Objective To compare the efficacy between hook plate combined with coracoclavicular ligament functional reconstruction by conjoined tendon transfer and single hook plate surgery in the treatment of Rockwood type Ⅲ and type Ⅴ acute acromioclavicular joint dislocations.Methods A prospective cohort study was conducted to analyze the clinical data of 37 patients with Rockwood type Ⅲ and Ⅴ acute acromioclavicular dislocations admitted to Jiangning Hospital Affiliated to Nanjing Medical University from October 2011 to April 2016.According to the random number method,the patients were divided into combined tendon and ligament reconstruction group (ligament reconstruction group,19 patients) and clavicular hook plate group (single plate group,18 patients).In the ligament reconstruction group,there were 14 males and five females,aged (47.0 ± 11.4) years,and there were 10 patients with type Ⅲ and nine with type Ⅴ.In the simple plate group,there were 12 males and six females,aged (45.0 ± 11.2)years,and there were 11 patients with type Ⅲ and seven with type Ⅴ.In the ligament reconstruction group,the acromioclavicular joint was reduced by clavicular hook plate,and the oblique ligament and the conical ligament were reconstructed by lateral half-inversion of the short head tendon of biceps brachii combined with tendon.The double-bundle functional reconstruction of coracoclavicular ligament was performed.In single plate group,hook plate was used to reduce acromioclavicular joint.The intraoperative blood loss,incision length,operation time,and visual analogue score (VAS) before operation and after 1 year follow-up were compared.Constant-Murley score and Karlsson score were used to evaluate the effect of operation.X-ray films were taken regularly to observe the reduction and maintenance of acromioclavicular joint dislocation.The complications were recorded.Results All patients were followed up for 17-24 months [(20.0 ± 1.7) months].There was no significant difference in intraoperative blood loss between the two groups (P ＞ 0.05).In the ligament reconstruction group and single plate group,the incision length was (13.4 ± 0.8) cm and (6.6 ± 0.7) cm (P ＜ 0.05);the operation time was (88.7 ± 8.3) minutes and (54.1 ± 7.3) minutes (P ＜ 0.05);the preoperative VAS score was (7.5 ± 0.9) points and (7.3 ± 0.7) points (P ＞ 0.05);the VAS at 1 year after operation was (2.1 ± 0.9) points and (3.8 ± 1.4) points (P ＜ 0.05).X-ray showed good reduction of acromioclavicular joint in ligament reconstruction group,with no loss of reduction occurred after removal of hook plate.In the simple plate group,loss of reduction,resorption of distal clavicle bone and bone fusion occurred after removal of hook plate.The Constant-Murley scores in the ligament reconstruction group and the single plate group were (89.5 ± 2.9) points and (79.6 ± 5.0) points respectively;the excellent and good rates of Karlsson score were 89.5％ (17/19) and 61.1％ (11/18) (both P ＜ 0.05),respectively.In the ligament reconstruction group,one patient complained of pain and swelling at the tendon.In the single plate group,loss of reduction occurred in three patients after removal of internal fixator;obvious subacromial osteolysis was seen in seven patients at 1 year after operation;and impingement sign was positive in nine patients at 1 year after operation.Conclusion The overall surgical effect of hook plate combined with coracoclavicular ligament functional reconstruction by conjoined tendon transfer is superior to single hook plate surgery in the treatment of type Rockwood Ⅲ and Rockwood Ⅴ acute acromioclavicular joint dislocations,though with longer operation time and bigger incision.