The windlass mechanism, first described by John Hicks in 1954, defines the anatomical and biomechanical relationship between the hallux and the plantar fascia. Hallux valgus (HV) and plantar fasciitis are the most common foot disorders, and, to date, no study has evaluated the relationship between these disorders. The purpose of this study was to determine the incidence of and factors associated with plantar fasciitis in patients with HV deformity.
In this prospective observational study, 486 patients with HV were divided into three groups according to stage of HV deformity. Patient sex, age, and body mass index were recorded. Presence of accompanying plantar fasciitis and heel spur was investigated by physical and radiographic examination. First metatarsophalangeal joint dorsiflexion of the affected side was measured. Patients with or without plantar fasciitis were also compared to evaluate factors associated with plantar fasciitis.
Mean age and body mass index of the patients were significantly different among the three HV groups. The incidence of plantar fasciitis and heel spur significantly increased in correlation with the severity of HV deformity. Increased age and HV stage and decreased first metatarsophalangeal joint dorsiflexion were significantly associated with presence of plantar fasciitis in HV.
In this study, the incidence of plantar fasciitis was significantly increased in correlation with the severity of HV deformity. Significant association was found between plantar fasciitis and HV, which are anatomically and biomechanically related to each other by the windlass mechanism.
It has been reported that approximately 10% of adults experience plantar heel pain in their lifetime.1 Because plantar heel pain is one of the most common disorders of the foot, several studies have been published to explain its etiologic factors.2 The windlass mechanism, defined as the support of plantar fascia during weightbearing, was first described by John Hicks in 1954.3 A windlass, which is used for lifting heavy objects, is a historical device that consists of a horizontal cylinder (drum) turned by a handle and a winding cable or rope attached to a weight. According to Hicks, the head of the first metatarsal bone was the drum of the windlass and the handle that does the winding was the toe, with the rope mechanism constructed as plantar fascia (Fig. 1).3 Later, Fuller4 also described the mechanical model of the mechanism and its relations with hallux limitus, hallux valgus (HV), and plantar fasciitis. In another study investigating the pathogenesis of HV deformity, Perera et al5 reported an increase in HV deformity due to tightening of the plantar fascia.
We hypothesized that HV deformity may result in secondary plantar fasciitis by the mechanical relation of the plantar fascia and hallux through the windlass mechanism. Therefore, the main purposes of the present study were to determine the incidence of plantar fasciitis in patients with HV deformity and to evaluate the factors associated with plantar fasciitis in patients with HV.
After approval from the ethical review board, this cross-sectional, observational, clinical study was performed simultaneously at the orthopedic surgery departments of two medical centers. Between January 1, 2015, and December 31, 2016, patients who were admitted to our departments and diagnosed as having HV were included in this study. Patients who were skeletally immature, had a history of foot surgery, had other abnormalities of the foot (eg, hallux limitus), or had foot deformities secondary to neuromuscular disorders or previous trauma were excluded from the study. After exclusion, 476 patients with a diagnosis of HV were included in this study and investigated for the incidence of plantar fasciitis.
The sex, age, and body mass index (BMI; the weight in kilograms divided by the square of the height in meters) were recorded for all of the patients. Physical examinations were performed by two different physicians from the two centers. The diagnosis of plantar fasciitis was established in accordance with current clinical guidelines.6,7 The criteria for the diagnosis of plantar fasciitis were as follows: 1) presence of pain under the plantar surface of the heel on weightbearing after a long period of sitting or at first step in the morning, 2) presence of plantar heel pain after prolonged weightbearing activity, 3) tenderness over the medial plantar aspect of the heel, 4) pain and tenderness over the plantar fascia while applying the windlass test, and 5) negative tarsal tunnel test results. To distinguish heel pain secondary to plantar fasciitis from other potential factors leading to heel pain, patients had to have all five of the criteria mentioned. First metatarsophalangeal joint passive dorsiflexion was measured by a standard goniometer. Weightbearing anteroposterior and lateral radiographs of both feet were obtained for all of the patients routinely. Radiologic evaluation of HV deformity was performed using measurement of the angle between the first metatarsal bone axis and the proximal phalangeal axis (HV angle) as well as the first-second intermetatarsal angle on anteroposterior radiographs. The presence of heel spur was also investigated through radiographs. Radiographic measurements were performed by one physician, who did not perform the physical examinations. Patients were divided into three groups—mild, moderate, and severe HV stages—according to the classification of Mann and Coughlin (Table 1).8
The sex distributions, ages, BMIs, and first metatarsophalangeal joint dorsiflexion values of the three groups were compared by the one-way analysis of variance test. Presence of heel spur and plantar fasciitis in the three groups were compared by the χ2 test. A second analysis was performed by dividing patients into two groups—healthy group (absence of plantar fasciitis) and plantar fasciitis group—to compare independent variables. The comparison between the two groups was performed by using the t test for continuous variables and the χ2 test for categorical variables. P values less than 0.05 were considered statistically significant.
The demographic data and the distribution of the patients are given in Table 2. According to the statistical analysis, the three HV groups were similar in sex; however, significant differences were observed in the mean age (P < .001) and BMI (P = .028) of the patients. The incidence rates of plantar fasciitis (P < .001) and heel spur (P < .001) were significantly increased as the stage of HV deformity increased (Fig. 2). Mean ± SD first metatarsophalangeal joint dorsiflexion was 44.4° ± 3.1° in the mild HV group, 44.1° ± 2.6° in the moderate HV group, and 39.7° ± 4.7° in the severe HV group; this value was significantly lower in the severe HV group compared with the other groups (P < .001).
According to the results of the comparison between patients with or without plantar fasciitis, the mean age (P < .001) and HV stage (P < .001) were significantly higher in the plantar fasciitis group (Table 3). In addition, patients' mean first metatarsophalangeal joint dorsiflexion was significantly lower in the plantar fasciitis group (P < .001).
Hallux valgus, which can cause pain and functional limitation, is a common acquired foot disorder.9 In the pathophysiology of this deformity, the windlass mechanism may have a potentially important role owing to its effects on first metatarsophalangeal joint kinematics.5,10 According to the windlass mechanism, when the toe moves to dorsiflexion during the push-off phase of gait it depresses the metatarsal head and tightens the plantar fascia. The tightening of the plantar fascia raises the medial longitudinal arch and supports the body weight.3,4 In HV deformity, this mechanism may be disrupted because of progressive subluxation of the metatarsal head. On the other hand, the tightening of plantar fascia, which passes medially from the first metatarsophalangeal joint in an oblique route, may lead to increased deformity in HV.11 In this study, we hypothesized that HV and plantar fasciitis, which are among the most common disorders of the foot, may both affect and aggravate each other by the windlass mechanism. According to the present results in a large study population, the incidence rates of plantar fasciitis and heel spur were significantly increased in correlation with the severity of HV deformity.
In a systematic review, Irving et al12 reported that increased age and weight as well as decreased ankle and toe dorsiflexion were associated with chronic plantar heel pain. In another study evaluating ultrasonographic measurements of plantar fascia and plantar intrinsic muscles in different stages of HV, Lobo et al13 reported a reduction in the cross-sectional area of intrinsic plantar muscles (flexor hallucis brevis and abductor hallucis) and an increase in the thickness of plantar fascia. To date, no study can be found reporting the association between plantar fasciitis and HV. On the other hand, several authors reported the relationship between plantar fasciitis and hallux limitus in the literature.14,15 Creighton et al14 reported the relationship between plantar fasciitis and the decreased dorsiflexion of the hallux. Aranda and Munuera15 mentioned that patients with plantar fasciitis had limited first metatarsophalangeal joint dorsiflexion compared compared with a control group. However, Allen and Gross16 reported no significant association between first metatarsophalangeal joint dorsiflexion and plantar fasciitis. In the present study, a significant decrease in metatarsophalangeal joint dorsiflexion was detected as the stage of HV deformity increased. In addition, the dorsiflexion range of the first metatarsophalangeal joint was significantly lower in patients with plantar fasciitis than in those without plantar fasciitis.
The increased prevalence of foot problems in obese and/or older patients is well established in the literature.17,18 Pita-Fernandez et al19 also reported a high prevalence of podiatric problems with increased age and female sex. In a study that evaluated ultrasonographic measurement of plantar fascia thickness in 156 adults, Abul et al20 reported that plantar fascia thickness had a positive correlation with age and BMI. In the present study, we also noted that age and BMI were significantly higher in patients with severe HV than in the other groups. In addition, the mean age was significantly higher in patients with plantar fasciitis.
The most important finding of this study was the increased incidence of plantar fasciitis in correlation with the severity HV deformity. When this issue was clinically assessed, the use of orthoses to reduce the overload on the hallux and implementation of stretching and strengthening exercises to prevent tightening of the plantar fascia may decrease the progression of HV deformity as well as the occurrence of plantar fasciitis. In his review, Glasoe21 also recommended strengthening exercises adjunct to orthoses treatment in HV deformity. According to the present results, we recommend that podiatric physicians and physical therapists consider the importance of the windlass mechanism in patients with HV and plantar fasciitis. Treatment of the disrupted mechanism in the early stages of HV deformity can prevent progression of the disease as well as reduce additional symptoms related to accompanying plantar fasciitis.
The main limitation of the study was its cross-sectional design. However, this is the first study in the literature evaluating the relationship between HV and plantar fasciitis in a large cohort. In addition, this study gives valuable information to podiatric physicians about interruption of the windlass mechanism in correlation with the severity of HV. Further well-designed, randomized, prospective studies are needed to achieve a better understanding of the mechanism in relation to these pathologic disorders.
According to the results of this study, the incidence of plantar fasciitis was increased in correlation with the severity of HV deformity. Significant association was found between plantar fasciitis and HV, which were anatomically and biomechanically related to each other by the windlass mechanism. This mechanism, which has an important role in foot function, should be evaluated well by podiatric physicians and physical therapists in clinical practice.
Financial Disclosure: None.
Conflict of Interest: None.