The Journal of Bone and Joint Surgery, Vol 64, Issue 2 225-230, Copyright © 1982 by Journal of Bone and Joint Surgery, Inc
Isotopic evidence for resorption of soft tissues and bone in immobilized dogs
L Klein, JS Player, KG Heiple, E Bahniuk and VM Goldberg
Various experimental methods for producing bone and ligament atrophy have
yielded contradictory results. These methods include denervation,
immobilization (both internal and external), and disarticulation. We
studied a model of internal skeletal fixation for twelve weeks in dogs that
were chronically prelabeled with 3H-tetracycline, 45Ca, and 3H-proline.
Bone resorption was analyzed by the loss of 3H-tetracycline, and bone and
soft-tissue mass were analyzed by the radiochemical and chemical analysis
of calcium and collagen. The strength of the anterior cruciate ligament was
studied in tension to failure when a fast rate of deformation was applied.
Failure of the femur-ligament-tibia complex occurred through the insertion
of the ligament into the tibia for both the experimental and the control
limbs. Loss of collagen was greater in the tibia and femur than in the
lateral meniscus and anterior cruciate ligament, and correlated with a
mechanical failure via bone. No evidence for collagen replacement in
atrophied tissues was found, but one-half of the resorbed calcium was
conserved. The marked loss of 3H-tetracycline indicated that bone atrophy
was the result of increased resorption of bone rather than decreased bone
formation. Clinical Relevance: We have demonstrated significant atrophy of
the soft tissues (lateral meniscus and anterior cruciate ligament) as well
as of bone in immobilized joints of dogs. It is likely that the decrease in
strength of the bone-ligament-bone complex is related to this atrophy of
soft tissues and bone around the joint.
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