The ping-pong fracture is a particular type of skull fracture in neonates and infants. In this type of fracture with indentation, which is less frequent, the calvarium is pushed inwardly, and the fracture line is not visualised radiologically. It is a type of fracture characteristic to neonates and young infants, and its occurrence is due to the malleable as well as elastic nature of the bones at this age. It is akin to “greenstick” fractures in the diaphysis of the long bones in children.
Neurological symptoms are usually absent under a conclusive clinical examination, showing deformations of the skull evident on palpation. Diagnostic imaging investigations are the plain cranial radiography and, as choice investigation, the native cerebral CT scan with bone window and 3D reconstruction. Although cases of spontaneous recovery are described, too (almost exclusively in certain cases with obstetric aetiology), the therapeutic solutions addressed to these particular types of skull fractures are either surgical or non-surgical, instrumental alternatives such as application of pumps, which create negative pressure at the level of invaginations. The pumps are like those used as breast milk extractors or vacuum extractors for obstetrical use.
For the entire population, the birth of a child is, we believe, one of the most important and joyful life events. Parents and family, not to endanger its existence, protect the new-born and, later on, the child during its growth, knowing the fragility of the age of the child at this stage. Therefore, traumatic events, especially in the immediate post-natal and infant stages are a rare pathological entity incidence. An even greater rarity is the head trauma, since the cephalic extremity is unanimously regarded as the most important and consequently the most protected part of the body.
As this period of life is special, so traumatic injuries are a particular feature that is not found in other ages. Within the cranial-cerebral trauma pathology seen in paediatric age population, a particular type of traumatic fracture is the “ping-pong” skull fracture. This particular type of skull fracture is met in neonates and infants. This less common pathological entity may be classified as a depressed fracture, with the particularity of a smooth inward indentation of the calvarium while imaging methods do not evidence a distinct fracture line.
The occurrence of this type of fracture is due to the malleable and elastic nature of the bones at this age. The “ping-pong” fracture may be considered a correspondent to “greenstick” fractures in the diaphysis of the long bones in children. The name given to this type of fracture comes from the aspect of the skull that is similar to a ping-pong ball that has been indented inwards after being pressed in with a finger.
Material and method
The main types of fractures at 0-1 years of age are the linear ones (Fig. 1) and the diastatic ones (Fig. 2), noting that, at this age, the calvarium structure allows great elasticity therefore skull fractures are extremely rare. The linear skull fracture has no medical or surgical treatment. The diastatic fracture needs to be tracked in time (clinically and using CT imaging) because it may lead to a progressive skull
fracture, that is specific to this age group.Between January 1st, 1999 and December 31st, 2014 (16 years) at the department of paediatric neurosurgery from “Bagdasar-Arseni” Emergency Hospital and since January 2013 at Sanador Hospital in Bucharest, 111 cases of traumatic brain injury in children under 1 year were presented and hospitalized. Of these, 7 cases (6.3%) met the characteristics of a “ping-pong” fracture.
Aetiology of the lesions was of obstetrical nature (in 5 cases), only two such injuries being secondary to minor traumas that occurred postnatally.
In terms of clinical presentation, in all cases, on palpation of the baby’s skull, an inward bump of the calvarium was noted. In most cases, this type of fracture is not accompanied by objective neurologica! symptoms. Of the analysed cases, in only one, a marked and prolonged psychomotor agitation of the child has been noted which set in post traumatically.
From the point of view of therapeutic solutions adopted in all cases analysed, surgery was required for the correction of the deflection of the calvarium.
All cases were discharged without objective neurological deficits, with favourable subsequent development, devoid of neurological sequelae.
Fig. 1 – Right temporal linear fracture in a three-month infant
Fig. 2 – Right frontal-parietal diastatic fracture in an eleven-month infant
Anatomically, in this type of fracture, both the periosteum and dura mater are intact. 
The minimal lesion aspect of the structures in the immediate vicinity of the surface of the bone (periosteum, dura mater, etc.) determines that this type of fracture be treated similarly to the “greenstick” fractures that occur, at the same age category, in the diaphysis of the long bones. These particular issues of the fracture are mainly due to the malleable nature of the bone in this early period of life and to the nature of the periosteum that has an osteogenic role and a protective one, too, at this stage of development of bone tissue, due to its thickness.
The most important causes that lead to this type of fracture are obstetrical trauma during childbirth and minor head injuries incurred postnatally. The most common cause is the trauma that occurs during the delivery of the newborn, whose skull has a soft consistency, when in contact with the bone topography of increased hardness of mother’s basin. Another cause of trauma may be the delivery using instruments such forceps or vacuum -extractor.  Outside obstetric causes, postnatal traumatic aetiology may also be involved, but very rarely, in “ping-pong” fractures. It is trauma caused by precipitation from a lower height by hitting the skull on a hard object with a small area of contact.
With advancing age, the skull acquires a firmer consistency, which is why this particular fracture entity, the “ping-pong” fracture, has an increasingly low incidence. The consistency of a higher hardness makes the skull bones to become stiffer and less elastic when exposed to mechanical strain, therefore the action of the traumatic agent will lead to the occurrence of fracture lines. 
Radiological investigations conducted in cases of “ping-pong” fracture reveal invagination of the calvarium, with a most often rounded aspect, without being able to highlight individualized indubitable fracture path.
Investigation imaging exams usually include simple skull radiograph type (Fig. 3) and CT scanning with bone window (Fig. 4) and three-dimensional reconstructions of the skull, the latter being the investigation of choice. MRI examination type requires a high consumption of time and resources, due to the need to sedate patients, without bringing additional information.
From the point of view of therapeutic solutions, as with any traumatic injury, both conservative attitudes and surgical therapies may be adopted, each type having its specific risks and indication. 
Fig. 3 – X-ray picture. (Skull X- ray in anteroposterior incidence)
Fig. 4 – Native CT aspect (bone window) – left parietal “ping-pong” skull fracture
There are also described cases of spontaneous recovery of calvarium invagination, with a low incidence. This way of development is almost exclusively found in cases with obstetrical determinism, being extremely rare in cases with other traumatic aetiology occurred postnatally.
The surgical treatment has the disadvantage of the need for general anaesthesia, but it allows a swift, full and effective cure of the lesion. Surgery allows inspection for any damage of dura mater and of the cortical bone to prevent interposition of dura mater among bone fragments (if there is still an unseen discontinuity in the cortical imaging) and thus prevents the development of a progressive fracture.
Surgical treatment consists in practicing a drill hole at a distance from the focus of the invagination and its correction by means of an elevator inserted through the epidural space (Fig. 5)
Fig. 5 – Schematic
Indication for surgical treatment is given mainly by the extension degree of invagination of the calvarium, the number of bones involved (location may involve or cross sutures) and the degree of compression of adjacent brain tissue. Cerebral impairment due to the compression exerted by the deflection of the cranial calotte in the absence of correction, cannot be estimated appropriately in terms of evolutionary potential towards brain injuries with secondary neurologica! deficits or lesion sequelae with epileptogenic character, especially since the neurologic symptoms of accompanying the traumatic bone lesion are virtually non-existent. 
Surgical treatment alternatives are the use of a vacuum extractor or a pump for lactation, which may rectify the deformed calvarium by the negative pressure they induce. 
In terms of prognosis, the majority of cases are without objective neurological symptoms installed secondary to the traumatic episode, thus the risk of subsequent development of neurological sequelae is minor, given the reduced lesion impact on the structures adjacent to the bone.
Finally, we can say that although it is an injury with reduced associated neurological symptoms, indication to adopt a method of restoring the normal appearance of the cranial box and cranial vault in default of a spontaneous correction thereof must be represented not only by considerations relating to cosmetic appearance.
The choice of a solution for interventional treatment should also take into consideration the theoretical possibility of a late onset of neurological sequelae of the type of seizures or the developmental disorders of the affected (compressed) brain tissue, with neurological deficits that may become objective later on.
The cosmetic appearance is also not to be neglected in these cases, given the age of onset of the lesion in children less than 1 year old. On the other hand, there are parents and other family members caring for the patient concerned, who not infrequently is the result of considerable efforts to give birth to a child who must be perfect in all respects.
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 Depressed ping-pong fracture
 Use of the elevator
 Placing the elevator obliquely under the trepanning hole representation of the surgical treatment of the “ping-pong” fracture
 Trepanning hole strictly adjacent to the depressed fracture
 Tip of the elevator under the depressed fracture
 Support element of the elevator in order not to damage the calvarium
 Aspect of undamaged dura mater, arachnoid and encephalon