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Rehabilitating the Chronically Laminitic Foot
REVIEW Rehabilitating the Chronically Laminitic Foot Bob Agne, DVM
ABSTRACT Trimming and shoeing the equine patients suffering with chronic laminitis entails a well organized approach, improves quality of life and generally results in a better outcome. The chronic laminitic hoof presents clinically in a variety of ways and thus treatment needs to be tailored to the individual horse. Keywords: Horse; Hoof; Foot; Laminitis; Shoeing
INTRODUCTION This article focuses on trimming and shoeing for horses that have suffered from laminitis, recovered from the initial insult, but now have chronic changes in the hoof capsule which may be causing lameness and other hoof problems. Common characteristics of the chronically laminitic hoof include the following:
Dished dorsal hoof wall Thin soles Irregular growth from the coronary band Toe cracks Frequent abscessation White line disease
Radiographically, the chronically laminitic foot typically shows the following changes: Lytic remodeling at the dorso-distal aspect (tip or apex) of the third phalanx (P3) A horn-lamellar zone that is wider than normal If medial and/or lateral sinking of P3 has occurred, then lytic changes may also be seen in the medial/lateral distal border of P3 Care should be taken when evaluating the “degree of rotation,” as it can be influenced by the manner in which the hoof has been trimmed. Venograms in these horses show variable degrees of vascular filling deficits in the dorsal solar and coronary plexi. If medial and/or lateral
From Rood & Riddle Equine Hospital, Lexington, KY. Reprint requests: Bob Agne, DVM, Rood and Riddle Equine Hospital, 2150 Georgetown Rd, Lexington, KY 40580. 0737-0806/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jevs.2010.07.014
Journal of Equine Veterinary Science Vol 30, No 9 (2010)
sinking has occurred, then deficits in the medial/lateral coronary and solar plexi may also be found. Lameness in these individuals is also variable. The initial examination should be thorough and aimed at ensuring that the condition is stable (i.e., there is no active lamellar inflammation and instability) and identifying exactly where the foot is painful and where hoof growth is still abnormal. Client education is important in these cases, as clients must understand that scarred, dystrophic lamellae will never return to normal. Even if we achieve improved sole and wall growth and are able to restore a normal hoof-pastern axis, the region of dystrophic lamellae will always be inherently weaker and more prone to abscessation as compared with the healthy tissue. Additionally, it is important for clients to understand that, because a portion of the lamellar region is permanently damaged, any further bouts of laminitis could be devastating.
GENERAL PRINCIPLES The following are the general principles that guide the rehabilitation process of the individual horses: 1. Protection of any weak and/or painful regions of the foot 2. Transfer of the load to the healthy regions of the foot and unloading the compromised regions 3. Encouraging digital biomechanics that promote horn growth in the affected regions 4. Prompt treatment of infections 5. Stabilization of wall cracks when necessary There is no single trimming or shoeing approach that is the only means of success. Each case is unique and many variables must be considered, including how the horse responds to the trimming/shoeing. One must be prepared to change the approach if the horse does not respond favorably.
INITIAL EXAMINATION The initial examination should include close inspection and palpation of the coronary band, hoof tester evaluation, and radiographs (lateromedial and standing dorsopalmar views at the very least). Careful attention should be paid to the growth rings below the coronary band, the health of the palmar/plantar portion of the foot, and overall hoof balance. Typically, the chronically laminitic foot has a stretched white line at the toe. The degree to which the white line
479
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480
has increased in width, compared with the white line at the quarter and heel, gives a good indication of the extent of P3 rotation. Similarly, a stretched white line in the medial or lateral region of the hoof can indicate that some medial or lateral sinking has occurred.
RADIOGRAPHIC ASSESSMENT Unless the hoof is severely overgrown, it is usually wise to take the radiographs before trimming the hoof. When assessing the radiographs, the following measurements made on the lateromedial view can be helpful in formulating a plan for trimming and shoeing, and in serving as a baseline for reassessment: Sole thickness at the tip of P3; about 10 mm is normal for a typical light-breed horse Width of the proximal and distal horn-lamellar zone; the proximal measurement is made just distal to the base of the extensor process; about 17 mm at both locations is normal for a typical light-breed horse Palmar/plantar angle (i.e., the angle of the solar margin of P3 in relation to the ground); 08 to 58 is normal for a typical light-breed horse Assessing the severity of lytic changes in P3, especially at the tip, can give some indication of the chronicity of the condition. The standing dorsopalmar view can help in the evaluation of lateral-medial balance, and in determining whether medial or lateral sinking has occurred. In addition, the radiographs provide a good view of hoof wall flares and the general position of the base of support and ground contact relative to the bony column.
TRIMMING Using the radiographs as a guide, trimming should proceed following the same principles used in a normal horse. However, the following precautions should be taken: 1. Trimming the heels to move the load-bearing surface back to the widest part of the frog may increase tension in the deep digital flexor tendon and thus increase stress on the dorsal lamellae. If significant heel height is lost in moving the loading surface back, then it may be advisable to use some type of heel wedge to prevent further stress on the dorsal lamellae. 2. Adequate sole depth under the tip of P3 is vital for protection of the bone and the solar corium. As sole growth typically is slowed in the chronically laminitic foot, sole depth at this location should be spared. No attempt should be made to give the solar surface of the hoof a concave shape by trimming out the sole. 3. As the dorsal region of the laminitic foot is compromised and may be unstable, the integrity of the palmar/plantar region of the foot should be maintained. The bars
should not be trimmed out; if they are healthy, they should be trimmed level with the heels. 4. The dorsal aspect of the hoof wall can be dressed back to establish a more normal hoof conformation. Although it may seem purely cosmetic, dressing the dorsal hoof wall back may reduce the lever effect on the already weakened dorsal lamellae and expose the dystrophic dorsal lamellar scar to the environment, allowing it to dry and perhaps reducing the incidence of abscesses in this region. 5. Easing tension in the DDFT during breakover can be achieved in the bare foot if sole thickness is sufficient (First check with hoof testers to determine whether sole depth is adequate). A subtle toe roll is made on the underside of the foot, from a point directly under the dorsal coronary band forward. If there is insufficient sole depth, sensitivity in the toe region, serious toe cracks, or other problems, then shoeing may be necessary. The environment in which the horse is managed should also influence the decision of shoeing. Realistically, most horses we are called to help will require shoeing to help them build sole thickness and uniform wall growth before they can go barefoot.
SHOEING Referring back to the goals of rehabilitation can help in choosing a shoeing approach that will protect the laminitic foot and encourage more normal growth. The typical chronic laminitis case is sensitive in the toe region because of inadequate sole depth. A shoe that covers and protects this region is advised, either a perimeter shoe with a wide-web toe or a full coverage shoe. Preferentially loading the healthy portion of the foot usually means loading the palmar/plantar regions for horses that primarily have P3 rotation. This goal can be achieved with a full coverage shoe or a heel plate and impression material in the caudal region of the foot. In horses that have P3 displacement medially or laterally, a shoe that loads the frog and unloads or floats the affected region usually is a good choice. To encourage sole growth through improved digital biomechanics, reducing the tension in the DDFT during both weight-bearing and breakover can be achieved by wedging the heels and rockering the toe. The same principle discussed earlier for rolling the toe in the bare foot can be applied using a rocker shoe. Raising the heels and rockering the toe tends to increase blood flow to the solar corium by reducing the vertical force of the tip of P3 on this region of the corium. However, heel wedging loads the caudal structures of the foot and may cause soreness in this region if done too aggressively or for a prolonged period. Wedging the heels and rockering the toe also encourages wall growth from the
B Agne Vol 30, No 9 (2010)
dorsal coronary band. Encouraging growth in horses with medial or lateral P3 displacement involves unloading that region as discussed previously. Visually monitoring wall growth and radiographically monitoring sole thickness over time can help determine whether the shoeing approach is achieving the desired goals or whether changes are needed.
481
Treating any infections within the hoof is an important aspect of rehabilitating laminitic feet. Foot infections are discussed in a separate paper in these proceedings. It is worth noting here that infection is often the reason we are called to treat these horses. By simultaneously treating the infection and encouraging more healthy foot growth, we help the equid resolve the infection and recreate a more healthy foot that is less likely to suffer from infection.
MANAGING TOE CRACKS AND INFECTIONS Toe cracks are common in horses with chronically laminitic feet. If they are mild to moderate, then therapeutic trimming and/or shoeing will often allow them to grow out without any further treatment. However, if the crack extends into the coronary band, it may need to be stabilized. There are several options, one being stabilization with small aluminum plates applied across the crack and secured with polymethylmethacrylate such that the crack is bridged but not filled. Care must be taken not to cover the crack, which encourages abscess formation.
DEEP FLEXOR TENOTOMY No discussion of rehabilitation for the chronically laminitic foot is complete without at least a mention of deep digital flexor tenotomy and realignment shoeing. This simple surgical procedure can be helpful when trimming and shoeing does not achieve the desired goals or when long-term therapeutic shoeing would be prohibitively expensive for the client. Tenotomy has been discussed elsewhere in these proceedings.
ABSTRACT Trimming and shoeing the equine patients suffering with chronic laminitis entails a well organized approach, improves quality of life and generally results in a better outcome. The chronic laminitic hoof presents clinically in a variety of ways and thus treatment needs to be tailored to the individual horse. Keywords: Horse; Hoof; Foot; Laminitis; Shoeing
INTRODUCTION This article focuses on trimming and shoeing for horses that have suffered from laminitis, recovered from the initial insult, but now have chronic changes in the hoof capsule which may be causing lameness and other hoof problems. Common characteristics of the chronically laminitic hoof include the following:
Dished dorsal hoof wall Thin soles Irregular growth from the coronary band Toe cracks Frequent abscessation White line disease
Radiographically, the chronically laminitic foot typically shows the following changes: Lytic remodeling at the dorso-distal aspect (tip or apex) of the third phalanx (P3) A horn-lamellar zone that is wider than normal If medial and/or lateral sinking of P3 has occurred, then lytic changes may also be seen in the medial/lateral distal border of P3 Care should be taken when evaluating the “degree of rotation,” as it can be influenced by the manner in which the hoof has been trimmed. Venograms in these horses show variable degrees of vascular filling deficits in the dorsal solar and coronary plexi. If medial and/or lateral
From Rood & Riddle Equine Hospital, Lexington, KY. Reprint requests: Bob Agne, DVM, Rood and Riddle Equine Hospital, 2150 Georgetown Rd, Lexington, KY 40580. 0737-0806/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jevs.2010.07.014
Journal of Equine Veterinary Science Vol 30, No 9 (2010)
sinking has occurred, then deficits in the medial/lateral coronary and solar plexi may also be found. Lameness in these individuals is also variable. The initial examination should be thorough and aimed at ensuring that the condition is stable (i.e., there is no active lamellar inflammation and instability) and identifying exactly where the foot is painful and where hoof growth is still abnormal. Client education is important in these cases, as clients must understand that scarred, dystrophic lamellae will never return to normal. Even if we achieve improved sole and wall growth and are able to restore a normal hoof-pastern axis, the region of dystrophic lamellae will always be inherently weaker and more prone to abscessation as compared with the healthy tissue. Additionally, it is important for clients to understand that, because a portion of the lamellar region is permanently damaged, any further bouts of laminitis could be devastating.
GENERAL PRINCIPLES The following are the general principles that guide the rehabilitation process of the individual horses: 1. Protection of any weak and/or painful regions of the foot 2. Transfer of the load to the healthy regions of the foot and unloading the compromised regions 3. Encouraging digital biomechanics that promote horn growth in the affected regions 4. Prompt treatment of infections 5. Stabilization of wall cracks when necessary There is no single trimming or shoeing approach that is the only means of success. Each case is unique and many variables must be considered, including how the horse responds to the trimming/shoeing. One must be prepared to change the approach if the horse does not respond favorably.
INITIAL EXAMINATION The initial examination should include close inspection and palpation of the coronary band, hoof tester evaluation, and radiographs (lateromedial and standing dorsopalmar views at the very least). Careful attention should be paid to the growth rings below the coronary band, the health of the palmar/plantar portion of the foot, and overall hoof balance. Typically, the chronically laminitic foot has a stretched white line at the toe. The degree to which the white line
479
B Agne Vol 30, No 9 (2010)
480
has increased in width, compared with the white line at the quarter and heel, gives a good indication of the extent of P3 rotation. Similarly, a stretched white line in the medial or lateral region of the hoof can indicate that some medial or lateral sinking has occurred.
RADIOGRAPHIC ASSESSMENT Unless the hoof is severely overgrown, it is usually wise to take the radiographs before trimming the hoof. When assessing the radiographs, the following measurements made on the lateromedial view can be helpful in formulating a plan for trimming and shoeing, and in serving as a baseline for reassessment: Sole thickness at the tip of P3; about 10 mm is normal for a typical light-breed horse Width of the proximal and distal horn-lamellar zone; the proximal measurement is made just distal to the base of the extensor process; about 17 mm at both locations is normal for a typical light-breed horse Palmar/plantar angle (i.e., the angle of the solar margin of P3 in relation to the ground); 08 to 58 is normal for a typical light-breed horse Assessing the severity of lytic changes in P3, especially at the tip, can give some indication of the chronicity of the condition. The standing dorsopalmar view can help in the evaluation of lateral-medial balance, and in determining whether medial or lateral sinking has occurred. In addition, the radiographs provide a good view of hoof wall flares and the general position of the base of support and ground contact relative to the bony column.
TRIMMING Using the radiographs as a guide, trimming should proceed following the same principles used in a normal horse. However, the following precautions should be taken: 1. Trimming the heels to move the load-bearing surface back to the widest part of the frog may increase tension in the deep digital flexor tendon and thus increase stress on the dorsal lamellae. If significant heel height is lost in moving the loading surface back, then it may be advisable to use some type of heel wedge to prevent further stress on the dorsal lamellae. 2. Adequate sole depth under the tip of P3 is vital for protection of the bone and the solar corium. As sole growth typically is slowed in the chronically laminitic foot, sole depth at this location should be spared. No attempt should be made to give the solar surface of the hoof a concave shape by trimming out the sole. 3. As the dorsal region of the laminitic foot is compromised and may be unstable, the integrity of the palmar/plantar region of the foot should be maintained. The bars
should not be trimmed out; if they are healthy, they should be trimmed level with the heels. 4. The dorsal aspect of the hoof wall can be dressed back to establish a more normal hoof conformation. Although it may seem purely cosmetic, dressing the dorsal hoof wall back may reduce the lever effect on the already weakened dorsal lamellae and expose the dystrophic dorsal lamellar scar to the environment, allowing it to dry and perhaps reducing the incidence of abscesses in this region. 5. Easing tension in the DDFT during breakover can be achieved in the bare foot if sole thickness is sufficient (First check with hoof testers to determine whether sole depth is adequate). A subtle toe roll is made on the underside of the foot, from a point directly under the dorsal coronary band forward. If there is insufficient sole depth, sensitivity in the toe region, serious toe cracks, or other problems, then shoeing may be necessary. The environment in which the horse is managed should also influence the decision of shoeing. Realistically, most horses we are called to help will require shoeing to help them build sole thickness and uniform wall growth before they can go barefoot.
SHOEING Referring back to the goals of rehabilitation can help in choosing a shoeing approach that will protect the laminitic foot and encourage more normal growth. The typical chronic laminitis case is sensitive in the toe region because of inadequate sole depth. A shoe that covers and protects this region is advised, either a perimeter shoe with a wide-web toe or a full coverage shoe. Preferentially loading the healthy portion of the foot usually means loading the palmar/plantar regions for horses that primarily have P3 rotation. This goal can be achieved with a full coverage shoe or a heel plate and impression material in the caudal region of the foot. In horses that have P3 displacement medially or laterally, a shoe that loads the frog and unloads or floats the affected region usually is a good choice. To encourage sole growth through improved digital biomechanics, reducing the tension in the DDFT during both weight-bearing and breakover can be achieved by wedging the heels and rockering the toe. The same principle discussed earlier for rolling the toe in the bare foot can be applied using a rocker shoe. Raising the heels and rockering the toe tends to increase blood flow to the solar corium by reducing the vertical force of the tip of P3 on this region of the corium. However, heel wedging loads the caudal structures of the foot and may cause soreness in this region if done too aggressively or for a prolonged period. Wedging the heels and rockering the toe also encourages wall growth from the
B Agne Vol 30, No 9 (2010)
dorsal coronary band. Encouraging growth in horses with medial or lateral P3 displacement involves unloading that region as discussed previously. Visually monitoring wall growth and radiographically monitoring sole thickness over time can help determine whether the shoeing approach is achieving the desired goals or whether changes are needed.
481
Treating any infections within the hoof is an important aspect of rehabilitating laminitic feet. Foot infections are discussed in a separate paper in these proceedings. It is worth noting here that infection is often the reason we are called to treat these horses. By simultaneously treating the infection and encouraging more healthy foot growth, we help the equid resolve the infection and recreate a more healthy foot that is less likely to suffer from infection.
MANAGING TOE CRACKS AND INFECTIONS Toe cracks are common in horses with chronically laminitic feet. If they are mild to moderate, then therapeutic trimming and/or shoeing will often allow them to grow out without any further treatment. However, if the crack extends into the coronary band, it may need to be stabilized. There are several options, one being stabilization with small aluminum plates applied across the crack and secured with polymethylmethacrylate such that the crack is bridged but not filled. Care must be taken not to cover the crack, which encourages abscess formation.
DEEP FLEXOR TENOTOMY No discussion of rehabilitation for the chronically laminitic foot is complete without at least a mention of deep digital flexor tenotomy and realignment shoeing. This simple surgical procedure can be helpful when trimming and shoeing does not achieve the desired goals or when long-term therapeutic shoeing would be prohibitively expensive for the client. Tenotomy has been discussed elsewhere in these proceedings.