Synostosis of the first and second ribs in six horses.
Abstract: CASE DESCRIPTION Over a 2-year period, 6 horses (4 Selle Français, 1 Hanoverian, and 1 Thoroughbred) were referred for evaluation of forelimb lameness. All horses had radiographic evidence of synostosis of the first and second ribs (SFSR). CLINICAL FINDINGS For 1 horse, the SFSR was considered the probable cause of the lameness (grade 3/5), with a shortening of the cranial phase of the stride in the affected limb. For 3 horses, it was considered a possible cause of the lameness (grade 1/5) for the same reason. For 2 horses, SFSR was considered an incidental finding unassociated with any clinical signs. The 4 horses with lameness suspected as attributable to SFSR had a moderate to severe amount of irregularly marginated new bone formation at the site of the SFSR, with a cranial displacement of the first rib, compared with findings for the 2 horses in which the SFSR was considered incidental. A likely congenital abnormality of the first rib was first suspected on nuclear scintigraphy in the 1 horse for which it was performed or on radiography of the caudal cervical portion of the vertebral column (3 horses) or shoulder joint (2 horses). TREATMENT AND OUTCOME The horse in which SFSR was considered the probable cause of the lameness was retired to the field and remained chronically lame. Two of the 3 horses in which SFSR was considered a possible cause of lameness received an IV infusion of tiludronate disodium and mesotherapy over the caudal cervical and cranial thoracic regions; both returned to competition but with poor results. One of the 2 horses with subclinical SFSR never developed lameness on the affected side. No follow-up information was available for the other 2 horses. CLINICAL RELEVANCE SFSR can be an incidental finding in horses, with or without clinical manifestations. This abnormality should be considered as a differential diagnosis for horses with forelimb lameness and associated shortening of the cranial phase of the stride that fails to improve with diagnostic analgesic techniques.
Publication Date: 2018-08-16 PubMed ID: 30110211DOI: 10.2460/javma.253.5.611Google Scholar: Lookup
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Summary
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The research article describes a two-year study of a rare bone condition in six horses that resulted in the fusing together, or synostosis, of their first and second ribs. This condition, which was discovered as the horses were being evaluated for lameness in their forelimbs, was suspected to be a contributing factor to lameness in some cases, while in others it was an incidental finding with no associated clinical signs.
Case Description and Findings
- The study spanned two years and involved six horses of varying breeds (4 Selle Français, 1 Hanoverian, and 1 Thoroughbred) that presented with lameness in their forelimbs.
- Upon examination, all horses showed radiographic proof of a rare condition known as synostosis of the first and second ribs (SFSR).
- For one horse, the SFSR was believed to be the likely cause of its moderate lameness (rated as 3/5 in intensity), which was characterized by a shorter cranial phase of stride in the affected limb.
- For three other horses, SFSR was considered a potential cause of their mild lameness (rated as 1/5).
- In two instances, SFSR was observed but did not seem connected with any observable symptoms and thus was seen as an incidental finding.
- The horses with suspected SFSR-induced lameness showed moderate to severe irregular bone growth at the synostosis site and a forward displacement of the first rib.
- For these horses, the fused ribs were first noticed either through nuclear scintigraphy (one horse) or through radiography of the lower neck and/or shoulder joint.
Treatment and Outcome
- The horse suspected to have lameness due to SFSR was retired and remained persistently lame.
- Two of the horses where SFSR was seen as a possible cause of the lameness were treated with intra-venous tiludronate disodium (a bone resorption inhibitor) and mesotherapy (a non-surgical skin rejuvenation technique) applied over the lower neck and upper chest regions. Although they returned to competition, the results were poor.
- One of the horses with incidental SFSR did not develop lameness. Follow-up information was not available for the other two horses.
Clinical relevance
- The study indicated that SFSR can exist in horses without causing any symptoms, making it an incidental finding.
- However, when evaluating horses for forelimb lameness and associated stride issues that do not improve with pain management techniques, SFSR should be considered as a potential diagnosis.
Cite This Article
APA
Rovel T, Coudry V, Denoix JM, Audigie F.
(2018).
Synostosis of the first and second ribs in six horses.
J Am Vet Med Assoc, 253(5), 611-616.
https://doi.org/10.2460/javma.253.5.611 Publication
Researcher Affiliations
MeSH Terms
- Animals
- Diagnosis, Differential
- Female
- Horse Diseases / diagnosis
- Horse Diseases / diagnostic imaging
- Horses
- Lameness, Animal / etiology
- Male
- Pedigree
- Radiography / veterinary
- Ribs / abnormalities
- Synostosis / complications
- Synostosis / diagnosis
- Synostosis / veterinary
- Ultrasonography / veterinary
Citations
This article has been cited 3 times.- Spriet M, Vandenberghe F. Equine Nuclear Medicine in 2024: Use and Value of Scintigraphy and PET in Equine Lameness Diagnosis. Animals (Basel) 2024 Aug 28;14(17).
- Dyson S, Phillips K, Zheng S, Aleman M. Congenital variants of the ventral laminae of the sixth and seventh cervical vertebrae are not associated with clinical signs or other radiological abnormalities of the cervicothoracic region in Warmblood horses. Equine Vet J 2025 Mar;57(2):419-430.
- Ros KB, Doveren A, Dreessen C, Pellmann R, Beccati F, Zimmermann E, Distl O. Radiological Methods for the Imaging of Congenital Malformations of C6-T1, the First and Second Sternal Ribs and Development of a Classification System, Demonstrated in Warmblood Horses. Animals (Basel) 2023 Dec 2;13(23).
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