The skeletal system in horses comprises a complex structure of bones that provide support, protection, and mobility. Equine bones are involved in various physiological functions, including mineral storage and hematopoiesis. The bone structure in horses is categorized into different types, such as long bones, short bones, flat bones, and irregular bones, each serving specific roles in movement and stability. Research in this area explores topics such as bone development, remodeling, and the impact of nutrition and exercise on bone health. This page gathers peer-reviewed studies and academic articles that focus on the anatomy, physiology, and pathology of bones in horses, offering insights into conditions such as fractures, bone diseases, and the effects of aging on the equine skeletal system.
Greene EA, Smith KR, Pendergraft JS, Raub RH, Arns MJ.When the decision was made to euthanatize an acutely laminitic Thoroughbred broodmare, graduate students from the Department of Animal Sciences and Industry reconstructed the skeleton for use as a teaching tool. The reproductive and gastrointestinal tracts were removed and preserved in formalin. The hide, muscle, tendons, ligaments, and organs were removed, and the bones were boiled in water for > or = 48 h to remove all remaining tissue. After boiling, the bones were soaked in gasoline to remove fat from the marrow cavities and then soaked in a bleach/detergent mixture as a final cleaning ...
Glade MJ.Skeletal homeostasis during late gestation, lactation, and the post-lactational recovery period is poorly understood. In an experiment using an animal model (the horse), metacarpal breaking strengths (MBS) estimated via transmission ultrasonics were examined during the last 12 weeks of gestation and for 40 weeks after parturition. MBS increased during the last 6-10 weeks of gestation in mares fed amounts of calcium (Ca) recommended by the National Research Council; maximum MBS coincided with the week of parturition. In contrast, MBS in mares fed 20% less Ca remained relatively constant during ...
Kobluk CN.Lateral luxation of the patella in four femoropatellar joints of three foals was repaired by recession sulcoplasty and medial imbrication of the joint. One foal was euthanatized because of septic arthritis caused by incisional dehiscence, and the other two foals were normal 2 years after surgery. Recession sulcoplasty combined with medial imbrication of the joint capsule resulted in a functional femoropatellar joint and should be considered in foals affected with lateral patellar luxation.
Kaneps AJ, O'Brien TR, Redden RF, Stover SM, Pool RR.The distal phalanx and metacarpal physis of both forelimbs of 32 Thoroughbred foals 3-32 weeks of age were radiographed to identify those limbs with osseous bodies at a palmar process (PP) of the distal phalanx. Osseous bodies (ossicles) were identified radiographically in 19% of the foals. Sixteen of the 32 foals were selected for microradiographic and histological evaluation: 6 foals with radiographic evidence of ossicles and 10 foals without. Fourteen ossicles of the PP were observed radiographically. Ossicles were either a triangular bone fragment at the palmar aspect of the distal angle o...
Todhunter RJ, Altman NS, Kallfelz FA, Nersesian P, Lust G.Combined blood pool and delayed images produced by use of 99mTc-methylene diphosphonate (99mTcMDP) were evaluated as an objective measurement of the response of equine joints with osteochondral defects to postoperative exercise and intra-articularly administered polysulfated glycosaminoglycan (PSGAG). Osteochondral defects (approx 2.4 x 0.9 cm) were induced arthroscopically in the dorsodistal radial carpal bones of 18 ponies. These ponies were randomized (while balancing for age [range 2 to 15; median, 5.0; mean, 5.1 years]) to 2 treatment groups. Nine ponies were assigned to be exercised, and...
Grøndahl AM, Dolvik NI.Radiography of the tibiotarsal and metacarpo- and metatarsophalangeal joints was performed on 753 Standardbred trotters (6 to 21 months old) born in 1988. The surveyed population was drawn at random from all parts of Norway and represented about 60% of Standardbred trotters born the same year. Osteochondrosis in the tibiotarsal joint was diagnosed in 108 (14.3%) horses, and the prevalence of disease in progeny groups > 10 ranged from 0 to 69%. Bony fragments in the palmar/plantar portion of the metacarpo- and metatarsophalangeal joints were diagnosed in 89 (11.8%) horses, and the prevalence of...
Parente EJ, Richardson DW, Spencer P.Medical records of 57 horses admitted between 1980 and 1991 because of basal sesamoidean fractures were evaluated. Radiographic measurements of fragment size and fracture characteristics were recorded to determine their relationship to outcome. A successful outcome was assessed on the basis of the ability to return to racing, ability to race more than one time, and ability to finish first, second, or third. Any change in racing class also was assessed. There was a significant (P < 0.001) overrepresentation of Thoroughbreds, compared with other breeds in the hospital population. Fractures of...
Ragle CA.The equine head is especially prone to trauma from kicks, collisions, entrapments, and falls. The specialized structures of the equine head are important in both function and appearance. When injury causes either loss of function or cosmesis, timely treatment is paramount. This article discusses the occurrence and therapy of trauma to the equine head, including fractures of the mandible and premaxilla, facial bone, hyoid apparatus, and skull base.
Park RD.Radiographic examinations of the equine head can be performed with portable x-ray machines. The views comprising the examination depend on the area of the head being examined. With a knowledge of radiographic anatomy and radiographic signs of disease, valuable diagnostic information can be obtained from the radiographic examination. In addition, the radiographic information can also be used to develop a prognosis and determine the most appropriate therapy.
Driesang I, Böhm D.Both hock joints were examined clinically, radiologically and scintigraphically in 80 horses with special regard to bone spavin. The positive x-ray and bone scan results corresponded in most cases. It was evident that there was no correlation between degree of lameness and/or extent of radiological findings and increased radioactive uptake in the joint. Scintigraphic evaluation may demonstrate early changes at the onset of bone spavin as well as the frequent bilateral nature of the condition.
Riggs CM, Lanyon LE, Boyde A.A novel technique for determining the collagen fibre orientation pattern of cross-sections of cortical bone was used to study mid-diaphyseal sections from the equine radius. Several in vivo strain gauge studies have demonstrated that this bone is loaded in bending during locomotion in such a way that the cranial cortex is consistently subjected to longitudinal tensile strains and the caudal cortex to longitudinal compressive strains. Twenty-three radii from 17 horses were studied. All the bones obtained from adult horses exhibited a consistent pattern of collagen fibre orientation across the c...
Dyson SJ, Kidd L.Analgesia of the distal interphalangeal (DIP) joint and of the navicular bursa was performed independently in the lame or lamer forelimb of 59 horses, in which lameness was significantly improved by perineural analgesia of either the palmar digital or palmar (abaxial sesamoid) nerves. In 3 horses no improvement was detected. Lameness was improved by analgesia of the DIP joint but there was no response to analgesia of the navicular bursa in 3 horses. In 12 horses, lameness was improved by analgesia of the navicular bursa but intra-articular analgesia resulted in no change. Forty-one horses resp...
Riggs CM, Vaughan LC, Evans GP, Lanyon LE, Boyde A.Mechanical test specimens were prepared from the cranial and caudal cortices of radii from eight horses. These were subjected to destructive tests in either tension or compression. The ultimate stress, elastic modulus and energy absorbed to failure were calculated in either mode of loading. Analysis was performed on the specimens following mechanical testing to determine their density, mineral content, mineral density distribution and histological type. A novel technique was applied to sections from each specimen to quantify the predominant collagen fibre orientation of the bone near the plane...
Hance SR, Schneider RK, Embertson RM, Bramlage LR, Wicks JR.Medical records and radiographs were reviewed from 20 foals with caudal femoral condylar lesions. Osseous lesions were classified radiographically into 3 categories. Type-I lesions were characterized by a discrete area of radiolucency within the subchondral bone of the caudal aspect of a femoral condyle and were associated with septic arthritis and osteomyelitis. Type-II lesions had localized, osseous irregularities involving < 50% of the femoral condyle. Type-III lesions had widespread irregularities involving a large area of the condyle, and in 5 foals with type-III lesions, there was a thin...
Fenger CK, Bertone JJ, Biller D, Merryman J.Generalized medullary infarction of the long bones was diagnosed in a 12-year-old Tennessee Walking Horse mare. The mare was referred after a 6-week course of shifting weight on her hind limbs, and kicking. Physical examination revealed mild stifle joint distention and withdrawal reactions to digital pressure over the long bones. Radiography revealed patchy areas of medullary sclerosis in the distal portion of each femur and proximal portion of each tibia. A full-thickness cortical and cancellous tibial biopsy revealed infarcted bone marrow, with cortical and periosteal osteonecrosis. The caus...
Kaneko M, Oikawa M, Yoshihara T.Pathomorphological analysis was performed on fractured bones of 470 race horses. The most common fracture site was the limb (98% of cases), and the majority of fractures were intra-articular. Focal osteochondral lesions consisting of osteochondrosis, osteonecrosis and osteosclerosis were observed frequently in fractured and non-fractured bones. In the fractured bones, the lesions frequently appeared in the vicinity of the fractured site. Under the influence of antecedent osteochondrosis from the young stage, osteosclerotic and osteonecrotic lesions may have been induced by immoderate exercise ...
Linford RL, O'Brien TR, Trout DR.Lameness examinations and radiography of the distal phalanx and associated soft-tissue structures of the front feet of 103 Thoroughbred racehorses, 4 to 9 years old, were performed to determine normal radiographic appearance and morphometry. Of 103 horses examined, 41 were used in the study that were without clinical signs of foot problems or lameness, had raced at least twice prior to radiography, and had raced at least twice more in the 6 months after radiography. Lateromedial and dorsoproximal-palmarodistal radiographic views of each front distal phalanx were used to measure 28 bone and sof...
Davies HM, McCarthy RN, Jeffcott LB.Stacked rectangular rosette strain gages were used to measure surface bone strain on the dorsomedial cortex of the third metacarpal bones in 6 adult Thoroughbred horses during treadmill exercise. The peak principal compressive and tensile strains, angle of the peak strains and strain rate during loading were calculated and compared with speed and gait. At speeds from 4 to 14 m/s loading on the metacarpus resulted in compression of the dorsomedial cortex. Tension only occurred consistently in 1 forelimb of 1 horse at the walk (2 m/s). The angle of peak compression was within 10 degrees of the l...
Pleasant RS, Baker GJ, Foreman JH, Eurell JA, Losonsky JM.Navicular bone intraosseous pressure, gross pathologic, histologic, and histochemical data were collected from 8 horses with navicular disease and 4 control horses. Simultaneous navicular bone intraosseous, medial palmar arterial, and saphenous venous pressures were measured for the left and right forelimbs of each horse under general anesthesia. Gross pathologic evaluation included grading of changes on the flexor surface of the navicular bone. Safranin-O-fast green-stained sections were used for histologic-histochemical grading of the hyaline articular and fibrocartilage surfaces of the navi...
Lavoie JP, Carlson GP, George L.Hypertrophic osteopathy was diagnosed in 3 horses and in a pony, ranging in age from 8 to 21 years. There were 2 females, 1 sexually intact male, and 1 gelding. In 3 animals, hypertrophic osteopathy was associated with pulmonary abscesses, bronchogenic squamous cell carcinoma, and ovarian granulosa-cell tumor, respectively, and resulted in death or euthanasia. Duration of the condition ranged from 1 to 4 months. In 1 horse, hypertrophic osteopathy was believed to be secondary to pregnancy, and resolved following uncomplicated delivery of a live foal.
Pleasant RS, Baker GJ, Muhlbauer MC, Foreman JH, Boero MJ.The case records, radiographs, and nuclear bone scans of 58 horses with stress reactions or stress fractures of the proximal palmar aspect of the third metacarpal bone (MC3) were reviewed. There were 47 Standardbreds, 4 Quarter Horses, 3 Thoroughbreds, 2 Arabians, 1 Oldenburg, and 1 Pony of America. Fifty-six of the horses were racehorses or performance horses. The mean and median ages of affected horses were 4 and 3 years, respectively. Lameness ranged from mild to severe. Physical findings were usually subtle and included signs of pain on deep palpation of the proximal palmar aspect of MC3 a...
Stover SM, Pool RR, Martin RB, Morgan JP.The dorsal cortex of the equine third metacarpal mid-diaphyseal bone was characterised during growth by the histological and microradiographic examination of specimens from 30 horses ranging in age from 2 months to 8 y. Bone from horses aged less than 6 months was characterised by rapid periosteal apposition of circumferential trabeculae of woven bone that were next connected by radial trabeculae to the parent cortex. Deposition of lamellar bone on the inner trabecular surfaces resulted in rows of primary osteons. Replacement of primary bone occurred only after 4 months of age and preferential...
Wright IM.Clinical and radiological features of 16 horses with fractures of the lateral malleolus of the tibia are reported. The paper describes surgical techniques used, results obtained and discusses justification for removal. Fourteen fractures were unilateral and two bilateral. There was no left:right disparity. The history included a known traumatic incident in 14 cases. All animals had a tarsocrural joint effusion and 10 had palpable thickening of the lateral collateral ligaments. Crepitus was also palpable in 10 horses. The fracture was identified in all dorsoplantar and 14 of 18 dorsomedial-plan...
Lepage OM, Marcoux M, Tremblay A, Dumas G.The influence of sex on serum osteocalcin levels was studied in 99 Standardbred horses, 52 males and 47 females. The age varied between the day of birth and five years old. A significant inverse correlation (r = -0.87, p 0.05). When the subjects were divided into five age groups of six months or less, 6 to 18, 18 to 24, 24 to 36 and between 36 and 60 months, no significant influence of sex was noted. A predictive model for serum osteocalcin levels (y = 52.19 - 0.026 age in days, r2 = 0.76) for Standardbred horses aged between the day of birth and five years is described.
Jackman BR, Baxter GM.A 1-year-old Appaloosa stallion had a mass on the right rostral hemimandible. The mass was firm, did not cause signs of pain, and was identified as a bone cyst by radiography and biopsy. Surgical correction included curettage of the cystic cavity and grafting the defect with both cortical and cancellous bone. By 5 months, the cystic cavity was ossifying; continued remodeling with an increase in bone density was apparent 22 months after surgery.
Smyth GB, Taylor EG.A Salter-Harris type-II fracture of the proximal portion of the right femur in a 2-month-old filly was reduced and stabilized with three 6.5-mm-diameter, 100-mm-long cancellous bone screws through a dorsal approach to the right coxofemoral joint. The screws were removed after 11 months because the filly became lame in the affected limb. The surgical wounds dehisced despite preventive measures, most likely because of tightness of skin in the coxal region. Seven years after the original injury, the horse could perform vigorous paddock exercise without any disability. Early internal fixation of p...
Uhlhorn H, Carlsten J.The aim was to investigate radiographic findings of subchondral sclerosis and subchondral lucency in the dorsoproximal-dorsodistal (DPr-DDi) projection of the third carpal bone (C3) in relation to clinical appearance and to prognosis for racing. In a retrospective study, case records of 89 Standardbred trotters diagnosed with traumatic carpitis confirmed with intra-articular anaesthesia were examined. Records included data on degree of lameness at presentation and after flexion tests and a radiographic examination of the carpus, including a DPr-DDi projection of the C3. Subchondral lucency was...
Stolk PW, Firth EC.Intra-osseous pressure measurements in the third metatarsal bone of anesthetised young and mature ponies demonstrated that a pressure gradient exists along the bone, the pressure being highest at the level of the nutrient foramen and decreasing distally and proximally from this point. The height of the intra-osseous pressure pulse also decreased toward the bone ends. It is concluded that the sites of measurement of the intra-osseous pressure in clinical and experimental studies should be standardized.
Kottmeier LK, Seehusen F, Helweg M, Rohn K, Stadler P, Hellige M.Magnetic resonance imaging and the correlation to histopathological findings of the equine palmar foot of lame horses have been described previously, using 0.27 and 1.5 T systems. Compared to these, 3 T systems provide superior spatial resolution and imaging contrast. The aim of our prospective anatomic study was to characterize the imaging anatomy of the navicular region on 3 T MRI in comparison to histopathological findings. We hypothesized that 3 T MRI allows a good visualization of the entire navicular apparatus and reliable measurements of navicular cartilage and cortical bone thickness. ...
Milne DW, Turner AS, Gabel AA.In the horse, surgical approaches for plating fractures of the ulna, radius, metacarpus, tibia, and metatarsus involved a single curvilinear skin incision and incision of the superficial fascia in a manner to prevent postoperative dehiscence. The tension side of the bones, as well as location of nerves, arteries, veins, and muscles, were the major determinants in developing these approaches for atraumatic surgery and short operative time.
Jann HW, Breshears MA, Allison RW, Pechman RD, Day J, Hart JC, Moorman VJ.Intestinal adenocarcinomas are rare but have been described in the literature. The present case is unusual in both its clinical presentation and in the distribution of metastatic lesions. The sequestrum formation and pathological fracture present are most commonly associated with osteomyelitis in horses and the details of the case highlight the need for differential diagnosis in these particular circumstances and of which clinicians should be aware.
Gottschalk RD, Kirberger RM, Fourie SL.In order to establish the incidence of vacuum phenomenon in horses' carpal, metacarpophalangeal and metatarsophalangeal joints, stress-flexed radiographs were made of normal joints, joints with known pathology and in anaesthetised horses with joints under traction. Focal intra-articular radiolucencies were identified in normal stress-flexed carpal, metacarpophalangeal and metatarsophalangeal joints. These radiolucencies can be confused with those associated with pathological conditions.