Background Despite the high prevalence of unstable distal radius fractures (DRFs), there is no consensus regarding the optimal method and treatment timing, especially for elderly patients with multiple associated injuries. Purpose This study aimed to compare the grip strength achieved with two different methods for definitive dynamic external fixation of DRFs in elderly patients with polytrauma operated on within the first 24 hours. Methods In this prospective randomized trial, 35 patients were assigned to undergo definitive external dynamic fixation of DRFs using the nonbridging (group A) or bridging (group B) method. The grip strength, range of motion (ROM), Disabilities of the Arm, Shoulder and Hand (QuickDASH) outcome measure, visual analog scale (VAS) score for pain, and radiographic characteristics were evaluated at 6 and 12 months. Results At 12 months, no significant between-group difference was observed with respect to grip strength. All patients showed results in the third or fourth quartiles. The mean ROMs were 96.94 and 96.38% and the mean QuickDASH scores were 3.53 and 3.85 in groups A and B, respectively. The VAS scores were 1.60 and 1.85 in groups A and B, respectively. The overall complication rates were 13.3 and 15% in groups A and B, respectively. Initial fracture reduction was maintained in 86.67 and 95% of the patients in groups A and B, respectively. Conclusions Both bridging and nonbridging external definitive dynamic fixation proved safe and reliable for the treatment of unstable DRFs in elderly patients with polytrauma. The grip strength results in both groups predicted the restoration of ability in elderly patients to perform activities of daily living independently.