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Luxation of the Superficial Digital Flexor Tendon from the Tuber Calcanei in Horses

By

Jane C. Boswell

, MA, VetMB, CertVA, CertES (Orth), DECVS, MRCVS, The Liphook Equine Hospital

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

Luxation or subluxation of the superficial digital flexor tendon from the point of the hock may occur after disruption to the retinaculum that attaches the tendon to the calcaneus. Luxation or subluxation more commonly occurs laterally but may occur medially. Rarely, the superficial digital flexor tendon may split sagitally, and part of the tendon luxates medially and part laterally.

Lameness is usually acute and severe in onset and associated with marked swelling over the point of the hock. Horses may become panic-stricken in the acute stages if the tendon is moving on and off the os calcis, and they may kick out frequently with the affected limb. In some horses, the tendon will resume its normal position when the horse is standing but luxate or subluxate as the horse moves; in other horses, the tendon remains permanently displaced. Diagnosis is based on careful observation and palpation and can be confirmed by ultrasonography.

In the acute stages, sedation and analgesia are important. If the tendon remains permanently displaced laterally (or medially), treatment involves prolonged stall rest (4–6 mo), possibly with the limb immobilized in a heavily padded full limb bandage or cast. Lameness usually improves, but the horse may be left with a mechanical lameness causing a jerky hindlimb action that may limit its use as a dressage horse, although horses may be able to jump or race. Horses with a persistently medially displaced tendon usually have a greater degree of mechanical lameness and a poorer prognosis for return to athletic function.

In horses in which the tendon is unstable and subluxates on and off the tuber calcanei, endoscopy of the calcaneal bursa reveals disruption of both the medial retinacular/calcaneal insertion of the superficial digital flexor tendon and its associated fibrocartilage, with disruption of the medial wall of the bursa creating or establishing communication with an acquired subcutaneous bursa. Treatment is by radical resection of the disrupted fibrocartilage and division of remaining attachments of the fibrocartilage or retinacular insertions with the unstable main body of the superficial digital flexor tendon, thereby creating a stable lateral subluxation. Although repair or reconstruction techniques have been reported, results have been unreliable. Permanent stable subluxation eliminates anxiety and usually results in a “sound” functional horse.

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
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Musculoskeletal Disorders in Large Animals
A seven-year-old Quarter horse gelding presents with a 1-week history of mild lameness. During the examination, the horse raises his head as he places weight on his left forelimb and drops it when placing weight on the right forelimb. Which limb is most likely affected in this horse?
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