BFR May Protect Against Bone Loss Following ACL
March 24, 2019
The potential effects of BFR on bone are not well established in the available research. Based on the physiological effects of BFR, it seems there are positive changes that would promote bone healing or increases in bone density. Karabulut et al. demonstrated a similar increase in Bone-Specific Alkaline Phosphatase (marker for osteoblast activity) with a BFR group at 20% 1RM compared to a heavy lifting group at 80% 1RM. Mouser (2019), Hunt (2013), and Patterson (2011) all demonstrated increases in capillarity with BFR which would increase the transport of osteoblast to the bone. Hewitt et al. (2005) demonstrated, in an animal model, that cyclical inflation and deflation of a cuff proximal to a fracture could promote bone healing. To date, none of the BFR studies looking directly at bone have been done on injured humans. Until now.
Last week, Dr Bradley Lambert, PhD and his colleagues from Houston Methodist presented their most recent and very intriguing work at American Academy of Orthopedic Surgeons in Las Vegas. They had individuals post ACL reconstruction perform exercises with Personalized Blood Flow Restriction or work-matched, standard of care exercise. As part of their trial, they assessed bone mineral density, bone mass, and lean muscle mass via DEXA scan.
The BFR group performed all of their exercises with 80% Limb Occlusion Pressure using a Delfi Personalized Tourniquet System starting 10 days after surgery 2x week up to 12 weeks. "The addition of BFR therapy to standard rehab exercises was found to prevent muscle mass loss in the whole leg and thigh in the post-operative limb compared to rehab alone. Intriguingly, the addition of BFR was also observed to minimize losses in bone mineral content and preserve bone density in the limb compared to standard rehab alone." What was equally fascinating was the large bone loss the control group suffered at 6 and 12 weeks after ACL surgery. This has not been well documented, that bone almost becomes osteopenic after surgery, and begs the question of the role this "bone dump" may play not only in graft incorporation but also in the cross-talk that is required between bone and muscle. Many important pathways to support muscle such as progenitor cells and HIF-1A to promote angiogenesis arise from the bone. Given that the bone is in a catabolic state up to 12-weeks after ACL surgery, and probably longer, may give insight into the difficulty for the muscle to fully recover and the slow incorporation of grafts. This is very impactful not only for young healthy patients undergoing surgery, but perhaps even more for the elderly total joint patient that may suffer even more bone attrition. It goes without saying that the application of PBFR after fractures may be supported even more after this study. In fact, we have the largest PBFR trial in the world currently enrolling patients after femur fractures. Link: https://clinicaltrials.gov/ct2/show/NCT02746458?te...
Dr Lambert and his colleagues are already planning multiple follow-up studies and we are excited to be collaborating with the Methodist team.
The study will be submitted for publication soon. You can find more information on this presentation in the press release from AOSSM:
Hewitt, John D., et al. “The Effect of Intermittent Pneumatic Compression on Fracture Healing.” Journal of Orthopaedic Trauma, vol. 19, no. 6, July 2005, pp. 371–76.
Hunt, Julie E. A., et al. “Time Course of Regional Vascular Adaptations to Low Load Resistance Training with Blood Flow Restriction.” Journal of Applied Physiology, American Physiological Society Bethesda, MD, Aug. 2013, doi:10.1152/japplphysiol.00040.2013.
Karabulut, Murat, et al. “Effects of High-Intensity Resistance Training and Low-Intensity Resistance Training with Vascular Restriction on Bone Markers in Older Men.” European Journal of Applied Physiology, vol. 111, no. 8, Aug. 2011, pp. 1659–67.
Patterson, Stephen D., and Richard A. Ferguson. “Enhancing Strength and Postocclusive Calf Blood Flow in Older People with Training with Blood-Flow Restriction.” Journal of Aging and Physical Activity, vol. 19, no. 3, July 2011, pp. 201–13.