Background: Low-load blood flow restriction (BFR) training has attracted attention as a potentially effective method of perioperative clinical rehabilitation for patients undergoing orthopaedic procedures. Purpose: To (1) compare the effectiveness of low-load BFR training in conjunction with a standard rehabilitation protocol, pre- and postoperatively, and non-BFR interventions in patients undergoing anterior cruciate ligament reconstruction (ACLR) and (2) evaluate protocols for implementing BFR perioperatively for patients undergoing ACLR. Study Design: Systematic review; Level of evidence, 2. Methods: A systematic review of the 3 medical literature databases was conducted to identify all level 1 and 2 clinical trials published since 1990 on BFR in patients undergoing ACLR. Patient demographics from included studies were pooled. Outcome data were documented, including muscle strength and size, and perceived pain and exertion. A descriptive analysis of outcomes from BFR and non-BFR interventions was performed. Results: A total of 6 studies (154 patients; 66.2% male; mean ± SD age, 24.2 ± 3.68 years) were included. Of these, 2 studies examined low-load BFR as a preoperative intervention, 1 of which observed a significant increase in muscle isometric endurance ( P = .014), surface electromyography of the vastus medialis ( P < .001), and muscle blood flow to the vastus lateralis at final follow-up ( P < .001) as compared with patients undergoing sham BFR. Four studies investigated low-load BFR as a postoperative intervention, and they observed significant benefits in muscle hypertrophy, as measured by cross-sectional area; strength, as measured by extensor torque; and subjective outcomes, as measured by subjective knee pain during session, over traditional low-load resistance training (all P < .05). BFR occlusion periods ranged from 3 to 5 minutes, with rest periods ranging from 45 seconds to 3 minutes. Conclusion: This systematic review found evidence on the topic of BFR rehabilitation after ACLR to be sparse and heterogeneous likely because of the relatively recent onset of its popularity. While a few authors have demonstrated the potential strength and hypertrophy benefits of perioperative BFR, future investigations with standardized outcomes, long-term follow-up, and more robust sample sizes are required to draw more definitive conclusions.

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Objectives: A growing number of investigations have demonstrated the negative impact of delaying treatment on clinical and radiographic outcomes in orthopedic surgery. However, the effect of delayed surgery on patient-reported outcomes (PROs) in those undergoing anterior cruciate ligament reconstruction (ACLR) remains unknown. The purpose of this study was to compare achievement of clinically significant outcomes (CSOs) in patients with greater than six months of time from injury to ACLR to those with less than or equal to six months of delay to surgery. Methods: A retrospective cohort study was performed to identify all patients undergoing primary ACLR between January 2017 and January 2018, with a minimum follow-up of one year. Patient demographics, comorbid medical conditions, and outcome scores on the International Knee Documentation Committee (IKDC) score and the Knee Injury and Osteoarthritis Outcomes (KOOS) Score were compared between patients with greater than six months from time of injury to ACLR and those with less than six months. CSOs were defined using minimal clinically important difference (MCID), patient acceptable symptomatic state (PASS), and substantial clinical benefit (SCB). Multivariate logistic regression was performed to produce odd ratios (OR) for outcome achievement and Weibull parametric survival analysis was performed to produce hazard ratios (HR) for relative time to outcome achievement. CSOs and time to CSOs at 1- and 2-year follow-ups were compared. Results: A total of 416 patients were included, with an average age of 34.7±14.4 years; 154 (37%) patients sustained ACL injury greater than six months prior to surgery. On multivariate analysis, these patients had significantly reduced likelihood to achieve the SCB on the KOOS Sport (OR: 0.2, 95% CI: 0.05-0.98, P = 0.04), PASS on the IKDC (OR: 0.58, 95% CI: 0.40-0.82, P = 0.03) and KOOS Pain (OR: 0.68, 95% CI: 0.49-0.93, P = 0.002) , as well as greater likelihood to undergo revision ACLR (OR: 8.99, 2.28-30.36, P < 0.001) at 1-year follow-up. At 2-years follow-up, patients with greater than 6 months of time from injury to ACLR> 6 months similarly experienced significantly reduced likelihood to achieve the PASS on the IKDC (OR: 0.15, 95% CI: 0.05-0.43, P < 0.001), KOOS Sport (OR: 0.38, 95% CI: 0.16-0.85, P = 0.02), KOOS Pain (OR: 0.31, 95% CI: 0.13-0.68, P = 0.012), KOOS Symptoms (OR: 0.32, 95% CI: 0.14-0.69, P = 0.004), KOOS activities of daily living (ADL) (OR: 0.05, 95% CI: 0.00-0.85, P = 0.04), and a greater likelihood to undergo revision ACLR (OR: 8.34, 95% CI: 3.51-11.4, P = 0.001). Finally, patients with delayed ACLR experienced delayed achievement of multiple CSOs on time-to-event analysis (HR: 1.55-6.48). No impact of surgical timing on achievement of the MCID was observed. Conclusion: Patients with greater than 6 months from time of injury to ACLR reported inferior PROM scores, reduced likelihood to achieve CSOs, and increased rates of revision surgery at 1-year and 2-years follow-up. These patients also reported significantly delayed achievement of CSOs. This information should be offered during preoperative counseling to illustrate the potential risk of delayed surgery in active patients with acute ACL rupture. [Table: see text][Table: see text][Table: see text]