Avulsion fracture around joints is a form of ligament or tendon injury, and is also a special type of intra-articular fracture [18, 19]. On the one hand, the traction of ligaments, tendons, or articular capsules increased the occurrence of displacement. On the other hand, soft tissues are often embedded in the broken end. These two points make the fracture reduction become difficult, increasing the incidence of nonunion and affecting the functional recovery of ligaments, tendons and joints [12, 13]. Additionally, patients with defects of articular cartilage or articular surface would suffer from arthritis or joint dysfunction. Commonly, conservative treatment and surgery are the two major treatments of avulsion fracture. However, conservative treatment often causes some complications, such as synarthrophysis, nonunion, joint instability, and arthritis, resulting in an unstable fixation and an unsatisfactory outcome. Therefore, most avulsion fracture is recommended to be treated with internal fixation in the early stage. Indeed, patients with avulsion fractures without displacement was suggested to receive surgical treatment to promote the functional recovery [13, 14]. For instance, Huang et al.  found that the anterior arthroscopic-assisted fixation was a simple and feasible alternative for treating PCL avulsion fractures.
At present, the commonly used internal fixation methods for avulsion fracture include screws, steel wires, K-wire tension band, suture anchors, sutures, straddle nails, and allogeneic bone nails, among which screw fixation is the most commonly used. The stability of screw fixation is reliable for larger avulsion fracture fragments, but for patients with osteoporosis, small fracture fragments, or severe comminution, it is easy to damage the bone fragments when drilling or screwing. Therefore, screw fixation is more suitable for avulsion fracture patients with large bone mass and without heavy osteoporosis [18, 20]. For comminuted fractures that cannot be fixed with screw, steel wires, K-wire tension band, and sutures can be selected. However, these operations need to be performed in the transitional zone between the fragment and ligament, which is inconvenient and relatively cumbersome. When fixing with fine stainless-steel wire, excessive tension will injure ligaments and damage fracture fragments.
The hook plate used in surgical treatment of avulsion fractures had several advantages as follows [1, 13, 21] It was established from AO special hook plate or 1/3 titanium plate, which was commonly used in fracture treatments. (2) The hook plates established a non-rigid fixation to maintain stability, allowing a longer period for retention of the implant. (3) Eccentric screws were implanted independent of fracture fragments through the hook plates for compress fixation. (4) The hook plates declined boring and cutting damages of fracture fragments in favor of bone union. (5) The hook plates were performed regardless of the size of ligaments, tendons and fragments. (6) It had wide indications, particularly for hand avulsion fracture. In addition, Shin et al.  compared the mechanical effects of the hook plate and the rivet fixation in the treatment of ulnar collateral ligament avulsion fracture of metacarpophalangeal joint, and the results showed that the stability and strength of the hook plate were better than the rivet. Our previous research compared hook plate with traditional method in the treatment of avulsion fracture of the olecranon, and found that all fractures healed. There was no significant difference in healing time and incidence of complications between the two groups (P > 0.05). However, the former was superior to the control group in terms of functional recovery and range of joint activity, and the difference was statistically significant (P < 0.05) .
In this study, 3 cases with avulsion fractures of greater tuberosity of humerus had shoulder joint adhesion and perihumeral inflammation, and the functional recovery of shoulder was poor. One reason is due to the high age of the patients (average age was 55). In addition, the patients did not actively cooperate with the treatment for early rehabilitation exercises because of their low requirements for shoulder joint function after the operation. Meanwhile, the hook is located above the greater tubercle, which may impact the acromion and affect shoulder joint activity. Therefore, anchor suture and fixation should be the first choice for avulsion fracture of greater tubercle of humerus. Our study was designed to evaluate the outcomes of the hook plate fixation for 60 patients with avulsion fractures around joints. All the patients performed early rehabilitation exercises and the incision healed well without complications, such as screw loosening, instability of joints and arthritis. The excellent and good rate of joint function recovery was about 95%, which was higher than traditional internal fixation . Nevertheless, hook plate fixation still had some limitations. Firstly, hook plate fixation cannot be used under arthroscope. Secondly, it was unsuitable for severe comminuted fractures and anterior cruciate ligament avulsion fractures. Consequently, we should choose the appropriate internal fixation method according to different clinical situations.
In conclusion, hook plate fixation has the therapeutic effect on treating avulsion fractures around joints with the advantages of reliable fixation, early rehabilitation after operation, high recovery rates of joint function, wide indications, and convenient uses.