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The Use of Adherence Monitors with Orthoses

Kevin Felton, CO, LO

Disclosure: The author has no commercial or proprietary interest in any product mentioned.

ABSTRACT

As the outcomes of orthotic treatments are increasingly scrutinized, practitioners are seeking to gain an understanding of the effects of variable patient adherence. Several groups have developed electronic adherence monitors for orthoses, but these have not achieved widespread use. By making the development and use of reliable adherence monitors for orthoses a high priority, orthotists may soon be able to document the effectiveness of orthotic treatments.

Key Words: patient compliance, orthotic devices, monitoring, ambulatory.

Increasingly, healthcare practitioners are required to document the effectiveness of treatments through outcome studies.¹ One aspect of outcomes-based research that has received insufficient attention in the field of orthotics is adherence to the treatment regimen. Currently we do not know what the therapeutic threshold is for effective treatments. Also lacking are objective data to determine whether adverse outcomes are due to ineffective orthoses or insufficient wear. Electronic adherence monitors must be developed to provide these needed data.

Why Monitor Adherence?

We implicitly accept the dose dependency of orthotic treatment when recommending wear schedules, but seldom do we have objective data to support our assumptions. The effectiveness of these orthoses is assumed to be related to the wear schedule. For example, the debate over 23 or 16 hours-per-day wear of the Boston brace has continued well beyond Green's 1986 paper that suggested the shorter wear time was adequate.²

Clinically we ask patients how much they wear their orthoses. However, we know that self-reports such as these tend to be exaggerated.³ One might argue that, for clinical use, patient self-reports are accurate enough; however, for research purposes we need more objective methods.

Terminology

"Compliance" and "adherence to the treatment regimen" are synonymous terms that are usually used interchangeably. Some authors, such as Feinstein,⁴ believe that compliance is the more accurate term. However, Meichenbaum and Turk⁵ state that the connotations of adherence to a mutually agreed on treatment regimen are more positive than those of compliance with the practitioner's orders.

Design

An electronic adherence monitor consists primarily of two components: the sensor, with any signal conditioning circuitry, and the recording device. Signal conditioning modifies the output of the sensor to provide appropriate data for the recording device.⁶ All components must fit unobtrusively into the orthosis. In addition, the clinic must have a computer to download data from the adherence monitor.

Dunbar pointed out that no universal standard for measuring adherence exists and that we must create a threepart adherence definition for each study. First we must define the behavior under study. Then we must determine how to describe that behavior, and finally we must determine the time period of interest.⁷ For an orthosis adherence monitor, orthosis wear might be the chosen behavior. To describe wear, we might use strap tension, surface pressure, temperature, or proximity to the orthosis. We then must decide whether to look at a short sample of the day or week, or to follow wear patterns over months or years. These aspects of the adherence definition will have a profound influence on the design of the monitor.

Caution

Rudd's second standard for adherence monitoring requires that a monitor be objective.⁸ We must rigorously test any such device to assure that it meets this standard. Failure to do so may lead to the sorts of errors reported by Brueckner, Marshik, Sherman, and Hendeles from a commercially available monitor for inhaler use. Frustrations with the units led them to test four new monitors for one week before using them with patients. They reported that only one functioned correctly, although it failed within a month of patient use.⁹

Who is Monitoring Adherence?

Pharmaceutical researchers are leading the way in developing novel methods of measuring adherence to treatment regimens. Microelectronic monitoring has become common in drug trials with the advent of the commercially available Medication Event Monitoring System (MEMS)¹ The MEMS consists of a pill bottle whose cap contains a microprocessor that records each opening of the bottle as a presumptive dose.¹⁰ Knowledge of adherence to the treatment regimen allows more accurate determination of the therapeutic effects in drug therapy.

Activity-Based Monitors

Although studies involving medication monitors abound, few discuss remote measurements of patients' activity or interaction with orthoses. The authors of these studies have shown considerable ingenuity with their approaches to the problems. Each has attempted to fulfill the three criteria for adherence monitors set down by Rudd: "The ideal standard would be simultaneously unobtrusive (so as to avoid patient sensitization and maximize cooperation), objective (to produce discrete and reproducible data for each subject), and practical (to maximize portability and minimize cost)."⁸

Several monitors of "up-time" (time spent standing and walking)¹¹ have been developed. In two of these monitors, mercury switches record when a patient's thigh attained a near vertical position. In the 1980s, Sanders^12,13 required patients to wear a timer on their belts with a wire extending to a thighmounted switch. Later advances in electronics allowed Tran, Schwarz, Gorman, and Helme¹¹ to build a single small device for patients to wear on a thigh. Mechanical issues, such as determining the optimal alignment and waterproofing, remained as significant challenges.

An even more ambitious attempt to measure patient activity was undertaken by Walker, Heslop, Plummer, Essex, and Chandler. In their device, a microcomputer sampled the states of two mercury switches and a chest-mounted accelerometer. An onboard alarm could be set to prompt patients to enter their pain level on the keyboard periodically.^l4 A simpler contact-switch step counter was used by Sykes, Ross, Powell, and Edwards to determine the number of steps taken by paraplegic patients in a reciprocating gait orthosis (RGO) with and without electrical simulation.¹⁵

Recently, Coleman, Smith, Boone, Joseph, and del Aguila have developed the Step Activity Monitor (SAM). The Step Activity Monitor is a small device worn about the ankle that provides data on the patient's step frequency at fixed intervals. This device has been used to assess patient activity levels with different treatments or prosthetic components.¹⁶ These approaches have proved useful for measuring changes in patient activity that might be attributable to the treatment modalities.

Wear-Based Monitors

When the behavior of interest is not directly linked to activity, the situation becomes more difficult. Houghton, McInerney, and Tew developed the "E cell" to measure Boston brace wear. Notably, all components were hidden, so patients and physicians were blinded to the monitor.¹⁷ However, Smith, Platts, Edgar, and Sweeting, while developing their own monitor, found the E-cell system inaccurate because patient movements within the orthosis could cause the lumbar-pad pressure switch to cycle off.¹⁸

Similar problems face orthodontists who wish to know how well orthodontic headgear is worn. Kyriacou and Jones have described an experimental device that relies on tension through the springs, much like strap tension in an orthosis, with the addition of a temperature threshold to keep patients from cheating.¹⁹ However, none of these wear-based adherence monitors has achieved widespread use.

Conclusion

As we strive to provide optimum care for our patients, we must have reliable data on which to base our orthotic interventions. Outcome studies to determine the most efficacious treatments are beginning to include the effects of variable treatment adherence.

Urquhart pointed out that patients are continually conducting "natural experiments" all around us by variably adhering to their treatment regimens. Also, in situations where the use of a true control group may be unethical or impractical, the lowest stratum of the adherence spectrum may be used to approximate controls.²⁰ We can use these natural experiments to determine optimum treatment duration and minimum effective wear time of orthoses.

Electronic monitoring is a promising data-collection tool for conducting outcome studies. Objective data comparing outcomes with actual orthosis wear will greatly enhance our understanding of the efficacy of orthotic interventions.

Acknowledgements

Special thanks to Tim Crusius, PhD, for editorial assistance and encouragement.

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