Volar plating of AO C3 distal radius fractures: biomechanical evaluation of locking screw and locking smooth peg configurations.

PURPOSE: The goal of this study was to determine whether locking screws or smooth locking pegs optimize fixation of AO C3 intra-articular distal radius fractures. A secondary goal was to determine which combinations of locking screws and smooth locking pegs influence construct stability. METHODS: In anatomic radius models, AO C3 intra-articular distal radius fractures were fixed using volar locking plates. For the first part, 16 specimens were randomized to receive either 2 locking screws or 2 smooth locking pegs in each of the 3 pairs of holes in the plate. For the second part, 30 specimens were randomized to receive any 4 combinations of locking screws and smooth locking pegs in each of the 3 pairs of holes. Axial loading to failure was applied. RESULTS: Constructs consisting of 4 smooth locking pegs within the lunate fragment were significantly weaker than constructs with 4 locking screws (means 626 N vs 981 N, respectively). Constructs with smooth locking pegs in the ulnar positions of the lunate fragment were weaker than with locking screws in these positions (means 737 N vs 977 N, respectively). Locking screws in the subchondral position of the lunate fragment were stronger than smooth locking pegs in these positions (means 1,227 N vs 934 N, respectively) and any other combination (means 1,227 N vs 942 N, respectively). CONCLUSIONS: Use of locking screws as opposed to smooth locking pegs for AO C3 intra-articular distal radius fractures, particularly subchondral and in the ulnar side of the lunate fragment, optimizes construct stability. This may have implications on postoperative rehabilitation protocols and may limit costs related to use of volar locking plates.

Nd:LiTaO(3) waveguide laser.

Waveguide lasers operating near 1092 and 1076 nm were fabricated in Z-cut Nd-Ti codiffused LiTaO(3). The Nd diffusion was at 14000 degrees C for 120 h. Samples from two wafers were examined. The Nd film starting thickness was 7 nm in wafer 1 and 15 nm in wafer 2. Ti stripes, 8-15 microm wide, were diffused at 1500 degrees C for 4 h for wafer 1 (130-nm stripe thickness) and 2 h forwafer 2 (100-nm stripe thickness). Pumping was at 750 nm. Threshold occurred at 330 mW of absorbedpump power for the best waveguides from wafer 1 and100 mW for the best waveguides from wafer 2. The slope efficiency of the latter was 0.07%.

Extended-cavity operation of rare-earth-doped glass waveguide lasers.

Channel waveguides fabricated in Nd-doped glass were used as gain elements for extended-cavity lasers. End-fire pumping was performed with a Ti:sapphire laser operating at 807 nm. The 4-nm FWHM output spectrum was centered near 1057 nm. Slope efficiencies were typically 4-11%, with thresholds near 20 mW. Active mode locking and Q switching were separately performed; mode-locked pulse widths were roughly 80 ps FWHM. Q-switched peak power was 1.2 W. The cw output narrowed to 7 GHz and tuned over a range of 24 nm when a grating provided feedback; single-frequency operation resulted when a high-reflectivity étalon was added.

Y-branch waveguide glass laser and amplifier.

A Y-branch channel waveguide laser operating near 1057 nm was fabricated by electric-field-assisted ion exchange in Nd-doped silicate glass. The overall length was 24 mm. Optical pumping was performed with a cw Ti:sapphire laser. Mirrors were bonded to the polished waveguide facets. The slope efficiency was 5.1% when a 4%-transmitting output coupler was used. Threshold was reached at 26-mW absorbed pump power. The device exhibited a single-pass small-signal gain of 0.034 dB/mW when operated as an amplifier. The 3-dB splitting loss of the Y-branch structure was overcome when the absorbed pump power was approximately 85 mW.

Integrated-optic laser fabricated by field-assisted ion exchange in neodymium-doped soda-lime-silicate glass.

A continuous-wave integrated-optic channel waveguide laser operating at 1.057 microm has been fabricated in neodymium-doped soda-lime-silicate laser glass. The device was end-fire pumped with the 0.528-microm line of an argon-ion laser. Threshold for laser action occurs for an absorbed pump power of 31 mW. The slope efficiency for the integrated-optic laser is estimated to be 0.5%. Field-assisted ion exchange in a eutectic melt of CaNO(3) and KNO(3) was used to form the waveguide.