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. 2019 Aug;28(8):1505-1514.
doi: 10.1016/j.jse.2019.01.003. Epub 2019 Apr 5.

Continuously monitoring shoulder motion after total shoulder arthroplasty: maximum elevation and time spent above 90° of elevation are critical metrics to monitor

Ryan M Chapman  1 , Michael T Torchia  2 , John-Erik Bell  2 , Douglas W Van Citters  3
Affiliations

Continuously monitoring shoulder motion after total shoulder arthroplasty: maximum elevation and time spent above 90° of elevation are critical metrics to monitor

Ryan M Chapman et al. J Shoulder Elbow Surg. 2019 Aug.

Abstract

Background: Traditional clinical shoulder range-of-motion (ROM) measurement methods (ie, goniometry) have limitations assessing ROM in total shoulder arthroplasty (TSA) patients. Inertial measurement units (IMUs) are superior; however, further work is needed using IMUs to longitudinally assess shoulder ROM before TSA and throughout post-TSA rehabilitation. Accordingly, the study aims were to prospectively capture shoulder elevation in TSA patients and to compare the results with healthy controls. We hypothesized that patients would have reduced maximum elevation before TSA compared with controls but would have improved ROM after TSA.

Methods: A validated IMU-based shoulder elevation quantification method was used to continuously monitor 10 healthy individuals (4 men and 6 women; mean age, 69 ± 20 years) without shoulder pathology and 10 TSA patients (6 men and 4 women; mean age, 70 ± 8 years). Controls wore IMUs for 1 week. Patients wore IMUs for 1 week before TSA, for 6 weeks at 3 months after TSA, and for 1 week at 1 year after TSA. Shoulder elevation was calculated continuously, broken into 5° angle "bins" (0°-5°, 5°-10°, and so on), and converted to percentages. The main outcome measures were binned movement percentage, maximum elevation, and average elevation. Patient-reported outcome measures and goniometric ROM were also captured.

Results: No demographic differences were noted between the cohorts. Average elevation was not different between the cohorts at any time. Control maximum elevation was greater than pre-TSA and post-TSA week 1 and week 2 values. Time under 30° and time above 90° were equal between the cohorts before TSA. After TSA, patients showed decreased time under 30° and increased time above 90°.

Discussion: This study demonstrates that acute and chronic recovery after TSA can be assessed via maximum elevation and time above 90°, respectively. These results inform how healthy individuals and patients use their shoulders before and after TSA.

Keywords: Arthroplasty; inertial measurement unit; range of motion; rehabilitation; shoulder; wearable.

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Figures

Figure 1.
Figure 1.
Example instrumentation including A) IMU donning locations on the sternum and humerus and B) angle computation between gravity and acceleration data.
Figure 2.
Figure 2.
Data processing workflow including 1) raw accelerometer signal input, 2) processing accelerometer signals (bony segment differentiation, low pass filtration, offsetting anatomical/sensor misalignment, and distal to proximal coordinate transformation), 3) continuous shoulder elevation calculation, 4) daily metric calculation (average, maximum bin > 10x, maximum elevation, binned movement rate, binned percentage), 5) weekly metric averages, and 6) total subject averages.
Figure 3.
Figure 3.
Average shoulder elevation for controls (solid) and TSA patients (pre-TSA: striped, post-TSA: dotted).
Figure 4.
Figure 4.
Maximum shoulder elevation for controls (solid) and TSA patients (pre-TSA: striped, post-TSA: dotted). Statistically significant differences between cohorts are denoted by an asterisk.
Figure 5.
Figure 5.
Movement percentage A) less than 90° elevation binned in 15° increments and B) greater than 90° elevation binned in 45° increments.
See this image and copyright information in PMC

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