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Articular Process-Synovial Intervertebral Articulation Complexes in Horses


The articular process-synovial intervertebral articulation (AP-SIVA) complex is located dorsally to the vertebral canal. It is composed of the caudal articular process of one vertebra, the synovial joint (with articular cartilage, synovial fluid and membrane, and articular capsule) located at the base of the interspinal space, and the cranial articular process of the following vertebra. Eight types of abnormal radiographic findings have been identified in the AP-SIVA complexes of the equine thoracolumbar spine (see Table 1: Abnormal Radiographic Findings in Articular Process-Synovial Intervertebral Articulation (AP-SIVA) ComplexesTables). These findings were mainly observed at the thoracolumbar junction and in the lumbar area. These abnormal findings were reported in adult horses but also in 3- to 6-yr-old race and sport horses. AP-SIVA lesions are much more likely to be associated with back pain than kissing spines or any other vertebral lesions.

Table 1

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With ultrasonography, loss of the joint space because of periarticular osteophytes and dorsal periarticular proliferation (types 4 and 6) can be detected. This procedure helps determine whether the proliferation is symmetric or, if not, which side is most affected.

Treatment and management include periarticular ultrasonographic-guided injections of steroids, mesotherapy over the painful area, and rehabilitation using tolerated exercises after progressive warm-up at a slow canter.

Last full review/revision March 2012 by Stephen B. Adams, DVM, MS, DACVS; Joerg A. Auer, DrMedVet, Dr h c, MS, DACVS, DECVS; James K. Belknap, DVM, PhD, DACVS; Jane C. Boswell, MA, VetMB, CertVA, CertES (Orth), DECVS, MRCVS; Peter Clegg, MA, Vet MB, PhD, CertEO, DECVS, MRCVS; Andrew L. Crawford, BVetMed, CertES (Orth), MRCVS; Jean-Marie Denoix, DVM, PhD, Agregé; Marcus J. Head, BVetMed, MRCVS; C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DACVS, DACVSMR; James Schumacher, DVM, MS, DACVS, MRCVS; John Schumacher, DVM, MS, DACVIM; Roger K. W. Smith, MA, VetMB, PhD, DEO, DECVS, MRCVS; Chris Whitton, BVSc, FACVSc, PhD

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