Adolescent idiopathic scoliosis: is there a relationship between Risser staging and the proximal humerus ossification system?

Purpose: To evaluate whether there is a mismatch between Risser staging and the proximal humerus ossification system (PHOS); and to analyze the correlation in the skeletal maturity stages between the two humeral epiphyses.

Methods: Data from patients aged 10 to 18 years with adolescent idiopathic scoliosis (AIS) seen between 2018 to 2021 were analyzed. In an anteroposterior (AP) spine radiograph the ossification process was evaluated using the Risser classification method and bilateral PHOS (if both humeral epiphyses were visualized). A mismatch between methods was defined as a Risser 0-1 (relatively skeletally immature) with a PHOS 4-5 (skeletally mature), or a Risser 2-5 (relatively skeletally mature) with a PHOS 1-3 (skeletally immature). The McNemar test was used to calculate the significance of the mismatch.

Results: A mismatch between Risser and PHOS stages was observed in 28.5% of 105 patients, which was statistically significant (p < 0.001). Of the 49 patients with a Risser 0-1, 55.1% (n = 27) had a PHOS 4-5. None of the patients with a Risser 2-5 had a PHOS 1-3. In the 47 patients in whom both humeri were visualized, the absolute correlation between the left and right PHOS values was 95.7%.

Conclusion: Of AIS patients who are relatively skeletally immature according to Risser staging, more than half may be skeletally mature when measured with PHOS. In patients with a Risser 0-1, it is recommended to measure skeletal maturity in an AP spine radiograph using the PHOS method, which may more accurately guide treatment decision-making, without the need to visualize both humeral epiphyses in this radiographic projection.

Level of evidence: IV.