Publication: Predicting cubitus varus in supracondylar fractures of the humerus by Baumann’s angles in post reduction X-rays
Date
2006
Journal Title
Journal ISSN
Volume Title
Publisher
Kathmandu University
Abstract
Objectives: The present study presents the technique to predict cubitus varus by post reduction Affected Side and
Normal Side Baumann’s angle difference (ASBA and NSBA) respectively. It intends to correlate the Baumann’s
angle to the final carrying angle of the injured elbow and presents the relevant mathematical clinical rule along with
its prediction test characteristics.
Material and Methods: Total 57 patients of 6.5±1.67yrs, 22 were males and 8 females with 19/30 having left side
injury. Isolated closed supracondylar fractures of humerus up to 5 days duration included and previous trauma,
pathological fracture, other injury, elbow disease were excluded .30/57 completed >1 year follow-up.
Results: The Mean NSBA was 74.4±4.14º. The mean normal side carrying angles (NSCA) were 9.56 ± 2.2º. The
NSCA IQR (Inter Quartile Range) was 8.8-10º. The ASBA was 79.9±9.1º and affected side carrying angles (ASCA)
was 0.20±8.7º. The ASCA was best predicted by the difference between ASBA-NSBA (ASCA=3.87-0.65(ASBA-
NSBA; F=15.91). At a cut off of 8.8º (the lower limit of IQR for NSCA), a value >0º for ASBA- NSBA was 80%
predictive of cubitus varus. With pre test probability of varus at 70%, sensitivity was 0.94 and specificity 0.42.
Discussion: A prediction rule to predict the final carrying angle from ASBA NSBA difference is presented with a
positive predictive value 0.80, specificity of 0.42, and sensitivity of 0.94 at a pre test probability of 0.70.When the
diagnosis of cubitus varus is ASCA<8.8º (Lower limit of the IQR for NSCA).
Conclusion: If affected side Baumann’s Angle – Normal Side Baumann’s Angle is equal to or greater than 0 then
there was 80% probability of having cubitus varus.
Key words: Supracondylar fractures of humerus, Baumann’s angle, Complications, Carrying angle, Cubitus Varus.