Personalized BFR Rehabilitation for Patients with Possible Prior Nerve Injury
A question was raised recently as to whether it is safe and reasonable to conduct personalized BFR rehabilitation on a patient who may have a prior nerve injury. After consideration of the evidence-based clinical literature, and in consultation with experts in neurology and orthopedic/arthroscopic surgery, the following information is provided in response:
- There is no evidence in the clinical literature to suggest that prior nerve injury is a contraindication for use of a surgical-grade tourniquet instrument and surgical-grade tourniquet cuff in BFR rehabilitation. (Confirmed by recent PubMed search)
- Prior nerve injury is not listed as a contraindication or precaution in the ‘Instructions for Use’ of the personalized tourniquet system that is most commonly used for BFR.
- Any risk of nerve injury in BFR rehabilitation, whether or not the patient has a prior nerve injury, is mitigated by the use of a surgical-grade tourniquet instrument in which the lowest and safest tourniquet pressure can be determined based on Limb Occlusion Pressure (LOP), and by the use of personalized tourniquet cuffs which deliver lower pressures and lower pressure gradients to the underlying limb (see Background below).
- The existing clinical literature clearly shows that higher tourniquet pressure levels and higher cuff pressure gradients are associated with higher probability of nerve-related injuries (see Background below). Thus the use of non-personalized BFR cuffs and instruments, which may apply substantially higher pressures and higher pressure gradients to the underlying limb is not recommended. Non-personalized cuffs include narrow pneumatic cuffs and non-pneumatic elastic bands. Non-personalized instruments are those that cannot determine LOP and thus cannot recommend a patient’s restriction pressure based on LOP.
- In the absence of any evidence or contraindications, it is safe and reasonable to carry out personalized BFR rehabilitation on patients with possible prior nerve injury, using proven surgical-grade equipment and protocols.
- In treating such patients, standard protocols may be modified, for example by using a lower percentage of LOP or by using shorter periods of time, but this is not considered necessary and may affect outcomes in comparison with published data.
- For all patients, whether or not there may be a prior nerve injury, it is recommended that the patient’s condition prior to treatment be well documented, as well as the treatment protocol, specific instrument and cuff used, and patient outcome. The specific nature of any prior nerve injury should be documented, e.g. whether such injury may have been related to prior trauma, prior surgery or prior tourniquet use. Also, the extent of any prior nerve injury should be documented, e.g. whether it can be localized to a specific region. Such documentation will develop additional evidence of the value and safety of this rehabilitation modality for others in future.
In the literature, it has been shown that tourniquet-related nerve injuries may arise from two basic mechanisms. The first mechanism is the application of a high pressure gradient along the length of the nerve underlying a tourniquet cuff [1-5]. A high pressure gradient results in an axial force being applied along the nerve, effectively “stretching” and disrupting the nodes of Ranvier which surround the nerve, and injuring the underlying nerve cells. The location of such tourniquet-related nerve injuries is typically beneath the cuff location, and often near the distal edge of the cuff location. One cause of high pressure gradients is the application of high tourniquet pressures over a short distance, such as when narrow tourniquet cuffs are used, which require higher pressures for blood flow restriction compared to wider cuffs [6, 7].
The hazard of high pressure gradients is mitigated in some modern tourniquet systems by (1) use of personalized tourniquet pressures, optimized to identify the lowest pressure needed for individual patients, and (2) use of personalized tourniquet cuffs, designed to match the limb shape and optimally apply cuff pressure circumferentially and from one cuff edge to the other, thereby producing the lowest pressure gradients beneath the cuff when used in conjunction with personalized tourniquet pressures [7,8].
A second reported cause of tourniquet-related nerve injury is general ischemia of the limb distal to the cuff for an extended period of time, but this risk is mitigated by the use of short tourniquet times .
 Loenneke JP, Fahs CA, Rossow LM, Sherk VD, Thiebaud RS, Abe T, Bemben DA, Bemben MG. Effects of cuff width on arterial occlusion: implications for blood flow restricted exercise. European journal of applied physiology. 2012 Aug 1;112(8):2903-12.
 McEwen J, Casey V. Measurement of hazardous pressure levels and gradients produced on human limbs by non-pneumatic tourniquets. In: Proceedings of the 32nd Conference of the Canadian Medical and Biological Engineering Society 2009. Calgary, Canada; 2009 May 20-22. p 1-4.