BFR Therapy After ACL Reconstruction

Patients will be randomized to either BFR therapy or no BFR therapy. Randomization will be carried out using block randomization with blocks of 6.

Those undergoing BFR therapy will have a Delfi Personalized Tourniquet System (PTS) cuff applied to the proximal thigh of their operative leg and inflated to 80% limb occlusive pressure (LOP) calculated by the Delfi PTS device during physical therapy (PT) sessions from day 2 after surgery through day 7 after surgery. Those in the no BFR group will have the Delfi PTS cuff applied to their proximal thigh with inflation of the tourniquet to minimal pressure only. BFR therapy will be administered by health care providers who have undergone training and certification for BFR therapy with the Delfi PTS device.

Both groups will undergo the following PT regimen two times daily beginning on the day after the surgical procedure and lasting for 6 weeks post-operatively:

• Quad sets = x1 min isometric hold, 30 sec off, 3 sets
• Terminal knee extensions = 3x15, 30 sec rest or short arc quads sitting 1 x 30 + 3 x 15, 30 sec rest
• Once range of motion (ROM) allows: Bike 10 mins, low to no resistance

Each physical therapy visit will last approximately 60 minutes. During that time, there will be a total estimated time of 5-7 minutes during which the tourniquet cuff will be on the thigh, and the tourniquet will be inflated for a similar time period. The tourniquet will inflate for about 1 minute in order to find out the specific pressure for the patient's leg and then will remain inflated until exercises are completed, which should take 4-6 minutes. The cuff will then be deflated and is removed from the leg within about 30 seconds of being deflated.

Patients will have MRI performed pre-operatively and at 6 weeks post-operatively with axial cuts to 50% femoral length above joint line. Quadriceps cross-sectional area will be measured by a blinded observer using MRI. Patients will have clinical measurements including thigh girth, Lachman test, knee joint range of motion, and knee joint swelling performed pre-operatively, at post-op day 1, post-op day 14, and 6 weeks post-operatively. All clinical measurements will be performed by a blinded observer. Additionally, patient reported pain level will be obtained at the same timepoints in which clinical measurements are performed using visual analog scale.

In order to ensure there are no nerve injuries present in patients prior to undergoing application and inflation of thigh tourniquet, all patients in the study will have single shot adductor and/or sciatic nerve blocks to ensure 24 hour period without nerve block prior to initiation of BFR therapy. Patients included in the study cannot have a nerve block lasting longer than the day of surgery. To ensure no new nerve deficits are present, the patients will undergo a physical examination during morning rounding on post-operative day 1 to assess for new nerve deficits.