Weight-based determination of spinal canal depth for paediatric lumbar punctures

Abstract

Objectives: The aim of this study was to evaluate whether spinal canal depth (SCD), measured using ultrasound, could be estimated from simple body measurements in a sample of children.

Methods: We measured SCD in a group of 225 children aged 0-18 years in the curved left lateral position using ultrasound. Statistical analysis was performed using Pearson's correlation coefficient at the 5% level of significance. We also performed linear regression analyses (analysis of variance) for mid-spinal canal depth (MSCD), including five potential predictors of age, gender, height, weight and body surface area, in each model.

Results: The mean MSCD was 33.0 mm (18.1-56.4) across the whole cohort. The best linear correlation of MSCD (mm) was found with weight (W; kg), approximating the formula MSCD=0.4W+20 (R(2)=0.72). Body weight accounted for 85% of the variance in the data (adjusted R(2)=0.72). Our formula gives values outside of the actual measured SCD range in 23/225 (10.2%) of cases and estimates MSCD at 24 mm at 10 kg, 32 mm at 30 kg and 40 mm at 50 kg.

Conclusions: We demonstrate a good correlation between weight and MSCD in a large group of children. Use of the simple formula MSCD (mm)=0.4 W+20 could improve the success rates of lumbar puncture in the paediatric population, but remains to be validated.

Keywords: General Paediatrics; Imaging; Measurement.