| 摘要 |
<p>A compression bone screw apparatus (10) includes an elongated cylindrical shaft member (23) with a first smaller diameter portion that is of generally uniform cylindrical configuration, and a second enlarged diameter annular proximate end portion (27). An internal bore (28) extends longitudinally along the length of the shaft member (23), being open ended so that a driver tool (19) can extend through the elongated cylindrical shaft member (23) during installation of the compression bone screw apparatus (10). A generally cylindrical lag screw member (30) is slidably mounted in telescoping fashion upon the shaft member (23) at a position spaced from the annular proximate end portion (20) thereof. Splines prevent rotation of the shaft (23) with respect to the lag (30) as the lag (30) slides upon the shaft (23) to increase the overall combined length of the assembled shaft and lag screw (10). Stops, preferably in the form of abutting shoulders (27,33) of the respective shaft (23) and lag (30) screw member abut when the apparatus (10) is fully extended so that continued threading of the lag (30) into a surgical opening (17,18) in bone (T) causes a compression load across a fracture (14). The small compressing load discourages disassembly of the apparatus (10) when subsidence occurs.</p> |
