Abstract
Introduction
Total knee arthroplasty (TKA) is highly successful due to pain reduction, patient satisfaction, and increased range of motion (ROM) during activities of daily living (ADL). ROM recovery is critical for successful outcomes, however ROM values are typically captured during routine physical therapy (PT) appointments via simplified measures (e.g. goniometric maximum passive ROM). These measures are imprecise, potentially neglecting patients’ home experiences. Accordingly, improved measurement methods are necessary to realistically represent ROM recovery. A validated inertial measurement unit (IMU) method continuously capturing knee ROM was deployed assessing knee ROM recovery during PT appointments and during patients’ routine daily experiences. Our objectives were to 1) continuously capture knee ROM pre-/post-TKA via IMUs and 2) divide each day's data to PT/non-PT segments comparing ‘gold standard’ ROM measurements (PT periods) with non-invasive home measurements (non-PT periods). Given patients are verbally/physically encouraged during PT, we hypothesized PT and non-PT metrics would be significantly different including 1) greater kinematics, 2) shorter times, and 3) greater activity level during PT compared to non-PT.
Methods
Following IRB approval, IMUs captured long duration, continuous (8–12 hours/day, ∼50 days) knee ROM pre-/post-TKA. Post-TKA metrics were subdivided to PT/non-PT time periods including maximum ROM, gait phase ROMs (stance/swing), gait times (stride/stance/swing), and activity level. Clinical ROM and patient reported outcome measures (PROMs) were also captured before/after TKA. Statistical comparisons were completed between pre-TKA, post-TKA PT, and post-TKA non-PT metrics. Correlation analyses were completed between IMU, clinical ROM, and PROMs.
Results
10 TKA patients (3M, 69±13 years) enrolled. Patient compliance with sensor use was high (pre-TKA: 9.7±1.8 hours/day, 6±1 days; post-TKA: 8.5±2.3 hours/day, 37±4 days). Patients received 1.5±0.5 standard PT sessions per postop week (1.1±0.2 hours/session). All patients were well-healed at 6-weeks post-TKA with no additional surgical interventions required. Dividing ROM data showed distinct qualitative differences between PT and non-PT periods. Specifically, maximum knee ROM was significantly less during PT than outside PT during late rehabilitation weeks. Additionally, PT stance and swing phase ROM were significantly greater during PT throughout recovery. No differences in stride/stance/swing time were noted between PT/non-PT periods during recovery. However, significant activity level differences were noted throughout recovery.
Discussion
This study highlights limitations utilizing clinic captured ROM establishing recovery. Notably, IMU ROM measurements allow capturing richer information than discrete simplified clinical measures. Maximum flexion during PT was likely less than non-PT due to exercises completed (i.e. high passive ROM vs. low ROM gait performance). PT gait flexion was likely greater than non-PT because of ‘white coat effects’ wherein patients are closely monitored clinically, whereas gait is completed as desired at home. Interestingly, temporal metrics were equal between PT/non-PT implying clinician's presence encourages improved kinematics but has no impact on ambulation timing. Activity level was significantly greater during PT than non-PT likely resultant from clinicians enforcing high activity levels throughout PT sessions. In total, these results imply data captured clinically represents optimum patient performance whereas data captured non-clinically represents realistic patient performance.
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