Use of a flexed dorsoplantar radiographic view of the talocrural joint to evaluate lameness in two dogs.

A flexed dorsoplantar radiographic view of the talocrural joint was a useful additional view to diagnose abnormalities of the lateral trochlear ridge of the talus of 2 dogs. This view outlined the subchondral bone of both trochlear ridges of the talus and the apposing cochlea tibiae of the distal portion of the tibia. The tarsus was flexed at the level of the talocrural joint, and an x-ray beam was centered on the joint. With this additional view, fractures of the lateral trochlear ridge were readily diagnosed. This view would help to demonstrate osteochondral lesions of the lateral trochlear ridge.     

ULTRASONOGRAPHIC EVALUATION OF TARSOCRURAL JOINT CARTILAGE IN NORMAL ADULT HORSES

Ultrasonographic examination of the tarsus was performed on four clinically and radiographically normal limbs of adult horses. Particular attention was paid to the articular cartilage surfaces of the trochlear ridges of the talus and the distal intermediate ridge of the tibia. Two separate measurements of articular cartilage thickness were acquired from a longitudinal view at each site. Anatomy was confirmed with post mortem dissection. Ultrasonography was found to be a practical method for imaging the articular cartilage over the trochlear ridges of the talus and distal intermediate ridge of the tibia. The cartilage appeared as a hypoechoic band overlying the hyperechoic subchondral bone. The mean cartilage thickness over the lateral and medial trochlear ridges of the talus and the distal intermediate ridge of the tibia were 0.57 mm, 0.58 mm and 0.7 mm respectively. These measurements may have value for comparison to thickened cartilage and lesions of osteochondrosis and abnormally thinned cartilage of osteoarthritis. Ultrasound examination was not helpful in evaluating the proximal and distal intertarsal and tarsometatarsal joints, the close proximity of the articular surfaces obscured visualization of the articular cartilage.     

Radiographic anatomy of the tarsocrural joint of the dog

The normal radiographic anatomy of the proximal hock joint of the dog is discussed. The choice of projection depended on the site to be examined. Examination of the lateral trochlear ridge of the talus required a number of projections including the fully extended and fully flexed mediolateral, plantaromedial-dorsolateral oblique and a flexed dorsoplantar using a horizontal beam. The best radiographic projection for examination of the medial side of the joint was the plantarodorsal projection while the mediolateral projection showed the dorsal and plantar edges and gave some general information of changes around the joint.     

SCINTIGRAPHIC EVALUATION OF THE DISTAL TARSAL REGION IN HORSES WITH DISTAL TARSAL PAIN

Distal tarsal pain is a common reason for hind limb lameness, but diagnosis cannot always be made on radiographic examination. Scintigraphy may allow detection of subtle changes undetected by other diagnostic methods. We hypothesized that (1) distal tarsal pain would be associated with a loss of the expected pattern of radiopharmaceutical uptake (RU) detected in normal horses, (2) distal tarsal RU would be greater in limbs with tarsal pain than without pain, (3) RU in painful tarsi with radiographic evidence of osteoarthritis (OA) would be greater than in distal tarsal pain with no radiographic evidence of OA. The study aimed to describe radiopharmaceutical distribution in the distal tarsal region of horses with distal tarsal pain, and to compare this with the contralateral limb and results from horses without tarsal pain. Retrospective evaluation of scintigraphic images of the distal tarsal region was performed for 52 horses with distal tarsal pain: 15 with no radiographic evidence of OA (Group 1) and 37 with radiographic evidence (Group 2). The images were assessed using vertical and horizontal profile analysis across the distal tarsal region and regions of interest comparisons between the distal tarsal region and tibia within each horse (RU ratio). Painful limbs in unilaterally lame horses from Groups 1 and 2 had a significantly greater RU ratio than the respective contralateral limbs, and were significantly greater than the RU ratio in normal horses. On plantar images, mean region of interest counts were greater in the lame than the contralateral limb in Group 2 but not in Group 1. Although there was a positive correlation between lame and contralateral limb RU ratio in group 1, this was lost in group 2 horses. In lame limbs, the normal vertical activity profile was lost in 85% of group 1 and all of group 2, and the normal horizontal activity profile was lost in all of group 1 and 96% of group 2. There was a significant effect of lameness, but not of group on sites of peak activity on all profiles. The results of this study indicate that distal tarsal pain is associated with loss of the expected pattern of RU detected in normal horses. The findings also suggest that distal tarsal RU in lame limbs is greater than in limbs without pain, and that painful limbs with radiographic evidence of OA have a greater RU than painful limbs without radiographic evidence of OA.     

Arthroscopic Approach and Intra-Articular Anatomy of the Plantar Pouch of the Equine Tarsocrural Joint

Arthroscopic examination of structures within the plantar pouch of the tarsocrural joint was accomplished via portals in both the plantaromedial and plantarolateral aspects of the joint. Flexion and extension of the tarsus while examining the joint through either portal allowed observation of the proximal and plantar aspects of the lateral and medial trochlear ridges, the trochlear groove, the caudal aspect of the distal tibia, and the deep digital flexor tendon (DDFT) in its sheath. From a plantarolateral portal, the plantar talocalcaneal ligament and the plantar aspect of the lateral malleolus could be observed. The caudal aspect of the medial malleolus could not be observed with flexion or extension of the joint from a plantaromedial portal, but in some horses, the caudal aspect of the lateral malleolus could be observed. The dorsolateral and dorsomedial aspects of the plantar pouch were best examined from a portal on the ipsilateral side of the joint. An instrument portal opposite either arthroscope portal allowed access to most regions of the joint except the abaxial surface of the trochlear ridge opposite the instrument.     

Arthroscopic removal and curettage of osteochondrosis lesions on the lateral and medial trochlear ridges of the talus in two dogs

Osteochondrosis lesions in the tibiotarsal joint were treated arthroscopically in two dogs. One dog had unilateral osteochondrosis of the dorsal aspect of the lateral trochlear ridge of the talus. The second dog had bilateral osteochondrosis of the plantar aspect of the medial trochlear ridge of the talus. Removal of all osteochondral fragments (i.e., joint mice) and debridement and curettage of the remaining talar defects were accomplished arthroscopically. Both dogs had excellent short-term outcomes.     

Computed tomography assisted diagnosis and treatment of a comminuted fracture of the plantar aspect of the medial trochlear ridge and the proximal tubercle of the talus in a foal

Isolated fractures of the proximal tubercle of the talus and the medial trochlear ridge of the talus have been reported in the equine literature. A comminuted, intra-articular fracture of the plantar medial trochlear ridge and proximal tubercle of the talus has not been previously reported. The current case report describes this unique comminuted fracture in a 6-week-old Thoroughbred foal with acute onset lameness. The diagnosis was achieved by a combination of radiography, ultrasonography and computed tomography (CT) followed by CT arthrography. Surgical removal of the fracture fragments was recommended; the intra-articular fracture fragments were removed under arthroscopic visualisation of the plantar pouch of the tarsocrural joint; due to ligamentous attachments and partial extra-articular nature, the fracture fragment of the proximal tubercle of the talus was removed via an arthrotomy extension of the medial arthroscopy portal. On follow-up examination 12 months post-operatively, the yearling showed no clinical evidence of lameness or radiographic evidence of secondary degenerative joint disease.     

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.     

Normal Radiographic and Ultrasonographic Appearance of the Adult Dromedary Camel Tarsus (One Humped Camel)

Six cadaver pelvic limbs were obtained from clinically sound dromedary camels and examined radiographically and ultrasonographically using a 7.5 MHz convex transducer. Radiographic examination was performed in dorsoplantar, lateromedial, dorsolateral‐plantaromedial oblique and plantarolateral‐dorsomedial oblique projections, and the bony structures and articulations of the tarsal joint were outlined. The tarsus was ultrasonographically investigated in four planes (dorsal, medial, lateral and plantar), and each plane was scrutinized in four levels (calcaneal tuber, tibial malleoli, base of calcaneus and proximal end of metatarsus) in both transverse and longitudinal views. Limbs were examined grossly, frozen at ?20°C and sectioned. Radiographic and ultrasonographic findings correlated well with the gross anatomy and frozen sections. The normal appearance of bony and soft structures of the tarsus described in this study provided basic reference data for ultrasonographic and radiographic investigations of tarsal disorders in the dromedary camel.     

Radiographic, computed tomographic and arthroscopic findings in 23 dogs with osteochondrosis of the tarsocrural joint

Twenty-three dogs with osteochondrosis of the tarsocrural joint were evaluated by radiography, computed tomography (CT) and arthroscopy. The radiographic examination included an extended and flexed mediolateral, a plantarodorsal, a flexed dorsoplantar skyline view, and a plantaromedial-dorsolateral and a plantarolateral-dorsomedial view (two oblique views). The CT examination was carried out in ventral recumbency and 1 mm slices were taken with a bone window setting; 31 lesions were identified in the 46 joints examined. The arthroscopic exploration used either a plantar or a dorsal puncture, depending on the site of the lesion. In six cases the lateral, and in 17 cases the medial trochlear ridge was involved. Although the survey radiographs were sufficient to make a diagnosis, the CT examination helped to determine the exact site, and the number and size of the fragments of bone. A four-stage classification system comparable to the one used in man was established. Arthroscopy provided information about synovial inflammation and damage to the joint cartilage, and made it possible to remove fragments of bone from one-third of the cases.     

Changes on radiographs at Thoroughbred yearling sales: Prevalence and significance

Examination of Thoroughbred yearlings at public auction is a special form of prepurchase examination since the clinician cannot be as thorough as in clinical situations. Yearlings are purchased based on visual and limited physical examinations and evaluation of presale radiographs and upper respiratory tract endoscopic examination. The prevalence and clinical relevance of radiographic changes has been the subject of our recent publications and a summary of our results is presented here. Radiographic changes were most common in the fetlock joints and 1127 forelimb and 1102 hindlimb fetlock radiographic series were examined. Flattened areas of the distal palmar aspect of the distal articular surface of the third metacarpal bone (McIII) were found in 41% of yearlings and had neither an effect on performance nor caused the subsequent development of clinical problems. Flattening (10%) or radiolucency (17%) of the dorsal aspect of the distal sagittal ridge of McIII was common and had no effect of these 2 parameters. Thirty of 1130 yearlings that had complete carpal radiographic examinations had signs of dorsal medial middle carpal disease. The presence of dorsal medial middle carpal joint lesions affected the horse’s ability to start a race and increased the incidence of clinical problems. The most common finding on carpal radiographs was circular radiolucencies in the ulnar carpal bone but the presence of this finding neither affected the ability to start nor was associated with clinical problems. Forty-eight of 1101 yearlings with complete tarsal radiographic examinations had concavity or fragmentation of the cranial intermediate ridge of the distal tibia, but there was no effect on racing performance. The changes most commonly observed in the distal tarsal joints were the presence of osteophytes or enthesophytes involving the distal intertarsal or tarsometatarsal joints. The presence of osteophytes or enthesophytes involving the distal intertarsal or tarsometatarsal joints were the only changes significantly associated with starting a race, but the effect was small. There were 600 yearlings with stifle radiographs, but in only 170 of them could the medial femoral condyle and proximal tibia be evaluated. Thirty-four yearlings had defects with or without fragments on the lateral trochlear ridge of the femur and there were no significant associations with any outcome except that they were more likely to have surgical treatment.     

On the occurrence of blood vessels in the superficial layers of articular cartilage in bovine fetuses

The occurrence of vascular networks in the superficial layers of articular cartilage of 51 bovine fetuses (10-93 cm CRL) and 3 calves was studied grossly and histologically. The networks were found regularly on the incisura trochlearis of the ulna, on the trochlea of the radius and talus, on the plantar articular surface of the head of the talus, on the proximal articular surface of the fused central and 4th tarsal bones, and less regularly on the articular surfaces of the distal phalanx and distal sesamoid (navicular) bone and on the cochlea of the tibia. The vessels coursed in the superficial stratum of the articular cartilage and were encountered in those places where synovial fossae or villi are found later. The vessels were not present in the calves.     

IMAGING DIAGNOSIS—RADIOGRAPHIC,ULTRASONOGRAPHIC, COMPUTED TOMOGRAPHIC,AND FLUOROSCOPIC APPEARANCE OF A DISTAL PELVIC LIMB ARTERIOVENOUS MALFORMATION IN A YOUNG GERMAN SHEPHERD DOG

A German shepherd puppy presented for evaluation of a suspected arteriovenous fistula on the distal aspect of the right pelvic limb. Radiographs demonstrated expansion and resorption of the tarsal and metatarsal bones, and ultrasound detected a vascular abnormality. Using computed tomographic angiography, a complex arteriovenous malformation (AVM) involving the distal tibia, tarsus, and the metatarsus and an osteochondritis dissecans (OCD) lesion of the talus were identified. Based on these findings, therapeutic limb amputation was performed. Fluoroscopic angiography, vascular casting, and dissection were then used to further characterize features of this previously unreported AVM with concurrent bony lesions and OCD.     

The hindlimb in walking horses: 2. Net joint moments and joint powers

The objective of the study was to describe net joint moments and joint powers in the equine hindlimb during walking. The subjects were 5 sound horses. Kinematic and force data were collected synchronously and combined with morphometric information to determine net joint moments at each hindlimb joint throughout stance and swing. The results showed that the net joint moment was on the caudal/plantar side of all hindlimb joints at the start of stance when the limb was being actively retracted. It moved to the cranial/dorsal side around 24% stride at the hip and stifle and in terminal stance at the more distal joints. It remained on the cranial/dorsal side of all joints during the first half of swing to provide active limb protraction, then moved to the caudal/plantar aspect to reverse the direction of limb motion prior to ground contact. The hip joint was the main source of energy generation throughout the stride. It was assisted by the tarsal joint in both stance and swing phases and by the fetlock joint during the stance phase. The coffin joint acted as an energy damper during stance, whereas the stifle joint absorbed almost equal amounts of energy in the stance and swing phases. The coffin and fetlock joints absorbed energy as the limb was protracted and retracted during the swing phase, suggesting that their movements were driven by inertial forces. Future studies will apply these findings to detect changes in the energy profiles due to specific soft tissue injuries.     

SCINTIGRAPHIC ASSESSMENT OF THE METACARPOPHALANGEAL AND METATARSOPHALANGEAL JOINTS OF HORSES WITH JOINT PAIN

Our aims were to evaluate the pattern of radiopharmaceutical uptake in horses with lameness related to the metacarpophalangeal and/or metatarsophalangeal joint and compare the results with similar information from sound horses. It was hypothesized that there would be a difference in radiopharmaceutical uptake between the lame and contralateral limb in unilaterally lame horses and that there would be a difference between lame and sound horses. Nuclear scintigraphic images of 43 horses with forelimb lameness and 30 horses with hindlimb lameness were evaluated. In all horses lameness was improved by intraarticular analgesia of the joint, or by perineural analgesia of the palmar/plantar (at the junction of the proximal 3/4 and the distal 1/4 of the metacarpal/metatarsal regions) and palmar/plantar metacarpal/metatarsal nerves. All images were assessed subjectively and a quantitative image analysis was performed by drawing a vertical line profile through the center of each joint in the lateral images and using region of interest analysis in both lateral and dorsal/plantar images. Ratios of radiopharmaceutical uptake were compared for each region between lame and contralateral limbs in unilaterally lame horses and between lame and control horses. There was a significant difference in the ratio of radiopharmaceutical uptake in the proximal aspect of the proximal phalanx between lame and nonlame forelimbs in unilaterally lame horses and in both lame and contralateral limbs of lame horses compared with control horses for the regions of the distal aspect of the third metacarpal/metatarsal bone and the proximal sesamoid bones. However, the profile analysis was of limited clinical value.     

The effect of the tarsal joint positions on the tibial nerve motor action potential latency in dog: electrophysiological and anatomical studies

This study has been carried out to determine the effect of neutral position, hyperextension and hyperflexion of the tarsal joint on the tibial nerve, motor action potential latency and tarsal canal compartment pressure in dogs with the aid of electrophysiological and anatomical methods. Totally twenty healthy mongrel dogs were used. Latency of motor nerve action potential (MNAPL) studies of tibial nerve via surface stimulating and needle recording electrodes was performed on right hind limbs of all the dogs. The compartment pressures of the tarsal canal with the pressure transducer were determined from both limbs from ten of the dogs. In one dog, tarsal regions of both left and right limbs were demonstrated using magnetic resonance imaging (MRI). Two dogs were euthanatized and tarsal regions of the dogs were sectioned for correlative anatomy. Nerve conduction studies showed that the MNAP latency of the tibial nerve were 3.55 +/- 0.097 ms, 3.76 +/- 0.087 ms and 3.39 +/- 0.097 ms in neutral, hyperextension and hyperflexion positions, respectively. Hyperflexion of the tarsal joint caused prolongation of the MNAP latency of the tibial nerve with the highest pressure value being determined in tarsal canal. From the anatomical viewpoint, the distance between the flexor hallucis longus muscle and the superficial digital muscle was the shortest during hyperflexion and the plantar branch of saphenous artery, lateral and medial plantar nerves located more laterally in cadaver and MR imaging sections. As a result of this study, it is thought that tarsal region diseases as well as long time splint in the hyperflexion position as applied in the Ehmer sling can affect the compartment pressure and nerve tension because of occupying in the tarsal canal. Raising pressure and nerve stretching in the tarsal canal compartment could cause deficiencies in the conduction velocity of the tibial nerve. This might be a result of tarsal tunnel syndrome in the dog. Clinicians could consider this syndrome in cases of tarsal region diseases as well as application of long time splint in hyperflexion of tarsal joints in dogs.     

A RADIOGRAPHIC STUDY OF THE DISTAL INTERPHALANGEAL JOINT AND NAVICULAR BURSA OF THE HORSE

Radiographic contrast studies were used in 50 forelimbs from 13 live horses and 12 fresh adult cadavers to determine the frequency of communication between the navicular bursa and the distal interphalangeal joint. Injections of contrast medium were made into the dorsal aspect of the distal interphalangeal joint of one limb and into the navicular bursa of the other forelimb of each horse. In 25 limbs in which contrast medium was injected into the distal interphalangeal joint, no communication was demonstrated between the joint and the navicular bursa. In 20 of the 25 limbs in which injection was made into the navicular bursa, no communication between joint and bursa was seen. In five horses, contrast medium was visible in both the distal interphalangeal joint and the navicular bursa. However, in four of five horses the communication was clearly iatrogenic. In both limbs of one horse, contrast medium was seen to enter the digital flexor tendon sheath after injection into the navicular bursa.
There is probably no naturally occurring communication between the navicular bursa and distal interphalangeal joint in the horse.