The cat vertebral column: stance configuration and range of motion |
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Authors: | J M Macpherson Y Ye |
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Institution: | (1) R.S. Dow Neurological Sciences Institute, 1120 N.W. 20th Ave., Portland, OR 97209 USA e-mail: jane@NSI.LHS.ORG, Fax: +1-503-413-7229, US;(2) Department of Surgery (Otolaryngology), University of Connecticut Health Center, Farmington, CT 06030–1110, USA, US |
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Abstract: | This study examined the configuration of the vertebral column of the cat during independent stance and in various flexed positions.
The range of motion in the sagittal plane is similar across most thoracic and lumbar joints, with the exception of a lesser
range at the transition region from thoracic-type to lumbar-type vertebrae. The upper thoracic column exhibits most of its
range in dorsiflexion and the lower thoracic and lumbar in ventroflexion. Lateral flexion is limited to less than 5° at all
segments. The range in torsion is almost 180° and occurs primarily in the midthoracic region, T4-T11. Contrary to the depiction
in most atlases, the standing cat exhibits several curvatures, including a mild dorsiflexion in the lower lumbar segments,
a marked ventroflexion in the lower thoracic and upper lumbar segments, and a profound dorsiflexion in the upper thoracic
(above T9) and cervical segments. The curvatures are not significantly changed by altering stance distance but are affected
by head posture. During stance, the top of the scapula lies well above the spines of the thoracic vertebrae, and the glenohumeral
joint is just below the bodies of vertebrae T3-T5. Using a simple static model of the vertebral column in the sagittal plane,
it was estimated that the bending moment due to gravity is bimodal with a dorsiflexion moment in the lower thoracic and lumbar
region and a ventroflexion moment in the upper thoracic and cervical region. Given the bending moments and the position of
the scapula during stance, it is proposed that two groups of scapular muscles provide the major antigravity support for the
head and anterior trunk. Levator scapulae and serratus ventralis form the lateral group, inserting on the lateral processes
of cervical vertebrae and on the ribs. The major and minor rhomboids form the medial group, inserting on the spinous tips
of vertebrae from C4 to T4. It is also proposed that the hypaxial muscles, psoas major, minor, and quadratus lumborum could
support the lumbar trunk during stance.
Received: 2 January 1997 / Accepted: 23 September 1997 |
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Keywords: | Vertebral column Antigravity support Scapula Cat |
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