Cast-OFF 2: one week versus three to five weeks of plaster cast immobilization for non-or minimally displaced distal radius fractures, a stepped wedge cluster randomized controlled trial.

Objectives: Implementation of one week of cast immobilization followed by gradually increasing wrist mobilization for non- or minimally displaced DRF and comparison of the functional outcomes and pain scores with the usual care (three to five weeks of cast immobilization).

Methods: Design: A randomized stepped wedge cluster design, prospective cohort.

Setting: Academic and peripheral hospitals in level 1, 2, and 3 trauma centers.

Patient selection criteria: All patients between 18 and 85 years old with an isolated non- or minimally and nonreduced DRF were eligible for inclusion. Participating hospitals were randomized to transition from usual care (three to five weeks of cast immobilization) to one week of cast immobilization, following the stepped wedge design.

Outcome measures and comparisons: Patient characteristics, secondary dislocation, surgical treatment, visual analog scale (VAS), Patient Rated Wrist Evaluation (PRWE), Patient Reported Outcomes Measurement Information System Pain Interference (PROMIS-PI), Pain Catastrophizing Scale 4 (PCS-4), and patient satisfaction were compared between control, and intervention group at week 1, 3-5, 6, month 3, 6, and 12. A difference around 11 points on the PRWE scale was considered clinically significant.

Results: 402 patients were included (control n=197 vs intervention n=205, 267/135, female/male). There were no differences in age (53.7 ± 18.6 vs 53.3 ± 19.5, P = 0.27), sex (66% vs 67% female, P 0.44), dominant hand fractured (44% vs 53%, P 0.39), and type of fracture (39% vs 41% extra-articular, P = 0.44) After six weeks, the PRWE score showed no clinically significant differences (-4.5 [CI -12.9, 4.02], P = 0.30). No significant differences were observed for function, pain scores, and patient satisfaction between groups (all P > 0.05). Furthermore, there was no significant difference in secondary dislocation rate (control 1.5% vs intervention 1.0%, p=0.32, P = 0.32) and operation rate (control 1.5% versus 1.5% intervention P = 0.92).

Conclusions: This study compared one week of cast immobilization followed by gradually increasing wrist mobilizationto the usual care of three to five weeks for nonreduced DRF. No clinically significant differences in function, pain scores, patient satisfaction, secondary dislocation, and operations were observed. Therefore, one week of plaster immobilization can be safely recommended for the non- or minimally displaced and nonreduced DRF treatment.

Level of evidence: Level II. See Instructions for Authors for a complete description of levels of evidence.