Abstract
Nowadays, horses have to train and perform in high-level sportive and leisure activities. Injuries of the locomotor system with a decreased functionality or pain of the back are often seen in equine hospitals. In general, the relationship between limb and vertebral column function in mammals is complex and has been
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of scientific interest for long time. The age-old bow-and-string concept of the mammalian back, which implies that several body parts influence back motion (Barthez 1798; Slijper 1946), needed a detailed update. In horses, the origin and pathogenesis of back problems are difficult to predict with clinical examination alone, and thus deserves an objective evaluation and investigation. Modern gait analysis technology allows for an objective, more accurate and detailed analysis of body kinematics to study how limbs interact with vertebral column movement (Chapter-1). In Chapter-2 it was shown that changes in the head-and-neck position influence back kinematics. Lowering the head-and-neck flexes the vertebral column, while it increases range of motion (ROM); by lifting the head-and-neck the column extends and ROM becomes reduced. It was concluded that the low position of the head-and-neck increase vertebral movement. On the other hand, an extremely high head-and-neck position provokes reduced movement and an extended posture of the back. Back pain and lameness do coexist and commonly the primary cause of the problem is clinically found in the limbs. In Chapter-3 and-4 the relation between slight lameness and vertebral motion was investigated. It was shown that even subtle forelimb and hindlimb lameness provoke systematic changes in pelvic and thoracolumbar kinematics. Induced forelimb lameness provoked increased ROM and changed the pattern of thoracolumbar motion in the sagittal and horizontal planes. Hindlimb lameness resulted in hyperextension and increased ROM of the back, but also in a decreased ROM of the lumbosacral segment. All changes presumably are done in an attempt to unload the affected limb. In Chapters-5 and-6 it was shown that induced unilateral back pain affects back and limb kinematics. Vertebral ROM increased, the position of the back was more extended and showed increased lateral motion. However, the effect of back pain on limbs was rather minimal consisting in decreased flexion of some of the joints of all four limbs during swing phase. Thus, it can be assumed that primary back pain is unlikely to produce important changes in the limbs. In Chapter-7 the effect of chiropractic manipulations on horses with back pain was studied. Understanding the effect of back and limb pain experimentally, it could be hypothesized that treating back pain would induce biomechanical changes in the vertebral column. The main effect of the chiropractic manipulations was a less extended thoracic back, enhanced vertebral ROM, a reduced inclination of the pelvis and improvement of the symmetry of its motion. It can be concluded that there is a tight functional relationship between vertebral column and limbs. When pain is present in any component, the balance between them will be affected. In a similar way, when changes in posture are imposed to the horse the whole motion chain within the axial and appendicular skeleton will be influenced.
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