Surgical treatment of avulsion fracture around joints of extremities using hook plate fixation

Joints are surrounded by articular capsule, ligaments and tendons. Avulsion fractures occur when the capsule, ligaments or tendons are avulsed from the bone due to unexpected contraction of the muscles or mechanical force [1]. As reported, the contractile properties of muscle and the attachment of tendons and ligaments at both ends of bone collectively contributed to the muscle contraction, so unexpected contraction of the muscles could lead to avulsion fractures at the site of tendon or ligament attachment [2]. Most avulsion fractures were intra-articular fractures, while relatively small fracture fragments are commonly attached to the ligament and capsule, making the joint difficult to return to the normal anatomical position [3]. The conservative treatment often has a poor therapeutic effect on avulsion fractures around joints, easily leading to fracture nonunion, joint instability and joint adhesion [4]. There are several fixations used to treat avulsion fractures, mainly including screw fixation [5], percutaneous Kirschner wire (K-wire) fixation [6], bone grafting [7], and plating fixation [8]. Internal fixation using lag screws or absorbable screws is recommended to fix large fragments, while K-wire and stainless-steel wire fixation is used to fix small fragments in order to avoid fracture nonunion [9]. However, the stability of screw fixation was not sufficient to meet the requirement of early rehabilitation exercise for patients with osteoporosis [10]. K-wire and stainless-steel wire fixation also shows unfavorable outcome, such as poor stability of the joint, which increases the risk of internal fixation failure.

Recently, accumulating evidence has strongly implied that the hook plate fixation has the advantages of more stable fixation of the fragments regardless of the bone quality and high accurate reduction in fracture with small fragments in the treatment of avulsion fractures [11]. For example, Shin et al. [12] found that the hook plate fixation provided stronger fixation relative to a suture anchor for thumb ulnar collateral ligament (UCL) fracture-avulsions. Moreover, Mehling et al. [13] have reported the excellent outcomes of mini-hook plate treating for phalangeal fractures. Based on these findings, we proposed that the hook plate might be a compatible fixation instrument for treating avulsion fractures around joints.

The purpose of the present study was to summarize clinical data of patients with avulsion fractures around joints of the extremities treated with hook plate fixation. More importantly, it was our goal to assess the necessity of surgery, the flaw of the mainstream internal fixation as well as the specific characteristics and therapeutic outcomes of hook plate.

All the patients were healed within 3 months after surgery with stage I healing incision without vascular or nerve injuries. The mean duration of follow-up was 18.1 months (range from 12 to 24 months). The functional score of the affected limb was significantly improved 3 months after surgery (Table 2, p < 0.05). No fractures with dislocation or delayed union were found in all patients. In the last follow-up, 3 cases (average age 55) with avulsion fractures of the humeral greater tuberosity had shoulder joint adhesion and peri humeral inflammation, and the functional recovery of shoulder joint was poor. Other patients were scored excellent or good of the functional recovery results. The total excellent and good rate was 95%. In addition, no instability of joints, looseness of internal fixation or traumatic arthritis was observed. Mild joint fibrosis occurred in 5 cases. In the last follow-ups, the functional score of the affected limb was markedly greater than that in the 3-month follow-ups (Table 2, p < 0.05). Internal fixation was removed after one year of surgery in 35 patients. The follow-up data for functional scores at each site was shown in Table 2. Typical cases were presented in Figs. 2, 3, 4, 5 and 6.

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. [19] 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. [12] 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) [22].

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 [12]. 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.