Advanced imaging of an incomplete fracture and exostosis of the third metacarpal bone in a young Warmblood horse

A 5-year-old Hanoverian gelding with acute moderate right forelimb lameness underwent nuclear scintigraphy, which identified marked increase in radiopharmaceutical uptake of the proximomedial aspect of the right metacarpus. Ultrasonography and radiography identified sclerosis and exostosis of the proximomedial aspect of the metacarpal bone III in-between the suspensory ligament and the second metacarpal bone, and presence of a suspected fracture. The owner requested euthanasia of the gelding, and post-mortem computed tomography and magnetic resonance imaging identified marked bone sclerosis and thickening of the palmar cortex of the metacarpal III (McIII), presence of an incomplete fracture in the palmar cortex of McIII and expansive exostosis from McIII extending in a palmar direction between the suspensory ligament and the second metacarpal bone. Histopathological examination confirmed the imaging findings of sclerosis and led to final diagnosis of a fracture of the palmar cortex of the McIII associated with an exostosis encroaching the medial aspect of the suspensory ligament. No abnormalities were present in the suspensory ligament or metacarpal bone II (McII).     

Fibro‐osseous tumour of the fourth metacarpal bone in a horse: Clinical,radiographic and long‐term post operative findings

This case study describes a rare case of a fibro‐osseous tumour in the distal part of the fourth metacarpal bone of a 13‐year‐old horse. The tumour was surgically removed and wound healing occurred without complications. A specific diagnosis was reached by considering the clinical and histological features of the mass. However, the process was complicated by the different classification systems for this type of tumour. When classified according to the veterinary literature, ossifying fibroma is the appropriate diagnosis, whereas in human medicine this term has been replaced.     

The effect of training on equine metacarpal bone breaking strength

Right third metacarpal bones (n=24) from Thoroughbreds, 24 to 48 months old and in race training, were tested to failure in 3 point bending. The neutral load axis was estimated and the distance from the axis to the outer dorsal cortical surface measured. Mid-diaphyseal dorsopalmar and lateromedial outer cortical and medullary diameters were measured. Breaking strength, cortical area and area moment of inertia were also calculated. Significant correlations were demonstrated between months in training and dorsopalmar bone diameter, cortical area and area moment of inertia. Significant linear models were illustrated between the same 3 variables and number of months in training. It was concluded that increased duration of training significantly enlarges dorsopalmar bone diameter, cortical area and area moment of inertia. Training did not affect metacarpal bone breaking strength as determined by 3 point bending.     

Fibro‐osseous tumour of the second metacarpal bone in a Thoroughbred filly

A 7‐month‐old Thoroughbred filly was evaluated because of an enlarging mass present on the proximomedial aspect of the left metacarpus. The mass was first noticed at age 2 months and had continued to increase in size. The mass was firm, nonpainful to palpation, covered with normal haired skin and had never been associated with lameness. Radiographs obtained at ages 2 and 7 months revealed an enlarging and partially mineralised mass associated with the second metacarpal bone. Based on the clinical and radiographic progression, as well as the location of the mass, a poor prognosis for future athletic soundness was given and the filly was subjected to euthanasia. The mass had histological features of both an ossifying fibroma and osteoma.     

Computed tomography as a method of estimating bone mineral content in horses

With the advancement of technology, more tools and methods are being made available for the assessment of bone density in the live animal. Computed tomography (CT) is one such tool. In a CT scan, x-rays are passed through a subject and detectors record transmitted energy. The CT computer then constructs cross-sectional images from this data to represent the internal anatomy.The first objective of this study was to investigate CT as a means of estimating bone mineral content of the equine third metacarpal bone. Our hypothesis was that the cross-sectional area of the third metacarpal bone, as measured on CT images, would correlate significantly with ash weight of that section. Our second objective was to use CT to measure and compare bone density in the dorsal, palmar, lateral and medial cortices of the equine third metacarpus. We hypothesized that CT would detect differences in density by cortex.Twelve cadaver thoracic limb specimens, from horses of varying age, breed and prior use, were scanned on a CT 9800 (GE Medical Systems). Scanned sections of the limb were then skinned, dried, ether-extracted and ashed in a muffle furnace. Bone mineral content was expressed as grams of ash/cm section of bone. The image recorded by the CT was developed and assessed using an imaging photodensitometer and a corresponding software package to estimate the area of each bone section. Correlation was determined using SAS (6.12). Differences in bone density by cortex were calculated using a simple t-test. The maximum, minimum and mean estimates of third metacarpal bone cross-sectional area as determined by CT were 519, 351 and 423 mm², respectively, while the maximum, minimum and mean ash weights were 8.9, 4.8 and 6.4 g/cm, respectively. Estimates of bone mineral content by ash and cross-sectional area as determined by CT were significantly correlated (r=.91, P=.0001). There was no difference in CT density numbers between lateral and medial cortices, however the dorsal cortex was lower in density than the lateral (P<.05) and the palmar cortex was lower in density than all other cortices (P<.05). This data suggests that in a research setting, CT is an effective method by which to calculate cross-sectional area and, hence, estimate bone mineral content. Computed tomography was also able to detect differences in bone density by cortex.     

Computed tomography assisted repair of a central tarsal bone slab fracture in a horse

A 13‐year‐old Quarter Horse gelding was presented for repair of a central tarsal bone fracture. Radiographs showed a single large nondisplaced sagittal slab fracture; however, computed tomography (CT) revealed an additional small, displaced central tarsal bone fragment. The complex fracture was repaired, under the same anaesthetic period as the CT examination, using the CT hard copies images, intraoperative fluoroscopy and radiographs. The horse recovered well and after rehabilitation showed no residual lameness at work. Computed tomography was instrumental in achieving precise screw placement and successful fracture repair.     

Standing repair of an articular dorsal medial oblique fracture of the proximal third metacarpal bone in a racing Standardbred

The third metacarpal bone (McIII) is a common site of long bone fractures in racehorses. However, articular fractures of the dorsomedial aspect of McIII are a rare location of such injuries. This report describes the successful standing surgical repair of an articular fracture of the dorso-medial proximal McIII in a 4-year-old Standardbred racing mare using lag screw fixation.     

Treatment of incisive bone fracture in a horse using an acrylic splint

A ventrally displaced incisive bone fracture was diagnosed in a 3-year-old Andalusian stallion. Symptoms included swelling of the lips, dysphagia and ptyalism. External manipulation revealed pain and crepitus in the gingival region of the rostral maxilla. An intraoral examination revealed upper gingival haematomas, misalignment and malocclusion of the incisors (prognathism). A radiograph of the rostral maxilla confirmed ventrally displaced bilateral fractures of the incisive portion of the maxilla rostral to the canine teeth (Triadan 104/204). The fracture was reduced under general anaesthesia. A methylmethacrylate intraoral splint was used to stabilise the fracture. Post operative radiographs confirmed the fracture reduction. Post operative clinical control confirmed the correct position of the splint. No complications were encountered in the post operative period and good stabilisation was obtained. The splint was removed 60 days post operatively. The use of an acrylic intraoral splint successfully stabilised a bilateral, ventrally displaced incisive bone fracture. Normal occlusion was obtained. The use of an acrylic splint may represent a relatively simple, inexpensive and noninvasive technique for the repair of incisive bone fractures rostral to canine teeth in horses.     

A retrospective study comparing conservative and surgical treatments of open comminuted fractures of the fourth metatarsal bone in horses

The proximal third of metatarsal IV is predisposed to open comminuted fractures due to its superficial and prominent position and controversy exists regarding the most appropriate management for this type of fracture. Fifty‐three horses treated for open comminuted fractures of the proximal third of metatarsal IV were selected for study from 6 equine hospitals across England. Comparisons were made between the 21 horses treated conservatively and the 32 horses treated surgically. Horses treated conservatively at referral centres had comparable rates of survival, rates of return to full work and convalescent periods but a significantly lower cost than those treated surgically. The results of this study suggest that aggressive conservative therapy may be indicated in open comminuted fractures of the proximal third of metatarsal IV.     

Surgical treatment of a second metacarpal bone exostosis with associated desmitis of the body of the suspensory ligament in a horse

This report outlines the diagnosis, surgical treatment and successful outcome following treatment of second metacarpal bone exostosis with concurrent suspensory ligament desmitis, and lameness in a horse. Magnetic resonance imaging was useful in determining the extent of pathology within the suspensory ligament and site of proposed surgical resection. MRI was also utilised as a post-operative tool in determining the timescale for satisfactory healing to enable the horse to return to athletic work.     

Septic pyomyositis,multiple pelvic osteomyelitis and thrombosis in a Thoroughbred foal

Multiple septic osteomyelitis, septic thrombi and septic arthritis are recognised as possible complications of sepsis; however, there are few reports of localised pyomyositis in association with septic arterial thrombosis in foals. A 1-month Thoroughbred colt was presented for investigation of acute and progressive left hindlimb lameness. Physical and laboratory examinations were performed. Ultrasonographic, radiographic and computed tomographic examinations revealed the presence of multiple abscesses and areas of osteomyelitis localised to the gluteal muscles, coxal bone and lumbar spine respectively. Considering the poor prognosis, the foal was subjected to euthanasia. Necropsy confirmed the diagnostic imaging findings and revealed the presence of an extensive septic thrombus, affecting the internal iliac artery, and a single pulmonary abscess. Streptococcus equi subsp. zooepidemicus was isolated from all lesions.     

Differences in the morphology of distal border synovial invaginations of the distal sesamoid bone in the horse as evaluated by computed tomography compared with radiography

Reasons for performing study: Distal border synovial invaginations of the distal sesamoid bone are radiographically assessed during the selection process of horses admitted as breeding stallions or in purchase examinations. Nowadays, many moderately or some deeply penetrating proximally enlarged synovial invaginations are considered as moderate or severe radiographic findings. Objective: To measure the difference between and agreement of the morphology of distal border synovial invaginations on radiography vs. computed tomography (CT). It was hypothesised that the morphology of distal border synovial invaginations would be better evaluable on CT compared with radiography. Methods: Computed tomography scans and 3 dorsoproximal–palmarodistal oblique (DPr‐PaDiO) radiographs were obtained on 50 cadaver forefeet from 25 Warmblood horses. Computed tomography was assumed to be the gold standard. The number, shape and depth of penetration of distal border synovial invaginations into the distal sesamoid bone were evaluated with both methods, and the comparison of their measurements was statistically described. Results: A statistically significant mean difference for number of distal synovial invaginations between CT and all 3 DPr‐PaDiO projections was found and was approximately equal to 2, meaning that CT permits visualisation of an average of 2 more invaginations than radiography. In none of the cases did radiography have a higher number observed than CT. A large variation in the difference of measurements for depth of penetration against their mean difference between CT and the 3 radiographic projections was seen. Radiography underestimated the depth of invaginations, and more so when these were deeper. There was no statistically significant mean difference found between the techniques for depth. A moderate to good agreement between measurements on CT and the three DPr‐PaDiO projections for shape was seen, in which the D55°Pr‐PaDiO projection showed the best agreement. A high specificity (90–99%) and low sensitivity (65%) for all projections for shape were found. Conclusions and potential relevance: Radiography differs considerably from CT concerning the morphology of distal navicular border synovial invaginations. For the evaluation of the number, depth and shape of distal synovial invaginations in the distal sesamoid bone, radiography shows only partially the morphology seen on CT.     

Tibial osteomyelitis caused by Rhodococcus equi in a mature horse

A 7‐year‐old Paint mare presented for evaluation of a swollen right hindlimb of approximately 6 weeks' duration. Ultrasonography and radiography suggested a severe osteomyelitis and abscessation of the right tibia. Previous treatment included systemic antimicrobial therapy using procaine penicillin G (22,000 u/kg bwt, q. 12 h, i.m.) and gentamicin sulfate (6.6 mg/kg bwt, q. 24 h, i.v.) initially followed by oral doxycycline (10 mg/kg bwt, q. 12 h, per os) and rifampin (5 mg/kg bwt, q. 12 h, per os). Based on the poor prognosis the mare was subjected to euthanasia. Necropsy results subsequently revealed a severe, chronic, focal, necrotising osteomyelitis with localised cellulitis and abscessation. Rhodococcus equi was isolated from the tibia, subcutaneous abscess and from a pectoral abscess found at necropsy. Immunological testing of blood samples obtained ante mortem revealed normal blood lymphocyte phenotyping, but markedly increased IgG and IgM concentrations, indicating an active humoural response. While there have been reports of Rhodococcus equi infection in mature horses this is an area previously unreported in the literature.     

Subcutaneous abscess caused by Clostridium perfringens and osteomyelitis in a dog

A case of a subcutaneous abscess caused by Clostridium perfringens infection in a five-month-old dog is reported in this study. Clinical examination, radiological findings and cytological analysis of abscess fluid were consistent with Clostridium induced disease. Treatment including drainage of the abscess and antibiotic therapy led to rapid clinical improvement. However, despite aggressive medical therapy and proper wound care, the deep soft tissue infection led to osteomyelitis with premature closure of the growth plates of the tibia and secondary bone shortening. Prolonged treatment with metronidazole and amoxicillin-clavulanic acid resulted in an excellent outcome with normal weight bearing.     

Septic arthritis of the first and second cervical vertebral articulations with vertebral osteomyelitis in a foal caused by Salmonella

A case of infectious arthritis of a cervical vertebral articulation and vertebral osteomyelitis in a foal caused by Salmonella is described. Ultrasound images of the cervical facet joints were suggestive of septic arthritis and ultrasound facilitated needle placement for arthrocentesis and joint lavage. Due to the uncommon location of the infection, diagnosis of septic arthritis was not immediate and, despite aggressive intra‐articular lavage and instillation of appropriate intra‐articular antibiotics after hospitalisation, we were unable to resolve the infection in this foal. Radiographs did not show evidence of osseous involvement until later in the course of the infection. Septic arthritis should be suspected in cases with similar clinical and laboratory findings and radiographic changes may not be present early in the course of infection. Ultrasound imaging provided the most useful diagnostic information regarding infection of the cervical joints, facilitating both diagnosis and treatment.     

Partial mandibular condylectomy and temporal bone resection for chronic,destructive, septic arthritis of the temporomandibular joint in a horse

Sepsis of the temporomandibular joint (TMJ) of the horse is rare. This case report describes the use of radiography, ultrasonography and computed tomography to diagnose sepsis of the TMJ in a 2‐year‐old Thoroughbred filly. The mandibular condyle and temporal bone were partially resected to successfully remove necrotic tissue within and surrounding the TMJ. Sepsis resolved and the horse returned to race training. Follow‐up computed tomography examination showed generation of a mandibular ‘pseudocondyle’ at 8 months post operatively.     

Computed tomographic diagnosis of incomplete palmar cortical (fatigue) fracture of the third metacarpal bone in two young adult endurance horses

Two young adult endurance horses were presented for investigation of sudden-onset forelimb lameness during competition. Clinical examination revealed a severe forelimb lameness and pain on palpation of the proximal palmar metacarpal area. Initial radiographic survey of the affected forelimb was unremarkable in both cases. A week of box rest resulted in only a mild improvement in the lameness. A second radiographic examination did not reveal any significant abnormalities. In both cases, scintigraphic examination was suggested, but was declined by the owner, and the lameness had significantly improved after local infiltration of 3 mL of anaesthetic solution in the proximal suspensory region. Radiographic and ultrasonographic examinations of the carpus and proximal suspensory region were unremarkable in Case 2. Case 1 had increased thickness of the medial lobe of the proximal aspect of the suspensory ligament. A computed tomographic examination was performed and an incomplete longitudinal (fatigue) fracture of the proximal third metacarpal bone was detected. After 8 months of box rest and rehabilitation, re-examination revealed resolution of the lameness in both cases. Advanced diagnostic imaging should be considered in young endurance horses with severe lameness during competition or training, in which radiographic and ultrasonographic examinations are unremarkable or do not explain the severity of the lameness. Computed tomography imaging is considered a useful diagnostic imaging technique to detect incomplete longitudinal palmar metacarpal cortical (fatigue) fractures due to its ability to provide excellent bone detail.     

Navicular bone osteomyelitis and navicular bursitis with associated fistula diagnosed with magnetic resonance fistulography in the horse

A 7‐year‐old Quarter Horse gelding was referred for magnetic resonance (MR) imaging due to chronic left hindlimb lameness localised to the foot. On presentation, a previously undiagnosed draining tract was identified at the plantar aspect of the pastern. Radiographs revealed severe osteolysis of the navicular bone. Positive contrast MR fistulography was performed using a gadolinium based contrast agent following conventional MR imaging of the left hind foot. Fistulography allowed characterisation of a fistulous tract, which was closely associated with the deep digital flexor tendon, navicular bursa and osteomyelitis of the navicular bone.