This is a pilot study designed to evaluate the effectiveness of TENS as part of post-operative pain management. Subjects receiving a TENS unit as part of clinical practice will be approached for consent and followed for 12 months.

Transcutaneous electrical nerve stimulation (TENS) is an affordable and non-invasive option for post-operative analgesia. Broadly, TENS devices deliver pulsed electrical impulses across skin to modulate pain. They are theorized to work through different mechanisms at multiple physiologic levels. Centrally, TENS units activate small-diameter sensory afferents (Aδ nerve fibers), which in turn activate descending pain-inhibitory networks. Peripherally, TENS activation of both large- and small-diameter sensory afferents blocks nociceptive signals to the brain and is instead perceived as TENS-induced paresthesias. Finally, TENS efficacy may also be mediated by µ-opioid, 5-hydroxytryptamine (HT)-1, and 5-HT-2 receptors, particularly at low-frequency electrical activity.2

There are inconclusive results for the adjunctive use of TENS to modulate pain, largely because of a relative paucity of high-quality trials and significant inter-study heterogeneity due to non-standardized protocols. Moreover, most studies within the orthopaedic literature have been concentrated primarily within the total knee arthroplasty (TKA) literature and may have limited generalizability to orthopaedic trauma patients. Some studies have shown a trend towards decreased opioid consumption with the adjunctive use of TENS (vs. placebo-TENS or standard care)3,4 while other studies have shown no difference in pain scores in the post-operative period.5-8 To the investigator's knowledge, only two recent randomized clinical trial (RCT)s have been conducted on non-TKA orthopaedic populations, both of which show promise for the use of TENS postoperatively. One prospective double-blind randomized trial on arthroscopic rotator cuff repairs found a 25% reduction in post-operative opioid consumption when TENS was used adjunctively for pain control .9 Another single-blind prospective RCT on Colles' fractures reported greater postoperative pain improvements in patients receiving TENS vs. placebo.10

There is a growing body of evidence to suggest that TENS therapy can reduce post-operative pain after orthopedic procedures. More high-quality studies are needed to strengthen this suggestion and to characterize specific protocols, populations, and orthopedic conditions for which it might work best. Transcutaneous electrical nerve stimulation, if shown to be effective, stands to serve as an affordable non-opioid, non-invasive option for the safe and effective treatment of pain in the orthopaedic trauma patient population.

TENS units are a non-significant risk device and, therefore, do not require an investigational device exemption (IDE) based upon FDA guidance.15-17 The sensor pads will be placed at the same time as the surgical fixation of the study injury. It does not present a potential serious risk to the health and welfare of patients.

Specific Aim 1: To pilot the use of TENS among a postoperative lower extremity injury population as part of multimodal pain management.

Null Hypothesis (H0): TENS cannot be delivered safely among this population. Alternative Hypothesis (HA): TENS can be delivered safely among this population.

Specific Aim 2: To compare utilization of inpatient and outpatient pain medications of patients treated with TENS and historical controls.

H0: Patients treated with TENS will require the same amount of opioids as historical controls.

HA: Patients treated with TENS will require less opioids (lower morphine milligram equivalent - MME) than historical controls during hospitalization and throughout 3-month follow up.

Specific Aim 3: To compare patient-reported outcomes of patients treated with TENS and historical controls.

H0 1: Patients treated with TENS will experience equivalent patient-reported outcomes as compared to historical controls.

HA 1: Patients treated with TENS will experience greater improvement in patient-reported outcomes (PROMIS 29) relative to baseline as compared to historical controls.

H0 2: Patients treated with TENS will report higher pain scores as compared to historical controls.

HA 2: Patients treated with TENS will report equivalent or lower pain scores as compared to historical controls.

This will be a prospective observational study of patients undergoing operative treatment of lower extremity conditions, including fracture fixation, treatment of nonunion, and deformity correction. The study will be conducted at a single Level I trauma center. Enrolled patients will receive TENS postoperatively during hospitalization; TENS units will also be sent home with patients for use throughout recovery. This group will be compared to controls injury-matched from a prospectively collected, historical database on mobility who did not receive treatment with TENS.

Inclusion Criteria:

• Operative treatment of lower extremity conditions, including fracture fixation, treatment of nonunion, and deformity correction
• Injury or deformity of the femur, tibia (plateau, shaft, pilon), or hindfoot and ankle
• Isolated injury
• Age 18 years or older
• Able to provide consent

Exclusion Criteria:

• • Unable to provide consent (no use of LAR)

This will be a prospective observational study of patients undergoing operative treatment of lower extremity conditions, including fracture fixation, treatment of nonunion, and deformity correction. The study will be conducted at a single Level I trauma center. Enrolled patients will receive TENS postoperatively during hospitalization; TENS units will also be sent home with patients for use throughout recovery. This group will be compared to controls injury-matched from a prospectively collected, historical database on mobility who did not receive treatment with TENS.