Effect of floating toes on knee and trunk acceleration during walking: a preliminary study (2024)

Abstract

[Purpose] This study investigated the effect of floating toes on knee and trunkacceleration during walking in experimental setting. [Subjects and Methods] Twelve healthyvolunteers walked barefoot at a preferred speed along a linear pathway under 2 conditions:normal gait (control) condition and floating toes (FT) condition. In the latter, weightbearing by the toes was avoided using kinesiology tape applied along the toe extensors.Accelerations of the knee (Kn) and lumbar spine (Lx) were assessed using triaxialaccelerometers mounted on the right fibular head and the spinous process of L3.Acceleration vectors were oriented such that the anterior, right, and cranial deviationswere positive along the anteroposterior, lateral, and vertical axes, respectively. Theroot mean squares (RMSs; anteroposterior, RMSap; lateral, RMSl; vertical, RMSv) werecalculated, and the mean values of 3 trials in each condition were determined. Differencesbetween the conditions were assessed using the Wilcoxon signed-rank test. [Results]LxRMSap and LxRMSv were larger in the FT condition than in the control condition. KnRMSvtended to be higher in the FT condition than in the control condition. [Conclusion]Floating toes increase acceleration and might create mechanical stress on the lower backand knee during walking.

Key words: Floating toes, Walking pattern, Triaxial acceleration

INTRODUCTION

The foot is the foundation of the human body, as it is the first part of the body thatcontacts the ground during gait. Hence, toe flexor function is essential for balancing¹⁾ and walking²⁾. However, in clinical practice, patients often present with lowerextremity or lower-back dysfunction and unable to touch the ground with their toes—that is,floating toes³⁾—during walking andstanding. Floating toe syndrome is the condition in which one or more toes fail to purchasethe weight bearing surface in stance and walking³⁾: elevation of the metatarsal ray prevents it from being loaded underthe weight-bearing condition. Floating toe has been reported to be an aftereffect of footsurgery^{4, 5)}, and decrease in toe grip strength may be one of the factors causingfloating toes in adult⁶⁾.

In Japan, floating toe has recently been focused on as a malalignment of the foot both inadults^{6, 7)} and children^{8, 9)}. Because these studies are epidemiologicalstudies, the association between floating toe and physical function has remained unclear.Biomechanical change in one joint can influence the kinetics or kinematics of proximal ordistal joints during weight bearing; hence, floating toe may also affect the kinetics orkinematics of proximal joints. Therefore, floating toe may influence gait pattern. Faultyfoot biomechanics can adversely affect all supporting joints above the foot, including thelower back¹⁰⁾. Toe flexor function isessential for producing the propulsive force at the toe, which is essential for walking;floating toe-induced insufficient toe flexor function may have a negative influence on theknee, hip, and lower back. For example, Dananberg and Guiliano¹¹⁾ stated that appropriate treatment to correct gait style byusing custom-made foot orthoses was effective in improving the symptoms of lower-back pain;in other words, altering the gait pattern influences lower-back pain.

In assessing gait patterns, accelerometers are advantageous over traditional gait analysisinstruments, such as three-dimensional motion analyzer and force plates, because of theirlow cost, compact size, and ability to be used outside of a laboratory environment^{12, 13)}. Therefore, because walking is a relatively unrestricted motion, itis ideal for quantifying gait abnormalities, for determining how individual adapts tofunctional disturbances, and for evaluating changes in gaitpatterns¹²⁾.

Therefore, this preliminary study investigated the effect of floating toes on knee andtrunk acceleration during walking by using accelerometers. We hypothesized that floatingtoes during walking might affect the normal gait pattern and thus have an effect on knee andtrunk acceleration.

SUBJECTS AND METHODS

This study was approved by the Research Ethics Committee of Kio University (H23-35). Allparticipants provided written informed consent prior to participating in the study.

Twelve healthy volunteers (9 males, 3 females; age, 21.2 ± 0.7 years; height, 165.8 ±8.0 cm; weight, 59.3 ± 7.9 kg) were asked to walk barefoot at a preferred but constant speedalong a linear pathway under 2 conditions: with normal gait (control condition) and withinhibited toe flexion to prevent weight bearing on the toes (floating toe (FT) condition).The test order of the two conditions was randomized. Participants’ 10-m walking speed wasmeasured using a stopwatch. Accelerations of the knee (Kn) and lumbar spine (Lx) weremeasured using triaxial accelerometers (MVP-RF-8-GC-500, Microstone Corporation, Nagano,Japan) mounted on the right fibular head¹⁴⁾and the spinous process of L3^{12, 13, 15)}. Acceleration vectors were oriented such that the anterior, right,and cranial deviations were positive along the anteroposterior, lateral, and vertical axes,respectively, on the basis of the local coordinate axis on the accelerometers (6 degrees offreedom). Heel strike was confirmed using pressure sensors placed under both heels. In theFT condition, toe flexion was inhibited using kinesiology tape (NKH-25, Nitto DenkoCorporation, Osaka, Japan) applied along the toe extensors at the maximal extensionposition. Reduced weight bearing on the toes was confirmed using a force platform (WinFDM;Zebris, Isny im Allgäu, Germany). The participants were instructed to initiate walking withthe left foot, and data from the sixth and eighth steps, both of which were in the stancephase on the right side, were recorded. The same protocol was repeated 3 times in eachcondition at a sampling rate of 1 kHz. The root mean squares (RMSs) (anteroposterior, RMSap;lateral, RMSl; vertical, RMSv) were calculated, and the means of 3 trials in each conditionwere determined.

Differences between the two conditions were assessed using the Wilcoxon signed-rank test.All statistical analyses were performed using SPSS version 22.0 (IBM, Tokyo, Japan), withthe level of significance set at 5%.

RESULTS

Participants’ walking speeds in the control and FT conditions were 4.33 km/h ± 2.71% and4.29 km/h ± 2.65%, respectively. LxRMSap and LxRMSv were higher in the FT condition than inthe control condition (p=0.013 and 0.046, respectively). Similarly, KnRMSv tended to behigher in the FT condition than in the control condition (p=0.055) (Table 1).

DISCUSSION

This study demonstrated that floating toes during walking increased anteroposterior andvertical accelerations of the lower back and tended to increase vertical acceleration of theknee. Hessert et al.¹⁶⁾ identified adifference in the foot-pressure distribution in the hallux region of healthy young andelderly groups during walking. A factor related to age-related changes in walking patternsmight be a change in the toe contact area. Floating toe–induced insufficient toe contactwith the ground—that is, reduction in the toe contact area—means a smaller support base,which might influence postural control during the single-leg stance phase during walking.Elis et al.¹⁷⁾ reported that reducedplantar sensation causes a cautious walking pattern. Tanaka et al.¹⁸⁾ highlighted the importance of toe strength andsomatosensory feedback from the sole during dynamic single-leg balancing. Floatingtoe–induced reduction in the support base might result in decreased sensory input from theplantar surface, which might lead to changes in the walking pattern.

Typically, weight-bearing during walking proceeds from the heel to the toe, which enablesthe generation of the propulsive force. However, floating toe–induced insufficient toecontact prevents normal weight-shift from the posterior to the anterior during walking;hence, vertical acceleration of the knee and trunk might increase. Menz et al.¹⁹⁾ reported that head acceleration tostabilize its position was not affected even if pelvic acceleration increased. Theydemonstrated that in order to stabilize head position during walking, trunk accelerationmight compensate for the change in postural control strategy caused by insufficient toecontact with the ground.

An abnormal gait eventually interferes with spinal segmental movements²⁰⁾, which could lead to serial postural distortions, muscularimbalances, and spinal joint dysfunction. Some researchers have demonstrated changes in themotor control of the trunk during walking in patients with chronic lower-back pain^{21, 22)}. Therefore, increased anteroposterior and vertical accelerations ofthe lower back might induce increased mechanical stress on the discs, facet joints, andmuscles, which in turn might cause degenerative changes of the lumbar structures and/orlower-back pain. Electromyography and three-dimensional motion analysis studies can furtherclarify the influence of floating toes on muscle activity and movement of the trunk.

In this study, floating toes during walking tended to increase vertical acceleration of theknee. This change might result in increased mechanical stress, which could affect thearticular cartilage of the knee. In their case–control cohort study, Segal et al.²³⁾ reported that maximum articular contactstress was higher in incident cases with osteoarthritis (OA) of the knee compared withnormal control knees. Gross et al.²⁴⁾reported that planus foot morphology was associated with frequent knee pain and medialtibiofemoral cartilage damage in older adults. Moreover, an association between the halluxand knee OA²⁵⁾, including that between lowpressure on the hallux during walking and medial knee OA²⁶⁾, has been reported. Therefore, insufficient floating toe–inducedtoe contact caused might be associated with development of knee OA. In future studies, therelationships of toe contact with knee motion and muscle activity should be investigated ina clinical setting in patients with knee OA.

This study has several limitations. First, the sample was small and had more males thanfemales. Second, this study did not consider the differences in the functions of the halluxand lesser toes because experimental floating toes included all toes. In addition we did notmeasure foot pressure in the toe region, although we could confirm that toe region did notcontact during walking in the FT condition. Future studies are required to examine suchmultidimensional aspects as ground reaction force, muscle activity, and three-dimensionalmotion, although the associations between insufficient toe contact with the ground andaccelerations of the knee and trunk were investigated in this study. Furthermore, becausethis was an experimental study, additional studies are needed to clarify the influence oftoe function during walking in patients with lower-back pain or knee dysfunction in aclinical setting. These studies might elucidate the unknown cause of musculoskeletaldysfunction and can lead to the development of a novel physical therapy. In conclusion,floating toes increase anteroposterior and vertical accelerations of the lower back and tendto increase vertical acceleration of the knee during walking. Therefore, insufficient toecontact might increase mechanical stress on the lower back and knee, which might causemusculoskeletal dysfunction.

REFERENCES