Treadmill Perturbation Training for Fall Prevention After Total Knee Replacement

Participants:

We will recruit 196 participants who are scheduled for primary unilateral total knee arthroplasty (TKA) and can commit to 5 additional study visits.

Baseline assessment: At enrollment, all participants will be assessed for a set of demographic and functional risk factors listed below

1. Age
2. Sex
3. Body mass index
4. Number of painful joints - Patient Reported Arthralgia Inventory
5. Medications that increase fall risk
6. Number of falls in the past 12 months
7. Self-reported activity level (UCLA activity score)
8. Habitual walking speed (8-meter walk test)
9. Functional Limitations
10. PROMIS (Patient-Reported Outcomes Measurement Information Systems) Physical Function computerized adaptive test (CAT)
11. Knee Injury and Osteoarthritis Outcome Score (KOOS) Activities of Daily Living Subscale
12. Pain - KOOS pain subscale; Intermittent and Constant Osteoarthritis Pain Scale; Pain Catastrophizing Scale; Tampa Scale of Kinesiophobia
13. Balance and mobility impairment
14. Timed up and go test
15. 30 second chair stand test
16. 4 stage balance test
17. 8 m walk test
18. Functional reach test
19. 6-minute walk test
20. 4 square step test
21. Comorbidities - SCQ comorbidity questionnaire
22. Depression - PROMIS depression (CAT)

Participants will also undergo a standard gait analysis assessment consisting of approximately 5 nonconsecutive minutes of walking at comfortable and fast speeds on an instrumented treadmill with reflective markers will be placed on bony landmarks of the trunk, arms, and lower extremities.

After this assessment, participants will be provided with a Fitbit that they will wear daily except during bathing or swimming. Physical activity level will be measured for the duration of the follow-up period (1 year).

Finally, randomization assignments will be provided along with written education materials (fall prevention brochures from the Centers for Disease Control and Prevention), and the following activities will be undertaken according to grouping:

Group 1 - Perturbation training (4 sessions over 2 weeks with a post-test session 1 week later):

1. 30 reflective markers will be placed on bony landmarks of the trunk, arms, and lower extremities with one marker indicating the proximal and distal end of each segment and one marker placed out of line with the other two so that the motion capture software can define the 3D motion of each segment.
2. Participants will be stand comfortably with feet at approximately hip width, on a split belt treadmill. They will be fitted with a safety harness. They will be instructed that the treadmill will move and that they should do whatever they can to maintain or regain their balance.
3. During the next one minute, a tester will activate the treadmill. Two small surface translations (0.02 cm at roughly 0.22 m/s) will then be administered which will require several small forward directed steps to regain stability. These two small disturbances will provide a familiarization of how the treadmill works.
4. Participants will be informed that they will receive up to 30 disturbances of larger magnitude while facing forward, then again while facing to each side. They will be instructed to "do whatever [they] can to recovery [their] balance".
5. On the next perturbation, the participant will receive a larger disturbance. Each training perturbation will consist of the treadmill accelerating for 300 ms, maintaining a constant velocity for 170 ms, then decelerating to 0 m/s in 100 ms. Prior to the disturbance participants will be informed to recover their balance and continue walking for 5 seconds after the perturbation.
6. The tester will then administer no more than 30 disturbances of increasing difficulty as tolerated by the participant.
7. A final perturbation will be administered. This constitutes the post-test assessment.
8. Steps 2-7 will be repeated with the participant turned 90 degrees such that a step to the side will be required. The magnitude of the perturbations will be scaled to 2 foot widths.
9. Step 8 will be repeated with the participant turned by 180 degrees such that both sides receive lateral training.

Group 2 - Education Control: this group will not undergo additional training but will only receive the written materials

Beginning one week after surgery and then every two weeks for one year, participants will be contacted by text message and asked whether they had fallen during the previous two weeks. People who report falls will be contacted for a detailed interview about the circumstances and consequences of the event.