Lumbar Interbody Fusion Using the Telamon® Peek™ Versus the Telamon® Hydrosorb™ Fusion Device

Inclusion Criteria: * Both genders, age between 18 and 70 years * Chronic low back pain (\> 3 months) with or without leg pain but no signs of motor loss * Based on clinical history, physical examination, and radiographic signs, pain interpreted as emanating from L4-L5 or L5-S1 * Symptoms refractory to conservative treatment for at least 3 months * Evidence of degenerative changes at L4-L5 or L5-S1 (spondylosis) on plain radiographs and/or CT scan, and/or MRI. The pathology should be predominant on one level. * Single-level Posterior Lumbar Interbody Fusion surgery (PLIF) is indicated by the spine surgeon * Additional posterior fixation is mandatory * Use of autograft of the iliac crest is possible * Ability to provide informed consent Exclusion Criteria: * Previous lumbar spinal fusion * All other previous spinal surgery except for successful removal of a herniated disc more than 2 years before entering the study * Symptomatic degenerative disc disorder at more than one lumbar level * Pregnancy or intention to become pregnant during the two year study * Ongoing psychiatric illness * Evidence of alcohol and/or drug abuse * Inability to complete the questionnaires * Inability to walk independently * Other indications than degenerative spinal disorders including a metabolic bone disease, osteoporosis, infection, old fracture, inflammatory process, or neoplasm * Obvious painful and disabling arthritic hip joints