The greater tuberosity of the humerus is the bony protrusion of the proximal lateral part of the humerus. It is the insertion point of the supraspinatus, subaspinatus and teres minor tendons. After the fracture of the greater tuberosity of the humerus, the fracture block is often displaced posteriorly and upward by the muscle pull, which easily causes acromial impingement syndrome and is often accompanied by rotator cuff injury. If the fracture is not properly reduced, the supraspinatus, subaspinatus or teres minor may be shortened. Muscle strength may also be weakened, which seriously affects the function of the shoulder joint [19]. In addition, the biomechanical test [20] showed that the deltoid force required for abduction of the shoulder joint increased from 116% to 127% when the greater tubercle fracture was displaced by 5-10 mm. While the abductive force increased by 29% when the fragment was displaced by > 1 cm, active surgical treatment should be used for humeral greater tubercle fractures with displacement over 5 mm. Hence, for the patients in this study, the average displacement of fracture blocks was 19.75 ± 2.05 mm (5-30 mm), and only surgical treatment could provide adequate fixation and accurate reduction of the fracture block, which is conducive to the recovery of normal anatomical structure and promotes the rapid recovery of shoulder joint function.
When selecting the optimal surgical fixation strategy for fractures of the greater tuberosity of the humerus, the deforming force caused by rotator cuff muscle elongation should be taken into account. The supraspinatus, infraspinatus and teres minor are inserted into the greater tuberosity of the humerus, and their coupling force plays a crucial role in the function of the shoulder joint. Ogawa et al. [21] reported that most fractures of the greater tubercle of the humerus (57%) involve the supraspinatus and supraspinatus joints, resulting in upward and backward displacement of the greater tubercle of the humerus in the same direction as the rotator cuff pull for a complete supraspinatus tendon, and note that posterior displacement is particularly important because it is often underestimated and delays treatment. On the other hand, Mutch et al. [16, 22] found that 20% of the fracture blocks of the greater tuberculum shifted downward, and in the study of Bahrs et al. [23], the displacement was up to 25.2%, which suggested that it might be caused by the direct downward force or the impact of the greater tuberculum with the acromion during extreme abduction of the upper limb. In addition, in the case of anterior dislocation of the shoulder, the shear force at the glenoid margin can also lead to greater tuberosity fractures. The suture bridge technique covers the fracture block with the high-strength thread at the end of the anchor, which can effectively disperse the shear force and torsion force of the suture line and obtain satisfactory suture and fixation effects. The network structure formed by the high-strength thread crossing is able to firmly fix the avulsion bone and rotator cuff. Lin et al. [24] reported superior supraspinatus muscle tension on the greater tubercle fragment. The fixation of the greater tubercle with an anchor through the rotator cuff was superior to that with two tension screws. The supraspinatus muscle can be reduced by 100% coverage of the supraspinatus, and the supraspinatus muscle can provide the maximum contact area, which increases the fixation strength of the fracture block and decreases gap formation. The double-row anchor bridge suture technique has been widely used in arthroscopic surgery. Compared with traditional surgical methods, it has certain biomechanical advantages for repairing rotator cuff injuries and fixing fractures of the greater tubercle [15]. Under arthroscopy turned into a double row of anchors, the suture bridge technology with a tail line will smash the humerus fracture piece for complete coverage of the greater tuberosity, provide anatomical repositioning, and anchor the minimally invasive open reduction with fixed line suture bridge technology. This procedure takes the same amount of time of as solid block of fracture fixation, reduces the use of outside anchor nails, saves cost, and reduces the operation steps, thereby shortening the operation time.
Although the bridge suturing technique has obvious advantages in the treatment of greater tubercle fractures of the humerus, arthroscopic surgery itself also has certain limitations, including complicated operations and longer operation times that will increase the potential risk of surgery; surgeons must have a higher learning curve [25]. It has also been reported that arthroscopic double-row anchoring is unlikely to adequately reduce and repair severely displaced fracture fragments and can even damage the rotator cuff [26]. Using minimally invasive open reduction with suture bridge technology can overcome the disadvantages of cancellous bone screw fixation and steel plate internal fixation, reduce the risk of implants fixed weakly or loosely, avoid secondary operations to remove the screw and plate internal fixation and decease the cost compared with arthroscopy. This technique is more beneficial to the good reduction of bone mass and the examination and repair of rotator cuff injury through limited incision and direct vision operations.
Recently, the minimally invasive open reduction and suture technique with suture anchors for the treatment of greater tubercle avulsion fractures of the humerus has achieved good therapeutic results and brought great benefits to patients. The advantages of this technique include: 1) less surgical trauma, fewer postoperative complications, and faster recovery of pain; 2) simple operation, no special equipment, all under direct vision operation; 3) suture anchors are more conducive to the reconstruction of original rotator cuff prints; 4) the suture bridge technique fixes the bone block at rotator cuff insertion on the surface in a multidirectional, overall and stable manner to the humerus head, forming a two-layer plane fixation of rotator cuff insertion, which is accurate and conducive to early functional exercise; 5) suture anchors can form planar multipoint stress fixation, which can disperse the stress, reduce the reduction and loss, and is conducive to the recovery of rotator cuff function; 6) suture anchors are suitable for the treatment of comminuted fracture of greater tuberosity or osteoporotic fracture; and 7) avoids secondary surgery to remove the internal fixation. However, this technique also has several limitations. Due to relatively small fracture fragments, it is difficult for hollow screws to fix avulsion fracture blocks, which are often located above the greater tubercle. The steel plate cannot choose the appropriate location, which leads to more complications and even fixation failure. However, the split fracture block is large, and it is difficult to maintain the stability of the fracture fragment only by suture bridge technology. The compression fracture block is relatively stable, and conservative treatment is generally adopted.
Several notes should be considered when using this technique. 1) When repairing the rotator cuff, the footprint area should be covered by 100% to provide more contact area while reducing local tension. In addition, the initial fixed strength can be increased to reduce the formation of intertissue space to promote fracture healing and thus enhance the strength of the repaired tendon. 2) For comminuted fracture or small fracture block, fixation with a wire anchor can be used to reduce the possibility of iatrogenic fracture caused by plate fixation. 3) For greater tuberous humeral fracture with a large fracture block, the anchor should be perforated 5-10 mm from the most lateral edge of the fracture block to prevent the anchor from being too close to the lateral edge of the large fracture block, causing iatric fracture, and to prevent the anchor from failing. 4) The threading position of the anchor suture line should be kept in the same plane, and the suture line should not be inserted between the bone blocks. 5) When the suture is fixed, the tightness should be moderate to maintain a certain tension on the rotator cuff but not be loose and affect healing.
Our study has some limitations. First, this retrospective study had no control group using other fixation techniques, such as locking compression plates or arthroscopic fixation. Second, the sample size was small, with only 16 cases and a follow-up time of no more than 2 years. Therefore, the next step is to continue to accumulate more samples and longer follow-up cases and to set up a control group using other treatment methods to evaluate the effect of minimally invasive open reduction and suture bridge techniques for the treatment of humeral greater tubercle fractures.