The Objective Measurement of Brace-Use Adherence in the Treatment of Idiopathic Clubfoot

Sangiorgio, Sophia N. PhD; Ho, Nathan C. MS; Morgan, Rebecca D. BS; Ebramzadeh, Edward PhD; Zionts, Lewis E. MD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.16.00170
Scientific Articles
Abstract

Background: A successful outcome for the treatment of idiopathic clubfoot is believed to require adequate adherence to brace use. Previous studies have relied on parental reporting of brace application. We used temperature sensors to determine the adherence to the bracing protocol, the accuracy of parent-reported use, and differences in adherence between patients who experienced relapse of deformity and those who did not.

Methods: Using wireless sensors attached to brace sandals, we monitored brace wear over a 3-month period in this cross-sectional study involving 48 patients in 4 age-based groups: 6 to 12 months (Group 1), >1 to 2 years (Group 2), >2 to 3 years (Group 3), and >3 to 4 years (Group 4). Parents were blinded to the purpose of the sensors. The mean number of hours of daily brace use as measured by the sensors was compared with the physician-recommended hours and parent-reported hours of brace use.

Results: Sensors were retrieved from 44 of 48 patients. Overall, the median brace use recorded by the sensors was 62% (range, 5% to 125%) of that recommended by the physician, and 77% (range, 6% to 213%) of that reported by the parents. For Groups 1 to 3, the difference between the physician-recommended and measured number of hours of daily brace use was significant (p ≤ 0.002), and the difference between the parent-reported and measured number of hours of daily brace use was also significant (p ≤ 0.013). Eight (18%) of the 44 patients who completed the study experienced relapse during the period of monitoring; most importantly, the mean number of hours of brace wear for these patients, 5 hours per day (median, 4; and standard deviation [SD], 3 hours per day) was significantly lower than the 8 hours per day for those who did not experience relapse (median, 9; and SD, 5 hours per day) (p = 0.045).

Conclusions: The present study objectively quantified the number of daily hours of post-corrective brace wear for patients with clubfoot in varying age groups and provides an estimate of the number of hours required to avoid relapse.

Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Author Information

1The J. Vernon Luck, Sr., MD, Orthopaedic Research Center, Orthopaedic Institute for Children, Los Angeles, California

2Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California

3Department of Biomedical Engineering, University of Southern California, Los Angeles, California

E-mail address for S.N. Sangiorgio: SSangiorgio@mednet.ucla.edu

E-mail address for N.C. Ho: nathanho@mednet.ucla.edu

E-mail address for R.D. Morgan: Rdmorgan@mednet.ucla.edu

E-mail address for E. Ebramzadeh: EEbramzadeh@mednet.ucla.edu

E-mail address for L.E. Zionts: LZionts@mednet.ucla.edu

Article Outline

The Ponseti method has become the most widely used method of treating infants with idiopathic clubfoot deformity1. Initial deformity correction is achieved using a series of 4 to 6 weekly manipulations and cast applications, followed by an Achilles tenotomy, in most patients. Correction is maintained by using a post-corrective foot abduction orthosis (FAO). Although there is a general consensus that the FAO must be used nearly full time during the initial months after cast application, the recommended hours of brace use, as well as the duration of bracing, vary widely in the literature2.

Relapse of deformity has been attributed to the failure to adhere to the recommended use of a post-corrective brace3-19. The reported rate of failed adherence to brace use ranges from 32% to 61% in outcome studies with a minimum of 2 years of follow-up3-5,7-9,11-13. The determination of brace use in those studies may not have been accurate because the investigators determined adherence on the basis of parental estimates of the number of hours of daily brace wear. Therefore, objective monitoring of brace use, such as with sensors, must be employed to accurately assess adherence to brace use.

To our knowledge, clubfoot brace use has been measured objectively in only 1 previous study. Morgenstein and colleagues20 employed a pressure sensor to monitor initial brace use for 21 patients. Data were obtained from 15 of the patients for 1 month and from 7 of the patients for 3 months. The authors reported that patients wore the brace 91.7% of the physician-recommended hours during the first month of use, whereas the rate declined to 77.1% at 3 months. While that study presented important information, many questions remain regarding the importance of brace-use adherence to treatment outcome.

In the present study, we used Mitchell-Ponseti braces equipped with wireless temperature sensors to record brace-use adherence among patients with idiopathic clubfoot grouped according to age. We measured the number of hours of daily brace use in order to assess (1) the difference between clinician-recommended use and measured brace use, (2) the difference between parent-reported use and measured brace use, and (3) the extent to which measured brace use influences the risk of relapse during the study period.

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Materials and Methods

Study Overview

The criteria for participation in this prospective study were a diagnosis of idiopathic clubfoot deformity, no prior operative treatment, a Diméglio score21 of >5, and current use of a brace to maintain correction. All parents of patients between the ages of 6 and 48 months who met these criteria and were seen in our clinic between January 2015 and June 2015 were invited to participate until all positions in each age-based group were filled. Twelve patients were enrolled in each group, according to the following age categories: 6 to 12 months (Group 1), 13 to 24 months (Group 2), 25 to 36 months (Group 3), and 37 to 48 months (Group 4).

Patients were treated by a single surgeon using the Ponseti method22, and all patients used the Mitchell-Ponseti FAO (MD Orthopaedics)13. All participants had completed the first 3 months of full-time brace use and were given a recommended minimum use for nighttime and naptime that was based on normal sleep patterns of infants and children. In general, parents were instructed to apply the brace as follows: 16 hours per day until the age of 1 year, 14 hours per day between the ages of 1 and 2 years, 12 hours per day between the ages of 2 and 3 years, and 10 hours per day between the ages of 3 and 4 years23,24. In some cases, the parents were instructed to apply the brace for additional time if some loss of correction had been noted at prior clinic visits during the course of treatment. For this reason, all patient-specific recommendations for brace wear were documented (see Appendix). We used an ongoing, prospectively collected database of all patients with clubfoot seen in the clinic beginning in 2006, to compare the characteristics of the study patients with the overall clinic population.

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Wireless Temperature Monitoring

Two wireless SmartButton (ACR Systems) temperature data loggers were used to monitor brace wear for each patient (n = 96 sensors). The sensors featured programmable data-acquisition, a 3-V battery, and a data storage capacity of 2,048 readings, sufficient for continuous sampling every 90 minutes for approximately 4 months, the maximum time between clinic visits for the patient population. The sensors were attached to the outside of the brace sandals, just above the heel, to avoid locations prone to skin irritation (Fig. 1-A). The standard sandal was modified by placing a hole through the white rubber liner at the location of the temperature sensor to facilitate contact between the sensor and the foot (Fig. 1-B). To maximize data acquisition, sensors were placed on both sandals and programmed to sample the temperature every 90 minutes, offset by 45 minutes, making the effective sampling rate every 45 minutes.

The sensor functionality was validated internally prior to the onset of the present study, with socks of varying thicknesses and footed pajamas worn by healthy volunteer children of the same ages of the patients included in the present study. For the validation study, parent volunteers were instructed to document the exact times the brace was applied and removed. The engineer was blinded to this information when he analyzed the sensor data to calculate the hours worn. The analysis was then compared with the hours reported by the parents. Several data sampling rates were tested before the 45-minute interval was selected, and the process was repeated several times as the analysis programs and techniques were improved prior to the onset of the present study.

To minimize the likelihood that parental knowledge of the sensor might alter brace application, parents were told that the sensor was intended to monitor the temperature inside the brace to improve the comfort of future brace designs. The institutional review board approved this approach, provided parents were debriefed at the conclusion of their participation.

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Data Collection

At the patient’s enrollment clinic visit, full correction of the foot was confirmed on the basis of physical examination by the treating physician. Parents were provided with patient-specific instructions regarding the number of hours to apply the brace each day, which was documented. The foot was clinically evaluated again at the follow-up clinic visit, and the number of daily parent-reported hours of brace use was documented. Sensors were removed from the braces, and the data were downloaded to the study computer. The medical staff was blinded to the sensor data. If the medical staff noted that a relapse had occurred over the course of the monitored study period, this information was also documented. Relapse was defined as the reappearance of any component of clubfoot deformity that required additional cast application followed by the resumption of brace use or surgery.

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Data Reduction and Analysis

The data were imported into MATLAB (version 8.2.0.701; MathWorks) for data reduction and analysis. First, temperature data from both feet were synchronized to make a single data set for each patient. The mean temperature of the entire data set was then calculated to establish a baseline to indicate brace use. If single, isolated data points were observed to cross this baseline, the baseline was adjusted by 1° to 2° for each patient. This adjustment mitigated false positives due to varying environmental factors and ambient temperature concerns. Next, the number of data points above the baseline was converted into time measurements, which were used to calculate the average hours of daily use based on total days the patient had the instrumented brace. Four plots were generated for each patient: (1) all raw data, to verify gross sensor functionality, (2) the mean number of hours the brace was worn per day over the study duration, (3) a histogram of the mean hours worn per day, and (4) a sample plot of daily brace use (Fig. 2).

Adherence to brace wear was calculated by determining the ratio of hours the orthosis was worn to the hours of prescribed use, multiplied by 100 to express the quotient as a percentage. Similarly, the accuracy of parental reporting was calculated by determining the ratio of hours the orthosis was worn to the hours the parent reported the brace was worn, multiplied by 100.

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Statistical Methods

Chi-square analysis was used to compare the demographics of the 48 patients in the study cohort with those of the otherwise-eligible patients with clubfoot treated at our clinic who consented to participate in our master database study. Boxplots were constructed to display the distribution of the mean number of hours of recommended daily brace use and that of measured use for each of the 4 age-based groups. Paired t tests were performed to compare the recommended use with the measured use for each of the 4 groups. Similarly, boxplots were constructed to display the distribution of the mean number of hours of parent-reported daily brace use and that of measured use for each of the 4 age-based groups. Paired t tests were performed to compare the reported use with the measured use for each of the 4 groups. Finally, boxplots were constructed to display the distribution of the mean number of hours of daily brace use by patients who experienced relapse over the study period and that of patients who did not experience relapse.

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Results

Characterization of Patient Demographics

Forty-eight parents consented to participate in this study and were issued braces with sensors. Overall, the patient characteristics and family demographics of the study cohort were similar to those of otherwise-eligible patients treated at our clinic over the past 10 years (Table I). However, among the study cohort, only 3 (7%) of the patients had private insurance, which was somewhat lower than would be expected. The data collected and analyzed for the study cohort are presented in the Appendix.

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Completion

Of the 48 patient-issued instrumented braces, 4 were not returned. Two parents reported that the braces were lost and verbally confirmed that they were not worn as instructed. An additional 2 braces were lost, with no parent-reported information about brace use. As no sensor data were available for these 4 patients, they were excluded from the overall analysis. No family complained about the prominence of the sensors, no sensors malfunctioned, and there were no skin or other patient problems attributable to the sensors during the period of observation.

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Brace-Use Adherence

Parents were instructed to apply the brace for a mean of 12.6 hours per day (median, 12.0; and standard deviation [SD], 2.3 hours per day) (Table II). Instead, we measured 8 hours per day (median, 8; and SD, 5 hours per day). The number of hours recommended for each patient varied according to age, history of prior relapse, and clinical assessment by the treating physician. For the 3 groups of patients who were under the age of 3 years, the difference between the recommended protocol and the measured use was significant (p ≤ 0.002) (Fig. 3).

Adherence, expressed as a percentage of the recommended number of hours, ranged from 5% to 125% for all patients (median, 62%) (Table III). The median adherence among the 4 groups ranged from 41% to 76%, with the youngest and oldest patient groups being most adherent, and the middle 2 groups (the 1 and 2-year-old patients) being the least adherent.

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Accuracy of Parent-Reported Brace Use

Parents reported an average of 11.3 hours per day of brace use (median, 11.5; and SD, 3.6 hours per day). Again, this was higher than the total measured brace use of 8 hours per day (median, 8; and SD, 5 hours per day). The difference between the parent-reported brace use and the measured use was significant for the 3 youngest patient groups (p ≤ 0.013) (Fig. 4).

The parent-reported accuracy of brace use ranged from 6% to 213% of the measured brace use for all patients (median, 77%). The median parent-reported brace use among the 4 groups ranged from 57% to 108% of the measured brace use, with the parents of the oldest patients being the most likely to underestimate brace application, as indicated by a median value of >100% (Table III).

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Influence of Adherence on Relapse

Eight (18%) of the 44 patients who were monitored for the complete study period demonstrated relapse at their follow-up appointment; the mean measured brace application for those patients was 5 hours per day (median, 4; and SD, 3 hours per day), which was significantly lower than for those who did not relapse (mean, 8; median, 9; and SD, 5 hours per day) (p = 0.045) (Fig. 5). The mean adherence among patients who relapsed was 40% (median, 27%), whereas among patients who did not relapse, the mean adherence was 64% (median, 76%). The mean accuracy of parent-reported use among patients who relapsed was 70% (median, 47%), with a mean parent-reported use of 72% (median, 80%) among patients who did not relapse during the period of observation. Of the 4 patients who did not complete the study, 3 experienced a relapse of deformity at their follow-up appointment.

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Discussion

Adherence to the post-corrective clubfoot brace protocol has been stated to be the most important factor contributing to a successful outcome, and a lack of adherence is generally thought to be the most common cause of relapse3-19. Using various definitions, several studies have reported rates of nonadherence to brace use ranging from 32% to 61% of the recommended number of hours3-5,7-9,11-13. All of these studies relied on caregiver estimates of daily hours of brace use to determine nonadherence.

The present study showed that objectively measured post-corrective brace use was a median of 62% of that recommended by the physician. Furthermore, the estimated hours of brace use reported by the parents was a median of 77% of the measured use. On average, parents were instructed to apply the brace for 12.6 hours per day. They reported an average of 11.3 hours per day; as measured, brace used averaged 8 hours per day. For patients in the youngest 3 age groups (<3 years of age), families reported significantly higher brace use than was measured (p ≤ 0.013); however, for patients between the ages of 3 and 4 years, the difference between reported and measured brace wear was not significant (p = 0.468), indicating that parent-reported adherence was more accurate for older patients (Figs. 3 and 4).

Eight of the 44 patients who were monitored for the complete study period demonstrated relapse at their follow-up appointment. For those patients, the mean measured brace use, 5 hours per day, was significantly lower than the mean use among those who did not relapse, 8 hours per day (p = 0.045) (Fig. 5). This finding supports previous observations by investigators who reported an association between inadequate brace use, as reported by parents, and relapse3-19. However, the present study was the first, to our knowledge, to objectively quantify the relationship between brace wear and relapse. While the number of patients in the present study was perhaps too small to precisely determine the necessary number of hours—or brace dose—needed to prevent relapse, the results suggest that 8 hours or more of daily brace use may be helpful to prevent a relapse. Additional studies with larger cohorts will be needed to determine more accurately the minimum number of bracing hours necessary to curtail the frequency of relapse of deformity.

Heat25-30 and pressure31,32 sensors, embedded in orthoses, have been successfully used to accurately monitor brace wear in children with adolescent idiopathic scoliosis, which has led to several key advances in the treatment of scoliosis. Katz et al.26 used objectively measured brace-adherence data to determine a dose response, specifically, the rate of curve progression as a function of brace use. Those authors were able to demonstrate that, among 82% of the patients who wore their brace for ≥12 hours per day, the curves did not progress. More recently, Karol et al.33 reported that patient-specific data on brace adherence were effective for counseling patients and their families, thereby improving compliance and treatment outcomes, a strategy that may have future applicability to the families of patients with clubfoot.

To our knowledge, there has been only 1 previous article describing the objective measurement of clubfoot brace use. Morgenstein and colleagues20 used pressure sensors to monitor brace wear for a small group of patients. They found a mean adherence percentage of 91.7% in the first month of brace use (n = 15), which declined to 77.1% by the third month (n = 7). The authors concluded that mean adherence declined significantly; however, their study did not address adherence beyond the initial 3 months of use. In contrast, the present study was designed to quantify adherence over the entire course of brace treatment. This information may be beneficial to the clinician in interpreting parental reports of brace use.

There were several limitations of the present study. First, due to size limitations and the duration between patient visits, the sampling rate of the sensors was limited. However, the differences between the median recorded daily hours of brace use by patients who experienced relapse and those who did not was 5 hours, significantly larger than the effective resolution of our data logger, which was approximately 45 minutes. Second, this was a cross-sectional study, monitoring patients in several age groups, between 2 consecutive visits. Ideally, a longer-term longitudinal study may provide more information regarding brace-adherence patterns over time as a function of age. Third, findings pertain to a single institution with a single treating surgeon and a patient population composed largely of low-income families (88% with an annual family income of <$40,000; Table I), which may not be representative of the general population. Fourth, since the optimum number of hours of brace use to prevent relapse is not yet known, our recommendations for daily brace use were based on sleep patterns of infants and children as recommended by Ponseti22. Lastly, this study included only 1 post-corrective brace design.

In conclusion, this study objectively quantified the number of hours of brace wear among patients with clubfoot. Our findings showed that there was a difference between physician-recommended and actual brace use and that parent-reported use tends to be overestimated, particularly in younger patients. These observations indicate that routine brace monitoring has the potential to accurately identify patients who are receiving an inadequate number of hours of brace use and facilitate more effective counseling of these families. We also found that the patients who wore the brace more than 8 hours per day were less likely to experience relapse than those who wore it less than 5 hours per day. Larger studies are needed to more precisely establish the number of hours of post-corrective brace wear needed to reduce the occurrence of relapse of deformity. Currently in our practice, our findings assist us in better estimating actual brace use based on the parental report. Once better sensors and data retrieval systems are devised, we hope to routinely monitor all patients in the future.

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Appendix Cited Here...

A table showing the data collected and analyzed for patients in the study cohort is available with the online version of this article as a data supplement at jbjs.org.

NOTE: The authors thank Sanghun Alejandro Chung, MS, and Brice Lekavich, MS, for assistance with sensor testing and validation; Mohammad Nazif, BS, for assistance with data analysis and manuscript preparation; and Michael Jew, BS, and Shannon Cooper, BS, for assistance with clinical data collection.

Investigation performed at the J. Vernon Luck, Sr., MD, Orthopaedic Research Center at the Orthopaedic Institute for Children, Los Angeles, California

Disclosure: The study was funded by a 2014 Pediatric Orthopaedic Society of North America clinical research grant. Braces were donated by MD Orthopaedics, Wayland, Iowa. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article.

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