First Cranial Adjacent Segment Degeneration After Posterior Lumbar Fusion Fixation: A Mid-term Follow-up

Study Design.A retrospective study of 57 patients who underwent posterior lumbar interbody fusion(PLIF) at L4-S1 or L5S1.Objective.Long-term clinical and radiologic outcome measures were used to determine a lumbar fusion's contribution to degenerative changes in adjacent motion segments(ASD).To investigate the risk factors of adjacent motion segments(ASD).Methods.From January1998 to December 2002,57 patients who underwent lumbar fusion(PLIF) and have more than 6 years of follow-up were evaluated.Radiologic methods were used to evaluate the ASD on radiograph preoperative and last follow-up. The clinical outcome was evaluated by the Japanese Orthopedic Association(JOA) score and the association between clinical outcome and ASD was evaluated.Results.Radiological ASD occurred in 11 of the 57 patients(19.3%).Overall results in patients were good,the JOA score rose from an average of 11.5±3.8(preoperative) to24.2±4.2(postoperative) and 24.4±3.9(last follow-up),the recovery rate of the JOA score was72.5%±4.5%(postoperative) and73.7%±22.4%at last follow-up. Patients who left the degenerative adjacent segment unfused showed an significant(P＜0.05) higher risk for ASD than patients with the degenerative adjacent segment fused.Objective and subjective clinical results showed no differences between the two groups.Patients suffering from ASD showed a signifcant(P＜0.05) reduced sacral inclination and lumbar lordosis angles.Conclusions.Our results suggest that degenerative changes on MRI of the adjacent fusion segements,advanced age(＞60 years) may be risk factors for radiological ASD; Radiographic evidence of ASD does not necessarily correlate with a poor outcome.