BOOST- Blood Flow Restriction Therapy to Optimize Muscle Size and Strength in Recovery From Lower Limb Orthopaedic Trauma

Lower limb fractures constitute the largest burden of fracture care globally. It is well documented that major upper and lower extremity trauma results in significant disability, with a protracted trajectory of recovery. A large proportion of these fracture can require a period of immobilization or protected weight bearing for up to 12 weeks depending on the nature, location and treatment of the fracture. Loss of muscle bulk and functional strength can occur with immobilization and disuse in as early as five days, and is confounded by severity of injury. Rehabilitation of these patients is focused on regaining range of motion, muscle strength and return to function. Traditional regimens to increase muscle size require exercises to be performed at high loads and intensities, typically at 60%-70% of a person's one repetition maximum. Due to the prolonged period of weight bearing protection and/or immobilization, and the recovery from the traumatic injury itself, most patients are unable to engage in high intensity and load exercises. This limits their ability to improve muscle size and strength and in turn slows down their return to function.

Blood flow restriction therapy (BFRT) originated in the 1960s in Japan. However, this initial approach was wrought with poor safety and reliability. The implementation of the automatic pneumatic tourniquet in 1979 allowed for the pressure applied by the tourniquet to be reliably controlled and replicated. Since then, multiple studies have been done to improve upon the technique, with the main aims to identify the optimal occlusion pressure and extent of blood flow restriction.

Blood flow restriction works on the principle of restricting arterial inflow and occluding venous outflow from the chosen limb. The personalized aspect is drawn from the fact that the pressure applied is a pre-determined percentage of the patient's Limb Occlusion Pressure (LOP). LOP is defined as the minimum pressure required, at a specific time by a specific tourniquet cuff applied to a specific patient's limb at a specific location, to stop the flow of arterial blood into the limb distal to the cuff. Benefits have been shown with blood flow restriction at 40%-80% of the patient's LOP. Further, despite the relationship between blood flow and fracture healing, studies in upper limb fractures have demonstrated that the reduced blood flow does not have a detrimental effect on bony union.

Personalized blood flow restriction therapy (BFRT) can help achieve similar muscle growth by performing exercises at lower loads and intensities (20%-30%) of one repetition maximum. There is significant excitement around this concept in elective orthopaedics, and this treatment modality has been shown to be effective in rehabilitation from ACL reconstruction, total knee replacements, wrist fractures and Achilles tendon ruptures. Although what is known about recovery and long-term disability in lower extremity orthopaedic trauma patients makes them an obvious candidate for this, there is a lack of evidence for use in lower limb fractures. With this pilot study, the investigators hope to demonstrate the feasibility of conducting a larger RCT on this topic.

Hypotheses The investigators hypothesize that personalized BFRT will be tolerated by patients from 2 weeks post injury with increasing tolerance overtime. Personalized BFRT will demonstrate an increase in quadriceps muscle size and strength in the injured leg at 12 weeks following injury. The treatment effects of BFRT on lower extremity strength at 12 weeks in fracture patients will be used to inform the sample size calculation of a future definitive trial. The investigators further hypothesize that the proposed pilot trial will demonstrate feasibility of a future definitive trial.