Coley et al, 2001, USA | Neonates and infants referred for image-guided LP after unsuccessful blind attempts. 32 patients enrolled | Prospective | Diagnosis of the cause of failed LP when failure has occurred and assessment on whether US can provide guidance for LP | 23 US studies showed intrathecal and/or epidural echogenic haematoma, 5 showed minimal fluid, and 4 had normal exams. US guidance used 26 times. US guidance provided usable samples in 15 of 26 attempts. In 11 encounters where thecal sac appeared normal with CSF visible, US was always successful. In 6 encounters where minimal or bloody CSF present, provided usable samples in 4 | Did not compare cause of failed LP found by US versus some other standard imaging study. Did not compare success of LP with US to fluoroscopy |
Ferre et al, 2007, USA | 76 patients were enrolled after exclusion criteria. A convenience sample of ED patients were used at an academic referral centre with an emergency medicine residency training programme | Prospective, observational trial | Two EPs sought to identify relevant anatomy in emergency patients. Visualisation time for 5 anatomical structures (spinous processes or laminae, ligamentum flavum, dura mater, epidural space, subarachnoid space), BMI, and perception of landmark palpation difficulty were recorded | Soft tissue and bony anatomical structures were identified in all subjects. Mean BMI was 31.4 F 9.8 (95% confidence interval 29.1 to 33.6). High-quality images were obtained in <1 min in 153 (87.9%) scans and in <5 min in 174 (100%) scans. Mean (SD) acquisition time was 57.19 (68.14) s; range 10–300 s | Data were obtained by 2 EPs who were working independently. There was no third party to check or verify data. Population was a convenience sample, not actual adults undergoing LP |
Stiffler et al, 2007, USA | The study enrolled a convenience sample of eligible patients at an ED. 62 patients were enrolled after exclusion criteria. | Prospective cross-sectional study | Calculated the BMIs of eligible patients and then categorised them as normal (BMI <24.9), overweight (BMI 24.9–30), or obese (BMI ⩾30). We recorded the difficulty in palpating traditional LP landmarks. Identification and measurement of the spatial relationships of the sacrum; spinous processes of lumbar vertebrae L3, L4, and L5; ligamentum flavum; and the spinal canal by US was attempted | Successful identification of pertinent structures (L4-L5 spinous processes and the spinal canal) occurred in 100% of patients with normal BMI, 95% of those who were overweight, and 74% of those who were obese. Difficulty in palpating landmarks was noted in 5% of patients with normal BMI, 33% of those who were overweight, and 68% of those who were obese. In subjects with difficult-to-palpate landmarks, US identified pertinent structures in 16 of 21. The average distance from skin to ligamentum flavum was 44 mm in those with normal BMI, 51 mm in those who were overweight, and 64 mm in those who were obese; measurements between spinous processes did not vary by BMI. Overall, there was a moderate correlation (0.62) between BMI and the distance from skin to ligamentum flavum | Population was a convenience sample of adult patients at the ED, not patients undergoing an actual LP. Data not reviewed nor verified by a third party |