THE EFFECTS OF FUSION AND NON FUSION METHODS: ON THE SAGITTAL LUMBAR PROFILE AND THE DEVELOPMENT OF ASD

Abstract

Background: Abnormal sagittal plane configuration should be considered as one of the risk factors contributing to development of ASD.

Study design: Retrospective comparative randomised radiologic and clinical study.

Purpose: To analyse the relationship between sagittal plane configuration of the lumbosacral spine in comparison with rigid versus dynamic instrumentation and TDR and ASD.

Material: Study compared 4 groups of patients, who underwent primary monosegmental surgery for spondy-lolisthesis (Group A and B) or DDD (Group C and B) in lumbar spine between 1990–2005. Group A included 35 patients with ASD after 360° fusion, Group B 69 patients with 360° fusion without ASD, Group C 30 patients with dynamic instrumentation and Group D 35 patients with TDR both without ASD. The mean ages of the patients of the groups were 46.5/43.6/47.4/42.3 years respectively, the mean follow-up were 8.3/6.4/3.8/4.2 years respectively. The mean follow-up period between original surgery and ASD in Group A was 3.6 years.

Radiographic evaluation parameters: lumbar lordosis (L1-S1), distal lordosis (L4-S1), sacral slope (SS), segmental lordosis resp. lumbosacral angle (SA) and slippage (S).

Cinical evaluation criteria: VAS and Oswestry disability index questionnaires.

Methods: All parameters were measured and compared in all spines pre- and post-operatively and at the last follow-up observation. The correlation and regresion analysis were used for statistical evaluation of angular characteristics.

Results: Statistically significant correlations at the level of significance of α = 0.05 were found out between parameters: distal lordosis L4-S1 in Group A was smaller after surgery (−39.53°) than in Group C (−44.17°) and D (−52.21°) respectively, but not in Group B (−40.98°). Slippage S and segmental lordosis SA were decreased after surgery in Group A and B from 23.69% /26.11% and −14.21°/−15.26° to 9.77% /7.89% and −15.71°/−18.91° respectively, and thereafter they were increased at the last follow-up/ASD to 12.73%/11.67% and −12.18°/−15.21° respectively. VAS -reported pain and Oswestry decreased in all groups post-operatively and increased in Group A with the ASD. No correlation was found between parameters L1-S1 and SS in any group.

Discussion and Conclusion: All three instrumentation almost equally after surgery maintained the global profile of the lumbosacral spine with significant clinical improvement. No difference was found out between segmental and global sagittal profile by 360° fusion with/without ASD. Further follow-up at long term is necessary in order to confirm the influence of decreased distal lordosis L4-S1 after 360° fusion to development of ASD in comparison with non-fusion methods.