Teevan’s experiments also proved that a fracture of the internal table alone could be produced mechanically, this being in obedience to the law that ‘when a pressure is applied to a body the fracture commences on the line of extension, not that of compression’.
Fractures of the internal table are undoubtedly more common in those situations where diploic tissue is prevalent, e.g. in the frontal, parietal, and upper occipital regions. In the squamo-temporal and cerebellar regions fractures of the internal table are almost unknown.
Teevan also stated that ‘but little force is required to produce such a fracture, and that they are produced usually by some small body, such as a stone’.
=Fractures involving the whole thickness of the skull.= Fractures which involve the whole thickness of the skull may be:--
When depressed, the fragments of bone may be either loose or interlocked, forming in the latter case the so-called pond and gutter fractures.
(_d_) Fissured, stellate, comminuted, punctured, &c.
=Symptoms associated with fracture of the vault.= A diagnosis of fracture of the vault is made:--
On the evidence obtained by local examination.
On the evidence supplied by symptoms dependent on injury to the intracranial contents.
The various intracranial lesions are discussed elsewhere (see Chapters III and IV).
=Evidence supplied by local examination.= A compound fracture will be most readily determined by digital examination, previous to which the scalp-wound must be carefully cleansed. Digital examination is greatly preferable to investigation with the aid of the probe. In any case care must be taken to avoid mistaking one of the sutures of the skull for a fissured fracture.
In simple fractures the diagnosis is frequently obscured by an extensive subaponeurotic or subpericranial hæmatoma. Irregularities of surface are more or less diagnostic of a solution in the surface of the bone, and a linear hæmatoma is of corresponding clinical value. In any case, the presence of an extensive hæmatoma must be regarded as of so suggestive a nature that exploration is called for, more especially when prolonged concussion or compression are co-existent. Such treatment is imperative when the hæmatoma--whether diffuse, localized, or linear--pulsates, such a condition implying a breach in the surface of both bone and dura with communication between the extra-cranial and some intra-cranial hæmorrhage.