Pediatric Coding Alert

Question: Our pediatrician saw a patient and documented that the patient’s left femur and tibia are shorter than the right. Given that ICD-10 codes are for unequal limb length, my question is: which leg is unequal, the left or the right?

New Jersey Subscriber

Answer: Your question assumes that the shortness of the right leg is acquired rather than congenital, given that you refer to “unequal limb length,” which is the language used in M21.7- (Unequal limb length (acquired)). However, you do not say whether your pediatrician made that distinction, and how you code this depends on whether the shortness of the left femur and tibia is congenital or acquired.

If it is congenital, the code choice is easier, as the code descriptors for Q72.4 (Longitudinal reduction defect of femur) and Q72.5 (Longitudinal reduction defect of tibia) state that they are for “reduction defects.” So, for congenital defects, coding is as simple as adding laterality, which would lead you to:

• Q72.42 (Longitudinal reduction defect of left femur)
• Q72.52 (Longitudinal reduction defect of left tibia).

For acquired shortness of limb lengths, laterality is determined by following the note that accompanies ICD-10 code M21.7-, which states that “the site used should correspond to the shorter limb.” In this situation, this means that you should use the codes for the left femur and tibia:

• M21.752 (Unequal limb length (acquired), left femur)
• M21.762 (Unequal limb length (acquired), left tibia).