Background:Degenerative lumbar instabilities are one of the major reasons for low back pain, especially in elderly people.There is still controversy in the literature about the clinical outcome of instrumented monosegmental fusions compared to noninstrumented posterolateral fusions.Material/Methods:In this study we described the postoperative outcome of 33 patients who underwent posterolateral monosegmental spinal fusion:instrumented (17 patients)or noninstrumented (16 patients).All patients received the same instrumentation system.Medical history (considering daily activities,sports,social contacts and quality of life),clinical examination and radiological analysis served as evaluation parameters.Data were collected by a questionnaire based on the Oswestry Disability Score for low back pain.Results:86.6%of all subjects showed an improvement of postoperative health status. Although patients with fusion without internal fixation needed a reduced dose of postoperative analgesics compared to the monosegmental non-instrumented group,there were no statistical differences in patient-reported,clinical and radiographical outcome between the two groups.Conclusions:The results do not indicate a benefit in outcome from added instrumentation in elective lumbar fusions.This should be considered in each single case when a spinal fusion in the treatment of degenerative lumbar instability is indicated.

Keywords: Internal Fixators, Low Back Pain - surgery, Lumbosacral Region, Questionnaires, Spinal Diseases - surgery, Spinal Fusion - adverse effects