Effect of custom-made foot orthoses in female hallux valgus after one-year follow up

Effect of custom-made foot orthoses in female hallux valgus after one year followup ABSTRACT STUDY DESIGN: Prospective trial, using a repeated-measures design. BACKGROUND: Subtalar joint hyperpronation plays a fundamental role in the development of hallux valgus; then treating this condition with foot orthotics should prevent progress of the deformity. OBJECTIVES: The aim of this study was to determine whether the use of custom-made foot orthoses for 12 months prevented the advance of hallux valgus in women. MATERIAL AND METHODS: Fifty-four women with mild to moderate hallux valgus were divided into two groups: the experimental group used custom-made foot orthoses, and the control group used no treatment. First Intermetatarsal (IMA) and hallux abductus (HAA) angles were measured at the beginning of the study and after 12 months followup. Inter-group comparisons were made of these angles at both times of measurement, and intra-group comparisons between the two times of measurement. RESULTS: The initial HAA was similar in both groups (19.92 ± 4.25 degrees for the control group, 20.55 ± 5.10 degrees for the experimental group; p = 0.392), and also the IMA (10.56 ± 2.45 degrees for the control group, 10.86 ± 2.33 for the experimental group; p = 0.618) There were no significant differences in the followup values of these angles (p = 0.395 and p = 0.288, respectively). There were no significant intra-group differences in the comparisons of the initial and followup angles. CONCLUSIONS: Hallux valgus did not have a significantly slower evolution in participants of the experimental group comparing with controls, so the custom made orthotics seems to have no effect in the evolution of mild and moderate hallux valgus. Word count of the abstract: 257 words. CLINICAL RELEVANCE If subtalar joint hyperpronation plays a fundamental role in the development of hallux valgus, then controlling the abnormal mobility of this joint by means of foot orthotics should prevent or control progress of the condition. This paper could help solve this controversy. Word count of the clinical relevance statement: 42 words. BACKGROUND In hallux valgus (HV) the great toe is deviated laterally and the first metatarsal medially, resulting in a medial bony prominence at the first metatarsophalangeal joint (MPJ). 1, 2 The exact ætiology of the development of HV is not entirely clear. According to many authors, the development of HV is multi-factorial, including both intrinsic and extrinsic factors. 3-11 The commonest cause of adult HV is a combination of environmental factors (e.g., mechanical abnormalities caused by badly fitting footwear) and a genetic predisposition to constitutional anatomical factors, with some authors describing the latter to be involved in 70% of cases. 4, 12 However, in most cases there is a clear biomechanical base ætiology. Excessive pronation of the subtalar joint during the stance phase of gait is responsible for instability of the foot, causing dysfunction of the first ray and the first MPJ, leading to deformities as HV. 1, 6, 8, 13-15 If subtalar joint hyperpronation plays a fundamental role in the development of HV, then controlling the abnormal mobility of this joint by means of foot orthotics should prevent or control progress of the condition. But even though there have been various studies of the effectiveness of such conservative treatments, they have led to a situation of some controversy. Some longitudinal studies have reported that foot orthoses are effective in preventing HV while others have refuted this claim. The present work was aimed at responding to the question of whether treatment with custom-made foot orthotics can reduce or slow down the progress of HV in women with mild to moderate HV (according to the classification of Kelikian 16), after a 12-month followup period. The null hypothesis is that foot orthoses have no effect in controlling the advance of HV, i.e., that the study participants using foot orthoses for 12 months would have the same increase in HV as participants who did not use them. METHODS Subjects A prospective trial, using a repeated-measures study was carried out with 54 women of mean age 30.63 ± 11.87 years with mild to moderate HV (97 affected feet). Each foot was counted as a separate case, since for a given participant only one foot may be affected. The participants were volunteers from three sources: students of Podiatry at the Xxxxxxxxxx xx Xxxxxxx (30 women); patients attending the Podiatry Clinic Area at the Xxxxxxxxxx xx Xxxxxxx who met the inclusion criteria and agreed to participate voluntarily in the study (11 women); and staff of this centre who, when they heard of the study, decided to volunteer (13 women). Patients were divided into two groups – an experimental group corresponding to participants to whom the use of foot orthotics was applied, and a control group corresponding to participants to whom no treatment was applied. Data for the study were collected between January 2008 and November 2011, at the Podiatry Clinic Area of the Xxxxxxxxxx xx Xxxxxxx (XXXXX). The study was approved by the Experimentation Ethics Committee of the Xxxxxxxxxx xx Xxxxxxx. Allocation to either the control or the experimental group was as follows (see flow diagram in figure 1). All the women who met the inclusion criteria and had attended the Podiatry Clinic Area at the Xxxxxxxxxx xx Xxxxxxx seeking treatment with orthotics and had agreed to participate in the study were assigned to the experimental group (11 participants). For ethical reasons, and to maintain the quality of care provided by this centre, the authors believed that when patients had presented seeking treatment they could not be assigned to the control group because this would have meant 12 months without treatment. To prevent this producing heterogeneity between the groups, it was used the technique of matching on grounds of age and severity of the HV to choose the first 11 participants to include in the control group. The remaining participants (32 people) voluntarily asked to participate in the study, and they were randomly assigned to the groups (coin toss). Originally, the control group consisted of 48 feet of 26 women, mean age 30.31 ± 9.27 years, and the experimental group of 49 feet of 28 women, mean age 30.94 ± 14.05 years. In the control group, three women did not attend the 12-month followup study for the following reasons: one of them because of change of residence and two did not attend on the day set for the followup (unknown reasons). In the experimental group, five women did not attend the 12-month followup study for the following reasons: one of them for pregnancy, another one because she had lost the foot orthoses, and three did not attend on the day set for the followup (unknown reasons). The final sample consisted of 46 women (83 feet), aged 30.63 ± 11.87 years. Control group consisted of 23 women (42 feet) aged 30.94 ± 14.06 years, and experimental group consisted of 23 women (41 feet) aged 30.31 ± 9.27 years. Insert figure 1. Inclusion criteria One selection criterion was that the growth physes of the participant's bones should be closed for there to be no possibility of variation in any of the parameters measured due to growth. Other inclusion criteria were: having an inclination angle of the calcaneus to the ground greater than five degrees, and presenting an HV angle greater than 15 degrees and lower than 40 degrees. Exclusion criteria were: having undergone osteoarticular surgery on the foot; having suffered serious injury to the foot that could have altered its bone morphology; having received orthopædic treatment; suffering from degenerative bone and joint diseases or neuromuscular imbalances; obvious deformities other than HV in the forefoot that might affect the results of the study; pregnancy; women who experienced poor acceptance of the treatment, or who refused the X-ray of the feet. Variables The independent variable was the use of foot orthoses. The dependent variables were the intermetatarsal angle between the first and second metatarsals (first IMA) and the hallux abductus angle (HAA) (Figure 2). These variables were measured at the beginning of the study (initial) and after one year (followup) so that comparisons could be made. The HAA is a measure of the deviation of the proximal phalanx of the hallux with respect to the longitudinal axis of the first metatarsal. It is considered to be the principal parameter with which to quantify the HV deformity.15 The first IMA is considered to be the best measure of the medial deviation of the first metatarsal in the transverse plane – one of the components of the HV deformity.17 Insert figure 2. Procedure Each participant was given an informative document which explained the nature of the research, its objectives, and its potential risks. If, after reading it and having any doubts clarified, she agreed to participate, she was asked to provide her written consent. For each participant, a data sheet was prepared with her parentage data and an anamnesis. Articular explorations were made with the participant on the examination table, standing, and walking, following the protocol used in the Podiatry Clinic Area of the University of Seville. The data from this exploration were used to establish that there existed rearfoot hyperpronation and mild to moderate HV according to the classification of Kelikian.16 For all the participants, a weightbearing dorsoplantar X-ray was taken of both feet together, with the X-ray tube at one metre from the feet and inclined at 15 degrees from the vertical.18, 19 The apparatus used was a Sedecal SPS HF-4.0® portable X-ray unit with a collimator. Kodak® Point of Care CR Cassette® chassis were used, equipped with a flexible GP phosphor screen of 24×30 cm. The operating parameters were 45 kV and four mA/sec, as recommended by the manufacturer. Each subject wore a lead apron to shield the rest of the body from radiation. A Kodak Point of Care 140® digital radiology device with Kodak Acquisition Software® was used for the acquisition and transmission of DICOM data, elements, and images. With this set-up, it is obtained a digital radiographic image which can subsequently be exported to the AutoCAD® computer program (AutoCAD 2006; Autodesk Inc, San Rafael, California) to perform the measurements. X-ray measurements using this procedure have been described in previous works.18, 20 Measurements were made by a single observer (MR) in order to reduce the error due to variability in the measurements.21 Fabrication of the foot orthoses For each participant in the experimental group, a mold of the foot was obtained with phenolic foam with the subtalar joint placed in neutral position. The patient's foot was manipulated before being introduced into the phenolic foam to place the subtalar joint in the neutral position and the forefoot plantar plane parallel to the floor. The negative molds of phenolic foam were filled with liquid plaster to obtain a positive mold of the foot on which to make the foot orthosis. Foot orthoses were made with polypropylene of three-mm thickness from the heel to just behind the metatarsal heads, and three-mm thick polyethylene foam posting of 45 shore A hardness on the distal part (Figure 3). The positive plaster cast was placed into a vacuum with the plantar surface upwards. A 3-mm thick polypropylene sheet was heated up to 180 degrees, until it became transparent (3-4 minutes), for vacuum press forming the orthosis. The 3-mm thick polyethylene foam sheet was heated and placed to the upper surface of the positive cast just before the polypropylene, so that both materials got adhered by heat and pressure. Some marks were painted on the orthosis in order to remove the spare material. These marks were the following: a calcaneal line parallel to the dorsal surface of the positive cast and 10-15 milimeters above the support surface level; one point just below the navicular tuberosity, representing the maximum height of the orthosis on the medial side; and a distal line joining the points just proximal to the metatarsal heads and ending at the proximal edges of the first and fifth metatarsal heads. The spare material was REFERENCES 1. Ferrari J. Bunions. Clin Evid (Online) 2009;pii:1112. 2. Mann RA, Coughlin MJ. Hallux valgus - etiology, anatomy, treatment and surgical considerations. Clin Orthop Relat Res 1981; 157:31-41. 3. du Plessis M, Zipfel B, Brantingham JW, Parkin-Smith GF, Birdsey P, Globe G, et al. Manual and manipulative therapy compared to night splint for symptomatic hallux abducto valgus: An exploratory randomised clinical trial. Foot (Edinb) 2011;21:71-78. 4. 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