The treatment of acromioclavicular (AC) joint dislocation is mainly based on the Rockwood classification. For acute acromioclavicular joint dislocations severer than Rockwood type III, surgical treatment is often required. The Rockwood type V injuries are common, but the surgical treatment methods are controversial. The common surgical procedures include clavicular hook plate. In 2007, Struhl reported the first case of using loop plate Endobutton device for treatment of AC joint dislocation in open surgery. Several scholars have also used double-loop to fix the AC joint dislocation under arthroscopy, and achieved satisfactory results. The Endobutton plate could be confirmed located at the base of coracoid process under arthroscopy, which was relatively safer compared to open surgery. Not only that, arthroscopy can also diagnose and deal with other problems. However, the fixation methods are numerous, including double-loop fixation, four-loop fixation and triple-loop fixation, and the more commonly seen are double-loop and four-loop fixation. The efficacy of double-loop fixation versus four-loop fixation has not been compared.

This study aims to evaluate and compare the efficacy of four-loop fixation through double bone tunnels versus double-loop fixation through single tunnel for treatment of acute AC joint dislocation of Rockwood type V.

We retrospectively reviewed the charts of patients with acute AC joint dislocation of Rockwood type V who had undergone arthroscopic double-loop fixation through single bone tunnel and four-loop fixation through double bone tunnels from May 2010 to May 2016. Eighty-two patients were included and divided into two groups according to different fixation types with 41 cases in each group. The patients were followed up for 2 years, and the visual analog scale (VAS) score, time of return to activities, number of patients return to activities, Constant-Murley scores as well as Karlsson were recorded as well. The Space between the coracoclavicular (CC) joint and AC joint was evaluated by imaging.

The average CC joint and AC joint distances in the double paired Endobutton (DPE) group were significantly smaller than those of the single paired Endobutton (SPE) group in the last follow up within two years after operation (P<0.05) . The average AC and CC distances in the healthy shoulder joints were significantly smaller than those of the affected joints in the SPE group (P<0.05) . However, these values were not significantly different from those of the affected joints in the DPE group (P>0.05) . In the last postoperative follow-up, the pain of the affected limb was significantly reduced in both groups, and there was a significant difference between preoperative and postoperative VAS scores, while there was no significant difference between the two groups.The time of returning to exercise was significantly shorter in the DPE group than in the SPE group, and the number of patients returning to exercise was significantly more than that in the SPE group. The Constant scores and Karlsson scores were significantly higher in the DPE group than in the SPE group, and the difference was statistically significant (P<0.05) . The complications in the DPE group were less than those in the SPE group.

Compared with the SPE group, the DPE group achieved better outcome with less complications in the treatment of acute AC joint dislocation of Rockwood type V under arthroscopy.