Effects of global postural reeducation on postural control, dynamic balance, and ankle range of motion in patients with hallux abducto valgus. A randomized controlled trial

Hallux abducto valgus (HAV) is a common musculoskeletal disorder that has been addressed surgically. Nevertheless, the manual therapy approach may play an important role in the management of this condition. The present study aimed to determine the effectiveness of global postural reeducation (GPR) in subjects with symptomatic mild to moderate HAV in static postural control, dynamic stability, and ankle dorsiflexion range of motion (DFROM). A total of 80 patients with mild to moderate symptomatic HAV were allocated to the intervention group (GPR) or control group (CG) (no treatment) for 8 weeks. Outcome measures were assessed at baseline at 4 and 8 weeks including static postural control (Romberg test), dynamic balance (Star Excursion Balance Test [SEBT]), and ankle DFROM (Weight‐Bearing Lunge Test [WBLT]). No improvements were observed at 4 weeks, but there were improvements at 8 weeks in: static postural control mediolateral displacement (X) of center of pressure (CoP) in both eyes open (EO) and eyes closed (EC): XEO (t(36) = 2.892, p = .006, d = 0.67); XEC (t(68) = 2.280, p = .026, d = 054); and velocity (V) of CoP displacement: VEO (t(68) = 2.380, p = .020, d = 0.57); VEC (t(36) = 2.057, p = .047, d = 0.37). It were also improvements in: WBLT (t(36) = −2.869, p = .007, d = 0.54) and SEBT at three directions (anterior, ANT; posteromedial, PM; and posterolateral, PL): SEBT.ANT (t(36) = −2.292, p = .028, d = 0.23); SEBT.PM (t(36) = −4.075, p < .001, d = 0.43); SEBT.PL (t(62) = −3.506, p = .001, d = 0.34). The present study showed that GPR compared to the CG might be effective in enhancing ankle function including postural control, dynamic balance, and DFROM.


| INTRODUCTION
Hallux abducto valgus (HAV) is defined as a static subluxation of the first metatarsophalangeal joint with lateral deviation of the great toe and medial deviation of the first metatarsal. 1 It is the most frequent foot pathology with a prevalence of 30% in women and 13% in men and it tends to increase with age. 1  The etiology is unknown, but it has been related to the pronated foot, metatarsophalangeal osteoarthritis, intrinsic foot musculature strength deficits, 4 genetics 5 big toe pain, 4,5 and the use of some kind of shoes including heels or narrow shoes. 6 HAV may lead to pain, 7 postural control alteration, 8 increased risk of falls, 7,9 and associated risk of foot injury due to plantar pressure alteration resulting from the altered morphology 7,8,10 and biomechanics. 7 Foot joints, muscles, and plantar mechanoreceptors are very important in feedback and feedforward mechanisms so, if they are altered, proprioception and postural control could be negatively affected. 8,10 If there are alterations of gait and plantar pressure peaks, load distribution of the foot can be modified, and this is related to metatarsalgia, HAV, or risk of falls. 7,9 When HAV deformity exists, postural stability decreases, specially mediolateral stability 8 which could also be related to musculature strength deficits. 4,11,12 Regarding the therapeutic approach of patients with HAV, the most common treatment is surgery. 13 Current literature includes joint mobilizations, exercise, ice, and orthopedics implements that involve toes separator and night splints at the early stages of the pathology but until recently this is the first study addressing the effectiveness of manual therapy approach on this pathology. 13,14 global postural reeducation (GPR) method consists of a combination of manual therapy and therapeutic exercise in which a pretension of the targeted myofascial chain is maintained, while the participant holds a specific treatment posture isometrically. 15,16 GPR is effective in the management of several musculoskeletal disorders including temporomandibular dysfunction, urinary incontinence, and spine injuries. 16,17 There was no previous research addressing the effectiveness of this method in subjects with HAV, but it may be helpful for the conservative management of this condition taking into account the aforementioned literature. Therefore, the present study aimed to determine the effectiveness of GPR in subjects with symptomatic mild to moderate HAV in static postural control, dynamic stability, and ankle dorsiflexion range of motion (DFROM).

| Design
This study was a Randomized Controlled Trial, with an experimental group (EG) consisted of GPR and a CG that received no intervention.
Patients were told to continue with their usual daily life activities. The study (NCT04468555) was approved by the Human Ethics Committee of the University of Jaén and conducted following the Declaration of Helsinki, good clinical practices, and applicable laws and regulations and meets the CONSORT guidelines standards. 12 Informed consent was obtained for all participants who accepted to be enrolled in the study.

| Outcome measures
The assessment was performed at baseline and after 4 and 8 weeks by an independent investigator. Sociodemographic and baseline data are described in Table 1.

| Static postural control
Stabilometric parameters were measured on a bipodal stance with a stabilometric platform of pressure resistive sensors (Sensor Medica).
The Romberg test was performed in eyes open (EO) and eyes closed (EC) conditions. In this test, participants should be in a barefoot bipodal stance with a 2 cm separation between heels and an angle of 30°between the feet. 18 Each measure consisted of 30 s of holding the stand position, following by 1 min of rest between EO and EC tests and a sampling frequency of 40 Hz. 19 The assessed parameters were related to the center of pressure (CoP) in both EO and EC conditions: mediolateral (X) and anteroposterior (Y) mean displacements of the CoP (mm), and velocity of CoP movement (v, in mm/s). 19 Smaller scores indicate better postural stability. 20

| Dynamic balance
was examined with the Star Excursion Balance Test (SEBT). It was assessed the three reach directions of the SEBT simplified version because it has been reported to be a reliable tool for measuring dynamic balance in people with lower-limb dysfunction with excellent test-retest reliability. 21 The test is performed while standing on a barefoot single-leg position with the affected limb positioned in the middle of the SEBT grid while the participant reaches the longest distance possible for all the three directions as described by Gribble et al. 21 Low scores are related to an increased risk of injury in the lower limb. 21 This test has been widely employed for monitoring the effectiveness of different physiotherapy approaches in dynamic balance. 21,22 ESTEPA-GALLEGO ET AL. | 1437

| Ankle DFROM
The Ankle DFROM was assessed with the Weight-Bearing Lunge Test (WBLT), which involves the participant standing on a tandem stance while performing a forward lunge. 23 During this task, the involved foot remained firmly planted on the ground as the tibia progressed over the talus into maximum ankle DFROM and the maximum distance from the great toe to the wall is measured. 23 While performing the WBLT, the clinician controlled the position of the feet, the knees, and the pelvis to check the correct execution. 23 It has been reported that WBLT is a valid test and has good reliability and reproducibility, being widely employed for monitoring change over time in manual therapy, including plantar massage and joint mobilization for subjects with CAI and sport-based intervention. 24,25 Previous research has shown that WBLT is correlated with dynamic postural control measures. 26

| Participants and allocation
Participants were allocated by an independent investigator who used a random number generator and sealed the treatment sequence in opaque envelopes that were opened before performing the first intervention. As there is no consensus for eligibility criteria in manual therapy approaches for HAV, our participation eligibility criteria were F I G U R E 1 Flow diagram according to CONSORT. 28 [Color figure can be viewed at wileyonlinelibrary.com] consistent with Abdalbary et al., 14 and du Plessis et al., 27 Inclusion criteria for participants were (A) having mild to moderate HAV deformity evaluated with MS; 6 (B) 18-65 years; (C) painful HAV. If there were bilateral HAV, we included in the study the most symptomatic and/or the one comprised between mild to moderate. 14,27 Exclusion criteria for participants included (A) surgeries in the lower limbs; (B) pathologic foot deformities not related to HAV; (C) to have been receiving physiotherapy treatment for HAV; (D) to suffer systemic diseases as deposit sickness or rheumatoid arthritis; (E) severe osteoarthritis; (F) to suffer any disease that affects the sensory-motor function of the foot different from the HAV; (G) to suffer any fracture or disease that was still affecting the foot; (H) patients with antiinflammatory drugs where manual therapy was contraindicated. 14,27 After participant screening, those who accept to take part in the study were randomly assigned to the control (no treatment) or experimental (GPR) group. Participants in both groups were instructed for continuing with their habitual daily life activities. Participant demographic information can be found in Table 1.

| Intervention
Individuals allocated to CG received no intervention, and those assigned to EG received three sessions based on the GPR methodology. Figure 1 shows the flow diagram according to the Consort statement. 12 Participants allocated to the intervention group received a treatment consisted of a GPR approach divided into 3 sessions and performed with a frequency of 1 session per week for 3 weeks. The sessions were performed individually, with an approximate duration of 40 min and all of them were assessed by the same physiotherapist. In the GPR methodology, there are several postures described for performing the treatment in which the subject has to actively participate. 15,16 Each session was divided into 5 parts, according to the methodology, without rest, progressing in the posture. 15 In this progression, postural demands increased during task execution with greater activation of intrinsic foot muscles. 29 A more detailed description can be found in  Table 3 shows the results of all outcome measures.

| RESULTS
The results showed no significant main effects in XEO, XEC, YEO,  The sole is involved in CNS processes including postural control and balance due to the high density of cutaneous mechanoreceptors that influence proprioceptive and exteroceptive information of the body position and the support state. 10 The function of mechanoreceptors could change due to biomechanical alterations in HAV conditions. 7,8,10 This may lead to poor postural control 8 decreased balance, 10 lower physical activity, 28 risk of falls 7,9,28 risk of injury, 16,28 and limited mobility and ambulation. 28 Literature also supports that plantar, joint,  33 which could be related to the 5. Walk maintaining the alignment of the first ray, an elevated medial longitudinal arch and dorsiflexion of the first proximal metatarsophalangeal joint. We performed this task during 5′. This is a dynamic task for integrate the results obtained after the previous work in the CNS.
Abbreviation: CNS, central nervous system. neurophysiological mechanisms underlying the stimulation of plantar cutaneous receptors. 10,36 These findings agree with the results obtained in our study where GPR intervention combines plantar and joint receptor stimulation resulting in superior results due to this combination. 10,36 Concerning muscle activation role in postural control, Lynn et al., 38 did not found differences between mediolateral oscillations in healthy individuals when performing training of intrinsic musculature of the foot. This is in contrast to the obtained results after GPR intervention and could be explained because during our intervention patients activate intrinsic and extrinsic muscles of the foot which has been deemed to play an important role in postural control. 11

| Manual therapy in HAV and dynamic balance
In presence of HAV, there are strength deficits that are related to balance impairments. 4,11 The present study shows improvements in dynamic balance at the 3 directions of SEBT at 8 weeks. These positive results could be due to neurophysiological mechanisms underlying the manual stimulation of the plantar and joint receptors that were described before 10,24,25,36 and the combination with muscle activation. 37,38 Literature reports that rigid tape improves dynamic balance in people with HAV deformity. 20,39 There is also evidence that supports that plantar massage and joint mobilizations improve single limb dynamic balance in patients with CAI. 22,31 Our findings in dynamic balance agree with the aforementioned results and it could be because both manual and taping interventions could enhance proprioceptive information of the cutaneous and joint receptors. 10,20,31,39 Previous investigators have also shown improvements in dynamic balance when training the intrinsic foot muscles in the healthy population, 38 individuals with excessively pronated feet 32 and subjects with CAI, 37 which agree with the results of our study due to the isometric activations of the foot core. Ankle passive joint mobilizations for decreased ankle DFROM has been widely explored in patients with CAI as well as Mobilizations With Movement with positive findings 22,31 These results agree with the obtained results after GPR intervention. The active component of GPR may play an important role in the integration of muscle activation and related subjective instability feeling due to ankle instability in patients with HAV. 22

| CONCLUSION
The obtained results suggest that GPR method is effective for improving mild to moderate HAV results in postural control parameters as mediolateral displacements and velocity of CoP displacement. It also improves dynamic balance in all three directions and ankle DFROM.

| Limitations and further investigation
The principal limitation of this study is the short and midterm evaluation. Future studies should examine the long-term results of the GPR treatment to determine the maintenance of the improvement over time.
However, future studies should evaluate psychological, pain and quality of life. This patology could affect patients self-concept and quality of life and should be adressed in a biopsicisocial model. 40