Aims. The aim of this study was to analyse human muscle tissue before
and after rotator cuff repair to look for evidence of regeneration,
and to characterise the changes seen in the type of muscle fibre. Patients and Methods. Patients were assessed pre-operatively and one year post-operatively
using the Oxford Shoulder Score (OSS) and MRI. The cross-sectional
area and distribution of the type of muscle fibre were assessed
on biopsies, which were taken at surgery and one year post-operatively.
Paired samples from eight patients were analysed. There were three
men and five women with a mean age of 63 years (50 to 73). Results. All but one patient showed improvement in OSS (p = 0.004). The
mean increase in the cross-sectional area of the muscle was 1220 μm. 2. (-801
to 3712; p = 0.03). There was a reduction of type 2a fibres (p =
0.02). A clear relationship could not be seen between the MRI findings and
the histological appearances. Conclusion. This is the first study to provide evidence that atrophy of the
supraspinatus muscle is reversible. Changes in the types of fibre
are discussed. MRI assessment of muscle atrophy may not be fully
representative of
The nervous system is known to be involved in inflammation and repair. We aimed to determine the effect of physical activity on the healing of a muscle injury and to examine the pattern of innervation. Using a drop-ball technique, a contusion was produced in the gastrocnemius in 20 rats. In ten the limb was immobilised in a plaster cast and the remaining ten had mobilisation on a running wheel. The muscle and the corresponding dorsal-root ganglia were studied by histological and immunohistochemical methods. In the mobilisation group, there was a significant reduction in lymphocytes (p = 0.016), macrophages (p = 0.008) and myotubules (p = 0.008) between three and 21 days. The formation of myotubules and the density of nerve fibres was significantly higher (both p = 0.016) compared with those in the immobilisation group at three days, while the density of CGRP-positive fibres was significantly lower (p = 0.016) after 21 days. Mobilisation after contusional injury to the muscle resulted in early and increased formation of myotubules, early nerve regeneration and progressive reduction in inflammation, suggesting that it promoted a better healing response.
