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Suspensory Desmitis in Horses

By

Matthew T. Brokken

, DVM, The Ohio State University

Last full review/revision Sep 2015 | Content last modified Jun 2016
Topic Resources

Injuries of the suspensory ligament (interosseous muscle) are common in forelimbs and hindlimbs of horses. Lesions are typically classified as affecting the proximal, body, or branches of the suspensory ligament.

Proximal Suspensory Desmitis:

The term proximal suspensory desmitis (PSD) is restricted to lesions confined to the proximal one-third of the metacarpus. PSD can occur unilaterally or bilaterally and is a common injury in all types of athletic horses. Injury to the proximal suspensory ligament and/or its attachment to the proximal palmar aspect of the third metacarpal bone typically results in sudden onset lameness that seems to improve within a few days. Lameness varies from mild to moderate and is typically not severe unless there is substantial involvement of the ligament and its attachment (avulsion of the palmar cortex). If the horse has bilateral PSD, there may be less overt lameness but more loss of action of the horse. Lameness is typically more noticeable on soft ground and with the affected leg on the outside of the circle. Response to distal limb and/or carpal flexion tests is variable. Pressure applied to the proximal palmar metacarpal region may elicit pain; however, this response/reaction should be compared with that of the other limb to determine significance.

Diagnosis of PSD usually requires localization with diagnostic analgesia, because typically horses do not have clinical signs (eg, heat, pain, swelling) that allow lameness to be localized to this region. There are multiple techniques to desensitize the proximal aspect of the palmar metacarpus. However, there is confusion interpreting the results of subcarpal analgesia because of the lack of specificity of local analgesic techniques. After lameness has been localized, radiographs as well as ultrasonographic examination of the region should be performed. Ultrasound of the proximal suspensory should be critically compared with that of the other limb, remembering that bilateral lesions do exist. Nuclear scintigraphy can help detect osseous injury at the proximal suspensory attachment, but negative scintigraphic images do not exclude the presence of PSD. MRI is also extremely useful to detect subtle changes in the proximal suspensory ligament that may not be visible or conclusive with ultrasonography. In addition, MRI allows accurate examination of the osseous structures adjacent to the suspensory ligament (metacarpal bones and distal carpal bones).

In contrast to hindlimb PSD, most horses with acute forelimb PSD respond well to rest and a controlled exercise program for 3–6 mo (~90% return to function). Premature return to work typically results in recurrence/persistence of lameness. Horses with chronic PSD may require a longer rehabilitation program or adjunct therapy (NSAIDs, shockwave, regenerative therapies) to return to consistent work.

Desmitis of the Body of the Suspensory Ligament:

This is principally an injury of racehorses. Injuries usually affect the forelimbs of Thoroughbreds and the forelimbs and hindlimbs in Standardbreds. Soreness on palpation of the forelimb suspensory ligament is quite common in horses with lameness associated with a more distal limb problem; however, structural abnormality of the ligaments is only rarely identifiable ultrasonographically. Clinical signs vary and involve enlargement of the ligament, local heat, swelling, and pain. Diagnosis is usually based on clinical signs and can be confirmed ultrasonographically. Treatment is aimed at reducing inflammation by systemic NSAIDs, hydrotherapy, and controlled exercise. Shockwave therapy, platelet-rich plasma, and stem-cell therapy have also been used for suspensory body lesions.

Desmitis of the Branches of the Suspensory Ligament:

This relatively common injury is seen in all types of horses in forelimbs and hindlimbs. Usually only a single branch in a single limb is affected, although both branches may be affected, especially in hindlimbs. Foot imbalance is often recognized in affected horses, and this may be a predisposing factor.

Clinical signs depend on the degree of damage and the chronicity of the lesion(s) and include localized heat and swelling. Swelling is often due to local edema of the affected branch. Effusion can be present in the adjacent palmar/plantar fetlock joint and/or the digital flexor tendon sheath. Pain is usually elicited either by direct pressure applied to the injured branch or by flexion of the fetlock. Lameness is variable and may be absent.

Diagnosis is based on clinical signs and ultrasonographic examination. Radiographic examination should also be performed to evaluate the attachment of the suspensory branch on the proximal sesamoid bones. Low 4-point diagnostic analgesia as well as intra-articular analgesia of the fetlock joint (varying degrees based on the location of the branch injury) improves lameness. Ultrasonography can detect a range of abnormalities, including enlargement, alteration of shape, and alterations in echodensity.

Management depends on the severity of the signs and on the breed and use of the horse. Shockwave therapy, local anti-inflammatories, ligament splitting, and regenerative therapy have all been used with varying results. Strict attention to foot balance is also critical in management of these lesions. Clinical signs may take ≥6 mo to improve, and the condition may recur. Prognosis for reinjury or persistence of lameness is worse in horses that are hyperextended in their fetlocks at rest or in horses with marked periligamentous fibrosis around the branch on ultrasound.

OTHER TOPICS IN THIS CHAPTER
Lameness in Horses
Overview of Lameness in Horses
The Lameness Examination in Horses
Imaging Techniques in Equine Lameness
Arthroscopy in Equine Lameness
Regional Anesthesia in Equine Lameness
Disorders of the Foot in Horses
Osseous Cyst-like Lesions in the Distal Phalanx in Horses
Bruised Sole and Corns in Horses
Canker in Horses
Fracture of Navicular Bone in Horses
Fracture of Distal Phalanx in Horses
Keratoma in Horses
Laminitis in Horses
Navicular Disease in Horses
Pedal Osteitis in Horses
Puncture Wounds of the Foot in Horses
Pyramidal Disease in Horses
Quittor in Horses
Quarter Crack in Horses
Scratches in Horses
White Line Disease in Horses
Sheared Heels in Horses
Sidebone in Horses
Thrush in Horses
Disorders of the Pastern and Fetlock
Fractures of the First and Second Phalanx in Horses
Fractures of the Proximal Sesamoid Bones in Horses
Osteoarthritis of the Proximal Interphalangeal Joint in Horses
Palmar/Plantar Metacarpal/Metatarsal Nonadaptive Bone Remodeling in Horses
Sesamoiditis in Horses
Chronic Proliferative Synovitis in Horses
Digital Sheath Tenosynovitis in Horses
Disorders of the Metacarpus in Horses
Tendinitis in Horses
Suspensory Desmitis in Horses
Inferior Check Desmitis in Horses
Bucked Shins in Horses
Exostoses of the Second and Fourth Metacarpal Bones in Horses
Fractures of the Small Metacarpal (Splint) Bones in Horses
Fracture of the Third Metacarpal (Cannon) Bone in Horses
Disorders of the Carpus in Horses
Fracture of the Carpal Bones in Horses
Subchondral Bone Disease of the Third Carpal Bone in Horses
Tearing of the Medial Palmar Intercarpal Ligament in Horses
Osteoarthritis of the Carpus in Horses
Distal Radial Exostosis and Osteochondroma of the Distal Radius in Horses
Carpal Hygroma in Horses
Rupture of the Common Digital Extensor Tendon in Horses
Disorders of the Shoulder in Horses
Developmental Diseases of the Shoulder in Horses
Fractures of the Shoulder in Horses
Bicipital Bursitis in Horses
Infection of the Shoulder in Horses
Suprascapular Neuropathy in Horses
Osteoarthritis of the Shoulder in Horses
Disorders of the Elbow in Horses
Developmental Orthopedic Disease in the Elbow of Horses
Fractures of the Elbow in Horses
Osteoarthritis of the Elbow in Horses
Collateral Ligament Injury in the Elbow of Horses
Disorders of the Metatarsus in Horses
Bucked Shins/Dorsal Cortical Fractures of the Third Metatarsal Bone in Horses
Exostoses of the Metatarsal Bones in Horses
Diaphyseal Fracture of the Third Metatarsal Bone in Horses
Incomplete Longitudinal Fractures of the Plantar Aspect of the Third Metatarsal Bone in Horses
Focal Bone Reaction and Avulsion Fractures of the Third Metatarsal Bone in Horses
Fractures of the Second and Fourth Metatarsal Bones in Horses
Enostosis-like Lesions of the Third Metatarsal Bone in Horses
Disorders of the Tarsus in Horses
Failure of Ossification of the Distal Tarsal Bones in Horses
Osteoarthritis of the Distal Tarsal Joints in Horses
Osteoarthritis of the Talocalcaneal Joint in Horses
Osteoarthritis of the Tarsocrural Joint in Horses
Synovitis/Capsulitis of the Tarsocrural Joint in Horses
Osteochondrosis of the Tarsocrural Joint in Horses
Osteitis of the Calcaneus in Horses
Fractures of the Distal Tarsal Bones in Horses
Fracture of the Talus in Horses
Fracture of the Fibular Tarsal Bone (Calcaneus) in Horses
Fracture of the Lateral Malleolus of the Tibia in Horses
Tarsal Joint Luxation in Horses
Desmitis of the Collateral Ligaments of the Tarsus in Horses
Rupture of the Fibularis (Peroneus) Tertius in Horses
Stringhalt
Curb in Horses
Disorders of the Tarsal Sheath in Horses
False Thoroughpin in Horses
Luxation of the Superficial Digital Flexor Tendon from the Tuber Calcanei in Horses
Gastrocnemius Tendinitis in Horses
Calcaneal Bursitis in Horses
Capped Hock
Disorders of the Stifle in Horses
Osteochondrosis of the Stifle in Horses
Subchondral Cystic Lesions in Horses
Meniscus and Meniscal Ligament Injuries in Horses
Cranial and Caudal Cruciate Ligament Injuries in Horses
Collateral Ligament Injuries in Horses
Intermittent Upward Fixation of the Patella and Delayed Patella Release in Horses
Fragmentation of the Patella in Horses
Patellar Luxation in Horses
Patellar Ligament Injuries in Horses
Gonitis and Osteoarthritis in Horses
Chondromalacia of the Femoral Condyles in Horses
Fractures of the Stifle in Horses
Disorders of the Hip in Horses
Luxation of the Coxofemoral Joint in Horses
Pelvic Fracture in Horses
Osteoarthritis and other Coxofemoral Joint Diseases in Horses
Disorders of the Back and Pelvis in Horses
Spinal Processes and Associated Ligaments in Horses
Articular Process−Synovial Intervertebral Articulation Complexes in Horses
Vertebral Bodies and Discs in Horses
Muscle Strain and Soreness in Horses
Lumbosacral Junction Abnormalities in Horses
Sacroiliac Joint Abnormalities in Horses
Developmental Orthopedic Disease in Horses
Osteochondrosis in Horses
Physitis in Horses
Flexural Deformities in Horses
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The lameness examination is an important method to identify musculoskeletal abnormalities. Which of the following abnormalities is NOT observed during a physical and lameness exam? 
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