Substantial mismatch of skeletal maturity assessment between Risser sign and Simplified Skeletal Maturity Scale/Thumb Ossification Composite Index in patients with adolescent idiopathic scoliosis.

BACKGROUND

Recently, hand skeletal maturity systems such as the Simplified Skeletal Maturity Scale (SSMS) or Thumb Ossification Composite Index (TOCI) have been introduced to attempt to prospectively predict the occurrence of peak height velocity (PHV) in adolescents. This study aims to compare the frequency of the mismatch in estimation of HV between Risser sign (RS) and SSMS/TOCI stages in adolescent idiopathic scoliosis (AIS) patients.

METHODS

One hundred thirty-three female patients with AIS were included. The mean age of the patients was 13.1 years. A whole spine and hand X-rays were obtained to establish skeletal maturity stage according to RS, SSMS, and TOCI systems. A mismatch resulting in overestimation (MOE) with RS compared to SSMS/TOCI was defined as the combination of RS 3-4/SSMS 3-5 or RS 3-4/TOCI 4-6, whereas a mismatch resulting in underestimation (MUE) with RS and SSMS/TOCI was defined as RS 0-1/SSMS 6-8 or RS 0-1/TOCI 7-8. Height velocity (HV) was compared between MOE/non-MOE and MUE/non-MUE groups.

RESULTS

Between RS and SSMS, the rates of the MOE and MUE groups were 4.3% and 1.7%, respectively. Between RS and TOCI, rates were 2.8% and 1.7%, respectively. With the combination of RS and SSMS stages, an estimate of HV of 5.6 cm/year in the MOE group was significantly larger than that of 2.7 cm/year in the non-MOE group, and 3.7 cm/year in the MUE group was significantly smaller than 6.9 cm/year in the non-MUE group. Likewise, with the combination of RS and TOCI stages, an estimate of HV of 5.8 cm/year in the MOE group was significantly greater that of 2.7 cm/year in the non-MOE group, and 3.7 cm/year in the MUE group was significantly smaller than 6.9 cm/year in the non-MUE group.

CONCLUSIONS

These findings support the use of SSMS/TOCI as the standard for assessing HV and skeletal maturity in patients with AIS.