Background The dislocation of acromioclavicular joint is a common injury clinically. This study is to investigate the treatment of acute acromioclavicular joint dislocation (Rockwood type Ⅲ) and compare the clinical effect of two different ways of coracoclavicular ligament reconstruction.Methods We select the patients with fresh Rockwood type Ⅲ to V dislocation of acromioclavicular joint from January 2008 to June 2013. After randomization, 16 cases received the reconstruction of coracoclavicular and acromioclavicular ligament arthroscopically with semitendinosus tendon (autogenous group). Among them, 12 were males and 4 were females, aged 16-62 years old, the average age is 39.8 years old. They were followed up for 9-39 months, the average follow-up was 25.6 months; 13 cases underwent the reconstruction of coracoclavicular ligament with the double Endobutton plate and Ethibond suture (Ethibond suture group), including 9 cases of male, 4 cases of female, aging from 19 to 57 years old, the average age is 36.5 years old, were followed up for 12-35 months with a mean follow-up of 19.6 months. The reason of injury: 12 cases of traffic injuries, 9 cases of sports injury, 4 cases of fall, bruise in 2 cases and 2 cases of other injuries. The time between injury to operation was 3-11 d, averagely 6 d. 8 patients were accompanied by SLAP injury of shoulder joint (5 cases of autologous ligament group, 3 cases of Ethibond suture group), 3 patients were accompanied by rotator cuff injury (1 cases of autologous ligament group, 2 cases of Ethibond suture group). 2 patients were combined with glenohumeral joint cartilage injury (1 case of autologous ligament group 1 case, 1 case of love help group), 2 patients were combined with Bankart injury (both in autologous ligament group), 1 patient was combined with glenoid fracture (Ethibond suture group). The age, sex, cause of injury, injury side and time from getting injured to operation of the two groups are without significant differences (P>0.05). Autologous ligament group arthroscopic semitendinosus tendon reconstruction of coracoclavicular ligament coracoclavicular ligament.All patients underwent operation under general anesthesia with endotracheal intubation. Patients were placed at 75°beach chair position. Bony landmarks were marked. The ipsilateral semitendinosus tendon was harvested first. Glenohumeral examination was first done through posterior viewing portal. Then the under surface of coracoid was exposed by shaver. Then establish the bone tunnel of clavicle, basal part of coracoid and acromial, transplant and fix the grafted tendon, wash the wound, suture the wound layer by layer. Ethibond suture group arthroscopic double Endobutton plate and Ethibond reconstruction of coracoclavicular ligament.The arthroscopic explosion and tunnel reconstruction is the same with the group mentioned above, use double Endobutton plate and Ethibond suture to reconstruct coracoclavicular ligament. Make sure the button completely stuck in the upper surface of the coracoid clavicle and underlying surface, abduct the shoulder joint, press the clavicle to get the acromioclavicular joint reduced, tighten Ethibond tail and fix the knot, close the wound.Two groups of patients were immobilized by neck wrist sling for 6 weeks. The immediate postoperative activity of elbow and wrist joint were demanded, shoulder joint passive exercise beginning at 2 weeks, then start the shoulder joint initiative and resistance strength training after 6 to 8 weeks. After 6 months the patients were allowed to engage in some contact sports activities. Through clinical examination, X-ray and CC-Dist measurements, then calculate the improvement rate, (CC-Dist value: the vertical distance between coracoid plane and the subclavian plane on the shoulder joint radiograph) and the Constant score was used to evaluate the curative effect. The Constant score, composed of the following 8 parts: the shoulder pain (15 points), daily activities (20 points), range of motion of the shoulder joint (40 points) (external rotation, internal rotation, abduction, flexion, each 10 points), strength test (25 points), wherein the objective score accounted for 65%, subjective scores accounted for 35%. The higher total score is, the better function the shoulder joint has. Excellent: ≥90; good: 80~89; general:70-79; poor ≤70. All the data were analysed by SPSS 19.0 statistical software. The imaging measurements, postoperative pain and functional scores were compared for the treatment group. Use t test or χ² test data to analysis statistically, the difference was statistically significant when P＜0.05.Results 29 patients obtained a 1 to 4 years (mean 2.5 years) follow-up. At last the improvement rate of the Constant score of autologous ligament group and Ethibond suture group were 47.31% and 47.01%, with no significant difference between them (t=0.136,P=0.893). The improvement rate of CC-Dist value of the Autologous ligament group and Ethibond suture group were 38.51% and 43.16%, there was an significant difference between the two groups (t=-2.895,P=0.007).Postoperative complications: two patients had a slight loss of reduction of the acromioclavicular joint. The autograft ligament group is more severe than the Ethibond suture group. Among them there were 4 cases of the autologous ligament group, 3 cases of the Ethibond suture group. The 4 patients of the autologous ligament group were satisfied with the appearance and function. The 3 patients were not significantly abnormal, but 2 patients complained a tightness of the shoulder and a soreness discomfort of the upper limbs.Conclusions The arthroscopic reconstruction of coracoclavicular and acromioclavicular ligament with semitendinosus tendon and the reconstruction with double EndoButton plate and Ethibond suture could improve the function of the shoulder joint, both the two have different advantages.