At least 20 subjects will be consecutively enrolled in this prospective pilot study from up to three (3) participating centers. Patients who, in the surgeon investigator's opinion, require lateral approach spinal fusion surgery at spinal level L4-5 (though may include any number of levels from L2 through L5), and have consented to XLIF surgery for their condition will be included. The following eligibility criteria are designed to identify existing clinic patients for whom study under this protocol is considered appropriate. All subjects must meet the inclusion/exclusion criteria below in order to be considered for enrollment.