Francisca Peydro de Moya; Ignacio Bermejo Bosch; Cristina Herrera Ligero; Enric Medina Ripoll; David Guerrero Ramos; Xavier Andrade Celdrán; Juan López Pascual

Instituto de Biomecánica (IBV) Universitat Politècnica de València. Edificio 9C. Camino de Vera s/n (46022) Valencia (Spain)

NedAMHPlus/IBV is a software application designed by the Instituto de Biomecánica (IBV) to help the clinician to carry out an objective analysis of gait in a simple, fast and - of paramount importance - easily interpretable way, given that it focuses on detecting and quantifying the primary dynamic and kinematic deficits thereof. The following clinical case allows us to demonstrate the usefulness of this application in the process of interpreting the results obtained through this test and making therapeutic decisions based on those results.

 

INTRODUCTION

A considerable percentage of pathologies of neurological origin, musculoskeletal disorders, and movement disorders associated with pain lead to alterations in ambulation. The movement analysis systems we use today make it possible to study in detail the repercussion these alterations have on a persons’ gait, but the downside is that it is by no means easy to apply these evaluation protocols in daily clinical practice due to their complexity, the length of time it takes to perform the test, and the fact that it is hard to interpret such a large number of results.

Faced with this practical difficulty, NedAMHPlus/IBV emerges as a software application specifically designed to analyze human gait in a simple, agile and easily interpretable way. It uses a simple test that normally takes about 30 minutes to quantify the functional state of a person’s gait in comparison with the normal population, from the moment the patient is instrumented until the measurement is obtained. It makes it possible to quantify the gait disorder, guiding the type of treatment to be implemented and evaluating its efficacy, although it does not provide an etiological diagnosis nor the anatomical location of a lesion.

This application uses data provided by a dynamometric platform, a photogrammetry system and, optionally, surface electromyography, to show the degree of functional gait capacity of the person being assessed. It is specially designed for use by rehabilitation physicians, orthopedic surgeons and physicians employed by work accident mutual insurance companies, and it is used for medical-legal assessments, the evaluation of bodily injury, the assessment of rehabilitation possibilities, and to plan and monitor treatment.

The following is a case report of a patient whose first toe had been amputated, assessed with NedAMHPlus/IBV before and after treatment. The purpose of this example is to show the usefulness of this application as an easy-to-use and easy-to-interpret tool that helps the clinical specialist in their decision-making process.

CLINICAL CASE 

A 39-year-old man whose first toe of the left foot had been crushed. He underwent surgery followed by a torpid evolution that ended up requiring amputation of the toe due to a disabling pain when walking. Despite surgery, he continued to experience pain that increased while walking. The physical examination revealed hyperkeratosis due to increased support on the lateral border of the sole of the left foot. Mobility and strength in both ankles were good and there was discrete claudication when weight is was placed on the left foot.

He is referred to the biomechanical assessment clinic of the Instituto de Biomecánica (IBV) for an assessment test to quantify gait ability and at the same time obtain objective data to guide and control the treatment.

An assessment was carried out with the NedAMHPlus/IBV application which analyzes gait dynamic pattern (reaction forces exerted by the lower limb during the stance phase) and kinematic pattern (sagittal plane joint mobility of the lower limbs and progression of the foot throughout the gait cycle). The recording techniques were a dynamometric platform together with two photocell barriers used to record gait speed and a 3D photogrammetry system. To carry out the assessment, NedAMHPlus/IBV compares the parameters obtained in both extremities with a normality database developed by the IBV. In the case of dynamic assessment, the database is segmented by age, gender, speed and the presence of footwear.

The patient was instrumented following a simplified Plug in Gait (PiG) model, which ensures accuracy in the sagittal plane using only 10 markers. The instrumentation process provided is simple and fast due to the easy location of the anatomical points at which the markers are to be placed. The measurement protocol consists of walking along a walking corridor at a comfortable speed, recording only 6 steps taken with each foot. The system analyzes all the information registered and automatically provides a report with the test results, which are summarized in three indexes:

1. Global Kinematic Assessment: the result of the analysis of the mobility in the sagittal plane of the joints of both lower limbs.

2. Global Dynamic Assessment: the result of the analysis of the speed, the difference in stance time and the reaction forces that are generated in the stance phase.

3. Repeatability: an analysis of the regularity of the dynamic parameters analyzed.

At a global level, it is considered that the functional capacity of gait remains within the normal range when both indexes (Global Kinematic Assessment and Global Dynamic Assessment) are equal to or higher than 90%, whereas it is considered functionally impaired when one or both indexes fall below 90% or when, in the opinion of the assessing physician and based on the test results as a whole, there is an equivalent assessment. One might say that the lower the overall assessment is the greater the degree of functional impairment.

RESULTS OF THE CASE

An initial assessment of the final result of the gait analysis carried out with NedAMHPlus/IBV showed an altered global functionality, quantified by a global kinematic result of 85% and a global dynamic result of 73% (Figure 1, top). This result means that the patient’s gait pattern is different to that of the normal population both from the point of view of the forces exerted in the stance phase and from that of lower limb mobility throughout the entire gait cycle.

Figure 1: Final result of gait functionality through kinematic and dynamic biomechanical assessment. Values equal to or greater than 90% are considered functionally normal. Top: Condition before treatment. Bottom: Condition after treatment.

In order to better understand the reason for this functional alteration and to decide on the best possible treatment, the results obtained were subjected to a detailed analysis. The dynamic analysis showed the existence of a claudication during gait with a shorter stance time of the left foot (Figure 2) explained by the difficulty of support consistent with its structural damage.

Figure 2: Graphical representation of the ground reaction force during the stance phase. Superimposition of the footfall records. (Right forces: orange lines. Left forces: purple lines). Condition before treatment.

The toe-off force and, most importantly, the left propulsive force, were deficient and asymmetric (40% asymmetry) (Figures 3 and 4, above). As a result, the main deficit was located in the final stance phase.

Figure 3: Graphical representation of a normal ground reaction force pattern during stance with its corresponding dispersion band (shaded) and mean pattern of the different components of the reaction force in the recorded footfalls. Top: Condition before treatment. Bottom: Condition with plantar orthosis. (Right forces: orange lines. Left forces: purple lines).

Finally, we observed an increased mediolateral force in the left stance in the context of a stance phase stability deficit in a foot with toe amputation (Figure 4, upper center).

Figure 4: Results in absolute values of the average dynamic parameters in gait. Top: Condition before treatment. Bottom: Condition with plantar orthosis.

The kinematic analysis, focused in this case on the joint mobility of the ankle and foot, showed a loss of the forefoot roll rocker implying less plantar flexion and therefore affecting the propulsion and toe-off deficit. In addition, there was also a decrease in the external rotation of the foot throughout the progression due to the acquired compensatory supination support. (Figure 5, top)

Figure 5: Average sagittal plane ankle mobility and foot progression during the gait cycle. Normality band (green). Right lower limb: lighter or orange line. Left lower limb: darker or purple line. Top: Condition before treatment. Bottom: Condition with plantar orthosis.

All these findings have to do with a loss of foot function at toe-off based on the deficit of action of the first toe due to reduced leverage in the stance and a compensation that shifts the load and propulsion to the external part of the sole of the foot. During gait, the first toe exerts an important action during the final stance phase, which consists of propelling the body forward, thus facilitating forward movement. Amputation of the first toe can modify this action, leading to the appearance of claudication. The patient walks in a more unstable manner, overloading the medial and external radii and thereby causing a supination of the forefoot, and the toe-off is therefore deficient due to the lack of contact of the first toe of the foot with the ground.      

RESOLUTION OF THE CASE

In the light of these biomechanical findings, it was decided to initiate a treatment that would facilitate stability during stance and facilitate toe-off. An orthosis consisting of an external device to replace the foot segment at the level of the first toe was prescribed. A new biomechanical analysis was performed assessing gait with the plantar orthosis to quantify the functional improvement obtained. In this new measurement condition (Figure 1, bottom), although the gait had not yet acquired a completely normal pattern in terms of reaction forces (78% of normality in its dynamic component), a clear improvement was however observed in the kinematic component (90% of normality). This treatment resulted in a correct anterior roll of the foot that facilitated toe-off (Figure 5, bottom). It was also possible to verify that a gait with greater footstep repeatability had been achieved (Figure 1, bottom), with a propulsive and toe-off force returning to normal (Figure 3, bottom) and a lower asymmetry of forces (Figure 4, bottom), thus minimizing claudication.

CONCLUSIONS

The use of NedAMHPlus/IBV as a fast and agile measurement system for functional gait analysis:

1. Allows functional assessment, from a dynamic and kinematic point of view, which is useful for clinical decision making.

2. Presents biomechanical results that can guide treatment as it locates and quantifies deficits.

3. Facilitates the control over time of the patient’s functional status in relation to their process.