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Correlations between subjective treatment responses and plantar pressure parameters of metatarsal pad treatment in metatarsalgia patients: a prospective study.
Kang JH, Chen MD, Chen SC, Hsi WL. BMC Musculoskelet Disord. 2006 Dec 5;7:95.
Quote:
BACKGROUND: Metatarsalgia is related to repetitive high-pressure loading under the metatarsal head (MH) that causes pain. The high pressure under the MH can be reduced by adequately applying metatarsal pads (MPs). Plantar pressure measurements may provide a method to objectively evaluate pressure loading under the MH. However, it is still unclear if the decrease in plantar pressure under the MH after MP treatment is associated with subjective improvement. This study aims to explore the correlations between subjective pain improvement and outcome rating, and the plantar pressure parameters in metatarsalgia patients treated using MPs.
METHODS: Thirteen patients (a total of 18 feet) with secondary metatarsalgia were included in this study. Teardrop-shaped MPs made of polyurethane foam were applied just proximal to the second MH by an experienced physiatrist. Insole plantar pressure was measured under the second MH before and after MP application. Visual analog scale (VAS) scores of pain were obtained from all subjects before and after 2 weeks of MP treatment. The subjects rated using four-point subjective outcome scales. The Wilcoxon signed-rank test was used to analyze the difference between the plantar pressure parameters and VAS scores before and after treatment. The Kruskal-Wallis test was applied to compare the plantar pressure parameters in each outcome group. Pearson's correlation was applied to analyze the correlation between the changes in plantar pressure parameters and VAS scores. Statistical significance was set as p < 0.05.
RESULTS: MP application decreased the maximal peak pressure (MPP) and pressure-time integral (PTI) under the second MH and also statistically improved subjective pain scores. However, neither the pre-treatment values of the MPP and PTI shift in the position of the MPP after treatment, nor the age, gender and body mass index (BMI) of the subjects were statistically correlated with subjective improvement. Declines in the PTI and MPP values after MP application were statistically correlated with the improvement in VAS scores (r = 0.77, R2 = 0.59, p < 0.001; r = 0.60, R2 = 0.36, p = 0.009).
CONCLUSION: We found that the successful decline in the PTI and MPP under the second MH after MP application was correlated to subjective pain improvement. This study provides a strategy for the further design and application of MPs for metatarsalgia treatment.
Correlations between subjective treatment responses and plantar pressure parameters of metatarsal pad treatment in metatarsalgia patients: a prospective study.
Kang JH, Chen MD, Chen SC, Hsi WL. BMC Musculoskelet Disord. 2006 Dec 5;7:95.
Excellent study. Should have been done 10-15 years ago by the podiatry profession, however. Oh well, at least somebody finally gave us some evidence of how metatarsal pads work.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Still a very small study to draw too many conclusions from, despite overwhelming anidotal evidence to support it. Similar work was published in the Chiropodist (UK) in the early 80s. Work conducted by Ken Robertson (if memory serves) with preliminary work on the pedobaragraph He compared position of met pads and peak pressure and found the positon of the metatarsal pad on the foot had significant little bearing on the peak pressures recorded. All appeared to reduce peak pressures but no attempt was made to record pain as his subjects were all normals. Over the last two decades there has been work done by physical therapists and physiotherapists relating to metatarsal pads and their effects. Some studies were pretty dubious but others rather interesting with one examining the effects of water content in callus.
It would seem prudent to accept pressure alone would not account for metatarsalgia but likely to contribute as a variable.
Along this topic...I've often wondered about the effects of mortons neuroma pads. I was taught in school to place the apex of this small dome pad (they are smaller than metatarsal pads) between the metatarsal necks of the affected interspace- with the hope of spreading the metatarsals having a reverse Mulders effect. I doubt this happens, and any positive effect is probably from the mechanisms discussed in this paper. Any thoughts??? Is it widely believed that a neuroma pad is designed to separate metatarsals???
Along this topic...I've often wondered about the effects of mortons neuroma pads. I was taught in school to place the apex of this small dome pad (they are smaller than metatarsal pads) between the metatarsal necks of the affected interspace- with the hope of spreading the metatarsals having a reverse Mulders effect. I doubt this happens, and any positive effect is probably from the mechanisms discussed in this paper. Any thoughts??? Is it widely believed that a neuroma pad is designed to separate metatarsals???
Nick
It seems reasonable to assume that a metatarsal pad or "neuroma pad" if placed correctly may tend to cause a small separation of the metatarsals that may, in turn, cause a reduction in compression force on the neuroma. However, I tell my patients that this will only work if their shoes are loose enough in the forefoot to allow the metatarsals to spread apart. I use small metatarsal pads routinely in patients with neuromas, mostly with good success, and I place them so that their apex is at the level of the metatarsal neck, +/- a few mm distal or proximal depending on perceived patient comfort. I feel the metatarsal pads work much better if placed on or within a custom foot orthosis for treatment of neuromas.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
As I understand the etiology of neuroma, there appears to be compression and stretching of the nerve fibres which are cited as co-requisites. The idea metatarsal heads rubbing together is unlikely and physically separating them with soft padding on the sole of the foot, improbable. But I do share Kevin's experience with the benefit of stratigically placed pads. I always thought the critical increased bulk over the lateral aspect of the fourth met shaft may in some way reduce peak pressure as the foot goes into propulsion. This may 'rest the nerve', and break the pain cycle. I have also used silicone props to similar effect.
As I understand the etiology of neuroma, there appears to be compression and stretching of the nerve fibres which are cited as co-requisites. The idea metatarsal heads rubbing together is unlikely and physically separating them with soft padding on the sole of the foot, improbable. But I do share Kevin's experience with the benefit of stratigically placed pads. I always thought the critical increased bulk over the lateral aspect of the fourth met shaft may in some way reduce peak pressure as the foot goes into propulsion. This may 'rest the nerve', and break the pain cycle. I have also used silicone props to similar effect.
Cameron
This is quite an interesting concept and one that I have not given much recent thought to. Mechanical modelling of the effects of the metatarsal pad would show, as in the study listed above, that GRF for the forefoot has not only been shifted more posteriorly towards the distal 3rd and 4th metatarsal shafts but also has been redirected away from the 3rd and 4th metatarsal heads. Another critical part of this modelling would be that the more narrow shape of the metatarsal necks versus the metatarsal heads would cause the intermetatarsal distance to be much greater at the metatarsal neck level than at the metatarsal head level.
Now, if a fairly pinpoint GRF (e.g. from a metatarsal pad) focuses a substantial plantar force more between the metatarsal necks rather than directly plantar to the metatarsal heads, there would be an increase in 4th metatarsal abduction moment (relative to the 3rd metatarsal) especially at late midstance and early propulsion. This increased magnitude of 4th ray abduction moment would tend to increase the distance between the 3rd and 4th metatarsals and would also probably significantly reduce the magnitude of pressure on the intermetatarsal nerve during late midstance and early propulsion.
The mechanism here is similar to the mechanism that occurs when a splitting wedge/maul is swung onto the end of a round of wood Macho Man Splitting Wood. A relatively concentrated, pinpoint force between the grain of the piece of wood will easily split most wood rounds. A given kinetic energy, E, applied with a correctly shaped splitting maul into the wood grain on the round would result in the round being easily split. However, the same applied energy, E, from a blunt sledge-hammer, would distribute the weight to compress the multiple grains of wood on end which would only compress the wood face and would cause a dent to be formed in the end of the round from the impact.
It seems quite likely that a metatarsal pad not only significantly increases the 4th ray abduction moment relative to the 3rd metatarsal and significantly decreases the pressure on the intermetatarsal nerve, but also slightly separates the metatarsal necks due to increased 4th ray abduction moment that causes increased tensile force on the deep transverse ligament (and other intermetatarsal soft tissue structures). This "splitting wedge" effect would be most prominent during late midstance and early propulsion when the GRF plantar to the forefoot is of the greatest magnitude.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
I would concur the most likely explanation does involve change in direction of GRFs but could be less sceptical if a rigid shaft was used (as in shoe modification). I am amazed all the more because of the very low resistance to compression within foams and felt and that these would offer sufficient lever to change in direction of GRFs. If indeed this is so then it may be even a short experience (matter of hours) can have long term effects.
Dear All,
I have issue with the very low density of MP's used by many pods - there is no mention of the density of the polyurethane pads used in the afore-quoted study.
I have had some success with 'hapad' products as they can be half adhered and moved to ensure the most accurate placement after trial.
Has any attention been paid to MP densities?
Regards PR
To the best of my knowledge MP are usually made of standard (medium) density foams /polyurethans or semi compressed, as in felts. Orthotists will often dent the foot plate of BKFO to give the equivolent effect of a hard density MP. I am not aware of any evaluations to review the efficacy of the traditional modification.
[quote=Kevin Kirby]and I place them so that their apex is at the level of the metatarsal neck, +/- a few mm distal or proximal depending on perceived patient comfort. [quote]
I often find 'placement' to be a very tricky operation. Whilst it is easy to place a pad directly onto the foot with adhesive tape, it becomes a lot loss predicatable when the foot has to position itself on top of the pad, attached to an orthosis, within a shoe...
Consequently, I often allow myself to be directed by patients as to where the pad should be placed on the the orthosis - more often than not, the area of greatest comfort corresponds to almost exactly *under* the neuroma (ie distal to the MTP joints).
Whenever I place the pad back at the metatatsal neck, they will frequently complain that is is too proximal and of limited benefit...
Consequently, I often allow myself to be directed by patients as to where the pad should be placed on the the orthosis - more often than not, the area of greatest comfort corresponds to almost exactly *under* the neuroma (ie distal to the MTP joints).
Whenever I place the pad back at the metatatsal neck, they will frequently complain that is is too proximal and of limited benefit...
Anyone else with this experience?
Not long ago I was experiencing intermetatarsal pain between 3-4 on my left foot. I found the greatest relief when walking would be to flex my toes - as if trying to grab something with my foot. I also found that in stance, a met pad would provide most relief when placed directly under the metatarsal heads. HOWEVER, this would be most uncomfortable during the propulsive phase of walking.
I also found that by placing a met pad too far proximally, it would irritate the tight plantar fascia, resulting in aching pain as well as the sharp intermetatarsal pain.
I often find 'placement' to be a very tricky operation. Whilst it is easy to place a pad directly onto the foot with adhesive tape, it becomes a lot loss predicatable when the foot has to position itself on top of the pad, attached to an orthosis, within a shoe...
Consequently, I often allow myself to be directed by patients as to where the pad should be placed on the the orthosis - more often than not, the area of greatest comfort corresponds to almost exactly *under* the neuroma (ie distal to the MTP joints).
Whenever I place the pad back at the metatatsal neck, they will frequently complain that is is too proximal and of limited benefit...
Anyone else with this experience?
LL
LL:
I use the same process as you do and have made the same observations regarding patient comfort. For placement of metatarsal pads on foot orthoses, I generally have the lab add the metatarsal pad to the device so that metatarsal pad protrudes 15 mm distal to the anterior edge of the orthosis. Over the years this has worked out very well for my patients as a good standard location of metatarsal pad placement on their orthoses.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
As far as I've observed, there is no uniformity amongst the pod community regarding the types of pads used (or, for that matter Cameron, amongst orthotists using them via cast modifications, since I've never done them that way and many of my colleagues are the same) as it usually depends on whether the individual pod is actually manufacturing the orthoses themselves and if so, where they buy their pads.
I have noticed frequent differences in placement position however, with a great many pods locating the apex beneath the MTPJs as they would do for a felt PMP that's adhered to the foot, rather than more proximally to load the shafts and decrease pressure on the met heads.
LL, just reading your post, I find the best area of placement to be when the apex is immediately proximal to the heads. I usually warn patients that this will feel too far back initially, but anything more distal will actually increase pressure beneath the MTPJs as the foot heads towards toe off, not doing the neuroma any favours. If it's blended into the device adequately at the posterior section, it shouldn't cause too much irritation to the plantar fascia slips
For what it's worth i usually place mine with the leading edge across the middle of the met heads (ie under half the wb area). I tend to find this works better with soft pads than having them more proximal. I also find they work much better on a casted device than on their own.
Robert, it sounds like we're doing the same thing. I think the main difference is whether the devices are made from a cast or a direct mould, such as one of those rubber footboards.
Effect of metatarsal pad placement on plantar pressure in people with diabetes mellitus and peripheral neuropathy.
Hastings MK, Mueller MJ, Pilgram TK, Lott DJ, Commean PK, Johnson JE. Foot Ankle Int. 2007 Jan;28(1):84-8
Quote:
BACKGROUND: Standard prevention and treatment strategies to decrease peak plantar pressure include a total contact insert with a metatarsal pad, but no clear guidelines exist to determine optimal placement of the pad with respect to the metatarsal head. The purpose of this study was to determine the effect of metatarsal pad location on peak plantar pressure in subjects with diabetes mellitus and peripheral neuropathy.
METHODS: Twenty subjects with diabetes mellitus, peripheral neuropathy, and a history of forefoot plantar ulcers were studied (12 men and eight women, mean age=57+/-9 years). CT determined the position of the metatarsal pad relative to metatarsal head and peak plantar pressures were measured on subjects in three footwear conditions: extra-depth shoes and a 1) total contact insert, 2) total contact insert and a proximal metatarsal pad, and 3) total contact insert and a distal metatarsal pad. The change in peak plantar pressure between shoe conditions was plotted and compared to metatarsal pad position relative to the second metatarsal head.
RESULTS: Compared to the total contact insert, all metatarsal pad placements between 6.1 mm to 10.6 mm proximal to the metatarsal head line resulted in a pressure reduction (average reduction=32+/-16%). Metatarsal pad placements between 1.8 mm distal and 6.1 mm proximal and between 10.6 mm proximal and 16.8 mm proximal to the metatarsal head line resulted in variable peak plantar pressure reduction (average reduction=16+/-21%). Peak plantar pressure increased when the metatarsal pad was located more than 1.8 mm distal to the metatarsal head line.
CONCLUSIONS: Consistent peak plantar pressure reduction occurred when the metatarsal pad in this study was located between 6 to 11 mm proximal to the metatarsal head line. Pressure reduction lessened as the metatarsal pad moved outside of this range and actually increased if the pad was located too distal of this range. Computational models are needed to help predict optimal location of metatarsal pad with a variety of sizes, shapes, and material properties.
The influence of metatarsal support height and longitudinal axis position on plantar foot loading
Thor-Henrik Brodtkor, Géza F. Kogler, Anton Arndt Clinical Biomechanics (Articles in Press)
Quote:
Background:
Metatarsal supports are effective at decreasing plantar foot pressures at the metatarsal heads, however, little is known about the dependence of this decrease upon height and position.
Methods:
Barefoot static stance pressure measurements were recorded during standing in single limb support (n=22). Two metatarsal support heights (5mm, 10mm) were evaluated in six positions at 5mm increments (0, 5, 10, 15, 20, 25mm) proximal to the metatarsal heads along the longitudinal axis of the foot. The barefoot condition with no metatarsal support served as the control. Mean force was measured for each test condition. The findings of this study are limited to the barefoot (unshod) condition.
Findings:
Mean plantar force decreased significantly under the second metatarsal head with both 5 and 10mm metatarsal supports compared to the control, and 10mm metatarsal support compared with 5mm metatarsal support (P<0.05) while no statistically significant differences were noted relative to longitudinal axis position.
Interpretation:
The results of this study suggest that the thickness of a metatarsal support is a determinant factor in regulating plantar loading. Surprisingly, the longitudinal axis location of a metatarsal support does not appear to be as important as clinically presumed since the data showed that the force decrease was similar for all positions from 5 to 25mm. Thus, the orthotic induced effect of a metatarsal support seems to have a sizable interaction range that has not previously been reported. We speculate that the metatarsal support’s fulcrum and lift effect can be sustained at a more proximal position due to the foot’s rigidity as a lever and the manner in which a metatarsal support interacts with the plantar aponeurosis.
I use the same process as you do and have made the same observations regarding patient comfort. For placement of metatarsal pads on foot orthoses, I generally have the lab add the metatarsal pad to the device so that metatarsal pad protrudes 15 mm distal to the anterior edge of the orthosis. Over the years this has worked out very well for my patients as a good standard location of metatarsal pad placement on their orthoses.
Wow, my lab doesn't place them even close to this. I appreciate your insight and sharing this. I will have to give this a try.
Does anyone find there are times when they have more success with a metatarsal bar?
Effect of a Metatarsal Pad on the Forefoot During Gait
Koen L. M. Koenraadt, Niki M. Stolwijk, Dorine van den Wildenberg, Jaak Duysens, Noël L. W. Keijsers
JAPMA January/February 2012 vol. 102 no. 1 18-24
Quote:
Background: Metatarsal pads are frequently prescribed for patients with metatarsalgia to reduce pain under the distal metatarsal heads. Several studies showed reduced pain and reduced plantar pressure just distal to the metatarsal pad. However, only part of the pain reduction could be explained by the decrease in plantar pressure under the forefoot. Therefore, an alternative hypothesis is proposed that pain relief is related to a widening of the foot and the creation of extra space between the metatarsal heads. This study focused on the effect of a metatarsal pad on the geometry of the forefoot by studying forefoot width and the height of the second metatarsal head.
Methods: Using a motion analysis system, 16 primary metatarsalgia feet and 12 control feet were measured when walking with and without a metatarsal pad.
Results: A significant mean increase of 0.60 mm in forefoot width during the stance phase was found when a metatarsal pad was worn. During midstance, the mean increase in forefoot width was 0.74 mm. In addition, walking with a metatarsal pad revealed an increase in the height of the second metatarsal head (mean, 0.62 mm). No differences were found between patients and controls.
Conclusions: The combination of increased forefoot width and the height of the second metatarsal head produced by the metatarsal pad results in an increase in space between the metatarsal heads. This extra space could play a role in pain reduction produced by a metatarsal pad
Metatarsal pads and metatarsalgia
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