Ultrasound-Guided Percutaneous Electrical Nerve Stimulation (PENS) as an Adjunct to a Multimodal Physical Therapy Program for Postoperative Shoulder Pain: A Randomized Clinical Trial

Background/Objectives: Arthroscopic shoulder surgery is associated with postoperative pain and loss of function. Percutaneous electrical nerve stimulation (PENS) may serve as an effective adjunct to postoperative rehabilitation. This randomized clinical trial examined whether adding ultrasound-guided PENS to a multimodal rehabilitation program improves pain, disability, pressure pain sensitivity, shoulder range of motion, and muscle strength in individuals with postoperative pain following shoulder arthroscopy. Methods: A randomized, parallel-group clinical trial (registry: NCT06331871) was conducted. Seventy patients who had undergone shoulder arthroscopy were randomized to receive manual therapy/exercise alone (n = 35) or manual therapy/exercise/PENS (n = 35). All participants received the multimodal program including manual therapy and exercises four weeks after surgery for a duration of 12 weeks (five sessions/week). Those allocated to the PENS group also received two sessions (once per week) of ultrasound-guided PENS targeting the suprascapular and axillary nerves. Pain intensity (Numeric Pain Rating Scale (NPRS)) and disability (Disabilities of the Arm, Shoulder and Hand (DASH)) were the primary outcomes, whereas function (Shoulder Pain and Disability Index (SPADI)), pressure pain threshold (PPT), isometric strength, and shoulder range of motion (ROM) were secondary outcomes. Pain, PPT, strength, and ROM were assessed before and after treatment, and at 1 and 3 months. Disability and function were assessed at baseline and 3 months after treatment. Results: Patients receiving PENS showed greater improvements in shoulder pain (F_{2.72, 182.32} = 7.76, p = 0.007, η²p = 0.10), disability (F_{1, 68} = 5.63, p = 0.020, η²p = 0.08), function (F_{1, 68} = 4.15, p = 0.046, η²p = 0.02) and PPT over the infraspinatus muscle (F_{3.20, 217.28} = 2.93, p = 0.032, η²p = 0.04) than those receiving manual therapy/exercise alone. No between-group differences were observed for PPT at the deltoid or tibialis anterior muscles. The PENS group also showed greater improvements in some, but not all, measures of shoulder strength and range of motion; however, the effect sizes were small and the clinical relevance of these differences remains uncertain. Conclusions: Adding ultrasound-guided PENS targeting the suprascapular and axillary nerves to a multimodal physical therapy program resulted in greater improvements in pain, disability, and shoulder-specific function, with limited additional benefits for some measures of strength and range of motion, compared with physical therapy alone, in individuals with postoperative shoulder pain. However, many of the lower-bound estimates of the 95% confidence interval did not surpass the minimal clinically important difference. Therefore, the clinical relevance of the results should be considered with caution.