PURPOSE: Fragility fractures of the pelvis (FFPs) type IIIa in the Rommens classification include unilateral iliac fractures as well as pubic rami fractures. We devised a new, less-invasive fixation technique to achieve increased stability for FFPs type IIIa. The aim of this study was to describe this procedure and report the preliminary clinical results. METHODS: A total of 14 geriatric patients (> 60 years old) who sustained FFP type IIIa caused by low-energy trauma were surgically treated with interdigitating screw fixation including a trans-pubic screw in a retrograde manner and two trans-iliac screws from the anterior inferior iliac spine toward the posterior inferior iliac spine. All iliac fractures were displaced with external rotation, and closed reduction was performed. Percutaneous screw fixation, in which fully threaded screws were in contact with each other, provided stable fixation allowing early mobilization. RESULTS: A median decrease in pain levels by post-operative day two was 4.5 compared with pre-operatively using a numerical rating scale. While full weight-bearing was allowed from four weeks post-operatively in the initial five patients, immediate full weight-bearing was instructed as tolerated for the subsequent nine patients. No complications were encountered during the peri-operative period. At the final follow-up, all fractures were united without fixation loss, screw dislodgment, or hardware failure. CONCLUSIONS: This procedure of closed reduction and interdigitating screw fixation for FFP type IIIa appears to represent a safe, reliable technique. Our experience suggests that interdigitating fixation for FFP type IIIa is effective for relieving pain and promoting early mobilization in elderly patients.