Abstract Objective To investigate the therapeutic effect of clavicle hook plate in acromioclavicular dislocation and distal clavicle fracture. Methods Forty-eight cases of acromioclavicular dislocation and distal clavicle fracture were treated with internal fixation of the clavicle hook plate by incision and reduction. The results were obtained at a follow-up of 10 months to 2 years after surgery, and the excellent rate of shoulder function was 100% according to Karlsson’s criteria. Conclusion The design of the clavicle hook plate conforms to the anatomical and biomechanical characteristics of the distal clavicle and the acromioclavicular joint, and the fixation is reliable. Keywords: clavicle hook plate; clavicle; acromioclavicular joint; fracture; dislocation The incidence of acromioclavicular joint dislocation and distal clavicle fracture is about 6% of the whole body fracture dislocation, and the effect of conservative treatment is not ideal. Our hospital used clavicle hook plate to treat such injuries from June 2003 to August 2006 with satisfactory results, which are reported as follows. 1. Clinical data 1. 1 General data Among the 48 cases, 33 were male and 15 were female, aged 18-69 years. There were 16 cases of acromioclavicular joint dislocation according to Tossy’s type, 4 cases of type II and 12 cases of type III; 32 cases of distal clavicle fracture according to Neer’s type, all of them were Neer type II. All patients had fresh fractures or dislocations without combined vascular and nerve injuries. The patient was placed supine with the affected shoulder elevated and the head tilted to the healthy side, and incision was made from the clavicle to the acromion to expose the distal clavicle and acromioclavicular joint, remove the soft tissue at the fracture end or the intra-articular fragmented cartilage disc, hold the bone clamp for temporary fixation after repositioning, insert the sharp hook of the plate under the acromion behind the acromioclavicular joint, press down the plate flat against the clavicle, drill holes in turn and fix it with 3.5mm screws on the The plate was drilled and fixed to the clavicle with 3.5mm screws. The torn acromioclavicular capsule, acromioclavicular ligament, trapezius, deltoid and surrounding fascia are repaired with sutures. The rostral collar ligament repair is not routinely performed. The incision is closed after checking the stability of the shoulder joint movement and fixation. After the operation, the affected limb was suspended by a triangular scarf for 1 week and then the shoulder joint was actively moved, and daily activities were performed after 3 weeks. 2. Results The 48 cases in this group were followed up for 10 months to 2 years after surgery, and there was no loosening of internal fixation or fracture displacement. The shoulder joint function was evaluated according to Karlsson’s criteria [1], and 42 cases were excellent and 6 cases were good. The excellent rate was 100%. Tossy type III acromioclavicular dislocation and Neer type II distal clavicle fracture are associated with complete rupture of the rostral collar ligament, and the proximal end is displaced posteriorly and superiorly by the pull of the sternocleidomastoid and trapezius muscles, and the distal end is displaced downward by the gravity of the upper limb and the pull of the pectoralis major, pectoralis minor, and latissimus dorsi muscles. The distal end is displaced inward by the gravity of the upper limb and the pull of the pectoralis major, pectoralis minor, and latissimus dorsi muscles, making it difficult to reset and maintain reset. 3.2 Characteristics of the clavicle hook plate The clavicle hook plate is designed according to the anatomical and biomechanical characteristics of the distal clavicle and the acromioclavicular joint, and is fully compatible with the “S” shape of the clavicle. The sharp hook of the plate inserted under the acromion and the body of the plate at the end of the clavicle form a lever, which generates a continuous and stable pressure at the distal end of the clavicle and both ends of the fracture, providing a stable and tension-free environment for the acromioclavicular and rostral ligaments and the surrounding soft tissues, improving the quality of ligament and soft tissue healing; moreover, the sharp hook passes outside the joint under the posterior acromion without damaging the joint, affecting the rotator cuff less and maintaining the micromotion of the acromioclavicular joint. The function of the acromioclavicular joint is maintained, and functional exercise can be performed early. (1) The hook plate is divided into left and right sides, and the length is from 3 to 6 holes, so the plate should be selected according to the side and type of injury, and 3 or 4 holes are generally chosen for acromioclavicular dislocation, and 3 screws are appropriate for the proximal end of distal clavicle fracture. (2) The entry point of the tip hook of the installed plate should be behind the acromioclavicular joint to fully expose the distal clavicle and the posterior edge of the acromioclavicular joint to ensure the correctness of the insertion point, and if necessary, intraoperative fluoroscopy of the C-arm machine to avoid insertion into the acromioclavicular joint cavity leading to collision with the humeral head and traumatic arthritis, and to prevent the tip hook from slipping out due to insufficient insertion length. (3) Plate pre-curvature is the main factor affecting the surgical result. The tip hook is partially inserted below the acromion, and special attention should be paid to the pre-bending of this part, otherwise it will lead to impingement of the shoulder joint during abduction; the length of the vertical part of the tip hook is not individually designed, too long will produce a jamming of the rotator cuff, too short makes the pressure of the tip hook on the acromion upwards too much leading to pain or even fracture. (4) The soft tissue and articular cartilage fragments in the joint should be removed during the dislocation of the acromioclavicular joint to avoid postoperative traumatic arthritis [3]; the fracture block of the distal clavicle must be fixed intraoperatively with screws on the hook plate to avoid postoperative activity between the fracture ends, resulting in delayed healing or non-healing of the fracture. 3, 4 Ligament repair Tossy type III acromioclavicular dislocation with complete rupture of the acromioclavicular and rostral ligaments and Neer type II distal clavicle fracture with complete rupture of the rostral ligament theoretically require ligament repair, but the rostral ligament is difficult to repair with satisfactory sutures. In our group of 48 cases, four cases were repaired with both sets of ligaments, and 44 cases were repaired with satisfactory repair of the joint capsule and acromioclavicular ligament without rostral collar ligament repair and reconstruction, and their results were excellent. Because of the good repositioning and durable and reliable fixation of the clavicle hook plate, the injured rostral collateral ligaments were repaired by natural alignment and scar formation [4]. We believe that it is not necessary to repair the rostral collar ligament, but the acromioclavicular capsule and the acromioclavicular ligament should be repaired as much as possible. Clavicle hook plate treatment of acromioclavicular dislocation and distal clavicle fracture has the advantages of reliable fixation, early functional exercise, few complications, and relatively simple operation, and is a form of internal fixation worth promoting.