For decades, needling interventions have been performed based on manual palpation and anatomic knowledge. The increasing use of real-time ultrasonography in clinical practice has improved the accuracy and safety of needling techniques. Although currently ultrasound-guided procedures are routinely used for patellar tendon pathology, e.g., during percutaneous electrolysis, the accuracy of these procedures is still unknown. This study used a cadaveric model to compare and evaluate both the accuracy and safety of ultrasound-guided and palpation-guided needling techniques for the patellar tendon. A total of five physical therapists performed a series of 20 needle insertion task each (n = 100), 10 insertions based on manual palpation (n = 50) and 10 insertions guided with ultrasound (n = 50) to place a needle along the interface between the patellar tendon and Hoffa's fat pad. All procedures were performed on cryopreserved knee specimens. Distance to the targeted tissue, time of the procedure, accurate rate of insertions, number of passes, and unintentional punctured structures between both applications (with and without ultrasound guiding) were compared. The results revealed higher accuracy (100% vs. 80%), a lower distance from needle to the targeted tissue (0.25 ± 0.65 vs. 2.5 ± 1.9 mm), longer surface of contact with the needle (15.5 ± 6.65 vs. 4.7 ± 7.5 mm), and a lower frequency of patellar tendon puncture (16% vs. 52%, p < 0.001) with the ultrasound-guided procedure as opposed to palpation-guided one. Nevertheless, the ultrasound-guided procedure took longer (54.8 ± 26.8 vs. 23.75 ± 15.4 s) and required more passes (2.55 ± 1.9 vs. 1.5 ± 0.95) to be conducted than the palpation-guided procedure (all, p < 0.001). According to these findings, the accuracy of invasive procedures applied on the patellar tendon is higher when conducted with ultrasound guidance than when conducted just on manual palpation or anatomical landmark. These results suggest that ultrasound could improve the clinical application of invasive procedures at the fat-patellar tendon interface. Due to the anatomical features of the targeted tissue, some procedures require this precision, so the use of ultrasound is recommended.
Keywords: accuracy; knee; needle; palpation; patellar tendon; ultrasound.