Clavicle fracture

The incidence of clavicle fractures is 30-60 per 100,000 people, with a male to female ratio of approximately 2:1, accounting for 5% to 10% of all fractures and 44% of shoulder joint injuries. The clavicle is the earliest bone to undergo ossification in the human body, and its ossification begins in the fifth week of embryonic life, and it is the only long tubular bone that ossifies by means of intramembranous osteogenesis. The primitive ossification center is located in the middle of the clavicle and is responsible for the growth of the clavicle up to 5 years of age. There is a growing epiphyseal plate at each of the inner and outer ends of the clavicle, but often only the medial ossification center can be visualized by x-ray. The medial epiphyseal plate is responsible for 80% of the length growth of the clavicle, and its ossification center usually does not begin to appear until 13 to 19 years of age, and it does not fuse with the clavicle until 22 to 25 years of age. Therefore, when diagnosing sternoclavicular dislocation in young patients, it is important to differentiate it from medial clavicular epiphyseal injury.

Functional Anatomy

The clavicle is approximately straight when viewed anteriorly, but is S-shaped when viewed superiorly, curving dorsally and medially to the ventral side. Its cross-section changes along the long axis, with the outer 1/3 flattened to accommodate muscle and ligament pulling; the middle 1/3 becomes tubular, with a reduced diameter and a thicker cortex and denser bone than the rest, to accommodate axial pressure and tension and to protect the vascular nerves beneath it; the inner 1/3 is rhombic and is associated with the sternum and the first rib by strong ligamentous tissue (Figure 1). Anatomical studies have shown that the clavicle is weakest here due to the morphological variations in the middle and outer 1/3. In addition, it is located lateral to the subclavian muscle stop and lacks the protection of muscular ligaments, making it the most vulnerable site for fracture, as evidenced by clinical observations.

Mechanism of injury

For clavicle fractures in adults, the most common mechanism of injury for clavicle fractures was previously thought to be the result of a fall with the hand in the hyperextended position, but Stanley et al. found that this mechanism of injury accounted for only 6.3% of mid-clavicle fractures and 5.9% of distal clavicle fractures, and in all patients, the most common mechanism of injury came from direct forces acting on the shoulder joint The most common mechanism of injury in all patients is direct force on the shoulder joint, usually without significant displacement or with only mild displacement.

In the case of falls with the palm in the hyperextended position, the fracture is often caused by the impact of an external force secondary to the fall. Another type of fracture due to indirect violence is when an external force acts on the shoulder, causing the clavicle to impact with the first rib, resulting in the formation of a spiral fracture in the middle 1/3 of the clavicle. In addition, with the frequent occurrence of traffic accidents in recent years, due to the strong impact in the car accident, the seat belt forms a fulcrum of force in the shoulder, which often leads to a transverse or oblique fracture in the middle of the clavicle, which people call a seat belt fracture. Probably because the violence of the trauma is usually greater, this type of fracture is more prone to non-union than the usual clavicle fracture.

Treatment

Fracture of the middle clavicle：

Splint fixation:Splint fixation of clavicle fractures is still the "gold standard". Plates include the 3.5mm LC-DCP, 3.5mm reconstruction plates, LCP locking plates, and some special forms of plates. The advantages of splints include: compression of transverse fractures; fixation of oblique or butterfly fractures with tension screws combined with neutralizing splints; effective control of rotation; secure fixation of the fracture for the patient's daily activities; and the fact that splints usually do not need to be removed (if they must be removed until 12 to 18 months postoperatively).

Distal clavicle fracture：

The clavicle hook splint is an indirect fixation method, the advantages of which include easy placement of the internal fixation, more accurate maintenance of repositioning, no disruption of the acromioclavicular joint, and relative stability of the internal fixation without slipping into the surrounding tissues as with the traditional kyphotic pin.

Proximal clavicle fracture：

The literature reports that nonoperative treatment is preferred for this type of fracture, with cervical-wrist sling braking. Incisional internal fixation may be considered if there is vascular nerve injury, or if the fracture is displaced posteriorly causing the patient to have difficulty breathing or swallowing, or if there are no such symptoms but imaging reveals that the displaced fracture is impinging on a vital posterior structure and that repositioning is ineffective. If fixation is not possible, the proximal clavicle may be removed if necessary.

Complications

• No healing：Previous literature reported a non-healing rate of 0.9% to 4% for clavicle fractures, and a recent bulk case survey found that the actual non-healing rate is much higher than one might expect.

• Deformity healing: The traditional view is that deformity healing of the clavicle is only an aesthetic problem and that if there is non-healing after surgery, the result is better than allowing the deformity to exist. However, recent observations have shown that shortening of the clavicle of more than 15 cm often leads to pain and limitation of movement in the late stage. In addition, some scholars have proposed simple "clavicle shaping" in the treatment of deformity healing, but this method is not advisable. Removing only the protruding scab can make the clavicle thinner and greatly increase the risk of fracture, and since the deformity of the clavicle is manifested in three dimensions, "smoothing" the clavicle in the horizontal plane alone will not completely correct the deformity. Therefore, a more reliable approach is similar to the treatment of nonunion: removal of the excess bone scab as much as possible after incision, stabilization of the internal fixation and one-stage bone grafting. Of course, the patient must be informed of the risk of non-union before surgery.

• Vascular nerve injury:The likelihood of vascular nerve injury after a clavicle fracture is low in the early stages, and secondary injury does not usually occur due to displacement of the fracture because of the increased vascular nerve space after the fracture, while in the late stages, the growth of bone scabs may cause symptoms of entrapment. Once this occurs, surgical decompression is often required.

• Traumatic arthritis:Traumatic arthritis after clavicle fracture tends to occur in the acromioclavicular joint after fracture of the outer 1/3 of the clavicle, mainly due to the destruction of this joint by violence at the moment of trauma, and partly due to the fracture involving the articular surface. If closure is ineffective, the distal 1 cm of the clavicle should be resected, and intraoperative care should be taken to protect the rostral-clavicular ligament.

  
  

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