A histological examination of spinal reconstruction using a frozen bone autograft

Development of a novel regenerative therapy for malignant bone tumors using an autograft containing tumor inactivated by high hydrostatic pressurization (HHP)

Surgical resection of malignant bone tumors leads to significant defects in the normal surrounding tissues that should be reconstructed to avoid amputation. Our research aimed to inactivate osteosarcoma (OS)-affected bone to obtain autologous bone grafts for bone defect reconstruction using a novel therapy called high hydrostatic pressurization (HHP) therapy. The key points are complete tumor death and preservation of the non-denatured native extracellular matrix (ECM) and bone tissue by HHP. Previously, we found that HHP at 200 MPa for 10 min can completely inactivate cells in normal skin and skin tumors, including malignant melanoma and squamous cell carcinoma while maintaining their original biochemical properties and biological components. Based on our previous research, this study used HHP at 200 MPa for 10 min to eradicate OS. We prepared an OS cell line (LM8), pressurized it at 200 MPa for 10 min, and confirmed its inactivation through morphological observation, WST-8 assay, and live/dead assay. We then injected OS cells with or without HHP into the bone marrow of the murine tibia, after which we implanted tumor tissues with or without HHP into the anterior surface of the tibia. After HHP, OS cells did not proliferate and were assessed using a live/dead assay. The pressurized cells and tumors did not grow after implantation. The pressurized bone was well prepared as tumor-free autologous bone tissues, resulting in the complete eradication of OS. This straightforward and short-pressing treatment was proven to process the tumor-affected bone to make a transplantable and tumor-free autologous bone substitute.

Characteristics and risk factors of instrumentation failure following total en bloc spondylectomy

AIMS

The aim of this study was to investigate the incidence and characteristics of instrumentation failure (IF) after total en bloc spondylectomy (TES), and to analyze risk factors for IF.

METHODS

The medical records from 136 patients (65 male, 71 female) with a mean age of 52.7 years (14 to 80) who underwent TES were retrospectively reviewed. The mean follow-up period was 101 months (36 to 232). Analyzed factors included incidence of IF, age, sex, BMI, history of chemotherapy or radiotherapy, tumour histology (primary or metastasis; benign or malignant), surgical approach (posterior or combined), tumour location (thoracic or lumbar; junctional or non-junctional), number of resected vertebrae (single or multilevel), anterior resection line (disc-to-disc or intravertebra), type of bone graft (autograft or frozen autograft), cage subsidence (CS), and local alignment (LA). A survival analysis of the instrumentation was performed, and relationships between IF and other factors were investigated using the Cox regression model.

RESULTS

A total of 44 patients (32.4%) developed IF at a median of 31 months (interquartile range 23 to 74) following TES. Most IFs were rod fractures preceded by a mean CS of 6.1 mm (2 to 18) and LA kyphotic enhancement of 10.8° (-1 to 36). IF-free survival rates were 75.8% at five years and 56.9% at ten years. The interval from TES to IF peaked at two to three years postoperatively and continued to occur over a period of time thereafter; the early IF-developing group had greater CS at one month postoperatively (CS1M) and more lumbar TES. CS1M ≥ 3 mm and sole use of frozen autografts were identified as independent risk factors for IF.

CONCLUSION

IF is a common complication following TES. We have demonstrated that robust spinal reconstruction preventing CS, and high-quality bone grafting are necessary for successful reconstruction.Cite this article: Bone Joint J 2023;105-B(2):172-179.

A Modified Spinal Reconstruction Method Reduces Instrumentation Failure in Total En Bloc Spondylectomy for Spinal Tumors

Introduction

Long-term spinal stability after total en bloc spondylectomy (TES) is challenging. The aim of this study was to examine whether the new method could reduce the incidence of instrumentation failure (IF).

Methods

We retrospectively compared 116 patients with spinal tumors who underwent TES between 2010 and 2019 and were followed up for >1 year. IF, cage subsidence, and complications were evaluated. Propensity score matching between conventional and new method groups was performed for age, sex, body mass index, preoperative radiotherapy, number of resected vertebrae, number of instrumented vertebrae, tumor level, and follow-up period. There were 25 cases each in the conventional and new method groups. The conventional method used a titanium mesh cage for anterior reconstruction and 5.5-mm-diameter titanium alloy rods for posterior fixation. The new method used a more robust cage for anterior reconstruction, bone grafting was performed around the cage, and 6.0-mm-diameter cobalt chromium rods were used for posterior fixation. We compared the incidence of IF and cage subsidence after TES between the conventional and new method groups.

Results

While 5 out of 25 patients (20.0%) in the conventional method group experienced IF, none from the new method group experienced IF. Three-year implant survival rates were 87.3% in the conventional and 100% in the new method groups. The new method group had a significantly higher implant survival rate (p<0.01). Cage subsidence was observed in 11 of 25 (44/0%) patients in the conventional method and 1 of 25 (4.0%; significantly lower, p<0.05) in the new method group.

Conclusions

The new reconstruction method significantly reduced IF incidence in patients with TES.

Abscopal Effect of Frozen Autograft Reconstruction Combined with an Immune Checkpoint Inhibitor Analyzed Using a Metastatic Bone Tumor Model

We evaluated the abscopal effect of re-implantation of liquid nitrogen-treated tumor-bearing bone grafts and the synergistic effect of anti-PD-1 (programmed death-1) therapy using a bone metastasis model, created by injecting MMT-060562 cells into the bilateral tibiae of 6-8-week-old female C3H mice. After 2 weeks, the lateral tumors were treated by excision, cryotreatment using liquid nitrogen, excision with anti-PD-1 treatment, and cryotreatment with anti-PD-1 treatment. Anti-mouse PD-1 4H2 was injected on days 1, 6, 12, and 18 post-treatment. The mice were euthanized after 3 weeks; the abscopal effect was evaluated by focusing on growth inhibition of the abscopal tumor. The re-implantation of frozen autografts significantly inhibited the growth of the remaining abscopal tumors. However, a more potent abscopal effect was observed in the anti-PD-1 antibody group. The number of CD8+ T cells infiltrating the abscopal tumor and tumor-specific interferon-γ (IFN-γ)-producing spleen cells increased in the liquid nitrogen-treated group compared with those in the excision group, with no significant difference. The number was significantly higher in the anti-PD-1 antibody-treated group than in the non-treated group. Overall, re-implantation of tumor-bearing frozen autograft has an abscopal effect on abscopal tumor growth, although re-implantation of liquid nitrogen-treated bone grafts did not induce a strong T-cell response or tumor-suppressive effect.

Revision surgery for instrumentation failure after total en bloc spondylectomy: a retrospective case series

Background

There have been several reports of instrumentation failure after three-column resections such as total en bloc spondylectomy (TES) for spinal tumors; however, clinical outcomes of revision surgery for instrumentation failure after TES are seldom reported. Therefore, this study assessed the clinical outcomes of revision surgery for instrumentation failure after TES.

Methods

This study employed a retrospective case series in a single center and included 61 patients with spinal tumors who underwent TES between 2010 and 2015 and were followed up for > 2 years. Instrumentation failure rate, back pain, neurological deterioration, ambulatory status, operation time, blood loss, complications, bone fusion after revision surgery, and re-instrumentation failure were assessed. Data were collected on back pain, neurological deterioration, ambulatory status, and management for patients with instrumentation failure, and we documented radiological bone fusion and re-instrumentation failure in cases followed up for > 2 years after revision surgery.

Results

Of the 61 patients, 26 (42.6%) experienced instrumentation failure at an average of 32 (range, 11–92) months after TES. Of these, 23 underwent revision surgery. The average operation time and intraoperative blood loss were 204 min and 97 ml, respectively. Including the six patients who were unable to walk after instrumentation failure, all patients were able to walk after revision surgery. Perioperative complications of reoperation were surgical site infection (n = 2) and delayed wound healing (n = 1). At the final follow-up, bone fusion was observed in all patients. No re-instrumentation failure was recorded.

Conclusion

Bone fusion was achieved by revision surgery using the posterior approach alone.

The process of bone regeneration from devitalization to revitalization after pedicle freezing with immunohistochemical and histological examination in rabbits

The pedicle freezing procedure by liquid nitrogen is a method for the reconstruction of tumor-bearing bone after malignant tumor resection. However, the regenerative mechanism of bone after the pedicle freezing procedure is unclear. We investigated the complete process from devitalization to revitalization of bone after the pedicle freezing procedure in 13 rabbits. After osteotomy the 5 mm distal femurs were immersed in liquid nitrogen, and the specimens were divided into frozen area and sub-frozen area. The bilateral femurs were harvested for evaluation of bone regeneration by histological and immunohistochemical examination (VEGF, CD31, BMP-2 and Runx2) from 1 week to 52 weeks. The diameter of operating femurs was compared with contralateral femurs from 6 weeks to 52 weeks. No viable cells could be found from 1 to 8 weeks in the frozen area, and a mean 1.83 cm necrotic range were detected in the sub-frozen area. The periosteal reaction, massive fibrous tissue and immature bone matrix invaded from the normal area to the necrotic area from 12 weeks. Subsequently, the necrotic bone was gradually replaced by newly formed bone by creeping substitution, with endochondral and intramembrane bone formation. The diameter of frozen femurs was significantly larger than the contralateral femur at the same period from 8 weeks to 52 weeks (P < 0.01). All immunohistochemical factors were positively expressed in both areas at different time points. The active osteoblasts and microvessel migrated from marrow cavity and periosteum into dead bone. This study suggested that the frozen bone not only provides a scaffold but also possesses excellent osteoinductive properties.