Blood Flow Restriction Following ACL Reconstruction (BFR)

The main objective is to determine the impact of Blood Flow Restriction (BFR) therapy, in comparison to a standard rehabilitation protocol, on preventing atrophy, improving quadriceps strength and improving functional outcomes of patients recovering from ACL reconstruction. The investigators hypothesize that patients undergoing BFR therapy after ACL reconstruction surgery will have better functional outcomes than those undergoing normal rehabilitation without BFR therapy.

Recovery from anterior cruciate ligament (ACL) reconstruction involves early physical therapy to promote muscular development. Traditional training regimens are based on the concept that muscle growth is induced with high resistance exercises of at least 65-70% of 1-repetition maximum. Achieving a high resistance level can be challenging in the early post-surgical patient who may be limited by pain, muscle atrophy, diminished proprioception, and psychological factors. Increasing evidence has suggested that Blood Flow Restriction (BFR) in resistance training, while transmitting a decreased load (25-50% of 1-repetition maximum) across the surgical site, may provide an additional benefit of inducing muscular development similar to that of high intensity exercises . Augmenting exercises with BFR involves an external pressure cuff applied to the proximal portion of the extremity, which is inflated to a pressure that restricts venous outflow while allowing arterial inflow to continue. This creates a physiologic environment for the patient to gain the hypertrophic effect of high resistance training, though at a lower and safer intensity. Studies suggest that BFR stimulates muscular development through an increase in metabolic stress, muscle fiber recruitment, cell swelling, and protein synthesis.

This group will undergo physical therapy exercises per the standard of care, with the addition of Blood Flow Restriction (BFR) utilizing a wide pressure cuff. BFR exercises will be initiated two weeks post-op, and continued for 16 weeks.

This group of patients will undergo physical therapy exercises per the current standard of care after their ACL reconstruction without BFR

A wide pressure cuff will be applied to the upper thigh prior to starting strengthening exercises. The cuff is inflated to 80% of resting systolic blood pressure. The cuff remains inflated for the entirety of the exercise (4 sets of a specific movement). Once the exercises are completed, it is deflated for a minimum of one minute before the next type of exercises are started.

The International Knee Documentation Committee (IKDC Questionnaire) is a knee-specific patient-reported outcome measure. The IKDC Questionnaire is a subjective scale that provides patients with an overall function score. The questionnaire looks at 3 categories: symptoms, sports activity, and knee function. Scores are obtained by summing the individual items, then transforming the crude total to a scaled number that ranges from 0 to 100. This final number is interpreted as a measure of function with higher scores representing higher levels of function.

The visual analog scale (VAS) is a validated, subjective measure for acute and chronic pain. Scores are recorded by making a handwritten mark on a 10-cm line that represents a continuum between "no pain" and "worst pain," with "no pain" corresponding to a VAS score of 0 and "worst pain" corresponding to a VAS score of 10.

We will measure quadriceps tendon strength (closed chain) strength using a hand-held dynamometer placed just distal to the knee joint on the posterior calf with the patient in the supine position. The outcome will be reported biweekly as a percentage of the strength of the contralateral side, and then finally reported as a change in strength from the first measurement to the final measurement. The results reported in this data table refer to the percent strength of the operated leg when compared to the contralateral side. The change in strength results can be found in the statistical analysis section.

A tape measure will be used to measure the thigh circumference 15 cm proximal to the superior pole of the patella. The outcome will be reported biweekly as a percentage of the contralateral side, and then finally reported as a change in circumference from the first measurement to the final measurement. The results reported in this data table refer to the percent circumference of the operated leg when compared to the contralateral side. The change in circumference results can be found in the statistical analysis section.

Tracked in the perioperative week and then from initiation of therapy 2 weeks post-op through 12 weeks post-op.

Degrees of knee flexion will be measured on the operative side by a licensed physical therapist. The outcome will be reported biweekly and then finally reported as a change in degrees from the first measurement to the final measurement. The results reported in this data table refer to the degrees of knee flexion at each reported time point. The change in knee flexion results can be found in the statistical analysis section.

Tracked in the perioperative week and then from initiation of therapy 2 weeks post-op through 12 weeks post-op.

Degrees of knee extension will be measured on the operative side by a licensed physical therapist, with zero degrees indicating the knee completely at extension and negative degrees indicating degrees of hyperextension. The outcome will be reported biweekly and then finally reported as a change in degrees from the first measurement to the final measurement. The results reported in this data table refer to the degrees of knee extension at each reported time point. The change in knee extension results can be found in the statistical analysis section.

Tracked in the perioperative week and then from initiation of therapy 2 weeks post-op through 12 weeks post-op.

Observation of any adverse events associated with BFR therapy, such as numbness, cuff-site pain, and bruising.

Inclusion Criteria: Age 13-35 years at the time of surgery Anterior Cruciate Ligament (ACL) reconstruction Using a physical therapy center with Blood Flow Restriction capabilities. Exclusion Criteria: Concomitant ligament reconstruction Concurrent procedures that require delayed weight bearing (ie: High Tibial Osteotomy (HTO), multi-ligament reconstruction, microfracture, etc) History of Deep Vein Thrombosis (DVT)/Pulmonary Embolism (PE) Immunocompromising conditions (ie: Rheumatoid arthritis, chronic steroid use, etc.) History of coagulation disorders or current use of anticoagulants Completion of physical therapy at a location not affiliated with the study Pregnancy

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