The purpose of this study was to evaluate the clinical and radiological results after arthroscopically assisted and image intensifier--controlled stabilization of high-grade acromioclavicular (AC) joint separations using the double TightRope technique with the first-generation implant. The double TightRope technique using the first-generation implant leads to good clinical and radiological results by re-creating the anatomy of the AC joint. Case series; Level of evidence, 4. Thirty-seven consecutive patients (4 women and 33 men; mean age, 38.6 years) who sustained an acute AC joint dislocation grade V according to Rockwood were included in this prospective study. The Subjective Shoulder Value (SSV), the Constant Score (CS), the Taft Score (TS), and a newly developed Acromioclavicular Joint Instability Score (ACJI) were used for final follow-up. Bilateral stress views and bilateral Alexander views were taken to evaluate radiographic signs of recurrent vertical and horizontal AC joint instability. Twenty-eight patients (2 women and 26 men; mean age, 38.8 years [range, 18-66 years]) could be evaluated after a mean follow-up of 26.5 months (range, 20.1-32.8 months). The interval from trauma to surgery averaged 7.3 days (range, 0-18 days). The mean SSV reached 95.1% (range, 85%-100%), the mean CS was 91.5 points (range, 84-100) (contralateral side: mean, 92.6 points), the mean TS was 10.5 points (range, 7-12), and the ACJI averaged 79.9 points (range, 45-100). The final coracoclavicular distance was 13.6 mm (range, 5-27 mm) on the operated versus 9.4 mm (range, 4-15 mm) on the contralateral side (P < .05). Radiographic signs of posterior instability were noted in 42.9% of cases. Patients with evidence of posterior instability had significantly inferior results in the TS and the ACJI (P < .05). Neither coracoid fractures nor early (within 6 weeks postoperatively) loss of reduction due to tunnel malpositioning or implant loosening was observed. The combined arthroscopically assisted and image intensifier--controlled double TightRope technique using implants of the first-generation represents a safe technique and yields good to excellent early clinical results despite the presence of partial recurrent vertical and horizontal AC joint instability.