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Metatarsal bars more effective than metatarsal pads in reducing impulse on the second metatarsal head
The Foot 21 (2011) 172–175
Contents lists available at ScienceDirect
The Foot journal homepage: www.elsevier.com/locate/foot
Metatarsal bars more effective than metatarsal pads in reducing impulse on the second metatarsal head Annie Deshaies a , Patrice Roy b , Panagiotis D. Symeonidis c,∗ , Bernard LaRue a , Norman Murphy d , Éric Anctil a a
University of Sherbrooke Hospitals, Orthopaedic Service, CHUS-Hôtel Dieu, 580, rue Bowen sud, Sherbrooke, Québec J1G 2E8, Canada Clinique Podiatrique de l’Estrie, 1135 Boul Jacques-Cartier, Sherbrooke, Québec J1J 3A8, Canada c E.Amynis 18, 54621 Thessaloniki, Greece d Tekscan, 4710 des Chanterelles, Rock-Forest, Québec J1N 4J6, Canada b
a r t i c l e
i n f o
Article history: Received 9 February 2011 Received in revised form 20 April 2011 Accepted 8 May 2011 Keywords: Metatarsalgia Impulse Pads Bars
a b s t r a c t Background: The second metatarsal head is commonly involved in cases of metatarsalgia. As part of the conservative treatment, metatarsal bars and metatarsal pads are often prescribed. Objective: To compare the effectiveness of metatarsal bars and metatarsal pads in reducing impulse on the second metatarsal head. Method: Thirty-five healthy subjects were monitored with an insole scanning system during walking in four different conditions: (a) wearing shoes only, (b) shoes plus metatarsal pads and shoes plus metatarsal bars, placed either (c) perpendicular to the foot axis or (d) oblique to the foot axis. The impulse under the second metatarsal head was measured using the first condition as a control. Both feet were examined in each subject resulting in a total of 840 measurements. Results: Both metatarsal bars and metatarsal pads were effective in reducing impulse when compared with the control (P < 0.01). Metatarsal bars were found to be more effective in reducing impulse as compared to the metatarsal pads (P < 0.01), and the oblique position of the bars was more effective than the perpendicular one (P < 0.01). Conclusions: The greatest reduction of impulse on the second metatarsal head in healthy subjects is achieved with the use of metatarsal bars in an oblique position. © 2011 Elsevier Ltd. All rights reserved.
1. Introduction Metatarsalgia is defined as pain in the region of the distal aspect of one or more of the metatarsals during weightbearing [1]. It is one of the commonest foot symptoms encountered in orthopaedic and podiatric practices and can result either from physiologic loading on pathological structures or by excessive loading on normal structures. The second metatarsal head is commonly affected by metatarsalgia [2]. This may occur primarily by a relatively longer second metatarsal, which results in increased pressure and friction during the propulsive phase of gait. Secondary metatarsalgia is caused by various metabolic, neurologic and traumatic conditions, which alter the mechanical load of the forefoot. Forefoot surgery on the first or second ray, which alters the relative metatarsal length, can also result in metatarsalgia over the second metatarsal head.
∗ Corresponding author. Tel.: +30 2310 258100; fax: +30 2310 258101. E-mail address: [email protected] (P.D. Symeonidis). 0958-2592/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foot.2011.05.001
Finally, Freiberg’s infraction has a marked predilection for the second metatarsal head [3]. The conservative treatment of metatarsalgia frequently includes the use of metatarsal pads and metatarsal bars. These orthotics and shoe modifications act by reducing the pressure on metatarsal heads which is related to pain relief, although the evidence regarding their effectiveness remains meager and conflicting [4,5]. Proper use of the orthotics can result in up to 60% of pressure reduction [6]. Metatarsal pads are insole devices with the advantage of high patients’ compliance. On the other hand, metatarsal bars are shoe modifications placed on the outside sole and are therefore more cumbersome and not always well tolerated by patients. Despite the widespread use of orthotics in the treatment of metatarsalgia current literature lacks sufficient evidence regarding the superiority of one over the other [5,7,8]. We compared the efficacy of metatarsal pads to external metatarsal bars in reducing impulse on the second metatarsal head in normal subjects. We also studied different positions of the bar and their effect on impulse reduction.
A. Deshaies et al. / The Foot 21 (2011) 172–175
173
2. Patients and methods Thirty-five healthy subjects aged from 15 to 65 years (mean age = 38 years) with asymptomatic feet volunteered for the study. There were 15 men and 20 women. Exclusion criteria for participation were any condition which could affect the subject’s gait or posture such as history of previous trauma or surgery of the foot and ankle, congenital or acquired foot deformities, lower limb malalignment, use of walking aids and any systemic disease that can affect walking. Both feet were evaluated for each subject. Each volunteer was asked to walk at his own walking speed and rhythm on a straight path for ten meters under four different conditions: (a) walking with shoes only, (b) walking with shoes and metatarsal pads (Fig. 1), (c) walking with shoes reinforced with metatarsal bars placed perpendicularly to the foot axis (Fig. 2a) and (d) Walking with shoes reinforced with metatarsal bars placed obliquely to the foot axis, along a line subtended by the heads of the first and the fifth metatarsal (Fig. 2b). In order to avoid the effect of abnormal patterns on the initiation of walking and stopping, only steps 2–7 from each condition were retained for analysis. Therefore, data for three right foot and three left footsteps was analyzed for each person resulting in six steps for each condition and a total of 24 measurements per person. This resulted in 840 measurements for the whole study group. Metatarsal pads and bars were adjusted to the subjects’ own running shoes by a trained podiatrist (PR). The shoes used by the volunteers were commercial soft sole shoes with laces. The metatarsal pads were prefabricated (model P407, JMS Plastics Supply Inc, Neptune, NJ) and made of Poron® , a microcellular urethane foam. They were 8 mm thick at the apex and had a longitudinal axis Fig. 2. Different positions of the metatarsal bars: perpendicular to the foot axis in the right shoe and obliquely in the left shoe.
Fig. 1. Metatarsal pads placed on the inside soles.
of 5.2 cm and a transverse axis of 4.5 cm. An adhesive flat backing permitted stable placement on each subject’s inner sole. The bars (model P406, JMS Plastics Supply Inc, Neptune, NJ) were made of a high-density rubber material (black neuron) and had the shape of a half-cylinder with a radius of 10 mm. Impulse (force-time integral in kg s) represents the load of a certain area in relation to the time the area is loaded. In the current study, impulses were recorded with the use of the F-scan bipedal inshoe analysis Mobile System (Tekscan, Boston, Massachusetts) in each of the four walking conditions. This device utilizes paper-thin sensors (F-Scan 3000) inserted inside the shoes and permits precise impulse measurement. There are four sensors per cm2 . Transfer units are placed around the ankle and linked to a battery belt pack permitting free ambulation. The sensors were calibrated and tailored to fit each subject’s shoes appropriately. According to the products guidelines, the sensors can be used 10–15 times before disposal. For the purposes of the current study, each sensor was used five times only. Data were analyzed using Research Foot Software Version 5.72. The program produces a graph using different colors for each step to indicate different impulse levels. The area underneath the second metatarsal head was outlined on each graph by one author (AD) who was blinded for the type of intervention. For each of the selected areas, the resulting impulse was calculated by the computer software. Each impulse represents the amount of loading pressure for the period of time during which it is applied, namely the duration of each step. The mean impulse of each foot was calculated in all four conditions. Therefore, for each of the 35 volunteers four left-foot and
174
A. Deshaies et al. / The Foot 21 (2011) 172–175
four right-foot mean impulses were calculated which resulted in a total of 280 mean impulses. A mixed model was used to account for the repeated measurements. In more detail, the following terms were considered in this multilevel model: condition, side, gender, condition × side, condition × gender, side × gender. Also the three-way interaction term condition × side × gender was considered but it was not significant, therefore the multilevel model with the two-term interactions was fitted. The mean and the corresponding 95% confidence intervals were presented. The pairwise comparisons between conditions were tested with paired Student’s t-tests and the Bonferroniadjusted P-values were reported. All analyses were conducted using SPSS 17 (SPSS, Inc., Chicago, IL). All reported P-values were two-tailed with P < 0.05 considered as significant.
Condition
Gender
Mean
95% confidence interval Lower limit
Upper limit
Shoes
Male Female
3.714 3.456
3.059 2.889
4.369 4.023
Met pads
Male Female
2.943 2.650
2.293 2.088
3.592 3.213
Straight bar
Male Female
1.979 2.181
1.324 1.614
2.633 2.747
Oblique bar
Male Female
1.701 1.832
1.053 1.271
2.350 2.394
Table 3 Mean impulses (kg s) and corresponding confidence intervals, showing the significant interaction between side and gender.
3. Results The mean impulses for both feet were reduced with the use of both metatarsal bars and metatarsal pads (Table 1) Men had higher impulses than women, the differences not being significant (Table 1; P = 0.898). Left feet impulses were significantly higher than the right side (P < 0.001). There was a significant difference in impulses among the four conditions (condition P < 0.001) showing that the impulses were significantly higher with the shoes only condition compared to the other three conditions (Bonferroni-adjusted P-value, P < 0.001 for all three comparisons). Moreover, the impulses were higher with the metatarsal pads compared to the straight and oblique bars (Bonferroni-adjusted P-value, P < 0.001 for both comparisons). Last, the oblique position of the bars was significantly more effective than the straight one (Bonferroni-adjusted Pvalue, P < 0.001). There was a significant interaction between gender and condition (P < 0.001) showing that the impulses were higher in men than in women in the shoes only condition and the pads, while they were higher in women than in men in the other two conditions with the bars (Table 2). Furthermore, there was a significant interaction between gender and side (P < 0.001), showing that the impulses were higher in men for the right side while they were higher in women for the left side (Table 3).
Table 1 Mean impulses (kg s) and corresponding confidence intervals. Gender
Side
Condition
Mean*
Lower limit
Upper limit
Male
Right
Shoes Met pads Straight bar Oblique bar Shoes Met pads Straight bar Oblique bar
3.513 2.819 1.786 1.469 3.916 3.066 2.171 1.933
2.855 2.167 1.122 .817 3.252 2.412 1.515 1.281
4.171 3.472 2.450 2.122 4.580 3.721 2.827 2.585
Shoes Met pads Straight bar Oblique bar Shoes Met pads Straight bar Oblique bar
3.072 2.344 1.805 1.418 3.840 2.957 2.556 2.247
2.502 1.779 1.228 .853 3.264 2.389 1.987 1.682
3.642 2.909 2.382 1.983 4.417 3.524 3.125 2.812
Left
Female
Table 2 Mean impulses (kg s) and corresponding confidence intervals, showing the significant interaction between condition and gender.
Right
Left
95% confidence interval*
* Estimated from the mixed model with the following terms in the model: gender (P = 0.898), side (P < 0.001), condition (P < 0.001), side × condition (P = 0.081), gender × condition (P < 0.001), gender × side (P < 0.001).
Side
Gender
Mean
95% confidence interval Lower limit
Upper limit
Right
Male Female
2.397 2.160
1.749 1.599
3.044 2.720
Left
Male Female
2.772 2.900
2.124 2.339
3.419 3.461
4. Discussion The use of orthotics and shoe modifications such as metatarsal pads and bars in patients with metatarsalgia has a proven beneficial effect on pain relief. This is attributed to the reduction in pressure on the metatarsal heads. On the other hand, some studies were unable to correlate the reduction of impulses over the central middle forefoot to pain scores [9]. Holmes and Timmerman demonstrated reductions in metatarsal peak pressures of up to 60% with the use of metatarsal pads in 10 asymptomatic subjects [6]. Hayda et al. also tested three pad types in 10 healthy volunteers [10]. They found the small felt pad type at the distal positioning to have the greatest effect on pressure reduction. Jackson et al. compared the effect of prefabricated insoles incorporating either metatarsal pads or bars to a shoe-only control condition in 12 rheumatoid patients [11]. In the central metatarsal head region both devices resulted in reduced peak pressures with the bars being more effective than the pads. This concurs with our findings. We found an up to 51% reduction in impulses below the second metatarsal head with the use of metatarsal bars. The data on the effect of the use of custom-made orthotics in pain relief for symptomatic feet remains rather limited and conflicting [4,8]. The evidence for conditions such as painful pes cavus is stronger than in other diseases, such as juvenile idiopathic arthritis, hallux valgus and plantar fasciitis. In the latter, Pfeffer et al. showed superior results of over-the-counter prefabricated orthotics to custom made ones [12]. In the case of paediatric flat feet, one study showed no difference in the number of participants with foot pain between custom-made orthoses, prefabricated orthoses and the control group who received no treatment [13]. Finally, in a diverse patient population with forefoot pain, Stolwijk et al. demonstrated a similar effectiveness on pain relief and plantar pressure redistribution among insoles of a different design [14]. In general, currently there seems to be no strong evidence regarding the superiority of using custom-made orthoses to prefabricated ones in a number of foot conditions [5]. The optimum position of the metatarsal pads and bars in relation with the metatarsal heads has been previously debated [15]. Currently most authors agree that the best position for the metatarsal
A. Deshaies et al. / The Foot 21 (2011) 172–175
pads is just proximal to the affected metatarsal head and this position was also used in the current study. No such consensus exists for the metatarsal bars. Therefore, part of the study was to compare two different positions of the bars. The oblique position along a line subtended by the heads of the first and the fifth metatarsal has a more anatomic rationale, as it falls closer to the normal metatarsal head arc. Moreover, the bar in this position acts just proximal to the second metatarsal head, which probably is the ideal position. In our study group the lowest impulses were achieved with this oblique position. In the current study healthy subjects were chosen to evaluate the impulse reduction effect of the orthotics. Many authors have also used asymptomatic volunteers as their study group [6,16–20]. Although the exclusion of patients with symptomatic forefeet can be considered a limitation of the study, the rationale of such a study design is to isolate the impulse reduction effect of any given orthotic device on feet with a previously normal pressure distribution. Therefore, this data can prove useful as a reference basis for further relevant studies. Unless the effectiveness of any pressure-reducing orthotic devise on healthy feet is documented, no reliable conclusions can be drawn from patient groups alone. Recent clinical studies have demonstrated a remarkable lack of agreement regarding the location of high pressure zones and subsequent insole design in patients with metatarsalgia between foot experts [21,22]. These results challenge the reproducibility of recommendations based on previous studies in the clinical practice. To the best of our knowledge, this is the first study to directly compare the efficacy of external metatarsal bars over metatarsal pads in reducing impulse over the second metatarsal head in healthy subjects. The F-scan Mobile System, which was used to assess impulse reduction has also been used successfully in previous relevant studies [23]. An additional strength is that both feet for each subject were studied and data on each side confirmed the data on the contralateral. A limitation of the study is that the subjects’ walking speed and cadence was not documented. This would provide useful additional information of the effect on walking speed of each of the orthotics in the different conditions. A further limitation is that the subjects were wearing their own running shoes and this parameter was not standardized. A number of authors have also proceeded this way in their studies [11,19,23,24]. Since each subject was his or her own control, the related impact of this factor, if any, is probably limited. A third limitation is that the outlining of the second metatarsal head area on the pressure graph was not based on a standing anteroposterior radiograph of the subjects’ feet and therefore may not be anatomically accurate. We felt however that the involvement of healthy volunteers only as our study population could not justify their exposure to radiation. Moreover, the outlining of the second metatarsal head area was performed by an orthopaedic surgeon in order to achieve reliable calculations. For certain conditions, differences between males and females were recorded in the current study. Recently, Queen et al. found that men demonstrated a significant increase in maximum force beneath the medial forefoot when running in training shoes when compared to females [25]. Gender related differences in plantar loading forces have also been studied during specific tasks, showing an overall increased plantar loading in male athletes [26]. Murphy et al. on the other hand, found no significant differences in plantar pressure values between male and female athletes [24]. Left feet impulses were found to be higher to the right side ones. It can be argued that the majority of our study population was right handed and they would bring the left foot forward, probably applying more force, at the initiation of their gait cycle. However, we could not explain this finding from our data or from previous relevant studies.
175
In summary, both metatarsal pads and external metatarsal bars significantly reduce the impulse on the second metatarsal head in healthy subjects. Metatarsal bars are more effective than metatarsal pads in impulse reduction. Although the current study was based on asymptomatic volunteers and its results may not be directly clinically applicable, our findings support the use of metatarsal pads and bars in the conservative treatment of metatarsalgia of the second metatarsal head. References [1] Dockery G. Evaluation and treatment of metatarsalgia and keratotic disorders. In: Myerson M, editor. Foot and ankle disorders. Philadelphia: W.B. Saunders Co; 2000. p. 359–77. [2] Fuhrmann RA, Roth A, Venbrocks RA. Metatarsalgia. Differential diagnosis and therapeutic algorithm. Orthopade 2005;34, 767–8, 9–72, 74–5. [3] Katcherian DA. Treatment of Freiberg’s disease. Orthop Clin North Am 1994;25:69–81. [4] Jannink M, van Dijk H, Ijzerman M, Groothuis-Oudshoorn K, Groothoff J, Lankhurst G. Effectiveness of custom-made orthopaedic shoes in the reduction of foot pain and pressure in patients with degenerative disorders of the foot. Foot Ankle Int 2006;27:974–9. [5] Nawoczenski DA, Janisse DJ. Foot orthoses in rehabilitation—what’s new. Clin Sports Med 2004;23:157–67. [6] Holmes Jr GB, Timmerman L. A quantitative assessment of the effect of metatarsal pads on plantar pressures. Foot Ankle 1990;11:141–5. [7] Praet SF, Louwerens JW. The influence of shoe design on plantar pressures in neuropathic feet. Diabetes Care 2003;26:441–5. [8] Hawke F, Burns J, Radford JA, du Toit V. Custom-made foot orthoses for the treatment of foot pain. Cochrane Database Syst Rev 2008;16. CD006801. [9] Postema K, Burm PE, Zande ME, Limbeek J. Primary metatarsalgia: the influence of a custom moulded insole and a rockerbar on plantar pressure. Prosthet Orthot Int 1998;22:35–44. [10] Hayda R, Tremaine MD, Tremaine K, Banco S, Teed K. Effect of metatarsal pads and their positioning: a quantitative assessment. Foot Ankle Int 1994;15:561–6. [11] Jackson L, Binning J, Potter J. Plantar pressures in rheumatoid arthritis using prefabricated metatarsal padding. J Am Podiatr Med Assoc 2004;94: 239–45. [12] Pfeffer G, Bacchetti P, Deland J, Lewis A, Anderson R, Davis W, et al. Comparison of custom and prefabricated orthoses in the initial treatment of proximal plantar fasciitis. Foot Ankle Int 1999;20:214–21. [13] Rome K, Ashford RL, Evans A. Non-surgical interventions for paediatric pes planus. Cochrane Database Syst Rev 2010;7:CD006311. [14] Stolwijk NM, Louwerens JW, Nienhuis B, Duysens J, Keijsers NL. Plantar pressure with and without custom insoles in patients with common foot complaints. Foot Ankle Int 2011;32:57–65. [15] Hsi WL, Kang JH, Lee XX. Optimum position of metatarsal pad in metatarsalgia for pressure relief. Am J Phys Med Rehabil 2005;84:514–20. [16] Chang AH, Abu-Faraj ZU, Harris GF, Nery J, Shereff MJ. Multistep measurement of plantar pressure alterations using metatarsal pads. Foot Ankle Int 1994;15:654–60. [17] Burgess S, Jordan C, Bartlett R. The influence of a small insert, in the footbed of a shoe, upon plantar pressure distribution. Clin Biomech (Bristol, Avon) 1997;12:S5–6. [18] Hinz P, Henningsen A, Matthes G, Jager B, Ekkernkamp A, Rosenbaum D. Analysis of pressure distribution below the metatarsals with different insoles in combat boots of the German Army for prevention of march fractures. Gait Posture 2007. [19] Mueller MJ, Strube MJ. Generalizability of in-shoe peak pressure measures using the F-scan system. Clin Biomech (Bristol, Avon) 1996;11:159– 64. [20] Novick A, Stone J, Birke JA, Brasseaux DM, Broussard JB, Hoard AS, et al. Reduction of plantar pressure with the rigid relief orthosis. J Am Podiatr Med Assoc 1993;83:115–22. [21] Guldemond NA, Leffers P, Schaper NC, Sanders AP, Nieman FH, Walenkamp GH. Comparison of foot orthoses made by podiatrists, pedorthists and orthotists regarding plantar pressure reduction in The Netherlands. BMC Musculoskelet Disord 2005;6:61. [22] Guldemond NA, Leffers P, Nieman FH, Sanders AP, Schaper NC, Walenkamp GH. Testing the proficiency to distinguish locations with elevated plantar pressure within and between professional groups of foot therapists. BMC Musculoskelet Disord 2006;7:93. [23] Ahroni JH, Boyko EJ, Forsberg R. Reliability of F-scan in-shoe measurements of plantar pressure. Foot Ankle Int 1998;19:668–73. [24] Murphy DF, Beynnon BD, Michelson JD, Vacek PM. Efficacy of plantar loading parameters during gait in terms of reliability, variability, effect of gender and relationship between contact area and plantar pressure. Foot Ankle Int 2005;26:171–9. [25] Queen RM, Abbey AN, Wiegerinck JI, Yoder JC, Nunley JA. Effect of shoe type on plantar pressure: a gender comparison. Gait Posture 2009;31:18–22. [26] Sims EL, Hardaker WM, Queen RM. Gender differences in plantar loading during three soccer-specific tasks. Br J Sports Med 2008;42:272–7.
Contents lists available at ScienceDirect
The Foot journal homepage: www.elsevier.com/locate/foot
Metatarsal bars more effective than metatarsal pads in reducing impulse on the second metatarsal head Annie Deshaies a , Patrice Roy b , Panagiotis D. Symeonidis c,∗ , Bernard LaRue a , Norman Murphy d , Éric Anctil a a
University of Sherbrooke Hospitals, Orthopaedic Service, CHUS-Hôtel Dieu, 580, rue Bowen sud, Sherbrooke, Québec J1G 2E8, Canada Clinique Podiatrique de l’Estrie, 1135 Boul Jacques-Cartier, Sherbrooke, Québec J1J 3A8, Canada c E.Amynis 18, 54621 Thessaloniki, Greece d Tekscan, 4710 des Chanterelles, Rock-Forest, Québec J1N 4J6, Canada b
a r t i c l e
i n f o
Article history: Received 9 February 2011 Received in revised form 20 April 2011 Accepted 8 May 2011 Keywords: Metatarsalgia Impulse Pads Bars
a b s t r a c t Background: The second metatarsal head is commonly involved in cases of metatarsalgia. As part of the conservative treatment, metatarsal bars and metatarsal pads are often prescribed. Objective: To compare the effectiveness of metatarsal bars and metatarsal pads in reducing impulse on the second metatarsal head. Method: Thirty-five healthy subjects were monitored with an insole scanning system during walking in four different conditions: (a) wearing shoes only, (b) shoes plus metatarsal pads and shoes plus metatarsal bars, placed either (c) perpendicular to the foot axis or (d) oblique to the foot axis. The impulse under the second metatarsal head was measured using the first condition as a control. Both feet were examined in each subject resulting in a total of 840 measurements. Results: Both metatarsal bars and metatarsal pads were effective in reducing impulse when compared with the control (P < 0.01). Metatarsal bars were found to be more effective in reducing impulse as compared to the metatarsal pads (P < 0.01), and the oblique position of the bars was more effective than the perpendicular one (P < 0.01). Conclusions: The greatest reduction of impulse on the second metatarsal head in healthy subjects is achieved with the use of metatarsal bars in an oblique position. © 2011 Elsevier Ltd. All rights reserved.
1. Introduction Metatarsalgia is defined as pain in the region of the distal aspect of one or more of the metatarsals during weightbearing [1]. It is one of the commonest foot symptoms encountered in orthopaedic and podiatric practices and can result either from physiologic loading on pathological structures or by excessive loading on normal structures. The second metatarsal head is commonly affected by metatarsalgia [2]. This may occur primarily by a relatively longer second metatarsal, which results in increased pressure and friction during the propulsive phase of gait. Secondary metatarsalgia is caused by various metabolic, neurologic and traumatic conditions, which alter the mechanical load of the forefoot. Forefoot surgery on the first or second ray, which alters the relative metatarsal length, can also result in metatarsalgia over the second metatarsal head.
∗ Corresponding author. Tel.: +30 2310 258100; fax: +30 2310 258101. E-mail address: [email protected] (P.D. Symeonidis). 0958-2592/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foot.2011.05.001
Finally, Freiberg’s infraction has a marked predilection for the second metatarsal head [3]. The conservative treatment of metatarsalgia frequently includes the use of metatarsal pads and metatarsal bars. These orthotics and shoe modifications act by reducing the pressure on metatarsal heads which is related to pain relief, although the evidence regarding their effectiveness remains meager and conflicting [4,5]. Proper use of the orthotics can result in up to 60% of pressure reduction [6]. Metatarsal pads are insole devices with the advantage of high patients’ compliance. On the other hand, metatarsal bars are shoe modifications placed on the outside sole and are therefore more cumbersome and not always well tolerated by patients. Despite the widespread use of orthotics in the treatment of metatarsalgia current literature lacks sufficient evidence regarding the superiority of one over the other [5,7,8]. We compared the efficacy of metatarsal pads to external metatarsal bars in reducing impulse on the second metatarsal head in normal subjects. We also studied different positions of the bar and their effect on impulse reduction.
A. Deshaies et al. / The Foot 21 (2011) 172–175
173
2. Patients and methods Thirty-five healthy subjects aged from 15 to 65 years (mean age = 38 years) with asymptomatic feet volunteered for the study. There were 15 men and 20 women. Exclusion criteria for participation were any condition which could affect the subject’s gait or posture such as history of previous trauma or surgery of the foot and ankle, congenital or acquired foot deformities, lower limb malalignment, use of walking aids and any systemic disease that can affect walking. Both feet were evaluated for each subject. Each volunteer was asked to walk at his own walking speed and rhythm on a straight path for ten meters under four different conditions: (a) walking with shoes only, (b) walking with shoes and metatarsal pads (Fig. 1), (c) walking with shoes reinforced with metatarsal bars placed perpendicularly to the foot axis (Fig. 2a) and (d) Walking with shoes reinforced with metatarsal bars placed obliquely to the foot axis, along a line subtended by the heads of the first and the fifth metatarsal (Fig. 2b). In order to avoid the effect of abnormal patterns on the initiation of walking and stopping, only steps 2–7 from each condition were retained for analysis. Therefore, data for three right foot and three left footsteps was analyzed for each person resulting in six steps for each condition and a total of 24 measurements per person. This resulted in 840 measurements for the whole study group. Metatarsal pads and bars were adjusted to the subjects’ own running shoes by a trained podiatrist (PR). The shoes used by the volunteers were commercial soft sole shoes with laces. The metatarsal pads were prefabricated (model P407, JMS Plastics Supply Inc, Neptune, NJ) and made of Poron® , a microcellular urethane foam. They were 8 mm thick at the apex and had a longitudinal axis Fig. 2. Different positions of the metatarsal bars: perpendicular to the foot axis in the right shoe and obliquely in the left shoe.
Fig. 1. Metatarsal pads placed on the inside soles.
of 5.2 cm and a transverse axis of 4.5 cm. An adhesive flat backing permitted stable placement on each subject’s inner sole. The bars (model P406, JMS Plastics Supply Inc, Neptune, NJ) were made of a high-density rubber material (black neuron) and had the shape of a half-cylinder with a radius of 10 mm. Impulse (force-time integral in kg s) represents the load of a certain area in relation to the time the area is loaded. In the current study, impulses were recorded with the use of the F-scan bipedal inshoe analysis Mobile System (Tekscan, Boston, Massachusetts) in each of the four walking conditions. This device utilizes paper-thin sensors (F-Scan 3000) inserted inside the shoes and permits precise impulse measurement. There are four sensors per cm2 . Transfer units are placed around the ankle and linked to a battery belt pack permitting free ambulation. The sensors were calibrated and tailored to fit each subject’s shoes appropriately. According to the products guidelines, the sensors can be used 10–15 times before disposal. For the purposes of the current study, each sensor was used five times only. Data were analyzed using Research Foot Software Version 5.72. The program produces a graph using different colors for each step to indicate different impulse levels. The area underneath the second metatarsal head was outlined on each graph by one author (AD) who was blinded for the type of intervention. For each of the selected areas, the resulting impulse was calculated by the computer software. Each impulse represents the amount of loading pressure for the period of time during which it is applied, namely the duration of each step. The mean impulse of each foot was calculated in all four conditions. Therefore, for each of the 35 volunteers four left-foot and
174
A. Deshaies et al. / The Foot 21 (2011) 172–175
four right-foot mean impulses were calculated which resulted in a total of 280 mean impulses. A mixed model was used to account for the repeated measurements. In more detail, the following terms were considered in this multilevel model: condition, side, gender, condition × side, condition × gender, side × gender. Also the three-way interaction term condition × side × gender was considered but it was not significant, therefore the multilevel model with the two-term interactions was fitted. The mean and the corresponding 95% confidence intervals were presented. The pairwise comparisons between conditions were tested with paired Student’s t-tests and the Bonferroniadjusted P-values were reported. All analyses were conducted using SPSS 17 (SPSS, Inc., Chicago, IL). All reported P-values were two-tailed with P < 0.05 considered as significant.
Condition
Gender
Mean
95% confidence interval Lower limit
Upper limit
Shoes
Male Female
3.714 3.456
3.059 2.889
4.369 4.023
Met pads
Male Female
2.943 2.650
2.293 2.088
3.592 3.213
Straight bar
Male Female
1.979 2.181
1.324 1.614
2.633 2.747
Oblique bar
Male Female
1.701 1.832
1.053 1.271
2.350 2.394
Table 3 Mean impulses (kg s) and corresponding confidence intervals, showing the significant interaction between side and gender.
3. Results The mean impulses for both feet were reduced with the use of both metatarsal bars and metatarsal pads (Table 1) Men had higher impulses than women, the differences not being significant (Table 1; P = 0.898). Left feet impulses were significantly higher than the right side (P < 0.001). There was a significant difference in impulses among the four conditions (condition P < 0.001) showing that the impulses were significantly higher with the shoes only condition compared to the other three conditions (Bonferroni-adjusted P-value, P < 0.001 for all three comparisons). Moreover, the impulses were higher with the metatarsal pads compared to the straight and oblique bars (Bonferroni-adjusted P-value, P < 0.001 for both comparisons). Last, the oblique position of the bars was significantly more effective than the straight one (Bonferroni-adjusted Pvalue, P < 0.001). There was a significant interaction between gender and condition (P < 0.001) showing that the impulses were higher in men than in women in the shoes only condition and the pads, while they were higher in women than in men in the other two conditions with the bars (Table 2). Furthermore, there was a significant interaction between gender and side (P < 0.001), showing that the impulses were higher in men for the right side while they were higher in women for the left side (Table 3).
Table 1 Mean impulses (kg s) and corresponding confidence intervals. Gender
Side
Condition
Mean*
Lower limit
Upper limit
Male
Right
Shoes Met pads Straight bar Oblique bar Shoes Met pads Straight bar Oblique bar
3.513 2.819 1.786 1.469 3.916 3.066 2.171 1.933
2.855 2.167 1.122 .817 3.252 2.412 1.515 1.281
4.171 3.472 2.450 2.122 4.580 3.721 2.827 2.585
Shoes Met pads Straight bar Oblique bar Shoes Met pads Straight bar Oblique bar
3.072 2.344 1.805 1.418 3.840 2.957 2.556 2.247
2.502 1.779 1.228 .853 3.264 2.389 1.987 1.682
3.642 2.909 2.382 1.983 4.417 3.524 3.125 2.812
Left
Female
Table 2 Mean impulses (kg s) and corresponding confidence intervals, showing the significant interaction between condition and gender.
Right
Left
95% confidence interval*
* Estimated from the mixed model with the following terms in the model: gender (P = 0.898), side (P < 0.001), condition (P < 0.001), side × condition (P = 0.081), gender × condition (P < 0.001), gender × side (P < 0.001).
Side
Gender
Mean
95% confidence interval Lower limit
Upper limit
Right
Male Female
2.397 2.160
1.749 1.599
3.044 2.720
Left
Male Female
2.772 2.900
2.124 2.339
3.419 3.461
4. Discussion The use of orthotics and shoe modifications such as metatarsal pads and bars in patients with metatarsalgia has a proven beneficial effect on pain relief. This is attributed to the reduction in pressure on the metatarsal heads. On the other hand, some studies were unable to correlate the reduction of impulses over the central middle forefoot to pain scores [9]. Holmes and Timmerman demonstrated reductions in metatarsal peak pressures of up to 60% with the use of metatarsal pads in 10 asymptomatic subjects [6]. Hayda et al. also tested three pad types in 10 healthy volunteers [10]. They found the small felt pad type at the distal positioning to have the greatest effect on pressure reduction. Jackson et al. compared the effect of prefabricated insoles incorporating either metatarsal pads or bars to a shoe-only control condition in 12 rheumatoid patients [11]. In the central metatarsal head region both devices resulted in reduced peak pressures with the bars being more effective than the pads. This concurs with our findings. We found an up to 51% reduction in impulses below the second metatarsal head with the use of metatarsal bars. The data on the effect of the use of custom-made orthotics in pain relief for symptomatic feet remains rather limited and conflicting [4,8]. The evidence for conditions such as painful pes cavus is stronger than in other diseases, such as juvenile idiopathic arthritis, hallux valgus and plantar fasciitis. In the latter, Pfeffer et al. showed superior results of over-the-counter prefabricated orthotics to custom made ones [12]. In the case of paediatric flat feet, one study showed no difference in the number of participants with foot pain between custom-made orthoses, prefabricated orthoses and the control group who received no treatment [13]. Finally, in a diverse patient population with forefoot pain, Stolwijk et al. demonstrated a similar effectiveness on pain relief and plantar pressure redistribution among insoles of a different design [14]. In general, currently there seems to be no strong evidence regarding the superiority of using custom-made orthoses to prefabricated ones in a number of foot conditions [5]. The optimum position of the metatarsal pads and bars in relation with the metatarsal heads has been previously debated [15]. Currently most authors agree that the best position for the metatarsal
A. Deshaies et al. / The Foot 21 (2011) 172–175
pads is just proximal to the affected metatarsal head and this position was also used in the current study. No such consensus exists for the metatarsal bars. Therefore, part of the study was to compare two different positions of the bars. The oblique position along a line subtended by the heads of the first and the fifth metatarsal has a more anatomic rationale, as it falls closer to the normal metatarsal head arc. Moreover, the bar in this position acts just proximal to the second metatarsal head, which probably is the ideal position. In our study group the lowest impulses were achieved with this oblique position. In the current study healthy subjects were chosen to evaluate the impulse reduction effect of the orthotics. Many authors have also used asymptomatic volunteers as their study group [6,16–20]. Although the exclusion of patients with symptomatic forefeet can be considered a limitation of the study, the rationale of such a study design is to isolate the impulse reduction effect of any given orthotic device on feet with a previously normal pressure distribution. Therefore, this data can prove useful as a reference basis for further relevant studies. Unless the effectiveness of any pressure-reducing orthotic devise on healthy feet is documented, no reliable conclusions can be drawn from patient groups alone. Recent clinical studies have demonstrated a remarkable lack of agreement regarding the location of high pressure zones and subsequent insole design in patients with metatarsalgia between foot experts [21,22]. These results challenge the reproducibility of recommendations based on previous studies in the clinical practice. To the best of our knowledge, this is the first study to directly compare the efficacy of external metatarsal bars over metatarsal pads in reducing impulse over the second metatarsal head in healthy subjects. The F-scan Mobile System, which was used to assess impulse reduction has also been used successfully in previous relevant studies [23]. An additional strength is that both feet for each subject were studied and data on each side confirmed the data on the contralateral. A limitation of the study is that the subjects’ walking speed and cadence was not documented. This would provide useful additional information of the effect on walking speed of each of the orthotics in the different conditions. A further limitation is that the subjects were wearing their own running shoes and this parameter was not standardized. A number of authors have also proceeded this way in their studies [11,19,23,24]. Since each subject was his or her own control, the related impact of this factor, if any, is probably limited. A third limitation is that the outlining of the second metatarsal head area on the pressure graph was not based on a standing anteroposterior radiograph of the subjects’ feet and therefore may not be anatomically accurate. We felt however that the involvement of healthy volunteers only as our study population could not justify their exposure to radiation. Moreover, the outlining of the second metatarsal head area was performed by an orthopaedic surgeon in order to achieve reliable calculations. For certain conditions, differences between males and females were recorded in the current study. Recently, Queen et al. found that men demonstrated a significant increase in maximum force beneath the medial forefoot when running in training shoes when compared to females [25]. Gender related differences in plantar loading forces have also been studied during specific tasks, showing an overall increased plantar loading in male athletes [26]. Murphy et al. on the other hand, found no significant differences in plantar pressure values between male and female athletes [24]. Left feet impulses were found to be higher to the right side ones. It can be argued that the majority of our study population was right handed and they would bring the left foot forward, probably applying more force, at the initiation of their gait cycle. However, we could not explain this finding from our data or from previous relevant studies.
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In summary, both metatarsal pads and external metatarsal bars significantly reduce the impulse on the second metatarsal head in healthy subjects. Metatarsal bars are more effective than metatarsal pads in impulse reduction. Although the current study was based on asymptomatic volunteers and its results may not be directly clinically applicable, our findings support the use of metatarsal pads and bars in the conservative treatment of metatarsalgia of the second metatarsal head. References [1] Dockery G. Evaluation and treatment of metatarsalgia and keratotic disorders. In: Myerson M, editor. Foot and ankle disorders. Philadelphia: W.B. Saunders Co; 2000. p. 359–77. [2] Fuhrmann RA, Roth A, Venbrocks RA. Metatarsalgia. Differential diagnosis and therapeutic algorithm. Orthopade 2005;34, 767–8, 9–72, 74–5. [3] Katcherian DA. Treatment of Freiberg’s disease. Orthop Clin North Am 1994;25:69–81. [4] Jannink M, van Dijk H, Ijzerman M, Groothuis-Oudshoorn K, Groothoff J, Lankhurst G. Effectiveness of custom-made orthopaedic shoes in the reduction of foot pain and pressure in patients with degenerative disorders of the foot. Foot Ankle Int 2006;27:974–9. [5] Nawoczenski DA, Janisse DJ. Foot orthoses in rehabilitation—what’s new. Clin Sports Med 2004;23:157–67. [6] Holmes Jr GB, Timmerman L. A quantitative assessment of the effect of metatarsal pads on plantar pressures. Foot Ankle 1990;11:141–5. [7] Praet SF, Louwerens JW. The influence of shoe design on plantar pressures in neuropathic feet. Diabetes Care 2003;26:441–5. [8] Hawke F, Burns J, Radford JA, du Toit V. Custom-made foot orthoses for the treatment of foot pain. Cochrane Database Syst Rev 2008;16. CD006801. [9] Postema K, Burm PE, Zande ME, Limbeek J. Primary metatarsalgia: the influence of a custom moulded insole and a rockerbar on plantar pressure. Prosthet Orthot Int 1998;22:35–44. [10] Hayda R, Tremaine MD, Tremaine K, Banco S, Teed K. Effect of metatarsal pads and their positioning: a quantitative assessment. Foot Ankle Int 1994;15:561–6. [11] Jackson L, Binning J, Potter J. Plantar pressures in rheumatoid arthritis using prefabricated metatarsal padding. J Am Podiatr Med Assoc 2004;94: 239–45. [12] Pfeffer G, Bacchetti P, Deland J, Lewis A, Anderson R, Davis W, et al. Comparison of custom and prefabricated orthoses in the initial treatment of proximal plantar fasciitis. Foot Ankle Int 1999;20:214–21. [13] Rome K, Ashford RL, Evans A. Non-surgical interventions for paediatric pes planus. Cochrane Database Syst Rev 2010;7:CD006311. [14] Stolwijk NM, Louwerens JW, Nienhuis B, Duysens J, Keijsers NL. Plantar pressure with and without custom insoles in patients with common foot complaints. Foot Ankle Int 2011;32:57–65. [15] Hsi WL, Kang JH, Lee XX. Optimum position of metatarsal pad in metatarsalgia for pressure relief. Am J Phys Med Rehabil 2005;84:514–20. [16] Chang AH, Abu-Faraj ZU, Harris GF, Nery J, Shereff MJ. Multistep measurement of plantar pressure alterations using metatarsal pads. Foot Ankle Int 1994;15:654–60. [17] Burgess S, Jordan C, Bartlett R. The influence of a small insert, in the footbed of a shoe, upon plantar pressure distribution. Clin Biomech (Bristol, Avon) 1997;12:S5–6. [18] Hinz P, Henningsen A, Matthes G, Jager B, Ekkernkamp A, Rosenbaum D. Analysis of pressure distribution below the metatarsals with different insoles in combat boots of the German Army for prevention of march fractures. Gait Posture 2007. [19] Mueller MJ, Strube MJ. Generalizability of in-shoe peak pressure measures using the F-scan system. Clin Biomech (Bristol, Avon) 1996;11:159– 64. [20] Novick A, Stone J, Birke JA, Brasseaux DM, Broussard JB, Hoard AS, et al. Reduction of plantar pressure with the rigid relief orthosis. J Am Podiatr Med Assoc 1993;83:115–22. [21] Guldemond NA, Leffers P, Schaper NC, Sanders AP, Nieman FH, Walenkamp GH. Comparison of foot orthoses made by podiatrists, pedorthists and orthotists regarding plantar pressure reduction in The Netherlands. BMC Musculoskelet Disord 2005;6:61. [22] Guldemond NA, Leffers P, Nieman FH, Sanders AP, Schaper NC, Walenkamp GH. Testing the proficiency to distinguish locations with elevated plantar pressure within and between professional groups of foot therapists. BMC Musculoskelet Disord 2006;7:93. [23] Ahroni JH, Boyko EJ, Forsberg R. Reliability of F-scan in-shoe measurements of plantar pressure. Foot Ankle Int 1998;19:668–73. [24] Murphy DF, Beynnon BD, Michelson JD, Vacek PM. Efficacy of plantar loading parameters during gait in terms of reliability, variability, effect of gender and relationship between contact area and plantar pressure. Foot Ankle Int 2005;26:171–9. [25] Queen RM, Abbey AN, Wiegerinck JI, Yoder JC, Nunley JA. Effect of shoe type on plantar pressure: a gender comparison. Gait Posture 2009;31:18–22. [26] Sims EL, Hardaker WM, Queen RM. Gender differences in plantar loading during three soccer-specific tasks. Br J Sports Med 2008;42:272–7.