Summary
Use of wearable technology to assess return to sport after ACL reconstruction
Abstract
Background
Clinical guidelines for return-to-play (RTP) following anterior cruciate ligament reconstruction (ACLR) rely on a combination of external physiologic parameters such as time, physical examination, functional RTP assessments and clinical judgement. Currently, there are no internal physiologic variables utilized to predict readiness for RTP.
The purpose of this study is to utilize a wearable muscle oxygen sensor to: 1) collect quadricep muscle oxygen saturation (SmO2) in healthy athletes to assess symmetry of the lower extremities to validate the contralateral limb as a control and 2) track return of quadricep muscle oxygen symmetry as an internal physiologic parameter for RTP against current assessments after ACLR.
Methods
50 healthy athletes between 14-25 years-old without a history of lower extremity injury were enrolled in standardized aerobic, isometric and strength tests while wearing a muscle oxygen sensor. Muscle oxygen sensors were placed on the quadriceps bilaterally allowing for continuous collection of muscle oxygen saturation (SmO2). An age-matched cohort of 28 athletes who underwent ACLR were enrolled alongside the healthy cohort. For all ACLR patients, demographics, graft type and quadriceps girth were collected at each visit. ACLR patients subsequently underwent the same testing protocol at 6-, 9-, and 12-month timepoints post-surgery. For each athlete, the time-paired difference in SmO2 was calculated by subtracting the normal SmO2 % from the affected leg SmO2.
Results
50 healthy athletes, 21 males and 29 females (mean age 20.1 yo; range: 18-22 y.o.) and 28 athletes post-ACLR, consisting of 16 males and 12 females (mean age 16.5 y.o.; range: 14-21 y.o.), completed the trial. 25/28 surgical athletes underwent patellar tendon autograft and 3 underwent quadriceps autograft. Within the healthy cohort, the mean difference in SmO2 did not statistically differ between the legs in any of the 3 exercise tests. Healthy athletes exhibited a normal variation in SmO2 within ± 5% between their legs confirming the paired extremity is a valid control. On average, surgical athletes did not see a return of normal muscle physiology by the 6- and 9-month time points but did by the 12-month time-point. 8/28 (28.6%) athletes at 6-months, 10/28 (35.7%) athletes at 9-months and 20/28 (71.4%) athletes at 12-months saw recovery of physiologic SmO2. Based on current external physiologic clinical guidelines, mean RTP was 10.8 months. Individually, 0/28 (0%) at 6-months, 15/28 (53.6%) at 9-months and 26/28 (92.9%) patients at 12-months met clinical criteria for RTP.
Conclusion
Based on healthy athletes, SmO2 measured using a wearable technology device revealed ±5% differential with side-to-side assessment using 3 standardized exercise parameters. Therefore, the contralateral extremity can serve as a control when assessing return of baseline internal physiologic muscle function. For the first time, this study introduces the use of wearable technology to assess internal physiologic parameters (muscle Sm02) as an additional clinical data point to guide RTP after ACLR. Further studies are underway to measure the predictive value of Sm02 measurements in RTP timing, risk of recurrent ACL injury and evaluate the need for personalized rehabilitation protocols.