Osteogenic biodegradable plates for cranioplasty in 6 patients across different age groups: clinical failure of promising concept? Patient series

Abstract

BACKGROUND

Reconstruction of cranial bone defects after craniotomy remains a contemporary neurosurgical challenge, necessitating an ongoing search for optimal synthetic materials that ensure effective healing, minimal postoperative complications, and satisfactory cosmetic outcomes. This issue is particularly critical in pediatric patients, in whom the dynamic nature of skull growth presents additional reconstructive complexities. Biodegradable implants with osteogenic and osteoconductive properties represent a promising solution, aiming to reduce complications commonly associated with rigid materials, such as skull deformation, and to enable gradual replacement of implants with native bone tissue.

OBSERVATIONS

In this study, the authors report a series of 6 cranioplasty procedures utilizing CyberBone implants, involving 4 pediatric patients of varying ages and 2 adults. Despite the theoretical advantages of these implants, their clinical experience did not meet expectations in terms of mechanical stability, aesthetic outcomes, or evidence of osteointegration.

LESSONS

Complications of varying severity, including implant deformation, resorption without adequate bone substitution, and poor cosmetic results, occurred in all patients. Based on these outcomes, the authors do not recommend CyberBone implants for routine clinical use in cranial reconstructions. Further material refinement and comprehensive safety studies are warranted before considering broader implementation in pediatric and adult populations.

https://thejns.org/doi/10.3171/CASE25570

Cranioplasty is an essential step following neurosurgical procedures involving craniotomy aimed at restoring skull integrity for protection, cosmesis, and physiological homeostasis. Autologous bone remains the gold standard because of its excellent biocompatibility, osteoconductive and osteoinductive properties, and low cost. It can be used either immediately or after preservation via cryopreservation or subcutaneous storage.^1–3 However, autologous bone resorption remains a significant concern in pediatric patients, particularly with cryopreserved grafts.⁴

When autologous reconstruction is not feasible due to infection, trauma, or loss of bone, synthetic materials such as titanium, polymethylmethacrylate, and hydroxyapatite are commonly used. These materials allow precise, patient-specific reconstruction using 3D planning and are well established in adult cranioplasty.⁵ However, in the pediatric population, rigid implants may impair cranial growth, leading to deformities and potentially necessitating reoperation.^2,6–8

The rapid expansion of the pediatric skull during early development, reaching 80% of the adult brain volume by age 2 years—is tightly coupled to mechanical and biological signaling from the dura mater, which plays a central role in osteogenesis.^9,10 This has driven interest in bioresorbable materials that can degrade over time while supporting bone regeneration, particularly in growing children.⁵ Despite promising in vitro and preclinical results, the clinical performance of these implants remains under scrutiny.

Recent reports have raised concerns regarding the mechanical reliability and biological behavior of bioresorbable implants under physiological and traumatic stress, including implant fractures and poor integration.¹¹ Cranioplasty in pediatric patients continues to face unresolved challenges, including high rates of graft resorption, infection, and implant failure.^6,12–16 Therefore, the search for an ideal cranioplasty material, especially for children, remains an ongoing effort.

This study presents a clinical case series evaluating the performance of CyberBone (Syntplant Ltd.), a biodegradable osteogenic implant, in pediatric and adult cranioplasty. We aimed to critically assess its clinical efficacy, integration, and safety in real-world surgical settings.

None of the CyberBone implants used in this study were CE certified under Regulation (European Union [EU]) 2017/745 on medical devices. However, according to Article 52(8) of the Medical Device Regulation (MDR), custom-made medical devices are exempt from mandatory clinical investigations and notified body conformity assessments prior to market placement. All implants were classified as custom-made and provided by the manufacturer, along with the required documentation, including a declaration of conformity, design specifications, and confirmation of compliance with Annex XIII of the MDR. The surgical teams were fully aware of the regulatory status, the procedures were performed with appropriate ethical approval, and informed consent was obtained from the patients’ legal guardians.

Study Description

Six cranial reconstruction procedures were performed by specialists at the Department of Neurosurgery, National Specialized Children’s Hospital Ohmatdyt and the National Cancer Institute (Kyiv, Ukraine), involving patients of different age groups—4 pediatric and 2 adult cases. All procedures used custom-designed biodegradable osteogenic implants (CyberBone). Each implant was individually fabricated to meet patient-specific anatomical and developmental requirements. Denser rigid constructs were used for adults, whereas more flexible and compliant versions were selected for pediatric patients to provide both adequate initial mechanical strength and the potential to accommodate skull growth over time through adaptive expansion and integration with the surrounding bone. It is necessary to notice that, after unsuccesful results in first 3 pediatric patients, a special form of the implant was produced by the manufacturer with a gyroid surface and 3-mm offset from the skull to provide better cosmesis and faster osseiontegration.

All implants were patient specific and provided free of charge by the manufacturer as a part of a charitable contribution. Intraoperatively, there were no notable differences between CyberBone implants, autologous bone, or titanium plates in terms of handling characteristics or early cosmetic outcomes. On average, the time from preoperative cranial CT imaging for implant planning to the final surgical procedure was approximately 1.5 months. All procedures were uneventful, and the early postoperative cosmetic results were satisfactory.

Patient 1

A 5-year-old boy presented with a cranial defect in the left frontotemporoparietal region (approximately 12 × 10 cm) after decompressive craniectomy. The defect exhibited cranial asymmetry and brain pulsation through the scalp. The implant was fixed using titanium plates.

At 6 months postoperatively, cosmetic outcomes were acceptable; however, CT showed a fracture in one elastic segment for skull growth. No trauma was reported and the implant remained firm on palpation.

From 7 months postoperatively, progressive implant deformation was noted. By 12 months postoperatively, imaging showed a complete vertical fracture of the central portion of the implant, with inward displacement toward the brain and overlapping fragments, creating a wedge-shaped deformity. The implant remained rigid during the examination.

CT imaging at 12 months showed limited ossification near the elastic zones and bone margins without osteointegration (Fig. 1). The patient’s mother chose conservative management, deferring revision until completion of the growth phase or if neurological symptoms developed.

FIG. 1.

Patient 1. Progressive deformation of the implant. Observation period: 35 months. A: Three-dimensional model of the skull before implantation. B: CT scan with 3D reconstruction obtained immediately after implantation. The implant is fixed with titanium plates. C: Three-dimensional model of the skull 7 months postoperatively. Asymmetry and early implant deformation are visible. D: CT scan obtained 7 months after surgery, showing early signs of deformation and focal osteogenesis. E: CT scan obtained 13 months after surgery. Progressive deformation of the implant is evident. F: Three-dimensional model 13 months postoperatively demonstrating severe deformation of the implant.

Patient 2

A 7-year-old male patient underwent cranioplasty for a left temporoparietal cranial defect (approximately 6 × 8 cm) following decompressive craniectomy. The defect was camouflaged by hair with mild asymmetry. The implant was fixed to native bone using bone sutures.

At 18 months postoperatively, the skull contour remained symmetric, with the implant well aligned and firm. A marginal gap of 0.3–0.4 cm was formed between the implant and native bone due to skull growth. Early ossification foci were observed along implant margins, indicating limited integration.

By 25 months postoperatively, the parents reported implant softness and brain pulsations after physical activity. CT imaging showed implant swelling and reduced density from 190 Hounsfield units (HU) to 100 HU centrally and 35 HU peripherally, suggesting degradation. The ossification zones remained between 300 and 400 HU.

At 31 months postoperatively, the patient presented with erythema and swelling at the bone-implant junction. CT imaging revealed implant thickening up to 1 cm, loss of defined margins, and implant density of 90–20 HU, confirming ongoing lysis without bone substitution (Fig. 2).

FIG. 2.

Patient 2. Implant lysis. Observation period: 31 months. A:Implant preoperative design. B: Three-dimensional model 14 months after surgery. Osteogenic points are visible between the implant’s growth zones. No osteointegration is observed between the implant and skull. C: Three-dimensional model of the skull 24 months postoperatively. Caregivers noted visible brain pulsation through the implant. D: CT scan showing structural loosening of the implant. E: Three-dimensional model of the skull with a spongy implant before debridement and removal. F: Three-dimensional model highlighting osteogenic zones within the implant.

Two weeks later, the patient presented with progressive swelling and erythema. Emergency surgery revealed complete implant lysis with a purulent material. The implant remnants appeared as porous, yellow-gray masses with inflammation extending into the surrounding tissues.

Surgical debridement was performed, and the fragments were collected for analysis. Reconstruction was postponed due to inflammation. Histopathology showed dense connective tissue with macrophages and giant cells containing dispersed inorganic material, and fibrous tissue with granulomatous inflammation.

Patient 3

An 8-year-old male presented with a posttraumatic cranial bone defect in the right temporoparietal region (approximately 6 × 6 cm) after decompressive craniectomy. The patient had an underlying arachnoid cyst, likely due to a severe traumatic brain injury. Concealed by hair, contour elevation was observed, with brain tissue bulging through the defect.

The implant was fixed to the native bone using bone sutures, without addressing the arachnoid cyst.

At 6 months postoperatively, the skull maintained symmetry, but the implant was elevated above the skull contour with visible “elastic segment patterning.” It remained firm without mobility, and no osteogenesis was observed. Chronic abrasions developed along the implant periphery, causing recurrent erosions requiring antiseptic care.

At 12 months postoperatively, CT imaging showed 0.3- to 0.4-cm gaps between the implant and bone edges, related to skull growth. Sparse ossification was noted along inner surface margins. The implant showed a reduced density, indicating biodegradation without robust osteogenesis.

At 29 months postoperatively, CT imaging showed unchanged arachnoid cyst size. The implant showed significant deformation, with poor bone margin adherence and elevation above the cranial contour. The implant density ranged from 60 to 140 HU, confirming lysis without bone formation (Fig. 3).

FIG. 3.

Patient 3. Implant lysis. Observation period: 29 months. A:Three-dimensional model 6 months postoperatively. B: Three-dimensional model 6 months after surgery showing visible skull asymmetry. C: Three-dimensional model 12 months after surgery. D: Three-dimensional model 12 months after surgery showing further structural changes. E:Clinical observation: implant softening and lysis confirmed on palpation; sponge-like texture noted. F: CT scan showing pronounced loosening of the implant structure.

Given the implant degradation and lack of osteointegration, removal of the CyberBone plate and secondary cranioplasty using titanium was recommended.

Patient 4

A 24-year-old man presented with a posttraumatic frontal bone defect measuring 8 × 6 cm from a previous neurosurgical treatment.

For the adult patient, an implant was designed without growth zones or elastic zones. It was dense with inherent porosity and perforated areas to allow osteoblast infiltration, expected to promote osteogenesis. The implant was placed into the defect and secured using bone sutures.

Nine months postoperatively, the patient returned with swelling and erythema at the implant site. On palpation, the plate was elevated 0.5 cm above the adjacent bone margins. No ossification zones were observed on CT imaging. The implant density ranged from 20 to 130 HU, confirming continued lysis without bone formation (Fig. 4).

FIG. 4.

Patient 4. Implant lysis. Observation period: 13 months. A: Three-dimensional model of the skull before surgery. B: Preoperative CT scan of the skull. C: Three-dimensional model 12 months after surgery showing the porous structure of the implant and decreased density. D: CT scan obtained 12 months after surgery, clearly demonstrating reduced density of the implant.

Because of progressive implant displacement and signs of aseptic inflammation, surgical removal was recommended, followed by secondary cranioplasty using a titanium plate. The procedure was scheduled.

Patient 5

A 14-year-old girl was diagnosed with low-grade sarcoma of the right parietal, frontal, and temporal bones. A wide craniectomy was performed, including resection of the affected bones, overlying aponeurosis, and dura mater, followed by duraplasty using an autologous aponeurosis. Given the need for future MRI to monitor oncological status, a nonmetallic implant was preferred.

The oncological condition remained stable. At 3 months postoperatively, the CyberBone implant was placed into the cranial defect and fixed to the native bone using bone sutures. Given prior experience with pediatric implants and the lack of satisfactory osteogenesis on follow-up imaging, a decision was made to increase implant elasticity and enhance porosity. Specially designed edges were incorporated to overlap the adjacent skull and prevent future displacement.

At 4 months postcranioplasty, MRI revealed disease progression with recurrent tumors in the surgical area. Multiple confluent lesions were observed surrounding the implant along the inner and outer surfaces of the frontal, parietal, and temporal bones, with brain edema, consistent with prolongatio morbi. The patient was considered for palliative care, and further surgery was not indicated. Supportive therapy, including antiedema and systemic treatment, was initiated. The last CT study showed lysis of the plate with a density ranging from 30 to 110 HU (Fig. 5).

FIG. 5.

Patient 5. Implant lysis. Observation period: 12 months. A:Three-dimensional model of the skull before implantation. B: CT scan obtained 12 months after surgery, showing marked reduction in implant density. C:Three-dimensional model illustrating soft implant structure in contrast to surrounding bone. D: Three-dimensional model showing osteogenic foci within the implant. Soft segments of the cranial plate were removed.

Patient 6

An adult female patient presented with a left M1–M2 saccular aneurysm after surgical clipping. She reported pain and discharge from the previous left temporal craniotomy site. Acute osteomyelitis of the left frontal and temporal bones with epidural abscess formation was diagnosed (Staphylococcus warneri). Surgical management included removal of the infected bone flap from the left frontotemporal region, debridement and drainage of the epidural abscess, and excision of the cutaneous fistula.

Five months later, the patient underwent a secondary cranioplasty. A CyberBone implant was placed edge-to-edge into the cranial defect using bone sutures.

At 2 months postoperatively, she returned with wound dehiscence and local infection. The infected implant was removed. Microbiological analysis revealed the sparse growth of Escherichia coli. The wound healed completely, and the patient was discharged in a satisfactory condition. The patient declined further reconstruction, although secondary cranioplasty using a titanium implant was advised.

Informed Consent

The necessary informed consent was obtained in this study.

Discussion

Observations

Cranial reconstruction remains a challenging endeavor, especially in pediatric populations, in whom skull growth introduces additional biomechanical and biological variables. In our series of 6 patients (4 pediatric and 2 adult cases), we assessed the clinical utility of the biodegradable osteogenic CyberBone implant for cranial defect reconstruction. Although the theoretical benefits of such implants are significant, including osteointegration, bioresorption, and the capacity to adapt to cranial growth, our results are largely disappointing.

One of the primary motivations for using bioresorbable osteogenic implants is to overcome the limitations of rigid materials such as titanium in growing skulls. Several studies have confirmed that rigid implants may impair skull development and lead to cranial deformities or require repeated surgeries in children.^2,5,12,14 In contrast, materials designed to degrade and integrate with the native bone theoretically allow physiological skull expansion while being gradually replaced by new bone.¹

The management of growing skull fractures (GSFs) remains another surgical challenge that relies on traditional approaches. The primary goals are excision of damaged tissue, watertight dural closure, and repair of the cranial defect, but in this article we focus only on problematic bone defects.^17–19 Cranioplasty is often performed in the same sitting as duraplasty, particularly for defects larger than 3 cm, whereas in smaller defects, especially in children younger than 5 years, reconstruction may be deferred, relying on the osteogenic potential of the dura.^20–22

When bone reconstruction is required, split calvarial grafts remain the preferred option, although in very young children, the calvarium may be too thin to be harvested safely.²² In such cases, dural repair alone may be sufficient. Various alloplastic materials, including methylmethacrylate or wire mesh, have been used, and autologous bone grafts are still considered the standard of care whenever feasible, as they provide reliable coverage and avoid the complications associated with foreign materials.^{18,19,23–25}

Timing of cranial defect closure remains key to the outcome and guides the choice between bioabsorbable and traditional materials. In elective procedures without cerebral edema, immediate cranioplasty with autologous bone after primary intervention is preferred. In cases with a high risk of brain swelling or when radiotherapy is planned, preservation of native bone in a cryobank offers safe delayed reconstruction. This approach is consistent with data from penetrating and nonpenetrating brain injuries, in which early aggressive debridement is emphasized, and delayed cranioplasty, often beyond 1 year, is recommended to minimize secondary brain injury.²⁶

Early recognition and timely repair are particularly important in the context of GSFs. Velho et al. reported favorable outcomes in 36 pediatric patients, with duraplasty alone sufficient in most cases and combined cranioplasty required in others using materials such as autologous bone, titanium mesh, or osteomesh.²⁰ Similarly, Liu et al. demonstrated that early intervention in GSF, within the first 2 months of progressive fracture enlargement, was associated with better results, avoiding scarring and facilitating dural dissection.¹⁷ These findings underscore that systemic factors, such as patient age, risk of cerebral edema, oncological status, and the presence of dural tears, must be considered when selecting both the timing and material for cranial reconstruction.

We hypothesized that CyberBone biodegradable plates might offer a novel solution for GSF repair. Such implants were expected to overcome the drawbacks of rigid synthetic materials like titanium plates, while replicating advantages of split calvarial grafts, such as biological integration and adaptability, without graft harvesting morbidity and with potential to reduce operative time. However, in our experience, CyberBone implants failed to meet expectations in terms of mechanical integrity, osteogenic activity, and cosmetic results.

All 6 patients in our study developed complications of varying severity, including implant deformation, fracture, inadequate integration, and inflammatory reactions. These outcomes echo concerns raised in previous case reports regarding the vulnerability of bioresorbable implants to trauma or insufficient bone substitution.¹¹ For instance, Igarashi et al. documented bioabsorbable cranial plate failure following trauma, questioning the long-term durability of such materials, despite initial claims of equivalence to titanium.¹¹

Radiologically, we observed a progressive decrease in the implant density (measured in HU), suggesting active resorption of the material without concurrent osteogenesis. In most cases, ossification was restricted to the peripheral zones or sites of fixation, but no case demonstrated complete bone substitution or consistent osteoinductive performance. This contradicts the preclinical assumptions that such materials would stimulate osteogenesis through mechanical strain on the dura and their intrinsic bioactivity.^9,10

A similar phenomenon was observed in recent experimental histological studies of poly(l-lactide--d,l-lactide) implants with 10% hydroxyapatite content. Despite successful fibroblast adhesion on the inner surface, no collagen fibers were found around the cell colonies, suggesting limited extracellular matrix formation. Moreover, the outer implant surface showed areas densely populated by dead immune cells, indicating a cytotoxic or inflammatory response likely caused by the implant material itself.²⁷ Furthermore, the gap formation between the implant and host bone in pediatric patients points to an insufficient ability of the material to “grow” with the expanding skull. This phenomenon has been previously described as a critical drawback of nondynamic cranioplasty implants in children.^5,14 In summary, while CyberBone presents a promising concept as a custom, degradable, osteogenic implant, the clinical results in our cohort suggest significant limitations.

The authors hypothesize that these implants failed to deliver the advantages claimed by the manufacturer due to design and material limitations. Cranial growth outpaced the implant’s ability to “expand” or adapt, causing plate fracture under rigid fixation and marginal gaps at bone-implant interfaces with elastic sutures. Increased elasticity compromised mechanical strength, while rigidity prevented physiological adaptation and vascularization. The observed ossification was minimal and outweighed by progressive resorption, indicating that the material was osteoconductive rather than osteoinductive. Moreover, CT studies showed declining density and plate swelling, suggesting an inflammatory reaction possibly triggered by implant components. The combination of technological shortcomings and lack of rigorous preclinical and clinical evaluation contributed to negative outcomes across all cases.

According to Regulation (EU) 2017/745 (MDR), custom-made medical devices, including patient-specific implants, are exempt from the requirement to undergo clinical investigations prior to CE marking (Article 52[8]). While such exemption facilitates access to individualized solutions, it also raises concerns regarding the insufficient premarket evaluation of safety and long-term performance. This regulatory gap underscores the need for stricter oversight and evidence-based validation even for custom-made implants.

Until further technological and compositional improvements are achieved, such implants should be used cautiously and not as a standard substitute for autologous bone or established synthetic options.

Lessons

Despite significant theoretical advantages, including biodegradability, osteoconductivity, and the potential to adapt to cranial growth, the CyberBone implant did not meet the clinical expectations in our case series of pediatric and adult patients undergoing cranioplasty. None of the 6 patients achieved satisfactory outcomes in terms of mechanical strength, cosmetic results, or complete osteointegration. All patients experienced complications of varying severity, including implant deformation, fracture, insufficient ossification, and inflammatory signs.

While the concept of a bioresorbable, osteogenic implant that can adapt to pediatric cranial growth is attractive, our findings suggest that the current version of the CyberBone implant is not reliable for clinical use. The observed complications and lack of consistent integration raise serious concerns about its safety and effectiveness.

Currently, the use of such implants in humans remains highly questionable and should not be considered a viable alternative to established materials. Further in-depth preclinical and clinical research is required to evaluate their biomechanical properties, biodegradation behavior, and biological responses in various age groups before any broader implementation can be justified.

Acknowledgments

During the preparation of this work, we used ChatGPT-5 to translate some parts of the text from Ukrainian to English and Paperpal to improve readability and language. After using these tools, we reviewed and edited the content as needed and take full responsibility for the content of the publication.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Ishchenko, Perekopaiko. Acquisition of data: all authors. Analysis and interpretation of data: all authors. Drafting the article: Ishchenko, Perekopaiko, Dudenko. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Ishchenko. Statistical analysis: Ishchenko, Perekopaiko, Boldyrev. Administrative/technical/material support: Ishchenko, Perekopaiko. Study supervision: Ishchenko, Perekopaiko.

Correspondence

Dmytro Ishchenko: National Specialized Children’s Hospital Ohmatdyt, Kyiv, Ukraine. ishchenko.dmitriy@gmail.com.