Effectiveness of continuous passive motion in total knee replacement patients with slow rehabilitation under ERAS pathway

Background: Although we know routine use of continuous passive motion (CPM) has no clinical benefit on patients’ outcome after total knee replacement (TKR), the effect of CPM on patients with poor rehabilitation progress under ERAS (Enhanced Recovery after Surgery) pathway is unclear. We aimed to evaluate the clinical outcomes by using CPM in these patients under ERAS pathway. Methods: We performed a retrospective study for patients who had TKR done between 2017 and 2019 under ERAS pathway. Patients who were not able to reach 45 degrees of active range of movement (ROM) on postoperative day (POD) 3 would be reviewed to see if any CPM was used. Primary outcomes were the length of hospital stay and the active ROM upon discharge. Other outcomes were the active ROM in POD4 and the latest follow-up, pain score, and quadriceps power. Result: After exclusion, total of 68 patients were included in the study, with 30 were given CPM and 38 were not. Both groups had matched demographics. The study (CPM) group had significantly higher mean active ROM upon discharge (76.00 vs 68.42 degrees, p = 0.02) and longer hospital stay (7.3 vs 5.9 days, p =0.01). There were no significant effects on pain score, quadriceps power, and the active ROM in POD4 and the latest follow-up. Conclusion: For post TKR patients with limited rehabilitation progress under ERAS pathway, the use of CPM could attain better active ROM upon discharge with no adverse effect on pain control and quadriceps power, but at the expense of an increase in the length of stay.