The stability of the acromioclavicular joint depends on a three-level anatomical defense system: Bony interlocking structure (the acromioclavicular joint surface forms a concave-convex matching shape) , static stability system (the four-dimensional tension network of the acromioclavicular ligament bears 82% of the initial anti-displacement load, and the coracoclavicular ligament complex provides vertical suspension function) , and dynamic stability system (the trape-deltoid muscle fascia generates dynamic compressive force Reaching 2.1 times the body weight during outreach. A pathological dislocation occurs when high-energy trauma interrupts ligament continuity (MRI shows that the Angle of conical ligament rupture is >25°) . There are significant differences in the stepwise treatment strategies based on the Rockwood classification: In types I-II, conservative treatment (dynamic brace fixation combined with biofeedback training) is adopted chiefly, while in cases of types IV-VI, surgical intervention is mainly required. For controversial type III dislocation, the failure rate of conservative treatment for manual workers reached 41.2%, prompting 56.3% of cases to choose early surgical intervention. Although the traditional clavicle hook plate technique can shorten the braking period through rigid fixation, it causes characteristic complications: unhooking, shoulder joint stiffness, intractable shoulder joint pain, acromial impact, subacromial osteolysis, etc. Persistent shoulder joint dysfunction (CMS<65) occurred in a few cases. In contrast, the single-incision double Endobutton loop plate technique achieved anatomical reconstruction. Its elastic fixation characteristic increased the CMS score to 84.7±1.8 three months after the operation (19.3% higher than the hook plate group, P=0.004) and reduced the incidence of complications such as acromial impact. However, the data of this group showed that the failure rate of the internal fixation device was 8%. A comparative study of 46 cases of Rockwood type III-IV (2020-2023) revealed the core contradiction: The Endobutton technique sacrifices the initial fixation strength while reducing mechanical complications. This discovery suggests that a new hybrid fixation system needs to be developed to enhance the fixation strength of the Endobutton.

This study conducted a retrospective cohort analysis to systematically compare the differences between the two surgical methods regarding surgical parameters, functional recovery, and complications.

This article aims to evaluate the clinical data of 46 patients with Rockwood type III and type IV acromioclavicular joint dislocation admitted to the Department of Orthopedics and Traumatology of Zibo Central Hospital from January 2020 to June 2023. We conducted a retrospective study on these patients. The same surgical team performed all surgeries. According to different surgical methods, 46 patients with acromioclavicular joint dislocation were divided into 23 cases in the single-incision double Endobutton loop plate internal fixation group, 12 in Rockwood type III, and 11 in Rockwood type IV. In the clavicle hook plate internal fixation group, there were 23 cases, including 13 of Rockwood type III and 10 of Rockwood type IV. The two groups' operation duration, incision length, and intraoperative blood loss were compared. The acromioclavicular distance (ACD) and coracoclavicular distance (CCD) before the operation, 1 month, 3 months, and 6 months after the operation distance, and the visual analogue scores (VAS) of the double-Endobutton plate internal fixation group and the clavicle hook plate internal fixation group at 1 month, 3 months and 6 months after the operation scale, VAS and Constant-murley functional score (CMS) were compared. The complications in the two groups were compared one year after the operation.

Both groups of surgeries were completed, and the follow-up time obtained was more than one year for both. The operation duration (49.00±3.84) min and incision length (45.29±8.16) mm in the double Endobutton loop plate internal fixation group were both shorter than those in the clavicle hook plate internal fixation group [ (67.63±5.14) min and (69.87±5.41) mm] , and the differences were comparable (P<0.05) . The intraoperative blood loss in the clavicle hook plate internal fixation group (81.65±5.05) ml was more than that in the double Endobutton loop plate internal fixation group (61.12±2.80) ml, and the difference was comparable (P<0.05) . At 1, 3, and 6 months after the operation, The VAS double Endobutton loop plate internal fixation groups [ (2.98±0.41) points, (2.37±0.29) points, (1.44±0.23) points] were all lower than those in the clavicle hook plate internal fixation groups [ (4.00±0.52) points, (2.80±0.42) points, (1.67±0.14) points] . The differences were comparable (P<0.05) . The Constant-Murley scores in the double Endobutton loop plate internal fixation group [ (73.43±1.83) points, (84.71±1.81) points, (88.24±1.58) points] were all higher than those in the clavicular hook plate internal fixation group [ (65.71±2.27) points, (79.30±1.99) points, (81.69±1.93) points There was a significant difference in , and the differences were comparable (P<0.05) . Different complications occurred in both the double Endobutton loop plate internal fixation group and the clavicle hook plate internal fixation group after the operation, with significant differences that were comparable (P<0.05) .

The dual Endobutton system achieves anatomical reconstruction through the dual mechanism of "suspension-tension band" and its dynamic fixation characteristics are more in line with the physiological kinematics of the acromioclavicular joint. Compared with the rigid fixation of the hook steel plate, the stress shielding effect is reduced. From the perspective of complications, the complications in the experimental group were mainly related to material properties (metal fatigue, interfacial frets) , while the complications in the control group were caused mainly by mechanical compression (acromial impingement syndrome) . Therefore, a type-oriented complication prevention system should be established. Due to the effect of the clavicle hook plate on local force application, we speculate that Endobutton should be given priority for patients with osteoporosis, and for those with high activity requirements, it is recommended to combine with enhanced suture techniques. The double Endobutton surgical method shows significant advantages in minimally invasive and functional recovery. Future research should focus on developing intelligent navigation systems to optimize the positioning accuracy of tunnels and improve the configuration design of steel plates through finite element analysis.