as having intermittent claudication to be included in the study. Alternative forms of treatment apart from using rocker soles include exercise regimes, drug therapy and in some cases, surgery. What are the side effects of taking part? There should be no side effects of taking part. Indeed, we hope to prove that the addition of rocker soles will be of benefit to you. However, we will not insist that you continue wearing the rocker-soled shoes should they prove to be beneficial. We will remove the rocker soled shape from the bottom of the shoes for you should you wish us to do so, and you may keep the shoes once the testing has been completed. There will be no charge for the shoes or alterations done to them. What are the possible disadvantages of taking part? There should be no disadvantages of taking part. What are the possible benefits of taking part? We hope that the treatment will help you. However, this can not be guaranteed. The information we get from this study may help us to treat future patients with intermittent claudication more effectively. What if new information becomes available? Sometimes, during the course of a research project, new information becomes available about the treatment that is being studied. If this happens, your research fellow will tell you about it and discuss with you whether you want to continue in the study. If you decide to withdraw your research fellow will make arrangements for your care to continue. If you decide to continue in the study you will be asked to sign an updated consent form.
Also, on receiving new information your research fellow might consider it to be in your best interests to withdraw you from the study. He/she will explain the reasons and arrange for your care to continue.
14. What happens when the research study stops? The treatment should be available on the NHS if you decide to continue with the addition of rocker soles to your shoes. It is unlikely however that they will pay for an additional pair of made-to-measure shoes unless you have a foot problem. They will, however, be able to add rocker soles onto a suitable pair of your own shoes free of charge.
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15. What if something goes wrong? Complaints as to your treatment by members of staff in the NHS or University of Salford will be handled by an independent person who will investigate the facts. If you are harmed by taking part in this research project, there are no special compensation arrangements. If you are harmed due to someone’s negligence, then you may have grounds for a legal action but you may have to pay for it. Regardless of this, if you wish to complain about any aspect of the way you have been approached or treated during the course of this study, the normal National Health Service complaints mechanisms may be available to you. 16. Will my taking part in this study be kept confidential? All information, which will be collected about you during the course of the research, will be kept strictly confidential. Any information about you which leaves the hospital/ university will have your name and address removed so that you cannot be recognised from it. Your GP will be notified of your participation in the trial, along with any medical practitioners not involved in the research who may be treating you. Do you agree to this? Yes/No 17. What will happen to the results of the research study? The results will be published in a research paper and will be used to write a PhD Thesis. The results are likely to be published at the end of the four-year period i.e. June 2003. You will be informed where and when the results
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are published. (You will not be identified in any publication/thesis). 18. Who is organising and funding the research? The research is being funded by N.H.S. Executive North West Research and Development Directorate. The funding body will pay for the salary replacement costs of the Research Fellow for an equivalent of two days per week for the duration of the study. The research Fellow will be organising the study and will involve colleagues at the University of Salford and other departments such as the Appliance Office and Orthopaedic and Surgical Directorate at Arrowe Park Hospital. 19. Who has reviewed the study? The study has been reviewed by the N.H.S. Executive North West Research and Development Directorate, and has been sent for peer review by two independent experts. The Wirral Health Authority Research Ethics Committee and The University of Salford Ethics Committee have also reviewed the study. Please contact Stephen Hutchins at The University of Salford: telephone number 0161 295 2320 or Mrs Lord, Appliance Officer, Arrowe Park Hospital on 0151 604 7092. Thank you for taking part in the study. April 2000 No. 1 You will be given a copy of the information sheet and a signed consent form to keep.