This study is being conducted to determine the percentage of patients with solid spinal fusions after being treated with Osteocel Plus in a TLIF procedure. Due to the unique processing conditions, Osteocel Plus retains a high concentration of stem cells in conjunction with the allograft bone matrix, so it is hypothesized that the fusion rate with Osteocel Plus will be comparable to published data for autograft. The Osteocel product family has already been used in approximately 15,000 cases worldwide.