Pathologic Disorders of the Foot in Professional Female Flamenco Dancers

Abstract

Background: The foot is the main element of artistic creation in flamenco dancing. At the professional level, the foot undergoes high musculoskeletal demands, predisposing the development of podiatric pathologic disorders in this group. The principal objective of this study was to determine the most common foot lesions in professional female flamenco dancers. Methods: In a cross-sectional observational study of 44 female professional flamenco dancers, the participants completed a short questionnaire about their demographic features, number of hours danced per week, and years of professional activity. Any foot lesions presented by the participant were also recorded. Results: Some type of pathologic foot condition was noted in 75% of the women, with a particularly high prevalence of hallux abducto valgus (61.4%), hypermobility of the first ray (43.2%), claw toe (40.9%), and varus fifth toe (37.5%) compared with the general population. No significant differences in the presence of pathologic disorders of the foot were found according to the time dedicated to dance or the years of professional activity. Conclusions: Female flamenco dancers in this study had a high prevalence of podiatric medical problems: some kind of pathologic abnormality of the foot was present in 75% of the participants. Hallux abducto valgus, claw toe, and hypermobility of the first ray were the most common pathologic disorders observed.

The foot is both a musical instrument and the main element of artistic creation in flamenco dancing. At the professional level, this activity makes musculoskeletal demands comparable with those of some high-performance sports [1]. During a flamenco performance, a dancer makes an average of 240 zapateados (sharp beats on the floor with some part of the shoe) per minute and an average of 1,400 zapateados throughout a standard dance [2]. This may be why there is a high prevalence of pathologic disorders of the foot in this population [3,4,5].

There are three elements of flamenco dancing that are predisposing factors for certain alterations, pathologic abnormalities, or problems of the foot: the technical gesture (the flamenco zapateado), the specific footwear, and the floor surface. The zapateado is an important component of this type of dance. It involves a strong impact of the foot against the floor with the toes, heel, or metatarsal area, depending on the type of zapateado. The zapateado speeds up during a performance and is perfectly coordinated with the beat set for each style [2,6]. The specific shoe is stiff soled, with metallic studs in the heel and toe to enhance the sound during percussion. For female flamenco dancers, this shoe has a heel height of 4 to 7.5 cm [7,8].

In most cases, the flooring on which the dancer performs does not have the appropriate properties to minimize impact and prevent injury. The dancer must be prepared to train or act on asphalt, tile, glazed ceramic, marble, improvised plywood stages on metal structures, oak floors, dance floors, or specific surfaces commercialized as being ideal sound platforms or professional acoustic flooring. Because there is no specific regulation, dance and flamenco floor manufacturers usually follow the European standard DIN 18032, Part II (elasticity, creep resistance, and soil homogeneity) [9].

Flamenco dancing lesions and pathologic abnormalities include, among others, spinal pain, lower-limb joint lesions, foot lesions, and abnormalities deriving from or exacerbated by the specific characteristic footwear, inadequate flooring, and the art form's technical gestures [5,7,10,11,12]. The principal objective of the present study was to determine the most common pathologic foot disorders in professional female flamenco dancers.

Methods

The study, with a cross-sectional and observational design [13], was performed between October 1, 2009, and January 31, 2012. The sample comprised 44 female professional flamenco dancers, either independent or associated with flamenco dance academies in Andalusia, Spain. Each participant was informed of the study objectives and the method of measurement of the variables, and written consent was obtained. The study was approved by the research ethics committee of the University of Seville (Seville, Spain).

The required inclusion criteria were professional female flamenco dancers who worked independently or were associated with dance institutions and academies, adults (age >18 years), professionally active at the time of the study, and having performed their flamenco dancing activity for a minimum of 20 hours a week for at least the past 12 months. The exclusion criterion was having undergone leg or foot osteoarticular surgery in the past 3 years.

The women completed a questionnaire regarding their demographic characteristics, podiatric medical record, type of footwear used (whether the light boot style of flamenco [botín] or the raised-heel flamenco shoe), number of hours per week dedicated to flamenco dancing, and years of professional activity. We measured the height of the dance shoe heel in centimeters, including the heelpiece (ie, the layer of material in contact with the floor). The angles, in degrees, of ankle dorsiflexion with the knee in flexion and extension were determined using a two-arm universal goniometer. With visual and manual examination, we determined whether the dancers had any pathologic disorders of the foot, noting in particular hallux limitus/rigidus, hallux abducto valgus, Taylor's bunion, claw toe, fifth toe abducto varus, pathologic disorders of the nail, hypermobility of the first ray, and the relaxed position of the calcaneus in support, pes planus, or pes cavus [14]. Hallux limitus/rigidus was determined by measuring the mobility of the first metatarsophalangeal joint with the two-arm universal goniometer, taking as normal an extension of 65° or more [14]. Hallux abducto valgus was established using the Manchester Scale following the procedure described by Garrow et al [15]. This scale is a clinical tool consisting of photographs of feet with four levels of hallux valgus: none, mild, moderate, and severe. The rearfoot was classified as valgus when the relaxed angle of the calcaneus in support was greater than 5° valgus, as varus when this angle was less than 2° varus, and as normal otherwise [14,16,17]. Pes planus or cavus was established from a study of the footprint using a software program (Footchecker software, version 4.0; Loran Engineering Ltd, Castel Maggiore, Italy).

The software package CTM version 1.1 (Franz Faul, Universitat 68 Kiel, Kiel, Germany) was used to determine the required sample size, assuming that there may be approximately 3,000 professional female flamenco dancers worldwide [8,10], an error (epsilon) of 2.2%, an initial estimate of 0.5 (50%), and a 95% confidence level. The result was a minimum number of participants of 39. The final study sample consisted of 44 female flamenco dancers (88 feet).

Data analysis was performed using a software package (SPSS v.23 for Windows; IBM Corp, Armonk, New York). For the descriptive statistics, the mean ± SD of the quantitative variables and the frequency and percentage occurrence of the different foot pathologic disorders were calculated. Normality of the distribution of the quantitative variables was checked using the Shapiro-Wilk test. Comparisons were made using parametric tests (the Student t test for independent samples) for the normally distributed variables and nonparametric tests (the Wilcoxon and Mann-Whitney U tests) otherwise. The comparisons made were ankle dorsiflexion with the knee in extended and flexed positions, ankle dorsiflexion between the left and right feet in both positions of the knee, height of the shoe heel between participants with and without hallux abducto valgus and between those with and without claw toe, and the weekly hours spent dancing and the years of professional activity between those with and without some type of foot lesion. We also used the Pearson test to analyze the correlation between the years of professional activity and the degree of ankle dorsiflexion.

Results

The data correspond to the 88 feet of 44 dancers aged 18 to 57 years old (mean ± SD age, 28.93 ± 8.61 years). The mean ± SD time spent dancing was 30.88 ± 8.91 hours per week (range, 20–56 hours per week), and the mean ± SD history of professional activity was 14.57 ± 10.84 years (range, 1–43 years).

Only nine of the dancers (20.5%) had ever attended a podiatric medical consultation. They all used heeled flamenco shoes, with a heel height of 4.5 to 7 cm. The 6-cm heel (including the heelpiece stud) was the most frequent, used by 47.7% of participants.

The mean ankle dorsiflexion of the study group with the knee extended and the subtalar joint in the neutral position was 10.88°, whereas with the knee flexed it was 19.68°. The mean difference between the two measurements was 8.8°, significant (P < .001) as determined by the Wilcoxon test. There were no significant differences between these measurements depending on laterality (mean ± SD right ankle dorsiflexion with the knee extended, 10.91° ± 6.47°; left ankle dorsiflexion with the knee extended, 10.84° ± 5.92° [P = .878]; right ankle dorsiflexion with the knee flexed, 19.43° ± 6.53°; left ankle dorsiflexion with the knee flexed, 19.93° ± 5.27° [P = .482]).

Most of the women (33; 75%) had some kind of pathologic disorder of the foot. The prevalence of deformities in the first metatarsophalangeal segment were as follows: hallux abducto valgus, 61.4%; hallux limitus/rigidus, 6.8%; and first-ray hypermobility, 43.2%. The cases of hallux abducto valgus were all classified according to the Manchester Scale as being type B.

The prevalences of Taylor's bunion, fifth toe abducto varus, and claw toe were 13.5%, 37.5%, and 40.9%, respectively. There was an association of hallux abducto valgus with claw toe in 27.27% of the participants; 44.44% of the feet with hallux abducto valgus also presented claw toe. Hallux abducto valgus and Taylor's bunion were simultaneously present in 13.63% of the participants, with all of the dancers presenting Taylor's bunion associated with hallux abducto valgus.

Regarding rearfoot alterations in the frontal plane, data showed that 55.55% of the rearfoot valgus presented hallux abducto valgus and 33.33% presented claw toe (Table 1). Regarding nail alterations, the prevalence of onychodystrophy was 20.5%, of onychomycosis was 11.4%, and of onychocryptosis was 9.1%.

Table 1. Rearfoot Deformities in the Frontal Plane According to Footprint Type.

Table 1. Rearfoot Deformities in the Frontal Plane According to Footprint Type.

There were no significant differences in mean ± SD heel height between dancers with and without hallux abducto valgus (6.00 ± 0.49 cm and 5.93 ± 0.73 cm, respectively; P = .920) and between dancers with and without claw toe (5.98 ± 0.57 cm and 5.94 ± 0.70 cm, respectively; P = .971).

Neither were there any significant differences in the mean ± SD hours of dedication to flamenco dancing between those with and without some type of foot lesion (31.26 ± 9.40 h/wk and 28.50 ± 4.21 h/wk, respectively; P = .520) or years of professional activity between those with and without some type of foot lesion (14.25 ± 10.55 years and 16.67 ± 12.86 years, respectively; P = .808).

We also checked whether the dancer's years of professional activity had some relationship with the observed angle of ankle dorsiflexion. Although we did find a statistically significant relationship in the case of ankle dorsiflexion with the knee flexed, the corresponding Pearson coefficient showed a weak correlation (correlation between knee-extended ankle dorsiflexion and years of professional activity: r = 0.007, P = .947; and between knee-flexed ankle dorsiflexion and years of professional activity: r = −0.292, P = .006).

Discussion

The present results revealed a high prevalence of pathologic abnormalities of the foot in this group of flamenco dancers. Various studies have related foot problems to flamenco dancing [5,18,19] and other forms of dance [20,21,22,23,24,25].

Indeed, in 2008 the Spanish National Institute of Health and Safety at Work declared flamenco art performers to be a high-risk group [26], noting their mostly poor working conditions and their lack of appropriate education, information, and awareness concerning health issues in general and the prevention and avoidance of occupational hazards in particular. Given the overriding importance of the lower limbs in flamenco, one has to consider flamenco dancers as an at-risk group highly susceptible to foot lesions.

In this study population, the mean ankle dorsiflexion with the knee extended and the subtalar joint in neutral position was 10.88° and with the knee flexed was 19.68°. The mean difference between the two measurements was 8.8° and was statistically significant. There were no significant differences between the two measurements according to laterality. These data differ from those reported by Pedersen and Wilmerding [18]. in a flamenco dancer study in which there was a large difference according to laterality in ankle dorsiflexion with the knee extended and the subtalar joint in neutral position: 6.57° for the right foot and 12.87° for the left. Although the relationship that we found between the years of professional activity and the angle of ankle dorsiflexion with the knee flexed was statistically significant, the value of the Pearson correlation coefficient showed it to be no more than weak.

Of the 44 dancers studied, 33 (75%) presented some foot abnormality. We found no significant connection between the weekly time committed to flamenco dancing and the presence of a podiatric medical condition. Cho et al [22] reported a study of the prevalence of pathologic conditions in 42 professional and amateur break-dancers, of whom 28.6% had foot lesions. The study by Steinberg et al [25] of 1,336 dancers of different disciplines found that tendinitis in the foot and ankle region was the most common pathologic condition (in 41% of the sample) in the 8- to 9-year-old group and the second most common (in 22% of the sample) in the 14- to 16-year-old group.

In the present sample, the prevalence of the hallux abducto valgus deformity was 61.4%. The literature in general shows dancing to be a factor that increases the prevalence of hallux abducto valgus [23,24,25,26,27]. The present result is similar to that reported for a group of ten flamenco dancers by Bejjani et al [3], although in a study of retired ballet dancers, Einarsdóttir et al [28] found no increase in the hallux abducto valgus angle compared with a population that did not practice this activity. The percentage obtained in this present study was greater than the 40% obtained in a previous study performed by the same research group but on a smaller sample [12].

The prevalence of the hallux rigidus/limitus deformity in the present study population was 6.8%. In a previous smaller-scale study [12], the prevalence was 40%. Some authors have related the presence of this pathologic disorder to dance [21,29]. The prevalences in dancers of hypermobility of the first ray and Taylor's bunion were 43.2% and 61.4%, respectively. In the work by Bejjani et al [3], the latter condition was present in 20% of their sample.

Claw toe was present in 43.2% of the study population, and fifth toe abducto varus in 6.8%. In their systematic literature review of dance shoes [23], two articles on flamenco were considered, concluding that the footwear was, indeed, a risk factor for claw toe, a conclusion that reflected the findings of other authors [20]. In the present study, however, the presence of hallux valgus or claw toe was unrelated to the height of the heels, with no significant differences in heel height of individuals who had hallux valgus and those who did not or between those who had claw toe and those who did not (P = .621 and P = .757, respectively). In their sample of ten female flamenco dancers, Bejjani et al [3] reported a 20% prevalence of claw toe. In the previous study by our group, we found a prevalence of claw toe of 27.5% and the same frequency of fifth toe abducto varus [12].

Regarding the presence of alterations of the rearfoot in the frontal plane, we found 20.5% rearfoot valgus and 2.3% rearfoot varus. Bejjani et al [3] reported 30% valgus feet in their sample of flamenco dancers. Again, 29.5% of the present sample had pes cavus and 11.4% had pes planus; the values reported in the literature are 50% and 20%, respectively. Some authors consider one consequence of the practice of dance to be the development of pes planus [20].

We found that 20.5% of the sample had onychodystrophy, 11.4% had onychomycosis, and 9.1% had onychocryptosis (ingrown nails). Sammarco and Miller [20] described onycholysis and subungual hematomas as being frequent lesions in the dancer's forefoot. Howse [21] reported an increased likelihood of nail growth problems and subungual exostosis in dancers. Rodríguez and Sanz [30] described a study of pathologic foot disorders in 159 female dancers, finding the prevalence of onychocryptosis to be 30% and of onychomycosis to be 15%. Quer and Pérez [5] described a study of the pathologic foot disorders of 174 adult male and female flamenco dancers. They found a prevalence of nail affectation that was similar to ours (20.7%) and specified that 11.5% of the cases were subungual hematomas and that 5.2% corresponded to infections. Note, however, that their study sample was not restricted to professional dancers. In the earlier, smaller-scale study published by our group, there was a prevalence of 11% of onychopathies, of which 75% were onychodystrophy and 25% were onychocryptosis [12,23]. For that reason, we had also considered dancers' footwear as a risk factor for nail problems.

In the female dancers in our study, we observed a variety of foot deformities, especially hallux abducto valgus (61.4%), first-ray hypermobility (43.2%), claw toe (40.9%), and varus fifth toe (37.5%). The weekly time committed to flamenco dancing did not influence the occurrence of podiatric pathologic abnormalities. Neither was heel height related to the presence of hallux abducto valgus or claw toe.

For flamenco dancers, personal treatment and suitable shoes, which take into account the morphologic and pathologic features of the foot, the technical gesture, and the floor surface, are essential. This research has helped us develop new insoles and specific flamenco shoes.

Conclusions

The female flamenco dancers who participated in this study had a high prevalence (75%) of podiatric medical problems. They had an ankle range of motion of approximately 10° with the knee extended, and a significant but weak relationship was observed between ankle range of motion and a dancer's years of professional activity. No significant differences were observed in the weekly hours of dedication to flamenco dancing or in the years of professional activity between dancers with and without some type of foot lesion.