Cubitus varus after pediatric lateral condylar fracture: true or pseudo?

Purpose: Common complications of lateral condylar fractures are lateral condylar overgrowth, lateral bony spur and cubitus varus. Lateral condylar overgrowth or lateral bony spur may appear as cubitus varus on gross examination. Such gross cubitus varus without actual angulation is pseudo-cubitus varus, while a difference of more than 5° in varus angulation on X-ray is true cubitus varus. This study aimed to compare true and pseudo-cubitus varus.

Methods: One hundred ninety-two children treated for unilateral lateral condylar fracture with a follow-up period of over six months were included. The Baumann angle, humerus-elbow-wrist angle and interepicondylar width of both side were compared. More than 5° in varus angulation on X-ray was considered cubitus varus. Increase in interepicondylar width was considered lateral condylar overgrowth or a lateral bony spur. The risk factors that could predict the development of a true cubitus varus were analyzed.

Results: True cubitus varus was 32.8%, measured by Baumann angle and 29.2%, measured by humerus-elbow-wrist angle. A total of 94.8% of patients showed an increased interepicondylar width. The predicted cut-off value for 5° varus angulation on the Baumann angle was a 3.675 mm increase in interepicondylar width by ROC curve analysis. The risk of cubitus varus in stage 3, 4, and 5 fractures according to Song's classification was 2.88 times higher than that in stage 1 and 2 fractures on multivariable logistic regression analysis.

Conclusion: Pseudo-cubitus varus is more prevalent than true cubitus varus. A 3.7 mm increase in interepicondylar width could simply predict true cubitus varus. The risk of cubitus varus increased in Song's classification stages 3, 4, and 5.