·Home ·Table of Contents ·General

Testing Vibration Analysis of the Achilles Tendon State Author Maslov Leonid Borisovich PhD, Professor 34 Rabfakovskay Str., Ivanovo, 153548, Russia Theoretical and Applied Mechanics Department State Power University of Ivanovo Tel., (0932)38-57-84 Fax: (0932)38-57-01 E-Mail: ispu@iname.com (for L.B. Maslov) Co-Authors Shapin Vadim Ivanovich PhD, Professor 34 Rabfakovskay Str., Ivanovo, 153548, Russia Theoretical and Applied Mechanics Department State Power University of Ivanovo Tel., (0932)38-57-84 Fax: (0932)38-57-01 Korablev Stanislav Sergeevich DrS, Professor 34 Rabfakovskay Str., Ivanovo, 153548, Russia Theoretical and Applied Mechanics Department State Power University of Ivanovo Tel., (0932)38-57-84 Fax: (0932)38-57-01 Contact

Abstract:

The accurate diagnostics of the Achilles tendon fractures and the permanent control on the rehabilitation process is the actual medical problem. A stand for vibratory examination of Achilles tendon state is suggested. The equipment records amplitude-frequency characteristics of the shank tendon-muscular complex that depend on physical and mechanical parameters of the investigated object conditioned by the real tissue state around the injury. A very detailed system of diagnostical criteria is developed. The method described is applied for investigating the shanks of the patients with acute and ancient Achilles tendon tears in the Ivanovo war veteran hospital.

Keywords: achilles tendon, tear, vibration, resonance, diagnostics.

1. Introduction

In this paper we consider an attempts of employment of the vibrodefectoscoping approaches to biomechanical objects. The accurate diagnostics of the Achilles tendon fractures and the permanent control on the rehabilitation process is the actual medical problem. Damages of the Achilles tendon significantly decrease physiological muscle strain, lead to serious functional disorders in neural-muscular apparatus or even to stable disability. Traditional methods of traumatology for determining the fracture of the tendon cannot provide the necessary reliability of the diagnostics. Statistic analysis proves that in 63% of such traumas there are made diagnostic mistakes. The modern techniques such as X-rays, radio-isotopes or magnetic topography examinations are rather expensive and have the hard restrictions to their application. So a new combined approach to analyse a physiological state of the human shank is considered.

2. Experimental Approach

The objective of resonance vibrational diagnostics (RVD) is to provide construction status based on signals, describing the oscillating processes on the diagnostic object [1]. The main distinctive feature of this method is that noiseless and non-vibration constructions may serve as vibrodiagnostical object. The diagnostic parameters are dynamic characteristics of gain-phase-frequency distribution of the object, dissipate and non-linear structure properties found during local vibrational impact. So the test resonance vibrodiagnostics is being treated as a part of technical one where the examination of the object's technical condition is being fulfilled with the help of artificially induced vibration.
A stand for vibratory examination of Achilles tendon state is suggested. The device is composed of a platform with a firmly fixed vibrator, a splint for extremity fixation in the mid-physiological position, which is located on a firmly fixed table, a platform and a dynamometer [2]. The foot is being put on the platform and fixed with the belts. The platform has a rotator mechanism, the axis of rotation coincides with the axis of the ankle joint enabling foot position changes. Excitation of mechanical oscillation is brought about by the electrodynamical vibrator by means of a stock with a tip and is perpendicular to the axis of the Achilles tendon. A frequency and amplitude of oscillations are being changed by means of a sound generator and power amplifier. Oscillation measurements are fulfilled by means of a vibroreceiver-accelerometer which is fixed on the Achilles tendon close to the vibroconductor with the help of self-adhesive band. Parameters of the oscillation process, including resonance condition of the muscular-tendon complex, are being registered after preliminary intensification of the signal from the vibroreceiver by the vibrogauge, oscillograph and automatical recorder.
The device is being used in the following way. The patient lies on the table, the extremity is being put on the splint and fixed by the belts on the level of the thigh and on the platform for the foot. Register-accelerometer is being fixed by means of self-adhesive band on the level of projection of the mid-third of the Achilles tendon. The examination may be done in any foot position and any static effort of foot flexors and extensors.
The equipment records amplitude-frequency characteristics (AFC or resonance curve) of the human tendon-muscular complex automatically for different kinds of vibration excitation and for various positions of the foot. A resonance curve depends on physical and mechanical parameters of the investigated object conditioned by the real tissue state around the injury. The examinations using the developed equipment was made by researches of the interuniversity laboratory "Biomechanics" in a war veteran hospital in Ivanovo. Over 100 gain-frequency soft tissues characteristics of damaged and normal extremities were examined. Amplitudes and frequencies of resonance oscillations were used as informational parameters. The statistical analysis of the data showed the following parameters of the first resonance on the gain-frequency characteristics for pushing and non-pushing extremities respectively: resonance frequency 43.1 ± 2.24 and 45.1 ± 1.12 Hz; energy dissipation factor 2.2 ± 0.09 and 2.1 ± 0.08. These characteristics reflect stiffness of tendon-muscular complex and its interaction with surrounding tissues.

3. Diagnostical Criteria Description

The aim of a physician is the diagnostics of the tendon-muscular complex state. It means the finding out of the presence of injury and its location and also the definition of the kind and of the degree of injury. We have simulated the fresh (1-7 days after breaking) fracture of the tendon at the different distance from the heel bone [3] and made the comparison of the computer AFC of the injured tendon with the real curves obtained by the research complex. On the basis of their analysis a very detailed system of diagnostical criteria is developed. All of them are mathematically expressed from the values of resonance frequencies and amplitudes in the three foot positions. The most informative and reliable criteria of the acute Achilles tendon tear can be formulated at the next way.

1) Alterations of frequency-resonance range of the tendon-muscular complex in the injured and contralateral (healthy) extremity in flexion (bending), extension (straightening) and neutral foot position:

DW ^s0 = (W^s0_inj - W^s0_c/lat )/W^s0_c/lat
DW^sb = (W^sb_inj - W ^sb_c/lat ) / W^sb_c/lat ,

where W^s0_inj , W^s0_c/lat - difference of resonance frequencies in foot straightening and in neutral foot position for the injured and contralateral extremities; W^sb_inj , W^sb_c/lat - difference of resonance frequencies in foot straightening and in foot bending for the injured and contralateral extremities:

W^s0 = W^s- W^o , W^sb = W^s- W^b ,

where W^s , W⁰ , W^b - resonance frequencies in foot straightening, neutral and bending position for injured and contralateral extremeties (indexes "_inj" and "_c/lat" are not written for simplicity here and below) (Fig.2).

Fig 2: Recorded amplitude-frequency characteristics of the Achilles tendon-muscle system of the patient A.V.K-y, case-history #51, 30 days after breaking, distance from the calcaneus tubercle - 3 sm, tendon edges divergence (diastasis) - 2 sm, scar tissue in the tear area.

Diagnostic sign - is the narrowing of the resonance-frequency range in the following foot positions: extension-neutral and extension-flexion:

DW^s0< 0 , DW^sb < 0 .

2) Alterations of amplitude-resonance range of the tendon-muscular complex in the injured and contralateral (healthy) extremity in flexion (bending), extension (straightening) and neutral foot position:

DA^s0 = (A^s0_inj - A^s0_c/lat ) / A^s0_c/lat ,

DA^0b = (A^0b_inj - A^0b_c/lat ) / A^0b_c/lat ,

where A^s0_inj , A^s0_c/lat - difference of resonance amplitudes in foot straightening and in neutral foot position for the injured and contralateral extremities; A^0b_inj , A^0b_c/lat - difference of resonance amplitudes in neutral and bending foot position for the injured and contralateral extremities:

A^s0 = A^s - A⁰ , A^0b = A⁰ - A^b ,

where A^s , A⁰ , A^b - resonance amplitudes in foot straightening, neutral and bending position for injured and contralateral extremeties (Fig.2).

Diagnostic sign - is the narrowing of the extension-neutral amplitude range and the rise of the neutral-flexion amplitude range:

DA^s0 < 0 , D A^0b > 0 .

4) Alterations of the quantity of peaks on the resonance curves in the injured and contralateral (healthy) extremity in flexion (bending), extension (straightening) and neutral foot position:

Dn^b = (n^b_inj - n^b_c/lat ) / n^b_c/lat ,

Dn⁰ = (n⁰_nj - n⁰_c/lat ) / n⁰_c/lat ,

D n^s = (n^s_inj - n^s_c/lat ) / n^s_c/lat ,

where n^b_inj , n^b_c/lat , n⁰_nj , n⁰_c/lat , n^s_inj , n^s_c/lat - the number of peaks on the resonance curves in every foot position for the injured and contralateral extremities.

Diagnostic sign - smoothing of the resonance curve and decrease in the number of resonance peaks in the every foot position:

Dn^b < 0 , D n⁰ < 0 , Dn^s < 0 .

This sign is theoretically observed as smoothing of the numerically calculated AFC curves.

Reliability of presence of the tendon tear can be characterised by the total percent sum in all the diagnostic signs (or intencity S) which is calculated by the formulas:

S = DW^s0 + DW^sb - DA^0b + D A^s0 + Dn^b + D n⁰ + Dn^s

The higher this magnitude is, the more reliable is the Achilles tendon tear.

4. Results

We have applied the methods described for investigating the shanks of the fourteen patients with acute Achilles tendon tears in the Ivanovo war veteran hospital. All of them underwent the vibration examinations and the following surgery in the period from 1 to 5 days after tendon breaking. The tendon edges divergence (diastasis) averaged an one centimetre. The distance from the calcaneus tubercle was lied in the range 3-6 sm. The space in the tear area was occupied by a haemorrhage.

Table 1: The Achilles tendon resonance curves parametres for the clinical cases


As example, the resonance curves of a patient with acute subcutaneous left Achilles tendon tear are shown on the Fig.1. The results of applying the criteria system developed for the tendon fracture determination are presented in the Table 1, clinical case (a). It can be noted that the whole criteria described are fulfilled with a large value of the intencity S. So a physician can make a conclusion about the acute tear of the Achilles tendon.

Fig 1: Recorded amplitude-frequency characteristics of the Achilles tendon-muscle system of the patient S.V.B-v, case-history #60, 2 days after breaking, distance from the calcaneus tubercle - 5 sm, tendon edges divergence (diastasis) - 1 sm, space in the tear area is occupied by a haemorrhage.


We have also investigated the group of the sixteen patients with ancient fractures of the Achilles tendon (more than 1 month). The resonance curves of one patient from this research group are presented on the Fig.2, the numerical parametres of them are in the Table 1, clinical case (b). Despite the long time period after breaking, the resonance frequency and amplitude differences in the shank AFC's are obviouse, i.e. the dignostical signs D W^s0, D W^sb, D A^0b, DA^s0 are executed. The large absolute magnitude of diagnostic signs intensity S proves the Achilles tendon tear. But the number of resonance peaks seems to be equal for the injured and contralateral extremities what has been observed for the almost people from this research group.

5. Conclusion

The investigations carried out give a possibility to say that the elaborated method of diagnosing functional condition of the triceps on the basis of resonance qualities of the tissues under the influence of low-frequency local vibration allows to diagnose a subcutaneous Achilles tendon tear to an approximation of nineteen percent of reliability.
Thus, the elaborated method and automatic equipment for vibrodefectoscopy of the tendon-muscular complex of the lower leg allow to introduce into clinical practice other effective diagnostic signs of the tendon condition in the regime of local vibratory examination and predict different alterations of the amplitude-frequency characteristics of the complex in different types of injuries.

6. References

1. Korablev S.S., Shapin V.I., Philatov J.E. Vibrational diagnostics in Instrument-Constructions. Hemisphera, USA, 1989.
2. Maleshev I.V., Nozdrin M.A., Shapin V.A., Schavelev V.L. Research complex for vibrational diagnostics of the Achilles tendon. Patent of Russian Federation #2077266, Bulletin of Inventions #11, 1997.
3. L.B.Maslov, V.V.Krasnoschekov. Shank injury computer simulation, in Proc. 2nd Int. Conf. "Tools for Mathematical Modelling", June 14-19, 1999, pp. 75-76, Saint-Petersburg, Russia, 1999.

© AIPnD , created by NDT.net

|Home|    |Top|