Application of Biocomposite Hydrogel With Developed Trabecular Cage in Lumbar Interbody Fusion: A Clinical Case Report

Abstract

Background:

Lumbar interbody fusion (LIF) is a widely used surgical technique for treating degenerative spinal conditions. However, challenges such as pseudarthrosis and implant migration remain significant concerns. This case report presents the use of a novel trabecular titanium cage combined with a biocomposite hydrogel containing stromal-vascular fraction and BMP-2 to enhance osseointegration and accelerate bone fusion.

Case presentation:

A 61-year-old female patient with severe chronic lumbar pain, functional impairment, and grade II anterolisthesis of L4 underwent lumbar interbody fusion. A custom-designed trabecular titanium cage was implanted, featuring an optimized porous structure for enhanced fixation and bone ingrowth. To further promote bone regeneration, a biocomposite hydrogel synthesized from adipose-derived stromal-vascular fraction and BMP-2 was applied. Postoperative assessment demonstrated significant pain reduction, improved functional activity, and early bone fusion formation. Radiological imaging confirmed stable implant positioning, progressive trabecularization, and successful osseointegration. No complications, such as implant migration or material loosening, were observed.

Conclusions:

This case highlights the potential benefits of combining advanced implant design with bioactive materials in spinal fusion surgery. The approach resulted in early and stable bone integration, reduced pain, and improved functional recovery. Further studies with larger patient cohorts and extended follow-up periods are needed to validate these findings and assess long-term outcomes.

Introduction

Lumbar interbody fusion (LIF) is a well-established technique used in spine surgery. The main goal of the procedure is to create a biomechanically strong interbody fusion, which is achieved using various implants and surgical approaches. ¹ Interbody cage used to restore interbody height, bone graft fixation, and restore biomechanical stability of the anterior column have been shown to be effective in achieving successful fusion. These grafts are associated with decreased postoperative pain, reduced hospitalization, lower complication rates and improved fusion rates compared to methods based on bone graft alone. ²

However, despite all the advantages of the method, there are also certain disadvantages, including pseudarthrosis, which is one of the common problems arising from insufficient vertebral fusion. ³ In this regard, the use of biological agents to improve reparative regeneration of bone tissue is currently relevant, showing results ranging from 63% to 100% described by Stephan et al. ⁴

Several classes of biological agents are currently available or under investigation in clinical and preclinical studies, among which autologous bone grafts—primarily harvested from the iliac crest—remain the gold standard due to their osteogenic, osteoinductive, and osteoconductive properties, despite limitations related to donor site morbidity and availability. ⁴ Allografts and demineralized bone matrix (DBM) offer osteoconductive scaffolding but lack consistent osteoinductive capacity and carry risks of immunogenicity or disease transmission. ⁵ Bone morphogenetic proteins (BMPs), especially recombinant human BMP-2 (rhBMP-2), have demonstrated significant potential in enhancing spinal fusion, and in comparison with autograft showed better fusion results. ⁶ Mesenchymal stem cells (MSCs), particularly those derived from adipose tissue or bone marrow, show promise due to their ability to differentiate into osteoblasts and modulate the local immune response. An analysis including 15 stem cell studies showed that the rate of vertebral fusion ranged from 60% to 100%, with a mean of 87.1%. ⁷ Stromal-vascular fraction (SVF), a heterogeneous cell population derived from adipose tissue, contains mesenchymal stem cells (MSCs), endothelial progenitor cells, and immune cells, which may synergistically promote bone healing. A clinical study by Choi et al ⁸ demonstrated the relative safety, technical feasibility, and potential effectiveness of this approach. Biocomposite hydrogels incorporating these biological agents (eg, BMP-2, SVF) serve as carriers that can localize and control the release of bioactive substances, improve graft handling, and enhance cellular viability and osteointegration. ⁹

The aim of this publication is to present a clinical case demonstrating the use of a biocomposite hydrogel and our self-developed trabecular cage in LIF.

Case Report

Patient Presentation

Patient A: a 61-year-old individual with a body mass index (BMI) of 33.6 kg/m² (height 161 cm, weight 87 kg), was admitted to the clinic with complaints of severe lower back pain radiating to the right lower limb, which worsened with movement. The pain had been present for 3 years. Initially, pharmacological therapy and chiropractic treatment provided partial relief, but over time, the pain progressively worsened and the treatment became ineffective. The patient was also diagnosed with bilateral osteoarthritis of the knee joints (grade II-III) and arterial hypertension.

Ethical Considerations

The study was conducted in accordance with the ethical principles set out in the Declaration of Helsinki (1964) and its subsequent amendments. The study protocol was reviewed and approved by the local ethics committee (protocol number 4, date: February 4, 2021), ensuring compliance with international standards for clinical research. Written informed consent was obtained from the patient before inclusion in the study. The patient was informed about the purpose of the study, the nature of the procedures performed, potential risks, and her right to withdraw from the study at any stage without any impact on her current medical care. The patient was insured for the entire period of participation in the study in accordance with the established requirements.

Radiological Diagnostics Before Surgery

X-Ray Analysis

Standard radiographs of the lumbosacral spine, and with functional loading, showed displacement of the L4 vertebral body by 1.5 cm anteriorly, as well as marked narrowing of the intervertebral gap between the L4 and L5 vertebrae, indicating anterolisthesis of the L4 vertebrae of grade II, according to the Meyerding classification (Figures 1 and 2). ¹⁰

Figure 1.

Preoperative radiographs of the lumbar spine.

Figure 2.

Preoperative radiographs of the lumbar spine with functional tests.

MRI

MRI images showed posterior bulging of the intervertebral disks at the levels of L4-L5 and L5-S1, with spinal canal stenosis. Hyperintense signal on T2-weighted images was recorded in the region of the closing plates of the L4-L5-S1 vertebrae, indicating inflammatory edema of bone structures, corresponding to Modic et al. 1 changes (Figure 3). ¹¹

Figure 3.

MRI of the lumbar spine.

Surgical Procedure

The indications for surgery were the presence of severe pain, ineffectiveness of conservative treatment, signs of vertebral instability, and stenosis of the spinal canal according to radiography and MRI.

Stage I

After the patient was admitted to the hospital, adipose tissue was harvested by lipoaspiration using the Zuk et al technique (Figure 4). ¹²

Figure 4.

Lipoaspiration of a patient.

The lipoaspirate obtained during the procedure, under strict aseptic and antiseptic conditions and with adherence to the cold chain, was transported to the laboratory for the synthesis of the biocomposite hydrogel.^9,13

Stage II

Surgery

The patient underwent surgery involving the removal of an intervertebral hernia, the installation of a trabecular titanium cage at the L4-L5 level—where the cage cavity, filled with autograft bone, was impregnated with a biocomposite hydrogel—followed by transpedicular fixation of the vertebrae.

In this operation, we used a trabecular cage made of titanium alloy that was developed by our team. The distinctive features of this device, compared to its close analogs, include a more rounded end of the structure, allowing for easier implant placement, and teeth oriented at a 45° angle (Figure 5), ensuring secure fixation between the vertebrae and preventing potential migration. The presence of a large central hole and the cellular structure facilitate rapid bone tissue regeneration, while the elasticity of the mesh-like design helps prevent prolapse and the development of adjacent segment syndrome.

Figure 5.

Three-dimensional model of the developed trabecular cage.

No intraoperative complications, such as damage to blood vessels, the dura mater, or nerve roots, were detected.

In the early postoperative period, the patient noted pain reduction, except for pain in the surgical wound and was activated on the first day and discharged on the 10th day after surgery, after suture removal. The postoperative wound healed with primary tension, without signs of inflammation.

Postoperative Questionnaire Results

The dynamics of the patient’s clinical parameters in the postoperative period is presented in Table 1, where positive dynamics of VAS, ODI, and SF-36 results was noted.

Table 1.

The Dynamics of the Patient’s Clinical Parameters in the Postoperative Period Is Presented in Table 1, Where Positive Dynamics of VAS, ODI, and SF-36 Results Was Noted.

Period	VAS	ODI	SF-36 (key indicators)
Before surgery	9/10	62% (extremely severe)	Physical functioning—10%, pain intensity—10%
10 d	4/10	30% (moderate impairment)	Slight improvement, but limitations remain
3 mo	3/10	22% (moderate impairment)	Physical functioning—60%, pain intensity—67%
8 mo	3/10	14% (minimal impairment)	Pain intensity—90%, role functioning—100%, social functioning—87%

Radiological Diagnostics After Surgery

Immediate Postoperative Period (3 Months)

The patient underwent control radiography of the lumbosacral spine (Figure 6), which showed the correct position of the metal structure.

Figure 6.

Control radiography of the lumbosacral spine 3 months after surgical treatment. Computed tomography analysis.

At the comparative analysis of computed tomography (CT)scans, in frontal and sagittal projections of multiplanar reconstruction the position of the cage-system is satisfactory. There is some local subsidence of the implant in the area of the inferior surface of the L4 vertebra. However, in the sagittal projection the formation of additional bone structure in the intervertebral space is determined mainly on the anterior-external surface of the implant.

Bone callus formation with minimal areas of lucency shows Bridwell KH-grade 2 ¹⁴ is noted in the central zone of the cage (Figure 8).

There is irregular narrowing of the articular gap with marginal overgrowths and osteosclerotic changes along the posterior part of the closure plates of the L4-L5 vertebrae, behind the cage (Figure 9).

Quantitative indicators of the density of the formed bone callus around and inside the cage are presented in Table 2.

Table 2.

Quantitative assessment of the density of the formed bone callus according to CT data in Hounsfield units.

Area of bone callus formation (in relation to the implant)	Quantitative indicator of bone callus density in Hounsfield units (HU)—ROI D ⩾3.0 mm	Image scheme
Anterior surface	371-817 HU	Figure 7
Central area (inner surface) of the cage	392-730 HU	Figure 8
Posterior surface	408-533 HU	Figure 9

Figure 7.

Sagittal projection of the lumbar spine at the level of L4-L5, with CT images of the formation of an additional bone structure in front of the implant (indicated by the red arrow).

Figure 8.

Frontal (right) and sagittal (left) CT data projections, with signs of dense bone callus formation) predominantly from underlying structures, with minimal areas of lucency by Bridwell KH-2 stage (indicated by red arrow).

Figure 9.

Sagittal view, behind the implant there is narrowing of the articular gap due to marginal growths with osteosclerotic changes of the closure plates at the level of L4-L5 (indicated by a red arrow).

No pronounced hypodense areas (lucencies) were observed at the edges of the interbody device and around the screws, ruling out material loosening and movement due to fixation instability. ¹⁵

Further follow-up involves CT follow-up of the lumbar spine after 12 months to confirm mature trabecularization with obvious bony bridges between the vertebral bodies. A repeat CT scan after 24 months is only performed if there is no solid spondylosis after 12 months, any evidence of lucency or cystic changes at the edges of the device or lucency lines through the fusion mass is an indicator of non-union or failed fusion. ¹⁶

Discussion

Titanium and polyetheretherketone (PEEK) are the most common materials for intervertebral cages used in LIF. Titanium is widely used in medicine due to its high biocompatibility and excellent corrosion resistance. However, due to their significantly higher modulus of elasticity compared to bone tissue, titanium cages can cause stress shielding effects and an increased risk of subsidence. ¹⁷

To reduce these risks, PEEK implants have been used in clinical practice. Their modulus of elasticity is closer to the characteristics of bone tissue, which contributes to the reduction of stress shielding, reduces the probability of subsidence, and increases the efficiency of fusion. ¹⁸ In addition, PEEK is radiopaque, which facilitates the control of bone fusion formation by radiography, unlike radiopaque titanium. The high inertness of the material also reduces the risk of cell adhesion and infection, but this same feature also hinders the osseointegration of PEEK implants, which may limit their long-term efficacy. ¹⁸ From this point of view, trabecular titanium constructs, whose structure is similar to cancellous bone, may provide even more favorable conditions for bone growth and integration. This is confirmed by the proliferation and differentiation of osteoblasts in vitro, as well as by the ingrowth of bone tissue into cancellous and cortical bone in vivo. ¹⁹ In addition, a metaanalysis by Massaad et al including 1094 patients from 11 studies revealed significant advantages of titanium constructs compared to PEEK cages. ²⁰ In the work conducted by Tang et al a 50-year-old patient with signs of instability at the L4-L5 level was fitted with a PEEK cage, with a description of bone block formation by CT scan only 1 year later. ²¹

Methods of pseudarthrosis prevention have become one of the most studied and funded areas in modern spine surgery. ⁴ Traditionally, the “gold standard” of bone grafting has been considered to be the use of autologous graft obtained from a donor or surgical site. Alternatives include allografts, synthetic materials and growth factors such as recombinant human bone morphogenetic protein (rhBMP)−2.

With the development of regenerative medicine and technology, mesenchymal stem cells (MSCs) are receiving increasing attention as a promising way to accelerate bone fusion and reduce the risk of complications. ²²

The technology of using a biocomposite hydrogel produced according to the previously described protocol and containing stromal-vascular fraction and BMP-2, jointly developed and implemented by the Biotechnology Center and our clinic, made it possible to enhance the useful properties of the titanium construct.^9,23 As a result, clinical results were improved and bone fusion formation was achieved earlier.

Limitations

This study has several limitations. Firstly, it is based on a single clinical case, which restricts the ability to draw broad generalizations. Although the results indicate pain reduction, functional improvement, and bone fusion formation, the absence of a statistically significant sample limits the validity of the findings.

Secondly, the study lacks a control group for direct comparison. Without a randomized controlled trial (RCT) or comparative cohort analysis, it is difficult to determine whether the observed improvements are solely attributable to the trabecular titanium cage combined with a biocomposite hydrogel or whether similar outcomes could have been achieved using conventional methods.

Additionally, despite positive radiological evidence of successful osseointegration, a longer follow-up period is required to assess fusion stability and potential complications such as adjacent segment syndrome or implant failure.

Conclusion

This clinical case demonstrates the successful use of a trabecular titanium cage combined with a biocomposite hydrogel containing stromal-vascular fraction and BMP-2 in LIF. The method resulted in significant clinical improvement, including pain reduction, increased functional activity, and enhanced quality of life.

Radiological data confirm early bone fusion formation with minimal lucency and active bone regeneration. The trabecular structure of the cage ensured stable fixation, facilitated osseointegration, and minimized the risk of implant migration.

Despite these promising results, further studies with larger patient cohorts and longer follow-up periods are necessary to validate the efficacy of this approach. We are currently conducting a study with a larger sample size and extended follow-up to address these limitations and further evaluate the benefits of trabecular titanium implants in combination with bioactive materials for LIF.