VSP stabilization of lumbar neoplasms: technical considerations and complications.

Variable screw placement (VSP) plates and pedicle screw fixation were used to stabilize eleven lumbar neoplasms. Blood loss and complications were comparable to other methods of posterior segmental fixation, although operative times were longer. Fewer levels were fused than for systems using sublaminar hooks or wires, with 8/11 patients treated with two level fixation. Four preoperatively irradiated patients experienced 43% of all complications and had 70% of the major complications. Wound infections occurred in 18%, vascular injuries in 18%, and transient neurologic deficits in 36% of our patients. Clinical pseudoarthroses developed in two patients, and tumor progression produced late instability in two patients with renal carcinoma. Thecal compression and late collapse led to therapeutic failure in four patients in 12-18 months. Fixation failure occurred in four patients, resulting from loosening of the plate on the screws in three patients, and breakage of a screw in one. Failure to adequately address anterior column disease was the primary cause of treatment failure in these patients. Proper seating of the plate on the pedicle screws is, likewise, crucial to construct stability and longevity. VSP instrumentation provides rigid fixation and allows more extensive tumor resection than traditional systems, while sparing vertebral motion segments. However, failure to address key technical and biomechanical principles may lead to serious complications.