Treatment of a Cyst-Like Synovial Hernia Associated with the Digital Flexor Tendon Sheath of a 17-Year-Old Pony

The aim of this study is to describe the successful treatment of a synovial hernia associated with the digital flexor tendon sheath (DFTS) in a 17-year-old pony. The pony presented with left forelimb lameness and multiple unusual swellings of the palmar and plantar aspect of the fetlock. The lameness was isolated to a swelling in close proximity to the DFTS of the left forelimb using diagnostic analgesia, and on diagnostic imaging, the swelling was found to be associated with the DFTS. The hernia resolved after percutaneous drainage and intralesional corticosteroids and atropine and pressure bandaging. Reports of synovial hernias in the horse associated with the DFTS are rare. This difference should be considered when presented with cases exhibiting similar clinical signs.     

MAGNETIC RESONANCE IMAGING FEATURES OF PROXIMAL METACARPAL AND METATARSAL INJURIES IN THE HORSE

Magnetic resonance (MR) imaging abnormalities in horses with lameness localized to the proximal metacarpal or metatarsal region have not been described. To accomplish that, the medical records of 45 horses evaluated with MR imaging that had lameness localized to either the proximal metacarpal or metatarsal region were reviewed. Abnormalities observed in the proximal suspensory ligament or the accessory ligament of the deep digital flexor tendon included abnormal high signal, enlargement, or alteration in shape. Twenty-three horses had proximal suspensory ligament desmitis (13 hindlimb, 10 forelimb). Sixteen horses had desmitis of the accessory ligament of the deep digital flexor tendon. One horse had desmitis of the proximal suspensory ligament and the accessory ligament of the deep digital flexor tendon on the same limb and one horse had desmitis of the proximal suspensory ligament on one forelimb and desmitis of the accessory ligament of the deep digital flexor tendon on the other forelimb. Four horses did not have abnormalities in the proximal suspensory ligament or accessory ligament of the deep digital flexor tendon. Eighty percent of horses with forelimb proximal suspensory ligament desmitis and 69% of horses with hindlimb proximal suspensory ligament desmitis returned to their intended use. Sixty-three percent of horses with desmitis of the accessory ligament of the deep digital flexor tendon were able to return to their intended use. MR imaging is a valuable diagnostic modality that allows diagnosis of injury in horses with lameness localized to the proximal metacarpal and metatarsal regions. The ability to accurately diagnose the source of lameness is important in selecting treatment that will maximize the chance to return to performance.     

Use of magnetic resonance imaging to diagnose distal sesamoid bone injury in a horse

CASE DESCRIPTION: A 5-year-old Appaloosa mare was examined for severe left forelimb lameness of 4 months' duration. CLINICAL FINDINGS: Lameness was evident at the walk and trot and was exacerbated when the horse circled to the left. Signs of pain were elicited in response to hoof testers placed over the frog of the left front hoof, and a palmar digital nerve block eliminated the lameness. Radiographs revealed no abnormalities, but magnetic resonance imaging (MRI) revealed increased bone density in the medullary cavity of the distal sesamoid (navicular) bone in the proton density and T2-weighted images and a defect in the fibrocartilage and subchondral bone of the flexor cortex. TREATMENT AND OUTCOME: Because of the absence of improvement after 4 months and the poor prognosis for return to soundness, the mare was euthanatized. An adhesion between the deep digital flexor tendon and the flexor cortex defect on the navicular bone was grossly evident, and histologic evaluation revealed diffuse replacement of marrow trabecular bone with compact lamellar bone. Changes were consistent with blunt traumatic injury to the navicular bone that resulted in bone proliferation in the medullary cavity. CLINICAL RELEVANCE: Use of MRI enabled detection of changes that were not radiographically evident and enabled accurate diagnosis of the cause of lameness. Navicular bone injury may occur without fracture and should be considered as a differential diagnosis in horses with an acute onset of severe unilateral forelimb lameness originating from the heel portion of the foot.     

Alternative surgical treatment for synovial ganglion cyst of the digital tendon sheath in one horse

A 6-year-old Highland pony gelding was presented with severe left fore (LF) limb lameness of acute onset. The lameness occurred concomitantly with mild digital flexor tendon sheath (DFTS) effusion and focal painful swelling on the lateral aspect of the LF fetlock region. Clinical examination and diagnostic analgesia localised the lameness to the fetlock region and on ultrasound, a cyst-like structure filled with anaechoic fluid was detected just proximal to the lateral sesamoid bone, at the proximo-lateral aspect of the DFTS and adjacent to the lateral neurovascular bundle. Communication between the cyst-like structure and the DFTS was suspected ultrasonographically and then confirmed with contrast tenography. Tenoscopic examination of the LF DFTS was performed and the communication between the fluid-filled structure and the synovial cavity was detected. The defect in the DFTS wall was enlarged tenoscopically and the lining of the cyst-like structure was debrided. The horse recovered well post-operatively and was back in work with no evident lameness 8 months after surgery. This alternative minimally invasive surgical treatment had an excellent outcome and has the advantage of reducing the risk associated with en bloc resection.     

MRI FEATURES OF METACARPO(TARSO)PHALANGEAL REGION LAMENESS IN 40 HORSES

Lameness originating from the metacarpo(tarso)phalangeal (MP) joint has a significant effect on the use and athletic competitiveness of a horse. The identification of the cause of lameness originating from the MP joint can be challenging, given the limitations of radiography, ultrasonography, and nuclear scintigraphy. Our purpose was to describe the injury types and incidence in magnetic resonance imaging (MRI) studies from 40 horses with lameness attributable to the MP joint region where it was not possible to reach a clinically plausible diagnosis using other imaging modalities. Horses were examined in a 1.5 T magnet (Siemens Medical Solutions) under general anesthesia. The frequency of occurrence of MR lesions was subchondral bone injury (19), straight or oblique distal sesamoidean desmitis (13), articular cartilage injury and osteoarthritis (eight), suspensory branch desmitis (seven), osteochondral fragmentation (seven), proximal sesamoid bone injury (seven), intersesamoidean desmitis (four), deep digital flexor tendonitis (four), collateral desmitis (three), superficial digital flexor tendonitis (two), enostosis‐like lesions of the proximal phalanx or MCIII (two), desmitis of the palmar annular ligament (one), desmitis of the proximal digital annular ligament (one), and dystrophic calcification of the lateral digital extensor tendon (one). Twenty‐five horses had multiple MR abnormalities. MRI provided information that was complementary to radiography, ultrasonography, and nuclear scintigraphy and that allowed for a comprehensive evaluation of all structures in the MP joint region and a diagnosis in all 40 horses.     

Aseptic tenosynovitis of the carpal flexor sheath caused by rupture of the accessory ligament of the deep digital flexor tendon

A mare was evaluated for acute left forelimb lameness with effusion of the carpal flexor sheath. No osseous abnormalities were noted during radiographic examination. Significant disruption of the accessory ligament of the deep digital flexor tendon was seen during ultrasonographic examination. Carpal sheath effusion and lameness resolved after medical treatment.     

Injection of corticosteroids, hyaluronate, and amikacin into the navicular bursa in horses with signs of navicular area pain unresponsive to other treatments: 25 cases (1999-2002)

OBJECTIVE: To determine history, clinical and radiographic abnormalities, and outcome in horses with signs of navicular area pain unresponsive to corrective shoeing and systemic nonsteroidal anti-inflammatory drug administration that were treated with an injection of corticosteroids, sodium hyaluronate, and amikacin into the navicular bursa. DESIGN: Retrospective study. ANIMALS: 25 horses. PROCEDURE: Data collected from the medical records included signalment, history, horse use, severity and duration of lameness, shoeing regimen, results of diagnostic anesthesia, radiographic abnormalities, and outcome. RESULTS: 17 horses had bilateral forelimb lameness, 7 had unilateral forelimb lameness, and 1 had unilateral hind limb lameness. Mean duration of lameness was 9.2 months. All horses had been treated with corrective shoeing and nonsteroidal anti-inflammatory drugs for at least 6 months; 18 had previously been treated by injection of corticosteroids and sodium hyaluronate into the distal interphalangeal joint. Fourteen horses had mismatched front feet, and 21 horses had signs of pain in response to application of pressure over the central aspect of the frog. Palmar digital nerve anesthesia resulted in substantial improvement in or resolution of the lameness in all horses. Twenty horses (80%) were sound and returned to intended activities 2 weeks after navicular bursa treatment; mean duration of soundness was 4.6 months. Two horses that received numerous navicular bursa injections had a rupture of the deep digital flexor tendon at the level of the pastern region. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that navicular bursa treatment may provide temporary improvement in horses with signs of chronic navicular area pain that fail to respond to other treatments.     

Mastocytoma in the common carpal sheath of the digital flexor tendons of a horse

A 13-year-old Morgan gelding was examined for right forelimb lameness and tenosynovitis of the right common carpal sheath of the digital flexor tendons. The horse had moderate right forelimb lameness at the trot and marked effusion of the right common carpal sheath of the digital flexor tendons. Ultrasonographic examination revealed a soft tissue mass within the proximal pouch of the affected tendon sheath, located adjacent to the distal physis of the radius. Cytology and culture of the fluid revealed a sterile, eosinophilic tenosynovitis. Tenoscopic exploration confirmed the presence of a capsulated soft tissue mass. Thecotomy was required to fully debride the mass, which histology revealed to be a mast cell tumour. At 22 months postoperatively, the horse developed mild right forelimb lameness and eosinophilic tenosynovitis because of recurrence of the mastocytoma. Mastocytosis is a possible differential diagnosis in any horse exhibiting lameness associated with tenosynovitis. Surgical excision combined with rest and postoperative intrasynovial and systemic corticosteroids may be palliative.     

MAGNETIC RESONANCE IMAGING FEATURES OF OBLIQUE AND STRAIGHT DISTAL SESAMOIDEAN DESMITIS IN 27 HORSES

Injury to the oblique and straight distal sesamoidean ligaments is becoming recognized as a more common cause of lameness in horses than was previously thought. The purpose of this study was to review the magnetic resonance (MR) imaging findings of 27 horses affected with desmitis of the oblique and/or straight distal sesamoidean ligament and determine long-term prognosis for horses with this diagnosis. Imaging was performed with horses in right lateral recumbency in a high-field 1 T magnet. All horses had lameness localized to the digit or metacarpophalangeal/metatarsophalangeal joint region with diagnostic local anesthetic blocks. Ten horses had forelimb lameness and 17 horses had hind limb lameness. MR imaging revealed abnormalities in the oblique distal sesamoidean ligaments in 18 horses, in the straight distal sesamoidean ligament in three horses, and in both the oblique and straight distal sesamoidean ligament in six horses. Treatment consisted of a 6-month rest and rehabilitation program in all horses. The digital flexor tendon sheath was injected with methylprednisolone acetate and hyaluronic acid in 22 horses to decrease inflammation in the injured ligaments before starting the rest and rehabilitation program. Two horses had ligament splitting performed, one in the oblique distal sesamoidean ligament and one in the straight distal sesamoidean ligament. MR imaging is an effective method for diagnosing injury to the oblique and straight distal sesamoidean ligaments in horses. Treatment, primarily a 6-month rest and rehabilitation program, allowed 76% of the horses to successfully resume performance.     

Can distal border fragments of the navicular bone be a primary cause of lameness?

A horse with unilateral forelimb lameness and pain localised to the palmar aspect of the foot was evaluated using radiography and low field magnetic resonance (MR) imaging. A distal border fragment of the navicular bone, an osseous cyst‐like lesion (OCLL) in the distal third of the navicular bone and focal distal sesamoidean impar desmitis were identified as the most likely causes of pain and lameness. No other lesions likely to contribute to pain and lameness were identified on MR images or gross post mortem examination. The OCLL was characterised histologically by enlarged bone lacunae containing proliferative fibrovascular tissue. Focal lesions of the distal aspect of the navicular bone are rarely found in isolation but can be causes of pain and lameness in horses.     

Arthroscopic removal of a palmar radial osteochondroma causing carpal canal syndrome in a horse.

A 5-year-old Arabian stallion with moderate effusion in the right carpal canal and intermittent lameness in this limb was diagnosed to have an osteochondroma projecting from the distal portion of the radius into the carpal canal. oral phenylbutazone treatment over the next 3 years allowed the stallion to continue its show career. Right forelimb lameness returned at that time, and ultrasonography revealed the osteochondroma impinging on the dorsal surface of the deep digital flexor tendon. The owner elected to have the osteochondroma surgically removed. The horse was anesthetized, and the carpal sheath was distended with balanced polyionic solution. A 4-mm arthroscope was inserted into the carpal sheath, and the osteochondroma projecting into the sheath was identified. The osteochondroma was removed by use of a Ferris-Smith bone rongeur, which was inserted into the carpal sheath through a stab incision over the osteochondroma. The effusion in the carpal sheath and the lameness resolved by 2 months, and the horse was returned to training 4 months after surgery.     

Tenectomy of the superficial digital flexor tendon as a treatment of suspected septic tendinitis and tenosynovitis of the digital flexor tendon sheath followed by rehabilitation with an orthotic device

A 15-year-old Sports horse gelding was referred for nonweightbearing lameness of the left hindlimb. Septic cellulitis was diagnosed and managed medically. After 14 days, septic tenosynovitis of the digital flexor tendon sheath (DFTS), with septic tendinitis of the superficial (SDFT) and deep (DDFT) digital flexor tendons, became evident. Surgical resection of the intrathecal portion of the septic SDFT was performed. Post-operatively, a half-limb cast was placed on the operated limb for 10 weeks followed by an articulated orthotic support boot during a rehabilitation period of 6 weeks. The horse recovered and regained long-term pasture soundness. Ultrasonography demonstrated the presence of bridging connective tissue in the location of the resected SDFT.     

The use of intrathecal analgesia and contrast radiography as preoperative diagnostic methods for digital flexor tendon sheath pathology

Reasons for performing study: The sensitivity of ultrasonography for the diagnosis of manica flexoria (MF) tears within the digital flexor tendon sheath (DFTS) is lower than for diagnosis of marginal tears of the deep digital flexor tendon (DDFT). Additional diagnostic tools would assist in appropriate decision making for either conservative or surgical management. Objectives: To evaluate the improvement in lameness of horses with MF or DDFT tears following intrathecal analgesia and to assess the sensitivity and specificity of contrast radiography for the diagnosis of these tears. Methods: The case records of horses presented to a referral clinic over a 7‐year period that underwent intrathecal diagnostic analgesia, or intrathecal analgesia and contrast radiography, of the DFTS with subsequent tenoscopy were examined. Results: Fifty‐three limbs had intrathecal diagnostic analgesia performed and 23 contrast tenograms were assessed in horses undergoing DFTS tenoscopy. Horses with DDFT tears were significantly more likely to respond positively to intrathecal diagnostic analgesia than those with MF tears (P = 0.02). Using contrast radiography, tears of the MF were predicted with an overall sensitivity of 96% and specificity of 80%; marginal tears of the DDFT were predicted with an overall sensitivity of 57% and specificity of 84%. Conclusions: The results of intrathecal analgesia of the DFTS in combination with contrast radiography have a high sensitivity for predicting MF tears. The sensitivity of contrast radiography for predicting tears of the DDFT is lower but the specificity remains high. Potential relevance: Contrast radiography performed at the same time as intrathecal analgesia provides useful information regarding the presence of MF tears and DDFT tears, which can assist in the decision of whether to manage the lameness conservatively or with tenoscopic evaluation.     

Effects of analgesia of the digital flexor tendon sheath on pain originating in the sole, distal interphalangeal joint or navicular bursa of horses

REASON FOR PERFORMING STUDY: Specific analgesic techniques are required in diagnosis of lameness to isolate the exact origin of pain to the many structures of the foot that may be involved. OBJECTIVE: To determine if analgesia of the digital flexor tendon sheath (DFTS) results in anaesthesia of other portions of the foot, such as the sole, distal interphalangeal joint (DIPJ), or navicular bursa (NB). METHODS: Lameness caused by pain in the dorsal margin or heel region of the sole of the foot was induced in 18 horses by: using set-screws to create solar pressure (Trial 1: n = 5); or administering endotoxin intrasynovially into the DIPJ (Trial 2: n = 6) and NB (Trial 3: n = 7). The gait of each horse was evaluated by examining videotape recorded before and after creation of lameness and after administration of mepivacaine hydrochloride into the DFTS. RESULTS: Median lameness scores in Trial 1 at 10 min post injection of the DFTS were not significantly different from those before administration of local anaesthetic solution into the DFTS (P> or =0.05), but median lameness scores were reduced significantly at 20 min (P< or =0.05). In Trials 2 and 3, median lameness scores were not significantly different at observations made at 10 and 20 min post injection of the DFTS. CONCLUSIONS: Analgesia of the DFTS has little effect on lameness caused by pain originating in the sole, DIPJ or NB. POTENTIAL RELEVANCE: Improvement of lameness in horses after intrasynovial analgesia of the DFTS is probably caused by attenuation of pain within the structures contained in the DFTS.     

The diagnosis of lameness associated with distal limbpathology in a horse: A comparison of radiography, computed tomography and magnetic resonance imaging

A cadaver limb from an eight-year-old horse with right forelimb lameness that was relieved with an intra-articular distal interphalangeal joint block was imaged with radiographs, spiral computed tomography (CT) and magnetic resonance imaging (MRI). Spiral CT demonstrated several lucencies within the deep digital flexor tendon immediately proximal to the navicular bone. On MRI these areas had increased signal and there was enlargement of the tendon at this site. Effusion in the proximal interphalangeal joint and navicular bursa and thinning of the fibrocartilage of the navicular bone were also observed on MRI images. These changes were not detected on radiographs. Histopathology confirmed that there were focal areas of collagen necrosis within the deep digital flexor tendon with thinning and degenerative changes in the fibrocartilage of the navicular bone.     

Mineralization of the supraspinatus tendon in dogs

Mineralization of the supraspinatus tendon is proposed as a cause of forelimb lameness in dogs. A new radiographic position (cranioproximal-cranio-distal) is advanced to detect abnormalities of the craniomedial aspect of the proximal portion of the humerus. Four dogs had surgery to remove mineralized debris from the supraspinatus tendon insertion and have improved limb function. Two dogs were evaluated in depth, with no signs of relapse 2 to 4 years after surgery. Other dogs, without apparent forelimb lameness, have had mineralization detected by use of radiography, thus emphasizing the need for thorough forelimb evaluation before determining that the mineralization is indeed the cause of lameness.     

The use of computed tomography to diagnose bilateral forelimb tendon pathology in a horse with unilateral lameness

A horse with unilateral forefoot lameness had bilateral deep digital flexor tendon (DDFT) lesions on computed tomography (CT). Venous contrast enhanced CT revealed distal sesamoidean impar desmitis in the lame forelimb. Computed tomography is useful for diagnosis of soft tissue lesions within the hoof capsule and contrast enhancement improves lesion conspicuity.     

Fracture repair of the distal portion of the radius by use of a condylar screw implant in an adult horse.

An 8-year-old American Quarter Horse gelding was evaluated because of an open fracture involving the left radius. The horse had fallen during training and became immediately non-weight-bearing in the left forelimb. On initial evaluation, the horse was unable to bear weight on that limb; radiography revealed a long oblique fracture of the distal metaphysis of the radius with minimal displacement of the fracture fragments. Because of the configuration of the fracture, we recommended surgical intervention with internal fixation. A condylar screw implant and 4.5-mm broad dynamic compression plate were applied to the medial and dorsolateral aspects of the radius, respectively. The horse recovered in a sling and full-limb bandage. Six months after discharge, the horse was reevaluated because of a grade 4/5 lameness in the same limb. Palpation revealed signs of severe pain over the distomedial aspect of the radius. Radiography of the left radius revealed severe osteolysis beneath the distal aspect of the condylar screw implant. Surgical removal of the medial plate was performed. Sixteen months after the initial fracture repair, the horse had returned to light training without signs of lameness. Removal of the dorsal plate may be indicated if this horse is to return to aggressive training or becomes lame in the left forelimb.     

Diagnostic analgesia of the equine digit

Analgesia usually occurs within 5 min after administration of local anaesthetic solution into joints or around nerves in the distal portion of the limb. Gait should be assessed within 10 min after diagnostic regional analgesia of the distal portion of the limb because rapid diffusion of anaesthetic solution can result in anaesthesia of other nerve branches, thus confusing results of the examination. A palmar digital nerve block (PDNB) anaesthetises most of the foot, including the distal interphalangeal (DIP) joint (coffin joint), rather than just the palmar half of the foot, as was once commonly believed. To avoid partially anaesthetising the proximal interphalangeal joint (pastern joint), the palmar digital nerves should be anaesthetised near or distal to the proximal margin of the collateral cartilages. Clinicians should be aware that an abaxial sesamoid nerve block (ASNB) may ameliorate or abolish pain within the metacarpo/metatarso‐phalangeal joint (fetlock joint). Mepivacaine administered into the DIP joint desensitises the DIP joint and probably the palmar digital nerves to also cause anaesthesia of the navicular bursa, the navicular bone, the toe region of the sole, the digital portion of the deep digital flexor tendon (DDFT) and the distal portions of the collateral ligaments of the DIP joint. When a large volume of mepivacaine HCl (e.g. 10 ml) is administered, the heel region of the sole may also be desensitised. Only a small percentage of horses with disease of the collateral ligament(s) of the DIP joint show a significant improvement in lameness after intra‐articular analgesia of the DIP joint, and no horse is likely to improve after intrabursal analgesia of the navicular bursa. A PDNB, however, improves lameness substantially in most horses that are lame because of disease of the collateral ligament(s) of the DIP joint, and all affected horses are likely to become sound after an abaxial sesamoid nerve block. The degree of improvement in lameness associated with injury to one or both collateral ligaments of the DIP joint after PDNB is determined by the extent of the injury and the level at which the palmar digital nerves are anaesthetised. The further proximal the level of the injury within the collateral ligament, the less likely that lameness is ameliorated by analgesia of the DIP joint or a PDNB. Verschooten's technique appears to be the most accurate technique for centesis of the navicular bursa. Even though analgesia of the DIP joint results in analgesia of the navicular bursa, analgesia of the navicular bursa does not result in analgesia of the DIP joint. Pain arising from the DIP joint can probably be excluded as a cause of lameness when lameness is attenuated by analgesia of the navicular bursa. Analgesia of the digital flexor tendon sheath (DFTS) is likely to desensitise only structures that are contained within or border on the sheath itself (i.e. the superficial and deep digital flexor tendons, the straight and oblique distal sesamoidean ligaments, the annular ligaments of the fetlock and pastern, and the portion of the DDFT that lies within the foot). Because lameness caused by disease of the DDFT within the foot may fail to improve appreciably after analgesia of the palmar digital nerves, the DIP joint, or the navicular bursa, a portion of the DDFT within the foot and distal to the DFTS probably receives its sensory supply from more proximal deep branches of the medial and lateral palmar digital nerves that enter the DFTS. Performing intrathecal analgesia of the DFTS on horses with lameness that is unchanged after anaesthesia of the palmar digital nerves but resolves after an ASNB, may be useful in localising lameness to that portion of the DDFT that lies within the foot. Resolution of lameness after intrathecal analgesia of the DFTS justifies suspicion of a lesion within the digital portion of the DDFT or within structures contained within the DFTS. The belief that concurrent or sequential intra‐articular administration of medication substantially increases the risk of joint infection or that inflammation caused by the local anaesthetic solution may dampen the therapeutic response to intra‐articular medication appears to be unfounded.     

USE OF CONTRAST-ENHANCED COMPUTED TOMOGRAPHY TO ASSESS ANGIOGENESIS IN DEEP DIGITAL FLEXOR TENDONOPATHY IN A HORSE

We compared contrast-enhanced computed tomography (CT) and high field magnetic resonance (MR) imaging in a horse with deep digital flexor tendonopathy. Lesions in the distal extremity were documented grossly and histopathologically. In contrast-enhanced CT, the deep digital flexor tendon lesions were markedly contrast enhancing with evidence of angiogenesis in the core and dorsal border lesions. The lesion morphology was clearly delineated on MR imaging, but without contrast media angiogenesis cannot be identified. Gross examination, histopathologic examination, and CD31 immunohistochemistry confirmed the tendonopathy and an increased presence of small blood vessels. In this horse, deep digital flexor tendon lesions appeared similarly on contrast-enhanced CT and MR imaging. Contrast-enhanced CT may be an alternative to MR imaging for assessing tendon and ligament injury in the digit of the horse.