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Ligament Healing Characteristics

See: - Biomechanics of ACL:

- Effects of Immobilization:
    - immobilization significantly decreases strength and energy-absorbing capacity of rabbit bone-ligament-bone preparations;
    - effect is most obvious at the ligament-bone junction;
           - under conditions of stress deprivation, there is increased osteoclastic activity at the junctional region of bone;
           - period of immobilization leads to increased likelihood that failure in response to strain would occur at this junction;
           - stress deprivation decreases strength in both the ligament and in the junction, and functional failure becomes more likely with increased immobilization;
    - effects of immobilization are reversible;
           - after immobilization junction regains its strength, although relatively slowly;
           - four to 12 months of recovery may be needed before junction recovers its normal biomechanical characteristics;

- Ligament Repair:
    - collagen synthesis and degradation proceed simultaneously, as in other types of wound healing, but collagen content increases;
           - initial collagen is type III, although later composition changes to predominantly type I collagen;
           - glycosaminoglycans also increase in the early phase of wound healing;
    - w/ remodeling & maturation, contents gradually return toward normal;
    - injured ligaments sometimes demonstrate the ability to contract or to "tighten up."
           - rat medial collateral ligaments Z-lengthened are able to contract to normal tightness in three weeks;
           - there is an assoc increase in the amount of actin as measured by immunofluorescent staining;
           - actin is same contractile protein found in thin filaments of muscle sarcomeres and in the cytoplasm of mobile cells

Attachment of autogenous tendon graft to cortical bone is better than to cancellous bone: a mechanical and histological study of MCL reconstruction in rabbits.