Lameness (AAEP Wrap-Up)
P3 Alignment In Laminitic Horses
"Chronic laminitis is a frustrating and, at times, disheartening condition to manage," said Stephen O'Grady, BVSc, MRCVS. "Treating chronic laminitis is always a challenge; here we move a bit away from veterinary medicine into the mechanics of farriery."
With chronic laminitis, O'Grady said that toe-downward rotation of P3 (the coffin bone) often occurs, which results in more pressure placed on the solar corium (the highly vascular tissue from which the sole grows) under the apex of P3. This pressure can disrupt blood flow, altering the rate and even the direction of sole growth.
"The method used (to ameliorate rotation) must achieve these key goals:
- "Re-establish weight-bearing along the entire solar surface of P3 (rather than being concentrated at the apex of P3);
- "Aid breakover by moving the functional breakover point palmarly (heelward); and
- "Decrease tension in the deep digital flexor tendon (DDFT).
"These goals are achieved by trimming the heels, applying a shoe that places the functional breakover point near the apex of P3, gluing the shoe to the foot so that the shoe and the solar margin of P3 are parallel, and raising the heels using wedge-shaped rails (wider at the heels to elevate them) attached to the shoe," O'Grady explained.
He prefers glue-on shoes for this purpose, and also uses an elastic polymer to fill the sole and allow it to bear weight.
This procedure was done by O'Grady in 32 horses with chronic laminitis. Nine horses also received a DDFT tenotomy, and two received an inferior check desmotomy.
"Twenty (62.5%, including the two desmotomy cases) returned to some level of usefulness, although below their former level of athletic ability," O'Grady reported. "The remaining 12 horses (37.5%) were pasture sound (including the tenotomy cases). (See article #4995 online.)
MRI of the Distal Limb
Magnetic resonance imaging (MRI) is becoming more available and helpful as researchers learn more about MRI in the horse. Tim Mair, BVSc, DEIM, DESTS, Dipl. ECEIM, MRCVS, of the Bell Equine Veterinary Clinic in the United Kingdom, presented the basics of MRI and described his experience imaging 96 horses (83 had problems).
MRI has traditionally been very difficult to use on the horse because of the small space for the subject in the scanner as well as the need for immobility. Horses need to be placed under general anesthesia to be scanned in conventional human scanners. Most of these scanners are prohibitively expensive to purchase and to maintain, which limits their use to a small number of large institutions.
However, in June 2002 Mair and colleagues at the Bell Equine Veterinary Clinic installed an open U-shaped scanner designed for imaging the standing horse's lower limb. It will image the limb up to the knee or hock.
"Generally, the entire MRI scan protocol (including pilot sequences to check positioning and setup for subsequent scans) takes between 60 and 120 minutes to scan both front feet or both hind feet," he stated.
Most of the time, Mair said, a horse's feet can be imaged without motion correction software as long as sedation is used. However, he said that scanning of areas above the foot generally requires motion correction.
He explained that a free-standing, heavily sedated horse will often sway up to 20 mm, pivoting about the distal joints. Also, sedation can cause transient trembling, and quick movements when the horse readjusts his balance also occur. However, supporting a leg in the scanner and employing careful head holding can help minimize movement in the leg being scanned.
Mair and his colleagues found problems in several horses, including damages to and changes in the deep digital flexor tendon (DDFT), navicular bone and bursa, navicular collateral ligament, distal sesamoidean impar ligament, distal interphalangeal joint collateral ligament, distal interphalangeal joint, and sesamoidean ligament. In most horses with foot wounds, the tract of the penetrating wound was identifiable.
"We believe that this technique (MRI) could revolutionize the assessment of certain musculoskeletal lesions of the distal limb," Mair concluded. (See article #5008 online.)
MRI and Navicular Disease
"Magnetic resonance imaging (MRI) has added to our knowledge of navicular disease, in large part because for the first time we can see into the horse's foot," said Robert Schneider, DVM, MS, Dipl. ACVS, equine orthopedic surgeon at Washington State University's Veterinary Teaching Hospital. He discussed using MRI to diagnose and evaluate treatments for navicular disease and nearby pathologies since 1997.
"Because of the limitations of radiographs, many causes of bilateral (in both front feet or both hind feet) foot pain have been recognized and diagnosed as navicular disease," he said. "MRI has allowed us to begin to differentiate some of these problems from navicular disease.
"The following problems were diagnosed as navicular disease in different horses prior to MRI: Chronic laminitis with mild rotation of P3, early bilateral osteoarthritis of the proximal interphalangeal joint, palmar (caudal or rearward) heel laminar pain, and bilateral desmitis of the straight sesamoidean ligament proximal to (above) its insertion on P2," he described. The varied nature of these problems explains the poor success rate of navicular syndrome treatment.
Differentiating horses with true navicular syndrome from those with nearby problems has improved treatment because veterinarians can use it to prescribe more targeted treatment for a specific problem, Schneider said. For example, he noted that horses with tendinitis require different treatment (injection of anti-inflammatory medication into the tendon sheath) than those with navicular bone pathology, but those tendon treatments wouldn't be recommended if the practitioner thought the horse had a bone problem. Also, rest for these horses--which is usually not recommended for navicular disease--might be beneficial for healing in horses with soft tissue damage.
"As MRI increases, our knowledge about navicular disease, early diagnosis, new treatments, and/or better case selection for current treatments will hopefully follow," he concluded. (See article #4990 online.)
Accessory Ligament Injury
Acute desmitis (ligament inflammation) of the small accessory ligament that anchors the superficial digital flexor tendon to the upper foreleg bone (radius) has been shown to be a significant cause of pronounced, transient lameness in Thoroughbred racehorses. Johanna Reimer, VMD, Dipl. ACVIM, of the Rood and Riddle Equine Hospital in Kentucky, presented her findings on this injury.
She diagnosed the condition in 27 Thoroughbred racehorses and one American Saddlebred (which was left out of the analysis) after they were presented with the following clinical signs: Transient lameness, persistent effusion (constant swelling) of the carpal sheath, palpable thickening behind the middle of the knee, recurrent effusion of the carpal sheath, and/or apparent thickening of the proximal (upper) SDFT that looks like a bowed tendon.
After several weeks of rest, restricted exercise, and a gradual return to full work, Reimer said that four horses had been retired. Twenty-two returned to training, with one dying of unrelated causes before racing. Nineteen (86%) returned to racing after an average of 8.5 months (range--two weeks to 16 months). One horse injured the other AL-SDFT during his first start back, but raced again six months later. Three horses started three times after recovering, three had four starts, 11 horses had at least five starts, and three only recently returned to racing. Three horses that did swimming or water treadmill exercise had poor healing or re-injury of the AL-SDFT.
"If the ligament seems of uniform and normal echogenicity, jogging may resume with an anticipated return to racing as early as six months post-injury in some cases," she said.
"Acute desmitis of the AL-SDFT might be an under-diagnosed condition in the Thoroughbred racehorse," Reimer said. She also noted that the condition was more prevalent in horses at least four years old, tended to appear in the right forelimb (at least in these American racehorses), and was not associated with other problems in the carpal canal region. (See article #4988 online.)
Examining the Foot
"The foot is involved, either directly or indirectly, in the large majority of lameness cases," said Ric Redden, DVM, founder of the International Equine Podiatry Center in Versailles, Ky.
In his presentation on examining the foot clinically and radiographically, Redden described in great detail the external and internal features that should be evaluated. He offered numerous photographs and radiographs of cases to illustrate his points on clinical observation, radiographic technique, and radiograph interpretation.
"The key is to use a disciplined, methodical approach that is designed to disclose and define the various normal soft tissue parameters, normal bone anatomy, and normal hoof capsule anatomy as well as the inter-relation of each component," he said. "When examining a foot or a radiograph, look for all the normal areas first; what is left over points to the problem you seek."
He described the history and clinical examination as being of paramount importance in evaluating the foot, with radiographs being used only to confirm diagnosis and help the practitioner develop shoeing prescription measurements. Less-exposed radiographs, which are good for showing soft tissue detail, are essential as, "Soft tissue pathology is present to some degree in every foot-sore horse, and soft tissue problems will jump out at you way before the bone changes.
"It is not enough for us to reach a medical diagnosis; our examinations must have the dual goal of directing us toward a solution to the horse's problem, for both immediate relief and long-range restoration and preservation of structural and functional integrity," he added. "That goal can be met only when our examinations are aimed at collecting as much specific information as possible, about every component of the digital unit." (See article #1457 online.)
Ultrasound Exam of the Shoulder
"Shoulder lameness presents a diagnostic challenge," said Mary Beth Whitcomb, DVM, lecturer in surgical and radiological sciences at the University of California, Davis, in her presentation on ultrasound examination of the equine shoulder. "Radiographs of this area have limited visibility, nuclear scintigraphy is expensive, and ultrasound is inexpensive and available to most practitioners," she said.
Whitcomb described shoulder ultrasound examination technique (using the procedure published by Tnibar, et al1) and shoulder anatomy as seen on ultrasound in great detail for attendees.
Results of Shoulder Exams--Whitcomb described the results of 81 ultrasound shoulder examinations in 61 horses at UC Davis from 1999-2000. Forty-three horses (70.5%) had shoulder abnormalities. The most common was bicipital bursitis (inflammation of the bicipital bursa; 19 horses), but several other abnormalities were discovered.
"The results of this study strongly support the use of ultrasound to diagnose soft tissue and bony abnormalities of the entire shoulder region," Whitcomb stated. She also noted that lesions of the infraspinatus tendon and bursa had not previously been reported, but were found in this study.
Another use of ultrasound in the shoulder is to guide procedures such as analgesia injection and lavage (flushing) of infected synovial structures (bursa); she described several cases and procedures as examples. (See article #4998 online.)
1 Tnibar, M.; Auer, J.A.; Bakkali, S. Ultrasonography of the equine shoulder: technique and normal appearance. Veterinary Radiology 1999; 40:44-47.
Diagnosing Pelvic Fractures
"The equine practitioner is likely to be faced with a horse that he/she suspects to have a pelvic fracture at some point in his or her career," said Agustin Almanza, MV, of the University of California, Davis, in his presentation on ultrasound examination for pelvic fractures. "The definitive diagnosis of a pelvic fracture in these cases can be a challenge, especially in the ambulatory setting.
He explained that radiographic examination (shot from the belly) and nuclear scintigraphy for this area can be quite helpful, but expensive. Both imaging modalities for this area require transport to a referral facility. Ultrasound, however, is inexpensive and available to many practitioners.
Findings in 28 Horses--Between August 1999 and December 2002, 53 horses received ultrasonographic exams of the pelvis at UC Davis (a total of 70 hemipelves, or pelvis halves). The examinations found 32 fractures in 28 horses (four horses had two fractures each). Transrectal ultrasound performed on 10 of the 28 horses with fractures detected previously undiagnosed fractures in two of them. The affected horses were varied as to sex, age, breed, and use.
Conclusions--"Ultrasound was able to provide excellent detail of the bony contours of the fracture sites and was useful in identifying associated muscle tearing and hematoma formation," Almanza said.
Also, he noted that standing lateral radiographs helped them diagnose fractures in three horses, although previous studies have not shown this imaging method to be useful for pelvic fractures.
"In summary, pelvic fractures should be suspected in horses with acute onset of severe hind limb lameness localized to the upper limb in performance or pasture horses of many breeds and uses," Almanza concluded. (See article #5000 online.)
About 65 veterinarians and farriers filled a room to discuss diagnostic analgesia, pads, Strasser trimming, ultrasound, and much more during the Podiatry Forum at the 2003 convention.
Moderators Gayle Trotter, DVM, MS, professor in clinical sciences at Colorado State University, and Redden facilitated the lively discussion.
The challenges of nerve blocks were mentioned, as well as the use of ultrasound.
Scintigraphy was described as being useful for imaging selected foot problems, especially sidebone. One attendee noted that many consider sidebone a relatively insignificant problem, but he sees it a lot in jumpers and the horses often respond to treatment.
Radiographic imaging of pedal osteitis (inflammation of the coffin bone, or P3) was also discussed. Trotter noted that a skyline view of the dorsal edge of P3 is very prone to error.
The Strasser Method--A particularly hot topic was the Strasser trim, which has met with a lot of skepticism among veterinarians and farriers. Many take issues with the principles espoused by German veterinarian Hiltrud Strasser. One veterinarian who had attended a three-day Strasser clinic described the differences between Strasser's methods and those traditionally taught to farriers.
"People say using this method produces a lot of soreness," he commented. "They say this is expected as the hoof becomes more 'normal,' which can take up to eight months. Some people have had good success with a modified, less severe version of this trim. You have to divide this method as it applies to pathological problems and normal feet."
Trotter commented that if veterinarians and farriers don't do a good enough job, there is always room for new fads in hoof care.
Maggots?--One veterinarian described his use of sterile maggots following street nail operations (to open an infected navicular bursa and drain it of infected material) and curettings of diseased tissue on osteomyelitis cases. They debride tissues in a non-traumatic fashion, he said. (See article #4991 online.)
- Preventing Contralateral Limb Laminitis: See page 28 of the March 2004 issue, and article #4976 online.
- Look for an in-depth article on presentations by Chris Pollitt, BVSc, PhD, in the August 2004 issue.
- "Growth and Adaptive Capabilities of the Hoof Wall and Sole: Functional Changes in the Response to Stress," Robert M. Bowker, VMD, PhD. Article #5005 online.
- "Contrasting Structural Morphologies of 'Good' and 'Bad' Footed Horses," Bowker. Article #5004 online.
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.
POLL: Managing Working Horses