Patent ID: 8206394

Claim:
A spinal fixation system comprising: a spinal rod, a plurality of bone anchors, one or more of the bone anchors having a U-shaped channel for receiving the spinal rod therein and a set screw, the U-shaped channel defined by two spaced-apart arms, the set screw having an external thread engagable with an internal thread provided on the arms to secure the spinal rod in the U-shaped channel, a plurality of generally tubular screw extensions, each screw extension connectable to one of the bone anchors and having a central lumen extending from a proximal end to a distal end of the screw extension, the central lumen sized to receive instruments and implants therethrough, a reduction cap having a bore extending therethrough, an internally threaded driving element, and a mating element disposed on a distal end thereof and adapted to removably mate the cap to one of the screw extensions, a set screw driver comprising a drive shaft having a proximal end and terminating at a distal end sized and shaped to fit within a mating feature on the set screw of a bone anchor, an externally threaded collar positioned about the drive shaft and rotatable relative to the drive shaft, the collar engaging an axial stop on the drive shaft, the collar engagable with the internally threaded drive element of the reduction cap, and a handle comprising an inner shaft having a distal end configured to engage the proximal end of the driver shaft of the set screw driver, an outer shaft having a distal end configured to engage the threaded collar, and a clutch connecting the inner shaft to the outer shaft and permitting selective rotation of the inner shaft relative to the outer shaft, the clutch comprising a spring and a plurality of disc clutch members positioned about the outer shaft, the spring biasing the disc clutch members into contact with one another and into contact with the outer shaft, at least one disc clutch member rotating relative to an adjacent disc clutch member upon application of a torque to the outer shaft greater than a preselected torque value.