Kinematic Symmetry Index: a method for quantifying the locomotion symmetry using kinematic data P Pourcelot, F Audigié, C Degueurce, Jm Denoix, D Geiger

To cite this version:

P Pourcelot, F Audigié, C Degueurce, Jm Denoix, D Geiger. Kinematic Symmetry Index: a method for quantifying the horse locomotion symmetry using kinematic data. Veterinary Research, BioMed Central, 1997, 28 (6), pp.525-538. ￿hal-00902500￿

HAL Id: hal-00902500 https://hal.archives-ouvertes.fr/hal-00902500 Submitted on 1 Jan 1997

HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Original article

Kinematic Symmetry Index: a method for quantifying the horse locomotion symmetry using kinematic data

P Pourcelot F Audigié C Degueurce JM Denoix1 D Geiger2

1 Biomécaniyue du cheval, lnra, École nationale vétérlunire d’Alf()rt, 7, ctvenue du G&dquo;t-de-Gaulle, 94704 Mni.sons-Alfbrl ceclex; 2 Laboratoire de mécanique physique, Université Petrls-Xll, avenue clu G&dquo;’-de-G(ilille, 94000 Créteil, /!!

(Received 15 May 1997; accepted 3l July 1997)

Summary - This study was conducted to evaluate a method for quantifying locomotion symmetry at trot in sound and lame . Using a 3D kinematic analysis system, the kinematics of the limb of sound and lame horses were recorded. The differences in motion between the left and right homologous joints were then quantified using a symmetry index based on an inter-correlation method. This method was used to calculate the symmetry indices of the vertical displacements and angle-time diagrams of the joints of each horse. In order to evaluate the sensitivity of this method of quantify- ing the locomotion symmetry, the symmetry indices of horses suffering from the three main types of (forelimb, hind limb and bilateral lamenesses) were compared with those calculated for a reference group of clinically sound horses. The symmetry indices calculated using this method were sensitive enough to distinguish different degrees of lameness. Except for symmetrical bilateral lame- ness, the indices obtained also allowed us to determine which of the fore or hind limbs were lame. The results of this study make it possible to consider potential applications of this method in research and clinical fields.

horse / kinematic / symmetry / lameness / trot

Résumé - Index de Symétrie Cinématique : une méthode de mesure de la symétrie de la loco- motion du cheval à partir de données cinématiques. L’objectif de cette étude est d’évaluer une méthode de mesure de la symétrie du trot de chevaux sains et boiteux. À l’aide d’un système d’ana- lyse cinématique 3D, les trajectoires des articulations des membres de chevaux sains et boiteux ont été enregistrées. Les différences de mouvement entre les articulations homologues droite et gauche ont ensuite été quantifiées à l’aide d’un index de symétrie basé sur une méthode d’inter-corrélation. Cette méthode a été utilisée pour calculer les indices de symétrie des décours verticaux et angu-

* Correspondence and reprints Tel: (33) 01 43 96 70 49; fax: (33) O1 43 96 31 62; e-mail: [email protected] laires des articulations de chaque cheval. Afin d’évaluer la sensibilité de cette méthode de mesure de la symétrie locomotrice, les indices de symétrie de chevaux souffrant des trois principaux types de boi- teries (antérieure, postérieure et bilatérale) ont été comparés à ceux d’une population de chevaux sains. Les indices de symétrie calculés à l’aide de cette méthode furent suffisamment sensibles pour distinguer différents degrés de boiterie. Sauf dans le cas de boiterie bilatérale symétrique, les indices obtenus permirent aussi de déterminer lesquels des membres antérieurs ou postérieurs étaient boiteux. Les résultats de cette étude permettent d’envisager l’application de cette méthode en recherche scien- tifique et clinique. cheval / cinématique / symétrie / boiterie / trot

INTRODUCTION placement-time and angle-time diagrams of the left and right limb joints. Its sensitiv- was evaluated the Evaluation of locomotion symmetry is a ity by comparing sym- indices of horses from the central part of the diagnosis of equine lame- metry suffering three main of lameness with those of ness. This clinical examination is however types essentially subjective. Different techniques a reference group of sound horses. have been used to quantify the locomotion symmetry of sound and lame horses. Merkens et al (1986, 1988, 1993) quanti- MATERIALS AND METHODS fied the ground reaction force symmetry of sound and lame horses at the walk and nor- Horses mal trot. Barrey et al (1995) evaluated the gait symmetry and regularity of trotting The reference group consisted of 13 sound horses using a belt with a mounted French Warmbloods from the Regiment de Cav- accelerometer. Kinematic techniques have alerie de la Garde R6publicaine. A detailed clin- also been used. Fredricson and Drevemo ical examination confirmed that each horse was free of lameness. (1972) showed that the correlation between clinically the kinematics of the extremity joints was The group of lame horses consisted of three strong between horses. May and Wyn-Jones lame French Warmbloods suffering from the (1987) and Buchner et al (1993) described three main types of lameness. Their degree of lameness was scored an clini- in the movements by experienced quantification procedures cian to the criteria used et al of the Kobluk et al according by hip. (1989) and Mar- (1993). tinez-del Campo et al ( 1991 ) compared the left and right angle-time diagrams. Recently, On the basis of clinical examination: Buchner et al evaluated (1995, 1996a, b) lame horse I presented a unilateral forelimb the kinematics of the limbs and calculated lameness due to navicular disease. It was mod- the symmetry indices of the trunk during an erately lame at trot (scored 2.0); induced lameness. However, no systematic lame horse 2 presented a bilateral foielimb of the locomotion study symmetry using lameness due to pain on the sole. It was severely kinematic data has been reported. lame at trot (scored 3.0);

The aim of this study was to describe and lame horse 3 presented a unilateral hind limb lameness due to an evaluate a method for quantifying locomo- injury to the third interosseous muscle. At trot it was lame tion symmetry in sound and lame horses spontaneous slightly (scored while after a flexion test kinematic data. A I .0) dynamic using left-to-right sym- it was severely lame (scored 3.0) during the first index was defined and metry computed. run and moderately lame (scored 2.0) during the This method was applied to the vertical dis- second run. Recording procedure Synchronization of the left and 3D reconstruction and right movements

Twenty-six markers were glued to the skin of A computer program was developed to analyse the animal, six on each forelimb (shoulder, elbow, the 3D kinematic data. In order for the left and carpus, , coronet and hoot) and seven on right trajectories of a pair of markers to be com- each hind limb (tuber coxae, great trochanter, pared and to calculate the symmetry indices, the stitle, tarsus, fetlock, coronet and hoot). Great movements of both left limbs of the horse with care was taken with regards to the symmetry of those of its right limbs were synchronized. This positioning the left and right markers. Four video synchronization was obtained by inter-correlat- cameras (50 Hz) were placed around a rubber ing the left and right longitudinal (X-axis) dis- examination track (Degueurce et al, 1996). These placements of the four hooves. The program con- were focused to image a field of view 5.50 m sidered the displacements of both left hooves as long (fig 1 The horses were led by a well-trained the reference and shifted up the right ones frame operator at a slow trot (3.2 m/s) and filmed untill by frame. Each time it calculated the coefficient at least five correct runs were made (Drevemo of correlation between the left and the right dis- et al, 1980). The films were digitized by a video placements (fig 2). This operation was repeated card with a resolution of 768 by 576 pixels and until the maximum value of the coefficient was the successive positions of the markers deter- reached. The calculation of the coefficient was mined. The 3D reconstruction of the trajectories performed using half the total number of frames: of the markers was calculated using the direct if there were 100 frames in the file, the program linear transformation method (Abdel-Aziz and would use, as references, the successive posi- Karara, 197 ).1 tions of both left hooves from frame number 25 to frame number 75. The first coefficient of cor- The highest value of these two maxima gave relation would be established using this refer- the number of frames by which both right limbs ence and the successive positions of both right might be shifted to obtain the best synchroniza- hooves from frame number 25 to 75 (fig 2, No 2). tion of the longitudinal displacements of both The result would be stored and the program pairs of hooves. This temporal synchronization would repeat the same operations with, now, the was applied to all the markers of both right limbs. successive positions of both right hooves from The other maximum gave another opportunity frames 26 to 76, then from frames 27 to 77, and for synchronization. It appeared after, or before, so on. Once the maximum value of the coeffi- another stride. The time interval between these cient was reached (fig 2, No 3), the same calcu- two maxima corresponded to the stride duration. lations were performed but, now, shifting down the right longitudinal displacements until the other maximum value of the coefficient was Calculation of the Kinematic reached (fig 2, No I). In our example, the first coefficient would be calculated with the longi- Symmetry Indices tudinal displacements of both right hooves from frames 24 to 74, then from frames 23 to 73, and In the following text, the term ’symmetry indice’ so on. refers to a pair of markers and the term ’syin- metry index’ refers to either the pair of fore or hind limbs.

The coefficient of determination at frame number i (r!2) between the left and right values of a kinematic variable calculated over one stride A value of I.0 indicates for duration is: perfect symmetry the measured variable.

Calculation of the Kinematic Symmetry Indexes The Kinematic Symmetry Index of the forelimbs (KSF) and the Kinematic Symmetry Index of the where NbF is the total number of frames in the hind limbs (KSH) of the kinematic variable were file; NbFS is the number of frames for a single computed by averaging the KSI of the fore and stride; Lj and R; are the left and right values of the hind limbs, respectively. kinematic variable at frame number j, MeanL and MeanR are, respectively, the means of the L, and the Rj between frame num- Kinematic variables studied ber (i) and frame number (i + NbFS). The symmetry indice of the kinematic variable The two kinematic variables studied in this paper was the mean of the coefficients were the vertical and (KSI) r2I displacement-time (fig 3) angle-time. For each joint, two KSI, one for the vertical Lame horse 3 presented a unilateral hind and one displacement (KSI,) for the joint angle limb lameness (fig 7). Its KSF indexes were were calculated the five (KSIA) by averaging similar to those of the sound horses but its trial values. KSHZ index was 0.71 as opposed to a stan- For each horse, four kinematic symmetry dard sound value of 0.88. All the KSIZ of indexes were two for the forelimbs calculated, the forelimbs were greater than two stan- and and two for the hind limbs (KSFZ KSFA) dard deviations below the mean of those of and were (KSHZ KSHA). They computed by the sound for the hind averaging the KSI of the fore and hind limbs, horses, whereas, respectively. limbs, only the stifle and the fetlock pre- sented this same characteristic. During the first run after the flexion test of lame horse 3 all the of the hind limbs were RESULTS (fig 8), KSIZ significantly lower than those of sound horses. The KSHZ index decreased from Figures 4 to 9 present the values of the KS 0.71 at spontaneous trot to 0.34. The KSFZ indices and indexes of the sound and lame index decreased from 0.92 to 0.85. This horses. the indices of the sound Assuming decrease was due to the KSIZ of the shoul- horses were the val- normally distributed, der and elbow, which were lower than 0.69. ues lower than two standard deviations During the second run (fig 9), the KSHZ below the mean of the sound ones < (P 0.05) index rose to 0.60 and the forelimb asym- were outside the 95% confidence interval. metry disappeared (KSFZ index went back Consequently they were not considered as to 0.93). sound values. For these abnormal values, a dark square is visible in the figures. DISCUSSION The means of the vertical displacement KSIZ of the sound horses (fig 4) ranged from This describes a method for 0.88 to 0.95 for the forelimbs with a KSFZ study quanti- index of 0.92 and from 0.82 to 0.95 for the fying the locomotion symmetry by calcu- indices between the left hind limbs with a KSHZ index of 0.88. All lating symmetry and values of a kinematic variable. the joint angle-time diagrams KSIA were right greater than 0.96 except for the fore and The critical part of this calculation is the hind coffins. synchronization of the movements of both left limbs of the horse with its right ones. Lame horse 1 suffered from a unilateral The reference variables used to obtain forelimb lameness The of the (fig 5). KSIZ the most suitable must sat- three markers of the forelimbs synchronization proximal isfy three conditions. They should be: were lower than two standard deviations

- below the mean of the sound horses. Its based on the most symmetrical kinematic variable of sound and lame horses; KSFZ and KSHZ indexes were 0.75 and 0.89, respectively. - representative of the whole locomotion;

- the most as A bilateral forelimb lameness was pre- discriminating possible. sent in lame horse 2 (fig 6). Its KSF index When trotting at constant speed and in a was not affected significantly, nevertheless straight line, the stride lengths of both right the KSIZ of the shoulder was lower than limbs of a sound or lame horse are neces- two standard deviations below the mean sarily very close to those of the two left KSIZ of the sound horses. The KSH indexes limbs (Peloso et al, 1993). Thus, the longi- and all the hind limb KSI were greater than tudinal displacements values of the lame those of the sound horses. horse markers remain symmetrical, as

opposed to the transversal and vertical ones. markers (Audigi6 et al, 1996). It represents To fulfil the second condition, it is necessary less than 2% of the values of the KS indices, to choose a set of longitudinal displacement except for the coffin joint angle where it values on both left and right limbs of the reaches 4ah. animal as reference. Furthermore, the more The real of this method is that distal the selected markers are located, the advantage the calculated indices are sensitive greater the acceleration readings are, and enough to between different of therefore the more discriminating the syn- distinguish degrees chronization becomes. Consequently, the lameness. Lame horse 3 presented an injury to the third interosseous muscle of the most suitable reference variables to syn- right hind limb. At the it shows a low chronize the movements of both lateral trot, degree of lameness 1.0). Its index bipeds are the longitudinal displacements (scored KSHZ of both hooves paired left and right. was 0.71 as opposed to a standard sound value of 0.88. The values of these indices As opposed to symmetry indices based were strongly affected by a dynamic flexion on the ratio of extreme or mean values, this test. During the first run (scored 3.0), the method takes into account the whole shape KSHZ index fell down to 0.34 inducing a of the curves. Nevertheless, it presents two light forelimb asymmetry with a KSFZ index main limitations. First, it cannot determine of 0.85. This forelimb lameness is observed the lame limb side. For example, lame horse on the proximal markers. During the sec- I presented an unilateral forelimb lameness ond run (scored 2.0), the hind limb lame- (scored 2.0). Its KSH indexes were similar ness is attenuated, the KSHZ index increases to those of sound horses but its KSFZ index to 0.60 and the forelimb asymmetry disap- was 0.75 as opposed to a standard sound pears. value of 0.92. It was apparent that the lame- The vertical indices are ness proceeded from the forelimbs, but more displacement lower but more sensitive than the investigations were necessary to determine generally ones. the second run after which forelimb was involved. Second, this joint angle During the flexion test, all the hind limb of method was unable to detect symmetrical KSIZ bilateral lamenesses. Lame horse 2 suffered lame horse 3 are significantly lower than the standard sound ones the from a bilateral forelimb lameness (scored although only 3.0); nevertheless, because of the lack of KSIA of the coffin joint is significantly affected. This lower be due locomotor asymmetries (Buchner et al, sensitivity may to two different causes. On the one hand, 1995), none of its KSF or KSH indexes was affected significantly. Once again, further the shape of the angle-time diagrams curves are smoother than the vertical analysis was required. displace- ment-time ones. On the other hand, the The resolution of the system and/or an lameness impact is lower on the shapes of asymmetrical placement between the left the joint angle-time diagrams curves than and right markers could affect the values of on the vertical displacement-time ones. The the KSI. However, these methodological KSIZ values of the tuber coxae, great errors do not alter the general shape of the trochanter and stifle are 0.12, 0. I 9 and 0.02, curves (Kadaba et al, 1989). Thus, they do respectively, during the first run when the not affect significantly the values of the hip KSIA stands at 0.98. It shows that the symmetry indices, because their calculation vertical displacements of the proximal left is based on a correlation method. The error and right markers are strongly asymmetrical of the vertical displacements and joint while the general shape of their associated angle-time diagrams has been evaluated rel- joint angle-time diagrams curves are unaf- ative to an asymmetrical placement of the fected. This analysis method of the locomotion Buchner HHF, Savelberg HHCM, Schamhardt HC, Barneveld A (1996a) Limb movement adaptations symmetry can be used with other gait ana- in horses with experimentally induced fore or hind- lysis variables. It is applicable within the limb lameness. Equine Vet J 28, 63-70 frame of a standard clinical lameness exa- Buchner HHF, Savelberg HHCM, Schamhardt HC, mination. For each joint, it provides the cli- Barneveld A (1996b) Head and trunk movement in horses with induced nician with an objective quantification of adaptations experimentally fore- or hind limb lameness. Vet J 28, 71-76 the level. Nevertheless further Equine symmetry Degueurce C, Dietrich G, Pourcelot P, Denoix JM, analyses with a higher number of lame Geiger D (1996) Three-dimensional kinematic tech- horses are required. This would make it pos- nique for evaluation of horse locomotion in out- sible to evaluate the of this method to door conditions. Med Biol Eng Comput 34, 249- ability 252 detect and the of subtle quantify degree Drevemo S, Dalin G, Fredricson I, G (1980) which have Hjert6n lameness, may potential appli- Equine locomotion: 1. The analysis of linear tem- cations in research and clinical studies. poral stride characteristics of trotting Standard- breds. Equine Vet J 12, 60-65 Fredricson I, Drevemo S (1972) Variations of resul- tant joint co-ordination patterns in fast-moving stan- ACKNOWLEDGMENTS dardbreds. Acta Vet Scand Suppl 37, 65-92 Kadaba MP, Ramakrishnan HK, Wootten ME, Gainey The authors wish to acknowledge their gratitude J, Gorton G, Cochran GVB (1989) Repeatability to P Perrot and B Bousseau for their important of kinematic, kinetic, and electromyographic data in normal adult J Res 7, 849-860 contributions. This study was supported by the gait. Orthop Institut national de la recherche Kobluk CN, Schnurr D, Horney FD, Sumner-Smith agronomique Dekleer Hearn TC and the Service des haras et de G, Willoughby RA, V, (1989) 1’equitation. Use of high-speed cinematography and computer generated gait diagrams for the study of equine hind limb kinematics. Equine Vet J 21, 48-58 REFERENCES Martinez-del Campo LJ, Kobluk CN, Greer N, Trent AM, Stoner LJ, Wickstrom L, Loch D (1991) The use of to Abdel-Aziz Karara HM Direct linear trans- high-speed videography generate YI, ( 1971 ) and for the formation from coordinates into angle-time angle-angle diagrams study comparator object- of locomotion. Vet Trau- coordinates in equine Comp Orthopaed space close-range photogrammetry. matol4, 120-1311 Proc Am Soc for Photogrammetry, Urbana, Illi- nois, January, 1-188 May SA, Wyn-Jones G (1987) Identification of hind- leg lameness. Equine Vet J 19, 185-188 Audigi6 F, Pourcelot P, Degueurce C, Denoix JM (1996) Effects of the asymmetrical placement of Merkens HW, Schamhardt HC, Hartman W, Kersjes AW Ground reaction force of Dutch skin markers in the kinematic assessment of the (1986) patterns Warmblood horses at normal walk. VetJ locomotion symmetry of the horse. Proc 3rd lnt Equine I 8, 207-2144 Workshop on Animal Locomotion, Saumur, France, May, 60 Merkens HW, Schamhardt HC, Hartman W, Kersjes AW ( 1988) The use of H(orse) INDEX: A method Back W, Barneveld A, van Weeren PR, van den Bogert of the reaction force of AJ (1993) Kinematic in analysing ground patterns gait analysis equine carpal lame and normal horses at the walk. lameness. Acta Anat 146, 86-89 gaited Equine Vet J 20,29-36 E, Auvinet B, Courouc6 A ( 1995) Gait evalua- Barrey Merkens HW, Schamhardt HC, van Osch GJVM, van tion of race trotters an accelerometric device. using den AJ Ground reaction force 156-160 Bogert (1993) pat- Equine Vet J Suppl 18, terns of Dutch Warmblood horses at normal trot. Buchner HHF, Kastner J, Girtler D, Knezevic PF Equine !f./25, 134-137 (1993) Quantification of hind limb lameness in the Peloso JG, Stick JA, Soutas-Little RW, Caron JC, horse. Acta Anat 146, 196-199 DeCamp CE, Leach DH ( 1993) Computer-assisted Buchner HHF, Savelberg HHCM, Schamhardt HC, three-dimensional gait analysis of amphotericin- Barneveld A (1995) Bilateral lameness in horses induced carpal lameness in horses. Am J Vet Res - a kinematic study. Vet Quart 17, 103-105 54,1535-1543