Relative motion orthosis

The relative motion orthosis is a static splint that positions the metacarpophalangeal joint of an injured digit in fifteen to twenty degrees of hyperextension relative to the uninjured neighbours. Through the juncturae tendinum the splint transfers extensor force from the repaired tendon to the adjacent intact tendons, permitting the patient to mobilise the digit actively from the early post-operative days without straining the repair. Originally described by Howell, Merritt and Robinson within the Immediate Controlled Active Motion protocol, the orthosis is now supported by RCT-level evidence in zones V and VI extensor repairs and is the contemporary default for those repairs.