Reliability and Consistency Analysis of Multiple Instruments for Scoliosis Screening in Adolescent Males: A...

The cause of adolescent idiopathic scoliosis (AIS) remains unknown, largely relies on Angle of Trunk Rotation (ATR) measurements via the validated Bunnell Scoliometer™. While low-cost, non-standard plastic inclinometers are increasingly utilized, their diagnostic accuracy remains uncertain. This lack of standardization may lead to inconsistent results and patient misclassification, necessitating a systematic comparison of these devices against a reference standard. This study evaluates the reliability and diagnostic consistency of four commercially available instruments against the Bunnell Scoliometer™ - the established gold standard - to determine their clinical utility in scoliosis screening.

Data were collected from a sample of 64 male adolescents. The ATR was measured at four anatomical spinal levels: upper thoracic (T4), mid-thoracic (T7), thoracolumbar (TL), and lumbar (L3). Five different instruments were used for each measurement, with Bunnell ScoliometerTM (#1) serving as the gold standard. A total of 256 measurement points 512 measurements were recorded by two professional individuals. Pearson correlation coefficients (r) were utilized to quantify the relationship between the standard and the test instrument.

The analysis revealed varying levels of agreement with the standard. Instrument 3 demonstrated the highest reliability (r = 0.92, p < 0.05), followed by Instrument 4 (r = 0.89, p< 0.01) and 5 (r = 0.81, p < 0.01), that showed a moderate correlation, while Instrument 2 exhibited the lowest consistency with the standard (r = 0.51, p < 0.01).

The observed performance variance - most notably the high reliability of Instrument 3 compared to the poor reliability of Instrument 2 - underscores the clinical risks inherent in unvalidated screening tools. These discrepancies are likely rooted in inconsistent manufacturing standards. While Instrument 3 (Baseline Scoliosis Meter), like the Bunnell Scoliometer™, is an FDA and CE-certified Class I medical device subject to strict regulatory oversight, many market alternatives lack such rigor. In these unvalidated devices, internal mechanical factors - such as the viscosity of the damping fluid, the mass and balance of the indicator ball, and the granularity of the printed scale - can vary significantly, leading to measurement drift.

To ensure the integrity of AIS screen, the use of unvalidated devices should be avoided in professional clinical settings. Manufacturing inconsistencies and a lack of quality control directly compromise diagnostic accuracy and patient outcomes.