I. What problems can occur with cranial defects.
1) aggravate brain injury: the skull defect area causes the patient’s head to be deformed, collapsing when upright, expanding when lying down, concave in the daytime and convex at night, due to the lack of skull protection, the external atmospheric pressure directly compresses the brain tissue through the defect area, and the repeated back and forth movement causes progressive damage to the local brain tissue of the defect. The damage mainly includes mechanical, cerebrospinal fluid dynamics and cerebral hemodynamics. Under normal circumstances, the subarachnoid space exists between the skull and the brain surface, and the cerebrospinal fluid flows with the rhythmic pulsation of brain tissue. When the skull is defective, the scalp lacks the support of the skull and collapses directly onto the brain surface, and the subarachnoid space in the defect area disappears, affecting the cerebrospinal fluid reflux, which is a factor causing chronic hydrocephalus and aggravating hydrocephalus. It also seriously affects the reflux of the superficial veins on the surface of the brain, making the blood flow to the brain tissue impaired. In addition, the reciprocal movement of the brain tissue in the area, the mechanical friction between the brain tissue and the edge of the defective skull, over time, leads to local brain atrophy and aggravation of the brain scar. The cumulative effect of the above three aspects of damage eventually results in new symptoms of neurological dysfunction, or aggravation of the original symptoms, seizures, hydrocephalus, etc.
2) Affecting the rehabilitation of brain function: Patients are afraid of the pulsation, expansion and collapse of the defect area, afraid of sunlight, vibration and even noisy sound, and often have poor self-control, poor concentration or memory loss, or depression, fatigue, reticence and low self-esteem, dizziness, headache, local tenderness, irritability and restlessness, which are called cranial defect syndrome. It leads to the decrease of quality of life and affects the rehabilitation effect.
3) Obstruction of aesthetics and safety: cranial defects are an obstacle to aesthetics, especially those located in the frontal area; after large cranial defects, the chance of brain tissue damage caused by accidental injury is greatly increased.
Second, which patients should undergo cranial repair.
1) Those with skull defect diameter over 3 cm should undergo skull repair regardless of whether they have symptoms or not.
2) If the diameter of cranial defect is less than 3 cm, the following conditions should be repaired.
(1) The presence of cranial defect syndrome.
②The defective area is aesthetically displeasing.
③Serious mental burden affects work and life.
Timing of cranial repair surgery.
Repair as soon as possible after the original craniotomy incision heals and the increase in intracranial pressure is relieved.
Cranial repair surgery.
Cranial repair generally uses the original surgical incision, places the cranial repair material between the scalp and the dura mater (or the membrane scar formed outside the brain tissue) that protects the brain tissue, firmly fixes the repair material with the surrounding normal skull by inlaying or covering, and finally sutures the scalp incision.
V. Materials available for cranial repair.
①Titanium memory alloy is a high-tech material widely used in human repair and fixation, which has the advantages of hardness, good shaping effect, firm fixation and rare rejection reaction with the body, but the price is relatively expensive.
②Silicone cranial bone is prefabricated by the manufacturer according to the shape of most people’s cranium, and it is cut on the corresponding prefabricated material according to the defective parts during surgery, which does not necessarily fully meet the shape of specific patients, but it is inexpensive.
③Artificial bone cement is close to cranial bone in composition, with good histocompatibility and easy shaping, but weak impact resistance.
④ Plexiglass has the advantages of hardness and light weight, but poor shaping, weak impact resistance, and rejection reaction with the body is common.
VI. Digital three-dimensional cranial reconstruction technology.
Digital three-dimensional cranial reconstruction technology is used for cranial repair. The specific process is as follows.
1) Thin-layer CT scan of the patient’s head, followed by three-dimensional reconstruction of the patient’s head using CT workstation.
2) Production of a cranial simulation model using numerical control technology.
3) calculation and fabrication of a three-dimensional restoration of the defective area using numerical control technology with reference to the healthy part and simulation technology.
4) in vitro verification of the restoration with the cranial simulation model.
5) Surgical placement of the restoration.