It is one of the oldest known neurosurgical procedures, dating from the year 3000 B. C., when the Paracas Indians in Peru performed procedures to correct large cranial defects.
Archeologic findings proved that the use of inorganic materials for cranioplasty had begun before the organic materials 1).
Across the centuries, many materials have been used for covering bony defects, including coconut shells, bones from both human and non-human donors, metals including gold, silver, tantalum, and titanium and more recently, biosynthetic materials such as resins and ceramics.
Cranioplasties are performed to protect the brain and correct cosmetic defects, but there is growing evidence that this procedure may result in neurological improvement.
The aim of cranioplasty is not only a cosmetic issue; also, the repair of cranial defects gives relief to psychological drawbacks and increases the social performances.
Cranioplasty is performed mostly after traumatic injuries.
The aim is not only a cosmetic issue; also, the repair of cranial defects gives relief to psychological drawbacks and increases the social performances.
The incidence of epilepsy is shown to be decreased after cranioplasty.
The presence of hydrocephalus, infection, and brain swelling. In children below 4 years old, if there is an intact dura mater, cranium can achieve self closure.
The pediatric patient for this procedure is distinct from the adult one because of the growing skulls and thinner bones of the calvarium. A paucity of data on the outcomes of this procedure in the pediatric population has been identified repeatedly.
Wagas et al conducted a retrospective cohort study to investigate the outcomes in a pediatric population that underwent cranioplasty after craniectomy at a institute in a developing-world country. The cohort showed no association of complication rate or cosmetic outcomes with the timing of cranioplasty, area of skull defect, type of implant used, or method of storage 3).
Considering the significant clinical and economic impact of the procedure, the search for materials and strategies to provide more comfortable and reliable surgical procedures is one of the most important challenges.
A literature review emphasizes the benefits and weaknesses of each considered material commonly used for cranioplasty, especially in terms of infectious complications, fractures, and morphological outcomes.As regards the latter, this appears to be very similar among the different materials when custom three-dimensional modeling is used for implant development, suggesting that this criterion is strongly influenced by implant design. However, the overall infection rate can vary from 0% to 30%, apparently dependent on the type of material used, likely in virtue of the wide variation in their chemico-physical composition. Among the different materials used for cranioplasty implants, synthetics such as polyetheretherketone, polymethylmethacrylate, and titanium show a higher primary tear resistance, whereas hydroxyapatite and autologous bone display good biomimetic properties, although the latter has been ascribed a variable reabsorption rate of between 3% and 50%. In short, all cranioplasty procedures and materials have their advantages and disadvantages, and none of the currently available materials meet the criteria required for an ideal implant. Hence, the choice of cranioplasty materials is still essentially reliant on the surgeon's preference 4).
In 19th century, the use of bone from different donor sites, such as ribs or tibia, gained wide population.
Many different types of materials were used throughout the history of cranioplasty. With the evolving biomedical technology, new materials are available to be used by the surgeons. Although many different materials and techniques had been described, there is still no consensus about the best material, and ongoing researches on both biologic and nonbiologic substitutions continue aiming to develop the ideal reconstruction materials.
Cranioplasty can be performed either with gold-standard, autologous bone flaps and osteotomies or alloplastic materials in skeletally mature patients. Recently, custom computer-generated implants (CCGIs) have gained popularity with surgeons because of potential advantages, which include preoperatively planned contour, obviated donor-site morbidity, and operative time savings. A remaining concern is the cost of CCGI production.
Several materials are available. Each has its advantages and disadvantages. Search is on for an ideal material.
Acrylic bone cement
An experimental model was developed in an indoor gun range. CAD cranioplasties with a material thickness of 2-6 mm, made of titanium or PEEK-OPTIMA(®) were fixed in a watermelon and shot at with a .222 Remington rifle at a distance of 30 m distance, a .30-06 Springfield rifle at a distance of 30 m, a Luger 9 mm pistol at a distance of 8 m, or a .375 Magnum revolver at a distance of 8 m. The CAD cranioplasties were subsequently inspected for ballistic effects by a neurosurgeon.
Titanium CAD cranioplasty implants resisted shots from the 9 mm Luger pistol and were penetrated by both the .222 Remington and the .30-06 Springfield rifle. Shooting with the .357 Magnum revolver resulted in the titanium implant bursting. PEEK-OPTIMA(®) implants did not resist bullets shot from any weapon. The implants burst on shooting with the 9 mm Luger pistol, the .222 Remington, the .30-06 Springfield rifle, and the .357 Magnum revolver.
Titanium CAD cranioplasty implants may offer protection from ballistic injuries caused by small caliber weapons fired at short distances. This could provide a life-saving advantage in civilian as well as military combat situations 5).
Methylmethacrylate and porous polyethylene (PP) were resistant to fracture and disruption. MMA provided the greatest neuroprotection, followed by PP. Autologous bone provided the least protection with cranioplasty disruption and severe brain injury occurring in every patient. Brain injury patterns correlated with the degree of cranioplasty disruption regardless of the cranioplasty material. Regardless of the energy of impact, lack of dislodgement generally resulted in no obvious brain injury 6)
A PubMed, Google Scholar, and MEDLINE search adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines included studies reporting patients who underwent DC and subsequent cranioplasty in whom cerebral hemodynamics were measured before and after cranioplasty.
The search yielded 21 articles with a total of 205 patients (range 3-76 years) who underwent DC and subsequent cranioplasty. Two studies enrolled 29 control subjects for a total of 234 subjects. Studies used different imaging modalities, including CT perfusion (n = 10), Xenon-CT (n = 3), single-photon emission CT (n = 2), transcranial Doppler (n = 6), MR perfusion (n = 1), and positron emission tomography (n = 2). Precranioplasty CBF evaluation ranged from 2 days to 6 months; postcranioplasty CBF evaluation ranged from 7 days to 6 months. All studies demonstrated an increase in CBF ipsilateral to the side of the cranioplasty. Nine of 21 studies also reported an increase in CBF on the contralateral side. Neurological function improved in an overwhelming majority of patients after cranioplasty.
This systematic review suggests that cranioplasty improves CBF following DC with a concurrent improvement in neurological function. The causative impact of CBF on neurological function, however, requires further study 7).
Paredes et al., prospectively studied cranioplasties performed at a hospital over a 5-year period. The National Institute of Health Stroke Scale and Barthel index were recorded prior to and within 72 h after the cranioplasty. A perfusion computed tomography (PCT) and transcranial Doppler sonography (TCDS) were performed prior to and 72 h after the surgery. For the PCT, regions irrigated by the anterior cerebral artery, the middle cerebral artery (MCA), the posterior cerebral artery, and the basal ganglia were selected, as well as the mean values for the hemisphere. The sonography was performed in the sitting and the supine position for the MCA and internal carotid. The velocities, pulsatility index, resistance index, and Lindegaard ratio (LR) were obtained, as well as a variation value for the LR (ΔLR = LR sitting - LR supine). Fifty-four patients were included in the study. Of these, 23 (42.6%) patients presented with objective improvement. The mean cerebral blood flow of the defective side (m-CBF-d) increased from 101.86 to 117.17 mL/100 g/min (p = 0.064), and the m-CBF of the healthy side (m-CBF-h) increased from 128.14 to 145.73 mL/100 g/min (p = 0.028). With regard to the TCDS, the ΔLR was greater on the defective side prior the surgery in those patients who showed improvement (1.295 vs. -0.714; p = 0.002). Cranioplasty resulted in clinical improvement in 40% of the patients, with an increase in the post-surgical CBF. The larger variations in the LR when the patient is moved from the sitting to the supine position might predict the clinical improvement 8).
Wachter et al., performed a retrospective chart analysis of patients that underwent DC and subsequent bone flap reimplantation between 2001 and 2011 at the Department of Neurosurgery, Georg-August-University Göttingen, Göttingen, Germany.
They registered demographic data, initial clinical diagnosis and surgery-associated complications.
They identified 136 patients that underwent DC and subsequent reimplantation. Forty-one patients (30.1%) had early or late surgery-associated complications after bone flap reimplantation. Most often, bone flap resorption and postoperative wound infections were the underlying causes (73%, n=30/41). Multivariate analysis identified age (p=0.045; OR=16.30), GOS prior to cranioplasty (p=0.03; OR=2.38) and nicotine abuse as a prognostic factor for surgery-associated complications (p=0.043; OR=4.02). Furthermore, patients with early cranioplasty had a better functional outcome than patients with late cranioplasty (p<0.05).
Almost one-third of the patients that are operated on for bone flap reimplantation after DC suffer from surgery-associated complications. Most often, wound healing disorders as well as bone flap resorption lead to a second or even third operation with the need for artificial bone implantation. These results might raise the question, if subsequent operations can be avoided, if an artificial bone is initially chosen for cranioplasty 9).