<p class="abstract">Treatment of acromioclavicular (AC) joint separation is controversial. Rockwood type I, II, III AC joint injuries generally treated conservatively. In the literature there is various treatment options described for treating type IV - VI injuries with good and poor outcome but no single gold standard method. Rockwood type IV - VI AC joint separation treated with internal splint technique by passing Merselene tape through drill hole at lateral end clavicle, passing it under coracoid process and tied it after reducing vertical displacement of AC joint. Simultaneously horizontal displacement corrected and Merselene tape passed through drill hole of acromian process and tied. Endobuttn supports Merselene tape at superior aspect of clavicle. This study was conducted between April 2015 to March 2019 in KPC Medical College and hospital, Kolkata after taking ethical committee permission. 20 patients undergo surgical fixation of type IV-VI AC joint separation within 3 weeks of injury. Outcome of clinical and radiological parameter assessment was at 6, 12, 24 weeks. Male female ratio was 7:3. Mean age 38.2 years, abduction was less than 100 degree in 2 patients at 6 months follow up due to inadequate compliance to physiotherapy. Other patients develop full Range of motion (ROM) and power of shoulder muscle 5/5. No cosmetic deformity except one painful scar. No postoperative displacement in alignment in Anteroposterior (AP) and axillary lateral view. This technique of interal spilint construct reduces need for rigid implant and biological procedure for acute AC joint dislocation though having excellent fixation strength, good reduction in both coronal and sagittal plane for proper healing of AC and Coracoclavicular (CC) ligaments.</p>