Myositis ossificans in cervical skeletal striated musculature of a horse - case reportABSTRACT
A case of myositis ossificans in the cervical region of a fifteen year old mare of unspecified breed, medium size, without obvious clinical signs, has been described. The disease was discovered in a radiograph image taken on a training of students in a course of radiodiagnostics. The radiograph image showed an area of increased radiopacity compatible with bone radiopacity, showing irregular contours and a multiple widespread appearance in the epaxial musculature of the cervical region. The mineralized area, considered extensive, occupied the dorsal region from the 4th cervical vertebra (C4) to the vicinity of the 1st thoracic vertebra (T1), slightly dorsal to the dorsal processes of the C4-T1 segment. An ultrasound examination of the left and right lateral cervical regions from C4 to T1 was performed on both sides of the animal using the ESAOTE® My LAB70 unit with a 12 to 18 MHz linear transducer. Based on the clinical history, radiographic and ultrasound images, and similarity to lesions reported in the literature, the diagnosis was myositis ossificans in the cervical region with partial ossification of the muscles, a condition considered uncommon in this species.
Keywords:
equine radiology; equine epaxial musculature ultrasonography; heterotopic ossification diagnosis
RESUMO
Descreve-se um caso de miosite ossificante na região cervical de uma égua de 15 anos, sem raça definida e de porte médio, sem sinais clínicos aparentes. A condição foi descoberta durante uma radiografia realizada para treinamento de estudantes em um curso de radiodiagnóstico. A radiografia revelou uma área de radiopacidade aumentada, compatível com radiopacidade óssea, com contornos irregulares e aspecto múltiplo disseminado na musculatura epaxial da região cervical. A área mineralizada, considerada extensa, ocupava a região dorsal desde a quarta vértebra cervical (C4) até a proximidade da primeira vértebra torácica (T1), ligeiramente dorsal aos processos dorsais do segmento C4-T1. Foi realizado um exame ultrassonográfico das regiões cervical lateral esquerda e direita, avaliando-se desde a vértebra C4 até a vértebra T1 em ambos os lados do animal, por meio do aparelho ESAOTE® My LAB70 com transdutor linear de 12MHz a 18MHz. Com base no histórico clínico, nas imagens radiográficas e ultrassonográficas e na semelhança com lesões relatadas na literatura, chegou-se ao diagnóstico de miosite ossificante na região cervical com ossificação parcial da musculatura, condição considerada incomum nesta espécie.
Palavras-chave:
radiologia equina; ultrassonografia de musculatura epaxial equina; diagnóstico de ossificação heterotópica
INTRODUCTION
Myositis ossificans is a rare tissue change, usually secondary to a traumatic or primary inflammatory lesion, that progresses to post-traumatic or post-inflammatory muscle fibrosis and worsens to heterotropic ossification in striated skeletal muscle (Pool and Thompson, 2002). This condition has already been observed in equine pelvic limbs, especially in the Quarter Horse breed (Pool and Thompson, 2002). (Dabareiner et al., 2004), and has also been described in the Colombian Creole (Rosas, 2019) and in 2023, the authors Benites (2024) described the case of a male Lusitano horse.
Calcinosis circumscripta (tumoral calcinosis) is the most common name for a muscular mineralizing lesion in the femoro-tibiopatellar region. This condition is characterized by a single lesion or multiple nuclei of dystrophic mineralization that clinically results in a concentric subcutaneous lesion with a slightly fluctuant appearance, most commonly located in the lateral region. The areas of mineralization have irregular contours and an ellipsoid shape in soft tissues, with radiopaque areas of granular distribution (Butler et al., 2016).
MATERIAL AND METHODS.
This study was conducted under the approval of the Ethics Committee on Animal Experimentation, with protocol number 0581/2023.
The radiographic examination was performed using a JOB portable X-ray unit in conjunction with a Leonardo DR Mini II (OR Technology) digital image detector or digital panel with Wi-Fi image transmission signal, with a CareView 750Cw (2022) digital board. The exposure factors used in the technique were 70 kV/1.65 mAs and a focus-film distance of approximately 80cm.
The mare was placed in a quadruped position (Fig. 1), restrained in a containment trunk, and led only by halter and rope. There was no need to restrain the mare with drugs or other restraint methods.
The ultrasound examination was performed using an ESAOTE® My LAB70 ultrasound device with a 12 to 18 MHz linear multifrequency transducer. The procedure was preceded by the application of 70% isopropyl alcohol. Ultrasound gel was used to minimize skin contact artifacts. The left lateral cervical region was scanned first, followed by the right lateral cervical region, and the ultrasound evaluation was performed between cervical vertebra C4 and thoracic vertebra T1 on both sides of the animal. The transducer positioning images are shown in Figures 2 A and 2 B.
Female of equine species aged 15 years and 9 months and weighing 250kg, of mixed breed, in quadrupedal support with region of interest (ROI) delimitation for detailed evaluation using external metal markers adhered to the cervical region. The DR digital image detector was positioned on the cervical region for latero-lateral projection, on the left lateral cervical region, centered on the center of the DR digital image detector.
A. Female of equine species aged 15 years and 9 months and weighing 250kg, of mixed breed, in quadrupedal support. Transducer positioning shown in longitudinal view of the left lateral cervical region. Figure 2 B. Transducer positioning shown in transversal view of the right lateral cervical region.
CASUISTRY
This case report concerns a mixed breed mare, aged 15 years and 9 months and weighing 250kg, belonging to the animal herd of the the Department of Clinical Medicine. This animal, which is free in a paddock and has a body score of 2 on a scale of 5, is used for practical classes in the undergraduate course of Veterinary Medicine, under the care of teaching professionals, for non-invasive practices and practical class procedures.
During a course in equine radiology in September 2022, the mare in question was taken to the radiology room of the Department of Radiology and Animal Reproduction for training in radiographic positioning of the cervical region of the spine. During the radiographic study, the presence of a large area of radiopacity was noted, similar to bone, but with irregular contours and a multiple widespread appearance in the epaxial musculature of the cervical region. The mineralized area was considered extensive as it occupied the dorsal region from the 4th cervical vertebra (C4) to the proximity of the 1st thoracic vertebra (T1), slightly dorsal to the dorsal processes of the C4-T1 segment.
The same mare was radiographed again in January 2023, when ultrasound was also performed to better determine the appearance and size of the lesion.
Radiographs of the cervical region showed an area of mineralization in the cervical muscles with bone-like radiopacity, irregular borders, and a heterogeneous appearance (Fig. 3 and 4).
Laterolateral projection radiograph of the caudal cervical of the mixed breed female of equine species, region showing the caudal limit of the largest mass of dystrophic mineralization in the cervical skeletal musculature. Other smaller areas are seen caudodorsal to the larger area, with radiopacity similar to bone, located dorsal to the spinous process at T2. Asterisk = mineralized musculature; T2 = spinous process of the second thoracic vertebra; black filled arrow = points to the smaller mineralized areas located dorsal to the spinous process at T2.
Latero-lateral radiograph of the cervical spine of the mixed breed female of equine species showing an area of heterogeneous dystrophic mineralization, irregular in appearance and triangular in shape, located in the cervical musculature between the spinous processes of C4 and T1. Asterisk = mineralized musculature; t = trachea; C4 = fourth cervical vertebra; C5 = fifth cervical vertebra; C6 = sixth cervical vertebra.
In the ultrasound study using the transducer in cross-section, it was possible to evaluate the presence of an area of hyperechogenicity followed by an acoustic shadow artifact with a rounded shape, located between the spinous processes of the C4 to T1 vertebrae, and it was possible to evaluate a greater number of details of the areas of hyperechogenicity on the left side of the animal, revealing a greater proximity of the region of lesion to the probe of the device (Fig. 5 and Fig. 6).
Cross-sectional ultrasonograph examination of the muscles of the cervical region of the mixed breed female of equine species showing an area of hyperechogenicity followed by a shadow artifact (*) of rounded shape located between the spinous processes of C4 and T1. Examination performed on the left side of the animal with the transducer positioning in longitudinal view of the left lateral cervical region.
Cross-sectional ultrasound examination of the muscles of the cervical region of the mixed breed female of equine species, showing an area of hyperechogenicity, followed by a shadow artifact (*), with a rounded shape, located between the spinous processes of C4 and C5. Examination carried out with the transducer positioning in transversal view of the right lateral cervical region.
DISCUSSION
Myositis ossificans is a muscle disease that can affect several species and is rare in horses (Pool and Thompson, 2002). Clinical examination provides useful signs for diagnosis. Imaging techniques (radiography, ultrasound), as used in this case report, can suggest a diagnosis, and further resources such as computed tomography, magnetic resonance imaging, CK dosage, and biopsy can be used for definitive diagnosis.
Biopsies were avoided in this case report, as surgery and intramuscular or intravenous injections have been described in humans as well, as they may aggravate or exacerbate the inflammatory process. This type of lesion can be detected on plain radiographs two to four weeks after its onset, with peripheral calcification that, unlike osteosarcoma, progresses centrally. CT scans help to identify the central radiolucency. The differential diagnosis includes idiopathic calcinosis, dermatomyositis, and calcium metabolism disorders, facilitated by the presence of soft tissue ossifications (Moraes et al., 2012).
Corticosteroid levels were not measured as there may be no changes in these assays as reported by the investigator in other species such as dogs. The most common form of calcinosis is idiopathic, with no prior change in calcium or phosphorus, and ectopic mineralization occurs in normal soft tissues and may or may not be related to disturbances in corticosteroid levels. (Voll et al., 2009).
The lesion described in this report is an isolated case and does not present with clinical signs of limitation of local muscle movement or signs of increase or decrease in volume or local sensitivity or local pain, unlike the case described previously where the animal had a marked rigid structure with a firm consistency, about 7 cm long and with increased sensitivity to palpation, associated with grade 4 claudication. (Benites, 2024).
In this case report, the image of dystrophic calcification was a radiographic finding, and subsequent images were obtained in a single horse with myositis ossificans. The results, in combination with future cases, may facilitate the diagnosis and monitoring of the progression of this disease.
In the published studies that serve as a reference for this case report, the anatomic region involved was the pelvic limb, specifically the posterior region of the thigh, including the semitendinosus, semimembranosus, biceps femoris, and gracilis muscles (Dabareiner et al., 2004). In some cases, the lesion has also involved muscle fascia (Pool and Thompson, 2002). This mineralizing lesion is described in the referenced studies as calcinosis circumscripta and is located adjacent to the proximal third of the fibula and the caudal region of the femorotibial-patellar joint and may be unilateral or bilateral. Based on literature reports, the image obtained in the cervical region is suggestive of myositis ossificans, similar to case reports in the pelvic limb muscles in the semitendinosus, semimembranosus, biceps femoris, and gracilis muscles (Dabareiner et al., 2004).
CONCLUSION
Due to the similarity of the radiographic pattern of changes, the most compatible radiographic diagnosis is myositis ossificans in the cervical region. Comparative analysis with the literature suggests that myositis ossificans is a rare condition that develops from traumatic or inflammatory injury to fibrosis and ossification in skeletal muscle. This case is specialy rare because of its cervical location in a mixed breed horse, in contrast to the more common reports of myositis ossificans in equine pelvic muscles, particularly in breeds such as Quarter Horses, Colombian Criollos and Lusitano. The documentation of this case contributes to the understanding of the presentation and diagnosis of this uncommon condition in horses.
REFERENCES
- BUTLER, J.; COLLES, C.; DYSON, S.; KOLD, S.; POULOS, P. Clinical radiology of the horse. 4.ed. [Cambridge]: Blackwell Publishing Company, 2016.
- BENITES, G.A. Rev Acad Cienc Anim. Calcinose circunscrita em terço médio do músculo extensor lateral de membro pélvico em equino: relato de caso v.22(Supl.2), p.43, 2024
- DABAREINER, R.M.; SCHMITZ, D.G.; HONNAS, C.M.; CARTER, G.K. Gracilis muscle injury as a cause of lameness in two horses. J. Am. Vet. Med. Assoc., v.224, p.1630-1633, 2004.
- MORAES, F.B.D.; QUEIROZ FILHO, A.R.D.; SILVA, L.J.D. et al. Miosite ossificante progressiva: relato de caso. Rev. Bras. Ortop., v.47, p.394-396, 2012.
- POOL, R.R.; THOMPSON, K.G. Tumors of bones. In: MEUTEN, D.J. (Ed.). Tumors in domestic animals. 2002. v.4, p.245-317.
- ROSAS TOVAR, L. Calcinosis circunscrita en un equino criollo colombiano. 2019. 19f. Monografía (Trabajo de Finalizacióndel Curso) - Clinica Veterinaria de Grandes Animales, Universidad de Ciencias Aplicadas y Ambientales, COL.
- VOLL, R.; GALGA, H.; VOLL, L. et al. Calcinose tumoral cervical em cão. Acta Sci. Vet., v.37, p.53-57, 2009.
Publication Dates
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Publication in this collection
14 July 2025 -
Date of issue
Jul-Aug 2025
History
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Received
12 Sept 2024 -
Accepted
26 Oct 2024
