Accounting for 9% of all shoulder injuries, acromioclavicular ligament injury is a common sport injury of shoulder joint. Clinically, it is often manifested with acromioclavicular dislocation. For the patients with Rockwood type I and type II acromioclavicular joint dislocation of less severe damage degree, satisfactory result can be achieved through conservative treatment. However, patients with severe acromioclavicular joint dislocation such as Rockwood type IV and type V and some Rockwood type III with high exercise level requirements, surgery is usually required. Traditionally, the treatment of acromioclavicular joint dislocation is mainly based on open reduction and internal fixation or ligament reconstruction. However, the complications such as reluxation, joint pain, and even iatrogenic rotator cuff injury are common. In 2010, French arthroscopist Boileau introduced the research of arthroscopic modified Weaver-Dunn technique combined with coracoclavicular ligament reconstruction for the treatment of chronic acromioclavicular joint dislocation. This technique provided a new idea based on its advantages of minimal trauma, fast recovery, effective outcome, etc. However, the longtime of arthroscopic surgery and the difficulty of surgical technique make it not suitable for young doctor or primary resident. Therefore, we tried arthroscopic coracoclavicular fixation combined and modified Weaver-Dunn with minimal incision procedure for the treatment of chronic acromioclavicular joint dislocation and explored its therapeutic efficacy.

1. Reseach object: From March 2016 to March 2017, the patients with chronic acromioclavicular joint dislocation (Rockwood Type III, IV and V) were admitted and treated in the department of Joint & Osteopathy Surgery, Shanghai Changhai Hospital. Inclusive criteria: (1) Clarified history of trauma with ineffective conservative treatment of 3 months; (2) Those with routine postoperative follow-up and functional exercise for at least 6 months. Exclusive criteria: (1) Combination of other shoulder joint injuries that require surgical treatment; (2) Patients with acute acromioclavicular joint dislocation.8 male patients were included in the study with an average age of 38.4 (22-53) years. Five cases had the dominant side affected, and three cases had the non-dominant side affected. Causes of injury: 2 cases of traffic accident and 6 cases of trauma. 2. Preoperative preparatio:The main purpose was to determine the dislocation type and whether there was a combined injury. In addition to routine preoperative examination, the shoulder X-ray film of anteroposterior view was also required. The X-ray film of stress position was further required in some of the Rockwood type III patient to distinguish from the Rockwood type II patient. In addition, the X-ray film of the outlet view of supraspinatus, shoulder ultrasound and MRI could be used to exclude the combined lesions such as acromial impingement syndrome and rotator cuff injury. 3. Operative methods:The operation was performed under general anesthesia. The patient was placed in beach chair position and routinely disinfected and draped. The anatomical landmarks and surgical approaches were determined as follows: the conventional posterior approach (P) , the anterolateral approach (AL) for observation, the lateral approach (L) for acromioplasty, the anteromedial approach (AM) for coronoid base exposure and the longitudinal minimal incision of 3 cm on distal clavicle.Coracoid exposure: Firstly, the conventional approach was established to insert an arthroscopy for glenohumeral joint exploration. The anteromedial approach was made 1 cm outside coracoid, and the radiofrequency (DePuy Mitek, Raynham, MA) was placed in rotator interval to remove part of the joint capsule and to expose coracoid. The camera was then turned to subacromial interval to establish the anterolateral and lateral approaches. The bursa was cleaned with shaver and radiofrequency to expose distal clavicle, coracoid process, acromion and joint tendon. (1) Acquisition of acromiocoracoid ligament. As the anterolateral acromial angle and coracoid ligament were fully exposed, the attachment point of coracoid ligament was penetrated with a PDS suture for standby application. The size of fragment was designed to be cut. The osteotomy boundary was marked with radiofrequency, and then the fragment with acromioclavicular joint was intercepted with abrasive drilling (Smith & Nephew Endoscopy) . Attention should be paid that the size of fragment should not be too large (approximately 5×5×7 mm) . (2) Distal clavicle resection and coracoclavicular fixation. A longitudinal incision of 3-4 cm was made on the surface of distal clavicle and 3 cm medial to acromioclavicular joint. The attached deltoid and trapezius fascia were peeled off to reveal the bone surface above distal clavicle. At this point, the clavicle was pressed down by the assistant, and the elbow joint was pushed upward for primary reduction. If the reduction was difficult, distal clavicle resection could be performed first. The clavicle was poked for resection of 8-10 mm with rongeur or oscillating saw, and the clavicular medullary cavity was debrided and enlarged. If the primary reduction was successful, the drilling and thread of loop of coracoid and clavicle could be completed first, and then the distal clavicle was removed. One end of the AC guide (Arthrex) was placed at the incision approximately 4 cm medial to AC joint, and the other end was placed at the base of coracoid process under arthroscopy. The AC joint could be temporarily fixed with a Kirschner wire that penetrated from the lateral side of acromion as required. The holes were drilled with a 2.4 mm K-wire through the guide. Attention should be paid to control the speed and strength to avoid damage to the nerve while drilling, and then the 4.0 mm hollow drill was used to expand the dual cortex of clavicle and coracoid along the Kirschner wire. Once the Kirschner wire was removed, a PDS suture was introduced along the hollow drill from clavicle tunnel to coracoid tunnel. As the drill was pulled out, the distal end of PDS drill was taken out from AM tunnel. The TightRope (Arthrex) was introduced into subcoracoid through the PDS line. The position of TightRope was determined under arthroscopy. The length of loop was shortened by alternately pulling of the sutures, and the reduction of AC joint was completed under direct vision and confirmed under fluoroscopy. The pulled-out sutures were fastened to the upper surface of clavicle with six and a half knots in the small incision. Under direct vision, a 2.5 mm Kirschner wire was used for drilling approximately 1 cm distal to the clavicular tunnel inside the small incision, passing only single cortex above clavicle. In step 1, The PDS line was passed through coracoclavicular ligament out of distal clavicular medullary cavity. Two non-absorbable high-strength sutures were inserted into the reversal holes of TightRope above clavicle, and the PDS suture was replaced by the high-strength sutures with lead technology. The replaced sutures were knotted for fixation. Since then, the coracoclavicular ligament with small fracture fragment was fixed in clavicular medullary cavity. This operation was beneficial to the strengthening of coracoclavicular gap. Finally, the acromioclavicular joint capsule was folded and sutured to further fix AC joint. (3) Incision closure. The dissected fascia of deltoid and trapezius were closed as much as possible, and attention should be paid to the soft tissue covering of TightRope and the knots above clavicle.4. Postoperative care and rehabilitation: The affected extremity was immobilized with shoulder-elbow sling for 3-4 weeks. During this period, the pendulum exercise was allowed, and the use of the distal limb was encouraged to complete most of the daily life activities and prevent the occurrence of elbow joint stiffness. Driving or heavy lifting should be avoided in the first 2 months, and anti-resistance training was conducted 2 months later. Over-head or confrontational movements were allowed 6 months after the operation. 5. Postoperative follow ups and evaluation:The shoulder joint radiographs of anteroposterior view were taken in the postoperative 1^st, 3^rd, 6^th and 12^th months to evaluate the reduction of acromioclavicular joint. The mobilities of shoulder anteflexion, external and internal rotation, and whether there was acromioclavicular joint tenderness were recorded through physical examination. The loss of acromioclavicular joint reduction was evaluated by comparing the difference value between the immediate and the last follow up. The shoulder joint function was evaluated using visual analogue score (VAS) and University of California Los Angeles (UCLA) rating system.

Within 1 month after surgery, the patients mainly complained about shoulder pain. Only 1 patient had mild tenderness in the operation area, and the excellent and good rate was 100%. All patients had normal passive motion but limited active motion compared with those of the healthy side, but the results were significantly better than those before. No upward displacement was observed at clavicular end under fluoroscopy after the operation. During the follow-ups of the 3rd and 12th months, the shoulder X-ray film and 3D CT showed the reduction of acromioclavicular region and the good attachment of plates on clavicle and coracoid process. One case of Rockwood type V injury was satisfied with the horizontal reduction of acromioclavicular joint after the surgery. The difference value of coracoclavicular gap between the immediate follow-up and the last follow-up was (0.41±0.26) mm, and the loss rate of acromioclavicular joint reduction was low with effective fixation. The VAS score decreased from 4.57 points to 2.88 points 1 year after the operation, and the UCLA score increased from preoperative (138.7±20.5) points to postoperative (173.6±11.3) points. The pain and postoperative function were significantly improved.

The combination of coracoclavicular elastic fixation and Weaver-Dunn ligament reconstruction, arthroscopic assisted coracoclavicular suspensory fixation and modified Weaver-Dunn procedure is simple and effective in treating chronic acromioclavicular joint dislocation without remarkable reduction loss. With low technical requirement for operator and short learning curve, it is beneficial to the extensive implement of this surgery. This technique can adapt to the early rehabilitation and the recovery of shoulder joint mobility, which helps the patient to quickly return to life or work.