Feasibility of Distal Femur Intraosseous Access in Adult Trauma: An Evaluation of Needle Length

Rapid vascular access is essential in trauma resuscitation, with intraosseous (IO) access providing a reliable alternative when peripheral intravenous access is not feasible. While the proximal humerus, tibia, and sternum are food and drug administration -approved IO sites, the distal femur has been proposed as a potential alternative, particularly in out-of-hospital adult cardiac arrest scenarios. This study aims to assess the feasibility of distal femur IO access in adults by evaluating the required needle length.

A prospective observational case series study was conducted involving 100 healthy adult volunteers. Ultrasound was used to measure soft tissue depth 2 cm proximal to the superior border of the patella. Measurements were taken with the transducer placed lightly on the skin and with gentle downward pressure. Participants with a skin-to-bone depth greater than 40 mm were considered at high risk for insertion failure, as the longest standard IO needle measures 45 mm.

One hundred participants were enrolled, with a median age of 27.3 years (IQR 25.0-29.0); 64 (64.0%) were male. Body mass index ranged from 17.42 to 35.26 kg/m², with a median of 22.86 kg/m² (IQR 20.81-25.03). The mean soft tissue depth at the distal femur site was 25.0 mm (IQR 21.9-29.6) without pressure and 14.0 mm (IQR 12.0-16.0) with gentle pressure. No participant had a soft tissue depth exceeding 40 mm.

Distal femur IO access appears to be a feasible alternative for vascular access in young, non-obese adult patients. Our findings suggest that standard IO needle lengths are adequate for this site in this population, supporting its potential incorporation into emergency protocols. Further research is recommended to validate these results and inform standardized guidelines for distal femur IO placement.