Summary

Blood Flow Restriction after ACL Reconstruction Does Not Accelerate Quadriceps Strengthening

Abstract

Introduction

The use of blood flow restriction (BFR) therapy has gained popularity as an adjunct rehabilitation technique following anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to longitudinally evaluate the impact that BFR has on quadriceps strength following ACLR with quadriceps tendon (QT) autograft in comparison to traditional rehabilitation protocols.

Methods

Patients undergoing primary ACLR with QT autograft at a single institution were retrospectively reviewed. Included patients had a minimum of two isometric strength testing sessions via electromechanical dynamometer (Biodex). Obtained strength measures included peak knee extension torque of the operative extremity and knee extension ratio (KER), in which the ratio of peak knee extension torque of the operative extremity and nonoperative extremity were compared. Strength measures were compared between patients that received BFR during postoperative rehabilitation and patients that underwent traditional rehabilitation without BFR for up to three strength measurement sessions. Demographic and surgical factors including patient age at surgery, sex, BMI, level of competition, time from injury to surgery, time from surgery to strength measurement session, use of regional anesthesia, tourniquet time, and concomitant surgery were collected. Two group comparisons of continuous and categorical variables were analyzed by using Mann-Whitney U and chi-squared test, respectively. Statistical significance was set at 0.05.

Results

A total of 45 patients (26 female) in the BFR group and 36 patients (13 female) in the traditional rehabilitation group met inclusion criteria. Mean age of the entire cohort was 19.5 years. There were no statistically significant differences among demographic or surgical factors between BFR and traditional cohorts. Of patients receiving BFR therapy, the mean number of BFR treatments was 18 from surgery to first strength measurement, 8 between first and second strength measurements, and 9 between the second and third strength measurements. Peak knee extension torque was lower for the BFR (96 Nm) group than traditional (111 Nm) group at the first strength measurement session (p=0.03) but was similar between groups at the second (118 Nm vs 134 Nm, p=0.1) and third (138 Nm vs 130 Nm, p =0.39) strength measurement sessions. There was no difference among BFR and traditional groups in the change of knee extension peak torque or change in KER between testing sessions. KER was lower at the second strength measurement in the BFR group (0.81) compared to the traditional group (0.90, p=0.02), though no differences existed at the first or third strength measurements.

Conclusion

Sequential knee extension strength measurements following ACLR in a young patient cohort demonstrated improvements irrespective of BFR use. There were no differences in the change of strength measures between testing sessions when comparing BFR and traditional rehabilitation groups. Both groups demonstrated similar strength improvements over time, and BFR did not accelerate strength gains compared to traditional rehabilitation. However, as the BFR cohort had lower starting yet similar final strength measurements compared to the traditional rehabilitation cohort, a role for BFR over the long term in at risk patients cannot be excluded.