'Disc degeneration in distal unfused segments: cause or consequence of adding-on after posterior fusion of lenke 3c, 5c, 6c adolescent idiopathic scoliosis?'.

BACKGROUND

The aim of this study is to examine the association between adding-on (AO) and disc degeneration(DD) of distal unfused levels in Lenke 3 C, 5 C, 6 C adolescent idiopathic scoliosis (AIS) patients with a follow-up of at least two years by comparing preoperative and postoperative magnetic resonance imaging (MRI).

METHODS

47 AIS patients (32 females and 15 males) with structural thoracolumbar/lumbar (TL/L) curves treated with long segment thoracolumbar fusion were retrospectively evaluated. Patients were divided into two groups according to the occurrence of the AO (AO and Non-AO groups). The unfused discs were graded using the MRI images according to the Pfirrmann grading method. The Scoliosis Research Society-22 (SRS-22) questionnaire and Visuel Analog Scale (VAS) were used to determine clinical outcomes.

RESULTS

The frequency of AO was found to be 29.78%. Postoperative total Pfirrmann score was significantly associated with AO. L5-S1 disc in the AO group had a statistically significant higher Pfirrmann grade than the Non-AO group. No significant association was found between the VAS and SRS-22 scores related to AO, DD or other radiological outcomes.

CONCLUSION

Although patients with AO demonstrated higher postoperative Pfirmann scores, no impact on clinical scores was observed. Furthermore, patients with AO developed significantly higher DD in L5-S1 disc, even if it is not the segment adjacent to the fusion. L5-S1 disc, which is already susceptible to degeneration, was further compromised in the presence of AO.