Outcomes of Cranioplasty with Synthetic Materials and Autologous Bone Grafts

doi:10.1016/j.wneu.2015.01.014

World Neurosurgery

Volume 83, Issue 5, May 2015, Pages 708-714

https://doi.org/10.1016/j.wneu.2015.01.014 Get rights and content

Objective

Using current surgical methods, cranioplasty is associated with a high complication rate. We analyzed if there are preexisting medical conditions associated with complications and compared the effect of different implant materials on the degree of complications.

Methods

A retrospective review of the medical records of all patients who underwent cranioplasty for cranial bone defects during the period 2002–2012 was conducted, and 100 consecutive cranioplasty procedures that met eligibility criteria were identified. Patients were analyzed in 4 groups, which were created based on the cranioplasty material: autograft (n = 20), bioactive fiber–reinforced composite (n = 20), hydroxyapatite (n = 31), and other synthetic materials (n = 29). Survival estimates were constructed with Kaplan-Meier curves, and the differences between categorical variable levels were determined using a log-rank test. Multiple comparisons were adjusted using a Šidák correction.

Results

During a median follow-up time of 14 months (interquartile range 3–39 months), 32 of 100 patients (32.0%) developed at least 1 complication. A minor complication occurred in 13 patients (13.0%), whereas 19 patients (19.0%) developed a major complication, which required reoperation or removal of the implant. In the autograft subgroup, 40.0% of patients required removal of the cranioplasty. The 3-year survival of the autograft subgroup was lower compared with other subgroups of synthetic materials. In hydroxyapatite and bioactive fiber–reinforced composite groups, fewer complications were observed compared with the autograft group.

Conclusions

Based on these results, synthetic materials for cranial bone defect reconstruction exhibit more promising outcomes compared with autograft. There were differences in survival rates among synthetic materials.

Introduction

In modern neurosurgical practice, craniectomy is a common procedure that may be needed secondary to a traumatic skull bone fracture, tumor infiltration of the skull bone, a malignant middle cerebral artery infarction, or severe infection. The objective of cranioplasty—reconstruction of a skull bone defect—is to diminish the complications of a craniectomy. These complications include herniation of the cortex through the bone defect, subdural effusion, seizures, and syndrome of the trephined 13, 15. Other objectives are to restore the earlier contour of skull bone and to protect the underlying brain.

Cranioplasty is associated with a high complication rate with present surgical methods 23, 32. A postoperative complication rate of 10%–40% has been reported in large cranioplasty series 2, 6, 17, 35. Frozen autologous bone graft is traditionally used for primary reconstruction because it is readily available. However, more recent reports suggest that problems after cranioplasty with frozen bone may be more common than was thought previously 12, 18. Polymethyl methacrylate (PMMA) is used as bone cement (i.e., polymerized in situ from methyl methacrylate monomer and polymer powder mixture) and as a bulk polymer implant material. PMMA, when used in bulk polymer form, is considered a reliable and inexpensive implant material (14), which showed better long-term outcomes compared with frozen autograft (22). PMMA, when used as bone cement, causes local toxic reactions, and the material becomes encapsulated by fibrous tissues. Other commercially available materials include hydroxyapatite (HA); titanium; polyethylene (PE); polyetheretherketone (PEEK) (19); and glass fiber–reinforced composite (FRC), which is loaded with particulates of bioactive glass (BG).

Meta-analyses of available data are scarce 9, 28, 29. The optimal timing of cranioplasty and numerous associated risk factors predicting complications are unknown. In the present study, we investigated whether preexisting medical conditions are associated with complications after cranioplasty and compared the degree of complication with different surgical materials. A 10-year consecutive retrospective study was performed to analyze these after cranioplasty.

Section snippets

Selection Criteria and Study Population

We reviewed electronic medical records from all patients who underwent a skull bone defect (>4 cm²) reconstruction during a 10-year period at our tertiary care institution, which has Neurosurgical and Head and Neck surgery departments that are responsible for craniofacial reconstructive surgery of people living in Southwest Finland, Satakunta, and Åland Islands areas (combined population of 725,000). A database was generated by querying procedures with the current procedural terminology codes

Description of Sample

Altogether 100 cranioplasties (84 individual patients) with sufficient complete data were included. Of these 100 cranioplasty procedures, there were 81 primary, 16 secondary, 2 tertiary, and 1 fourth reconstruction during the period 2002–2012. A cranioplasty was performed in 34 female patients (34.0%) and 66 male patients (66.0%) with an average age of 42.1 years (range, 3–79 years). The average body mass index was 26.5 (range, 17.3–40.8).

The average defect size was 105.2 cm² (range, 4.0–420.0

Discussion

The main finding of this study was that after skull bone reconstruction with autogenous bone, the implanted bone flap needed to be removed in 40.0% of cases. Leading causes for complication and removal of the autograft were infection and resorption (25.0% and 15.0%, respectively). Survival analysis of autograft, HA, FRC, and other alloplast subgroups showed the best survival in HA and FRC groups; however, the difference compared with the autograft group was not statistically significant.

At our

Conclusions

Based on the results of the present study, synthetic cranioplasty materials show more promising outcomes compared with autograft. Even with large defect sizes, survival of FRC implants did not differ from survival of smaller defects with HA bone cement. A prospective study comparing autograft with synthetic materials is warranted to reach more in-depth conclusions.

Acknowledgment

Robert M. Badeau, Ph.D., of Aura Professional English Consulting, Ltd. (www.auraenglish.com), is acknowledged for the language content editing of the manuscript.

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Regenerative biomaterials for musculoskeletal defects must address multi-scale mechanical challenges. Repairing craniomaxillofacial bone defects, which are often large and irregularly shaped, requires close conformal contact between implant and defect margins to aid healing. While mineralized collagen scaffolds can promote mesenchymal stem cell osteogenic differentiation in vitro and bone formation in vivo, their mechanical performance is insufficient for surgical translation. We report a generative design approach to create scaffold-mesh composites by embedding a macro-scale polymeric Voronoi mesh into the mineralized collagen scaffold. The mechanics of architected foam reinforced composites are defined by a rigorous predictive moduli equation. We show biphasic composites localize strain during loading. Further, planar and 3D mesh-scaffold composites can be rapidly shaped to aid conformal fitting. Voronoi-based composites overcome traditional porosity-mechanics relationship limits while enabling rapid shaping of regenerative implants to conformally fit complex defects unique for individual patients.
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In craniomaxillofacial surgery the inclusion of lattice structure on the Cranio-implants for the surgical procedure of cranial defects is difficult. Additive manufacturing open ups a huge space for the development of intricate profiles for complex surgical practices. Designing lattice structures with various design topologies has gained more interest in the medical community for reducing the weight of the implants in the cranial region. This research proposes the mimicking of cranial defective portion concerning bone-like porous structure by means of Poly methyl methacrylate (PMMA) material via 3D printing technology. The experiments were optimized by incorporating square-type porous lattice structure in the development of cranial implants. The design-based factors of the unit cell were enhanced with the aid of the Design of experiments (DOE) technique. L₉ orthogonal array is developed by incorporating various design-based factors of the lattice unit cell like unit cell size (mm), skewing angle (°), wall thickness (mm), and unit cell orientation (°). The experiments are optimized with respect to obtaining better compressive strength and compressive strength/density of the prepared lattice structure incorporated polymeric samples. The result shows that for obtaining the maximum compressive strength in the porous square lattice-structured PMMA compression samples will be a lower cell size of 2 mm, a higher skewing angle of 30°, a higher wall thickness of 1 mm, and a unit cell orientation of 90°. The experimental optimized condition results of the design-based factors achieve the maximum compressive strength and compressive strength/density of 83.37 MPa and 189.73 MPa/g mm⁻³. The lattice structure orientated with 90° has a significant contribution towards reducing the development of structural deviations of incorporating square lattice structure on the PMMA polymeric material. Therefore, the topologically modified square lattice structure incorporated 3D printed PMMA material has a potential scope for the replacement of conventional maxillofacial cranial implants.
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Patients who underwent cranioplasty from 1 January 2014 to 31 December 2020 at University Medical Center Utrecht and a control group consisting of our center’ employees were invited to fill out the Craniofacial Surgery Outcomes Questionnaire (CSO-Q), consisting of an assessment of cosmetic satisfaction, the Rosenberg Self-Esteem Scale (RSES), and the FNE scale. To test for differences in results, chi-square tests and T-tests were performed. Logistic regression was used to study the effect of cranioplasty-related variables on cosmetic satisfaction.
Cosmetic satisfaction was seen in 44/80 patients (55.0%) and 52/70 controls (74.3%) (p = 0.247). Thirteen patients (16.3%) and 8 controls (11.4%) had high self-esteem (p = 0.362), 51 patients (63.8%) and 59 controls (84.3%) had normal self-esteem (p = 0.114), and 7 patients (8.8%) and 3 controls (4.3%) had low self-esteem (p = 0.337). Forty-nine patients (61.3%) and 39 controls (55.7%) had low FNE (p = 0.012), 8 patients (10.0%) and 18 controls (25.7%) had average FNE (p = 0.095), and 6 patients (7.5%) and 13 controls (18.6%) had high FNE (p = 0.215). Cosmetic satisfaction was associated with glass fiber-reinforced composite implants (OR 8.20, p-value = 0.04).
This study prospectively evaluated PROMs following cranioplasty, for which we found favorable results.
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Decompressive craniectomy (DC) is a surgical procedure, that is followed by cranioplasty surgery. DC is usually performed to treat patients with traumatic brain injury, intracranial hemorrhage, cerebral infarction, brain edema, skull fractures, etc. In many published clinical case studies and systematic reviews, cranioplasty surgery is reported to restore cranial symmetry with good cosmetic outcomes and neurophysiologically relevant functional outcomes in hundreds of patients. In this review article, we present a number of key issues related to the manufacturing of patient-specific implants, clinical complications, cosmetic outcomes, and newer alternative therapies. While discussing alternative therapeutic treatments for cranioplasty, biomolecules and cellular-based approaches have been emphasized. The current clinical practices in the restoration of cranial defects involve 3D printing to produce patient-specific prefabricated cranial implants, that provide better cosmetic outcomes. Regardless of the advancements in image processing and 3D printing, the complete clinical procedure is time-consuming and requires significant costs. To reduce manual intervention and to address unmet clinical demands, it has been highlighted that automated implant fabrication by data-driven methods can accelerate the design and manufacturing of patient-specific cranial implants. The data-driven approaches, encompassing artificial intelligence (machine learning/deep learning) and E-platforms, such as publicly accessible clinical databases will lead to the development of the next generation of patient-specific cranial implants, which can provide predictable clinical outcomes.
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Materials Used in Cranial Reconstruction: A Systematic Review and Meta-Analysis
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Cranioplasty is a common neurologic procedure, with complication rates ranging from 20% to 50%. It is hypothesized that the risks of various complications are affected by which material is used for cranioplasty.
To evaluate the literature comparing rates of complications after cranioplasty using different materials including autologous bone, hydroxyapatite, methyl methacrylate, demineralized bone matrix, polyetheretherketone, titanium, or composite materials.
The PubMed/MEDLINE database was searched for relevant articles published between 2010 and 2020. After screening, 35 articles were included. Outcomes included infection, wound problems, poor cosmesis, overall complications, duration of surgery, and length of stay. For each outcome, a frequentist network meta-analysis was conducted to compare materials used.
The risk of infection was 1.62 times higher when methyl methacrylate was used compared with autologous bone (relative risk, 1.62; 95% confidence interval [CI], 1.07–2.45). Length of stay after cranioplasty was on average 3.62 days shorter when titanium was used compared with autologous bone (95% CI, 6.26 to –0.98). The networks constructed for other outcomes showed moderate to substantial between-study heterogeneity, wide CIs, and no significant differences between materials.
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: Conflict of interest statement: This research was funded by the Emil Aaltonen Foundation and Turku University Hospital. The principal financing partners of the FRC implant research are Tekes (the Finnish Agency for Technology and Innovation), Academy of Finland, and European Commission (Grant No. NEWBONE NMP3-CT-006-026279-2). J.M.P., J.P.P., and V.V. have received financial support in the form of a congress fee and travel expenses from Skulle Implants Corporation. K.M.J.A. and P.K.V. are board members and shareholders of the start-up company Skulle Implants Corporation, which is aiming to commercialize FRC implants. T.K. does not have any conflicts of interest to declare.

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ForumOutcomes of Cranioplasty with Synthetic Materials and Autologous Bone Grafts

Objective

Methods

Results

Conclusions

Introduction

Section snippets

Selection Criteria and Study Population

Description of Sample

Discussion

Conclusions

Acknowledgment

Clin Neurol Neurosurg

World Neurosurg

World Neurosurg

Bone

J Plast Reconstr Aesthet Surg

Clin Neurol Neurosurg

Craniofacial bone reconstruction with bioactive fiber-reinforced composite implant

Head Neck

Long-term results following titanium cranioplasty of large skull defects

Neurosurg Focus

Outcomes of cranial repair after craniectomy

J Neurosurg

Routine but risky: a multi-centre analysis of the outcomes of cranioplasty in the northeast of england

Acta Neurochir (Wien)

The fate of preserved autogenous bone graft

Plast Reconstr Surg

Development of a bioactive implant for repair and potential healing of cranial defects

J Neurosurg

Cranioplasty: indications and advances

Curr Opin Otolaryngol Head Neck Surg

Complications of cranioplasty following decompressive craniectomy: analysis of 62 cases

Neurosurg Focus

A 1-year study of osteoinduction in hydroxyapatite-derived biomaterials in an adult sheep model: part I

Plast Reconstr Surg

How “successful” is calvarial reconstruction using frozen autologous bone?

Plast Reconstr Surg

Long-term complications of decompressive craniectomy for head injury

J Neurotrauma

Long-term clinical outcome analysis of poly-methyl-methacrylate cranioplasty for large skull defects

J Oral Maxillofac Surg

Forum
Outcomes of Cranioplasty with Synthetic Materials and Autologous Bone Grafts