Resin sealant: a new method of methyl methacrylate cranioplasty. Technical note

Craniofacial Prosthetic Reconstruction Using Polymethyl Methacrylate Implant: A Case Report

Large cranial defects of complex geometric shapes are challenging to reconstruct. The cranial implants has to be fabricated prior to the cranioplastic surgery. The ideal material for cranial implant has to be inert, light weight, easy to fit and adaptable to the defect, offering the best aesthetic and functional results. Here is a clinical case report of a patient who was operated for osteomyelitis in the parieto-temporal region. The defect was reconstructed with heat cure polymethylmethacrylate (PMMA). Operative closure of the defect was facilitated with ligature titanium wires with minimal prosthesis contouring. The heat cure PMMA cranial implant is a safe, easy and economic alternative with great adaptability to cranial vault defects. The cosmetic results in this patient was excellent. No post-operative complications occurred.

Aesthetic refinement of secondary cranioplasty using methyl methacrylate bone cements

BACKGROUND

Cranioplasty using alternate alloplastic bone substitutes instead of autologous bone grafting is inevitable in the clinical field. The authors present their experiences with cranial reshaping using methyl methacrylate (MMA) and describe technical tips that are keys to a successful procedure.

METHODS

A retrospective chart review of patients who underwent cranioplasty with MMA between April 2007 and July 2010 was performed. For 20 patients, MMA was used for cranioplasty after craniofacial trauma (n = 16), tumor resection (n = 2), and a vascular procedure (n = 2). The patients were divided into two groups. In group 1, MMA was used in full-thickness inlay fashion (n = 3), and in group 2, MMA was applied in partial-thickness onlay fashion (n = 17). The locations of reconstruction included the frontotemporal region (n = 5), the frontoparietotemporal region (n = 5), the frontal region (n = 9), and the vertex region (n = 1). The size of cranioplasty varied from 30 to 144 cm(2).

RESULTS

The amount of MMA used ranged from 20 to 70 g. This biomaterial was applied without difficulty, and no intraoperative complications were linked to the applied material. The patients were followed for 6 months to 4 years (mean, 2 years) after MMA implantation. None of the patients showed any evidence of implant infection, exposure, or extrusion. Moreover, the construct appeared to be structurally stable over time in all the patients.

CONCLUSIONS

Methyl methacrylate is a useful adjunct for treating deficiencies of the cranial skeleton. It provides rapid and reliable correction of bony defects and contour deformities. Although MMA is alloplastic, appropriate surgical procedures can avoid problems such as infection and extrusion. An acceptable overlying soft tissue envelope should be maintained together with minimal contamination of the operative site.

LEVEL OF EVIDENCE V

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Anchoring of methylmethacrylate filler to the calvarium--technical note

Implanted methylmethacrylate may be unexpectedly displaced due to poor adherence to the bone. We developed a simple technique to fix the material plugging the burr holes for use primarily in cosmetically important areas. At the closure of craniotomy, 2-3 small drill holes are made at the rim of the craniotomy burr hole. To address cranial defects in the pterional region, small holes are placed on the bone surface around the key burr hole. The holes extend into the diploic layer and have no parallel relationship. After fixation of the bone flap, a methylmethacrylate filler mixture is manually plugged into the burr hole and pushed into the small holes, thereby forming horns for secure fixation. None among over 100 patients developed an objectionable bulge attributable to displacement of the filler. Our technique requires no special instruments or materials and decreases the risk of cosmetic problems.

Evaluation of polymethylmethacrylate adhesion: a comparison of direct onlay versus screw anchoring techniques

Polymethylmethacrylate (PMMA) is still the most frequently used alloplastic material for calvarial reconstruction, especially when dealing with large bony defects. It is strong, provides good protection to the underlying cerebral structures, and is stable and minimally reactive. One of the disadvantages of this material is its tendency to become loose over time because of its poor adherence to bone. Onlay miniscrews in improving PMMA's adhesion to bone have been previously proposed. A series of experiments were conducted to evaluate whether placement of screw anchors will significantly improve the adhesion force between the polymer and bony surface.

METHODS

Four fresh-frozen cadaver heads were used for this experiment. The PMMA preparation and setup time strictly followed manufacturer guidelines. Two experimental groups were created: (1) PMMA was placed on the subperiosteal bony surface with increasing surface areas (areas: 1-20 cm2), and (2) a standard area of 16 cm2 PMMA was placed on the bony surface with an increasing number of titanium miniscrews (number of screws: 0-5). The force required to separate the material from the underlying bone was assessed using a digital pull force gauge (Imada DPS-44) through vertical traction. The experiments were undertaken in triplicate; the results were statistically analyzed using Student t test.

RESULTS

Experiment 1: increasing forces were required as the surface area of PMMA application increased (1.2-42.3 N). The most consistent measurements with a low SD were obtained on the 16-cm2 implant, which was chosen for experiment 2. A 16-cm2 area would allow for the placement of up to 5 screws without technical difficulty. Experiment 2: higher forces were needed to detach the material, with increasing screw placement (1, 79; 2, 132.5; 3, 194.2; and 4 and 5, >196.1 N). In 73 of 75 experiments, the screws remained attached to the PMMA after separation. When the PMMA alone on a 16-cm2 surface area was compared with the placement of one or more screws, the force of adhesion significantly increased for all groups (P < 0.01). There was a 2.6x increase in this force with 1 screw, 4.4x with 2, 6.4x with 3, and 6.5x with 4 or more screws. Three or more miniscrews provided sufficient stabilization to anchor an implant firmly in place while resisting large traction forces.

CONCLUSION

Although greater surface areas of PMMA will increase the adhesion force between the polymer and bone, a clinically and statistically significant increase in this force may only be achieved with the use of miniscrews.

In situcranioplasty with methylmethacrylate and wire lattice

Most techniques of cranioplasty are expensive and require advance preparation if a custom-moulded prosthesis is to be used. Technical problems with cranioplasties using synthetic materials include sinking, elevation and rotation, while those with hydroxyapatite or bone graft cranioplasties include resorption and harvest site disfigurement. We report our technique of in situ cranioplasty using methylmethacrylate and a wire lattice that is fast, inexpensive and avoids these technical problems.

A new technique for cranioplasty with L-shaped titanium plates and combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite)

OBJECTIVE

The use of hydroxyapatite-based ceramics for cranioplasties has recently increased in Japan, because of the good cosmetic outcomes, biocompatibility, strength, osteoconductive properties, and lack of risk of disease transmission associated with these materials. However, miniplate fixation has not been possible for ceramic implants. We describe a new technique for miniplate fixation of ceramic implants.

METHODS

Combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite; NGK Spark Plug Co., Aichi, Japan) were used for cranioplasties. A slot and a pair of holes were cut in each Ceratite implant, for use as a fixation unit. We have also developed a new L-shaped titanium plate (HOMS Engineering Inc., Nagano, Japan) that fits into the fixation unit. We first insert an L-shaped titanium plate through the slot from the back surface of the Ceratite implant. We then bend the plate outward at the front surface of the Ceratite implant and fix it to the cranium of the patient with titanium screws. The Ceratite implant is usually firmly fixed to the cranium of the patient with three L-shaped titanium plates.

RESULTS

Using L-shaped titanium plates and Ceratite implants, we successfully performed cranioplasties for seven patients with cranial defects resulting from external decompression craniotomies. The Ceratite implant exactly fit the bone window for each patient. Surgical maneuvers were simple and easy for all patients, permitting shorter operating times. All Ceratite implants were firmly fixed, and no postoperative infections have occurred.

CONCLUSION

Our new technique for cranioplasty is simple and allows rigid fixation of Ceratite implants.

Validation of computer-assisted manufacture of titanium plates for cranioplasty

We have constructed 300 titanium cranioplasty plates, over 150 cases using a computerised technique, the remainder by external impression. The clinical follow-up of these cases over 8 years has shown consistently good results that justify our simple low-cost method of manufacturing these plates. Both techniques require the provision of a model on which to construct the plate. In the traditional technique, an approximate model is derived from the resected bone or a direct impression of the defect over the patient's scalp. Using the computerised technique, a more accurate model of the defect and the surrounding bone is milled in polyurethane foam from cross-sectional computerised tomographic (CT) scans. Sheet titanium is pressed to shape from a design outlined on a counterdie. The subsequent stages of the plate construction are then the same for both methods. This study describes the stages of the model manufacture, the validation of its accuracy and the plate construction that follows. Use of the computerised method has resulted in a reduction of errors, enabling the manufacture of a smaller plate than was possible previously. It has also enabled design changes through the achievement of greater accuracy in fit.

Skull reconstruction with a two-part interlocking custom-made titanium plate

We have used a two-part interlocking titanium plate for cranioplasty in two patients with large skull defects in which reconstruction with a titanium plate was required and extensive contouring of the plate was necessary.

Cardiac dilatation after cardiopulmonary bypass: ceramic plate technique for sternal splinting

Intraoperative sternal closure after cardiopulmonary bypass in patients with cardiac dilatation and dysfunction may cause fatal deterioration of their hemodynamics. To avoid this complication, a ceramic plate made from methyl methacrylate was used for sternal splinting. This simple splint can avoid chest wall compression to the overdilated heart, maintaining stable hemodynamics after cardiopulmonary bypass without postoperative respiratory complications or mediastinal infection.