Clin Orthop Surg.  2025 Apr;17(2):258-266. 10.4055/cios24248.

Stiffness-Related Disability Following Surgical Correction for Adolescent Idiopathic Scoliosis: A Comparative Analysis According to the Lowest Instrumented Vertebra Level

• Park SJ
• Lee CS
• Kang DH
• Park JS

• KMID: 2565827
• DOI: http://doi.org/10.4055/cios24248

Abstract

Background
Extensive spinal fusion inevitably results in loss of mobility, which may induce stiffness-related disability (SRD) during activities of daily living. Few studies have examined SRD after surgical correction for adolescent idiopathic scoliosis (AIS). This study aimed to investigate SRD following surgical treatment in AIS patients particularly with respect to the lowest instrumented vertebra (LIV).
Methods
Patients who underwent surgical correction for AIS between 2014 and 2021 and were followed up for 2 years were included. The degree of SRD was evaluated using the Stiffness-Related Disability Index (SRDI), which consists of 4 categories, each containing 3 questions, giving a total of 12 components of the questionnaire. The SRDI scores were compared according to the LIV level. Correlation analysis was performed to examine the relationship between the SRDI and legacy health-related quality of life (HRQOL) measurements.
Results
This study included 174 patients (47 men and 127 women) with a mean age of 13.8 years. Among the 12 items of the SRDI, the scores of 9 items showed a significant increase after surgery. The total sum of the SRDI scores also significantly increased after surgery. Pearson correlation analysis showed that the SRDI scores were significantly correlated with Oswestry disability index, nearly all domains, and the total sum of Scoliosis Research Society-22 questionnaire, and 36-Item Short Form Survey. No differences in the SRDI score were found among cases with the LIV between T12 and L3. However, the SRDI scores of patients with LIV at L4 were significantly higher than those of patients with other LIV levels.
Conclusions
Various degrees of SRD occurred after spinal fusion for AIS. The SRDI was significantly correlated with the HRQOL measurements. The SRDI score was highest in patients with the LIV at L4 when compared to those with other LIV levels. Fusion can be safely extended to L3 without significantly increasing SRD.

Keyword

Adolescent idiopathic scoliosis; Spinal fusion; Stiffness-related disability; Stiffness-related disability index; Lowest instrumented vertebra