Acetabular Version Increases After Closure of the Triradiate Cartilage Complex

Area of Science:

• Orthopedics
• Radiology
• Developmental Biology

Background:

• The developmental origins of primary femoroacetabular impingement (FAI), especially pincer FAI, are not fully understood.
• Investigating acetabular growth patterns during skeletal maturation may reveal deviations contributing to FAI pathomorphologies.

Purpose of the Study:

• To assess changes in acetabular version, depth/width ratio, and femoral head coverage during skeletal maturation in healthy children.
• To compare these parameters between different stages of triradiate cartilage complex (TCC) closure using serial MRIs.

Main Methods:

• Prospective comparison of 129 MRIs from 65 asymptomatic children (mean age 12.7 years) with 1-year intervals.
• Hips were grouped based on TCC status: "open-open," "open-closed," and "closed-closed."
• Acetabular version, 3-D depth/width ratio, and 3-D femoral head coverage were measured and analyzed using ANOVA with Bonferroni correction.

Main Results:

• Acetabular version significantly increased in the "open-closed" group and in hips with a fused TCC compared to those with an open TCC.
• No significant changes in acetabular depth/width ratio or femoral head coverage were observed among groups or over time.
• Acetabular version changes were most pronounced near the time of TCC physeal closure.

Conclusions:

• Acetabular version increases with skeletal maturity, particularly around TCC closure, while depth/width ratio and head coverage remain stable.
• These acetabular orientation changes during a specific developmental window may be implicated in the etiology of pincer-type FAI.
• Further research with larger cohorts and longer follow-up is needed to confirm these findings and their clinical relevance.