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.     

CLINICAL AND DIAGNOSTIC IMAGING CHARACTERISTICS OF LATERAL DIGITAL FLEXOR TENDINITIS WITHIN THE TARSAL SHEATH IN FOUR HORSES

Lateral digital flexor tendonitis is a rarely reported cause of hind limb lameness in performance horses. The purpose of this retrospective study was to describe clinical and diagnostic imaging findings for a group of horses with lateral digital flexor tendinitis within the tarsal sheath. Equine cases with a diagnosis of lateral digital flexor tendonitis and magnetic resonance imaging (MRI) studies of the affected region were retrieved from North Carolina University's medical record database. Recorded data for included horses were signalment; findings from history, physical examination, lameness examination, and all diagnostic imaging studies; treatment administered; and outcome. Four horses met inclusion criteria. Lameness was mild/moderate in severity and insidious in onset in all patients. Responses to flexion tests were variable. All horses showed positive improvement (70–90%) in lameness after tarsal sheath analgesia. Radiographic, scintigraphic, and ultrasonographic findings were inconclusive. For all horses, MRI characteristics included increased T2, PD, and STIR signal intensity within the lateral digital flexor tendon in the area of the tarsal sheath. Tarsal sheath effusion was slight in three horses, and mild/moderate in one horse. With medical treatment, two horses were sound at 6‐month followup, one horse was sound at 1‐year followup, and one horse had a slight persistent lameness (grade 1/5) at 9‐month followup. Findings supported the use of MRI for diagnosing lateral digital flexor tendonitis within the tarsal sheath in horses. Affected horses may have a good prognosis for return to athletic performance following appropriate medical treatment.     

Surgical treatment of tarsal sheath effusion associated with an exostosis on the calcaneus of a horse

A 2-year-old Thoroughbred colt was referred for evaluation of effusion within the tarsal sheath and associated lameness of the right hind limb. Conservative treatment consisting of needle aspiration and pressure bandaging had been unsuccessful. Radiography of the right tarsus revealed proliferative periosteal reaction along the distal caudal border of the sustentaculum tali and medial aspect of the calcaneus. The owners elected conservative treatment, using a local injection of corticosteroid and pressure bandaging the tarsus. Five months later, the severity of the effusion and lameness had increased. Radiography revealed increased reactive bone along the sustentaculum tali and mineralization of the plantar tarsal ligament and tarsal sheath. Surgical exploration revealed fibrous adhesions between the medial aspect of the calcaneus and the flexor tendon and associated soft tissue mineralization. The adhesions were broken down and the reactive bone along the calcaneus was removed. The mineralized soft tissue within the tarsal sheath was excised. Five months after surgery, the horse was sound at the trot, with only minimal tarsal sheath effusion. The response to treatment for tarsal sheath effusion and lameness caused by bony changes of the sustentaculum tali is often unsatisfactory. After responding poorly to conservative treatment, the horse in this report had a favorable outcome to the surgical intervention of this condition.     

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.     

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.     

Exostoses of the caudal perimeter of the radial physis as a cause of carpal synovial sheath tenosynovitis and lameness in horses: 10 cases (1999-2003)

OBJECTIVE: To determine the clinical, radiographic, ultrasonographic, and arthroscopic findings associated with tenosynovitis of the carpal synovial sheath induced by exostoses that originate from the caudal surface of the physeal scar of the distal radius and determine the results of surgical removal of those exostoses in horses. DESIGN: Retrospective study. ANIMALS: 10 horses. PROCEDURE: Medical records of horses with effusion in the carpal synovial sheath and lameness evaluated from 1999 to 2003 were examined. RESULTS: All horses had a history of intermittent mild to moderate effusion of the carpal synovial sheath and lameness of 1 forelimb. Results of regional perineural and intrathecal anesthesia of the carpal synovial sheath confirmed that the lameness originated in the carpal synovial sheath. Radiography revealed exostoses originating from the caudal cortex of the distal radius at the level of the closed physis. Arthroscopy was performed for confirmation and removal of exostoses that penetrated the carpal synovial sheath and impinged on the deep digital flexor tendon. All horses returned to previous athletic activity. One horse had a recurrence of clinical signs 12 months after surgery, which resolved with medical treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Tenosynovitis of the carpal synovial sheath and lameness were caused by impingement of exostoses of the caudal radius on the lining and contents of the carpal synovial sheath. Although the clinical signs and surgical treatment were similar to that caused by osteochondromas, these exostoses developed at the level of the closed physis of the distal radius and were not radiographically or histologically similar to osteochondromas.     

Carpal hyperextension in a Percheron mare caused by a palmar carpal ligament tear

A Percheron mare was presented for acute, severe lameness and marked swelling of the right forelimb after being cast. The mare was initially diagnosed with cellulitis of the forelimb but as her condition improved and the affected limb was able to bear more weight it became apparent that the limb was hyperextended at the level of the carpus. Widening of the palmar aspect of the middle carpal joint was observed radiographically. During ultrasonographic examination, excessive fluid in the carpal sheath and perithecal swelling were noted and tearing of the palmar carpal ligament was suspected. A dynamic brace was fabricated to prevent hyperextension of the carpus. After discontinuation of systemic antibiotics, the mare became febrile and forelimb lameness worsened. Cytology of fluid from the middle carpal joint confirmed joint sepsis and the mare was anaesthetised for arthroscopic examination. A tear in the palmar carpal ligament, characterised by focal fibre disruption and fibrillation, was identified during arthroscopic and tenoscopic examination. Communication between the carpal flexor tendon sheath and middle carpal joint was identified during these procedures. Both the middle carpal joint and carpal flexor tendon sheath were lavaged with physiological saline solution. Post operatively, swelling and lameness slowly resolved. Four months after discharge, the mare was sufficiently sound to be maintained at pasture. Viewed from its lateral aspect, the limb no longer appeared to be hyperextended from the carpus.     

Dynamic flexion/extension and non‐weight bearing ultrasonography is helpful for identifying manica flexoria tears in horses

Lesions of the manica flexoria are a tenoscopic finding in horses with digital flexor tendon sheath tenosynovitis. This retrospective case series study describes the ultrasonographic findings in seven horses admitted for digital flexor tendon sheath swelling associated with lameness and tenoscopic confirmation of a manica flexoria tear. Six horses had a partial manica flexoria tear, one a complete rupture. The ultrasonographic examination included a static examination on the weight and non‐weight bearing limb and a dynamic limb assessment during flexion and extension. The main ultrasonographic finding at the static weight bearing examination in horses with a partial tear was an asymmetrical appearance of the manica flexoria at the level of the junction with the lateral border of the superficial digital flexor tendon, or an incomplete visualization of the manica flexoria in case of complete rupture. The split edges of the completed ruptured manica flexoria were seen floating in the synovial fluid at the examination in flexion. In six of seven cases, the superficial digital flexor tendon slid abnormally relative to the deep digital flexor tendon, during flexion/extension movements, with medial displacement of the superficial digital flexor tendon, appearance of an anechoic gap between the flexor tendons or reduced superficial digital flexor tendon sliding. Because ultrasonographic diagnosis of the manica flexoria tear is considered challenging, detection of these ultrasonographic features is helpful to increase the likelihood of identifying manica flexoria tears prior to tenoscopy. Authors recommend static ultrasonographic examination of the manica flexoria using a flexed limb position and dynamic ultrasonographic examination using flexion and extension positioning for horses with suspected digital sheath injury.     

Deep digital flexor tendonopathy in the foot

Tendonopathy of the distal portion of the deep digital flexor tendon is a newly recognised, important cause of foot lameness in horses. Although the pathological morphology of lesions has been well described, the aetiopathogenesis remains uncertain. A conclusive diagnosis can only be made with magnetic resonance imaging, but the results of a thorough clinical examination, including regional analgesia and other imaging modalities may lead to a strong suspicion of deep digital flexor tendonopathy in the foot. The prognosis for return to soundness is guarded but new treatment modalities are currently being investigated for an improved outcome.     

Endoscopic examination of the tarsal sheath of the lateral digital flexor tendon in horses.

This study was designed to develop a reliable technique for endoscopic examination of the tarsal sheath of the lateral digital flexor tendon of horses. The anatomy of the tendon sheath and associated structures was studied in detail in cadavers before determining portals for the insertion of an arthroscope into the sheath. Approaches into the sheath through the proximal pouch and through the flexor retinaculum, at the level of the sustentaculum tali, were performed and compared in cadavers. The proximal pouch portal permitted visualisation only of the proximal half of the sheath, while the approach through the retinaculum allowed examination of the entire sheath. The normal endoscopic appearance of the tarsal sheath was studied. The endoscopic approach was subsequently used to examine and treat 5 horses with tarsal sheath tenosynovitis, including 2 cases of chronic, traumatic tenosynovitis and 3 of subacute septic tenosynovitis. Four of these horses had fragmentation of the sustentaculum tali. The technique allowed adequate examination of the sheath and debridement of adhesions and lesions within the lumen of the sheath. Fragments dorsal to the medioplantar edge of the sustentaculum tali could not be visualised endoscopically and had to be removed after widening of the wound. All 5 horses survived. Follow-up enquiries (8-31 months) revealed that the horses were all reported to be sound. Four were performing at their previous level of activity, 1 was used for hacking. The 2 cases presented with chronic tenosynovitis had residual sheath distension with no associated loss of function. A prospective study, including longer term follow-up investigation, is currently being performed.     

MUSCULOSKELETAL LESIONS AND LAMENESS IN 121 HORSES WITH CARPAL SHEATH EFFUSION (1999–2010)

Equine carpal sheath effusion has multiple etiologies. The purpose of this retrospective study was to describe the prevalence of distinct musculoskeletal lesions lameness in a sample of horses with a clinical diagnosis of carpal sheath effusion. A total of 121 horses met inclusion criteria. Seventy‐four percent (89/121) of horses were lame at presentation; middle‐aged (9–18 years, 80%) and older (> 18 years, 85%) horses were lame more frequently than young horses (< 9 years, 44%). Ninety‐three percent (113/121) were diagnosed with osseous and/or soft tissue abnormalities. Of these 113 horses, 10 exhibited osseous abnormalities, whereas 111 were diagnosed with soft tissue lesions. Eighty‐four percent (93/111) of the soft tissue injuries extended from the caudodistal antebrachium to the palmar metacarpus. The superficial digital flexor tendon (98/111; 88%) and accessory ligament of the superficial digital flexor tendon (64/111; 58%) were the most commonly injured structures, with both structures affected in 41 (41/111; 37%) horses. Injuries within the caudodistal antebrachium included the superficial digital flexor musculotendinous junction (66), the accessory ligament of the superficial digital flexor tendon (64), and deep digital flexor muscle (21), in isolation or in combination with other structures. Increased echogenicity in the medial superficial digital flexor musculotendinous junction was detected in 40 horses and was significantly associated with increasing age (middle‐aged, 19/40; old, 18/40). Findings from this study indicated that age should be taken into consideration for horses presented with carpal sheath effusion and that adjacent structures within the caudodistal antebrachium should be included in evaluations.     

Evaluation of a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon in horses

Objective: To develop a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon (AL‐DDFT) in horses. Study Design: Experimental. Animals: Cadaveric forelimbs (n=10) and 4 forelimbs from 2 horses anesthetized for terminal teaching procedures, and 12 forelimbs of 6 experimental horses. Methods: Saline distention of the carpal flexor sheath facilitated insertion of an arthroscope into the distal medial aspect of the sheath between the AL‐DDFT and deep digital flexor tendon (DDFT). Location of an instrument portal on the lateral aspect of the metacarpus was identified with a needle. The lateral aspect of the AL‐DDFT was transected and the arthroscope and instrument were switched to transect the remaining fibers on the medial aspect. Cadaveric specimens were dissected for evaluation. Experimental horses were monitored for 30 days postoperatively. Results: Minor complications including incomplete division of the AL‐DDFT and shallow incision into the suspensory ligament were observed in some cadaver specimens. The AL‐DDFT was completely transected in all experimental horses with no suspensory ligament damage. Mean±SD surgical time (incision to skin closure) was 28.3±11.8 minutes. On ultrasonographic examination, transection of the AL‐DDFT was complete in all experimental horses. Minor DDFT fiber disruption was noted in 1 limb during ultrasound examination at day 30. Conclusions: A tenoscopic approach through the carpal flexor sheath provided adequate access for desmotomy of the AL‐DDFT.     

Tenosynovitis of the carpal sheath of the digital flexor tendons associated with tears of the radial head of the deep digital flexor: observations in 11 horses

Reasons for performing study: Tears of the radial head of the deep digital flexor (DDF) have not previously been documented. Objectives: To describe the presentation, clinical, ultrasonographic and tenoscopic features associated with tears of the radial head of the DDF and to report the results of treatment. Hypotheses: Tears of the radial head of the DDF cause lameness and distension of the carpal sheath of the digital flexor tendons. Removal of disrupted tissue that is extruded into the sheath can result in clinical resolution and restoration of function. Methods: Case records and diagnostic images of horses in which tearing of the radial head of the DDF was diagnosed were reviewed retrospectively and follow‐up information obtained. Results: Eleven cases were identified. Clinical, ultrasonographic and tenoscopic commonality was recorded and treatment techniques were documented. All cases returned post operatively to pre‐injury levels of work. Conclusion: Tearing of the radial head of the DDF is a clinical entity with consistent diagnostic features. Tenoscopic removal of the torn tissue is associated with a good outcome. Potential relevance: Clinicians evaluating lame horses should include tearing of the radial head of the DDF as a differential diagnosis in animals with distended carpal sheaths. Tenoscopic surgery is a recommended treatment.     

Desmotomy for treatment of chronic desmitis of the accessory ligament of the deep digital flexor tendon in a horse.

Chronic lameness was determined to be caused by desmitis of the accessory ligament of the deep digital flexor tendon and adhesions associated with these 2 structures. Desmotomy of the accessory ligament, resection of adhesions, and controlled exercise during convalescence resulted in return to normal use without apparent lameness.     

Treatment and outcome of chronic tenosynovitis in three horses

Three horses were presented for treatment of chronic infections of the digital flexor tendon sheath. Clinical signs included severe lameness, and heat, pain and swelling of the digital flexor tendon sheath. The horses were treated with surgical lavage of the tendon sheath, systemic and local antibiotics, and analgesics. In each case, resolution of the lameness occurred over weeks to months. Only one horse returned to athletic activity, while the other two became comfortable at pasture. Response to treatment in cases of chronic tenosynovitis may not be as rapid or complete as that reported for acute tendon sheath infections.     

Treatment and outcome of chronic septic tenosynovitis in three horses

Three horses were presented for treatment of chronic infections of the digital flexor tendon sheath. Clinical signs included severe lameness, and heat, pain and swelling of the digital flexor tendon sheath. The horses were treated with surgical lavage of the tendon sheath, systemic and local antibiotics, and analgesics. In each case, resolution of the lameness occurred over weeks to months. Only one horse returned to athletic activity, while the other two became comfortable at pasture. Response to treatment in cases of chronic tenosynovitis may not be as rapid or complete as that reported for acute tendon sheath infections.     

Computed tomographic contrast tenography of the digital flexor tendon sheath of the equine hindlimb

Pre‐surgical investigation of digital flexor tendon sheath pathology remains challenging with current standard imaging techniques. The aim of this prospective, anatomical, pilot study was to describe the anatomy of the equine hind limb digital flexor tendon sheath using a combination of computed tomography (CT) and computed tomographic contrast tenography in clinically normal cadaver limbs. Ten pairs of hind limbs with no external abnormalities were examined from the level of the tarsometatarsal joint distally. Limbs initially underwent non‐contrast CT examination using 120 kVp, 300 mAs, and 1.5 mm slice thickness. Sixty millilitres of ioversol iodinated contrast media and saline (final concentration 100 mg/ml) were injected using a basilar sesamoidean approach. The computed tomographic contrast tenography examination was then repeated, before dissection of the specimens to compare gross and imaging findings. The combined CT and computed tomographic contrast tenography examinations provided excellent anatomical detail of intra‐thecal structures. The borders of the superficial and deep digital flexor tendons, and the manica flexoria were consistently identifiable in all limbs. Detailed anatomy including that of the mesotenons, two of which are previously undescribed, and the plantar annular ligament were also consistently identifiable. Dissection of all 10 pairs of limbs revealed there to be no pathology, in accordance with the imaging findings. In conclusion, the combination of CT and computed tomographic contrast tenography may be useful adjunctive diagnostic techniques to define digital flexor tendon sheath pathology prior to surgical exploration in horses.     

Tenoscopic-assisted treatment of open digital flexor tendon sheath injuries in horses: 20 cases (1992-2001)

OBJECTIVE: To determine history, physical and diagnostic examination findings, medical treatment, and outcome of horses with open injuries to the digital flexor tendon sheath treated with the assistance of tenoscopy. DESIGN: Betrospective study. ANIMALS: 20 horses. PROCEDURE: Medical records of 20 horses with open injuries to the digital flexor tendon sheath were reviewed. Signalment, history, physical and diagnostic examination results, bacteriologic culture and susceptibility testing results, surgical and medical treatments, and follow-up examination results were determined. Outcome was determined by use of telephone interview or physical examination. RESULTS: All horses were treated with tenoscopic-assisted lavage and debridement. Eighteen horses survived, and 2 were euthanatized during treatment. All horses were either grade-4 or grade-5 lame before treatment. Ten horses returned to previous use. Four horses were considered mildly lame and in athletic use. Three horses were considered mechanically lame and are in use with reduced expectations. One horse was lost to follow-up after being sold. One horse was euthanatized for financial reasons and 1 because of complications from regional sepsis. CONCLUSIONS AND CLINICAL RELEVANCE: Tenoscopy appears to be a useful modality in the treatment of open injury to the digital flexor tendon sheath in horses. Direct viewing, guided debridement, and targeted large-volume lavage are advantages obtained with intrathecal arthroscopy. Tenoscopy, when combined with antimicrobial and anti-inflammatory treatment, appears to offer a good chance of survival for affected horses.