Does the Sagittal Balance Influence Microsurgical Results for Spinal Stenosis? a prospective 4 years follow-up

Study Design: Retrospective Study Objective: Lumbar spinal stenosis (LSS) is known as one of the most frequent causes for spinal surgery. Since sagittal balance (SB) has drawn scientific attention in recent years, questions have been raised, whether there is a need to restore SB for best clinical outcome in every spinal surgery. This study evaluated the influence of SB on clinical outcome of patients with LSS in a long-term follow-up of more than 4 years. Summary of Background Data: Results of short-term follow-up did not show any association between clinical outcome and the degree of sagittal imbalance in patients with LSS, who received microsurgical decompression alone. Data concerning the long-term influence of sagittal balance are lacking. Methods: 136 patients were included and received a 1-year follow-up. 72 subjects underwent additional long-term follow up (51 months) . The patients received preoperative and follow-up long-standing spinal radiographs. Patients were assigned to one of three groups, according to their SB (normal-balance(NB), minor-loss-of-balance(miIB), major-loss-of-balance(maIB)). Clinical outcome parameters were determined by evaluating Roland-and-Morris-disability-questionnaire, Oswestry-Disability-Index, Odom’s-criteria, SF-36-score, visual-analogue-scales for pain and the walking distance. Results: Long-term follow-up showed a significant improvement of clinical outcome parameters independently of their sagittal balance(∆ODI_NB= -23,0±18,9; ∆ODI_miIB=- 26,9 ± 21,6; ∆ODI_maIB= -21,6±25,1). There was no significant difference between the three groups in pain, disability and quality-of-life. The miIB group benefitted most concerning walking distance. A relevant change concerning the sagittal balance was not detected at 4 years after surgery. Conclusions: SB does not influence the long-term clinical outcome in patients with symptomatic LSS after microsurgical decompression. Patients without obvious instability benefit significantly from microsurgery, regardless of their preoperative global sagittal balance. The initial pathological SB in patients with LSS appears to represent true structural changes of the spine, rather than a pseudo-imbalance due to a compensatory mechanism in order to relieve claudication.