%0 Journal Article
%T Device for lengthening of a musculotendinous unit by direct continuous traction in the sheep
%A Matthias A Zumstein
%A Eric Frey
%A Brigitte von Rechenberg
%A Robert Frigg
%A Christian Gerber
%A Dominik C Meyer
%J BMC Veterinary Research
%D 2012
%I BioMed Central
%R 10.1186/1746-6148-8-50
%X After several steps of technical improvements, the tensioner proved to be capable of actively stretching the retracted and degenerated muscle back to the original length and to withstand the external forces acting on it.This technical report describes the experimental technique for continuous elongation of the musculotendinous unit and reversion of the length of chronically shortened muscle.Chronic rotator cuff tears lead to retraction of the musculotendinous unit, atrophy and hitherto irreversible fatty infiltration of the rotator cuff muscles [1-6]. In the sheep, muscle retraction and fatty infiltration were shown to be related to a pronounced change in the pennation angle of the infraspinatus muscle with consequent shortening but absence of degeneration of the muscle fibres [7-9]. This shortening of the fibres may reduce muscle mass by >50% as a result of a reduction of sarcomeres in series [8]. Physiologically, these muscles loose their contractile strength, range of contraction and elasticity [7,8,10-12]. These changes are not reversible with current tendon repair techniques.Muscle homeostasis is regulated by different mechanical signals [13,14], primarily by active or passive tension applied on the tissue, respectively. In response to an increase of length, the functional demand of the tissue may be higher and the muscle tissue may increase in size by appearance of embryonic tissue, indicating a proliferative response [15-17]. Skeletal muscle reacts differently following repeated tensile strains. Fast stretching has been reported to potentially disrupt muscle fibers and to lead to a proliferation of non-contractile tissue [18]. Conversely, slow, continuous stretching results in skeletal muscle hypertrophy by an increase in absolute muscle mass due to a moderate increase of myofiber cross sectional area [18,19] and by a substantial longitudinal increase of sarcomere in series [19-21]. It is not yet known, however, whether these mechanisms are effective in muscl
%K Muscle
%K Sheep
%K Retraction
%K Fatty infiltration
%K Atrophy
%K Pennation angle
%K Continuous traction
%U http://www.biomedcentral.com/1746-6148/8/50