PARTIAL LACERATIONS OF HUMAN DIGITAL FLEXOR TENDONS - A BIOMECHANICALANALYSIS

The biomechanical properties of human flexor tendons with partial lace rations have not been previously studied. To determine the loss of ten sile strength with varying degrees of partial laceration, tensile test s were performed on 2 matched groups of human cadaver flexor tendons: One group had 50% while the other had 75% transverse volar lacerations of the anteroposterior diameter. The mean failure load of the 50%-lac erated tendons was 93% higher than that of the 75%-lacerated tendons. The forces tolerated by the lacerated tendons before failure were also compared to those measured in vivo during physiologic loading. The br eaking loads of both 50%- and 75%-lacerated tendons far exceeded the i n vivo forces measured in human flexor tendons during unresisted activ e finger movement (up to 34 N). Further, the breaking loads of 50% lac erations was higher than the in vivo forces during resisted active fin ger movement (up to 117 N). This study demonstrates that the threshold load levels to rupture of 50% and 75% lacerations are higher than phy siologic load levels measured during active motion, suggesting that pa rtial flexor tendon lacerations of up to 75% can withstand in vivo for ces associated with active unresisted mobilization or the digital flex or tendon.