Ma et al reported equations for estimating the length of a lumbar puncture needle to use for the L3-L4 interspace. The authors are from Taipei Medical University in Taiwan.

Patient selection: Taiwanese adults from 20 to 89 years of age



(1) weight in kilograms

(2) height in centimeters

(3) body mass index in kg per square meter


For males:


length of needle in cm =

= (0.182 * (BMI)) + 1.272


For females:


length of needle in cm =

= (0.067 * (body weight)) + 1.682


Other equation:


length of needle in cm =

= (0.1 * (weight) / (height in meters)) + 1.731

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