Involvement of the muscle-tendon junction in skeletal muscle atrophy: an ultrastructural study

Vol. 52 No. 1 Suppl., 2011
This supplement was not sponsored by Outside Organizations.


L. de Palma, M. Marinelli, M. Pavan, C. Bertoni-Freddari

Background: The muscle-tendon junction (MTJ) is a physiologically vital tissue interface and a highly specialized region in the muscle-tendon unit. It is the weakest point in the muscle-tendon unit, making it susceptible to strain injuries. Nonetheless, knowledge of the pathological changes affecting this region and of its response to the atrophy process is very limited. The aim of the study was to examine MTJ ultrastructural morphology in patients with different conditions that induce skeletal muscle atrophy and to attempt a grading of the atrophy process. Materials and Methods: Fifteen patients undergoing amputation in the distal or proximal third of the lower leg due to chronic or acute conditions were divided into two groups. Specimens of gastrocnemius muscle collected at the time of surgery were analyzed by histology and electron microscopy. The contact between muscle and tendon was measured using a dedicated software that calculated semi-automatically the base (B) and perimeter (P) of muscle cell finger-like processes at the MTJ. Results: Electron microscopy. The cells in the atrophic muscle of the chronic group were shallow and bulky. In the acute group, the myotendinous endings differed significantly in their structure from those of the chronic group. In atrophic muscle, the contact between muscle and tendon was reduced by quantitative and qualitative changes in the myotendinous endings. The B/P ratio allowed definition of three grades of myotendinous ending degeneration. Discussion: It is unclear whether degenerative changes induced by immobilization in muscle and, specifically, the MTJ are temporary and reversible or permanent. Conclusions: This preliminary study suggested a classification of ultrastructural MTJ changes into grade 0, reflecting a quite normal MTJ; grade 1, an intermediate process that might lead to irreversible atrophy or to recovery, spontaneously or with drug therapy; and grade 2, irreversible process with complete structural alteration.

Corresponding author: Luigi de Palma, Professor, MD, PhD, e-mail:

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Mariana Cevei, Elena Rosca, L. Liviu, Gabriela Mutiu, Dorina Stoicanescu, Liliana Vasile

Lumbar disk lesions in 47 cases were initially diagnosed using MRI investigation, then, after surgery, biological and histopathological aspects of intervertebral disks were revealed. Pieces from intervertebral disks were used for electron microscopy studies in order to determine collagen in the components of the intervertebral disk. The aim of the present study was to highlight the correspondence between the MRI aspect in cases with clinically manifest lumbar hernia, staged according to MRI Modic classification, and the histopathological aspect in patients with surgical interventions on the intervertebral disks. 4/5 of the analyzed disks had advanced forms of degenerescence of the intervertebral disks: hyalinized disk cartilage +/- intradiskal calcification or ossification zones, chronic inflammatory infiltrate at the disk cartilage level. Electron microscopy studies made on disk fragments obtained by discectomy revealed quantitative and qualitative changes of all types of collagen at the level of the three anatomical structures of the intervertebral disks, which correspond to the MRI changes.

Corresponding author: Mariana Cevei, Associate Professor, MD, PhD, e-mail:

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