Blood Flow Restriction Therapy Preserves Lower Extremity Bone and Muscle Mass After ACL Reconstruction

Abstract

Background: Muscle atrophy is common after an injury to the knee and anterior cruciate ligament reconstruction (ACLR). Blood flow restriction therapy (BFR) combined with low-load resistance exercise may help mitigate muscle loss and improve the overall condition of the lower extremity (LE).

Purpose: To determine whether BFR decreases the loss of LE lean mass (LM), bone mass, and bone mineral density (BMD) while improving function compared with standard rehabilitation after ACLR.

Study design: Randomized controlled clinical trial.

Methods: A total of 32 patients undergoing ACLR with bone-patellar tendon-bone autograft were randomized into 2 groups (CONTROL: N = 15 [male = 7, female = 8; age = 24.1 ± 7.2 years; body mass index [BMI] = 26.9 ± 5.3 kg/m2] and BFR: N = 17 [male = 12, female = 5; age = 28.1 ± 7.4 years; BMI = 25.2 ± 2.8 kg/m2]) and performed 12 weeks of postsurgery rehabilitation with an average follow-up of 2.3 ± 1.0 years. Both groups performed the same rehabilitation protocol. During select exercises, the BFR group exercised under 80% arterial occlusion of the postoperative limb (Delfi tourniquet system). BMD, bone mass, and LM were measured using DEXA (iDXA, GE) at presurgery, week 6, and week 12 of rehabilitation. Functional measures were recorded at week 8 and week 12. Return to sport (RTS) was defined as the timepoint at which ACLR-specific objective functional testing was passed at physical therapy. A group-by-time analysis of covariance followed by a Tukey's post hoc test were used to detect within- and between-group changes. Type I error; α = 0.05.

Results: Compared with presurgery, only the CONTROL group experienced decreases in LE-LM at week 6 (-0.61 ± 0.19 kg, -6.64 ± 1.86%; P < 0.01) and week 12 (-0.39 ± 0.15 kg, -4.67 ± 1.58%; P = 0.01) of rehabilitation. LE bone mass was decreased only in the CONTROL group at week 6 (-12.87 ± 3.02 g, -2.11 ± 0.47%; P < 0.01) and week 12 (-16.95 ± 4.32 g,-2.58 ± 0.64%; P < 0.01). Overall, loss of site-specific BMD was greater in the CONTROL group (P < 0.05). Only the CONTROL group experienced reductions in proximal tibia (-8.00 ± 1.10%; P < 0.01) and proximal fibula (-15.0±2.50%,P < 0.01) at week 12 compared with presurgery measures. There were no complications. Functional measures were similar between groups. RTS time was reduced in the BFR group (6.4 ± 0.3 months) compared with the CONTROL group (8.3 ± 0.5 months; P = 0.01).

Conclusion: After ACLR, BFR may decrease muscle and bone loss for up to 12 weeks postoperatively and may improve time to RTS with functional outcomes comparable with those of standard rehabilitation.

Keywords: ACL; anterior cruciate ligament; blood flow restriction; rehabilitation.

Figure 1.

CONSORT diagram. BFR, blood flow restriction therapy; Post-Op, postoperatively; Pre-Op, preoperatively; rehab, rehabilitation.

Figure 2.

Exercises and exercise progression chart. 1RM, 1-repetition maximum.

Figure 3.

Changes in site-specific bone mass after 6 and 12 weeks of rehabilitation. BFR, blood flow restriction therapy; CON, CONTROL. Data are presented as adjusted means ± 95% CI for site specific bone mineral density (BMD, g/cm2) measures in the injured limb before surgery (Pre-Op) and following 6 and 12 weeks of rehabilitation for the A) distal femur, B) proximal tibia, and C) proximal fibula. *,**Significant change from Pre-Op baseline within group at p < 0.05 and p < 0.01, respectively. #,##Significant difference between groups at the same measurement timepoint at p < 0.05 and p < 0.01, respectively.

Figure 4.

Changes in site-specific BMD after 6 and 12 weeks of rehabilitation. Data are presented as adjusted mean ± 95% CI for site-specific (BMD, g/cm²) measures in the injured limb before surgery (Pre-Op) and after 6 and 12 weeks of rehabilitation for the (a) distal femur, (b) proximal tibia, and (c) proximal fibula. *,**Significant change from Pre-Op baseline within group at P < 0.05 and P < 0.01, respectively. ^#,##Significant difference between groups at the same measurement timepoint at P < 0.05 and P < 0.01, respectively. BFR, blood flow restriction therapy; BMD, bone mineral density; CON, CONTROL.

Figure 5.

Changes in lower extremity lean mass after 6 and 12 weeks of rehabilitation. Data are presented as adjusted mean ± 95% CI for lean mass measures in the injured limb before surgery (Pre-Op) and after 6 and 12 weeks of rehabilitation for (a) whole limb lean mass and (b) thigh lean mass (kg, templated to distal 2/3 of the thigh for each patient). *, **Significant change from Pre-Op baseline within group at P < 0.05 and P < 0.01, respectively; ^#,##Significant difference between groups at the same measurement timepoint at P < 0.05 and P < 0.01, respectively. BFR, blood flow restriction therapy; CON, CONTROL.

Figure 6.

Return to sport. Data are presented as mean ± CI for time to RTS (months) as cleared by a physician. Frequencies of sport participation for each group are also shown. Patients not actively participating in an organized competitive sport but who regularly perform exercise training and play sports were classified as recreational athletes. BFR, blood flow restriction therapy; RTS, return to sport. *Significantly different from the BFR group at P < 0.05.