Cranioplasty is a

surgical operation Surgery is a medical specialty that uses manual and instrumental techniques to diagnose or treat pathological conditions (e.g., trauma, disease, injury, malignancy), to alter bodily functions (e.g., malabsorption created by bariatric surgery ...

on the repairing of

cranial Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Thi ...

defects caused by previous

injuries Injury is physiological damage to the living tissue of any organism, whether in humans, in other animals, or in plants. Injuries can be caused in many ways, including mechanically with penetration by sharp objects such as teeth or with b ...

or operations, such as

decompressive craniectomy Decompressive craniectomy ('' crani-'' + '' -ectomy'') is a neurosurgical procedure in which part of the skull is removed to allow a swelling or herniating brain room to expand without being squeezed. It is performed on victims of traumatic br ...

. It is performed by filling the defective area with a range of materials, usually a bone piece from the patient or a synthetic material. Cranioplasty is carried out by incision and reflection of the

scalp The scalp is the area of the head where head hair grows. It is made up of skin, layers of connective and fibrous tissues, and the membrane of the skull. Anatomically, the scalp is part of the epicranium, a collection of structures covering th ...

after applying anaesthetics and antibiotics to the patient. The

temporalis muscle In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic a ...

is reflected, and all surrounding

soft tissue Soft tissue connective tissue, connects and surrounds or supports internal organs and bones, and includes muscle, tendons, ligaments, Adipose tissue, fat, fibrous tissue, Lymphatic vessel, lymph and blood vessels, fasciae, and synovial membranes.� ...

s are removed, thus completely exposing the cranial defect. The cranioplasty flap is placed and secured on the cranial defect. The wound is then sealed. Cranioplasty was closely related to

trephination Trepanning, also known as trepanation, trephination, trephining or making a burr hole (the verb ''trepan'' derives from Old French from -4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, t ...

, and the earliest operation is dated to 3000 BC. Currently, the procedure is performed for both cosmetic and functional purposes. Cranioplasty can restore the normal shape of the

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

and prevent other complications caused by a sunken scalp, such as the "syndrome of the trephined". Cranioplasty is a risky operation, with potential risks such as

bacterial infection Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and many are beneficial but others can cause infectious diseases. The number of t ...

and bone flap resorption.

Etymology

The word ''cranioplasty'' can be broken down into two parts: cranio- and -plasty. Cranio- originates from the Ancient

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word κρανίον, meaning "

cranium The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

", while -plasty comes from the Ancient

word πλαστός, meaning "moulded" or "fashioned".

Medical uses

The operation has its cosmetic value as the normal shape of the cranium of patients is restored instead of the presence of a sunken skin flap, which may affect the confidence of patients. It also has its therapeutic value as the operation provides structure to the skull and protection to the brain from physical damage. The surgery restores regular cerebrospinal fluid (CSF) and

cerebral Cerebral may refer to: * Of or relating to the brain * Cerebrum, the largest and uppermost part of the brain * Cerebral cortex, the outer layer of the cerebrum * Retroflex consonant, also referred to as a cerebral consonant, a type of consonant so ...

blood flow dynamics, along with normal

intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adu ...

. Cranioplasty may improve

neurological Neurology (from , "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous system, which comprises the brain, the s ...

function in some individuals. Furthermore, it can reduce the occurrence of

headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...

s caused by injury or previous surgery. The optimal timing of cranioplasty is controversial. Some experts put the time between a

craniectomy Decompressive craniectomy ('' crani-'' + '' -ectomy'') is a neurosurgical procedure in which part of the skull is removed to allow a swelling or herniating brain room to expand without being squeezed. It is performed on victims of traumatic b ...

and a cranioplasty at usually between 6 months and a year, while others say that the two operations should be more than a year apart. The timing of cranioplasty is affected by multiple factors. Sufficient time is required for the recovery of the incision from the previous operation, as well as to clear any infections (both systemic and cranial). Some findings showed that a greater infection rate is associated with early cranioplasty due to interruption of wound healing, as well as an increased incidence of

hydrocephalus Hydrocephalus is a condition in which cerebrospinal fluid (CSF) builds up within the brain, which can cause pressure to increase in the skull. Symptoms may vary according to age. Headaches and double vision are common. Elderly adults with n ...

. Contrarily, there is evidence of early cranioplasty limiting complications caused by "syndrome of the trephined", including changes in

cerebral blood flow Cerebral circulation is the movement of blood through a network of cerebral arteries and veins supplying the brain. The rate of cerebral blood flow in an adult human is typically 750 milliliters per minute, or about 15% of cardiac output. ...

and abnormal

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

hydrodynamics. Other researchers have reported no significant difference in infection rate with different operational timings.

Contraindication In medicine, a contraindication is a condition (a situation or factor) that serves as a reason not to take a certain medical treatment due to the harm that it would cause the patient. Contraindication is the opposite of indication, which is a rea ...

s for cranioplasty include the presence of

brain swelling Cerebral edema is excess accumulation of fluid (edema) in the intracellular or extracellular spaces of the brain. This typically causes impaired nerve function, increased pressure within the skull, and can eventually lead to direct compressi ...

, and

. Cranioplasty is withheld until all contraindications are cleared.

Procedure

Before the operation,

CT scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

s and

MRIs Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and rad ...

are taken to study the cranial defect. The patient is given antibiotics to prevent bacterial infection. The patient is situated on a foam donut or a horseshoe head holder for the operation. The patient is then anaesthetised and an incision is made following the incision of the previous operation. The

and the

is reflected to completely reveal the cranial defect. Significant blood loss is observed as new

blood vessel Blood vessels are the tubular structures of a circulatory system that transport blood throughout many Animal, animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the Tissue (biology), tissues of a Body (bi ...

s formed in scar tissues are damaged by incision. Any

s at the edge of the defect are removed and the defect is cleaned. The cranioplasty material is placed on the defect and is fixed to the surrounding

with standard titanium plate and screws. CSF may be drained from the brain to reduce

hernia A hernia (: hernias or herniae, from Latin, meaning 'rupture') is the abnormal exit of tissue or an organ (anatomy), organ, such as the bowel, through the wall of the cavity in which it normally resides. The term is also used for the normal Devel ...

tion. Small holes may be drilled on the bone graft or the prosthesis to prevent the accumulation of fluid under the repaired defect.

Soft tissue Soft tissue connective tissue, connects and surrounds or supports internal organs and bones, and includes muscle, tendons, ligaments, Adipose tissue, fat, fibrous tissue, Lymphatic vessel, lymph and blood vessels, fasciae, and synovial membranes.� ...

temporalis In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic ...

, and the scalp are then fixed back in place. Subgaleal drain and dressing are applied to control facial swelling. After the operation, a

is taken and patients may stay in intensive care for at least a night for better neurological status observation, or be placed in a regular care unit. The subgaleal drain and dressing are removed before the patient is dispatched.

Children

Special considerations to children undergoing cranioplasty are made to accommodate for their growing

. Certain materials are more favoured when compared to adult cranioplasty. Autologous bone grafts are the most preferred materials for

paediatric Pediatrics (American English) also spelled paediatrics (British English), is the branch of medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Prev ...

cranioplasty, as they are accepted by the host and the bone flap can be integrated into the body of the host. However, autologous bone pieces may be unavailable or unsuitable in certain occasions. The body size of children may be not enough to have bone flaps to be stored in their subcutaneous spaces, while

cryopreservation Cryopreservation or cryoconservation is a process where biological material - cells, tissues, or organs - are frozen to preserve the material for an extended period of time. At low temperatures (typically or using liquid nitrogen) any cell ...

facilities for bone grafts are not widely available. The use of

autograft Autotransplantation is the transplantation of organs, tissues, or even particular proteins from one part of the body to another in the same person ('' auto-'' meaning "self" in Greek). The autologous tissue (also called autogenous, autogen ...

is also associated with a high rate of

bone resorption Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood. The osteoclasts are multi-nuclea ...

. Synthetic materials are used for paediatric cranioplasty when the use of

autografts Autotransplantation is the transplantation of organs, tissues, or even particular proteins from one part of the body to another in the same person ('' auto-'' meaning "self" in Greek). The autologous tissue (also called autogenous, autogenei ...

is not available or not recommended.

Hydroxyapatite Hydroxyapatite (International Mineralogical Association, IMA name: hydroxylapatite) (Hap, HAp, or HA) is a naturally occurring mineral form of calcium apatite with the Chemical formula, formula , often written to denote that the Crystal struc ...

is another option for children cranioplasty as it allows the expansion of cranium for children and its ability to be moulded smoothly. It is less commonly used than autografts due to its brittle nature, high infection rate, and poor ability to integrate with the human

. Bilateral cranioplasties are more prone to complications compared to unilateral cranioplasties in children. This may be explained by its larger scalp wound area, a higher volume of blood loss, and the higher complexity and duration of the operation.

Risks

Cranioplasty's complication risk ranges from 15% to 41%. The cause for such a high risk compared to that borne by other

neurosurgical Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty that focuses on the surgical treatment or rehabilitation of disorders which affect any portion of the nervous system including the brain, s ...

operations is unclear. Male patients and older patients are groups with higher rates of complication. Complications occurring after cranioplasty include

, bone flap resorption,

wound dehiscence Wound dehiscence is a surgical complication in which a wound ruptures along a surgical incision. Risk factors include age, collagen disorder such as Ehlers–Danlos syndrome, diabetes, obesity, poor knotting or grabbing of stitches, and traum ...

hematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is ...

seizures A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...

, hygroma, and cerebrospinal fluid (CSF) leakage. The risk of bacterial infections in performing cranioplasty ranges from 5 to 12.8%. Multiple factors are affecting the risk of infection, one being the materials used for the operation. Using

titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

, whether being custom-made or using a

mesh Medical Subject Headings (MeSH) is a comprehensive controlled vocabulary for the purpose of indexing journal articles and books in the life sciences. It serves as a thesaurus of index terms that facilitates searching. Created and updated by th ...

, is associated with a lower infection rate; on the other hand, materials such as

methyl methacrylate Methyl methacrylate (MMA) is an organic compound with the formula . This colorless liquid, the methyl ester of methacrylic acid (MAA), is a monomer produced on a large scale for the production of poly(methyl methacrylate) (PMMA). History MMA ...

and autologous bone is associated with a higher infection rate. Another risk factor for bacterial infection is the location of the operation. Bifrontal cranioplasties are associated with significantly higher infection rates and higher rates for reoperation. Other risk factors for infection include previous infections, contact between

sinuses Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoi ...

and operation site, devascularized scalp (loss of blood supply in the scalp), previous operations, and type of injury.

Bone resorption Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood. The osteoclasts are multi-nuclea ...

is another complication of cranioplasty with a complication rate of 0.7-17.4%. Bone resorption occurs when the autologous graft does not have blood supply due to devitalisation, or when scar tissues or

s remain on the edge of the cranial defect during cranioplasty.

Paediatric Pediatrics (American English) also spelled paediatrics (British English), is the branch of medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Prev ...

patients have a higher risk of resorption, with a resorption rate up to 50%.

is more likely to occur in this group of patients when their cranioplasty is carried out over 6 weeks after their previous operation. Fragmented bone flaps, as well as large bone flaps (>70 cm²), are associated with a higher resorption rate.

History

Ancient history

Trepanated skull of a woman-P4140363-black

The earliest cranioplasty operation is dated to 3000 BC in the Pre-Columbian Peruvian civilisation, where precious metals, gourds, and shells were found next to trepanned skulls in graveyards, suggesting that cranioplasty had been performed. In the Paracas region of present-day

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

, a skull from 2000 BC with a thin plate of gold covering a cranial defect was found. Moreover, defective skulls were found covered with coconut shells or

palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae ** List of Arecaceae genera **Palm oil * Several other plants known as "palm" Palm or Palms may also refer to: Music ...

leaves in ancient tribes of the Polynesian Islands. Sanan and Haines stated that the materials being used for cranioplasty were associated with the status of the patient.

Modern history

Research on cranioplasty was not emphasised among early surgical authors in ancient

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

, and

Rome Rome (Italian language, Italian and , ) is the capital city and most populated (municipality) of Italy. It is also the administrative centre of the Lazio Regions of Italy, region and of the Metropolitan City of Rome. A special named with 2, ...

, although there were research and practice on

in ancient

and

. More emphasis was placed on developing skills in applying dressing on an open wound. The earliest modern description of cranioplasty was written by surgeon Ibrahim bin Abdullah of the

Ottoman Empire The Ottoman Empire (), also called the Turkish Empire, was an empire, imperial realm that controlled much of Southeast Europe, West Asia, and North Africa from the 14th to early 20th centuries; it also controlled parts of southeastern Centr ...

, in his surgical book '' Alâim-i Cerrâhîn'' in 1505. The book mentioned the use of

xenografts Xenotransplantation (''xenos-'' from the Greek meaning "foreign" or strange), or heterologous transplant, is the transplantation of living cells, tissues or organs from one species to another.Kangal dogs or goats as materials for cranioplasty. Such materials were used due to the accessibility of these animals near battlefields, where the procedure is likely to be performed. The first true description of cranioplasty in Europe was made by Fallopius in the 16th century, stating that the fractured

should be removed and be reinserted with a gold plate if the dura was damaged. This was questioned by other practitioners at his time, concerning that surgeons may keep the gold instead of using it for surgery. The first cranioplasty was reported by the Dutch surgeon Job Janszoon van Meekeren. The report described the use of a segment of a

canine Canine may refer to: Zoology and anatomy * Animals of the family Canidae, more specifically the subfamily Caninae, which includes dogs, wolves, foxes, jackals and coyotes ** ''Canis'', a genus that includes dogs, wolves, coyotes, and jackals ** Do ...

as a material for cranioplasty on a

nobleman Nobility is a social class found in many societies that have an aristocracy. It is normally appointed by and ranked immediately below royalty. Nobility has often been an estate of the realm with many exclusive functions and characteristics. T ...

Moscow Moscow is the Capital city, capital and List of cities and towns in Russia by population, largest city of Russia, standing on the Moskva (river), Moskva River in Central Russia. It has a population estimated at over 13 million residents with ...

. The operation was successful, but its use of canine bone was not accepted by the church and the man was forced to leave Russia. Since the first operation, bones from more animal species were used as xenografts for cranioplasty. These include

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the gray wolf. Also called the domestic dog, it was selectively bred from a population of wolves during the Late Pleistocene by hunter-gatherers. ...

ape Apes (collectively Hominoidea ) are a superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans are found global ...

geese A goose (: geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera '' Anser'' (grey geese and white geese) and ''Branta'' (black geese). Some members of the Tadorninae subfamily (e.g., Egyp ...

rabbit Rabbits are small mammals in the family Leporidae (which also includes the hares), which is in the order Lagomorpha (which also includes pikas). They are familiar throughout the world as a small herbivore, a prey animal, a domesticated ...

s, calves,

eagle Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family of the Accipitridae. Eagles belong to several groups of Genus, genera, some of which are closely related. True eagles comprise the genus ''Aquila ( ...

s, oxen, and buffalos. In 1917, William Wayne Babcock reported the use of "soup bone", a piece of cooked and

perforated A perforation is a small hole in a thin material or web. There is usually more than one perforation in an organized fashion, where all of the holes collectively are called a ''perforation''. The process of creating perforations is called perfor ...

animal bone as a xenograft.

Development of modern materials

The prevalence of

head injuries A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

increased in the 20th century with the advancement of armaments, particularly the use of

hand grenades A grenade is a small explosive weapon typically thrown by hand (also called hand grenade), but can also refer to a shell (explosive projectile) shot from the muzzle of a rifle (as a rifle grenade) or a grenade launcher. A modern hand grenade g ...

trench warfare Trench warfare is a type of land warfare using occupied lines largely comprising Trench#Military engineering, military trenches, in which combatants are well-protected from the enemy's small arms fire and are substantially sheltered from a ...

during

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

. Along with a decreased mortality from suffering such injuries due to the development of cell debris removal, wound closing, and the use of

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

s, cranioplasty techniques were therefore improved.

Autografts Autotransplantation is the transplantation of organs, tissues, or even particular proteins from one part of the body to another in the same person ('' auto-'' meaning "self" in Greek). The autologous tissue (also called autogenous, autogenei ...

allografts Allotransplant (''allo-'' meaning "other" in Greek) is the transplantation of cells, tissues, or organs to a recipient from a genetically non-identical donor of the same species. The transplant is called an allograft, allogeneic transplant, ...

and synthetic materials are the main types of materials used for cranioplasty.

Autografts, or autologous grafts, are body tissues taken from the patient. The first successful cranioplasty using an autograft was recorded in 1821, with the bone piece being reinserted into the cranium. The operation achieved partial healing. Subsequently, more studies and operations were carried out with autografts. A successful case of reimplantation of cranial bone was reported by Sir William Macewen in 1885, popularising autografts to be material for cranioplasty. Succeeding operations involved autografts taken from different parts of the patient's body, such as the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

(leg bone),

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

(shoulder blade), ilium (hip bone),

sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...

(chest bone), along with fat tissues and

fascia A fascia (; : fasciae or fascias; adjective fascial; ) is a generic term for macroscopic membranous bodily structures. Fasciae are classified as superficial, visceral or deep, and further designated according to their anatomical location. ...

. Allografts are tissues from another individual of the same species. The first use of allografts was reported in 1915 with

cadaver A cadaver, often known as a corpse, is a Death, dead human body. Cadavers are used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue (biology), tissue to ...

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

by Morestin. Subsequently, another 32 cases of cranioplasties performed with cadaver cartilage were reported by Gosset in 1916. The use of

was favoured during

due to its

malleability Ductility refers to the ability of a material to sustain significant plastic Deformation (engineering), deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic def ...

and resistance to infection. Its use declined because of its lack of significant

calcification Calcification is the accumulation of calcium salts in a body tissue. It normally occurs in the formation of bone, but calcium can be deposited abnormally in soft tissue,Miller, J. D. Cardiovascular calcification: Orbicular origins. ''Nature M ...

and strength.

Cadaver A cadaver, often known as a corpse, is a Death, dead human body. Cadavers are used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue (biology), tissue to ...

was another type of allograft reported to be used as a cranioplasty material multiple times by Sicard and Dambrin from 1917 to 1919. The material was not favoured due to the high infection rate with its use. In the 1980s, the use of cadaver allograft disc for filling in small holes received a satisfactory result, and there was a resurgence of the use of

bone. However, cadaver bones and allografts, in general, are not the preferred materials in modern operations. The use of methyl methacrylate (PMMA) for cranioplasty has been developed since

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, when there was a high demand for it to treat combat injuries, and used extensively since 1954. PMMA becomes malleable when an

exothermic reaction In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change Δ''H''⚬ is negative." Exothermic reactions usually release heat. The term is often confused with exergonic reaction, which IUPAC define ...

occurs between its powder form and

benzoyl peroxide Benzoyl peroxide is a chemical compound (specifically, an organic peroxide) with structural formula , often abbreviated as (BzO)2. In terms of its structure, the molecule can be described as two benzoyl (, Bz) groups connected by a peroxide ...

, allowing it to be moulded to the cranial defect. Advantages of using it are its malleability, low cost, high strength and high durability. Disadvantages include its vulnerability to

infection An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

, as

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

may adhere to its

fibrous Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often inco ...

layer, as well as its brittle nature and absence of growth potential. Other common synthetic materials for cranioplasty include

and

hydroxyapatite Hydroxyapatite (International Mineralogical Association, IMA name: hydroxylapatite) (Hap, HAp, or HA) is a naturally occurring mineral form of calcium apatite with the Chemical formula, formula , often written to denote that the Crystal struc ...

. Titanium was first used for cranioplasty in 1965. It can be used as a plate or a mesh and be 3D printed as a porous form. Titanium is non-

ferromagnetic Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagne ...

and non-

corrosive Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

, making the host free from inflammatory reactions. It is also robust, thus preventing patients from trauma. The use of titanium is associated with a lower infection rate. Disadvantages of using titanium include its high cost, poor malleability, and disruption to

images. Hydroxyapatite is a compound of

calcium phosphate The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white ...

being arranged in a

hexagon In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A regular hexagon is de ...

al structure. It bonds well chemically with bones and inflicts little inflammatory reaction by the host, and has good osteointegration. It can be expanded and is used in

cranioplasty. It can be moulded smoothly and has appealing cosmetic results. However, the material is brittle and has low

tensile strength Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or F_\text in notation) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate ...

, and so is only suitable to be used for small cranial defects. Its use is also associated with a high infection rate. Hydroxyapatite is often used with a titanium mesh to prevent fractures and for better osteointegration.

References

{{Central nervous system tests and procedures Neurosurgical procedures Body modification Oral and maxillofacial surgery