Blood Flow Restriction Therapy After Anterior Cruciate Ligament Reconstruction.

Anterior cruciate ligament reconstruction (ACLR) rehabilitation necessitates restoration of quadriceps strength to minimize reinjury and optimize return to sport (RTS). Patients recovering from ACLR are limited by pain and activity restrictions, resulting in quadriceps muscle atrophy. Blood flow restriction (BFR) therapy involves performing exercises while a specialized blood pressure cuff is applied to the proximal aspect of the operative extremity and inflated to 40% to 90% of the arterial occlusion pressure, as determined using Doppler ultrasonography. BFR is theorized to induce an anaerobic environment and metabolic stress during exercise, promoting muscle hypertrophy and strength gains. Although the physiological mechanism has not been fully elucidated, it is theorized that BFR combined with low-load resistance training could yield muscle adaptations comparable to those of high-load resistance training. For ACLR patients with pain and restrictions precluding high-intensity strength training, incorporation of BFR into postoperative rehabilitation protocols could help mitigate quadriceps weakness and promote RTS. Randomized controlled trials report a prolonged, dose-dependent relation between BFR use and quadriceps and hamstring strength gains, improved bone and muscle mass, and earlier RTS, whereas other studies report no significant difference in quadriceps size, strength, or patient satisfaction compared with controls. Furthermore, although generally considered safe, there are rare reports of associated adverse events such as rhabdomyolysis, and BFR should be avoided in patients with a history of thromboembolic disease or peripheral vasculopathy. The literature examining BFR after ACLR is heterogeneous; lacks standardization; and contains broad variation in reported cuff pressures, as well as timing and duration of BFR use, among protocols. Although the use of BFR after ACLR shows promise, further study is necessary to elucidate the efficacy, safety, and optimal protocols.