The Influence of Short-term Restriction of Unilateral First Metatarsophalangeal Joint on the Contralateral Lower Limb Joints

To study the effect of restriction of unilateral movement of the first metatarsophalangeal joint (FMJ) on the biomechanics and gait of the contralateral lower limb. 8 adult college students completed walking with barefoot and left foot FMJ constraint (FMJC) respectively. The time node for collecting gait and biomechanical parameters is (I) 0min barefoot walking, (II) Walk immediately with FMJC at 0min, (III) walk after 30min with FMJC, (IV) walk barefoot after 30min with FMJC; Calculate the gait parameters on the contralateral side of the FMJC, the net joint torque and the joint moment arms of the hip, knee and ankle joints. Compared with the time node I, the maximum dorsiflexion angle and the maximum plantar flexion angle of the unrestricted side ankle joint at time node III increased significantly (p<0.05), and the maximum plantar flexion moment and maximum dorsiflexion moment increased significantly (p<0.05), the power of the ankle joint increased significantly (p<0.05); the torque and power of the hip and knee joints on the unrestricted side increased significantly (p<0.05); On the unrestricted side, there was no significant difference in stride length, swing phase, support phase and step length (p>0.05). Short-term unilateral FMJC will cause biomechanical compensation and compensation transmission in the unrestricted lower limb joints. That is, the unrestricted hip, knee, and ankle joints maintain normal gait by strengthening their work, and the transmission of compensation is enhanced from top to bottom.


Introduction
When studying the movement of lower body, researchers usually only focus on the movement features of the hip, knee and ankle joints, or simply consider the foot as a whole. At most, the movement of the foot involves only the subtalar(ankle) joint and the subtalar joint, while ignoring the Metatarsophalangeal Joint The role of the FMJ on foot movement cannot be ignored, and its flexion and extension characteristics can have an important impact on the running and jumping movements of the human body, especially the kick-off effect in the later stage of support [5,6]. Recent studies have shown that the FMJ, as the end joint of the human body, basically maintains an extended state during the process of pushing off the ground, so that the joint mainly absorbs energy before it leaves the ground, and the energy generated is almost negligible [7,8]. Study how the FMJ effectively transforms the absorbed energy, and the impact on the mechanical properties of the lower limbs is very meaningful [9,10]. The limited disease of the FMJ is common in various diseases, such as gout, diabetes, etc. [11,12]. The flexion and extension of the MJ will have an important impact on the human body's movement function, mechanical characteristics and other joint compensation of the lower limbs. The destruction of its stability will cause changes in the biomechanical characteristics of the forefoot, including the reduction of the range of motion of the MJ, the change of local plantar pressure, increased pressure around the joints, and then seriously affect the motor function of the foot and cause the functional compensation of the lower limbs [13][14][15]. Menz et al. measured the MJ plantar pressure and joint range of motion of 172 volunteers, analyzed and compared the relationship between the two and concluded that the correlation coefficient between MJ scope of activity and plantar pressure is 0.85 [16]. Budhabhatti et al. found through a three-dimensional finite element modeling study that completely restricting the flexion and extension of the FMJ will increase the pressure on the MJ by 223% [17]. Obviously, the importance of MJ to the normal activities of the human body is beyond doubt.
The results of our previous research show that [18], the FMJ constraint (FMJC) condition will increase the energy consumption of the ipsilateral ankle, knee, and hip joints. When the FMJ is restricted, the body mainly performs load generation through the ipsilateral hip, knee, and ankle joints. Compensation and transfer are used to maintain the dynamic balance of kinematics, and the compensation transmission is manifested as the sequential attenuation of the ankle, knee and hip joints. However, we did not study the energy changes of the unrestricted side joints. We assume that the compensation of joint load in the case of left FMJC can be transmitted from the left lower limb to the right lower limb, that is, the right lower limb joints increase work to contribute to the maintenance of the normal gait of the lower limbs. The purpose of this clinical research is to understand the biomechanical connection between the FMJ and the bilateral hip, knee and ankle joints of the lower limbs.

Inclusion and Exclusion Criteria
We refer to our previous experimental methods [18], Recruit 8 healthy young volunteers to participate in the trial (4 men and women). All subjects were informed of the trial process and requirements in advance. The trial was conducted after the subjects'  The equipment used in this experiment is mainly composed of the gait walking test bench ( Figure 1A), the data acquisition system, and the FMJC device ( Figure 1BC). The FMJC device used in the test consists of a low-temperature thermoplastic sheet provided by Convalesce ® , medical gauze and Velcro marking points. During the research, the FMJC was made according to the foot shape of each subject, thereby restricting the movement of the FMJ. The data acquisition system consists of a Vicon 3D optical motion capture system, which includes 6 MX infrared cameras and two AMTI biomechanics force plates. The force plate used to collect gait parameters has a collection frequency of 1000 Hz and a size of 464 mm×508 mm. The total length of the gait walking test bench is 5m, the width is 2m, and the height is 2.5m. The force plate is embedded in the walking test bench, and the angle of the force plate ground can be adjusted to ensure that the force plate and the surface of the test bench are in a horizontal plane.

Experimental Process
Before the gait analysis started, the experimenter calibrated the

Data Analysis
Calculate the three-dimensional angle, joint torque, and joint power of the hip, knee, and ankle joints on the unrestricted side of FMJC. The parameters in the two cases were compared by pairedsample t-test. The significance level was set as the probability of type I error not greater than 0.05, and all statistical analysis was completed with SPSS 24.0 software.

Results and Discussion
Gait parameters of the right lower extremity in the case of FMJC of the left lower extremity Compared with time node (I) 0min barefoot walking, there is no significant difference in the basic gait parameters of the right lower limb when walking with the FMJ on the left side (p>0.05) ( Table 1).

Kinematics and Biomechanical Parameters of the Ankle Joint of the Right Lower Extremity in the Case of FMJC of the Left Lower Extremity
The sagittal angle, torque, and power curves of the right lower   ultimately improve athletic performance [4,12].

Am J Biomed Sci & Res
Copy@ Ji Y, Xu R

Dynamic Changes of the Unrestricted Hip, Knee and Ankle Joint in the Case of Short-Term Unilateral FMJ Movement Restriction
In this trail, unilateral FMJC significantly affected the biomechanical parameters of the ankle, knee, and hip joints of the unrestricted side of the lower limb when walking, but there is no significant difference in gait parameters on the unrestricted side of the lower limbs; In order to ensure the integrity of the movement of the human body, adjacent and distal joints have a compensation function [19,20]. Although short-term FMJC is only shown in the data as ankle, knee and hip joint load transfer, the knee joint load change is not obvious, but research shows that long-term knee joint load increase will greatly increase the morbidity of the knee joint [21]. Therefore, the potential risk of FMJC is not only for the contralateral ankle joint, but also for the contralateral knee joint and even the hip joint; the treatment effect of many patients with knee arthritis is not satisfactory because the function of the foot and ankle is not paid attention to. Existing research have shown that foot and ankle function have an impact on knee joint disease [22], However, the influence of FMJC is not pointed out. The results of this study proved the following hypothesis: FMJC has a potential impact on the occurrence and development of knee arthritis in the contralateral lower limb.

In the Short-Term Unilateral Movement of the FMJ is Restricted, There is Motion Compensation Transmission in the Unrestricted Side Ankle, Knee and Hip Joint
In this trail, FMJC significantly affected the biomechanical parameters (torque, power, angle, etc.) of the unrestricted side ankle joint, knee joint, and hip joint during walking, while the traditional kinematics data (such as step length, step width, pace, etc.) showed no significant changes. If one joint has disease, other adjacent joints will use motion compensation to ensure the integrity of motion [23,24].

Shortcomings and Prospects
Of course, our research still has many shortcomings. First of all, the number of our subjects is relatively small, and the accuracy of the experimental results will be affected; Secondly, the FMJC brace we use still has defects in restricting the movement and durability of the MJs, and more suitable materials can be used in the future; We have not paid attention to the impact of some movement

Grant Support
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.