Juan López Pascual1, José Manuel Frías Bocanegra1, Marta Inglés de la Torre2, Nuria Sempere Rubio2, David Garrido Jaén1, Ignacio Bermejo Bosch1,3, Xavier Andrade Celdrán1
(1) Instituto de Biomecánica (IBV) Universitat Politècnica de València (Edificio 9C) Camino de Vera s/n (E-46022) Valencia (Spain)
(2) UBIC, Physiotherapy Department of the Universitat de València
(3) The IBV Health Technology Group, Bioengineering, Biomaterials and Nanomedicine CIBER (CIBER-BBN)
There is a high incidence of ankle sprains among military personnel. Poor recovery usually leads to the injury becoming chronic and recurrent. The Instituto de Biomecánica (IBV) has used the Kinemov/IBV movement analysis application to study the functionality of the ankle in military personnel with a history of sprains from the Military Emergency Unit (UME). When comparing the kinematics of the injured ankle to that of a healthy ankle during a single-leg jump, we have found a limitation of plantar flexion in the phase prior to landing. This finding would indicate the existence of functional sequelae in ankles that have in theory experienced a full recovery. The results of the study show that the information provided by a motion study could help to identify functional alterations of the ankle, point the way towards a better recovery, and avoid future problems.
INTRODUCTION
The Military Emergency Unit (UME) frequently travels across uneven terrain, which places high demands on the structures of the ankle and results in a very high incidence of ankle sprains.
Approximately 10 to 30% of people who suffer an ankle sprain develop chronic instability in the joint, increasing the risk of recurrence by 3.5 times. For this reason, it is very important to detect and treat ankle problems in order to recover the full functionality of the joint, and to prevent the injury from becoming chronic and causing more problems in the future.
Biomechanical tests can be used to identify anomalous patterns that are indicative of incomplete functionality. In the case of the ankle, previous research has studied the landing phase after a single-leg jump, observing changes in kinematics and in ground reaction forces in subjects with a previous injury when compared to a control group [1].
However, such comparison with a control group is not always a good option. Population groups such as athletes or military personnel, as a consequence of the training associated with their professional performance, develop special physical and biomechanical characteristics that can make comparison with a control group ineffective. In these cases, we would be better advised to make a comparison with the healthy contralateral limb.
We have not found any relevant scientific works that have studied the differences in a single leg jump between the injured ankle and the healthy contralateral one. This makes this study especially relevant.
The main purpose of this study is to analyze whether there are any differences between the affected side of the body and the healthy one in members of the Military Emergency Unit (UME) with a history of ankle injuries.
MATERIAL AND METHODS
Participants and description of the test
A group of 66 individuals from the Third Military Emergency Battalion (BIEM III) of the Military Emergency Unit (UME) took part in an ankle instability biomechanical assessment project. 35 of them had a history of ligament pathology in the ankle joint. In this paper we present the analysis of the data collected from the first 13 participants with a history of ankle injury. The purpose of this exploratory study is to determine the potential of the variables described in the bibliography to assess the affected ankle in comparison with the healthy contralateral ankle.
The tests were carried out in the Human Movement Laboratory at the Instituto de Biomecánica (IBV). The experiment was carried out by personnel from the UBIC research group, from the Physiotherapy School of the University of Valencia. After a warm-up routine, participants were instructed to perform a series of three single leg drop jumps. The test consisted in dropping with one leg from a box with a height of 40 cm onto a dynamometric platform embedded in the floor and managing to stabilize without using the other leg for support (Figure 1).
Figure 1: Example of the execution of a single leg jump with the right leg
Configuration and data collection
The study was recorded using the Kinemov/IBV human movement capture and analysis system, using photogrammetry and dynamometrical platforms. We discarded the use of surface electromyography due to the fact that the bibliographic findings suggested that it was not of interest.
From the set of predefined kinematic models presented by Kinemov/IBV, we selected the Lower Limb Bilateral model. This model calculates the joint kinematics of the hip, knee and ankle in the three anatomical axes, in accordance with the recommendations of the International Society of Biomechanics, allowing us to obtain the variables of interest defined at the beginning of the study.
The following steps were followed in each case: 1. Instrumentation with reflective markers, following the application’s anatomic location instructions; 2. Recording of the reference posture; 3. Recording of three jumps with each foot.
Once it has finished recording, the system automatically calculates and presents the kinematic (joint angles and velocities) and dynamic (reaction forces and rotational movement) variables (Figure 2).
Figure 2: Example of results calculated by Kinemov/IBV after the recording of a single-leg jump
Calculation of variables of interest
From the prior analysis of the literature, we identified four main groups of biomechanical effects in patients with an ankle injury associated with this test: 1. Alteration in the maximum reaction forces; 2. Changes in the stabilization times; 3. Alteration of the kinematics of the lower limb; 4. Increased dispersion between measurements (variability).
In this exploratory study, we decided to analyze the results of the ankle joint kinematics, leaving the assessment of the effects on hip and knee kinematics and the dynamic analysis for a later comprehensive study.
Previous studies found differences when comparing ankle kinematics in persons with a history of ankle sprains with a control group, both in the phases before and after landing. In particular, changes were reported in plantar flexion and ankle inversion angles before landing and in dorsiflexion after landing [2,3,4]. Differences were also found in angular flexion velocity after landing [4] and in the variability between measurements [5].
In order to calculate these variables with Kinemov/IBV, the first step was to determine the instant of contact of the foot with the ground (tc). To do so, we took as our reference the vertical reaction force curves of the three repetitions and we cut the scenes to make the starting time of the three curves coincide at one common point (Figure 3). Once the curves where synchronized, we used the time scale to determine tc as the instant at which the force no longer zero.
Figure 3: A: Original force curves; B: Synchronization of the three repetitions and determination of the instant of impact on the platform
In order to calculate the variables of interest we used the “Variable + Table” option, which makes it possible to calculate characteristic values of the curves for a given time interval. In order to obtain the pre-landing and post-landing variables, we defined the time interval [tc – 0,2: tc + 0,2], based on criteria taken from the bibliography (Figure 4).
Figure 4: Calculation of variables of interest using the variable + table option
By introducing the calculation limits, the values of the table are updated by applying the calculations to the range of established times. Once the graph was built, we used the ‘save for report option’ to save the configuration of the graph.
This process was repeated for the following curves: flexion-extension, inversion-eversion and angular velocity of flexion-extension of the ankle of the supporting foot, both for the jump with the right foot and the one with the left foot.
From the tables calculated by Kinemov/IBV, we directly obtained the variables of interest in the following way:
• Maximum plantar flexion of the ankle before landing: average of the minimum flexion/extension values.
• Maximum dorsiflexion of the ankle after landing: average of the maximum flexion/extension values.
• Maximum inversion of the ankle before landing: average of the maximum inversion/eversion values.
• Maximum angular flexion velocity of the ankle after landing: average of the maximum flexion/extension angular velocity values.
• Variability between ankle flexion measurements: Coefficient of variation (CV) of the maximum values and CV of the minimum flexion/extension values.
Analysis process
In order to automate the analysis process, we generated a report template with Kinemov/IBV. We included in the report the graphs and tables generated for the calculation of the variables of interest. In this way, for the following measurements, the analysis process was reduced to three steps: Importing the report template, identifying tc and defining the calculation limits for the update of the values in the tables.
The calculated values for the healthy and the injured legs were transferred to a spreadsheet to perform a descriptive analysis of the results.
RESULTS AND DISCUSSION
The purpose of this exploratory study was to assess the existence of functional sequelae in UME personnel with a history of ankle sprains. To this end, we analyzed the joint kinematics of the injured ankle and the healthy contralateral ankle during the execution of a single-leg jump. A T-test of related measurements was performed with the obtained measurements (Table 1).
85% of participants had less plantar flexion in the pre-landing phase with the foot with a history of sprains, when compared to the foot without prior injury. In this sense, it was shown that rigidity is generally higher in people who have previously suffered a sprain [6], which could justify the limitation observed in plantar flexion. Another explanation could be that the subjects have developed a protective mechanism, modifying the position of the foot to reduce the load on the ankle ligaments at the moment of impact. However, this cannot be determined exactly, because no subjective analysis of the perception of motor control or stability of the participants was carried out.
The rest of the variables studied did not present any changes between the injured side and the contralateral side. The absence of differences in the post-landing variables would indicate that the anatomic structures of the ankle have recovered the necessary strength to support the weight of the body after the fall. In particular, the absence of differences in variability and velocity would reflect a good recovery of ankle control and stability.
These results must be treated with caution, given that this is an exploratory study with a reduced sample size. Once all the measurements have been completed, we will carry out a comprehensive analysis of the variables and the statistical study that will allow us to obtain definitive conclusions.
CONCLUSIONS
This study has allowed us to verify that the assessment of a single leg jump and the comparison between the affected side and the contralateral side can be an appropriate approach to the evaluation of sequelae deriving from ankle sprains in military personnel.
The exploratory analysis using Kinemov/IBV has been extremely useful to obtain results in a fast and simple way.
ACKNOWLEDGEMENTS
We would like to thank the BIEM III of the Military Emergency Unit, for their collaboration, support and participation in this research project.
This activity has been carried out within the framework of the IMAMCJ/2020/1 project, financed by Registered Grant S8021000, distributed in favor of the technological centers of the Autonomous Community of Valencia, approved by the Budget Law of the Generalitat (Government of Valencia) for 2020.
REFERENCES
[1] Simpson, J. D., Stewart, E. M., Macias, D. M., Chander, H., & Knight, A. C. (2019). Individuals with chronic ankle instability exhibit dynamic postural stability deficits and altered unilateral landing biomechanics: A systematic review. Physical Therapy in Sport, 37, 210-219.
[2] Brown, C., Padua, D., Marshall, S. W., & Guskiewicz, K. (2008). Individuals with mechanical ankle instability exhibit different motion patterns than those with functional ankle instability and ankle sprain copers. Clinical Biomechanics, 23(6), 822-831.
[3] Caulfield, B. M., & Garrett, M. (2002). Functional instability of the ankle: differences in patterns of ankle and knee movement prior to and post landing in a single-leg jump. International Journal of Sports Medicine, 23(01), 64-68.
[4] Delahunt, E., Monaghan, K., & Caulfield, B. (2006). Changes in lower limb kinematics, kinetics, and muscle activity in subjects with functional instability of the ankle joint during a single leg drop jump. Journal of Orthopaedic Research, 24(10), 1991-2000.
[5] Kipp, K., & Palmieri-Smith, R. M. (2012). Principal component-based analysis of biomechanical inter-trial variability in individuals with chronic ankle instability. Clinical Biomechanics, 27(7), 706-710.
[6] Lin, C.-Y., Shau, Y.-W., Wang, C.-L., Kang, J.-H., 2015. Modeling and analysis of the viscoelastic response of the ankle ligament complex in inversion ankle sprain. Ann. Biomed. Eng. 43, 2047–2055.
