Multi-threaded cannulated bone anchors

摘要

A cannulated bone anchor assembly includes a bone anchor, a receiver member for receiving a spinal fixation element to be coupled to the bone anchor, and a closure mechanism to fix the spinal fixation element with respect to the receiver member. The bone anchor includes a distal shaft having a first threaded section distal to a proximal head, a second threaded section distal to and adjacent the first threaded section, and a third threaded section distal to and adjacent the second threaded section. The first threaded section having a constant major and minor diameter. The second threaded section having a tapering major and minor diameter. The third threaded section having a tapering major diameter and a constant minor diameter.

主权项

1. A bone anchor assembly comprising:
a bone anchor having a proximal head and a distal shaft configured to engage bone, the distal shaft having a first threaded section distal to the proximal head, a second threaded section distal to and adjacent the first threaded section, and a third threaded section distal to and adjacent the second threaded section, the bone anchor including a central passage extending from the proximal head through the distal shaft,
the first threaded section having a first major diameter, a first minor diameter, and a first length, the first major diameter and the first minor diameter being constant over the first length of the first threaded section,the second threaded section having a second major diameter, a second minor diameter, and a second length, the second major diameter and the second minor diameter tapering in a proximal to distal direction over the second length of the second threaded section, the second major diameter and the second minor diameter being less than the first major diameter and the first minor diameter respectively over the second length of the second threaded section,the third threaded section having a third major diameter, a third minor diameter, and a third length, the third major diameter tapering in a proximal to distal direction over the third length of the third threaded section, the third major diameter being less than the second major diameter over the third length of the third threaded section, the third minor diameter being constant over the third length of the third section, the third minor diameter being equal to the second minor diameter at a transition from the second threaded section to the third threaded section, a receiver member for receiving a spinal fixation element to be coupled to the bone anchor, the receiver member having
a proximal end having a pair of spaced apart arms defining a recess therebetween,a distal end having a distal end surface defining an opening through which at least a portion of the bone anchor extends, and a closure mechanism positionable between and engaging the spaced apart arms to capture the spinal fixation element within the receiver member and fix the spinal fixation element with respect to the receiver member.