Smoking was shown to have a negative effect on fusion and overall patient satisfaction, but no measurable influence on the functional outcome as assessed by the Dallas Pain Questionnaire.

Five categories of interacting factors that influenced symptoms of anxiety and depression both before and after surgery were identified: pain, lack of information, disability, return to work, and mental health. Information appears to have a regulating effect on anxiety and depression.

The long-term functional outcome of posterolateral spinal fusion improved significantly for boththose with and without pedicle screw instrumentation, with a global 70% satisfaction reported by the patients. Patients with isthmic spondylolisthesis Grades 1 and 2 with noninstrumented fusion had superior long-term outcomes after posterolateral spinal fusion in comparison with an instrumented fusion. In contrast, patients diagnosed as having primary degenerative instability improved significantly when the posterolateral fusion was supported by instrumentation. In actuality, pedicle screw instrumentation increased reoperation rate compared with noninstrumented posterolateral fusion.