J Neurosurg 47:790-792,1977
A new method of eranioplasty Technical note
TAKIS J. ASIMACOPOULOS, M.D., NIKOLAS PAPADAKIS, M.D., AND VERNON H. MARK, M.D.
Fifth Harvard Surgical Service (New England Deaconess Hospital), and Department of Neurosurgery, Boston City Hospital, Boston, Massachusetts v' A new method of cranioplasty is described. The skull defect is exposed, and an impression is taken which is used for the construction of a plaster of Paris model of the defect. Methyl methacrylate is molded to the model and thus an accurate reproduction of the skull defect is produced. The technique has the main advantage of good cosmetic appearance and strength. KEY WORDS cranioplasty 9 methyl methacrylate 9
E are presenting a new method of cranioplasty. For impression material we use alginate hydrocolloid, gas sterilized. For the construction of the skull defect model, dental quality plaster of Paris is used, also gas sterilized. The tray for the impression is made of methyl methacrylate and extensively perforated. Dental adhesive is used to increase the anchoring capacity of the tray. The skull plate is constructed from methyl methacrylate.
W
9 ,impression
9 plaster model
Technique The cranial defect is exposed and the pericranium is incised 3 to 4 mm away from the edge of the defect (Fig. 1). The incised pericranium is then removed and the edges of the defect are exposed and cleaned of scar tissue, so that there is a clear demarcation between the dura and the edge of the defect. At this point, an impression tray is made as follows. Methyl methacrylate is mixed to a doughy consistency and fashioned in the shape of the
defect. After it hardens, it is perforated extensively and sprayed with sterile dental adhesive to obtain anchoring capacity. A sterile indelible pencil is then used to mark the edge of the defect. Alginate hydrocolloid is mixed with water to a thick cream, and placed in generous amounts in the tray. The tray is then immediately pressed against the skull defect until it solidifieg (approximately 1 minute). The impression is then removed from the defect. Plaster of Paris is mixed with water and a generous amount of the mixture is used to cover the impression. When the plaster hardens (4 to 5 minutes), it is separated from the impression. The resulting model is compared with the impression and with the skull defect for accuracy and its borders are delineated with a sterile indelible pencil. Methyl methacrylate is mixed to a doughy consistency, placed in the model, and molded into a replica of the missing bone. After the plate hardens (approximately 10 minutes), it
790
J. Neurosurg. / Volume 47 / November, 1977
A new m e t h o d of cranioplasty
FIG. 1. Artist's drawing showing the steps in molding the model of the defect and placing the plate in position.
The method described has several advantages. It provides the surgeon with a system for work outside the operative field. The plaster model is an accurate replica of the skull defect, so the plate will both fit the defect perfectly and have the same contour with the missing bone. This is particularly important when the defect is in a visible area,
such as in the supraorbital and frontal regions. Also, no empty space exists to allow accumulation of fluid inside or outside the plate, with its attendant danger of infection. The uniformity in thickness with the missing bone contributes to the increased strength of the plate, since unequal thickness results in points of decreased strength. There is one further advantage. The heat release and consequent tissue irritation that may result from the direct molding of methyl methacrylate in the skull defect are eliminated. In experiments with dogs, we found that polymerization of methyl methacrylate applied directly to a skull defect raises the temperature of the epidural space from an initial level of 36 ~ to 64 ~ C despite continuous irrigation with cold saline. This rise lasts for approximately 3 minutes. Further experi-
J. Neurosurg. / Volume 47 / November, 1977
791
is removed from the model and fitted into the skull defect. Any minor irregularities may be smoothed with a pneumatic drill. A few perforations are made in the plate and it is wired to the skull in the usual manner. To this date, we have performed 10 cranioplasties with this method, producing good cosmetic results even in cases with very large defects. Discussion
T. J. Asimaeopoulos, N. Papadakis and V. H. Mark mental work by one of us has demonstrated the deleterious effect of heat on cell viability. 1
left ventricular circulatory assist device, in Bell AC, Nerem RM: 1975 Advances in Bioengineering. New York: American Society of Mechanical Engineers, 1976, pp 28-31
Reference
1. Asimacopoulos P J, McGrath J J, Cravalho EG: The thermal sensitivity of the human fibroblast HeLa S-3 as a model for thermal insult to the neointima of a nuclear-fueled, blood-cooled,
Address reprint requests to: Nikolas Papadakis, M.D., Department of Neurosurgery, Boston City Hospital, 818 Harrison Avenue, Boston, Massachusetts 02118.
792
J. Neurosurg. / Volume 47 / November, 1977
A new method of eranioplasty Technical note
TAKIS J. ASIMACOPOULOS, M.D., NIKOLAS PAPADAKIS, M.D., AND VERNON H. MARK, M.D.
Fifth Harvard Surgical Service (New England Deaconess Hospital), and Department of Neurosurgery, Boston City Hospital, Boston, Massachusetts v' A new method of cranioplasty is described. The skull defect is exposed, and an impression is taken which is used for the construction of a plaster of Paris model of the defect. Methyl methacrylate is molded to the model and thus an accurate reproduction of the skull defect is produced. The technique has the main advantage of good cosmetic appearance and strength. KEY WORDS cranioplasty 9 methyl methacrylate 9
E are presenting a new method of cranioplasty. For impression material we use alginate hydrocolloid, gas sterilized. For the construction of the skull defect model, dental quality plaster of Paris is used, also gas sterilized. The tray for the impression is made of methyl methacrylate and extensively perforated. Dental adhesive is used to increase the anchoring capacity of the tray. The skull plate is constructed from methyl methacrylate.
W
9 ,impression
9 plaster model
Technique The cranial defect is exposed and the pericranium is incised 3 to 4 mm away from the edge of the defect (Fig. 1). The incised pericranium is then removed and the edges of the defect are exposed and cleaned of scar tissue, so that there is a clear demarcation between the dura and the edge of the defect. At this point, an impression tray is made as follows. Methyl methacrylate is mixed to a doughy consistency and fashioned in the shape of the
defect. After it hardens, it is perforated extensively and sprayed with sterile dental adhesive to obtain anchoring capacity. A sterile indelible pencil is then used to mark the edge of the defect. Alginate hydrocolloid is mixed with water to a thick cream, and placed in generous amounts in the tray. The tray is then immediately pressed against the skull defect until it solidifieg (approximately 1 minute). The impression is then removed from the defect. Plaster of Paris is mixed with water and a generous amount of the mixture is used to cover the impression. When the plaster hardens (4 to 5 minutes), it is separated from the impression. The resulting model is compared with the impression and with the skull defect for accuracy and its borders are delineated with a sterile indelible pencil. Methyl methacrylate is mixed to a doughy consistency, placed in the model, and molded into a replica of the missing bone. After the plate hardens (approximately 10 minutes), it
790
J. Neurosurg. / Volume 47 / November, 1977
A new m e t h o d of cranioplasty
FIG. 1. Artist's drawing showing the steps in molding the model of the defect and placing the plate in position.
The method described has several advantages. It provides the surgeon with a system for work outside the operative field. The plaster model is an accurate replica of the skull defect, so the plate will both fit the defect perfectly and have the same contour with the missing bone. This is particularly important when the defect is in a visible area,
such as in the supraorbital and frontal regions. Also, no empty space exists to allow accumulation of fluid inside or outside the plate, with its attendant danger of infection. The uniformity in thickness with the missing bone contributes to the increased strength of the plate, since unequal thickness results in points of decreased strength. There is one further advantage. The heat release and consequent tissue irritation that may result from the direct molding of methyl methacrylate in the skull defect are eliminated. In experiments with dogs, we found that polymerization of methyl methacrylate applied directly to a skull defect raises the temperature of the epidural space from an initial level of 36 ~ to 64 ~ C despite continuous irrigation with cold saline. This rise lasts for approximately 3 minutes. Further experi-
J. Neurosurg. / Volume 47 / November, 1977
791
is removed from the model and fitted into the skull defect. Any minor irregularities may be smoothed with a pneumatic drill. A few perforations are made in the plate and it is wired to the skull in the usual manner. To this date, we have performed 10 cranioplasties with this method, producing good cosmetic results even in cases with very large defects. Discussion
T. J. Asimaeopoulos, N. Papadakis and V. H. Mark mental work by one of us has demonstrated the deleterious effect of heat on cell viability. 1
left ventricular circulatory assist device, in Bell AC, Nerem RM: 1975 Advances in Bioengineering. New York: American Society of Mechanical Engineers, 1976, pp 28-31
Reference
1. Asimacopoulos P J, McGrath J J, Cravalho EG: The thermal sensitivity of the human fibroblast HeLa S-3 as a model for thermal insult to the neointima of a nuclear-fueled, blood-cooled,
Address reprint requests to: Nikolas Papadakis, M.D., Department of Neurosurgery, Boston City Hospital, 818 Harrison Avenue, Boston, Massachusetts 02118.
792
J. Neurosurg. / Volume 47 / November, 1977
