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.

No abstract

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.

No abstract

In this study we evaluated methods to reduce the friction of an extrasynovial tendon under a pulley in vitro. The surface of canine peroneus longus (PL) tendons was modified with gelatin and/or hyaluronic acid (HA) under different conditions. The gliding resistance between treated or control tendons and the canine digital flexor pulley was measured during 500 cycles of simulated flexionlextension. After 500 cycles, the gliding resistance of normal PL tendon increased 10-fold (p < 0.05), while the gliding resistance of tendons coated with carbodiimide derivatized gelatin (cd-gelatin) or carbodiimide derivatized gelatidHA (cdgelatin-HA) did not increase significantly. The PL tendon treated with cd-gelatin-HA had a similar friction response during the repetitive motion as the intrasynovial flexor digitorum profundus (FDP) tendon. Scanning electron microscopy after 500 cycles of motion showed that the tendon surface in the group treated with cd-gelatin-HA appeared smoother than tendons in the other groups.

No abstract

Fracture of the lateral process of the talus is an injury unique to snowboarders and is of particular clinical relevance because it masquerades as an anterolateral ankle sprain and is difficult to detect on standard radiographic views. Misdiagnosis can lead to long-term morbidity in a young and active population, with ensuing severe degeneration of the subtalar joint. To date, the precise mechanism of injury has not been established, making it difficult to identify potential preventive strategies in equipment design or snowboarding technique. Fracture of the lateral process of the talus in snowboarders has been thought to result from pure dorsiflexion and inversion combined with axial loading. We hypothesized, however, that external rotation is a key component of the mechanism of injury. Ten cadaveric ankles were mounted on a materials testing machine in a position of fixed dorsiflexion and inversion. All ankles were loaded to failure axially, with or without combined external rotation. No fractures occurred after axial loading in dorsiflexion and inversion, but six of eight specimens sustained fractures of the lateral process of the talus when similarly loaded with external rotation added, supporting our hypothesis. Further study is needed to evaluate the relationship between various types of snowboarding equipment and fracture mechanism.