Medial Clavicle Fractures

Relevant Anatomy

The clavicle is the first long bone to ossify. However, the epiphysis at the medial end of the clavicle is the last of the long bones to appear and is the last epiphysis to close. It does not ossify until 18–20 years of age. The epiphysis does not fuse with the shaft of the clavicle until age 23–25 years. Until then, the growth plate remains the weakest point and more likely to sustain a displaced physeal fracture than a true dislocation.

The medial part of the S-shaped clavicle articulates with the sternum through a saddle-shaped joint with little intrinsic bony stability. Concerning the osseous anatomy, in both the anteroposterior and superoinferior directions, the clavicle is thickest at its medial part and looks more like a square (on average 25 mm on a side).

The clavicle is stabilized to the sternum via the sternoclavicular joint capsule and the anterior and posterior sternoclavicular ligaments. The posterior sternoclavicular ligament is particularly thick and stout. Further stability is provided by the costoclavicular ligament at the inferior border connecting with the first rib and the interclavicular ligament at the superior border connecting with the contralateral medial clavicle.

Only the anteroinferior surface of the sternal end of the clavicle is covered by cartilage ( Fig. 4.1 ) and the clavicular articular surface is much larger than the sternal articular surface. There is also an intra-articular disc. Probably, as for meniscus in the knee, the function of the disc is to work as a shock absorber. Degenerative tears of the disc are commonly seen with aging and most of the time are asymptomatic in contrast to uncommon traumatic disc tears. ^,

Several muscles originate or insert on the medial clavicle. These include the clavicular part of the pectoralis major muscle, the sternocleidomastoid muscle, and the subclavius muscle.

In the case of a medial clavicle fracture, depending on the location of the fracture, any of these can act as deforming forces to displace the fracture and impede reduction. Typically, the lateral fragment is displaced anteriorly and inferiorly due to the pull of the pectoralis major muscle and the force of gravity on the upper limb while the sternocleidomastoid pulls the medial fragment superiorly.

Evaluation

A medial clavicle fracture is a rare injury, accounting for <5% of all clavicle fractures. They commonly occur in middle-aged men as a result of auto or motorcycle accidents. The high incidence of segmental fractures (9%) and chest trauma (49%) implies an association with high-energy trauma. These injuries, especially if nondisplaced or minimally displaced, are frequently missed during general clinical examination of the polytrauma patient, especially as more severe head, chest, and cervical injuries often coexist and can distract from the diagnosis. Furthermore, even if a standard trauma screening chest radiograph is taken, the overlapping shadows around the sternoclavicular joint and the medial clavicular metaphyseal cortices make diagnosis somewhat challenging even on standard radiographs. In the case of a hematoma, there should be a high suspicion of fracture. Even if displacement is visualized in the acute setting, it can be hard to distinguish between an anterior sternoclavicular dislocation and a medial clavicular fracture. When there is a suspicion of medial clavicle fracture, we recommend computed tomography (CT) scan for evaluation.

In children and young adults, fractures at the medial end of the clavicle are most commonly physeal separation. In contrast to adults, in which the lateral fragment displaces anteriorly, in this population, the lateral fragment can also displace anteriorly but much more commonly displaces posteriorly ( Fig. 4.2 ). When the lateral fragment is displaced posteriorly, this can cause dysphagia and/or dyspnea. Symptoms of mediastinal compression are a clear operative indication. Because the medial clavicular epiphysis is the latest bone to ossify, in patients under the age of 20, magnetic resonance imaging (MRI) or ultrasound can be helpful to distinguish between a physeal separation or a real dislocation. In younger patients without symptoms, physeal injuries may remodel but closer to skeletal maturity, even physeal injuries with significant displacement may benefit from treatment.