Robinson Risk Score for calculation of nonunion risk for displaced midshaft clavicle fractures. Needs 3 inputs:

1. Smoker (yes/no)
2. Comminution - i.e. presence of 3 or more fracture fragments (yes/no)
3. Absolute displacement (mm)

Logit(p) = -5.616 + (1.324 x [1 if smoker or 0 if nonsmoker]) + (0.561 x [1 if comminuted fracture or 0 if noncomminuted fracture]) + (0.153 x
absolute fracture displacement in millimeters).

Percentage probability of nonunion = exp(logit[p])/(1 + exp[logit(p)]) x 100.

Reference:
Risk Factors for Nonunion After Nonoperative
Treatment of Displaced Midshaft Fractures
of the Clavicle, I.R. Murray, C.J. Foster, A. Eros, C.M. Robinson. J Bone Joint Surg Am. 2013;95:1153-8