Trial of Neurostimulation and Blood Flow Restriction for PFPS in Active Duty

A high rate of ambulatory care visits has been observed for patellofemoral pain syndrome (PFPS) in active duty military personnel, posing a significant threat to military readiness. For 2016 and 2017, there were 998,149 ambulatory care visits by active duty service members for knee pain across all the military services. Persons with PFPS limit their activity and joint motion to decrease pain, but the inactivity hastens the disease process, loss of quadriceps muscle strength and joint instability. The resulting muscle weakness affects work performance, limiting mobility and impacting military deployment health. Ultimately this condition leads to disability and early discharge of otherwise healthy service members.
We have shown that self-managed neuromuscular electrical stimulation (NMES), a passive electrotherapy, when performed concurrently with active exercise reduced pain and improved muscle strength in PFPS. Blood flow restriction (BFR) training has been shown to be effective in quadriceps strengthening for those that cannot tolerate heavy resistance training, such as individuals with patellofemoral pain. Given that these approaches -- NMES, BFR and active exercise -- have been shown to confer measurable benefits, we propose to evaluate the use of a previously tested NMES with active exercise self-managed program and supplement it with BFR.
The overall objective of this project is to compare two self-managed treatment regimens for PFPS: (1) NMES-Exercise supplemented with high BFR at 80% limb occlusive pressure (LOP) and (2) NMES-Exercise augmented with a low percentage of BFR LOP at 20 mmHG (BFR-sham). Each of the two treatment arms will perform a fixed exercise protocol singularly and in combination with BFR-NMES, and NMES alone. The rationale for this study is that by limiting blood flow to an exercising limb using active and passive exercise is expected to significantly improve lower extremity muscle strength, mobility, quality of life (QOL), and pain.
Such outcomes will ultimately result in improved deployability, retention of military personnel, and decreased economic costs in this population. Our central hypothesis is that the combination of NMES-Exercise of the injured leg supplemented with BFR set at 80% LOP will show significantly greater improvements in muscle strength, mobility, pain, daily activity, and QOL than the NMES-Exercise with BFR set at a very low percentage of LOP at 20 mmHG. We propose a randomized controlled trial to assess these specific aims.

Specific Aims:
1. To determine whether self-managed NMES-Exercise program supplemented with a high BFR of 80% LOP (limb occlusion pressure) is significantly more efficacious than NMES-Exercise with low BFR LOP set at 20 mmHG (sham) in improving muscle strength of the lower extremity, daily physical activity, and mobility.
2. To determine whether NMES-Exercise with high LOP BFR therapy improves QOL and PFPS symptoms significantly more than NMES-Exercise with low LOP BFR.

After consent and baseline testing, we will randomly assign active duty male and female subjects, ages 18 to 45, (n=84) with PFPS to one of two groups. All groups will receive 9 weeks of at-home and in-clinic strength training comprising NMES-Exercise with low or high LOP BFR. Using the linear mixed effect method, we will build longitudinal regression models to assess group differences in outcome measures over the 9 weeks. Positive results could translate into accelerated rehabilitation, decreased symptoms, and lower medical costs with better patient outcomes.

Relevance
This military unique proposal seeks to identify feasible self-management strategies for military members with PFPS that will return them to duty as quickly as possible. The high rate of PFPS reflects the physical demands of military service, including demanding training programs, maintaining physical fitness, and activities associated with military operations. A self-managed NMES-Exercise-BFR strength training program for PFPS is safe, novel, and military-relevant and could contribute to evidence-based self-managed approaches that translate into proven treatment options in the theatre of operation.