Clavicle shortening after fracture

                                        Dr. KS Dhillon

Introduction

Clavicle fractures are quite common. They account for 2.6% to 4% of all fractures. About eighty percent of clavicle fractures are located in the middle third of the clavicle [1]. These fractures primarily occur in the younger population with male dominance of about 70% [2].

The most common mechanism of injury is a direct fall on the shoulder. Fractures can also be sustained during sporting activities and motor vehicle accidents. 

About 69–82% of fractures occur in the midshaft of the clavicle, 12–26% in the lateral part, and 2–6% in the medial part [3]. Fractures of the medial and lateral parts are less common because the medial and lateral parts are firmly secured by strong ligaments and muscles, while the middle part of the clavicle lacks any strong attachments and thus is more vulnerable to a fracture. 

Due to the muscle and other soft tissue attachment, the lateral fragment displaces caudally, anteriorly, and medially, leading to angulation and overall shortening of the clavicle.

Regardless of the type of fracture, clavicle fractures have traditionally been treated almost exclusively non-operatively. Studies in the 1960s showed good functional results for conservatively treated midshaft clavicle fractures and a low nonunion rate compared to fractures treated by primary open reduction [3]. Several more recent studies, on the other hand, have reported opposite results with newer methods of fracture fixation 

[3], “which may have contributed to the 705% increase in operative treatment of clavicle fractures in Sweden between 2001 and 2012” [4]. The optimal treatment of clavicle fractures however remains a debated subject.

A recent Cochrane review by Lenza et al [5] showed that there is low-quality evidence that surgical treatment has no additional benefits in terms of function, pain, and quality of life compared with conservative treatment of clavicle fractures.

Displaced fractures of the clavicle that are treated conservatively often lead to shortening of the clavicle. There are several studies that have reported that shortening is associated with greater disability of the shoulder [6-9], whereas other studies have reported no such association [10-14].

Measurement of clavicle shortening

Clavicle fracture shortening was often measured on dedicated anteroposterior (AP) view of the clavicle or shoulder girdle [15].

Posteroanterior (PA) chest x rays have been found to be equally useful for the measurement of clavicle length [16]. 

Jones et al. [17] carried out a study and concluded that using unilateral radiographs of the fractured clavicle was insufficient for determining the true degree of fracture shortening. 

Computed tomography (CT) imaging of the clavicle has been regarded as the gold standard for measurement of the actual clavicular length [16] and an important modeling tool to establish clavicular morphology [18,19]. CT allows for imaging of the clavicle in multiple planes without projection abnormalities. Therefore, many believe that CT is a more reliable modality for evaluating clavicular length.

Most often clavicle length is measured, using a PA view of a chest radiograph. The clavicle length is the distance between two points placed on the center of the proximal and distal ends of the clavicle. The center is determined by choosing a point that is halfway between the superior and inferior aspects of the proximal end of the clavicle. The same is repeated for the distal end of the clavicle. The difference in length between the two sides provides the value of relative shortening.

For measurement of the clavicle length on CT, a clavicle-specific plane is created by orienting an oblique reconstruction through the center of the sternoclavicular joint proximally and the center of the acromioclavicular joint distally. As with X-ray measurements, the length of each clavicle is measured from the midpoint of the medial end of the clavicle to the lateral end of the clavicle.

Omid et al [15] carried out a study to compare the accuracy of clavicle shortening measurements based on plain radiographs with those based on CT reconstructed images of the clavicle. They found that measurement of clavicle length using AP plain radiographs is inaccurate. The measurements made on chest radiographs correlated poorly with those made on the CT, and this variability was significant. The reason for this variability can be explained by the fact that no radiographic projection captures the length of the clavicle in its oblique plane as can be done with a CT reconstruction. There was length overestimation and subsequent miscalculation of the true length of the clavicle. 

Radiographic measurements overestimated the clavicular length by a mean of 6.42mm to 8.22 mm which resulted in underestimation of clavicle shortening as compared to CT-based measurements. 

In the AP chest x rays, due to the greater distance between the clavicle and X-ray film, there can be greater projection artifact, amplification effects, and measurement errors due to positioning and rotation [16].

Impact of clavicular shortening

Clavicle fractures have traditionally been treated conservatively in the past. In nonoperatively treated patients, closed reduction of the fracture is difficult to achieve and to maintain and therefore is not attempted. A certain degree of clavicular shortening usually remains after union due to overlap of the fracture fragments.

There are several studies that have reported that shortening is associated with greater disability of the shoulder [6-9], whereas other studies have reported no such association [10-14].

Woltz et al [20] carried out a systematic review of the literature to find out whether clavicular shortening after nonoperative treatment of midshaft fractures affects shoulder function. There were 6 articles included in this systematic review based on the selection criteria. The studies were published between 2006 and 2015 and evaluated a total of 379 patients.  Five studies were retrospective and one was prospective. In four of the studies, determining the relationship between shortening and shoulder function was the primary aim. Follow-up was at least 12 months in all studies, with a mean of 4.5 years.

The reported mean shortening ranged from 9.2 mm to 25 mm. Three studies compared patients with a shortening of less than 20 mm with those having 20 mm or more shortening. In these studies, 19% of the study population had a shortening of ≥20 mm. 

The authors found that there is not enough evidence in the literature to show that shortening of a midshaft clavicle after a fracture is a risk factor for functional impairment.

The authors concluded that the existing evidence to date does not allow for a valid conclusion regarding the influence of shortening of the clavicle on shoulder function after union of nonoperatively treated midshaft clavicular fractures.

Conclusion

Fractures of the clavicle are common. Traditionally they have been treated conservatively without surgery. Conservatively treated fractures heal with some overlap leading to shortening of the clavicle. 

The gold standard for the measurement of clavicle shortening is a CT. Chest X rays can also be used to measure the clavicle length.

Shortening of the clavicle was believed to produce no functional disability. There are several publications that show that shortening of the clavicle produces no functional disability. However, in the recent past, there have been several authors who claimed that shortening of more than 2 cm is associated with shoulder dysfunction. Systematic review of the literature, however, shows that there is not enough evidence to show that clavicle shortening is a risk factor for functional impairment.

References

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