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.     

SCINTIGRAPHIC EVALUATION OF THE PROXIMAL METACARPAL AND METATARSAL REGIONS OF HORSES WITH PROXIMAL SUSPENSORY DESMITIS

The aim of the study was to characterize radiopharmaceutical uptake patterns in horses with clinical and ultrasonographic evidence of proximal suspensory desmitis. It was hypothesized that radiopharmaceutical uptake in the proximal palmar (plantar) aspect of the third metacarpal (metatarsal) bone would be greater in lame limbs of horses with proximal suspensory desmitis than in sound limbs and that there would be a positive correlation between the severity of ultrasonographic abnormalities and the degree of radiopharmaceutical uptake. Nuclear scintigraphic evaluation of the proximal metacarpal or metatarsal regions of 126 horses with ultrasonographic evidence of proximal suspensory desmitis was performed. In all horses lameness was substantially improved by perineural analgesia of the palmar metacarpal (subcarpal) or plantar metatarsal (subtarsal) nerves. Scintigraphic images were assessed subjectively, by profile analysis and using region of interest analysis. Associations between the degree of ultrasonographic abnormality and radiopharmaceutical uptake ratios and the presence of radiographic abnormalities and radiopharmaceutical uptake ratios were analyzed. Subjectively, the majority of horses had normal radiopharmaceutical uptake. Profile analysis provided little additional information. However with region of interest analysis there was greater radiopharmaceutical uptake ratios in plantar images in the proximal metatarsal regions of lame limbs compared with nonlame limbs. There was no association between radiological abnormalities and radiopharmaceutical uptake ratios. In forelimbs there was no association between ultrasonographic lesion grade and radiopharmaceutical uptake ratios, however in hindlimbs there was a significant relationship between ultrasonographic grade and radiopharmaceutical uptake ratios.     

SCINTIGRAPHIC EVALUATION OF THE PROXIMAL METACARPAL AND METATARSAL REGIONS IN CLINICALLY SOUND HORSES

In recent years, pain arising from the proximal metacarpal and metatarsal regions has become well recognized as a cause of lameness and various disease entities have been identified. However, our knowledge of normal patterns of radiopharmaceutical uptake is limited, making interpretation of images problematic. It is therefore important to characterize normal patterns of radiopharmaceutical uptake at specific sites to ensure valid interpretation of images in clinical cases with subtle lesions. The purpose of this study was to describe the pattern of radiopharmaceutical uptake in the proximal metacarpal and proximal metatarsal regions in clinically sound horses. Scintigraphic images from 64 clinically normal horses were evaluated. All the images were assessed subjectively. The lateral, dorsal, and plantar scintigraphic images were assessed qualitatively using horizontal line profiles through the proximal metacarpal and proximal metatarsal regions. Mean ratios of radiopharmaceutical uptake were calculated from three regions of interest sited over the proximal metacarpal and proximal metatarsal regions and a reference site. In 78% of forelimbs the peak of radiopharmaceutical activity was at the dorsal to central portion of the proximal metacarpal region. Seventy-five per cent of the dorsal plane profiles of activity were symmetrical, with the highest peak over the medial to central portion of the proximal metacarpal region. In 80% of hindlimb lateral images the peak radiopharmaceutical activity was at the central to plantar aspect of the proximal metatarsal region. All (100%) plantar image profiles of activity were symmetrical, with the highest peak being over the lateral portion of the proximal metatarsal region. There was no significant left and right variation between sites for mean ratios on the lateral and dorsal images of the proximal metacarpal region. However, using lateral images the mean ratios from all regions of the right proximal metatarsal were greater than left (dorsal P = 0.003, plantar P < 0.0001 and whole proximal metatarsal, P = 0.0006). There was no significant variation in mean ratios between left and right on plantar images. However, the mean ratio for the lateral proximal metatarsal region was significantly greater than for the medial proximal metatarsal regions (P < 0.0001). There was no significant effect of age. Left/right symmetry of radiopharmaceutical uptake was shown in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions. There was higher radiopharmaceutical uptake in the right proximal metatarsal region than the left, which agrees with previous studies of the tarsal and metatarsophalangeal joints. There were differences in the pattern of radiopharmaceutical uptake between the forelimbs and hindlimbs. In the forelimbs maximum radiopharmaceutical uptake was located at the dorsal to central portion of the proximal metacarpal region in the lateral image, with peak activity over the medial to central portion of the proximal metacarpal region on dorsal images. In the hindlimbs the maximum radiopharmaceutical uptake was at the central to plantar aspect of the proximal metatarsal region in the lateral image, with peak activity over the lateral portion of proximal metatarsal region on plantar images. The results of this study support the hypothesis that there would be a standard pattern of radiopharmaceutical uptake across the proximal metacarpal and l metatarsal regions, but the pattern of uptake observed would be different in the proximal metacarpal region compared with the proximal metatarsal region. There was left/right symmetry of radiopharmaceutical uptake in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions, with higher radiopharmaceutical uptake in the right. There was no variation of radiopharmaceutical uptake pattern with age.     

Quantitative analysis of scintigraphic findings in tibial stress fractures in Thoroughbred racehorses

OBJECTIVE: To develop a quantitative method of interpreting tibial scintigrams of Thoroughbred racehorses with tibial stress fractures that may facilitate diagnosis of fractures and to provide prognostic information regarding future performance of affected horses. ANIMALS: 35 Thoroughbred racehorses. PROCEDURES: Static bone-phase scintigrams of tibial stress fractures were quantitatively analyzed by use of ratios of the mean radionuclide counts per pixel in a region of interest (ROI) drawn around the area of increased uptake of radiopharmaceutical to mean counts per pixel in a second ROI drawn around an apparently normal area of the tibial diaphysis. In horses with unilateral fractures, ratios for the contralateral tibia were determined by use of 2 ROIs drawn at the same positions as the ROIs in the fractured tibia. Ratios were compared between fractured versus apparently normal tibias, between horses that returned to racing versus those that did not, and among horses with various grades of lameness. The association between ratios for fractured tibias and intervals between diagnosis and return to racing was also assessed. RESULTS: Mean ratio of ROIs in apparently normal tibias was 1.35 (95% confidence interval [CI], 1.21 to 1.50); that in tibias with stress fractures was 3.55 (95% CI, 2.50 to 4.60). These ratios were significantly different. None of the associations between ratios for fractured tibias and grades of lameness or performance outcomes were significant. CONCLUSIONS AND CLINICAL RELEVANCE: Tibial stress fracture scintigrams can be quantitatively analyzed. A prospective study with a controlled rehabilitation period is necessary to evaluate the possible applications of this method.     

SCINTIGRAPHIC AND RADIOGRAPHIC APPEARANCE OF THE SACROILIAC REGION IN HORSES WITH GAIT ABNORMALITIES OR POOR PERFORMANCE

Nuclear bone scintigraphy is commonly used in the diagnosis of sacroiliac disease in horses. The aim of the present retrospective study was to determine if there was an association between radiopharmaceutical uptake pattern and radiographic appearance of the sacroiliac region in horses. Seventy-nine horses undergoing bone scintigraphy with Tc-99 m-HDP and radiography of the pelvis because of lameness or poor performance were studied. Subjective and semiquantitative methods were used to characterize and compare radiopharmaceutical uptake between horses. Ventrodorsal radiographs of the region were obtained and were evaluated. Subjectively, 70 horses (88.6%) had an abnormal uptake pattern. In nine horses, the sacroiliac region was normal (11.4%). There was no association between subjective evaluation of the scintigraphic images and semiquantitative methods. There was a significant association between radiopharmaceutical uptake and conformation (T- or Y-like form) and shape (butterfly-, wing-, leaf-, or horn-like) of the sacrum. The radiopharmaceutical uptake of the tubera sacralia was significantly higher in males (left side P =0.002, right side P =0.003). In conclusion, the conformation of the sacrum may play an important role in the scintigraphic appearance and may be the cause of increased radiopharmaceutical uptake.     

Results of bone scintigraphy in racing standardbred horses: 64 cases (1992-1994).

OBJECTIVE: To document anatomic patterns of scintigraphic uptake and related orthopedic disease associated with racing activity in Standardbred horses. DESIGN: Retrospective study. ANIMALS: 64 Standardbred horses evaluated for lameness. PROCEDURE: Medical records at the time of discharge were reviewed, and information regarding signalment; history; results of lameness examination, scintigraphy, and radiography; diagnosis; and treatment were obtained. RESULTS: 274 areas of increased radiopharmaceutical uptake were identified. Scintigrams of 218 limbs (106 forelimbs, 112 hind limbs) were available for review. Seventy-three (33%) scintigrams had increased radiopharmaceutical uptake associated with the proximal sesamoids, 46 of 106 (43%) fore-limb scintigrams had increased uptake associated with the third carpal bone, and 33 of 112 (33%) hind limb scintigrams had radiopharmaceutical uptake associated with the small tarsal bones. Forty-three of 218 (20%) scintigrams had increased uptake associated with the distal aspect of the third metacarpal and metatarsal bones. Abnormal scintigraphic uptake was bilateral in 91 of 139 (65%) forelimb locations and 99 of 134 (74%) hind limb locations with increased radiopharmaceutical uptake. The primary scintigraphically identified classifications of disease were exercise-induced bone remodeling, synovitis or arthritis, and soft-tissue avulsion from bone (66, 17, and 6% of areas with increased radiopharmaceutical uptake, respectively). Of 274 areas with increased radiopharmaceutical uptake, 244 (89%) were believed to be clinically important. CONCLUSIONS AND CLINICAL RELEVANCE: Distinctive patterns of increased radiopharmaceutical uptake were identified that suggested Standardbred horses used for racing may have a predilection to develop orthopedic disease at specific sites that are distinct from those in Thoroughbreds used for racing and horses used for jumping activities.     

STRESS REMODELING AND STRESS FRACTURE OF THE HUMERUS IN FOUR STANDARDBRED RACEHORSES

Two 2-year-old pacers, a 3-year-old pacer and a 2-year-old-trotter with acute forelimb lameness were admitted for nuclear scintigraphic examination. Horses were grade 3-4/5 lame. There was increased radiopharmaceutical uptake (IRU) in the distal cranial medial aspect of the humerus in one horse and along the caudal humeral cortex in the other three horses. Two of the four horses were affected bilaterally. Radiographic abnormalities consisted of thickening of the caudal cortex of the mid-diaphysis of the humerus but radiographic changes were not present in all horses. All horses were managed with stall rest initially then stall rest with hand-walking followed by limited turn out for a total of four months. None of the horses had raced before injury. One horse has returned to race training and the other three horses have returned to racing. Average time to return to racing was 329 days. Humeral stress fractures in Standardbred horses are rare. Diffuse patterns of IRU have not been reported in the humerus and are likely indicative of severe stress remodeling. Standardbred racehorses with stress fractures or stress remodeling of the humerus appear to have a good prognosis for return to racing.     

FOCAL INCREASED RADIOPHARMACEUTICAL UPTAKE IN THE DORSOPROXIMAL DIAPHYSEAL REGION OF THE EQUINE PROXIMAL PHALANX

The aims of this study were to establish the frequency of occurrence, intensity and symmetry of focal increased radiopharmaceutical uptake in the dorsoproximal aspect of the diaphysis of the proximal phalanx; to determine if this focal increased radiopharmaceutical uptake was related to age, height, gender, breed, bodyweight, or discipline of the horse, and if there was any relationship with lameness. Scintigraphic images from 690 horses were analyzed subjectively and objectively. Age, breed, discipline, height, weight, gender, and lame limb(s) or reasons for presentation were recorded for all horses. Univariate and multivariable logistic regression was performed to identify associations between available variables and focal increased radiopharmaceutical uptake. Focal increased radiopharmaceutical uptake was present in 17% of forelimbs and 7% of hindlimbs. It occurred most frequently in the forelimbs of older, taller, and heavier warmblood and warmblood cross dressage horses, and the hindlimbs of older, taller, and heavier showjumpers and dressage horses. It was usually bilaterally symmetrical and was not associated with lameness.     

Nuclear Scintigraphic Evaluation of the Distal Tarsal Region in Normal Horses

Bone-phase scintigraphy is sensitive to the dynamic process of bone modeling and remodeling, which may be adaptive or pathologic. Our knowledge of normal patterns of radiopharmaceutical uptake (RU) is limited, making interpretation of images problematic. It is therefore important to characterize normal patterns of RU at specific sites and relate these to age and exercise, to ensure valid interpretation of images in clinical cases with subtle lesions. This study aimed to characterize patterns of uptake of radiopharmaceutical in the distal tarsal region in clinically normal horses, and to investigate the effects of age and work discipline. Retrospective evaluation of nuclear scintigraphic images of the distal tarsal region of 30 clinically sound, high-level showjumpers and lower-level riding horses was performed. All images were acquired dynamically as a series of 35 two-second frames, which were then motion corrected and summated. 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. There was a repeatable pattern of RU across the distal tarsal region in both horizontal and vertical directions. There was significantly greater RU on the dorsal compared with plantar aspect, and lateral compared with medial aspect of the distal tarsal region. RU in the right distal tarsal region was significantly greater than in the left. Elite showjumpers had significantly higher RU ratio compared with the lower-level riding horses, but no significant alterations in the pattern of RU were detected.     

CLINICAL AND DIAGNOSTIC IMAGING FINDINGS IN HORSES WITH SUBCHONDRAL BONE TRAUMA OF THE SAGITTAL GROOVE OF THE PROXIMAL PHALANX

Eight sports horses with unilateral (4) or bilateral (3) forelimb or unilateral hindlimb (1) lameness had subtle radiologic abnormalities of the subchondral bone of the sagittal groove of the proximal phalanx associated with moderate or intense increased radiopharmaceutical uptake. High‐field or low‐field magnetic resonance (MR) imaging confirmed the presence of a fissure fracture or subchondral and trabecular bone trauma. Seven of eight lesions were located approximately midway between the dorsal and palmar cortices of the proximal phalanx; the eighth was sited more dorsally. Two horses underwent follow‐up MR imaging and abnormal signal intensity persisted, with little change.     

Scintigraphic appearance of stress-induced trauma of the dorsal cortex of the third metacarpal bone in racing Thoroughbred horses: 121 cases (1978-1986)

Review of 121 bone scintigrams obtained on racing Thoroughbred horses with clinical histories indicative of forelimb lameness revealed 3 scintigraphic patterns of stress-induced trauma to the dorsal cortex of the third metacarpal bone: (1) focal, intense uptake associated with recent stress fracture; (2) regional uptake of varying intensity or a mixed pattern of uptake associated with chronic stress fracture; and (3) diffuse, mild to moderate uptake associated with periostitis (bucked shins). The latter scintigraphic pattern appeared to be an exaggerated manifestation of the normal remodeling process evident in immature horses (2 to 3 years old). Scintigraphy was most helpful in identifying radiographically occult stress fractures, determining the extent of cortical involvement before surgical intervention in cases of chronic stress fractures, and monitoring the fracture healing process.     

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.     

Scintigraphic evaluation of metacarpophalangeal and metatarsophalangeal joints in clinically sound horses.

The purpose of this study was to describe the pattern of radiopharmaceutical uptake in the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) (fetlock) joints in clinically sound horses. Scintigraphic images from 29 clinically normal horses were evaluated. All the images were assessed subjectively. The lateral views were assessed quantitatively using vertical line profiles through the center of the joint, and mean ratios of radiopharmaceutical uptake were calculated from regions of interest around the third metacarpal or metatarsal bones, and the proximal phalanx and proximal sesamoid bones. From the vertical line profiles, in the majority of forelimbs (65%) the peak activity of radiopharmaceutical distribution was at the proximal region of the proximal phalanx, with a significantly lower activity within the condyles of the third metacarpal bone. However, in 84% of hindlimbs there was a broader profile peak incorporating the condyles of the third metatarsal bone and the proximal aspect of the proximal phalanx, indicating a more generalized even uptake of radiopharmaceutical across the MTP joint. When the regions of interest were compared between front and hindlimbs, there was no significant difference between proximal phalanx and proximal sesamoid bones, but the distal condyles of the third metacarpal bone of the forelimb had significantly lower radiopharmaceutical activity than hindlimbs (P < 0.04). In lateral images, the mean forelimb ratios tended to be higher in the left MCP joint compared with the right (P = 0.069). In hindlimbs, the mean ratios tended to be higher in the right MTP joint than the left (P = 0.052). There was no significant effect of age.     

STRESS FRACTURE OF THE SCAPULA IN TWO HORSES

Stress fracture of the scapula in two horses is described. Both horses had a history of acute lameness after strenuous exercise. Using elective nuclear scintigraphy focal increased radiopharmaceutical uptake in the affected scapula consistent with a fracture was identified. Standing radiography was nondiagnostic in both horses. Ultrasonographic findings in one horse were consistent with a minimally displaced incomplete fracture. Both horses were treated conservatively and returned to train and race successfully postinjury. Veterinary     

ABNORMAL BONE SCAN FINDINGS OF THE EQUINE ISCHIAL TUBEROSITY AND THIRD TROCHANTER

Obtaining high-quality radiographs of the proximal aspect of equine limbs is difficult because of the large muscles in these regions. The use of scintigraphy may provide further information. Abnormal bone scan findings of the ischial tuberosity or the third trochanter were found in 29 adult horses with obscure hind limb lameness between 1986 and 1996 at the Large Animal Clinic of the University of Bern. Each had abnormal radiopharmaceutical uptake but not all had radiographic changes. Radio-pharmaceutical uptake ratios between the ischial tuberosity and the greater trochanter were calculated. The uptake ratio in a control group of 11 clinically sound horses was lower than in 11 lame horses with subjectively enhanced radiopharmaceutical uptake.     

The sacroiliac joints: evaluation using nuclear scintigraphy. Part 2: Lame horses

REASONS FOR PERFORMING STUDY: Sacroiliac (SI) joint disease is difficult to diagnose definitively on clinical grounds. HYPOTHESES: Lameness not attributable to SI joint pain may result in asymmetrical uptake of radiopharmaceutical in the tubera sacrale and SI joints; and that horses with clinical signs suggestive of sacroiliac joint disease would have differences in the ratios of radiopharmaceutical uptake between the fifth lumbar vertebra (L5) and either the tubera sacrale or SI joints compared with normal horses. OBJECTIVES: To determine whether differences in radiopharmaceutical activity could identify individuals with presumed SI joint region pain. METHODS: The scintigraphic appearance of the pelvic region of 234 horses (Group I) with lameness unrelated to the SI joints was compared with that for 40 normal horses (Group N) in full work and that for 41 horses with suspected SI joint disease (Group II). The effect of age, sex, lame limb and discipline were assessed in Group I. Motion-corrected scintigraphic images were assessed grossly, using profile analysis and by comparing ratios of uptake of mean count per pixel between L5 and each of the left (L) tuber sacrale (TS), right (R) TS, LSI and RSI joints. Left-right symmetry was compared. RESULTS: Lame horses (Group I) had greater asymmetry of radiopharmaceutical uptake in the tubera sacrale compared with normal horses. Horses with right hindlimb lameness had a larger RSI/LSI ratio compared to normal horses. In Group I L5/LTS, L5/RTS and L5/RSI increased with age, and there was a trend for L5/LSI to increase with age. In horses with presumed sacroiliac joint disease (Group II), L5/LTS, L5/RTS and L5/RSI were all greater compared with normal horses. Detection of marked left-right asymmetry by quantitative analysis or profile analysis was helpful in discriminating between those horses with clinical signs compatible with SI joint disease and either normal horses or those lame due to another cause. CONCLUSIONS AND POTENTIAL RELEVANCE: Scintigraphic evaluation of the SI region is useful to identify SI joint disease in combination with other clinical signs supportive of the diagnosis. However, diagnosis should not be based on this alone because of some degree of overlap in the range of radiopharmaceutical uptake between horses with SI joint disease and both normal horses and those with other causes of lameness.     

Use of multisite quantitative ultrasonography for noninvasive assessment of bone in horses

OBJECTIVE: To evaluate the usefulness of multisite quantitative ultrasonography for noninvasive assessment of bone in horses. SAMPLE POPULATION: 12 healthy horses and both forelimbs from 8 clinically normal horses. PROCEDURE: For in vivo measurements, various regions of interest (ROI) were examined on the third metacarpal bone, radius, and tibia. Precision error for speed of sound (SOS) measurements was obtained by measuring each ROI of 4 horses 10 times with probe repositioning. Additionally, 3 operators measured each aspect of the third metacarpal bone of 6 horses 5 times each. For ex vivo measurements, third metacarpal bones were examined at 9 ROI, and SOS measurements were performed before and after soft tissue removal. One ROI of a single forelimb was subjected to 96 ex vivo measurements with 3 different contact media. RESULTS: The lateral aspect of the third metacarpal bone had significantly higher SOS values than the dorsal and medial aspect of the third metacarpal bone. No difference was obtained between SOS values of the lateral and medial aspect of the radius. The tibia had significantly higher SOS values than the lateral aspect of the radius and the dorsal and medial aspect of the third metacarpal bone. Intraoperator coefficients of variation ranged from 0.62 to 3.15%, and interoperator coefficients of variation ranged from 0.78 to 2.70%. Values of SOS were highest when silicone oil was used as the contact medium. CONCLUSIONS AND CLINICAL RELEVANCE: Speed of sound measurements obtained by quantitative ultrasonography in axial transmission mode can be used to precisely measure superficial cortical bone properties of third metacarpal bone, radius, and tibia in horses.     

A Quantitative Review of the Equinalysis System for Equine Locomotion Analysis

Movement analysis techniques allow objective and quantitative assessment of kinematic gait analysis. Consistent repeatability of the kinematic data is essential for such assessments. This study investigated whether the repeatability of a standardized Equinalysis Elite gait analysis system is sufficient to allow its use in clinical evaluation of equine lameness with reliable documentation of individual locomotion patterns. The extent to which examinations on different days affected the results when a standardized protocol was used was investigated. The repeatability of distal limb kinematics in nine sound horses over three successive days at one location was investigated. Measurements were performed at the examination area, for three motion cycles at the walk and trot, in each direction per day. Skin markers were placed on the lateral aspect of the coffin joint, forelimb fetlock joint, hindlimb fetlock joint, carpus, tarsus, elbow, and stifle, at clipped sites marked with a permanent marker. The inter-day repeatability of angular measurements of the carpus, tarsus, forelimb fetlock, and hindlimb fetlock joints was determined. A low degree of inter-day repeatability was found with statistically significant (P ≤ .05) differences between findings on different days, observed in the time-angle diagrams of left and right carpus, tarsus, forelimb fetlock, and hindlimb fetlock joints of all horses, at both walk and trot. The standardized Equinalysis Elite system for gait analysis of distal limb kinematics in the horse did not provide highly repeatable data in this setting.     

Is there a characteristic distal tarsal subchondral bone plate thickness pattern in horses with no history of hindlimb lameness?

REASONS FOR PERFORMING STUDY: Osteoarthritis (OA) is a common cause of distal tarsal pain, but disease development is poorly understood. Awareness of normal tarsal structure and function is important in order to understand the pathogenesis of OA. Thickening of the subchondral bone (SCB) plate has been related to the development of OA, but SCB plate patterns in the equine tarsus have not been documented. HYPOTHESES: There is a repeatable pattern of SCB thickness across the distal tarsal joints, and specifically that thickness would be greatest dorsally and laterally. METHODS: Twenty cadaver tarsi were collected from mature horses that had undertaken low-level exercise only with no history of hindlimb lameness. Magnetic resonance images were acquired using a high-resolution sagittal 3-dimensional T1-weighted spoiled gradient echo sequence. Subchondral bone thickness was measured on sagittal images at dorsal and plantar locations on the proximal and distal aspects of the central (CT) and third (T3) tarsal bones and proximal aspect of the third metatarsal bone (Mt3). RESULTS: On the proximal aspect of CT, medial and lateral SCB thickness were significantly greater than midline. On the distal aspect of CT and T3 and proximal Mt3, lateral SCB thickness was significantly greater than medial and midline sites. Dorsal SCB thickness was greatest on the proximal and distal aspects of CT and proximal Mt3. Subchondral bone accounted for a greater proportion of CT and T3 on the dorsal aspect than the plantar. CONCLUSIONS: There is a repeatable pattern of SCB thickness in the distal tarsal bones of horses with no history of hindlimb lameness. This reflects the pattern of loading across the joints. POTENTIAL RELEVANCE: This study provides evidence of a consistent osteochondral pattern in the equine tarsus for reference in identification of osteoarticular pathologies.