Blood Flow Restriction to Improve Muscle Strength After ACL Injury

Quadriceps muscle weakness is a common consequence following anterior cruciate ligament (ACL)
injury and reconstruction. Maximizing quadriceps strength following ACL injury is significant
as diminished quadriceps strength has been linked to the osteoarthritis that affects over 50%
of surgically reconstructed limbs. Given that knee joint health following ACL injury is
predicated on restoring quadriceps strength, identifying treatment approaches capable of
improving strength is paramount. Blood flow restriction training (BFRT) is a method whereby
oxygen to the muscle is intentionally reduced during exercise/rehabilitation and may lead to
more timely and substantial strength gains. In the proposed project, we will examine the
efficacy of BFRT in patients who have undergone ACL reconstruction and suffer from quadriceps
weakness. This project will have a randomized clinical trial design. Sixty patients that have
torn their ACL and plan to undergo surgical reconstruction will be randomized into one of
four groups: 1) eccentric exercise; 2) concentric exercise; 3) eccentric exercise with blood
flow restriction; or 4) concentric exercise with blood flow restriction. All patients
regardless of randomization assignment will also receive standard of care ACL rehabilitation.
Approximately 6 weeks after ACL reconstruction surgery, patients will begin to receive the
study interventions which will last for 8 weeks. The concentric exercise will be a leg press
exercise done on a conventional leg press machine, while the eccentric exercise will be a leg
press exercise done on a device designed to elicit eccentric muscle contractions. Patients
will train at 70% of their 1 repetition maximum and will complete 4 sets of 10 contractions
at each session (2 sessions/week). For patients randomized to the BFRT groups they will
complete the leg press exercise while blood flow the the quadriceps muscle is restricted with
a BFRT device (Delfi Personalized Tourniquet System for Blood Flow Restriction). We will
quantify our dependent variables prior to surgical reconstruction, 6 weeks post-operatively
(before study intervention starts), 14 weeks post-operatively (immediately after study
intervention ends), and time of physician discharge from rehabilitation (e.g. time medical
clearance for return to activity). The primary outcome is isokinetic quadriceps strength. We
hypothesize that patients who complete eccentric exercise along with blood flow restriction
training will realize the greatest gains in muscle strength.

The DELFI PTS Personalized Tourniquet system is exempt from premarket notification and is
therefore not subject to 510(k)

Inclusion Criteria:

1. suffered an acute, complete ACL rupture as confirmed by MRI

2. scheduled to undergo ACL reconstruction

3. scheduled to undergo ACL reconstruction with a surgeon affiliated with MedSport
(University of Michigan Orthopaedic Clinic)

4. willing to undergo rehabilitation through MedSport (University of Michigan Orthopaedic
Clinic) 5)) Willingness to participate in testing and follow-up as outlined in the
protocol

6) English-speaking

Exclusion Criteria:

1. inability to provide written informed consent (or assent)

2. female subjects who are pregnant or are planning to become pregnant during the study
timeframe

3. previous ACL injury

4. previous surgery to either knee

5. bony fracture accompanying ACL injury

6. chronic ACL injuries (for our study, this is defined as patient reporting to a
physician greater than 2 weeks after initial injury)

7. patients who experienced a knee dislocation

8. History of blood clots

9. Previous deep vein thrombosis

10. Use of estrogen or progestin contraceptive

11. History of cerebrovascular disease

12. History of peripheral vascular disease

13. History of Sickle Cell Anemia

14. History of chronic muscular disorder (e.g. fibromyalgia)

15. History of severe hypertension