Elsevier

World Neurosurgery

Volume 109, January 2018, Pages e305-e312
World Neurosurgery

Original Article
Reappraisal of Neonatal Greenstick Skull Fractures Caused by Birth Injuries: Comparison of 3-Dimensional Reconstructed Computed Tomography and Simple Skull Radiographs

https://doi.org/10.1016/j.wneu.2017.09.168Get rights and content

Objective

The most common birth-associated head injuries during vaginal delivery are cephalhematomas and subgaleal hematomas. Cranial injuries are rarely encountered. The neonate cranium is soft and pliable, and greenstick skull fractures (GSFs) are expected to be more frequent than linear or depressed fractures, but they are extremely difficult to detect with simple skull radiography. As a result, no reports have been issued on this topic to date. Recent reports suggest that technological advances in 3-dimensional (3D) computed tomography (CT) have successfully enhanced the diagnostic accuracy for cranial fractures. The authors researched the types and characteristics of GSFs and the diagnostic accuracy of 3D CT for cranial fractures in neonates.

Methods

The simple skull radiographs and 3D CT images of 101 neonates were retrospectively evaluated and compared with respect to diagnosis of cranial fractures, and skull GSFs were classified on the basis of 3D CT findings into 5 types depending on multiplicity and location.

Results

3D CT detected 88 cases of cranial fractures, that is, 89 GSFs, 4 combined GSFs and linear fractures, and 3 combined GSFs and depressed fractures. The diagnostic rate of 3DCT was 91% and this was significantly higher than the 13% rate of simple skull radiographs (P < 0.001).

Conclusions

GSFs rather than linear fractures were found to account for most cranial injuries among neonates. The diagnostic accuracy of 3D CT was considerably superior than simple skull radiography, but the high radiation exposure levels of 3D CT warrant the need for development of a modality with lower radiation exposure.

Introduction

The incidence of major birth trauma ranges 1.0–11.7 in every 1000 live births, and the most common type of injury is cephalhematoma (56.6%).1, 2 Skull fractures account for only 0.01%–0.1% of major birth trauma cases.1, 2, 3, 4 Linear skull fractures are more common than depressed skull fractures in children, whereas depressed skull fractures are more common than linear skull fractures in neonates because of birth trauma.5 However, this conclusion may be incorrect because linear skull fractures are not easily observed with simple skull radiographs or 2-dimensional (2D) computed tomography (CT).2 Given these diagnostic limitations, few reports have claimed linear skull fracture frequencies of up to 10%–12% among all live births.2, 5, 6

Greenstick skull fractures (GSFs) are incomplete fractures that are encountered in the soft and pliable bone of pediatric patients, whereby the bone bends under the influence of the applied force and the outside layer, but not the inner layer, of bone is fractured.7, 8 These GSFs usually transpire in the long bones of children, but they can also occur in flat bones.9, 10, 11 However, in the incompletely ossified neonatal skull, gradual pressure on skull bones would likely bend rather than break bones and cause GSFs rather than linear fractures. However, GSFs in the neonatal skull are extremely difficult to observe with simple skull radiography, and probably for this reason, no such reports in the literature have been issued to date.

In the past, 3-dimensional (3D) CT required long scan times and relatively wide scan intervals, which adversely affected resolution. On the other hand, the recently developed 16- or 64-channel multidetector CT machines allow faster scanning and postscan processing techniques of scan distance and direction, and thus can be used to produce 2D or 3D multiplanar reconstructions.12 These technological advances have assisted in further continued improvements in the diagnostic accuracy of CT, and they have contributed to our understanding of lesions pertaining to cranial morphology, vascular patterns, and ventricular structures. In particular, 3D imaging allows linear, depressed, and diastatic skull fractures to be observed clearly. In addition, it has enhanced diagnostic accuracy because it enables basal skull fractures to be directly visualized.13, 14, 15, 16, 17, 18

Therefore, there is a need to determine the role of 3D CT in the assessment of neonatal cranial injuries, such as cranial fractures sustained during birth, especially with respect to GSFs. In this retrospective study, we studied the types and characteristics of GSFs as diagnosed with 3D CT, and compared the diagnostic accuracies of 3D CT and simple skull radiography.

Section snippets

3D CT Findings of Skull GSFs

The authors discovered a parietal lesion of the cranium involving a fracture of the incomplete outer table of the parietal bone in the operating field, which appeared as diffuse, amorphous, overlapping, tear-drop shapes of low-density bone defects on preoperative 3D CT in 2 neonates who were undergoing surgery for an epidural hematoma. Considering these observations, we suggest that incomplete outer table fractures observed as diffuse, amorphous, overlapping, teardrop shapes on 3D CT images can

Birth Skull Fractures on 3D CT Images

In the 101 neonates, 3D CT findings resulted in a diagnosis of GSFs in 89, linear fractures in 4, and depressed fractures in 3 neonates (Table 1). On the 3D CT images, GSFs were well visualized because of their lower density compared with normal bone. Low-density changes of fractures observed on 3D CT images were not affected by the presence of subgaleal hematomas or cephalhematomas, as hematomas were clearly distinguishable from fractures.

Of the 89 GSF neonates, GSFs involved the left side

Skull Fracture as a Birth Injury

During vaginal delivery, the fetal head is compressed while passing through the birth canal, causing pressure along the transverse axis to compensate for the shortened anteroposterior distance, which can result in parietal skull fractures, and along the longitudinal axis which increases the rostrocaudal distance and can result in injury of the falx or tentorium.19, 20 According to a report by Towner et al.21 intracranial hemorrhage was caused by vacuum extraction in 1 of 860 neonates, forceps

Conclusion

GSFs are the most common birth-related skull fractures, because the neonatal skull is characterized by considerable elasticity. 3D CT is considerably more accurate than simple skull radiography for detecting GSFs in neonates.

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    • Correlation of Neonatal Birth-Associated Greenstick Skull Fractures with Perinatal Factors and Long-Term Outcome: Children with a Greater Number of Greenstick Skull Fractures Showed Poor Results in Terms of Long-Term Neurodevelopment

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      In birth injury, linear or depressed skull fracture has been reported to occur in 0.1%–0.01% of all births.10,11 Cho et al.9 reported, however, that most of the skull fractures in neonates are GSFs, and the incidence increased 10-fold or greater based on the 3DCT findings confirmed in the surgical view. In the present study, among the 295 neonates with GSF, a linear or depressed skull fracture occurred in 24, showing a greater than 12-fold GSF incidence.

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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