The Effects of Preoperative Blood Flow Restriction Training in Patients Undergoing ACL Reconstruction: A Pilot Randomized Control Trial

Quadriceps femoris (QF) muscle function is an integral factor in the rehabilitation and overall outcome after lower extremity injury or surgical intervention. Atrophy of this muscle group is a common finding in patients undergoing anterior cruciate ligament (ACL) reconstruction. This is due to the immobility prior to surgery, vascular ischemia caused by a tourniquet intra-operatively and inability to perform high load strength training in the early post-operative period. A deficit in QF muscle strength can result in excessive joint loading and be a contributing factor in the early onset of osteoarthritis of the knee. It should be noted that a loss of strength in this primary knee extensor mechanism muscle group can persist for up to 2 years after surgery. Thus, the reduction of QF atrophy and maintenance of strength during an intervention such as an ACL reconstruction has large implications for the overall post-operative outcome and natural history of the knee joint.

In order to combat the challenges of muscle atrophy for patients with an ACL injury, blood flow restriction (BFR) training has been shown to have beneficial effects in the post-operative period specifically. The process of using BFR therapy involves the application of an extremity tourniquet to occlude venous outflow and restrict arterial inflow. Thus, an anaerobic environment is created to promote muscle hypertrophy by having cells upregulate cell signalling, protein synthesis and ultimately myogenic proliferation. The use of BFR during lower extremity rehabilitation has shown that its simultaneous use with low load resistance training can have similar hypertrophic effects to isolated high load resistance training. This is ideal for patients who are initially unable to perform high intensity exercises shortly after an ACL reconstruction surgery, but are attempting to reduce overall QF atrophy.

However, the use of BFR in the pre-operative period has yet to be well established. Preconditioning with an ischemic environment may provide an effective way to reduce QF atrophy with low load exercises while awaiting surgery. Additionally, having a period of sensitization with anaerobic conditions prior to surgery, may provide some resistance to the damaging effects of a tourniquet intra-operatively. The limited studies that have attempted to use BFR therapy prior to ACL surgery have had short intervention periods, small sample sizes and outcome variables that have not assessed overall clinical outcome. If BFR in the pre-operative setting can be shown to provide beneficial effects, it will be a valuable tool in maximizing the overall outcome of patients undergoing ACL reconstruction.

This prospective feasibility study has been designed to assess pre-operative BFR in patients awaiting ACL reconstruction. This study will serve the following: (1) to determine if BFR improves strength testing prior to surgery and (2) to determine if BFR reduces QF muscle group atrophy prior to surgery. Additionally, preliminary results on pre-operative clinical and quality of life scores will be collected. If this study shows encouraging results, it will serve as a template for a more comprehensive randomized control trial.