Osseous cyst‐like lesions in the feet of lame horses: Diagnosis by standing low‐field magnetic resonance imaging

Osseous cyst‐like lesions (OCLLs) were diagnosed by standing low‐field magnetic resonance (MR) imaging in 9 mature horses (age range 6–17 years). All horses had been subjected to a routine lameness evaluation (including standard foot radiographs) with no diagnosis being reached prior to MR imaging. The duration of lameness ranged from one month to one year. OCLLs were diagnosed in 12 feet. The site of the lesions included the distal phalanx in 11 feet (subchondral bone in 4, insertion of collateral ligaments of the distal interphalangeal joint in 4, insertion of the distal sesamoidean impar ligament in 3) and the subchondral bone of the distal aspect of the middle phalanx in one foot. OCLLs were characterised by discrete spherical or elliptical areas of high or intermediate signal in all MR sequences. In most cases the lesion was surrounded by a rim of bone with abnormally low signal.     

Long-Term Outcome in 44 Horses with Stifle Lameness After Arthroscopic Exploration and Debridement

Objective— To (1) examine the outcome in horses with osteoarthritis or intra‐articular soft tissue injuries of the stifle after arthroscopic exploration and debridement and (2) to determine any imaging or surgical findings that may influence prognosis. Design— Case series. Animals— Horses (n=44) with lameness referable to the stifle, diagnosed with osteoarthritis, meniscal tears, or other intra‐articular soft tissue injuries based on arthroscopic examination. Methods— Medical records of horses with stifle lameness that had arthroscopic exploration were reviewed. Horses with osteochondrosis lesions, intra‐articular fractures, or osseous cyst‐like lesions were excluded. Pertinent case information was analyzed and short‐ and long‐term outcome was assessed. Results— There was no association between radiographic score and surgery score. Diagnostic ultrasound had a sensitivity of 79% and a specificity of 56% for identifying meniscal injuries. Follow‐up information was available for 35 horses; 23 horses (60%) improved after surgery, 16 (46%) became sound, and 13 (37%) returned to their previous level of function. A negative association was observed between age and degree of preoperative lameness and outcome. More severe changes observed on preoperative radiographs were also negatively associated with prognosis. No horses with grade 3 meniscal tears improved postoperatively and increasing meniscal pathology was negatively associated with return to previous function. A weak association between surgery grade and outcome was also observed. Degree of chondral damage, location of primary pathology, and microfracture techniques had no effect on outcome. Conclusions— Advanced horse age, severe lameness and preoperative radiographic changes, and presence of large meniscal tears are associated with a negative postoperative outcome for horses with stifle lameness. Appearance of the articular surface at surgery appears to be an inconsistent prognostic indicator. Clinical Relevance— Some horses with extensive cartilage damage may return to athletic function after arthroscopic debridement and lavage. A more pessimistic prognosis may be given to older horses, those with more severe preoperative lameness, and those with severe radiographic changes or large meniscal tears.     

Osseous cyst‐like lesions of the lateral intertubercular groove of the proximal humerus: A report of 5 cases

This report documents the case presentation, evaluation, treatment and outcome of 5 horses with an osseous cystlike lesion (OCLL) of the intertubercular groove of the proximal aspect of the humerus. In 3 of the 5 cases, delayed phase gamma scintigraphic findings demonstrated increased radiopharmaceutical uptake in the region of the intermediate tubercle of the proximal humerus of the affected limb, demonstrating increased bone remodelling in this region. In 4 of the 5 horses, an OCLL was identified in the intermediate tubercle of the proximal humerus, and in one horse the OCLL was identified in the greater tubercle. Medial‐lateral and craniomedial‐caudolateral oblique radiographic views were helpful to see the lesions in all cases. Ultrasonography confirmed the location of the subchondral and fibrocartilage defect associated with the OCLL and confirmed communication of the cyst with the lateral intertubercular groove of the humerus in 3 of the 5 cases. Ultrasonography also confirmed a variable degree of bicipital tendonitis in 3 of the horses. OCLL of the lateral intertubercular groove of the proximal humerus should be considered in the evaluation of any mature horse with lameness isolated to the bicipital bursa. Development of these OCLL may be a result of trauma or altered limb biomechanics as a result of shoulder osteoarthritis or concurrent chronic lameness, which leads to disruption or thinning of the fibrocartilage, remodelling of the subchondral bone and subsequent cyst development.     

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.     

Acquired peri-articular ganglion cyst in the lateral femorotibial joint in an 18-year-old Percheron cross mare

This report describes a case of sudden lameness in an 18-year-old Percheron cross mare after presumably being kicked by another horse, and the subsequent formation of a ganglion cyst originating from the lateral femorotibial joint. Physical examination, radiographic and ultrasonographic investigation identified a soft round 5 cm diameter mass attached to the left lateral femorotibial joint. After surgical removal, histopathological examination confirmed a ganglion cyst. The horse responded well to the surgical removal of the cyst, and 4 weeks after the surgery, the mare has returned back to her same athletic performance. According to the authors’ knowledge, this is the first reported case that describes a peri-articular ganglion cyst originating from the stifle joint.     

Diagnostic imaging of the equine fetlock region using radiography and ultrasonography. Part 2: the bony disorders

The metacarpophangeal/metatarsophalangeal (fetlock) joint in the horse is commonly associated with equine lameness and diagnostic imaging is routinely used to investigate disorders of the joint and its surrounding tissues. This review describes the osseous disorders of the fetlock as well as the technical aspects of taking radiographic and ultrasonographic images of the different lesions. In current clinical practice, a combination of radiography and ultrasonography is still the most frequently used approach to arrive at a diagnosis.     

Arthroscopic treatment of meniscal cysts in the horse

Reasons for performing study: To describe the clinical symptoms, treatment, and outcome of meniscal cysts in horses. These structures have not been previously described in the literature as a potential cause of lameness in the horse. Hypothesis: Meniscal cysts are an uncommon condition of the femorotibial joint but can be a significant cause of lameness. Symptoms can be resolved by arthroscopic excision. Methods: Records of horses diagnosed with meniscal cysts and treated by cyst excision and meniscal debridement at 2 surgical practices were reviewed. Clinical outcome was determined by repeat veterinary examination and contact with owner. Results: Seven cases of meniscal cyst were treated with arthroscopic cyst excision and meniscal debridement. Five of 7 horses had lameness attributable to femorotibial joint pathology, while the remaining 2 horses had meniscal cysts found incidentally during diagnostic arthroscopy for the treatment of osteochondritis dissecans of the lateral trochlear ridge of the femur. Five of 6 horses with long‐term follow‐up were sound and a 7th horse was improved 11 months after surgery. Conclusions and potential relevance: Meniscal cysts, while uncommon, can be associated with progressive lameness in the horse. Surgical excision of the cysts results in resolution or improvement of symptoms, without evidence of recurrence on follow‐up examination.     

Use of computed tomography to evaluate a fracture associated with a subchondral pedal bone cyst in a horse

The radiological examination of bone lesions can be challenging, considering the complex superimposition of the 3D anatomy of a region on to a 2D image. This report describes the findings achievable with different diagnostic imaging modalities (radiography, arthrography, spiral computed tomography) and the correlation with the post mortem and histopathological findings in a horse with a fracture associated with an osseous cyst‐like lesion in the third phalanx. CT was highly superior to radiography to evaluate the spatial configuration and completeness of the fracture, relationship between the fracture and osseous cyst‐like lesion, architecture of the cyst, presence of its communication with the joint and secondary degenerative joint disease. In conclusion, CT represents an asset in these cases for an accurate prognosis and therapy.     

Severe lameness associated with an impact fracture of the proximal phalanx in a filly

A 3‐year‐old filly was presented for severe lameness referable to the left front fetlock joint. Radiographs confirmed an osseous cyst‐like lesion and synovial fluid cytology ruled out sepsis. The filly responded poorly to medical management and was subsequently subjected to euthanasia. Post mortem examination confirmed an impact fracture of the proximal phalanx, previously undiagnosed in the horse.     

Osteolytic lesions of the tuber calcanei in two horses

Two adult horses were evaluated for chronic hind limb lameness. Nonseptic calcanean bursitis with associated focal osteolytic lesions at the point of insertion of the gastrocnemius tendon was diagnosed in each horse by physical and lameness examinations, radiography, ultrasonography, and synovial fluid analysis. Both horses underwent arthroscopic exploration and lavage of the affected bursa, and one horse also underwent surgical debridement of the osseous lesion. Both horses remained lame for 13 months after the surgical procedures. To our knowledge, osseous lesions of the calcaneus in horses with nonseptic calcanean bursitis have not been reported. The flexed proximoplantar-to-distoplantar tangential radiographic view of the calcaneus was essential in localizing the lesions, as was the sonogram in one horse. Arthroscopy provided a thorough evaluation of the bursa and associated tendons. On the basis of the outcome of these 2 horses, the prognosis for complete recovery for horses with this condition appears to be unfavorable. Surgical debridement of the osseous lesion was of no benefit and may have been detrimental.     

Unusual osteochondral lesions of the talus in a horse

A 2-year-old Thoroughbred gelding was evaluated for a grade 3 out of 5 unilateral hind limb lameness. Flexion of the right hock and stifle joints (spavin test) exacerbated the lameness. Response to intra-articular and perineural anaesthesia isolated the source of lameness to the tarsocrural area, despite an absence of tarsocrural joint effusion. Routine radiographic examination of the hock did not reveal any significant abnormalities. Skeletal nuclear scintigraphic evaluation revealed a focal region of increased bone activity in the proximal medial trochlear ridge of the talus. Flexed lateromedial radiographic views identified three discrete semicircular lytic lesions at the proximal articular margin of the medial trochlear ridge of the talus. Conservative management of the lesions was associated with a successful return to racing. The location and appearance of the osteochondral lesions of this report have not been previously reported and may be a manifestation of developmental orthopaedic disease and abnormal endochondral ossification. Nuclear scintigraphy and flexed lateromedial radiographic views facilitated identification of the lesions. This radiographic view is recommended when lameness is isolated to the tarsocrural joint and standard radio-graphic projections fail to identify a cause.     

Use of magnetic resonance imaging for identifying subchondral bone damage in horses: 11 cases (1999-2003)

OBJECTIVE: To assess the use of magnetic resonance (MR) imaging for identifying subchondral bone damage in the distal limbs of horses. DESIGN: Retrospective study. ANIMALS: 11 horses. PROCEDURE: Medical records of horses with lameness and subsequent evidence of subchondral bone damage as determined by MR imaging were reviewed. Severity and duration of lameness, results of diagnostic local anesthesia and diagnostic testing, surgical and necropsy findings, and treatment were recorded. Outcome was determined by follow-up information obtained from the owner or referring veterinarian. RESULTS: Lameness was localized by physical examination and diagnostic local anesthesia. Lameness was localized to the metacarpophalangeal or metatarsophalangeal joint in 4 horses, distal interphalangeal joint in 5 horses, and tarsocrural joint in 2 horses. The duration of lameness ranged from 2 weeks to 20 months. Magnetic resonance imaging of the affected joints revealed abnormal fluid accumulation within the subchondral bone. None of the abnormalities observed by MR imaging were detected by radiography. Subchondral bone damage was diagnosed in all horses. Arthroscopy of the affected joint was performed in 4 horses. Communication with the articular surface of the affected bone was suspected on the basis of results of MR imaging in 4 horses and was confirmed by arthroscopy in 1 horse and by necropsy in 1 horse. CONCLUSIONS AND CLINICAL RELEVANCE: Magnetic resonance imaging was useful for providing a diagnosis when other imaging techniques did not definitively identify the cause of lameness. Subchondral bone damage was clearly identified by MR imaging and should be considered as a cause of lameness in horses in which radiographic findings are unremarkable.     

Occult subchondral osseous cyst-like lesions of the equine tarsocrural joint

OBJECTIVE: To report the clinical signs, diagnosis, management, and outcome of horses with occult sub-chondral osseous cyst-like lesions of the tarsocrural joint. DESIGN: Retrospective study. ANIMALS: Twelve horses with subchondral osseous cyst-like lesions (SOCLs) in the tarsocrural joint. METHODS: Information about history, examination findings, diagnostic techniques, and surgical procedures as obtained from medical records. Outcome was determined by patient re-evaluation and telephone communication with the referring veterinarian, owner, or trainer. RESULTS: Horses were aged from 3 to 29 years. Lameness (2 weeks to 1 year) varied from moderate to severe. Synovial fluid analyses (9 horses) yielded changes consistent with suppurative inflammation and positive bacterial culture was obtained in 4 horses. Eight of 9 horses that had intra-articular analgesia had a dramatic reduction in lameness. No abnormalities were detected on tarsal radiographs in 10 horses. Scintigraphy identified foci of increased radiopharmaceutical uptake in the distal tibia or talus of all horses, and the lesion was further characterized by computed tomography in 7 horses. SOCLs were identified in the medial malleolus (5), intertrochlear groove of the talus (4), lateral malleolus (2), and distal intermediate ridge of the tibia (1). One horse was euthanatized, 6 horses had surgical debridement, and 5 horses were managed conservatively. Four horses treated surgically (67%) returned to soundness. Conservatively treated horses continued to exhibit lameness but 2 were sufficiently sound for light pleasure riding. CONCLUSIONS: Occult lesions of the tarsus not visible on radiographs can be detected by computed tomography and scintigraphy and may be a source of lameness. CLINICAL RELEVANCE: SOCL, possibly of septic origin, should be a differential diagnosis for persistent lameness localized to the tarsocrural joint without radiographic abnormalities. Surgical debridement of the lesions may offer the best prognosis for a return to athletic soundness.     

OSSEOUS LESIONS IN THE METACARPO(TARSO)PHALANGEAL JOINT DIAGNOSED USING LOW-FIELD MAGNETIC RESONANCE IMAGING IN STANDING HORSES

We report the use of low-field standing magnetic resonance imaging in the standing horse for the diagnosis of osseous lesions in the metacarpophalangeal (MCP) or metatarsophalangeal (MTP) joint that were not apparent using standard radiography. Thirteen horses were studied and all had thickening of the subchondral bone plate and abnormal signal intensity in the adjacent spongiosa in either the condyles of metacarpal/metatarsal III or the proximal phalanx or both. Abnormalities were characterized by diffuse decreased signal intensity on T1-weighting adjacent to the subchondral bone and within the spongiosa in at least two imaging planes; in the absence of increases in signal intensity in fat-suppressed images, this change was interpreted as bone sclerosis. Nine horses also had a diffuse decreased signal intensity on T2^*-weighting in the same areas and five had a diffuse increase in signal intensity in fat-suppressed images in conjunction with a decrease in signal intensity on T1- and T2^*-weighted images; the increase in signal intensity in fat-suppressed images was interpreted as fluid accumulation. Five horses had a focal area of change in signal intensity within the subchondral bone with apparent loss of definition between the subchondral bone and the articular cartilage. Eleven horses were available for follow up, of which eight were sound and three remained lame. We conclude that lameness originating from the MCP or MTP joint may be associated with osseous damage in horses of any signalment in the absence of radiographic changes.     

Clinical and low field magnetic resonance imaging features of osseous cyst‐like lesions of the proximal sesamoid bones in seven horses

Osseous cyst‐like lesions of the proximal sesamoid bones (PSBs) were diagnosed in 7 horses. The diagnosis was achieved radiographically prior to magnetic resonance imaging (MRI) in only one horse, and in the other 6 horses the diagnosis was made using low field MRI (retrospective evaluation of the radiographs after the MRI revealed ill‐defined radiolucencies of the PSBs in 4 of these horses). The horses ranged in age from 3 to 12 years, and the affected limbs included 3 forelimbs and 4 hindlimbs. The onset of lameness was reported to be sudden in 6 horses and insidious in one, and the duration of lameness at the time of MRI ranged from 0.3 to 11 months. The degree of lameness in the 6 horses with sudden‐onset lameness was moderate to severe. Pain on flexion of the affected metacarpo(tarso)phalangeal (fetlock) joint or exacerbation of the degree of lameness following fetlock flexion was recorded in 4 of the 7 horses. The MRI findings in all cases included a focal high signal intensity lesion (all magnetic resonance sequences) at various locations in one PSB. Both septic and nonseptic aetiologies were identified. Four of the 7 horses were subjected to euthanasia due to persistent lameness, one remained chronically lame and only 2 were able to return to their previous level of exercise.     

Is there a relationship between clinical presentation,diagnostic and radiographic findings and outcome in horses with osteoarthritis of the small tarsal joints?

Reasons for performing study: Despite the possibility that sound horses may have radiographic signs consistent with osteoarthritis of the small tarsal joints (OA‐STJ), a diagnosis of ‘bone spavin’ as a cause of lameness is often made based only on radiographic examination. Objectives: To determine whether severity of radiographic change and response to treatment are correlated with the duration and degree of lameness and the response to intra‐articular anaesthesia in horses with OA‐STJ. Methods: A retrospective study of all horses that showed a positive response to intra‐articular anaesthesia of the STJ was performed. Details of history, clinical presentation and diagnostic findings were recorded. Radiographs of affected tarsi were evaluated and scored independently by 2 observers. Follow‐up was via a telephone questionnaire with the owner. Statistical analysis was used to assess the association between the duration and degree of lameness, the response to intra‐articular anaesthesia and radiographic findings. Response to treatment was compared with the findings from the diagnostic work‐up. Results: Ninety‐one horses were included (61 unilateral and 30 bilateral lameness). Fifty‐nine percent of horses had been lame for over 2 months. There was no association between the duration and degree of lameness, or between duration or degree of lameness, intra‐articular anaesthesia and radiographic findings. Response to treatment showed a significant positive association with less severe radiographic changes within the tarsometatarsal (TMT) joint. Follow‐up was available for 48% of cases, with 52% horses returning to the same level of exercise. Conclusions: There is no association between the duration and degree of lameness, the response to intra‐articular anaesthesia and radiographic findings in horses with OA‐STJ. However, horses that improved following treatment tended to have less marked TMT joint pathology. Potential relevance: Response to intra‐articular anaesthesia should remain the gold standard for diagnosis of OA‐STJ. Predicting which cases are likely to improve following treatment remains difficult.     

Removal of large fragments of the extensor process of the distal phalanx via arthrotomy in horses: 14 cases (1992-1998)

OBJECTIVE: To evaluate the outcome of horses with large fragments of the extensor process of the distal phalanx that were removed by use of arthrotomy. DESIGN: Retrospective study. ANIMALS: 14 horses with large fragments of the extensor process of the distal phalanx. PROCEDURE: Medical records for horses with large fragments of the extensor process that were removed by use of arthrotomy were reviewed. Data retrieved from medical records included signalment, use of horse, affected limb, lameness history, lameness examination findings, radiographic findings, surgical technique, and outcome. Follow-up evaluation was obtained by telephone interview. RESULTS: Most affected horses were < 5 years old and had a history of chronic lameness. Lameness grade ranged from 1/5 to 4/5. Fragments involved 20 to 45% of the dorsopalmar articular surface of the distal phalanx. Eight of 14 horses had a successful outcome. Outcome was not associated with age, duration or severity of lameness, or fragment size. CONCLUSIONS AND CLINICAL RELEVANCE: Despite involvement of a large portion of the articular surface and use of arthrotomy, joint instability and permanent soft tissue injury was not a problem in most horses. Outcome may be improved by selection of horses with lameness of < 2 years' duration and careful management after surgery. A fair prognosis may be anticipated for removal of large fragments of the extensor process via arthrotomy.     

Progression of Femoropatellar Osteochondrosis in Nine Young Horses Clinical, Radiographic and Arthroscopic Findings

The clinical and radiographic progression, and arthroscopic findings for nine young horses (<1 year of age) with femoropatellar osteochondrosis (OCD) are presented. Horses had a 2 to 12 week history of bilateral (8 horses) or unilateral (1 horse) hindlimb lameness. The most consistent clinical signs included femoropatellar joint distention and bilateral hindlimb lameness. At the onset of clinical signs, radiographic lesions were not present (4 horses) or subtle (5 horses), but were easily identified on radiographs taken 4 to 24 weeks later. Arthroscopic surgery was delayed until radiographic changes became obvious. Surgical findings in 20 femoropatellar joints were most commonly osteochondral "flaps" located on the proximal lateral trochlear ridge of the femur and were larger than had been indicated by the radiographs. Eight horses were being used for their intended purpose, which was racing (3 horses were racing and 3 were in race training), dressage (1 horse) or pleasure riding (1 horse). One horse required a second surgery when similar lesions developed in the opposite stifle, and was euthanatized 2 months later because of persistent lameness. Once clinical signs are observed, osteochondrosis lesions of the distal femur can progress in foals younger than 9 months of age and the full extent of the radiographic lesion may take several weeks to develop.     

Primary haemangiosarcoma in the proximal humerus of a Clydesdale gelding

An 11‐year‐old Clydesdale gelding was presented for investigation of left forelimb lameness of 2 weeks' duration. The use of scintigraphic imaging helped to localise the source of lameness to the left proximal humerus. In this report, the clinical and diagnostic imaging features of a primary osseous haemangiosarcoma in a horse are described, along with the challenges of establishing a definitive diagnosis ante mortem. In addition, neoplasia of the appendicular skeleton should be considered a differential cause of lameness in the horse.