INTRODUCTION
Precise localization of the center of the reservoir access port (RAP) of intrathecal
pump is a crucial step to ensure a safe refill procedure. In difficult refill cases,
ultrasound guidance has been reported useful. Being more expensive and timeconsuming,
the purpose of the study was therefore to identify situations in which
sonographic localization is more accurate than the template method, in order to
restrict its use to these defined conditions.
MATERIALS AND METHODS
The RAP was localized using the template provided by the manufacturer and by
ultrasound guidance. The distance between the two points was measured. A
distance superior to 3.5 mm, corresponding to the radius of the silicone septum of the
RAP, was considered a clinically significant deviation.
RESULTS
During the study period, 22 patients underwent a total of 81 refill procedures. No
significant correlation was found between the distance between the two points and
age, height, weight, body mass index (BMI) or abdominal perimeter. The correlation
was significant between distance and pump’s depth. According to the ROC Curve,
the sensitivity of ultrasound identification of the RAP was 69.2% and the specificity
83.3% when the pump was implanted at a depth of 10 mm.
DISCUSSION
Our results are comparable to these published in the literature, pointing the
usefulness of ultrasound for refill of deeply implanted pumps. Our study provides an
additional element by specifying the depth from which the ultrasound seems to be
superior to template.
CONCLUSION
Poor accuracy in RAP identification of intrathecal pump can lead to life-threatening
complications. The results of our study suggest that the localization of recessed-RAP
can be improved by ultrasound in cases of pump implanted deeper than 10 mm. For
more superficially implanted devices, the template method seems to be as accurate
as ultrasound.