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The construction and implantation of a silicone rubber cranial prosthesis
Maxillofacial prosthetics
The construction cranial Bernard
and
implantation
of a silicone
rubber
prosthesis W. Segall,
D.M.D.*
Regional (:enter fog- Maxillo~a&l Prosthetics, Ear Hospital oj Pittsburgh, Pittsburgh, Pa.
The Eye and
A
large variety of biologic and nonbiologic materials have been used for cranioplasty. They include autogenous bone, tantalum, acrylic resins, and silicone rubber. The use of bone grafts in the reconstruction of large cranial defects has proved unsatisfactory due to postoperative absorption of the bone graft. Tantalum is difficult to prepare. Acrylic resin, although easy to work with, requires time-consuming procedures in the molding of accurately fitting prostheses. However, several studies and clinical experiments have demonstrated that silicone rubber provides an excellent synthetic compound, characterized by lack of reaction, maleability similar to that of human soft tissue, and complete resistance to attack by the human body. In addition, it requires relatively simple techniques in carving and is known to yield superior cosmetic results. Speirs and Blocksmal proved the inertness of silicone rubber and its safety for use in implants. Courtemanche and Thompson2 found SUCcessful use for silicone rubber in reconstruction of craniofacial defects. in 1969, Dickinson and associates” also reported success in the use of medical-grade silicone implant materials in frontal reconstructions. This article delineates the technique involved in the construction and implantation of a silicone rubber cranial prosthesis.
MATERIALS
AND
METHODS
Preoperative construction. In order to prepare the patient for an accurate impression, all hair is removed from the scalp in the area of the defect, and the defect is outlined in indelible pencil. The impression of the depressed area is made with irreversible hydrocolloid. When this has hardened, ‘quick-setting Kerr No. 2 plaster is placed over it to act as a tray. A positive cast is made of dental stone, and the indelible line is automatically transferred onto the stone cast. The depression on the cast is filled with baseplate wax, 0.5 cm. in excess of the delineated lines, to allow for variations in the size of the actual bony defect (Fig. 1) , Subsequently, the wax is smoothed to the outline of the cranium. It is then carefuly removed from the *Director. 194
Silicone
Fig. 1. Positive
rubber
cranial
prosthesis
195
cast with wax implant.
Fig. 2. Stone mold after elimination
of wax.
Fig. 3. Fenestrated
implant.
positive cast and invested into a two-piece mold made of dental stone. When the curing flask is opened, the wax is eliminated by boiling (Fig. 2). A mixture of No. 382 medical-grade silicone and a proportional amount of stannous actuate catalyst is placed into the mold, which is then tightly closed. When the material has hardened, the flask is opened, and the silicone implant is removed. (There is no need for a separating medium when using silicone, as it does not adhere to dental stone.) The excess silicone is trimmed along the edges of the implant prosthesis, and holes are drilled 0.5 cm. distant with a No. 8 round dental bur (Fig. 3). (This is necessary to insure penetration of fibrous tissue through the holes of the prosthesis, thereby fixing the implant to the surrounding tissue.) As a last step, the implant is thoroughly scrubbed and autoclaved in a stainless steel dish. When removed, it should not come in contact with any lint-producing materials. The silicone rubber prosthesis is now ready for implantation. If it seems that the implant may be too small, two or three slightly larger implants could be prepared in the same way. Surgical procedure. Once the defect has been completely exposed surgically, the implant is tried directly on the skull. If the prosthesis is too large in any specific area, it can be easily cut down to the correct shape with a scalpel, but this is seldom necessary because of the accuracy of the preliminary construction. If the defect is
196
Segall
J. Prosthet. Dent. February, 1974
Fig. 4. Defect prior to reconstruction. Fig. 5. Reconstructed defect. shallow, sutures must be placed to hold the prosthesis in position and give it adequate fixation until fibrosis encapsulates the implant. If the defect has sufficient depth, and there is no risk of displacement of the implant, sutures are not required. The flap is now replaced over the corrected defect and sutured into place. REPORT OF A PATIENT A 19-year-old man with a history of aspergillosis of the frontal sinus underwent frontal sinus aspiration in November, 1970, resulting in a diagnosis of aspergillosis. On exploring the frontal sinus, it was noted that there was considerable bone erosion with a large defect due to surgery and disease. On March 29: 1971, the patient was admitted to Eye and Ear Hospital for reconstructive surgery, and on March 31, 1971, he underwent correction of the frontal deformity with a No. 382 medical-grade silicone implant. Operatiue procerlure. Following adequate premeditation, the patient was brought to the operating room where a general endotracheal anesthesia was administered. A bicoronal-type incision was then made, beginning above the ear on the left and carried across coronally to the opposite side. The incision was carried through the subcutaneous layers and to the periosteum. Brisk bleeding was controlled with hemostats which were then grouped in rubber bands and used for retraction. The periosteum QZS then elevated off the temporal bone bilaterally and elevated anteriorly to expose the frontal defect. Careful elevation was carried out over the previously formed frontal defect; there were no dural tears. It was noted that the previously placed fascia graft was intact, with good support of the inner table of the frontal sinus. The defects in the left orbital rim superiorly and right orbital rim medially were noted. and careful dissection was then performed down into the glabellar angle. At no time was any nasal frontal communication noted. It was thought that the previously placed fascia and muscle plug were adequate. A previously contoured, medical-grade, silicone implant was then placed in the defect and contoured about the edges. A good? or excellent, contour was obtained when
Volume31 Number2
Silicone
rubber
cranial
prosthesis
197
the forehead flap was replaced. It did not seem necessary to suture the implant in place because of the good fit and the tension of the forehead flap over the defect. The bicoronal flap was then closed with 3-O silk approximating the periosteum, followed by 2-O silk subcutaneously approximating the scalp, followed by 4-O silk in a running horizontal-vertical mattress-type suture. A pressure dressing was placed on the head and over the eyes. The patient tolerated the procedure well and left the operating room in good condition. Postoperative procedure. The patient’s postoperative course was relatively benign. The skin sutures were removed on the seventh and eighth postoperative days, after which he was discharged from the hospital. On follow-up observation, the contour of the silicone implant was noted to be satisfactory (Figs. 4 and 5). CONCLUSION Silicone is ideal for use in cranioplasty because of its physical properties, its similarity in softness to living tissue, and the facility with which it can be molded into shape and fitted onto the area to be reconstructed. References 1. Speirs, A. C., and Blocksma, R.: New Implantable Silicone Rubbers, Plast. Reconstr. Surg. 31: 166-175, 1963. 2. Courtemanche, A. D., and Thompson, G. B.: Silastic Cranioplasty Following Cranio-Facial Injuries, Plast. Reconstr. Surg. 41: 165-170, 1968. 3. Dickinson, J. T., Cepcic, J. A., and Kamerer, D. B.: Principles of Frontal Reconstruction, Laryngoscope 79: 1019-1075, 1969.
DEPARTMENTOF ORAL SURGERY JACKSON MEMORIAL HOSPITAL 1150 N. W. 14TH ST.,No.500
MIAMI,FLA. 33136
The construction cranial Bernard
and
implantation
of a silicone
rubber
prosthesis W. Segall,
D.M.D.*
Regional (:enter fog- Maxillo~a&l Prosthetics, Ear Hospital oj Pittsburgh, Pittsburgh, Pa.
The Eye and
A
large variety of biologic and nonbiologic materials have been used for cranioplasty. They include autogenous bone, tantalum, acrylic resins, and silicone rubber. The use of bone grafts in the reconstruction of large cranial defects has proved unsatisfactory due to postoperative absorption of the bone graft. Tantalum is difficult to prepare. Acrylic resin, although easy to work with, requires time-consuming procedures in the molding of accurately fitting prostheses. However, several studies and clinical experiments have demonstrated that silicone rubber provides an excellent synthetic compound, characterized by lack of reaction, maleability similar to that of human soft tissue, and complete resistance to attack by the human body. In addition, it requires relatively simple techniques in carving and is known to yield superior cosmetic results. Speirs and Blocksmal proved the inertness of silicone rubber and its safety for use in implants. Courtemanche and Thompson2 found SUCcessful use for silicone rubber in reconstruction of craniofacial defects. in 1969, Dickinson and associates” also reported success in the use of medical-grade silicone implant materials in frontal reconstructions. This article delineates the technique involved in the construction and implantation of a silicone rubber cranial prosthesis.
MATERIALS
AND
METHODS
Preoperative construction. In order to prepare the patient for an accurate impression, all hair is removed from the scalp in the area of the defect, and the defect is outlined in indelible pencil. The impression of the depressed area is made with irreversible hydrocolloid. When this has hardened, ‘quick-setting Kerr No. 2 plaster is placed over it to act as a tray. A positive cast is made of dental stone, and the indelible line is automatically transferred onto the stone cast. The depression on the cast is filled with baseplate wax, 0.5 cm. in excess of the delineated lines, to allow for variations in the size of the actual bony defect (Fig. 1) , Subsequently, the wax is smoothed to the outline of the cranium. It is then carefuly removed from the *Director. 194
Silicone
Fig. 1. Positive
rubber
cranial
prosthesis
195
cast with wax implant.
Fig. 2. Stone mold after elimination
of wax.
Fig. 3. Fenestrated
implant.
positive cast and invested into a two-piece mold made of dental stone. When the curing flask is opened, the wax is eliminated by boiling (Fig. 2). A mixture of No. 382 medical-grade silicone and a proportional amount of stannous actuate catalyst is placed into the mold, which is then tightly closed. When the material has hardened, the flask is opened, and the silicone implant is removed. (There is no need for a separating medium when using silicone, as it does not adhere to dental stone.) The excess silicone is trimmed along the edges of the implant prosthesis, and holes are drilled 0.5 cm. distant with a No. 8 round dental bur (Fig. 3). (This is necessary to insure penetration of fibrous tissue through the holes of the prosthesis, thereby fixing the implant to the surrounding tissue.) As a last step, the implant is thoroughly scrubbed and autoclaved in a stainless steel dish. When removed, it should not come in contact with any lint-producing materials. The silicone rubber prosthesis is now ready for implantation. If it seems that the implant may be too small, two or three slightly larger implants could be prepared in the same way. Surgical procedure. Once the defect has been completely exposed surgically, the implant is tried directly on the skull. If the prosthesis is too large in any specific area, it can be easily cut down to the correct shape with a scalpel, but this is seldom necessary because of the accuracy of the preliminary construction. If the defect is
196
Segall
J. Prosthet. Dent. February, 1974
Fig. 4. Defect prior to reconstruction. Fig. 5. Reconstructed defect. shallow, sutures must be placed to hold the prosthesis in position and give it adequate fixation until fibrosis encapsulates the implant. If the defect has sufficient depth, and there is no risk of displacement of the implant, sutures are not required. The flap is now replaced over the corrected defect and sutured into place. REPORT OF A PATIENT A 19-year-old man with a history of aspergillosis of the frontal sinus underwent frontal sinus aspiration in November, 1970, resulting in a diagnosis of aspergillosis. On exploring the frontal sinus, it was noted that there was considerable bone erosion with a large defect due to surgery and disease. On March 29: 1971, the patient was admitted to Eye and Ear Hospital for reconstructive surgery, and on March 31, 1971, he underwent correction of the frontal deformity with a No. 382 medical-grade silicone implant. Operatiue procerlure. Following adequate premeditation, the patient was brought to the operating room where a general endotracheal anesthesia was administered. A bicoronal-type incision was then made, beginning above the ear on the left and carried across coronally to the opposite side. The incision was carried through the subcutaneous layers and to the periosteum. Brisk bleeding was controlled with hemostats which were then grouped in rubber bands and used for retraction. The periosteum QZS then elevated off the temporal bone bilaterally and elevated anteriorly to expose the frontal defect. Careful elevation was carried out over the previously formed frontal defect; there were no dural tears. It was noted that the previously placed fascia graft was intact, with good support of the inner table of the frontal sinus. The defects in the left orbital rim superiorly and right orbital rim medially were noted. and careful dissection was then performed down into the glabellar angle. At no time was any nasal frontal communication noted. It was thought that the previously placed fascia and muscle plug were adequate. A previously contoured, medical-grade, silicone implant was then placed in the defect and contoured about the edges. A good? or excellent, contour was obtained when
Volume31 Number2
Silicone
rubber
cranial
prosthesis
197
the forehead flap was replaced. It did not seem necessary to suture the implant in place because of the good fit and the tension of the forehead flap over the defect. The bicoronal flap was then closed with 3-O silk approximating the periosteum, followed by 2-O silk subcutaneously approximating the scalp, followed by 4-O silk in a running horizontal-vertical mattress-type suture. A pressure dressing was placed on the head and over the eyes. The patient tolerated the procedure well and left the operating room in good condition. Postoperative procedure. The patient’s postoperative course was relatively benign. The skin sutures were removed on the seventh and eighth postoperative days, after which he was discharged from the hospital. On follow-up observation, the contour of the silicone implant was noted to be satisfactory (Figs. 4 and 5). CONCLUSION Silicone is ideal for use in cranioplasty because of its physical properties, its similarity in softness to living tissue, and the facility with which it can be molded into shape and fitted onto the area to be reconstructed. References 1. Speirs, A. C., and Blocksma, R.: New Implantable Silicone Rubbers, Plast. Reconstr. Surg. 31: 166-175, 1963. 2. Courtemanche, A. D., and Thompson, G. B.: Silastic Cranioplasty Following Cranio-Facial Injuries, Plast. Reconstr. Surg. 41: 165-170, 1968. 3. Dickinson, J. T., Cepcic, J. A., and Kamerer, D. B.: Principles of Frontal Reconstruction, Laryngoscope 79: 1019-1075, 1969.
DEPARTMENTOF ORAL SURGERY JACKSON MEMORIAL HOSPITAL 1150 N. W. 14TH ST.,No.500
MIAMI,FLA. 33136