The Precision and Safety of Ultrasound-Guided versus Palpation-Guided Needle Placement on the Plantar Fascia and Flexor Digitorum Brevis Interface: An Anatomical Study

Abstract

Background: Evidence suggests the plantar fascia and its interphase with the flexor digitorum brevis muscle can play a relevant role in plantar heel pain. Needling interventions could offer an appropriate treatment strategy to addressing this interface. Objective: We compared the accuracy and safety of ultrasound-guided versus palpation-guided procedures for the proper targeting of the interface between the plantar fascia and the flexor digitorum brevis with a solid needle. Methods: A crossover cadaveric study was conducted. Five experienced therapists performed a series of 20 needle insertions each (n = 100 in total, 10 landmark-guided and 10 ultrasound-guided) on 10 anatomical samples. The therapists were instructed to accurately place the needle on the interface between the plantar fascia and the flexor digitorum brevis muscle. The distance of the tip of the needle to the identified target (accuracy), the surrounding sensitive structures targeted (safety), the time needed for the procedure, the number of needle passes, and the needle length outside the skin were assessed. Results: The ultrasound-guided technique was associated with a significantly higher accuracy (p < 0.001) but without differences in safety (p = 0.249) as compared to the palpation-guided procedure. Conclusion: Our results suggest that ultrasound-guided insertion exhibits greater accuracy but not greater safety than palpation-guided insertion when targeting the interface between the plantar fascia and the flexor digitorum brevis.