Blood Flow Restriction Therapy Preserves Whole Limb Bone and Muscle Following ACL Reconstruction

Abstract

Objectives: Patients often experience atrophy and bone loss immediately following anterior cruciate ligament (ACL) reconstruction. Rehabilitation (rehab) combined with blood flow restriction (BFR) therapy have been shown to mitigate muscle atrophy and reduce timelines for earlier return to function. Little is known about how BFR may impact bone loss. The objectives this study were to determine if BFR provides additional benefits when added to standard rehab in young active patients following ACL reconstruction with regards to preserving bone, recovering muscle, and regaining physical function. Methods: Fourteen active young adults (M=8, F=6; 23±7 yr; 170±10 cm, 75±14 kg) undergoing ACL repair via patellar tendon autograft were recruited, provided informed consent, and were randomized into two groups (CONTROL, n=7 & BFR, n=7) who performed 12wks of rehab beginning at 10 days post-surgery (2/wk). Both groups performed the same rehab protocol. However, during select exercises [quadriceps contractions wks1-3, bilateral leg press wk3-12, eccentric leg press wk4-12, hamstring curl wk4-6, eccentric hamstring curl wk7-12.], the BFR group exercised with 80% arterial limb occlusion using an automated tourniquet around the proximal thigh outfitted with Doppler (Delfi®). Exercise resistance was set at 20% of predicted 1-repetition maximum assessed in the contralateral limb. Exercises were performed for 4 sets of 30-15-15-15 repetitions separated by 30 s of rest. Functional assessments were performed at wk8 and wk12 post-surgery. Bone mineral density (BMD), bone mass, and lean muscle mass (LM) were measured using DEXA (Figure 1, GE®) at pre-surgery as well as wk6 and wk12 of rehab. Statistical Analysis: A 2(group) x 3(time) ANCOVA (co-varied on pre-surgery measures) was used to detect and compare changes in muscle and bone measures from pre-surgery at wk6 and wk12. A 2(group) x 2(time) ANOVA was used to detect and compare changes in functional outcomes tested at wk8 and wk12 between groups. Significant interactions were followed with a Tukey’s post hoc test for pairwise comparisons. Type I error was set at α=0.05. Results: Results are shown in Table 1. Both groups experienced similar decreases from pre-surgery measures in total LM at wk6 (p<0.05) with total lean mass in only the CONTROL group remaining diminished at wk12 (p<0.05). Whole leg LM in the injured limb was decreased in the CONTROL group, but not the BFR group, at both wk6 and wk12 (p<0.05). Thigh LM was found to be decreased in both groups at wk6 but to a greater extent in the CONTROL compared to the BFR group and remained decreased in only the CONTROL group at wk12. Whole leg bone mass was decreased in the control group at wk6 and in both groups wk12 (p<0.05). The CONTROL group was observed to have a decrease in BMD at the distal femur and proximal tibia as wk12 as well as the proximal fibula at wk6 and wk12 (p<0.05). Both groups demonstrated similar improvements in single leg squat distance, Y-balance, leg curl, and leg press from wk8 to wk12 of rehab (p<0.05). (Completed Data, N=32 anticipated by time of conference). Conclusion: In addition to recovering muscle to a greater extent than standard rehab alone, the addition of BFR to ACL rehab exercises appears to have a protective effect on bone. This effect also appears to not be limited to the site of cuff compression. Future studies are needed to examine the biochemical and mechanical mechanisms by which BFR may simultaneously act on bone and muscle. [Table: see text]