THE INFLUENCE OF HALLUX VALGUS ON PELVIS AND LOWER EXTREMITY MOVEMENT DURING GAIT

BACKGROUND: The hallux and the fi rst metatarsophalangeal joint play a major role in load transmission during walking. OBJECTIVE: The main aim of this study was to investigate diff erences in kinematics of the pelvis and lower extremities during gait by comparing people with hallux valgus (HV) and a control group (CG). METHODS: We compared subjects with asymptomatic bilateral HV (n = 6, 57.8 ± 5.64 years) with those who had CG (n = 11, 50.7 ± 4.41 years). Gait analysis was investigated using an optoelectronic system Vicon MX. The subjects walked at self selected speeds. In total, fi ve trials of each subject were analyzed. The statistical processing was performed by means of the Student t-test. The eff ect size was determined using the ω measure. RESULTS: In people with HV there was a signifi cantly smaller maximum of dorsal fl exion during the stance phase (p < 0.01, ω > 0.06) and a greater maximum of plantar fl exion at the beginning of the stance phase (p < 0.01, ω > 0.06). The maximum of knee extension at the end of the swing phase was signifi cantly greater (p < 0.01, ω > 0.06) in subjects with HV. In the frontal plane, a signifi cantly smaller maximum of hip abduction (p < 0.01, ω > 0.06) during the gait cycle was observed in people with HV. The range of pelvic obliquity (p < 0.01, ω > 0.06) and pelvic rotation (p < 0.01, ω > 0.06) were signifi cantly smaller in people with HV. CONCLUSION: This study demonstrated that HV does not exclusively concern the foot. The valgus deformity of the big toe can negatively infl uence function of the lower extremities and can cause overloading of those segments as well.


INTRODUCTION
Hallux valgus (HV) is a complex, progressive triplanar forefoot deformity. It incorporates a valgus deviation of the big toe, increased varus of the fi rst metatarsal bone and a medial prominence of its head (Lorimer, Neale, & French, 2006). This is related to other foot problems, depending on the cause, duration of symptoms and the degree of deformity. HV deformity usually occurs together with a decrease of the transverse arch, an occurrence of hammer toes, a widening of the forefoot and pressure distribution changes under metatarsal heads, causing a metatarsalgia (Halebian & Gaines, 1983;Torkki, 2004).
HV deformity is related to foot dysfunction and may lead to failure of basal support in the stance phase, shock absorption and load transmission during gait. The structure and function of the foot play the main role in postural dynamics. Stabilization of the fi rst metatarsal is the basic precondition for optimal foot function. In hallux valgus deformity, fi rst ray dynamic stabilization failure and loss of the contact between the fi rst metatarsophalangeal joint surfaces and sesamoid bones is typical (Lorimer et al., 2006). HV is related to functional joint centration failure in terms of postural ontogenesis (Kolář, 2001). Due to a chain failure, one dysfunctioning segment can cause overloading of other segments and change the movement pattern (Kučera, 1994;Vařeka & Vařeková, 2003).
The main aim of this study was to investigate the diff erences in the kinematics of the pelvis and the lower extremities during gait between people with HV and control group.
Using a 3D motion analysis system (Vicon MX, Oxford Metrics Inc., Oxford), movement of the pelvis and lower extremity segments was observed during gait. We used the Plug-In Gait model (7 segments, 16 refl ex markers). The advanced Vicon system with 7 infrared cameras was synchronized with 2 force platforms (Kistler 9286AA, Kistler Instrumente AG Winterthur, Switzerland). It enabled us to detect the phases of the gait cycle.
We carried out a kinesiology examination prior to the actual measurement. The subjects walked at self selected speeds without shoes. After two test trials, ten trials were measured. Five trials of each subject were analyzed -the ankle peaks in the sagittal plane (plantar/ dorsal fl exion); knee peaks in the sagittal (fl exion/extension) and frontal plane (varus/valgus); hip peaks in the sagittal (fl exion/extension) and frontal plane (adduction/abduction); range of the pelvis movement in the sagittal (pelvis tilt); frontal (pelvis obliquity) and transverse plane (pelvis rotation) were quantifi ed and evaluated by means of the Vicon Nexus 1.0 and Polygon Authoring Tools.
Collected data were analyzed by means of the Student t-test (Statistica 9.0, StatSoft, Inc.). The statistical signifi cance level was set as 0.05. Moreover, the omegasquared (ω 2 ) quantity was determined to be a measure of the eff ect size. A "rule of thumb" was employed if it was greater than 0.01 as a small eff ect, greater than 0.06 as a medium eff ect and greater than 0.15 as a big eff ect (Cohen, 1988).

RESULTS
The mean values and the standard deviations of measured variables in people with HV compared to CG are shown in TABLE 1. In people with HV, a significantly greater maximum of plantar fl exion during the loading response (p < 0.01, ω 2 > 0.06) and a smaller maximum of the dorsal fl exion during midstance (p < 0.01, ω 2 > 0.06) were found (Fig. 1). Maximal knee extension at the end of the swing phase was signifi cantly greater (p < 0.01, ω 2 > 0.06) in subjects with HV (Fig. 2). In the frontal plane, a signifi cantly smaller maximum of hip abduction (p < 0.01, ω 2 > 0.06) during the gait cycle was observed in people with HV (Fig. 3). The range of pelvic obliquity (p < 0.01, ω 2 > 0.06) (Fig. 4) and pelvic rotation (p < 0.01, ω 2 > 0.06) were signifi cantly smaller in people with HV.

DISCUSSION
The hallux and the fi rst metatarsophalangeal joint (MTPJ I), together with the plantar aponeurosis, play a major role in loading transmission during gait. Dysfunction of these structures in the case of HV deformity can cause excessive foot pronation (Huang, Kitaoka, An, & Chao, 1993;Waldecker, 2004), which increases the range of forefoot movement, aff ects foot stabilization and resupination at the end of the stance phase (Frank, Satake, Robinson, & Gentchos, 2009). The excessive pronation found by Bolgla and Keskula (2003) represents the most common biomechanical problem and is often cited as a key contributor in many overuse injuries of the lower limb and lower back. Excessive pronation, according to Dinsdale (2009), is synonymous with excessive calcaneal eversion and increased internal tibial rotation. Root, Orien, and Weed (1977) reported that abnormal subtalar joint pronation can be a result of forefoot varus, rearfoot varus, tibia vara, ankle joint equinus and a plantar fl exed fi rst ray.
Our results confi rm that HV deformity infl uences the movement of the whole lower extremity and pelvis during gait. The greater plantar fl exion at the beginning of the stance phase was also found in subjects with juvenile HV (Janura et al., 2008). The smaller dorsifl exion during the stance phase corresponds to the results of the 3D gait analyses using the multisegment foot model in subjects with HV (Deschamps, Birch, Desloovere, & Matricali, 2010;Hwang et al., 2006). Glasoe, Nuckley, and Ludewig (2010) found that people with HV had an increased range of adduction during mid-swing at the forefoot-rearfoot angle and a decreased inversion, whereas during the pre-swing phase, a signifi cantly increased rearfoot eversion was found. These changes in the frontal plane movement of the foot can relate to lesser hip abduction during preswing in our experimental group. For an optimal performance of the toe off , dorsifl exion in MTPJ I within the range of 65 degrees is necessary. The physiological range of the hallux dorsifl exion is from 20 to 30 degrees; the plantar fl exion of the fi rst metatarsal compensates for the missing 40 degrees. The excessive pronation of the foot does not infl uence the required dorsifl exion in MTPJ I (Frank et al., 2009). Similarly, in functional hallux limitus, extension of the MTPJ I during weightbearing is not possible. According to Dinsdale (2009) the limited plantar fl exion of the fi rst ray compensates for the disturbed stabilization of the fi rst metatarsal against the ground, owing to excessive pronation or delayed resupination. This condition is known as "sagittal plane blockage". Sagittal plane blockage can, according to Danaberg (1993aDanaberg ( , 1993b and Dananberg and Guiliano (1999), cause and perpetuate many chronic postural complaints, which include lumbar stress and chronic low back pain. Dimonte and Light (1982) reported that the patients with HV will tend to keep their weight on the lateral border of the foot. The propulsion cannot be made optimally in cases of HV. Patients with HV have to use apropulsive gait. Apropulsive gait could explain the smaller degree of hip abduction at the toe off , which we found in our experimental group as well.
Our experimental group used a lesser range of pelvis obliquity and pelvis rotation as compared to the CG. Dinsdale (2009) reported that the foot should be stable to ensure quality support during the stance phase. The failure of foot stabilization due to forefoot dysfunction disrupts the function of muscles stabilizing the pelvis. Over time these muscles become, according to Dinsdale (2009), fatigued, weak, hypotonic and tender upon palpation. This often leads to abnormal pelvic movement, pelvic muscle imbalance and pelvic instability. Dananberg (1993aDananberg ( , 1993b found the relationship between a common, but rarely recognized entity known as "functional hallux limitus" and chronic postural complaints, including lumbar stress and chronic low back pain. The lesser range of pelvis motion can be also related to a reduced walking speed and a shorter stride length, which was demonstrated in other studies of the gait in subjects with HV (Khazzam, Long, Marks, & Harris, 2007;Menz & Lord, 2005).

CONCLUSIONS
This study demonstrated that HV does not exclusively concern the foot. The centralization and stabilization failure of the fi rst metatarsophalangeal joint does not allow patients with hallux valgus deformity to perform heel off and toe off optimally. It can be especially negatively projected at the end of a pre-swing phase during walking. The valgus deformity of the big toe can negatively infl uence function of the lower extremities and can cause overloading of those segments as well. D ananberg, H. J. (1993b). Gait style as an etiology to chronic postural pain. Part II. Postural compensatory process. Journal of the American Podiatric Medical Association, 83(11), 615. D ananberg, H. J., & Guiliano, M. (1999). Chronic low back pain and its response to custom made foot orthoses. Journal of the American Podiatric Medical Association,89(3), 109. D eschamps, K., Birch, I., Desloovere, K., & Matricali, G. A. (2010). CÍLE: Účelem této studie bylo analyzovat a interpretovat rozdíly v kinematických parametrech chůze u osob s hallux valgus v porovnání s kontrolní skupinou.