Resection of up to 30% of the anterolateral quadrant of the head-neck junction did not significantly alter the load-bearing capacity of the proximal part of the femur. However, a 30% resection significantly decreased the amount of energy required to produce a fracture. Thirty percent should be considered to be the greatest feasible amount of resection because of the change in the pattern of the femoral head-neck response to axial loads that we observed.
Biomechanical testing was done on 15 matched pairs of central-third bone-patellar tendon-bone and double-looped semitendinosus-gracilis grafts harvested from 15 cadaveric knees. Load to failure, composite graft stiffness, and the modulus of elasticity were calculated for each graft. Specimens were from 2 female and 13 male donors (average age, 40 years; range, 17 to 53). Average load to failure for the patellar tendon grafts was 1784 N (+/- 580), compared with 2422 N (+/- 538) for the hamstring tendon grafts (significantly different). There was no statistically significant difference in stiffness between grafts (patellar tendon, 210 N/mm; hamstring tendon, 238 N/mm). The elastic modulus was 225 MPa (+/- 129) for the patellar tendon grafts and 145 MPa (+/- 58) for the hamstring tendon grafts (significantly different). The average cross-sectional area for the hamstring tendon grafts was 57 mm2, compared with the 45 mm2 for the patellar tendon grafts. The hamstring tendon grafts were significantly stronger than the matched central-third patellar tendon grafts, but the two grafts were similar in stiffness. The patellar tendon grafts had a higher modulus than the hamstring tendon grafts.
In this model of dorsally comminuted extra-articular distal radial fractures, dorsal pi-plate fixation demonstrated better resistance to fracture gap motion than did the four types of volar plate fixation. The AO volar locking and DVR plates conferred the greatest resistance to fracture gap motion among the four volar plates tested. Volar locking technology conferred a significant increase in resistance to fracture gap motion as compared with nonlocking plate technology.
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