PURPOSE For nonsurgical treatment of fractures of the proximal phalanges of the triphalangeal fingers, different dynamic casts have been described. The main principle behind these casts is advancement and tightening of the extensor hood, caused by a combination of blocking the metacarpophalangeal joints in flexion and actively flexing the proximal interphalangeal joints. In contrast to established treatment protocols using functional forearm casts, the Lucerne cast allows for free mobilization of the wrist joint. The purpose of the current multicenter study was to compare the results of conservative, functional treatment using 2 different methods, either a forearm cast or a Lucerne cast. METHODS Over a 2-year-period, a prospective, randomized, multicenter study was conducted at 4 hospitals in Switzerland. Clinical and radiological results of 66 consecutive patients having 75 extra-articular fractures of the proximal phalanges were recorded through a minimum follow-up of 3 months. Intra-articular and physeal fractures, pathological fractures, open fractures, concomitant injuries of the tendons or collateral ligaments, and accidents more than 7 days before presentation were excluded from the study. RESULTS Radiographically, there were no statistically significant differences between the 2 groups in terms of palmar apex angulation and radial or ulnar angulation. There were no differences in total active range of finger motion. Wrist joint motion at the time of cast removal was statistically superior in patients treated with Lucerne cast. However, there were no significant differences in wrist joint motion at 12 weeks of follow-up. CONCLUSIONS The clinical and radiological results achieved with the Lucerne cast are comparable to those of established treatment. Well-reduced, minimally angulated, or nonangulated fractures of the proximal phalanges of the fingers can be effectively treated using functional casts without immobilizing the wrist. TYPE OF STUDY/LEVEL OF EVIDENCE Therapeutic II.