INJURY SIZE AFFECTS LONG-TERM STRENGTH OF THE RABBIT MEDIAL COLLATERAL LIGAMENT

Long term effects (104 weeks) of 2 extremes of gap size on the mechani cal behavior of the rabbit medial collateral ligament were examined, I n the midsubstance of each right medial collateral ligament, either an 8 mm gap injury was created or a 4 mm Z plasty injury was created and repaired, Each group was subdivided into a healing interval of 40, 78 , or 104 weeks, Femur-medial collateral ligament-tibia complexes were tested mechanically or examined with light microscopy, Both injuries h ealed with histologically similar tissue and showed improved mechanica l behavior 78 weeks after injury, No further improvement was measurabl e 104 weeks after injury, Scar material properties remained markedly i nferior to normal regardless of injury, Low load and viscoelastic beha vior recovered relatively well regardless of gap size, However, gap in juries showed significantly inferior structural properties at all inte rvals, These results suggest that a large initial gap between ligament ends in the extraarticular space predisposes scars to long term struc tural weakness. If this principle is true clinically, then patients wi th large gaps between torn ligament ends (caused by displacement, fold ing, or retraction) may function well at lower loads, but they may be chronically at greater risk of reinjury at high loads.