Chronic tendon tears lead to retraction, fatty infiltration, and atrophy of the respective muscle. These muscle changes are decision-making criteria in rotator cuff tear management.
To investigate the functional implications of these morphological changes in a sheep rotator cuff tear model.
Controlled laboratory study.
The authors established chronic retraction of the musculotendinous unit accompanied with fatty infiltration and atrophy of the infraspinatus muscle in 20 sheep. The contractile force and passive tension of the muscle as a function of its length were measured and the active work capacity determined.
After tendon release and chronic retraction (by 5.7 ± 0.9 cm), fatty infiltrated and atrophied infraspinatus muscles (with a density of 22.4 ± 10.4 Hounsfield units [HU] and a cross-sectional area of 65% ± 16% of the contralateral control side) had a mean contractile amplitude and strength of 2.7 ± 0.4 cm and 235 ± 71 N compared with the contralateral control shoulder of 4.1 ± 0.7 cm and 485 ± 78 N (P < .05), respectively. The mean active work of the muscle was 2.8 ± 0.9 N·m for retracted and 8.8 ± 2.4 N·m for control muscles (P < .05). The correlation of total active work to fatty infiltration (r = 0.78, P < .001) was significant.
Chronic tendon tears are associated not only with retraction, fatty infiltration, and atrophy but also with loss of strength and contractile amplitude. The functional changes can only indirectly and approximately be predicted by computed tomography imaging findings.
The current criteria (atrophy, retraction, and fatty infiltration) may help to quantify the structural reparability of a chronically retracted musculotendinous unit after rotator cuff tendon tear but may only approximately predict the remaining function of the muscle.
"In case of tendon tears, disuse, denervation, cachexia or myodystrophic disease muscular atrophy is a common and unavoidable consequence. The pathophysiologic mechanisms and the histological and biochemical changes differ greatly between these different etiologies, however fatty infiltration and the consequent decrease of muscle cross sectional area results in declined muscle strength, elasticity and range of joint motion [13-15]. "
[Show abstract][Hide abstract] ABSTRACT: It seems appropriate to assume, that for a full and strong global shoulder function a normally innervated and active deltoid muscle is indispensable. We set out to analyse the size and shape of the deltoid muscle on MR-arthrographies, and analyse its influence on shoulder function and its adaption (i.e. atrophy) for reduced shoulder function.
The fatty infiltration (Goutallier stages), atrophy (tangent sign) and selective myotendinous retraction of the rotator cuff, as well as the thickness and the area of seven anatomically defined segments of the deltoid muscle were measured on MR-arthrographies and correlated with shoulder function (i.e. active abduction). Included were 116 patients, suffering of a rotator cuff tear with shoulder mobility ranging from pseudoparalysis to free mobility. Kolmogorov-Smirnov test was used to determine the distribution of the data before either Spearman or Pearson correlation and a multiple regression was applied to reveal the correlations.
Our developed method for measuring deltoid area and thickness showed to be reproducible with excellent interobserver correlations (r = 0.814--0.982).The analysis of influencing factors on active abduction revealed a weak influence of the amount of SSP tendon (r = -0.25; p < 0.01) and muscle retraction (r = -0.27; p < 0.01) as well as the stage of fatty muscle infiltration (GFDI: r = -0.36; p < 0.01). Unexpectedly however, we were unable to detect a relation of the deltoid muscle shape with the degree of active glenohumeral abduction. Furthermore, long-standing rotator cuff tears did not appear to influence the deltoid shape, i.e. did not lead to muscle atrophy.
Our data support that in chronic rotator cuff tears, there seems to be no disadvantage to exhausting conservative treatment and to delay implantation of reverse total shoulder arthroplasty, as the shape of deltoid muscle seems only to be influenced by natural aging, but to be independent of reduced shoulder motion.
[Show abstract][Hide abstract] ABSTRACT: Rotatorenmanschettenläsionen sind häufig und die Inzidenz steigt mit zunehmendem Alter. Nach einer Sehnenruptur der Rotatorenmanschette kommt es zu einer Retraktion der muskulotendinösen Einheit, was mit einer Muskelverfettung (fettige Infiltration), einer Atrophie sowie einer interstitiellen Fibrose der Muskulatur einhergeht und die Muskelarchitektur grundlegend verändert. Diese Umgestaltungen gelten als wichtige prognostische Faktoren für das Ergebnis einer operativen Rotatorenmanschettenrekonstruktion. Die Wahl des richtigen Zeitpunkts der Rekonstruktion sowie eine optimale mechanische Fixation sind mitentscheidend für das erfolgreiche Einheilen der Sehne an der Knocheninsertion. Hierbei spielt die Kenntnis pathophysiologischer Vorgänge eine wichtige Rolle. Ziel dieses Artikels ist es, die bis heute existierende Evidenz bezüglich der präoperativ bestehenden Veränderungen der muskulotendinösen Einheit mit der Wahl des Operationszeitpunkts und der Operationstechnik in Beziehung zu setzen.
[Show abstract][Hide abstract] ABSTRACT: Musculotendinous retraction is a limiting factor for repair of long-standing rotator cuff tears. However, it is currently unknown to what extent the muscle and tendon contribute to the degree of total retraction. Further understanding of this may possibly influence the strategy of musculotendinous reconstruction.
To analyze the contribution of muscle and tendon to the process of myotendinous retraction.
Cross-sectional study; Level of evidence, 3.
Magnetic resonance imaging of 130 shoulders with intact (n = 20) or completely torn supraspinatus tendons was analyzed. Fatty infiltration of the supraspinatus muscle was graded according to Goutallier stages. The degree of retraction of the tendon stump and of the musculotendinous junction was assessed.
There were 30 shoulders without evidence of supraspinatus fatty infiltration, 25 with stage 1, 23 with stage 2, 25 with stage 3, and 15 with stage 4 changes. The corresponding tear sizes (distance of tendon end from greater tuberosity) were 4, 21, 27, 37, and 41 mm; the distance of the myotendinous junction from the greater tuberosity was 22, 33, 39, 48, and 48 mm; and the length of the tendons (distance of tendon end to myotendinous junction) was 19, 13, 12, 11, and 8 mm, respectively. In Goutallier stage 3 and above, and in case of a positive tangent sign, the musculotendinous junction was, in 90% of the cases, retracted to or beyond the glenoid.
Musculotendinous retraction in chronic rotator cuff tears results mainly from shortening of the muscle fibers but in advanced stages results also from shortening of the tendon tissue itself. The present data demonstrate, for the first time, that the residual tendon stump in a tendon tear does not have the length of the original tendon and is further shortened over time. Therefore, direct anatomic tendon reinsertion will result in lengthening of the supraspinatus muscle greater than what it would have been before the tear.
The American Journal of Sports Medicine 12/2011; 40(3):606-10. DOI:10.1177/0363546511429778 · 4.36 Impact Factor
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