Massive atrophy of leg muscle after being immobilized in plaster casts following fracture

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In this first published research on human muscle atrophy consequent upon immobilization in plaster casts Professor Anthony J Sargeant demonstrated that gross anthropometric measurement of leg muscle size vastly underestimated the magnitude of the reduction in cross sectional area of the muscle fibres themselves. Needle biopsies of the quadriceps muscle in young military personnel who had simple leg fractures and had been immobilized in plaster casts for between 6-12 weeks showed that the muscle fibres were reduced by nearly 50% in cross sectional area. This reduction would lead to a concomitant reduction in the maximum force that the muscle could generate.Furthermore the study indicated that even with intensive residential rehabilitation the rebuilding of muscle fibre size was a very slow process. Indeed subsequent studies and observations suggest that full recovery of muscle fibre size may never be recovered in the injured legs in many people suffering leg injury and consequent immobilization. It appears that the time course of muscle loss and muscle gain is asymmetric with loss of muscle occurring rapidly, within days of immobilization, while recovery of muscle size takes many weeks.
Clinical Science and Molecular Medicine
Clin Sci Mol Med. 1977 Apr;52(4):337-42

1. Seven patients who had suffered unilateral leg fracture were studied after removal of immobilizing plaster casts.

2. Leg volume measured anthropometrically was reduced by 12% in the injured leg (5-68 +/- 1-05 litres) compared with the uninjured (6-43 +/- 0-87 litres). Associated with this loss was a similar reduction in the net maximum oxygen uptake achieved in one-leg cycling, from 1-89 +/- 0-21 1/min in the uninjured leg to 1-57 +/- 0-18 1/min in the injured.

3. Measured by a percutaneous needle biopsy technique, a reduction of 42% was found in the cross-sectional area of the muscle fibres sampled from the vastus lateralis of the injured compared with the uninjured leg.

4. Staining for myosin adenosine triphosphatase activity showed that both type I and II fibres were affected, being reduced respectively from 3410 to 1840 micronm2 and from 3810 to 2390 micronm2 cross-sectional area.

5. Possible reasons and implications are discussed for the discrepancy between the magnitude of the difference observed in the gross measurement of leg function (maximum oxygen uptake) and structure (leg volume) as compared with the cellular level (cross-sectional fibre area).

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