R. Leggon et al., THE HOLDING STRENGTH OF CANNULATED SCREWS COMPARED WITH SOLID CORE SCREWS IN CORTICAL AND CANCELLOUS BONE, Journal of orthopaedic trauma, 7(5), 1993, pp. 450-457
The comparative holding strength of cannulated screws (CS) versus soli
d core screws (SCS) has not been reported, although differences exist
in the respective diameters of their outer thread and pilot drill hole
s. Our objectives were to characterize these differences and determine
the holding power of CS compared with SCS in cortical and cancellous
bone. The dimensions of the Synthes (Paoli, PA) 3.5-mm SCS, 3.5-mm CS,
6.5-mm SCS, and 7.0-mm CS were measured, and the cross-sectional area
for thread purchase was calculated. Using adult canine femurs, small-
fragment 3.5-mm SCS were inserted in cortical (midshaft) and cancellou
s (condyle) bone of one limb, and CS were placed in similar locations
in the contralateral limb. The same technique was used for large-fragm
ent CS and SCS. Pull-out testing was performed using an MTS machine (M
TS Systems, Minneapolis, MN) with axial loads applied at 5 mm/s, and d
ata were analyzed to determine the effects of screw type, location, an
d size. Differences in CS versus SCS design result in higher cross-sec
tional areas available for SCS thread purchase. Yet no significant dif
ferences exists between screw types (SCS vs. CS) in either cortical or
cancellous bone. In cancellous bone, large-fragment screws required m
ore force to pull out than did small screws (p = 0.000). The mean forc
e required to pull out small-fragment screws was higher in cortical bo
ne than in cancellous bone (p = 0.000). These data suggest that the cl
inical decision to use CS versus SCS should not be based on pull-out s
trength.