May 2018

Biofeedback aids in resolving the paradox of weight-bearing

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Too much? Or not enough? New biofeedback tools help patients with lower-limb fracture in their struggle to understand how much weight to bear on an injured limb.  

By Jill R. Dorson

Clinicians whose patients have a lower-limb fracture are faced with a paradox: whether or not to instruct them to place weight on the healing fracture. There are clear arguments on both sides of the issue: Placing a specified amount of weight on a healing fracture can help bone growth1; conversely, placing too much weight on a fracture or surgical implant can impede, even damage, the healing progress.

Combine that ambiguity with patients’ traditionally low compliance with weight-bearing instructions, and the medical community is left at a crossroads. One direction does appear to offer hope. Raaben et al recently reported that visual biofeedback not only helps improve compliance but also gives more meaningful feedback to patients and medical practitioners so they can better determine how much weight to place on the injured site.2

There is no doubt, however, that weight-bearing is important in rehabilitation. Several studies have shown that partial weight-bearing can improve fracture healing, help maintain bone stock and bone mineral density, and be useful in healing overuse injuries.3,4 In addition, weight-bearing early in the recovery process can help to keep healing fractures aligned and implants in place.

Every institution has its own rules— some using percentage of body weight, some using number of pounds, others using patient “feel.”

What does weight-bearing mean?

It is obvious that weight-bearing means patients should put weight on the injured site, but there is no standard definition. Every institution has its own rules—some using percentage of body weight, some using number of pounds, others using patient “feel.” The Table5 describes how the University of Pittsburgh Medical Center defines levels of weight-bearing.

The more targeted question, though, is: How much weight at different stages of rehabilitation? A look at weight-bearing instructions from multiple rehabilitation centers makes it clear that there is no standard for the amount of weight at different stages of recovery and that the determination of the percentage of weight is often left up to the ability of the patient to determine.

For example, weight-bearing instructions provided by Twin Cities Orthopedics, a chain of rehabilitation centers in Minnesota, calls for patients to wear controlled ankle motion boots following an ankle fracture and use a bathroom scale to “get a feel” for what a certain degree of weight bearing feels like, and then:6

…[i]f you are able to tolerate 25% well, progress to 50% of your body weight; if you are able to tolerate 50% well, progress to 75% of your body weight…

Although a physical therapist would presumably help a patient to understand how much weight 25% or 50% of their body weight is, that number can be hard to translate outside of a well-calibrated clinical setting.

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Mobile systems are the next generation of weight-bearing measurement technology

A mobile biofeedback system created by researchers at Universitair Medisch Centrum (UMC) Utrecht, The Netherlands, is an example of the latest advancement in the measurement of weight-bearing. The SensiStep device, custom-made sandals outfitted with force sensors, a wristband, and wireless technology, allows medical practitioners to monitor weight-bearing while a patient is walking. According to the website on which the device is showcased (www.sensistep.com), it provides real-time data about load. The team that developed the device shared insight into the device through a 2017 Sensors article.13

Historically, biofeedback systems had limited use due to their bulkiness; there were often cables associated with the machine, and the reliability of sensors could be compromised by changes in temperature or humidity—and by cost. Newer technology is more nimble and allows physical therapists to not only monitor the weight put onto an injured limb, but to input a specific target load. The patient is then alerted when he (she) is putting too much or not enough weight on the limb.

Numerous studies are documenting how mobile devices can help improve compliance and, unlike cumbersome predecessors, be used in dynamic situations.

Jill R. Dorson is a freelancer writer.

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How to measure weight-bearing

Physical therapists use 3 key methods to measure how much weight a patient is bearing on a healing limb, although biofeedback has been shown to be the most promising.7

Tactile feedback from a physical therapist is the method most often used,1 although at least 1 study3 has shown that this method does not accurately train the patient. In this scenario, a physical therapist will place his (her) hand beneath the patient’s foot and estimate the amount of weight being applied. While this method is cost-effective because no special equipment is needed, it does require a well-trained physical therapist. However, in a 2009 study published in Archives of Physical Medicine and Rehabilitation, even the best physical therapists erred by as much as 30% of desired weight in their estimate.8

A second method used to measure weight-bearing is a simple bathroom scale. A patient can step onto the scale to get an idea of how it feels to bear a certain weight. However, the activity is static, and multiple studies have shown that the act of standing does not adequately replicate the act of walking, and is therefore not fully useful.9,10

The method gaining traction for measuring weight-bearing is biofeedback, which allows patients to get feedback while walking. As early as 2001, a Swedish study that employed biofeedback using pressure-sensitive insoles found that, that despite verbal feedback, none of the patients were able to comply with weight-bearing instructions and, in fact, questioned the usefulness of limited weight-bearing in rehabilitation.3

Adapted from: University of Pittsburgh Medical Center.5

Fast-forward 17 years and, in a 2018 Gait and Posture study, Raaben et al provide evidence that weight-bearing was more easily understandable with the use of real-time visual biofeedback.2 The recent study had 2 groups with lower-extremity fracture: one group in which full weight-bearing was prescribed; the other, touch-down weight-bearing. Both groups walked 15 meters while the biofeedback system registered their weight-bearing. Then, the groups were asked to walk the 15 meters with visual biofeedback. Visualization allowed the participants to adapt their load, improving compliance overall.

Findings were significant for the full weight-bearing group—increasing from 51% body weight for the first walk to 74% body weight with visual feedback (P=0.0016). The touch-down weight-bearing group saw decreases in exerted load from 16.7 kg (±9.77 kg) without feedback to 10.27 kg (±4.56 kg) with visualized feedback (P=0.0718). Significantly, variance between individual steps decreased with visual feedback (P=0.018).

The authors concluded that feedback that was visualized in real time improved therapy compliance in these participants. The findings are in line with past work, which found that patients are not only more likely to follow directions, but are more likely to properly execute instructions with the assistance of biofeedback.1

Why is compliance among patients low in weight-bearing?

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Although methods of measuring weight-bearing in healing patients have until recently been inexact, reasons for low rates of compliance among patients are multifactorial. Reasons range from the amount of pain a patient feels when bearing weight to the anxiety of feeling the pain or a patient’s fear of doing further damage. In his most recent study, researcher Marco Raaben, a PhD candidate at Universitair Medisch Centrum (UMC) Utrecht, The Netherlands, found that failing to follow weight-bearing instructions can have a negative effect on healing, ranging from displacing the fracture to causing failure with the implant.2

As a practical matter, weight-bearing on an injured limb requires an attentiveness that many patients do not have. Consider that, when patients leave the controlled clinical setting, they are often faced with unique challenges—stairs, pets, children—that can take their attention away from focusing on weight-bearing.

This consideration leads to the issue of life in the real world. As with prescription nonadherence, noncompliance with weight-bearing instructions has been reported at approximately 25%;11 indeed, in this 2016 study, nearly 42% of the noncompliant group suffered adverse events, compared with 12% of the compliant group, despite receiving explicit advice on the potential for complications. Compliance and noncompliance was comparable across all groups, with the only significant influence being warmer weather, which led to more noncompliance. The editorial that accompanied the published study reminds clinicians to consider patient-centered outcomes and lifestyle ramifications when providing such instructions.13

As artificial intelligence becomes more customizable and technology evolves to make biofeedback devices smaller and more user friendly (see “Mobile systems are the next generation of weight-bearing measurement technology”13), the opportunity to personalize a prescription for weight-bearing to meet an individual patient’s needs becomes a very real possibility. Will the clinician order it? Will the patient follow it? Stay tuned for answers to these questions.

REFERENCES
  1. Hustedt J, Blizzard D, Baumgaertner M, Leslie MP, Grauer JN. Current advances in training orthopaedic patients to comply with partial weight-bearing instructions. Yale J Biol Med. 2012;85(1):119-125.
  2. Raaben M, Holtslag H, Leenen L, Augustine R, Blokhuis TJ. Real-time visual feedback during weight bearing improves therapy compliance in patients following lower extremity fractures. Gait Posture. 2018;59:206-210.
  3. Tveit M, Karrholm J. Low effectiveness of prescribed partial weight bearing. Continuous recording of vertical loads using a new pressure-sensitive insole. J Rehabil Med. 2001;33(1):42-46.
  4. Kubiak E, Beebe M, North K, Potter M. Early weight bearing after lower extremity fractures in adults. J Am Acad Ortho Surg. 2013;21(12):727-738.
  5. University of Pittsburgh Medical Center. Weight bearing. UMPC website. . Accessed June 19, 2018.
  6. Hess R, Pederson T. Ankle fracture. Non-operative treatment. Weight-bearing progression. Twin Cities Orthopedics website. https://tcomn.com/wp-content/uploads/2017/03/Ankle-Fracture-Non-Surgical-Weight-Bearing-Progression-New-2017.pdf. Accessed June 19, 2018.
  7. Abdalbary SA. Partial weight bearing in hip fracture rehabilitation. Future Sci OA. 2017;12;4(1):FSO254.
  8. Hurkmans H, Bussmann J, Benda E. Validity and Interobserver reliability of visual observation to assess partial weight-bearing. Arch Phys Med Rehabil. 2009;90(2):309-313.
  9. Malviya A, Richards J, Jones R, Udwadia A, Doyle J. Reproducibility of partial weight bearing. Injury. 2005;36(4):556-559.
  10. Chow D, Cheng C. Quantitative analysis effects of audio biofeedback on weight-bearing characteristics of persons with transtibial amputation during early prosthetic ambulation. J Rehabil Res Dev. 2000;37(3):255-260.
  11. Chiodo CP, Macaulay AA, Palms DA, Smith JT, Bluman EM. Patient compliance with postoperative lower-extremity non-weight-bearing restrictions. J Bone Joint Surg Am. 2016;98(18):1563-1567.
  12. Bogie K. Consider the patient When prescribing total non-weight-bearing: Commentary on an article by Christopher P. Chiodo, MD, et al.: “Patient compliance with postoperative lower-extremity non-weight-bearing restrictions.” J Bone Joint Surg Am. 2016;98(18):e80.
  13. Raaben M, Holtslag HR, Augustine R, van Merkerk RO, Koopman BF, Blokhuis TJ. Technical aspects and validation of a new biofeedback system for measuring lower limb loading in the dynamic situation. Sensors. 2017;17(3). pii: E658.
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