From the Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, and Minnesota Spine Center, Minneapolis, Minnesota.
Acknowledgment date: November 18, 1996.
First revision date: February 27, 1997.
Second revision date: April 7, 1997.
Acceptance date: April 7, 1997.
Device status category: 1.
Address reprint requests to: Robert B. Winter, MD; Minnesota Spine Foundation; 606-24th Avenue South, Suite 606; Minneapolis, MN 55454.