In recent years, with the improvement of the survival and limb salvage rates after neoadjuvant chemotherapy, considerations on improving limb function on the premise of complete resection of the tumor should be made. Joint-preservation limb salvage (JPLS) is an effective method for treating osteosarcoma of limbs in children and adolescents. It was first used in epiphysis-preservation limb salvage (EPLS) for malignant bone tumors in children. Amitani et al. then proposed a limb salvage procedure that preserves the knee joint. In a recent study, Takeuch et al. called it joint-preserving surgery (JPS). In the past decade, our team has been studying and improving this surgical approach [13–16], and because of the rise of the patient's age and the closure of the physis, we named it joint-preservation limb salvage.
In this study, 19 patients with OS who underwent the JPLS were followed-up 12–228 (median 62) months and had an MSTS score of 27(range 24 to30) points. From 2009 until now, our team has committed to the clinical study of JPLS, fully confirming that joint-preservation biological reconstruction surgery after receiving neoadjuvant chemotherapy can achieve a good prognosis and limb function in patients. During this period, other studies also reported a higher limb function score. Tsuchiya et al. classified osteosarcoma around the knee joint and then maximally preserved the epiphysis according to the size of the extent of tumor invasion of the epiphysis. Twenty patients obtained good limb function and a lower local recurrence rate after joint-preserving surgery by different means. Chen et al. performed a joint-sparing hemicortical resection and biological reconstruction in six patients with high-grade osteosarcoma, and the postoperative MSTS score was as high as 97.7%. Their team preserved the anterior and posterior cruciate ligaments and one of the collateral ligaments on both sides, and argued the higher MSTS score was due to knee stability. Wong et al. applied computer navigation technology to achieve accurate bone resection and preserve the epiphysis as much as possible. They applied a special tumor prosthesis to repair neoplastic bone defects in four patients aged 6 to 14 years, of whom one died of lung metastasis five months after surgery, and the remaining three patients were followed up for 26, 45.7, and 52.3 months, with an MSTS limb function score of 30.
At present, most studies[13, 17–19] have confirmed that under the premise of ensuring that tumor resection meets the requirements of safety, the implementation of JPLS will not reduce patients' survival rate or increase the postoperative recurrence rate and the occurrence of complications. On the contrary, it brings better limb function. Furthermore, since the tumor bone inactivation site does not involve the articular surface cartilage and the articular surface cartilage and surrounding soft tissues are preserved as much as possible, so there is no significant impact on the knee joint function in the later stage.
Therefore, we argue that the reconstruction concept of JPLS should be prioritized in clinical practice under strict adherence to effective neoadjuvant chemotherapy.
The contents of JPLS include epiphysial-preservation tumor segment bone resection and bone defect repair, and because the used tumor segment bone has the advantages of lower rejection, low price, and good bone healing, we generally use inactivated tumor segment bone to repair bone defects.At present, the main modes of bone inactivation in the tumor segment are liquid nitrogen freezing , hypertonic saline  external radiotherapy, and alcohol. Sung et al. experimentally demonstrated that 95% of alcohol can completely kill tumor cells without interfering with osteogenesis and effectively preserves joint function. A pilot study by our team in ten patients with OS treated with JPLS and using 99% alcohol resulted in one patient dying of local recurrence and multiple metastases 13 months after surgery, three patients dying due to multiple metastases 9, 12, and 24 months after surgery, and three patients required reoperation due to inactivated bone fractures, with a mean International Society of Limb Salvage (ISOLS) graft score of 31 (87%) and a mean Musculoskeletal Tumor Society (MSTS) functional score of 23 (77%) at the last follow-up. In this study, 16 patients with osteosarcoma around the knee joint were treated with alcohol-inactivated bone replantation.Four patients underwent open reduction and internal fixation with an embracing fixator due to inactivated bone fracture 2–9 months after surgery. One patient underwent extended resection of the tumor due to two soft tissue recurrences within 11 months after surgery. Finally, five patients were followed up for 12 months after surgery without abnormalities.
We found that the MSTS limb function score in the joint-preservation group was higher than that in the prosthesis-replacement group, consistent with a previous study by Chen et al. . In their MSTS function evaluation of 90 osteosarcoma patients, the biological reconstruction and joint-preservation scores (25.0 ± 3.3 and 25.1 ± 3.6) were significantly higher than the mechanical reconstruction and joint resection scores (23.4 ± 3.7 and 23.1 ± 3.4, P < 0.05). San-Julian and Vazquez-Garcia retrospectively analyzed the data of patients who underwent bone tumor arthrotomy over 30 years and found that joint-preservation resulted in a higher MSTS score than joint fusion and prosthesis implantation in the long run. Kensaku et al. investigated patient satisfaction after JPLS and JRLS. They found that MSTS and TESS scores were significantly higher in the JPLS group, indicating that these patients were more satisfied with limb function.
At present, the evaluation of the quality of life of patients with OS undergoing different surgical methods mainly involves the difference between limb preservation and amputation [26–29], and there are few surveys and studies on the quality of life after joint preservation. Therefore, in this study, we applied the SF-36 to observe patients' quality of life after different limb preservation methods. Xu et al. found no significant difference in patients' quality of life with various limb salvage methods. However, we found that the joint-preservation group's physical function and social function scores were higher than those of the prosthesis-replacement group, indicating that the physical function and social function related to the quality of life of the joint-preservation group were improved. These data are consistent with the study results by Kensaku et al., who investigated the SF-36 scores in 62 patients with osteosarcoma after limb preservation. The physical functioning domain of the SF-36 score is a measure of whether a patient's health status prevents regular physical activity, which can also reflect limb motor function. Social functioning is used to measure the impact of physical and psychological problems on the quantity and quality of social activities and evaluate the effect of health on social activities. Therefore, JPLS may results in a better life satisfaction than JPRS, but more research is needed to confirm this conclusion.
Previous studies have found good knee range of motion and function after joint preservation [31, 32], and to further explore the knee function status after JPLS, our study also added the IKDC score to evaluate the postoperative joint function and movement. The IKDC score provides a comprehensive evaluation of the subjective symptoms and objective signs of the knee system and applies to various knee conditions. In the past, the IKDC score was mainly used for assessing ligament and tendon injuries, particularly for anterior cruciate ligament injuries and defects [33, 34], and has not been used to evaluate knee joint function after limb salvage for bone tumors. We showed that the IKDC score of the joint-preservation group was higher than that of the prosthesis-replacement group. Further analysis of the differences in each item of the IKDC score for completing various daily movements and sports conditions between the two groups showed that, except for the sitting with a bent knee, the joint-preservation group scores were superior, confirming that patients after JPLS could live and exercise similar to healthy subjects. Gerhard et al. found in a long-term follow-up of 30 patients with Ewing sarcoma that 83% of the patients could perform regular sports activities. For those, the weekly time spend on sports depended on the type of surgery performed, with the joint-preservation group scoring higher in terms of sports time and activity scores than those in the prosthesis reconstruction group. Therefore, biological reconstruction might lead to the ability to perform high-impact sports. In this study, by analyzing the effect of knee joint function on daily life and movement using the IKDC score, we have obtained a deeper understanding of the effect of JPLS on limb function status. Furthermore, the postoperative efficacy evaluation of JPLS is limited to joint function and the stability and movement ability of the knee joint should be focused on.
This study has some limitations, such as a non-uniform follow-up time and small sample size, resulting in potential errors in scale scores. In addition, this study did not systematically analyze the complications and prognosis of JPLS. The study subjects only involved surviving patients with osteosarcoma and lacked functional evaluation of dead patients, which may have biased the overall efficacy evaluation of JPLS.