BACKGROUND

The plumb line (PL) is a common tool for assessing the sagittal curvatures of the spine, but its accuracy depends on the ability of the physician to use it correctly. This study aimed to present a fixed plumb line (FPL) no longer held by a physician but fixed to a support, evaluating the reliability in posture assessment, comparing it with PL in both adolescent with and without scoliosis.

METHODS

The study evaluated the sagittal distances of the spine using a PL and a FPL in 80 young adults aged between 28.7 ± 7.2 and 55 adolescents aged between 12.4 ± 2.3, with and without scoliosis. Two expert and two novice clinicians tested the patients to evaluate the intra-rater and inter-rater reliability of FPL. Each clinician assessed participants twice on the same day, with a predetermined time interval (>1 h) to reduce recall bias. Multi-factor multivariate analysis of variance and two-way analysis of variance assessed the statistical significance, while intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimum detectable change (MDC) validated FPL consistency.

RESULTS

FPL provided an ICC coefficient >0.90 for all the measures, while PL an average of 0.70. On AIS patients, PL and FPL showed a significant difference for C7  < 0.001 and T12  < 0.001. The measured parameters were sensitive to gender and age for the FPL, furthermore, the C7 and L3 measurements were statistically different between PL and FPL ( < 0.001). Intra-rater reliability results for FPL ranged from 0.94 to 0.98 across various parameters, while the SEM and MDC values underscore the valuable precision of the FPL with changes exceeding 1 cm being meaningful. These findings suggest that FPL could be a reliable and accurate tool for measuring sagittal distances of the spine in both scoliotic and non-scoliotic patients.