Predicting cubitus varus in supracondylar fractures of the humerus by Baumann's angles in post reduction X-rays.

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+/-1.67 yrs, 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+/-4.14 masculine. The mean normal side carrying angles (NSCA) were 9.56 +/- 2.2 masculine. The NSCA IQR (Inter Quartile Range) was 8.8-10 masculine. The ASBA was 79.9+/-9.1 masculine and affected side carrying angles (ASCA) was 0.20+/-8.7 masculine. 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 8.8 masculine (the lower limit of IQR for NSCA), a value >0 masculine 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<8.8 masculine (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.