Fig. 2.

Logistic regression analysis showing the relations between duration of symptoms before the operation and radiological prognosis. The line is the curve fit from logistic regression, and represents the probability of an unsatisfactory radiological prognosis with the duration of symptoms before the operation. If the duration of symptoms before the operation is 2.53 days, the patient has an unsatisfactory radiological prognosis in 25% of cases; 4.72 days, in 50% of cases; 6.9 days, in 75% of cases; and 13.84 days, in 99% of cases.