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Metacarpophalangeal and phalangeal joint kinematics in horses shod with hoof caulks
Refereed
METACARPOPHALANGEALAND PHALANGEAL JOINT KINEMATICS IN HORSES SHOD WITH HOOF CAULKS K.N. Thompson, PhD; and L.S. Herring, MSc
SUMMARY
The application of hoof caulks to horseshoes influenced the stride kinematics of horses exercising on a treadmill. Metacarpophalangeal andphalangealjoint angles were changed when four 1/4 inch caulks were placed in a balanced manner on the bearing surface of the shoe. The dorsal metacarpophalangeal joint angle decreased (P<.05) and the dorsal phalangeal joint angle increased (P<.05) for all parts of the stance phase (impact, mid-stance, lift-off) when hoof caulks were added to the horseshoe. In addition, both the metacarpophalangeal and phalangeal joint angles in the transverse plane decreased (P<.05) when hoof caulks were placed in the horseshoe. The decrease in these joint angles caused the lower limb to take on a limb configuration similar to a varus limb. No differences (P>.05) in stride length, stride frequency or stance duration due to the caulks were observed. The use of hoof caulks changed limb configuration in a way which might change the forces placed on the joint surface, or on the tendinous/ligamentous structures in the lower limb.
INTRODUCTION
Quadrupedal locomotor patterns are influenced by many factors. One common technique used to modify Authors' address: University of Kentucky, Department of Veterinary Science, Maxwell Gluck Equine Research Center, Lexington, 40546-0099, USA. Acknowledgments: The investigation reported in this paper (#92.4-226) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director.
Volume 14, Number 6, 1994
stride in the horse is through different farriery modifications which alter limb motion. Alterations in the dorsal hoof wall-pastern axis have been shown to affect both temporal and spatial characteristics of the walk, trot and canter 1,e as well as the angle of hoof at ground impact. The angle of the hoof at ground impact is important in the distribution of ground reaction forces during the stance phase. 1,s Clayton, t also reported that breakover time and the number of toe-first impacts were increased in horses with an abnormal hoof wall-pastern axis. However, stride length did not change with the angle of the hoof. t Several other reports suggested that similar changes in hoof angle predispose the horse to lameness. 4,s,6,7 There is little scientific evidence available on the influence that different types of traction devices (toe grabs, heel caulks) have upon locomotor patterns. Many different traction devices are used, most of which are aimed at increasing the coefficient of friction between the horse's foot and ground. Rooney,3 suggested that all traction devices increased the friction between ground and foot, and decreased sliding of the foot during the stance phase. Forsell,8 hypothesized that toe grabs increased tension in tendons and ligaments by decreasing the dorsal metacarpophalangeal and dorsal phalangeal joint angles during the stance phase. In a study which measured the effect of traction devices, Nilsson et al., 9 reported that toe grabs and caulks placed only on the heel did not alter step height or the slide of the horse's foot on the ground. However, toe grabs were found to decrease the dorsal phalangeal joint angle in both fore and hind limbs, but they did not affect the dorsal metacarpophalangeal angle. These authors also reported that caulks on the heel increased dorsal metacarpophalangeal and phalangeal joint angles. 319
The purpose of this study was to examine the effect of hoof caulks (without changing hoof orientation) on metacarpophalangeal joint motion of horses exercising on a high speed treadmill. This information would help to better understand the use of traction devices in the equine athlete.
A=
M A T E R I A L S AND M E T H O D S
This study was conducted as a randomized complete block experiment. Six mature Thoroughbred horses ranging in wither height from 1.54-1.66 m and in body weight from 420-525 kg were used. The horses were obtained from a local riding stable and kept on pasture for 90 to 120 days prior to the start of the experiment. All horses did not have any gross conformational defects in the lower limb and were evaluated subjectively by investigators each day of the training and data collection period for clinical signs of lameness. During this study no obvious unsoundness occurred. The horses were adapted to a high speed treadmill and exercised 5 days per week for 12 weeks prior to the start of data collection. The daily training program consisted initially of a 400 m walk and a 400 m trot. The walking and trotting distance was increased each week thereafter. A 200 m canter was added after the second week and the distance cantered was increased in the subsequent weeks of the training period. The treadmill velocities were 1.8, 4.0, 7.0 m/s for the walk, trot and canter. The final training program consisted of 600 m of walking, 1000 m of trotting and 600 m of cantering. At the end of the training period, the horses were filmed at the walk (1.8 m/s), trot (4.0 m/s), canter (7.0 m/ s) and gallop (10.0 m/s). Both left and right lead limbs were filmed at the canter and gallop. The horses were filmed with two high speed black and white cameras a at a filming rate of 200 Hz. Each camera was placed lateral and oblique to the treadmill, 3 m apart and 5.5 m from the approximate midpoint of the exercising horse. A calibration structure consisting of 20 non-coplanar control points with known coordinates was used to define the volume of space in which the horses worked. Great care was taken to ensure that the calibration volume was as precise as possible and recalibrated if the residuals from the calibration were higher than the residuals from the data collection. An adaptation of the direct linear transformation method 1° was used to define the three-dimensional space. High gain retro-reflective circular (1.9 cm diameter) tape markers b were placed on each foreleg at the approximate midpoint of the third metacarpal bone, the approximate center of rotation of the metacarpophalangeal joint and the approximate midpoint of the hoof wall.-Markers were placed on the side of the limb facing the camera (lateral for the left limb and medial for the right limb). Eight aNACIncorporated, Tokyo,Japan. 1~3MCompany,St. Paul, Minnesota. 320
Figure 1, Diagram of the placement of the hoof caulks and blanks on the bearing surface of the horseshoe, A) top view; B) side view.
consecutive strides were collected from each gait after the horses had settled into the gait for approximately 60 seconds. Data from the right and left limbswere combined for the walk and trot. Data were analyzed with an autodigitizing motion analysis system.e Displacement data were smoothed using a non-recursive moving average filter with a cut-off frequency of 15 Hz. This study consisted of two groups of horses wearing two types of horseshoes. Each shoe had initially been tapped with four holes, one hole at each heel and two at the toe (Figure 1). For the first treatment small metal blanks were inserted into each tapped hole of the horseshoes. In the second treatment 1/4 inch hoof caulks were inserted into each tapped hole of the horseshoes. The hoof caulks were of equal lengths and when placed in the horseshoe did not change the orientation of the hoof with the treadmill. The blanks were flush with the bearing surface of the horseshoe and were equal in weight to the hoof caulks. Stride length, stride frequency, stance duration, phalangeal (PH)joint angle, and metacarpophalangeal (MCP) joint angle were recorded. The PH angle was defined as the angle that the segment between the hoof and the approximate center of rotation of the metacarpophalangeal joint made with the treadmill. The metacarpophalangeal joint angle was defined as the angle between the third metacarpal segment (segment between the third metacarpal and center of MCP joint) and the phalangeal segment (segment between the hoof and center of MCP joint). Angular displacements of the MCP angle and PH angle were de¢EV3D,MotionAnalysisCorporation,Santa Rosa,California. JOURNAL OF EQUINE VETERINARY SCIENCE
Table 1. Mean (_+SD) stride length (SL)*, stride frequency (SF)** and stance duration (ST)*** in horses exercising with and without hoof caulks. SL Gait Walk Trot Canter Gallop * Meters/stride **Strides/second Seconds
SF
ST
Flat
Caulk
Flat
Caulk
2.1(.3) 2.8(.3) 3.9(.3) 5.3(.3)
2.1(.2) 2.8(.2) 4.0(.2) 5.4(.3)
1.0(.1) 1.5(.3) 1.8(.1) 1.9(.1)
1.0(.1) 1.5(.1) 1.8(.1) 1.9(.1)
scribed in terms of the three-dimensional axis system through which the horse moved. The horizontal axis was X, the vertical axis was Z and the perpendicular intersection of the two was the Y axis. Dorsal joint angles were defined in the sagittal plane and medial joint angles were defined in the transverse plane. The joint angles were measured at three points of the stride; 1) impact, 2) midstance and 3) lift-off. Impact and lift-off with the treadmill were determined from the vertical displacement of the marker on each hoof wall. This was also used to determine the stance phase for each limb. Mid-stance was defined to be the point when the third metacarpal bone was perpendicular to the treadmill. These stride parameters were chosen based upon their importance to load bearing and structural support while the limb was in contact with the treadmill. All analyses of variance procedures were performed using the GLM procedure of SAS, tl appropriate for a repeated measures design. The whole plot was the shoeing treatment used, and stride within a gait was used as the repeated measures effect. 12 The wide variation in MCP and PH joint angular changes were primarily due to the small sample size, however, differences due to treatment were still observed. To test differences due to the shoeing treatment the residual error was used.
Flat
Caulk
.54(.08) .20(.05) .14(.01) .12(.01)
.55(.06) .22(.02) .14(.02) .11(.01)
RESULTS When the hoof caulks were placed in the horseshoe, many of the kinematic measures made in this study were changed. However, stride length, stride frequency and stance duration were not changed (P>.05) with the addition of hoof caulks (Table 1). In the XZ plane (sagittal) the dorsal MCP joint angle was in most cases less (P<.05) for horses shod with hoof caulks than those shod with flat shoes at impact, midstance and lift-off (Table 2). The decrease in this angle indicated that the MCP joint was extended more during the stance phase for horses shod with hoof caulks than those shod normally. The greater joint extension was observed for most of the gaits which were filmed. A greater degree of MCP joint extension increased tendon elongation and the strains placed on flexor tendons and the suspensory ligament during the stance phase .t3 In the YZ plane (transverse) the MCP joint angle was in most cases less (P<.05) for the gallop during impact, mid-stance and lift-off in horses shod with caulks than for those shod normally (Table 3). The angular change during the stance phase could have been related to the greater amount of MCP joint extension which was observed in the
Table 2. Mean (_+SD) metacarpophalangeal joint angles in the sagittal plane (XZ) of horses exercising with and without hoof caulks. Flat
Impact Caulk
Mid-stance Flat Caulk
Gait Walk 157(11) 159(8) 149a(12) Trot 158a(11) 153b(8) 135a(15) Canter, lead 158(9) 158(7) 125(5) Canter,trail 152(9) 152(8) 125a(5) Gallop,lead 165a(16) 158b(11) 128a(13) Gallop,trail 157a(13) 152b(9) 131a(12) a,bMeansin the same row withinheadingwithouta commonsuperscriptdiffer (P<.05). Volume 14, Number 6, 1994
141b(5) 130b(4) 126(6) 126b(5) 123b(8) 124b(9)
Lift-off Flat Caulk 146a(5) 146a(18) 145(19) 135a(7) 134(11) 139a(19)
144b(6) 141 b(8) 142(17) 140b(14) 134(13) 133b(14)
321
Table 3. Mean (_+SD) metacarpophalangeal joint angles in the transverse plane (YZ) of horses exercising with and without hoof caulks. Impact
Mid-stance Flat Caulk
Flat Caulk Gait Walk 179(5) 179(6) 177(7) Trot 179(9) 179(6) 177(11) Canter,lead 179(6) 179(6) 178(9) Canter,trail 177(10) 177(10) 173(9) Gallop,lead 178a(10) 175b(8) 178(12) Gallop,trail 18@(14) 178b(9) 181a(12) a'bMeansin the same row withinheadingwithouta commonsuperscriptdiffer (P<.05). horses shod with hoof caulks. In the XZ plane (sagittal) the dorsal PH joint angle was in most cases larger (P<.05) at impact, mid-stance and liftoff for horses shod with hoof caulks than for those shod normally (Table 4). This was observed in all gaits except for the canter and indicated more flexion of the PH joint in horses shod with hoof caulks. In the transverse plane the PH joint angle was in most cases less (P<.05) with the addition of hoof caulks. This represented a shift laterally of about 2-3 ° during all parts of the stance phase and at all gaits except the gallop when the hoof caulks were added (Table 5). In this study, the phalangeal segment was aligned differently with other skeletal structures in the lower limb when horses were shod with hoof caulks than when they were shod normally.
DISCUSSION
The hoof caulks used in this study were balanced across the surface of the horseshoe. The hoof caulks did not alter stride length, stride frequency or stance duration in horses exercising on a treadmill. Horses wearing shoes with hoof caulks showed a decreased dorsal MCP joint angle at impact, mid-stance
178(8) 178(10) 177(7) 174(7) 177(11) 175b(8)
Lift-off Flat
Caulk
178(5) 178(12) 180a(11) 175(7) 183(10) 162a(11)
178(8) 179(7) 175b(13) 177(9) 178(8) 177b(7)
and lift-off in the sagittal plane. The increase in MCP joint extension was observed for most of the gaits measured in this study and led to a 5-8 ° increase in joint extension. Nilsson et al, 9 reported that the use of toe grabs alone did not change the dorsal metacarpophalangealjoint angle, but when heel caulks were used they increased the dorsal metacarpophalangeal joint angle. They also reported toe grabs decreased the dorsal phalangeal angle, while heel caulks increased the dorsal phalangeal angle. Overextension of the metacarpophalangeal joint has been suggested3,14,15 to be related to several musculo-skeletal diseases (navicular disease, sesamoid bone fracture, degenerative joint disease, tendon tearing). In the present study, the decrease in dorsal MCP joint angle at impact was caused by the use of hoof caulks and the angular change was maintained during the entire stance phase. This differed from the results of Nilsson et al., 9 and could be due to the balanced placement of the hoof caulks over the surface of the horseshoe. The use of toe grabs or heel caulks changes the orientation of the hoof with the ground, which because of the effective change in hoof angle effects joint kinematics differently. The use of hoof caulks at faster velocities than those used in the present study may also cause a greater amount of joint extension or even overextension than was observed in this study.
Table 4. Mean (-+SD) phalangeal joint angles in the sagittal plane (XZ) of horses exercising with and without hoof caulks. Impact Caulk
Mid-stance Flat Caulk
Flat Gait Walk 125a(9) 130b(7) 122a(9) Trot 126a(8) 133b(4) 13 la(10) Canter,lead 137(6) 136(4) 145(5) Canter,trail 136(5) 135(5) 145(5) Gallop,lead 132a(9) 140b(6) 141a(12) Gallop,trail 134a(7) 138b(6) 138a(13) a'bMeansin the same row withinheadingwithouta common superscriptdiffer (P<.05). 322
128b(5) 139b(4) 143(6) 143(4) 146b(8) 145b(9)
Lift-off Flat 100(10) 94a(12) 100a(13) 104(9) 107(11) 96a(18)
Caulk 97(6) 103b(7) 104b(10) 102(8) 106(11) 105b(15)
JOURNAL OF EQUINE VETERIN~:W SCIENCE
Table 5, Mean (± SD) phalangeal joint angles in the transverse plane (YX) of horses exercising with and without hoof caulks. Impact
Mid-stance
Lift-off
Flat
Caulk
Flat
Caulk
Flat
Gait Walk
96a(3)
94b(4)
96a(5)
93b(4)
95a(2)
92b(4)
Trot
97a(4)
94b(5)
97a(5)
95b(4)
96a(5)
94b(6)
Canter,lead
95a(4)
94b(3)
95a(3)
93b(4)
95a(5)
93b(5)
Canter,trail
95(5)
94(5)
95(3)
94(5)
95a(4)
93b(6)
94(4) 95(5)
95(5) 95(6)
95(4) 94(5)
Gallop,lead 94(6) 95(4) 95(7) Gallop,trail 93(5) 94(5) 96(6) a.bMeansin the same row within headingwithouta common superscriptdiffer (P<.05).
When the MCP angle was examined in the transverse plane a 3-6 ° change was noted at the canter and gallop when hoof caulks were used on the horseshoes. This caused the lower limb to resemble a varus MCP joint configuration during the stance phase. This joint configuration would presumably lead to increased stresses placed on the medial sides of the joint, and increased incidence of cartilage damage to those areas. The dorsal PH joint angle was greater in the horses shod with hoof caulks when compared to those shod normally. The dorsal PH joint angle followed a similar pattern for each gait and through most of the stance phase as it increased approximately 4-9 ° with the addition of hoof caulks to the horseshoes. This was similar to that described by Nilsson et alp for heel caulks, but differed from their observations for toe grabs. Forsell, 8 suggested that smaller dorsal phalangeal angles during stance increased tension in the deep flexor tendon which increased the pressure acting on the navicular bone. The greater dorsal PH joint angle observed in the present study likely then decreased the strain in the deep flexor tendon and decreased the forces placed upon the surface of the navicular bone during the stance phase. The larger dorsal PH joint angle may partially offset the increase in deep flexor tendon strain which occurred when MCP joint extension increased with the use of hoof caulks. If strain on the deep flexor tendon is increased, a progressive degeneration of the cartilaginous tissue in contact with the deep flexor tendon occurred, t6 These results suggest that hoof caulks do change orientation of the metacarpophalangeal and phalangeal joints during different portions of the stance phase. As a result, the change in limb configuration may lead to uneven loading patterns across the metacarpophalangeal joint surface which can increase the incidence of joint damage. Further study is needed to determine the specific effects that different types and configurations of tractions devices have upon limb orientation.
Volume 14, Number 6, 1994
Caulk
REFERENCES
1. Clayton HM: The effect of an acute hoof wall angulation on the stride kinematics of trotting horses. Eq VetJ 9:86-90, 1990a. 2. Clayton HM: The effect of acute angulation of the hind hooves on diagonal synchrony of trotting horses. Eq VetJ9:91-94, 1990a. 3. Rooney JR: Biomechanics of Lameness in Horses. Huntington: Kreiger Publishing Company, pp 115-196, 1969. 4. Bushe T, Turner TA, Poulos PW, Harwell NM: The effect of hoof angle on coffin, pastern and fetlock joint angles. Proc 33rd Am Assoc Eq Pract, pp 729-738, 1987. 5. Rooney, JR: The angulation of the forefoot and pastern of the horse. J Eq Vet Sc/ 4:138-143,1984. 6. Butler KD: The Principles of Horseshoeing II. Maryville: Doug Butler Publisher, pp 319-363, 1985. 7. Klobluk CN, Robinson RA, Gordon BJ, Clanton CJ, Trent AM, Ames TR: The effect of conformation and shoeing:A cohort study of 95 Thoroughbred racehorses. Proc 35th Am Assoc Eq Pract, pp 259-274, 1989. 8. Forsell EG: The diagnosis of lameness. Royal Vet. College Lectures, Stockholm, Sweden,1943, (as cited in Nilsson et al., 1973) 9. Nilsson G, Fredricson I, Drevemo S: Some procedures and tools in the diagnostics of distal equine lameness. Acta Vet Scand Supp144:63-79, 1973. 10. Marzan GT, Karara HM: A computer program for direct linear transformation solution of the collinearity condition, and some applications of it. Symposium on Close Range Photogrammetric Systems, pp 420-476, 1975. 11. SAS. Users' Guide: Statistics. Cary: SAS Institute Inc., 1985. 12. Steel RGD, Torrie JD: Principles and Procedures of Statistics: A Biometrica/Approach. New York: McGraw-Hill Book Company, 1980. 13. Riemersma DJ, Van Den Bogert AJ, Schamhardt HC, Hartman, W: Kinetics and kinematics of the equine hind limb: In vivo tendon strain and joint kinematics. Am J Vet Res 49:13531359, 1988. 14. Stashak TS: Adams' Lameness in Horses. 4th ed. Philadelphia: Lea and Febiger. pp 796-812, 1987. 15. Bramlage LR, Bukowiecki CW, Gabel AA: The effect of training on the suspensory apparatus of the horse. Proc, 35th Am Assoc Eq Pract, pp 245-247, 1989. 16. Thompson KN, RooneyJR, Petrites-Murphy MB: Considerations on the pathogenesis of navicular disease. J Eq Vet Sci 11:4-8, 1991.
..Y~'~
METACARPOPHALANGEALAND PHALANGEAL JOINT KINEMATICS IN HORSES SHOD WITH HOOF CAULKS K.N. Thompson, PhD; and L.S. Herring, MSc
SUMMARY
The application of hoof caulks to horseshoes influenced the stride kinematics of horses exercising on a treadmill. Metacarpophalangeal andphalangealjoint angles were changed when four 1/4 inch caulks were placed in a balanced manner on the bearing surface of the shoe. The dorsal metacarpophalangeal joint angle decreased (P<.05) and the dorsal phalangeal joint angle increased (P<.05) for all parts of the stance phase (impact, mid-stance, lift-off) when hoof caulks were added to the horseshoe. In addition, both the metacarpophalangeal and phalangeal joint angles in the transverse plane decreased (P<.05) when hoof caulks were placed in the horseshoe. The decrease in these joint angles caused the lower limb to take on a limb configuration similar to a varus limb. No differences (P>.05) in stride length, stride frequency or stance duration due to the caulks were observed. The use of hoof caulks changed limb configuration in a way which might change the forces placed on the joint surface, or on the tendinous/ligamentous structures in the lower limb.
INTRODUCTION
Quadrupedal locomotor patterns are influenced by many factors. One common technique used to modify Authors' address: University of Kentucky, Department of Veterinary Science, Maxwell Gluck Equine Research Center, Lexington, 40546-0099, USA. Acknowledgments: The investigation reported in this paper (#92.4-226) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director.
Volume 14, Number 6, 1994
stride in the horse is through different farriery modifications which alter limb motion. Alterations in the dorsal hoof wall-pastern axis have been shown to affect both temporal and spatial characteristics of the walk, trot and canter 1,e as well as the angle of hoof at ground impact. The angle of the hoof at ground impact is important in the distribution of ground reaction forces during the stance phase. 1,s Clayton, t also reported that breakover time and the number of toe-first impacts were increased in horses with an abnormal hoof wall-pastern axis. However, stride length did not change with the angle of the hoof. t Several other reports suggested that similar changes in hoof angle predispose the horse to lameness. 4,s,6,7 There is little scientific evidence available on the influence that different types of traction devices (toe grabs, heel caulks) have upon locomotor patterns. Many different traction devices are used, most of which are aimed at increasing the coefficient of friction between the horse's foot and ground. Rooney,3 suggested that all traction devices increased the friction between ground and foot, and decreased sliding of the foot during the stance phase. Forsell,8 hypothesized that toe grabs increased tension in tendons and ligaments by decreasing the dorsal metacarpophalangeal and dorsal phalangeal joint angles during the stance phase. In a study which measured the effect of traction devices, Nilsson et al., 9 reported that toe grabs and caulks placed only on the heel did not alter step height or the slide of the horse's foot on the ground. However, toe grabs were found to decrease the dorsal phalangeal joint angle in both fore and hind limbs, but they did not affect the dorsal metacarpophalangeal angle. These authors also reported that caulks on the heel increased dorsal metacarpophalangeal and phalangeal joint angles. 319
The purpose of this study was to examine the effect of hoof caulks (without changing hoof orientation) on metacarpophalangeal joint motion of horses exercising on a high speed treadmill. This information would help to better understand the use of traction devices in the equine athlete.
A=
M A T E R I A L S AND M E T H O D S
This study was conducted as a randomized complete block experiment. Six mature Thoroughbred horses ranging in wither height from 1.54-1.66 m and in body weight from 420-525 kg were used. The horses were obtained from a local riding stable and kept on pasture for 90 to 120 days prior to the start of the experiment. All horses did not have any gross conformational defects in the lower limb and were evaluated subjectively by investigators each day of the training and data collection period for clinical signs of lameness. During this study no obvious unsoundness occurred. The horses were adapted to a high speed treadmill and exercised 5 days per week for 12 weeks prior to the start of data collection. The daily training program consisted initially of a 400 m walk and a 400 m trot. The walking and trotting distance was increased each week thereafter. A 200 m canter was added after the second week and the distance cantered was increased in the subsequent weeks of the training period. The treadmill velocities were 1.8, 4.0, 7.0 m/s for the walk, trot and canter. The final training program consisted of 600 m of walking, 1000 m of trotting and 600 m of cantering. At the end of the training period, the horses were filmed at the walk (1.8 m/s), trot (4.0 m/s), canter (7.0 m/ s) and gallop (10.0 m/s). Both left and right lead limbs were filmed at the canter and gallop. The horses were filmed with two high speed black and white cameras a at a filming rate of 200 Hz. Each camera was placed lateral and oblique to the treadmill, 3 m apart and 5.5 m from the approximate midpoint of the exercising horse. A calibration structure consisting of 20 non-coplanar control points with known coordinates was used to define the volume of space in which the horses worked. Great care was taken to ensure that the calibration volume was as precise as possible and recalibrated if the residuals from the calibration were higher than the residuals from the data collection. An adaptation of the direct linear transformation method 1° was used to define the three-dimensional space. High gain retro-reflective circular (1.9 cm diameter) tape markers b were placed on each foreleg at the approximate midpoint of the third metacarpal bone, the approximate center of rotation of the metacarpophalangeal joint and the approximate midpoint of the hoof wall.-Markers were placed on the side of the limb facing the camera (lateral for the left limb and medial for the right limb). Eight aNACIncorporated, Tokyo,Japan. 1~3MCompany,St. Paul, Minnesota. 320
Figure 1, Diagram of the placement of the hoof caulks and blanks on the bearing surface of the horseshoe, A) top view; B) side view.
consecutive strides were collected from each gait after the horses had settled into the gait for approximately 60 seconds. Data from the right and left limbswere combined for the walk and trot. Data were analyzed with an autodigitizing motion analysis system.e Displacement data were smoothed using a non-recursive moving average filter with a cut-off frequency of 15 Hz. This study consisted of two groups of horses wearing two types of horseshoes. Each shoe had initially been tapped with four holes, one hole at each heel and two at the toe (Figure 1). For the first treatment small metal blanks were inserted into each tapped hole of the horseshoes. In the second treatment 1/4 inch hoof caulks were inserted into each tapped hole of the horseshoes. The hoof caulks were of equal lengths and when placed in the horseshoe did not change the orientation of the hoof with the treadmill. The blanks were flush with the bearing surface of the horseshoe and were equal in weight to the hoof caulks. Stride length, stride frequency, stance duration, phalangeal (PH)joint angle, and metacarpophalangeal (MCP) joint angle were recorded. The PH angle was defined as the angle that the segment between the hoof and the approximate center of rotation of the metacarpophalangeal joint made with the treadmill. The metacarpophalangeal joint angle was defined as the angle between the third metacarpal segment (segment between the third metacarpal and center of MCP joint) and the phalangeal segment (segment between the hoof and center of MCP joint). Angular displacements of the MCP angle and PH angle were de¢EV3D,MotionAnalysisCorporation,Santa Rosa,California. JOURNAL OF EQUINE VETERINARY SCIENCE
Table 1. Mean (_+SD) stride length (SL)*, stride frequency (SF)** and stance duration (ST)*** in horses exercising with and without hoof caulks. SL Gait Walk Trot Canter Gallop * Meters/stride **Strides/second Seconds
SF
ST
Flat
Caulk
Flat
Caulk
2.1(.3) 2.8(.3) 3.9(.3) 5.3(.3)
2.1(.2) 2.8(.2) 4.0(.2) 5.4(.3)
1.0(.1) 1.5(.3) 1.8(.1) 1.9(.1)
1.0(.1) 1.5(.1) 1.8(.1) 1.9(.1)
scribed in terms of the three-dimensional axis system through which the horse moved. The horizontal axis was X, the vertical axis was Z and the perpendicular intersection of the two was the Y axis. Dorsal joint angles were defined in the sagittal plane and medial joint angles were defined in the transverse plane. The joint angles were measured at three points of the stride; 1) impact, 2) midstance and 3) lift-off. Impact and lift-off with the treadmill were determined from the vertical displacement of the marker on each hoof wall. This was also used to determine the stance phase for each limb. Mid-stance was defined to be the point when the third metacarpal bone was perpendicular to the treadmill. These stride parameters were chosen based upon their importance to load bearing and structural support while the limb was in contact with the treadmill. All analyses of variance procedures were performed using the GLM procedure of SAS, tl appropriate for a repeated measures design. The whole plot was the shoeing treatment used, and stride within a gait was used as the repeated measures effect. 12 The wide variation in MCP and PH joint angular changes were primarily due to the small sample size, however, differences due to treatment were still observed. To test differences due to the shoeing treatment the residual error was used.
Flat
Caulk
.54(.08) .20(.05) .14(.01) .12(.01)
.55(.06) .22(.02) .14(.02) .11(.01)
RESULTS When the hoof caulks were placed in the horseshoe, many of the kinematic measures made in this study were changed. However, stride length, stride frequency and stance duration were not changed (P>.05) with the addition of hoof caulks (Table 1). In the XZ plane (sagittal) the dorsal MCP joint angle was in most cases less (P<.05) for horses shod with hoof caulks than those shod with flat shoes at impact, midstance and lift-off (Table 2). The decrease in this angle indicated that the MCP joint was extended more during the stance phase for horses shod with hoof caulks than those shod normally. The greater joint extension was observed for most of the gaits which were filmed. A greater degree of MCP joint extension increased tendon elongation and the strains placed on flexor tendons and the suspensory ligament during the stance phase .t3 In the YZ plane (transverse) the MCP joint angle was in most cases less (P<.05) for the gallop during impact, mid-stance and lift-off in horses shod with caulks than for those shod normally (Table 3). The angular change during the stance phase could have been related to the greater amount of MCP joint extension which was observed in the
Table 2. Mean (_+SD) metacarpophalangeal joint angles in the sagittal plane (XZ) of horses exercising with and without hoof caulks. Flat
Impact Caulk
Mid-stance Flat Caulk
Gait Walk 157(11) 159(8) 149a(12) Trot 158a(11) 153b(8) 135a(15) Canter, lead 158(9) 158(7) 125(5) Canter,trail 152(9) 152(8) 125a(5) Gallop,lead 165a(16) 158b(11) 128a(13) Gallop,trail 157a(13) 152b(9) 131a(12) a,bMeansin the same row withinheadingwithouta commonsuperscriptdiffer (P<.05). Volume 14, Number 6, 1994
141b(5) 130b(4) 126(6) 126b(5) 123b(8) 124b(9)
Lift-off Flat Caulk 146a(5) 146a(18) 145(19) 135a(7) 134(11) 139a(19)
144b(6) 141 b(8) 142(17) 140b(14) 134(13) 133b(14)
321
Table 3. Mean (_+SD) metacarpophalangeal joint angles in the transverse plane (YZ) of horses exercising with and without hoof caulks. Impact
Mid-stance Flat Caulk
Flat Caulk Gait Walk 179(5) 179(6) 177(7) Trot 179(9) 179(6) 177(11) Canter,lead 179(6) 179(6) 178(9) Canter,trail 177(10) 177(10) 173(9) Gallop,lead 178a(10) 175b(8) 178(12) Gallop,trail 18@(14) 178b(9) 181a(12) a'bMeansin the same row withinheadingwithouta commonsuperscriptdiffer (P<.05). horses shod with hoof caulks. In the XZ plane (sagittal) the dorsal PH joint angle was in most cases larger (P<.05) at impact, mid-stance and liftoff for horses shod with hoof caulks than for those shod normally (Table 4). This was observed in all gaits except for the canter and indicated more flexion of the PH joint in horses shod with hoof caulks. In the transverse plane the PH joint angle was in most cases less (P<.05) with the addition of hoof caulks. This represented a shift laterally of about 2-3 ° during all parts of the stance phase and at all gaits except the gallop when the hoof caulks were added (Table 5). In this study, the phalangeal segment was aligned differently with other skeletal structures in the lower limb when horses were shod with hoof caulks than when they were shod normally.
DISCUSSION
The hoof caulks used in this study were balanced across the surface of the horseshoe. The hoof caulks did not alter stride length, stride frequency or stance duration in horses exercising on a treadmill. Horses wearing shoes with hoof caulks showed a decreased dorsal MCP joint angle at impact, mid-stance
178(8) 178(10) 177(7) 174(7) 177(11) 175b(8)
Lift-off Flat
Caulk
178(5) 178(12) 180a(11) 175(7) 183(10) 162a(11)
178(8) 179(7) 175b(13) 177(9) 178(8) 177b(7)
and lift-off in the sagittal plane. The increase in MCP joint extension was observed for most of the gaits measured in this study and led to a 5-8 ° increase in joint extension. Nilsson et al, 9 reported that the use of toe grabs alone did not change the dorsal metacarpophalangealjoint angle, but when heel caulks were used they increased the dorsal metacarpophalangeal joint angle. They also reported toe grabs decreased the dorsal phalangeal angle, while heel caulks increased the dorsal phalangeal angle. Overextension of the metacarpophalangeal joint has been suggested3,14,15 to be related to several musculo-skeletal diseases (navicular disease, sesamoid bone fracture, degenerative joint disease, tendon tearing). In the present study, the decrease in dorsal MCP joint angle at impact was caused by the use of hoof caulks and the angular change was maintained during the entire stance phase. This differed from the results of Nilsson et al., 9 and could be due to the balanced placement of the hoof caulks over the surface of the horseshoe. The use of toe grabs or heel caulks changes the orientation of the hoof with the ground, which because of the effective change in hoof angle effects joint kinematics differently. The use of hoof caulks at faster velocities than those used in the present study may also cause a greater amount of joint extension or even overextension than was observed in this study.
Table 4. Mean (-+SD) phalangeal joint angles in the sagittal plane (XZ) of horses exercising with and without hoof caulks. Impact Caulk
Mid-stance Flat Caulk
Flat Gait Walk 125a(9) 130b(7) 122a(9) Trot 126a(8) 133b(4) 13 la(10) Canter,lead 137(6) 136(4) 145(5) Canter,trail 136(5) 135(5) 145(5) Gallop,lead 132a(9) 140b(6) 141a(12) Gallop,trail 134a(7) 138b(6) 138a(13) a'bMeansin the same row withinheadingwithouta common superscriptdiffer (P<.05). 322
128b(5) 139b(4) 143(6) 143(4) 146b(8) 145b(9)
Lift-off Flat 100(10) 94a(12) 100a(13) 104(9) 107(11) 96a(18)
Caulk 97(6) 103b(7) 104b(10) 102(8) 106(11) 105b(15)
JOURNAL OF EQUINE VETERIN~:W SCIENCE
Table 5, Mean (± SD) phalangeal joint angles in the transverse plane (YX) of horses exercising with and without hoof caulks. Impact
Mid-stance
Lift-off
Flat
Caulk
Flat
Caulk
Flat
Gait Walk
96a(3)
94b(4)
96a(5)
93b(4)
95a(2)
92b(4)
Trot
97a(4)
94b(5)
97a(5)
95b(4)
96a(5)
94b(6)
Canter,lead
95a(4)
94b(3)
95a(3)
93b(4)
95a(5)
93b(5)
Canter,trail
95(5)
94(5)
95(3)
94(5)
95a(4)
93b(6)
94(4) 95(5)
95(5) 95(6)
95(4) 94(5)
Gallop,lead 94(6) 95(4) 95(7) Gallop,trail 93(5) 94(5) 96(6) a.bMeansin the same row within headingwithouta common superscriptdiffer (P<.05).
When the MCP angle was examined in the transverse plane a 3-6 ° change was noted at the canter and gallop when hoof caulks were used on the horseshoes. This caused the lower limb to resemble a varus MCP joint configuration during the stance phase. This joint configuration would presumably lead to increased stresses placed on the medial sides of the joint, and increased incidence of cartilage damage to those areas. The dorsal PH joint angle was greater in the horses shod with hoof caulks when compared to those shod normally. The dorsal PH joint angle followed a similar pattern for each gait and through most of the stance phase as it increased approximately 4-9 ° with the addition of hoof caulks to the horseshoes. This was similar to that described by Nilsson et alp for heel caulks, but differed from their observations for toe grabs. Forsell, 8 suggested that smaller dorsal phalangeal angles during stance increased tension in the deep flexor tendon which increased the pressure acting on the navicular bone. The greater dorsal PH joint angle observed in the present study likely then decreased the strain in the deep flexor tendon and decreased the forces placed upon the surface of the navicular bone during the stance phase. The larger dorsal PH joint angle may partially offset the increase in deep flexor tendon strain which occurred when MCP joint extension increased with the use of hoof caulks. If strain on the deep flexor tendon is increased, a progressive degeneration of the cartilaginous tissue in contact with the deep flexor tendon occurred, t6 These results suggest that hoof caulks do change orientation of the metacarpophalangeal and phalangeal joints during different portions of the stance phase. As a result, the change in limb configuration may lead to uneven loading patterns across the metacarpophalangeal joint surface which can increase the incidence of joint damage. Further study is needed to determine the specific effects that different types and configurations of tractions devices have upon limb orientation.
Volume 14, Number 6, 1994
Caulk
REFERENCES
1. Clayton HM: The effect of an acute hoof wall angulation on the stride kinematics of trotting horses. Eq VetJ 9:86-90, 1990a. 2. Clayton HM: The effect of acute angulation of the hind hooves on diagonal synchrony of trotting horses. Eq VetJ9:91-94, 1990a. 3. Rooney JR: Biomechanics of Lameness in Horses. Huntington: Kreiger Publishing Company, pp 115-196, 1969. 4. Bushe T, Turner TA, Poulos PW, Harwell NM: The effect of hoof angle on coffin, pastern and fetlock joint angles. Proc 33rd Am Assoc Eq Pract, pp 729-738, 1987. 5. Rooney, JR: The angulation of the forefoot and pastern of the horse. J Eq Vet Sc/ 4:138-143,1984. 6. Butler KD: The Principles of Horseshoeing II. Maryville: Doug Butler Publisher, pp 319-363, 1985. 7. Klobluk CN, Robinson RA, Gordon BJ, Clanton CJ, Trent AM, Ames TR: The effect of conformation and shoeing:A cohort study of 95 Thoroughbred racehorses. Proc 35th Am Assoc Eq Pract, pp 259-274, 1989. 8. Forsell EG: The diagnosis of lameness. Royal Vet. College Lectures, Stockholm, Sweden,1943, (as cited in Nilsson et al., 1973) 9. Nilsson G, Fredricson I, Drevemo S: Some procedures and tools in the diagnostics of distal equine lameness. Acta Vet Scand Supp144:63-79, 1973. 10. Marzan GT, Karara HM: A computer program for direct linear transformation solution of the collinearity condition, and some applications of it. Symposium on Close Range Photogrammetric Systems, pp 420-476, 1975. 11. SAS. Users' Guide: Statistics. Cary: SAS Institute Inc., 1985. 12. Steel RGD, Torrie JD: Principles and Procedures of Statistics: A Biometrica/Approach. New York: McGraw-Hill Book Company, 1980. 13. Riemersma DJ, Van Den Bogert AJ, Schamhardt HC, Hartman, W: Kinetics and kinematics of the equine hind limb: In vivo tendon strain and joint kinematics. Am J Vet Res 49:13531359, 1988. 14. Stashak TS: Adams' Lameness in Horses. 4th ed. Philadelphia: Lea and Febiger. pp 796-812, 1987. 15. Bramlage LR, Bukowiecki CW, Gabel AA: The effect of training on the suspensory apparatus of the horse. Proc, 35th Am Assoc Eq Pract, pp 245-247, 1989. 16. Thompson KN, RooneyJR, Petrites-Murphy MB: Considerations on the pathogenesis of navicular disease. J Eq Vet Sci 11:4-8, 1991.
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