JMIR Publications

ABSTRACT

Background:

Knee braces may improve symptoms and physical function following anterior cruciate ligament reconstruction (ACLR). However, their effectiveness depends on adherence, which typically relies on self-reported wear time that is prone to recall and response bias. Objective measures of adherence, such as temperature sensors, which are already validated in footwear and orthotics research, offer a potentially more accurate alternative to self-reporting. Despite this, there is no research comparing self-reported and sensor-measured wear times in a knee brace.

Objective:

To determine how well self-reported wear times reflect sensor-measured data in a slim-fit knee brace.

Methods:

Young adults (18-45 years), 1-8 years post-ACLR with early-onset knee osteoarthritis symptoms (KOOS4 score <80/100) wore a slim-fit brace during a 6-week feasibility trial. Self-reported wear times were recorded in daily logs. An undisclosed, embedded temperature sensor recorded temperature once every 10 minutes. A wear detection algorithm identified brace donning and doffing. These data were used to calculate aggregated measures (cumulative wear time over the 6-week intervention period, average daily wear time, total number of days worn) and repeated measures (daily wear duration, 3- and 7-day rolling averages). Agreement between self-reported and sensor-based measures was assessed using concordance correlation coefficients (CCC) and limits of agreement (LoA).

Results:

Of 14 randomised participants, 10 (30% male, age 33±6 years, 4±1 years post-ACLR) had both temperature sensor and self-reported wear data. Six participants (60%) under-reported average daily wear time (mean 29±24 minutes across all 10 participants), while nine (90%) over-reported the number of days worn (mean 9±6 days across all 10 participants). Daily wear time showed moderate agreement between the sensor and self-reporting (CCC 0.70, 95%CI 0.58 to 0.79), but wide LoA (-223 to 217 minutes). Using 3- or 7-day rolling averages narrowed LoA (-47 to 36 minutes per day and -14 to 10 minutes per day, respectively) and slightly improved CCCs (0.74, 95%CI 0.58 to 0.85, and 0.73, 95%CI 0.51 to 0.86, respectively). Greater agreement was observed with more aggregated outcomes; for total 6-week wear time, the CCC was 0.84 (95%CI 0.50 to 0.95). When expressed as daily average wear time, the CCC was excellent (0.92, 95%CI 0.73 to 0.98), although daily LoA still remained wide (-68 to 32 minutes), indicating substantial individual variability between self-reported and sensor-based measures. For the total number of days worn, the CCC was moderate (0.64, 95%CI 0.15 to 0.88) and LoA wide (-10 to 22 days).

Conclusions:

Self-reported daily brace wear time is inaccurate compared to objectively measured adherence using a temperature sensor. Aggregated data and rolling averages showed better agreement. Future intervention studies should consider objective adherence measures. Failing this, averaging self-reported wear time across the intervention period could improve accuracy. Clinical Trial: ACTRN12623001027606