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.

Introduction. The influence of lumbar and lumbosacral fusion on adjacent moving segments has been the subject of a number of studies, which have shown the origin and progress of degenerative changes and instability brought about by alterations of kinematics and elasticity of the fused segment. Back pains which emerge later in the postoperative period may be the consequence of degeneration and instability in the adjacent segment to the said fusion. The fusion shifts the centre of rotation to the level adjacent to the fusion, which increases the pressure and pull on both the disk and joints. It can be supposed that the pull and attendant pains are in direct proportion to the rigidity of the spondylodesis that is more pronounced after anterior intersomatic fusion and less so after posterior. The development of hyperlordosis or kyphosis in the lumbar region is also a risk factor for adjacent segment failure.

Material and methods. The authors performed a retrospective analysis on a group of 91 patients with spondylolisthesis who had undergone PLIF technique with transpedicular fixation surgery and PLF.

A total of 10 (11%) of 91 patients developed symptomatic next segment desease at a previously asymptomatic level. Date were obtained in patients with next – segment failure based on X-rays studies, neurological assessment and sequential follow-up examinations. The aforementioned patients had a mean age of 42.8 years and the mean follow up period was 8.7 years after surgery. 7 cases were isthmic, 2 degenerative and 1 dysplastic spondylolisthesis.

Fusion in every case entailed the use of autologinous bone grafts, and with the PLIF technique cages, in 3 cases, dowels, in 6 cases, and autofibula in 1 case were used. The mean follow-up period between original surgery and next-segment failure was 3.8 years.

Results. In ten cases from the group there was evidence of instability or degeneration, instability in 3 cases (all above fusion) and degeneration in 7 cases (4 above and 3 below fusion) respectively.

All patients with instability in cranial adjacent segment underwent successfully additional surgery by using 360° fusion with instrumentation (ALIF).

Discussion. In X-rays conducted prior to surgery, signs of hypermobility were present in the cranial adjacent segment in one case. This hypermobility affected the rigidity of the fusion in the caudal segment, which accelerated the progress of instability and caused further surgery to be necessary.

The cause of instability could also be overloading of the spine, damage to the stability of ligament and bone structures sustained during the operation, or a combination of the above.