Comparison of Chronological, Greulich-Pyle, and Modified Fels Skeletal Ages in Patients with Unilateral Infantile and Adolescent Blount Diseases.

Background: We sought to determine the relationship between Greulich and Pyle (G-P) and modified Fels (mFels) skeletal age in infantile and adolescent Blount diseases, where skeletal age (SA) is often advanced relative to chronological age (CA). We also sought to determine whether there was a difference between affected and unaffected extremity mFels SA in unilateral cases.

Methods: We reviewed databases of patients treated for subjects meeting inclusion criteria of unilateral infantile or adolescent Blount disease and concurrent interpretable hand and knee films. SA using the G-P atlas and of both knees by mFels method was compared with each other and CA.

Results: Twenty subjects with infantile Blount and 36 with adolescent Blount met inclusion criteria. Overall, there was no difference in mFels between affected and unaffected sides in either of these conditions (p = 0.6). SA was advanced by both methods in patients with both types of Blount disease, ranging from 5 to 18 months, depending on sex and diagnosis (p < 0.01). mFels was less advanced than G-P in both infantile and adolescent Blount diseases, but the differences were statistically significant only in boys with adolescent Blount disease (mean 10 months, p < 0.01).

Conclusions: Our study confirmed relatively advanced SA in patients with both forms of Blount disease. mFels SA was generally comparable in affected and unaffected extremities in these conditions. Given the epiphysial distortion typical of infantile Blount disease, comparability of affected/unaffected sides was an unexpected finding and should be validated by a larger cohort. Nevertheless, we recommend familiarization with and use of the mFels SA determination in these conditions.

Level of evidence: Level III, controlled case series. See Instructions for Authors for a complete description of levels of evidence.