Osteosarcoma is the most common highly malignant bone tumour in adolescent patients, with high mortality and disability rates. With the progress of neoadjuvant chemotherapy, imaging techniques and continuous development of reconstruction methods, limb salvage is always the preferred treatment model. Compared with amputation, limb salvage can achieve a similar 5-year survival rate and disease-free survival rate, and it can also obtain better psychological acceptance of patients [10]. Advances in chemotherapy and surgery have taken osteosarcoma from an almost universally fatal disease to one in which the majority of patients will survive with a meaningful quality of life [11].
How to choose the appropriate treatment program for bone defect reconstruction is a problem faced by surgeons. The reconstruction methods for bone defects after resection of malignant bone tumours include manufactured tumour-type artificial joints, biological constructs, bulk allografts, combinations of allograft-prosthetic composites and bone autografts to provide a stable reconstruction [12, 13]. Although prosthesis replacement is widely used at present, there are many complications, such as infection, loosening and fracture, especially in young adult patients who have high functional requirements. Furthermore, patients with high/intense activity have a higher failure rate. 3D-printed prostheses can also be used but much more expensive and complicated procedure [14]. In 2019, Zhao et al. [15], reported a systematic review of 33 studies with tumours affecting the distal tibia by searching the PubMed and EMBASE databases. In the 337 cases, biological reconstruction methods showed a better functional outcome (78.4% vs. 72.2%, P = 0.017) than non-biological prosthetic reconstruction methods. There are many problems with the use of allografts, such as the spread of infectious diseases, immune responses and social or religious beliefs, especially in Asian countries [16, 17]; a high incidence of complications (70%); and graft rejection (60%) in patients with limb sarcoma following allograft reconstruction for more than 10 years [18]. Furthermore, biological reconstruction might be the optimal reconstructive method. The patient’s own resected tumour segment after inactivation and reimplantation was considered to be an interesting idea for autografts used in bone defect reconstruction after resection of the malignant bone tumour. This technique will probably have a role in the management of osteosarcoma, and allograft use could be replaced in some settings [15], which is especially suitable for countries where foreign bone is difficult to obtain [19].
Extracorporeal irradiation and freezing are two common techniques used to eliminate residual tumour cells for autografts in limb salvage surgery with biological reconstruction of bone defects. Acceptable survival rates and satisfying function have been shown in some of the literature. In 1968, Spira and Lubin [20] first reported the application of extracorporeal irradiation in limb salvage treatment of malignant bone tumours. Compared with prosthetic reconstruction, this method is more economical and biological reconstruction is more acceptable to patients and their families [21, 22]. During the past 50 years, several oncologists have reported this inactivation method, but with the popularity of limb salvage surgery for malignant bone tumours, there are still many scholars who insist on and have interest in this technique [12, 23, 24]. A comparative study was performed to observe the effect of intraoperative extracorporeal irradiation and freezing treatments of tumour-bearing autografts, and no differences were found in the accumulated proportion of patients achieving union between the groups at 6, 9, 12, and 18 months [9]. Radiographic evaluation did not show differences in the average scores of the compared criteria. Tsuchiya et al. [25] applied liquid nitrogen freeze inactivation of autologous tumour bone in 28 cases of malignant bone tumours. The average follow-up time was 28.1 months (range 10–54), with bony union at a mean of 6.7 months after the operation in 26 patients (92.8%) and non-union occurring in two patients. Heat treatment would reduce bone strength but would lead to a loss of bone induction ability. Jeon et al. [26] treated 15 patients with distal femoral osteosarcoma with high-pressure steam inactivation of autologous bone reimplantation and followed them up for an average of 56 months (35–78 months). After surgery, five patients presented with non-union of bone, three patients presented with a loose prosthesis and no patients had an infection.
As a traditional biological bone reconstruction model, extracorporeal irradiation for limb salvage therapy has been widely reported, while the alcohol-inactivated technique has been rarely reported. Complications, such as graft fracture, infection, and non-union, must have an obviously negative effect on whole graft survivorship. The effectiveness of tumour eradication with the alcohol-inactivated technique has not yet been clearly revealed. We have developed a joint-preserving limb salvage approach for the treatment of osteosarcoma of the distal femur that involves reimplantation of alcohol-inactivated bone based on findings from a previous study. Alcohol might play a double role in the autograft: one is its killing effect on microbes, as well as tumour cells, and the other is its non-interference in the process of creeping substitution from the host [27]. Ten patients with Enneking stage IIb osteosarcoma were treated by alcohol-inactivated autograft reimplantation with joint preservation. The patients were followed up for an mean of 34 months, and all patients obtained first-stage healing, with a mean MSTS function score of 23 (77%) [28]. Our preliminary findings indicate that alcohol inactivation is a feasible approach that may help preserve the important structures of the joint and avoid long-term complications that can occur with endoprosthetic replacement [29]. Additional studies are needed to fully evaluate the efficacy and safety of this surgical approach. Our study provides a valuable reference for the clinical treatment of malignant bone tumours by comparing the clinical efficacy of the two methods. In this study, in the group of 14 osteosarcoma patients with alcohol inactivated autograft reimplantation, the 5-year survival rate was 71.4% (10/14), which is less than extracorporeal irradiation at 82.8% and frozen treatment at 84.4% [12].
Compared with other biological bone reconstruction methods, the alcohol-inactivated method is not only safe and effective in killing tumour cells but also more economical and convenient, with same shape matching for reimplantation. The disadvantage is that it takes a long time to complete the revascularization and to achieve normal bone union with the surrounding bone tissue. The adjacent joint may have cartilage degeneration and joint relaxation complications. The healing process of autograft bone reimplantation is the result of absorb, crawl and supersede and may be the main osteogenic pathway at the bone junction, and femur healing time is faster than tibia healing time [30]. In our study, most unions were detected within 8–14 months after surgery, which is similar to that of the research by Wu et al. [9] who performed a comparative study to observe the effect of intraoperative extracorporeal irradiation and freezing treatments. Ogura et al. [31] conducted a retrospective review of 11 patients undergoing reconstruction using a devitalized autograft, deep freezing and a vascularized fibula graft composite for lower extremity malignant bone tumours. A shorter union time (7 months) was reported for the autografts treated with freezing. The advantage of freezing may associated with the preservation of bone morphogenetic protein (BMP) in inactivated bone [32], which is superior to heat treatment, including extracorporeal irradiation, autoclaving, and pasteurization., Whether there is any difference in the efficacy of the three methods of autologous bone inactivation (extracorporeal irradiation, freezing or alcohol inactivation) has not been reported in a controlled study of clinical literature. Besides the influence factor of different inactivation methods, many other variable factors, such as the damage or quality of grafts, sites of tumour, reconstruction methods, stabilization during reconstruction, tumour local recurrence and infectious complications, may affect the process of graft osteogenic healing. All these relevant factors need to be considered and incorporated into the design of future studies.
The total complication rate (including tumour progression) was 42.9% (6/14) for irradiation treatment in the study, and Wu et al. [9], in an early, large sample size and controlled study, reported a complication rate of 44% (35/79). For the patients receiving alcohol inactivated autografts, we found a complication rate of 42.79% (6/14) that was a little higher than our previously reported 40% rate (4/10, with one local recurrence and three fractures of the inactivated bone or bending or breakage of the intramedullary nail [31]. Infections occurred in 14.3% (2 /14) of patients in each of our groups, which is higher than Wu et al. [9] who reported an infection rate of 8% (6/79) in the irradiation group and 5% (4/85) in the frozen autografts. The main worry about the alcohol inactivation technique is related to safety and the potential risk of recurrence, although its safety and effectiveness at killing tumour cells has been proven before in our preliminary findings the outcome in the management of osteosarcoma of the distal femur [28] and alcohol inactivated autograft-prosthesis composite for grade III giant cell tumor treatment [30]. Even with the clinical application of neoadjuvant chemotherapy and technical improvements in limb salvage surgery, local recurrence occurred in 11.6% of all patients and 12.4% of patients presented with distant metastases of osteosarcoma in a study by Bielack et al. [33]. Local recurrence presented at the same rate 14.3% (2/14) between the irradiation group and the alcohol inactivation group in our study, respectively, and the overall tumour recurrence rate was 15%(12/79) in the group treated with extracorporeal irradiation and 11% (9/85) in the group treated with freezing in the study by Wu et al. [9]. No tumour recurrence originating from inactivated bone was observed. It proved that either 50 Gy irradiation or 30 minutes of alcohol inactivation in autografts could achieve similar and reliable efficacy in eradicating tumour cells. Implantation of the tumour cells at the time of surgery is thought to be one of the causes of local recurrence [34]. In terms of survival, there was no difference between reconstructions receiving composites and intercalary grafts [35], which is similar to what we found in our study.
Although satisfactory outcomes were obtained in this study, several limitations exist. First, this was a retrospective study with a short follow-up period and small sample size, which may affect the reliability of the results. Further studies involving a larger cohort of patients and longer follow-up are needed to fully evaluate the efficacy and safety of this treatment approach. Second, the selection bias associated with surgical methods may affect the clinical outcomes. Alcohol-inactivated bone requires a longer time to accomplish revascularization and to integrate with the surrounding bone, which leads to greater length of time required for bone healing after surgery.