ABM/P-15-enhanced bone graft in oncologic cervical spine reconstruction: two case reports and narrative discussion

Introduction

Bone grafting has a long history in skeletal and spinal reconstruction (1,2). In spinal oncology, tumor-related bone destruction and mechanical instability are important considerations in treatment planning (3,4). Available grafting approaches include autograft, allograft, synthetic substitutes, and biologic adjuncts. Allograft use requires attention to tissue banking and disease-transmission risk (5,6). Hydroxyapatite and recombinant human bone morphogenetic protein-2 have been investigated in tibial fracture settings (7,8), but these studies do not directly establish their performance in oncologic cervical reconstruction.

Anorganic bone mineral/P-15 (ABM/P-15) bone grafts combine anorganic bone mineral with a synthetic 15-amino-acid peptide sequence designed to mimic the cell-binding domain of type I collagen. The mineral phase functions as an osteoconductive scaffold, while the peptide surface is intended to support osteoblast adhesion and matrix formation (9-12). This mechanism differs from bone morphogenetic proteins (BMPs), which are osteoinductive cytokines intended to drive bone formation through growth-factor signaling. Clinical evidence for ABM/P-15 comes primarily from degenerative cervical and lumbar spine populations; oncology-specific evidence remains limited and indirect (13-18).

We present two cases of complex cervical spine reconstruction in oncologic patients where ABM/P-15 was used as one component of a broader reconstructive strategy. This manuscript is framed as two clinical case reports with a focused narrative literature discussion, and is not intended to be a systematic review or PRISMA-structured evidence synthesis.

For this report, successful healing/fusion was defined operationally as continuous bridging trabecular bone or host-graft continuity on follow-up computed tomography (CT) across the intended fusion surfaces, accompanied by maintained segmental mechanical stability and absence of pseudoarthrosis, implant loosening, or hardware failure. This definition was informed by CT-based fusion-assessment concepts including the Glassman grading approach, although that lumbar posterolateral fusion scale was not formally applied to these heterogeneous cervical oncologic reconstructions (19). We present this article in accordance with the CARE reporting checklist (available at https://jss.amegroups.com/article/view/10.21037/jss-2026-0119/rc).

Case presentation

For both cases, the authors confirmed that the biologic adjunct was a Cerapedics ABM/P-15 product, described as i-FACTOR/PearlMatrix^TM, with PearlMatrix representing the same/rebranded product name. A 10-cc product volume was used in each case. The supplied documentation describes porcine-derived anorganic bone mineral particles coated with P-15 peptide and carried in bovine type I collagen. The product was hydrated with sterile saline or autogenous bone marrow aspirate, placed at the graft site, used with autograft or autogenous bone marrow aspirate, did not directly contact tumor-bed margins, and was not subject to institutional or cost restriction.

Radiographic fusion was assessed retrospectively on CT obtained at 6 and 12 months. Two evaluators reviewed the imaging and agreed regarding fusion status. Fusion was described when bridging trabecular bone or host-graft continuity was seen across the intended fusion surfaces, with maintained alignment and no radiographic pseudoarthrosis, implant loosening, or hardware failure. Dynamic radiographs were not used for the formal fusion assessment, the Glassman or another validated grading scale was not formally applied, and no formal interobserver-agreement statistic was calculated. Table S1 compares commonly used graft and biologic options in spinal fusion, including their mechanisms, advantages, limitations, and relevance to oncologic reconstruction.

Case 1: metastatic solitary fibrous tumor with upper cervical nonunion and pathologic fracture

A young adult male with metastatic solitary fibrous tumor had a long oncologic and surgical history. Earlier treatment included intracranial surgery in 2013, cervical decompression/fusion and adjuvant neck radiotherapy in 2019, axillary lymph-node dissection for metastatic solitary fibrous tumor in 2020, and revision cervical surgery for failed hardware in 2021. In 2022, imaging again raised concern for recurrence, and systemic therapy consultation was arranged.

He presented in July 2023 with severe cervical pain, inability to maintain his head upright, and marked functional limitation. Examination demonstrated upper cervical tenderness and clinical instability without motor or sensory deficit. CT showed a lytic lesion involving the left C1 lamina/transverse process with a pathologic fracture and C1–C2 nonunion; magnetic resonance imaging (MRI) showed adjacent soft-tissue disease with foraminal extension and mild thecal sac compression. After multidisciplinary review, revision stabilization was recommended.

On July 14, 2023, he underwent removal of prior implants and revision occiput-to-T2 posterior instrumentation. Local autograft from spinous processes was placed along the prepared posterolateral fusion beds, and the reported Cerapedics ABM/P-15 preparation was used as an adjunct at the fusion surfaces. The response materials state that the product did not contact tumor-bed margins. The patient remained neurologically intact postoperatively and began early physiotherapy.

At follow-up, radiographs at 3 months showed preserved alignment, CT at 6 months demonstrated bilateral bridging bone formation and progressive graft incorporation, and CT/radiographs at approximately 12 months showed continuous trabecular bone across the instrumented segments without pseudoarthrosis, implant loosening, or hardware failure (Figures 1-3). Visual Analog Scale (VAS)/Numeric Rating Scale (NRS) and Neck Disability Index (NDI) scores were not collected. The patient was reported to be neurologically intact, have no mechanical neck pain, and returned to playing basketball after having been unable to sit upright before surgery.

Figure 1 Original author-created treatment timeline for Case 1, metastatic solitary fibrous tumor with upper cervical nonunion and pathologic fracture. ABM, anorganic bone mineral.

Figure 2 CT sagittal image showing C1 screw failure secondary to nonunion. CT, computed tomography.

Figure 3 CT and radiographs showing fusion for Case 1 at approximately 12 months. CT, computed tomography.

Cancer-treatment review showed multiple prior radiation courses, including cranial radiotherapy in 2013, neck radiotherapy in 2019, and thoracic/axillary treatments in 2021. Pazopanib 800 mg orally daily was documented as starting on August 30, 2023, with interruptions from September 29 to October 6, 2023, discontinuation on February 15, 2024, restart on March 6, 2024, later treatment holds and dose modification, and no further systemic treatment recommended after June 19, 2025. No chemotherapy, immunotherapy, bisphosphonate, or denosumab use was reported.

Case 2: recurrent cervical chordoma treated with fibular reconstruction and ABM/P-15

A young adult female had recurrent cervical chordoma after prior surgery and radiotherapy. In June 2019 she underwent posterior C1–C6 surgery followed by an anterior approach with tumor removal. Proton-beam radiotherapy was arranged in Boston in September 2019. In 2022 she developed right-arm numbness and neck symptoms, and subsequent imaging showed progression involving the C2 and C4 foramina with surrounding lymph nodes. After tumor-board review and biopsy planning, en bloc resection was recommended.

In April 2023, she underwent anterior tumor resection, including partial C2–C4 corpectomy, with anterior and posterior stabilization. The previous fibular graft was preserved and reshaped, anterior fixation was provided with plate/screws spanning C4–C7 while preserving the prior C4–C5 plate, and grafting was performed at the intervertebral and host-graft interfaces. Posterior instrumentation included C2 pedicle screws, C3–C6 lateral mass screws, bilateral rods, and a structural fibular allograft strut from C1 to C5, augmented with the reported ABM/P-15 material. The response materials state that the product did not contact tumor-bed margins.

The immediate postoperative course was stable, with improved pain and upper-limb strength, 48 hours of intensive-care monitoring, adequate analgesia, early physiotherapy, and no vascular or infectious complication. Radiographs at 3 months showed maintained hardware position; CT at 6 months showed progressive bridging bone formation at host-graft interfaces; and CT/radiographs at approximately 12 months showed graft integration without pseudoarthrosis or implant failure (Figures 4,5). VAS/NRS and NDI scores were not collected. The patient was reported to be neurologically intact and without mechanical neck pain.

Figure 4 Original author-created treatment timeline for Case 2, recurrent cervical chordoma treated with fibular reconstruction and ABM/P-15. ABM, anorganic bone mineral.

Figure 5 CT sagittal images and radiographs showing fusion for Case 2 at approximately 12 months. CT, computed tomography.

Cancer-treatment review found no systemic therapy recommended for this patient and no chemotherapy, immunotherapy, bisphosphonate, denosumab, kinase inhibitor, or targeted systemic therapy. In April 2023, resection margins were positive. By October 2024, imaging showed a new left-sided cervical lesion concerning for local recurrence; no additional surgery, radiotherapy, or systemic therapy was recommended, and palliative care was pursued. She subsequently developed hydrocephalus requiring ventriculoperitoneal shunting and multiple shunt revisions in January 2025.

All procedures performed in this study were in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by McGill University Health Centre Research Ethics Board (No. MP-37-2022-8371), with annual renewal approved by delegated review for the period June 29, 2026 to June 28, 2027. Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

These cases describe radiographic fusion or graft incorporation after two high-risk cervical oncologic reconstructions in which ABM/P-15 was used as an adjunct. The observations are clinically relevant because both patients had features associated with impaired fusion biology, including prior radiotherapy, recurrent tumor, repeat surgery, and extensive reconstruction. However, they should be interpreted as initial observations rather than evidence of efficacy: both patients underwent multicomponent reconstruction with rigid fixation, autograft and/or fibular graft material, and multidisciplinary perioperative care. The contribution of ABM/P-15 cannot be isolated.

Mechanical stability is also central to successful healing. A biologic adjunct cannot compensate for persistent motion, inadequate load sharing, implant loosening, or failed alignment. In both cases, rigid instrumented stabilization and structural/autogenous grafting were essential elements of the reconstruction, and the perceived role of ABM/P-15 was limited to providing an osteoconductive scaffold with a collagen-mimetic cell-attachment surface in a compromised healing environment. This rationale remains theoretical in oncologic cervical reconstruction and should not be read as proof of an independent graft effect.

The mechanism of ABM/P-15 should also be described precisely and distinguished from BMP-based strategies. The anorganic bone mineral component provides an osteoconductive scaffold. The P-15 peptide is designed to mimic the cell-binding domain of type I collagen and may support osteoblast attachment and matrix production. By contrast, BMPs act through growth-factor signaling and are generally described as osteoinductive in selected approved indications. ABM/P-15 therefore should not be assumed to be osteoinductive in oncologic reconstruction, nor does this two-case experience demonstrate comparative benefit over autograft, allograft, BMPs, or other biologic strategies.

The oncologic context is important. Radiotherapy, local recurrence, systemic therapy, and compromised tissue quality can affect bone healing and survival independently of any graft material. In the solitary fibrous tumor case, pazopanib therapy and multiple radiation courses are potential confounders when interpreting fusion. In the chordoma case, later local progression and hydrocephalus reflected the aggressive oncologic course; this case report cannot determine whether ABM/P-15 had any favorable or unfavorable oncologic effect. Statements about oncologic safety or tumor progression should therefore be limited to descriptive reporting.

The cases are heterogeneous in diagnosis, prior treatment, reconstruction type, systemic therapy exposure, and oncologic course. They should not be pooled as an efficacy series. Instead, they suggest that standardized reporting of biologic implant details, construct stability, fusion criteria, oncologic treatment exposure, and patient-reported outcomes is essential if ABM/P-15 or related graft materials are studied prospectively in spine oncology.

Limitations

This report is limited by its two-case retrospective design, substantial case heterogeneity, lack of a control group, and inability to isolate the effect of ABM/P-15 from fixation, autograft, allograft/fibular graft reconstruction, radiotherapy history, systemic therapy, construct stability, or host biology. Fusion assessment was retrospective rather than prospectively protocolized; it was based on CT imaging at 6 and 12 months, was reviewed by two evaluators who agreed, did not use dynamic radiographs, did not formally apply the Glassman or another validated fusion grading scale, and did not include a formal interobserver-agreement statistic. VAS/NRS, NDI, and prospectively collected functional outcome scores were not available.

Conclusions

Two complex oncologic cervical reconstructions using ABM/P-15 as an adjunct within mechanically stable, multicomponent constructs demonstrated radiographic fusion or host-graft incorporation at approximately 12 months. These cases are descriptive and hypothesis-generating. They do not establish independent graft efficacy, comparative benefit, or oncologic safety, and they support the need for standardized prospective evaluation in oncologic spine reconstruction.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://jss.amegroups.com/article/view/10.21037/jss-2026-0119/rc

Peer Review File: Available at https://jss.amegroups.com/article/view/10.21037/jss-2026-0119/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-2026-0119/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by McGill University Health Centre Research Ethics Board (No. MP-37-2022-8371), with annual renewal approved by delegated review for the period June 29, 2026 to June 28, 2027. Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Ollier L. Traite experimental et clinique de la regeneration des os. Paris: Masson; 1867.
2. Albee FH. Transplantation of a portion of the tibia into the spine for Pott's disease. JAMA 1911;57:885-6.
3. Fisher CG, DiPaola CP, Ryken TC, et al. A novel classification system for spinal instability in neoplastic disease: an evidence-based approach and expert consensus from the Spine Oncology Study Group. Spine (Phila Pa 1976) 2010;35:E1221-9. [Crossref] [PubMed]
4. Coleman RE. Metastatic bone disease: clinical features, pathophysiology and treatment strategies. Cancer Treat Rev 2001;27:165-76. [Crossref] [PubMed]
5. Mroz TE, Joyce MJ, Steinmetz MP, et al. Musculoskeletal allograft risks and recalls in the United States. J Am Acad Orthop Surg 2008;16:559-65. [Crossref] [PubMed]
6. Friedlaender GE. Bone-banking. J Bone Joint Surg Am 1982;64:307-11. [PubMed]
7. Bucholz RW, Carlton A, Holmes R. Interporous hydroxyapatite as a bone graft substitute in tibial plateau fractures. Clin Orthop Relat Res 1989;53-62. [PubMed]
8. Govender S, Csimma C, Genant HK, et al. Recombinant human bone morphogenetic protein-2 for treatment of open tibial fractures: a prospective, controlled, randomized study of four hundred and fifty patients. J Bone Joint Surg Am 2002;84:2123-34. [Crossref] [PubMed]
9. Yang XB, Bhatnagar RS, Li S, et al. Biomimetic collagen scaffolds for human bone cell growth and differentiation. Tissue Eng 2004;10:1148-59. [Crossref] [PubMed]
10. Qian JJ, Bhatnagar RS. Enhanced cell attachment to anorganic bone mineral in the presence of a synthetic peptide related to collagen. J Biomed Mater Res 1996;31:545-54. [Crossref] [PubMed]
11. Bhatnagar RS, Qian JJ, Wedrychowska A, et al. Design of biomimetic habitats for tissue engineering with P-15, a synthetic peptide analogue of collagen. Tissue Eng 1999;5:53-65. [Crossref] [PubMed]
12. Nguyen H, Qian JJ, Bhatnagar RS, et al. Enhanced cell attachment and osteoblastic activity by P-15 peptide-coated matrix in hydrogels. Biochem Biophys Res Commun 2003;311:179-86. [Crossref] [PubMed]
13. Arnold PM, Sasso RC, Janssen ME, et al. Efficacy of i-Factor Bone Graft versus Autograft in Anterior Cervical Discectomy and Fusion: Results of the Prospective, Randomized, Single-blinded Food and Drug Administration Investigational Device Exemption Study. Spine (Phila Pa 1976) 2016;41:1075-83. [Crossref] [PubMed]
14. Arnold PM, Sasso RC, Janssen ME, et al. Neurosurgery. 2018;83:377-84.
15. Arnold PM, Vaccaro AR, Sasso RC, et al. Six-Year Follow-up of a Randomized Controlled Trial of i-FACTOR Peptide-Enhanced Bone Graft Versus Local Autograft in Single-Level Anterior Cervical Discectomy and Fusion. Neurosurgery 2023;92:725-33. [Crossref] [PubMed]
16. Spanninga BJ, Hoelen TA, Johnson S, et al. Clinical efficacy and safety of P-15 peptide enhanced bone graft substitute in surgical bone regenerative procedures in adult maxillofacial, spine, and trauma patients : a systematic literature review. Bone Joint Res 2025;14:77-92. [Crossref] [PubMed]
17. Harrop JS, Steinmetz MP, O'Toole JE, et al. P-15 Peptide Enhanced Bone Graft Improves Time to Fusion in Transforaminal Lumbar Interbody Fusion: A Randomized, Controlled, Investigational Device Exemption Study. Spine (Phila Pa 1976) 2026;51:229-37. [Crossref] [PubMed]
18. Harrop JS, O'Toole JE, Steinmetz MP, et al. P-15 Peptide Enhanced Bone Graft in Transforaminal Lumbar Interbody Fusion: A Randomized, Controlled, Investigational Device Exemption Study Demonstrating Improved Composite Clinical Success. Spine (Phila Pa 1976) 2026;51:238-47. [Crossref] [PubMed]
19. Glassman SD, Dimar JR, Carreon LY, et al. Initial fusion rates with recombinant human bone morphogenetic protein-2/compression resistant matrix and a hydroxyapatite and tricalcium phosphate/collagen carrier in posterolateral spinal fusion. Spine (Phila Pa 1976) 2005;30:1694-8. [Crossref] [PubMed]