Razavizadeh et al developed equations for estimating the depth of spinal needle insertion. The authors are from Kashan University of Medical Sciences in Iran.

Patient selection: 18 to 65 years of age



(1) weight in kilograms

(2) height in centimeters

(3) body mass index (BMI) in kg per square meter


needle depth in cm =

= (10.1 * (weight) / (height)) + 0.69


needle depth in cm =

= (0.18 * (BMI)) + 0.56

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