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Equine Veterinary Journal ISSN 0425-1644 DOI: 10.1111/evj.12378
Foot placement of the equine forelimb: Relationship between foot conformation, foot placement and movement asymmetry A. WILSON, R. AGASS, S. VAUX, E. SHERLOCK, P. DAY, T. PFAU and R. WELLER* Department of Clinical Science and Services, Royal Veterinary College, Hatfield, Hertfordshire, UK. *Correspondence email: [email protected]; Received: 25.04.14; Accepted: 30.09.14
Summary Reasons for performing study: Hoof conformation, foot placement and movement asymmetry are routinely assessed as part of the lameness examination. However, to date, few studies have described these parameters, or the interplay between them, in the general horse population. Objectives: To assess foot conformation and foot placement in the forelimbs of a group of general purpose horses and investigate the relationships between foot placement, foot conformation and movement asymmetry. Study design: Observational cross-sectional study. Methods: Forty-three horses were included in the study. Measurements were taken from photographs of each forelimb to assess foot conformation. Video footage was recorded simultaneously from perpendicular cameras at both walk and trot and used to categorise foot placement. Inertial sensor data were used to assess head movement asymmetry in trot. Results: There was a high degree of variation in foot placement between and within horses, but a ‘lateral heel’ placement was most common in walk and a ‘lateral’ placement most common in trot. Foot placement was associated with dorsal and palmar hoof angles but there was no relationship between foot placement and the other conformation parameters, nor with movement asymmetry. Moderate negative correlations were found between several of the conformation parameters and movement asymmetry. Conclusions: A relationship exists between foot conformation and movement asymmetry with decreasing hoof width and hoof length related to increasing amount of movement asymmetry. In the population of horses studied here – deemed to be ‘well functioning’ by their owners/riders – foot placement was found to be independent of movement asymmetry and, to a large extent, independent of foot conformation. Keywords: horse; conformation; foot placement; movement asymmetry
Introduction When examining a lame horse, veterinarians will assess hoof conformation, foot placement and movement asymmetry to gain insight into the nature of the lameness and its potential causes. Much has been written about the ‘ideal’ foot conformation. Regular trimming and shoeing attempt to enhance hoof balance by attending to hoof angle, length, mediolateral balance, sole thickness and interaction with the ground [1]. The rationale for this is that deviation away from symmetry leads to asymmetrical loading of the limb, with subsequent implications for performance, injury and lameness [2]. A number of studies have investigated these relationships in specific horse populations [3–5] but little has been written about the general horse population. Additionally, conformation is not static and will change with age, use and over the course of a shoeing interval [6–9]. The impact of differences in conformation on locomotion has not yet been fully elucidated.
Foot placement It is widely accepted that a well-balanced hoof should land flat on a hard surface [10,11], thereby distributing force uniformly across the sole. However, in the forelimbs, the foot is most commonly thought to land laterally [11,12], which may predispose to lameness in the digit as well as suspensory branch desmitis [11]. Toe first and heel first foot placement are said to compensate for palmar or toe pain respectively [11,13]. Thus, particular patterns of foot placement may be either a cause or consequence of lameness. Foot placement is also thought to be affected by conformation [11,14] and studies have investigated the effect of artificially altering hoof balance to assess the effect on locomotion [13,15]. However, the variation in foot placement in normal horses and how this relates to conformation and lameness has not been fully investigated.
Aims and hypotheses The aim of this study was to assess foot conformation and foot placement in the forelimbs of a group of horses considered to be ‘well functioning’ by their owners and to investigate the relationships between foot placement, foot conformation and movement asymmetry. It was hypothesised that: 1) Equine Veterinary Journal •• (2014) ••–•• © 2014 EVJ Ltd
foot conformation would not be significantly different between the left forelimb and the right forelimb; 2) foot placement would be consistent within a horse and not be significantly different between the left forelimb and the right forelimb; 3) a significant relationship would exist between foot conformation and foot placement; 4) a significant relationship would exist between movement asymmetry and foot conformation; and 5) a significant relationship would exist between movement asymmetry and foot placement.
Materials and methods Horses Ten out of the 43 horses were from the Royal Veterinary College teaching herd, not currently ridden; the remaining 33 horses were from private yards and all in current work without any perceived performance problems by the owners (see Supplementary Item 1 for details). Owners completed a brief questionnaire giving details of their horse’s age, height, sex, how often they are seen by a farrier (farriery interval) and when they were last seen by a farrier. There were 25 mares and 18 geldings and a range of ages (4–23 years) and heights (1.0–1.75 m) were included. Twenty-two horses were shod on the forelimbs, 21 were not.
Data collection Foot conformation: Three digital photographs were taken of each hoof. Each hoof was picked out and white tape applied to the dorsal-most aspect of the hoof wall (in line with toe clip, if present). Markers were applied to the medial and lateral heel bulbs, at the hairline of the most palmar aspect of each heel bulb. With the horse weightbearing, a Nikon J1 cameraa (F5.6, ISO-A 3200) was first positioned to capture a palmarodorsal view of the hoof, then to capture a lateromedial view of the hoof. The tape on the hoof wall was used to assess the correct positioning of the camera for the lateromedial view by subjectively evaluating the amount of tape that was visible from the marker placed on the dorsal-most aspect of the hoof wall. The hoof was held up and the camera aimed parallel to the sole, to capture
1
Foot placement, foot conformation and movement asymmetry
a solar view. A 10 pence coin for scale and the identification of the horse and limb were included in each photograph.
A. Wilson et al.
a)
Foot placement: Each horse was walked and then trotted over hard, level ground at its own natural pace, while being led either by its owner or an experienced handler. Simultaneous video recordings were taken from 2 views; side on and from behind. To capture mediolateral foot placement, a Nikon J1 cameraa (720p, 60 frames/s) was positioned on a tripod 0.5 m high, behind the horse and manually zoomed as the horse was led away from and towards the camera. To capture dorsopalmar foot placement, 4 Hero3 Black Edition camerasb (720p, 60 frames/s, narrow view) were positioned on blocks 2 m from the centre of the track, 4 m apart and with the lens at a height of 0.17 m. At the start of each recording, a loud noise was made to allow sound synchronisation of the videos to identify the same strides in the lateromedial and dorsopalmar views. Motion analysis: An MTx inertial sensorc was attached to the horse at the poll using a custom made velcro attachment that was fixed to the bridle or head collar. A surcingle was also fitted to the horse containing an Xbus unitc, which transmitted data from the sensor via a wireless connection to a laptop. The horse was led over a hard, flat, level surface first in walk and then in trot. This was repeated until at least 25 strides were captured in each gait, excluding any trials with anomalous events such as head tossing.
Horse’s name
b)
Data processing Foot conformation: The images were viewed using ImageJd software (version 1.47) and the following measurements were obtained using a digital ruler: diagonal hoof length (the length from the lateral heel bulb along the line of the frog to the furthest point of the toe), hoof width (the widest part of the sole, parallel to the heel bulbs), medial hoof width (from the point of the frog to the medial hoof wall, parallel to the heel bulbs), lateral hoof width (from the point of the frog to the lateral hoof wall, parallel to the heel bulbs), medial heel bulb height (from the hairline at the palmar most aspect of the medial heel bulb to the ground) and lateral heel bulb height (from the hairline at the palmar most aspect of the lateral heel bulb to the ground). The angle between the dorsal hoof wall and the ground and the palmar aspect of the hoof and the ground were also measured digitally. These measurements are shown in Figure 1. Using these measurements, the following ratios were calculated: heel height ratio (HHR) was calculated by dividing lateral heel height by medial heel height. The hoof symmetry ratio (HSR) was calculated by dividing the lateral hoof width by the medial hoof width. The diagonal hoof length to hoof width ratio (DHLHWR) was calculated by dividing the hoof length by the hoof width. The dorsal to palmar angle ratio (DPAR) was calculated by dividing the dorsal angle by the palmar angle. Foot placement: Videos were viewed using QuickTime Playere (version 10.2). The 2 videos for each horse were played back simultaneously, using the noise at the start of each trial for synchronisation. The videos were advanced frame by frame and mediolateral and dorsopalmar foot placement for each stride were simultaneously assessed. Mediolateral foot placement was categorised as either medial, lateral or flat. Dorsopalmar foot placement was categorised as either toe first, heel first or flat. Example excerpts from the captured videos showing different types of foot placement are shown in Figure 2. Combining these, overall foot placement for each stride was ascertained and categorised as heel, lateral heel, lateral, lateral toe, toe, medial toe, medial, medial heel or flat. Twelve strides were assessed for each forelimb, for each gait. Only strides where foot placement could be clearly seen in both views were included and only those strides where the horse was moving smoothly in the desired gait. Combining the data for the 12 strides, an overall classification of how a horse predominantly places each forelimb was made. If 9 or more out of the 12 strides had the same foot placement, this was taken as the predominant foot placement. If fewer than 9 strides had the same foot placement, the foot placement was classified as ‘mixed’. Motion analysis: Sensor data were processed following published protocols [16] and head symmetry values were calculated. In trot,
2
Palmar angle
Dorsal angle
Horse’s name
Medial heel height
Lateral heel height
20 mm c)
Sole width
Horse’s name
Lateral sole width
Medial sole width
Diagonal sole length 20 mm Fig 1: Photographs showing digital measurement of foot conformation parameters. a) lateral view, b) palmar view, c) solar view.
symmetry index (SI) from the poll was used to assess forelimb asymmetry: an SI of exactly 1 indicates symmetrical movement; an SI of 1 indicates left forelimb asymmetry. A horse is considered lame if the SI is 1.18, indicating right fore or left forelimb lameness respectively (thresholds derived from published treadmill data, introduced by Starke et al. [16]). Each forelimb was classified as either the limb that tended towards asymmetry or tended towards symmetry, depending on whether the asymmetry was attributed to that limb (i.e. SI 1 for left fore). A nondirectional version of SI was calculated by subtracting 1 from the SI value (rendering a value of 0 indicative of perfect symmetry) and then taking the absolute value. This effectively means that increasing values of nondirectional SI are related to increasing amounts of movement asymmetry. Equine Veterinary Journal •• (2014) ••–•• © 2014 EVJ Ltd
Foot placement, foot conformation and movement asymmetry
A. Wilson et al.
a)
b)
c)
d)
e)
f)
Fig 2: Pictures demonstrating a) lateral, b) flat, c) medial foot placement in dorsal view and d) heel, e) flat, f) toe first foot placement in lateral view.
Data analysis The Kolmogrov–Smirnov statistic was used to test the conformation parameters and SIs for normality (P
Equine Veterinary Journal ISSN 0425-1644 DOI: 10.1111/evj.12378
Foot placement of the equine forelimb: Relationship between foot conformation, foot placement and movement asymmetry A. WILSON, R. AGASS, S. VAUX, E. SHERLOCK, P. DAY, T. PFAU and R. WELLER* Department of Clinical Science and Services, Royal Veterinary College, Hatfield, Hertfordshire, UK. *Correspondence email: [email protected]; Received: 25.04.14; Accepted: 30.09.14
Summary Reasons for performing study: Hoof conformation, foot placement and movement asymmetry are routinely assessed as part of the lameness examination. However, to date, few studies have described these parameters, or the interplay between them, in the general horse population. Objectives: To assess foot conformation and foot placement in the forelimbs of a group of general purpose horses and investigate the relationships between foot placement, foot conformation and movement asymmetry. Study design: Observational cross-sectional study. Methods: Forty-three horses were included in the study. Measurements were taken from photographs of each forelimb to assess foot conformation. Video footage was recorded simultaneously from perpendicular cameras at both walk and trot and used to categorise foot placement. Inertial sensor data were used to assess head movement asymmetry in trot. Results: There was a high degree of variation in foot placement between and within horses, but a ‘lateral heel’ placement was most common in walk and a ‘lateral’ placement most common in trot. Foot placement was associated with dorsal and palmar hoof angles but there was no relationship between foot placement and the other conformation parameters, nor with movement asymmetry. Moderate negative correlations were found between several of the conformation parameters and movement asymmetry. Conclusions: A relationship exists between foot conformation and movement asymmetry with decreasing hoof width and hoof length related to increasing amount of movement asymmetry. In the population of horses studied here – deemed to be ‘well functioning’ by their owners/riders – foot placement was found to be independent of movement asymmetry and, to a large extent, independent of foot conformation. Keywords: horse; conformation; foot placement; movement asymmetry
Introduction When examining a lame horse, veterinarians will assess hoof conformation, foot placement and movement asymmetry to gain insight into the nature of the lameness and its potential causes. Much has been written about the ‘ideal’ foot conformation. Regular trimming and shoeing attempt to enhance hoof balance by attending to hoof angle, length, mediolateral balance, sole thickness and interaction with the ground [1]. The rationale for this is that deviation away from symmetry leads to asymmetrical loading of the limb, with subsequent implications for performance, injury and lameness [2]. A number of studies have investigated these relationships in specific horse populations [3–5] but little has been written about the general horse population. Additionally, conformation is not static and will change with age, use and over the course of a shoeing interval [6–9]. The impact of differences in conformation on locomotion has not yet been fully elucidated.
Foot placement It is widely accepted that a well-balanced hoof should land flat on a hard surface [10,11], thereby distributing force uniformly across the sole. However, in the forelimbs, the foot is most commonly thought to land laterally [11,12], which may predispose to lameness in the digit as well as suspensory branch desmitis [11]. Toe first and heel first foot placement are said to compensate for palmar or toe pain respectively [11,13]. Thus, particular patterns of foot placement may be either a cause or consequence of lameness. Foot placement is also thought to be affected by conformation [11,14] and studies have investigated the effect of artificially altering hoof balance to assess the effect on locomotion [13,15]. However, the variation in foot placement in normal horses and how this relates to conformation and lameness has not been fully investigated.
Aims and hypotheses The aim of this study was to assess foot conformation and foot placement in the forelimbs of a group of horses considered to be ‘well functioning’ by their owners and to investigate the relationships between foot placement, foot conformation and movement asymmetry. It was hypothesised that: 1) Equine Veterinary Journal •• (2014) ••–•• © 2014 EVJ Ltd
foot conformation would not be significantly different between the left forelimb and the right forelimb; 2) foot placement would be consistent within a horse and not be significantly different between the left forelimb and the right forelimb; 3) a significant relationship would exist between foot conformation and foot placement; 4) a significant relationship would exist between movement asymmetry and foot conformation; and 5) a significant relationship would exist between movement asymmetry and foot placement.
Materials and methods Horses Ten out of the 43 horses were from the Royal Veterinary College teaching herd, not currently ridden; the remaining 33 horses were from private yards and all in current work without any perceived performance problems by the owners (see Supplementary Item 1 for details). Owners completed a brief questionnaire giving details of their horse’s age, height, sex, how often they are seen by a farrier (farriery interval) and when they were last seen by a farrier. There were 25 mares and 18 geldings and a range of ages (4–23 years) and heights (1.0–1.75 m) were included. Twenty-two horses were shod on the forelimbs, 21 were not.
Data collection Foot conformation: Three digital photographs were taken of each hoof. Each hoof was picked out and white tape applied to the dorsal-most aspect of the hoof wall (in line with toe clip, if present). Markers were applied to the medial and lateral heel bulbs, at the hairline of the most palmar aspect of each heel bulb. With the horse weightbearing, a Nikon J1 cameraa (F5.6, ISO-A 3200) was first positioned to capture a palmarodorsal view of the hoof, then to capture a lateromedial view of the hoof. The tape on the hoof wall was used to assess the correct positioning of the camera for the lateromedial view by subjectively evaluating the amount of tape that was visible from the marker placed on the dorsal-most aspect of the hoof wall. The hoof was held up and the camera aimed parallel to the sole, to capture
1
Foot placement, foot conformation and movement asymmetry
a solar view. A 10 pence coin for scale and the identification of the horse and limb were included in each photograph.
A. Wilson et al.
a)
Foot placement: Each horse was walked and then trotted over hard, level ground at its own natural pace, while being led either by its owner or an experienced handler. Simultaneous video recordings were taken from 2 views; side on and from behind. To capture mediolateral foot placement, a Nikon J1 cameraa (720p, 60 frames/s) was positioned on a tripod 0.5 m high, behind the horse and manually zoomed as the horse was led away from and towards the camera. To capture dorsopalmar foot placement, 4 Hero3 Black Edition camerasb (720p, 60 frames/s, narrow view) were positioned on blocks 2 m from the centre of the track, 4 m apart and with the lens at a height of 0.17 m. At the start of each recording, a loud noise was made to allow sound synchronisation of the videos to identify the same strides in the lateromedial and dorsopalmar views. Motion analysis: An MTx inertial sensorc was attached to the horse at the poll using a custom made velcro attachment that was fixed to the bridle or head collar. A surcingle was also fitted to the horse containing an Xbus unitc, which transmitted data from the sensor via a wireless connection to a laptop. The horse was led over a hard, flat, level surface first in walk and then in trot. This was repeated until at least 25 strides were captured in each gait, excluding any trials with anomalous events such as head tossing.
Horse’s name
b)
Data processing Foot conformation: The images were viewed using ImageJd software (version 1.47) and the following measurements were obtained using a digital ruler: diagonal hoof length (the length from the lateral heel bulb along the line of the frog to the furthest point of the toe), hoof width (the widest part of the sole, parallel to the heel bulbs), medial hoof width (from the point of the frog to the medial hoof wall, parallel to the heel bulbs), lateral hoof width (from the point of the frog to the lateral hoof wall, parallel to the heel bulbs), medial heel bulb height (from the hairline at the palmar most aspect of the medial heel bulb to the ground) and lateral heel bulb height (from the hairline at the palmar most aspect of the lateral heel bulb to the ground). The angle between the dorsal hoof wall and the ground and the palmar aspect of the hoof and the ground were also measured digitally. These measurements are shown in Figure 1. Using these measurements, the following ratios were calculated: heel height ratio (HHR) was calculated by dividing lateral heel height by medial heel height. The hoof symmetry ratio (HSR) was calculated by dividing the lateral hoof width by the medial hoof width. The diagonal hoof length to hoof width ratio (DHLHWR) was calculated by dividing the hoof length by the hoof width. The dorsal to palmar angle ratio (DPAR) was calculated by dividing the dorsal angle by the palmar angle. Foot placement: Videos were viewed using QuickTime Playere (version 10.2). The 2 videos for each horse were played back simultaneously, using the noise at the start of each trial for synchronisation. The videos were advanced frame by frame and mediolateral and dorsopalmar foot placement for each stride were simultaneously assessed. Mediolateral foot placement was categorised as either medial, lateral or flat. Dorsopalmar foot placement was categorised as either toe first, heel first or flat. Example excerpts from the captured videos showing different types of foot placement are shown in Figure 2. Combining these, overall foot placement for each stride was ascertained and categorised as heel, lateral heel, lateral, lateral toe, toe, medial toe, medial, medial heel or flat. Twelve strides were assessed for each forelimb, for each gait. Only strides where foot placement could be clearly seen in both views were included and only those strides where the horse was moving smoothly in the desired gait. Combining the data for the 12 strides, an overall classification of how a horse predominantly places each forelimb was made. If 9 or more out of the 12 strides had the same foot placement, this was taken as the predominant foot placement. If fewer than 9 strides had the same foot placement, the foot placement was classified as ‘mixed’. Motion analysis: Sensor data were processed following published protocols [16] and head symmetry values were calculated. In trot,
2
Palmar angle
Dorsal angle
Horse’s name
Medial heel height
Lateral heel height
20 mm c)
Sole width
Horse’s name
Lateral sole width
Medial sole width
Diagonal sole length 20 mm Fig 1: Photographs showing digital measurement of foot conformation parameters. a) lateral view, b) palmar view, c) solar view.
symmetry index (SI) from the poll was used to assess forelimb asymmetry: an SI of exactly 1 indicates symmetrical movement; an SI of 1 indicates left forelimb asymmetry. A horse is considered lame if the SI is 1.18, indicating right fore or left forelimb lameness respectively (thresholds derived from published treadmill data, introduced by Starke et al. [16]). Each forelimb was classified as either the limb that tended towards asymmetry or tended towards symmetry, depending on whether the asymmetry was attributed to that limb (i.e. SI 1 for left fore). A nondirectional version of SI was calculated by subtracting 1 from the SI value (rendering a value of 0 indicative of perfect symmetry) and then taking the absolute value. This effectively means that increasing values of nondirectional SI are related to increasing amounts of movement asymmetry. Equine Veterinary Journal •• (2014) ••–•• © 2014 EVJ Ltd
Foot placement, foot conformation and movement asymmetry
A. Wilson et al.
a)
b)
c)
d)
e)
f)
Fig 2: Pictures demonstrating a) lateral, b) flat, c) medial foot placement in dorsal view and d) heel, e) flat, f) toe first foot placement in lateral view.
Data analysis The Kolmogrov–Smirnov statistic was used to test the conformation parameters and SIs for normality (P
