In recent years, the application of tumor-based prosthesis in China has been increasing year by year. Compared with other reconstruction methods, artificial prosthesis reconstruction has the advantages of early weight-bearing walking and more satisfactory postoperative function, but the incidence of complications such as infection, loosening and fracture is still high. Infection is the most difficult complication to manage, and recent developments in prosthesis have not led to a decrease in infection rates. The main cause of aseptic loosening is stress masking or stress concentration, which can be reduced through improvements in prosthesis design, such as a new “pressurized” tumor-based prosthesis that has emerged in recent years to avoid stress masking and achieve satisfactory short-term follow-up results. Lengthenable prostheses are becoming the first choice for pediatric limb preservation therapy, especially with the recent emergence of non-invasive lengthenable prostheses. A significant number of tumor-based prostheses still require revision surgery each year. The method of prosthesis fixation (cement fixation or biologic fixation) remains a hot topic in this field. The literature in recent years has reported low rates of aseptic loosening for both cement fixation and biologic fixation, and the jury is still out on which method is more advantageous. Although artificial prosthesis reconstruction has obvious advantages over other reconstruction methods in some aspects, other reconstruction methods such as autograft/allograft, allograft prosthesis composite (APC) reconstruction or rotational molding should also be considered when choosing a reconstruction method. Other reconstruction methods such as rotational molding can be chosen. Only by choosing the appropriate reconstruction method according to the specific case can the best treatment effect be achieved. In the early 1970s, with the advent of the Memorial Sloan-Kettering Cancer Center’s chemotherapy regimen for osteosarcoma based on adriamycin and high-dose methotrexate, surgeons such as Ralph Marcove, Kenneth Francis and Hugh Watts began to use custom prostheses to reconstruct tumors after resection. This marked the beginning of limb preservation therapy in the field of bone tumors. The development of limb preservation therapy is the result of a multidisciplinary approach that includes a deeper understanding of tumor biology, the advent of neoadjuvant chemotherapy, precise imaging techniques, increasingly sophisticated surgical techniques, advances in material science, and the progressive refinement of prosthetic design. The combined development of these disciplines led to the gradual refinement of limb preservation therapy for primary malignant tumors of bone in the late 1970s. The common reconstruction methods in limb preservation therapy are allograft, autograft, endoprosthesis and allo/autograft prosthesis composite (APC). Initially, tumor-based prostheses for reconstruction of large bone defects after tumor resection were custom-made endoprosthesis, but due to the increase in the number of surgeries, the long preoperative waiting time for prosthesis production, and the need for intraoperative size adjustment, prosthesis manufacturers gradually began to pre-produce different sizes of custom-made prostheses, which is the predecessor of the modular prosthesis. This was the predecessor of the modular prosthesis. Then in the early 1980s, modular endoprosthesis emerged. The main development of oncologic prosthesis in the same period was the biological fixation technology, represented by the KMFTR prosthesis (kotz modular femur & tibia resection system) designed by Kotz, which is the predecessor of the HMRS (howmedica modular resection system) by Stryker. The design is the predecessor of Stryker’s HMRS (howmedica modular resection system) product. The design of the modular prosthesis is characterized by its small size, and the prosthesis is assembled on site according to the length of the osteotomy and the skeletal characteristics of the patient. Because of the advantages of modular prosthesis, it gradually replaced the custom-made prosthesis and became the mainstream design. However, for some special cases, such as the need for a special size stem or a special size prosthesis, the custom-made prosthesis is still retained as a supplement to the modular prosthesis. In the last 10 years, the number of modular prostheses used abroad is significantly higher than that of custom prostheses. The advantages of the modular prosthesis include replacing only the damaged component during revision and reducing limb shortening by lengthening the prosthesis with additional prosthetic components. The oncologic knee prostheses (lower femoral and upper tibial prostheses) used from the late 1970s to the mid-1980s had a simple hinge structure. Due to the high incidence of aseptic loosening on follow-up, and the increasing understanding of knee biomechanics, the rotating-hinge tumor knee was introduced in the mid-1980s. Grimer et al. in 1991 reported early follow-up results of rotating-hinge knees for limb-preserving reconstruction. The incidence of aseptic loosening was reduced compared to a simple hinged prosthesis [2]. Currently, tumor-based knee prostheses are essentially of rotating hinge construction. In recent years, the literature on the reconstruction of large bone defects after tumor resection has concluded that prosthetic reconstruction is the preferred method of reconstruction, and the advantages of prosthetic reconstruction include immediate postoperative stability and early weight-bearing ambulation, and better short-term and long-term postoperative function [7]. The main advantage of artificial prosthesis over allograft bone reconstruction is the lower incidence of infection. Prosthetic reconstruction of the upper femur, lower femur, upper tibia, upper humerus and scapula is very reliable. Reconstruction of the upper tibia and acetabulum is still difficult. Artificial prostheses can provide strong and stable reconstruction in the early postoperative period, but the rate of prosthetic failure remains high as patient survival increases [7]. (i) Prognosis of artificial prosthesis Recent papers on artificial prosthesis have focused on their follow-up outcomes. The definition of prosthesis failure varies from literature to literature, resulting in some differences in statistical prosthesis survival rates. Most of the literature defines prosthesis failure as any case in which a partial or total artificial prosthesis needs to be replaced for any reason. The 5-year survival rates for artificial prostheses in the literature published in the last two years range from 65-94%. The site of the prosthesis is the main factor affecting the survival rate of the prosthesis, with the highest survival rate for the superior humeral prosthesis, 88-93% for the inferior femoral prosthesis, and 58% for the superior tibial prosthesis. Bickels et al [7] reported short-term 2-year follow-up results of 110 cases of tumor-based prostheses for the lower femoral segment. 73 of the 110 cases had a group-matched prosthesis applied, all of which were cemented rotating hinge prostheses. The main complications were deep infection (5.4%) and aseptic loosening (5.4%). The 5-year and 10-year survival rates for the prostheses were 93% and 88%, respectively. The overall limb preservation rate was 96% and the functional excellence rate was 85%.Yasko et al. reported the long-term follow-up results of 54 cases with Finn rotating hinge tumor-type knees between 1991 and 1999, all with cemented prostheses. Of the cases with complications, 7 had broken prosthetic stems, 2 had infections, and 1 had aseptic loosening. 41 cases (76%) did not require reoperation. the median MSTS functional score was 84%. In addition, revision of cases with failed allograft bone reconstruction using artificial prostheses was followed up for a mean of 77 months after surgery, with a 5-year survival rate of 92% for the prosthesis [14]. The 3-year survival rate of tumor-based prosthesis reported in the relevant domestic literature was 81.8% , and the 5-year survival rate was 65%. (B) Postoperative function of patients There are many reports in the literature on the functional outcome of the affected limb after limb preservation surgery, but there is a lack of prospective and systematic results from evidence-based medicine. A significant number of cases in each of the current reports were unable to obtain a final functional score. Functional evaluation is generally performed using the MSTS 1987 or MSTS 1993 system [18]. the MSTS scoring system is a physician-administered score and the results are subjective. The Toronto Extremity Salvage Score (TESS) as a functional score performed by the patient himself can eliminate the subjective factors of the physician and should be used as an important reference in clinical work. The MSTS scores reported in the literature are 60-78% for the upper humeral prosthesis reconstruction, 60-73% for the upper femur, 66-85% for the lower femur, and 74-83% for the upper tibia. Extra-articular resection was overall less functional than intra-articular resection. (C) Artificial prosthesis-related complications With the continuous progress of surgical technology, the improvement of prosthesis design, and the continuous development of artificial materials, tumor-type artificial prosthesis has gone through different stages, and the main complications of each stage are different: before 1980, large segments of metal prosthesis reconstruction were less used, and the main complications of the prosthesis were mechanical failure and infection; from the early 1980s to the mid-1990s, due to From the early 80’s to the mid 90’s, due to the large number of tumor type artificial prosthesis, people accumulated more experience and improved the prosthesis design, the main complication was aseptic loosening; from the late 90’s to the present, people reduced the incidence of aseptic loosening through various methods, and infection became the main complication of artificial prosthesis again. 1, prosthesis infection. Prevention and treatment of prosthetic infection remains a difficult problem in limb preservation therapy. Infection is the main cause of artificial prosthesis reconstruction failure reported in the recent literature, and infection is the second cause of amputation after limb preservation surgery following local recurrence, with a prosthesis infection rate of 5.2-12% in the recent literature and no significant reduction in prosthesis infection rate in recent years. The highest incidence of infection occurred in the upper tibial prosthesis and the lowest in the upper humerus. In addition, prosthetic lengthening in pediatric patients leads to an increased rate of infection. Some literature reports that chemotherapy increases the rate of infection, but others report that chemotherapy does not increase the rate of infection. The success rate of revision surgery required for infection is 70%, and for most cases of infection, second-stage revision is usually chosen, and second-stage implantation of the prosthesis should be performed after chemotherapy is completed. In fact, in addition to the transfer of the gastrocnemius muscle flap during the initial surgery, the transfer of the free muscle flap during revision surgery to improve the soft tissue coverage is also necessary. 2. Aseptic loosening. Aseptic loosening is still the main complication of prosthetic reconstruction. The incidence of aseptic loosening reported in the literature in recent years ranges from 0-56%. The incidence of aseptic loosening is related to the site of the prosthesis, and the results reported in different literature vary. The highest rate of loosening is seen with the superior tibial prosthesis, and the best prognosis is seen with the superior humeral prosthesis. One of the most cited papers on prosthesis loosening is a 1996 paper by Unwin in which the 10-year incidence of aseptic loosening was 6.2% in the upper femoral segment, 32.6% in the lower femoral segment, and 42% in the upper tibial segment, with most loosening occurring in the third to eighth years after surgery. In recent years, some large cases have reported no aseptic loosening in any of the follow-up cases, which is consistent with the conventional view. Previously published literature has shown cases of aseptic loosening within 2 years postoperatively. This may be due to improvements in prosthesis design and the choice of fixation method. To reduce the occurrence of aseptic loosening, bone grafting at the host bone-prosthesis junction may be used to promote the formation of extracortical bone bridges, as they prevent aseptic loosening by preventing prosthetic wear debris from entering the bone-prosthesis interface. In addition, the incidence of aseptic loosening is significantly higher in pediatric patients than in adults, and it is now believed that aseptic loosening is the process rather than the result of complications with the prosthesis, which will inevitably lead to mechanical complications such as liner wear and prosthesis fracture if no active intervention is made. 3, polyethylene liner wear. The incidence of polyethylene liner wear increases as the artificial prosthesis is used for longer periods of time, and the incidence of polyethylene liner wear is higher in simple hinged prostheses than in rotating hinged prostheses. In a long-term follow-up of 335 cases of lower femoral prosthesis reconstruction, Meyer et al. found that 55 cases required liner replacement, and the average time to replace the liner after the initial surgery was 11 years, and some patients may require multiple replacement, and it is recommended that the liner should be aggressively replaced, otherwise it can lead to other complications such as aseptic loosening. 4. Dislocation. Hip dislocation is the most common complication of the upper femoral prosthesis, with a dislocation rate of 11-15%. At present, the upper femoral hip reconstruction is generally performed using a double-acting head, with the hip capsule routinely preserved, and acetabular molding is generally not performed. In addition, hip stability can be enhanced by local muscle reconstruction, and the retention of the hip capsule does not increase the recurrence rate of tumors. The incidence of knee tumor-type prosthesis dislocation is low, mainly related to the design of the prosthesis. Currently most manufacturers produce tibial components of the prosthesis are made according to the design standard of knee joint distraction ≥ 39mm before dislocation occurs, Eckardt found through biomechanical analysis of six common prosthetic tibial rotating components in the United States, the tibial side components have a higher risk of dislocation if the length is < 4.5cm, these tibial components should not be used in patients with extensive soft tissue resection tumors. 5. Other. Patellofemoral complications are easily overlooked. healey et al. found patellofemoral complications in 35 (63%) of 27 cases of rotating hinge knees of the lower femoral segment at follow-up, including 11 cases of patellofemoral impingement, 2 cases of patella fracture, and 2 cases of osteonecrosis. The ratio of the patellar tendon length to the height of the patellar tendon attachment point (i.e., the distance between the tibial articular surface tangent and the tibial tuberosity in lateral knee X-rays) was 0.9 on average in patients with patellar impingement, which was significantly lower than in patients without impingement, which was 1.4. The postoperative function of the low patella was poorer than that of the normally positioned patella. In cases of patellofemoral-induced knee pain, patellar surface replacement should be considered for symptomatic relief in cases of revision or other reasons requiring reoperation. Hot issues of tumor-based prosthesis reconstruction (a) Fixation method It is not yet possible to compare which method is better: cement fixation or biological fixation. The literature reports satisfactory follow-up results for cement-based prostheses, while the follow-up results for biologic prostheses are also satisfactory. There are no randomized controlled clinical studies in the literature on both fixation methods for the same prosthesis, and there is insufficient evidence to prove which fixation method is more convenient for removal of the prosthesis during revision surgery. The rate of aseptic loosening of cemented prostheses has decreased in recent years. Stresses at the bone-prosthesis or cement-prosthesis interface are significantly lower with rotating hinged prostheses than with simple hinged prostheses. In addition, the design of the collar at the prosthesis-bone junction with hydroxyapatite spraying effectively promotes the formation of extracortical bridges and thus reduces the incidence of aseptic loosening, and two publications have reported that nontraditional cement fixation methods have a lower incidence of aseptic loosening than traditional cement fixation methods. The traditional cement fixation method is to expand the medullary cavity to a diameter 3-4 mm larger than the stem of the prosthesis, resulting in a 2 mm thick cement around the stem of the prosthesis, whereas the non-traditional cement fixation technique is to expand the medullary cavity to exactly the same thickness as the stem of the prosthesis to obtain stable fixation by inserting the prosthesis before cement fixation and filling the tiny gap between the prosthesis and the bone with cement to obtain stronger fixation before final fixation of the prosthesis. . The advantage of this fixation method is that a thicker diameter stem can be used, thus reducing the risk of stem fracture; in addition, more bone volume can be retained. The design of the prosthesis is more important than the fixation technique, and Grimer recently reported preliminary clinical results of a new distal femoral fixation technique, the pressurized prosthesis (Biomet, USA). This prosthesis uses spring-generated pressure on the broken end of the osteotomy to avoid stress masking, and the proximal end of the prosthesis is fixed with a locking pin. The collar of the prosthesis is sprayed with hydroxyapatite to facilitate bone ingrowth, and the tibial side is cemented. The clinical outcome of this prosthesis requires further follow-up, but early results are satisfactory. O'Donnell recently reported that chemotherapy affects bone remodeling, and until then there has been no objective evidence of an effect of chemotherapy on bone remodeling. Chemotherapy has now been shown to result in a higher rate of prosthetic complications, and physicians should consider the effect of chemotherapy on the prosthesis when selecting a fixation modality for different cases. (ii) Lengthenable prostheses Limb inequality in children after limb preservation is a hot issue in the field of limb preservation in recent years. With the continuous improvement of lengthenable prosthesis design, the problem of unequal limb length can be solved by adjusting the length of the prosthesis after implantation. The lengthenable prosthesis has gone through three stages of development: invasive lengthening, minimally invasive lengthening and non-invasive lengthening. The earliest application of lengthenable prosthesis was in 1976, and the representative of the first generation of lengthenable prosthesis is the British SEER prosthesis (Stanmore Extensible Endoprosthetic Replacement), which has undergone worm drive design, tungsten ball filling design (1982), C-shaped collar design (1988) and minimally invasive design prosthesis (1993). The second generation of extendable prostheses, the modular prosthesis, is typified by the HMRS prosthesis. This was followed by the automatic lengthenable prosthesis, in which the lengthening mechanism is a ratchet mechanism driven by the knee flexion motion, which lengthens the prosthesis by means of a screw. This was followed by the Phenix non-invasive lengthenable prosthesis, which was first invented by the French and has been improved several times since the 1990s and is now commercially known as the Repiphysis prosthesis (Wright Corporation, USA). The lengthenable prosthesis through the action of electromagnetic field outside the body, through the electromagnetic action to make the prosthesis lengthen. Currently the most used is the minimally invasive or non-invasive lengthenable prosthesis. The indications for selecting a lengthenable prosthesis are generally expected to be >3 cm for lower extremity shortening and >5 cm for upper extremity shortening. lengthenable prosthesis reconstruction is generally not required for girls >11 years of age and boys >13 years of age, as they can minimize limb inequality by selecting a slightly longer prosthesis with a thin-stemmed biologically fixed prosthesis on the contralateral uninvolved joint surface (which has minimal effect on epiphyseal growth). The disadvantage of the non-invasive lengthenable prosthesis is that it can only be cemented, as a violent hammer impact can damage the lengthening device of the prosthesis if biologic fixation is performed. In addition, patients with non-invasive lengthenable prostheses cannot undergo MRI because the magnetic field of the MRI will affect the lengthening device. The main problem with lengthenable prostheses is aseptic loosening. This is because the growth of the child’s bones increases the transverse diameter of the bones and the medullary cavity, and the high activity level of the child is another cause of loosening. If a child develops aseptic loosening as an adult, the lengthenable prosthesis should generally be replaced with a normal adult prosthesis. Another major problem with lengthenable prostheses is joint stiffness, which is mainly found in invasive lengthenable prostheses, causing stiffness on the one hand because multiple surgeries make the wound scar contracture serious, rehabilitation exercise difficulties; on the other hand, because the limb is lengthened when the knee flexion patellar tendon and quadriceps tendon length relative shortening, flexion difficulties. In addition, joint stiffness may be an early symptom of low-grade infection and should be taken seriously. Although many minimally invasive lengthening prostheses are now replacing traditional open lengthenable prostheses, minimally invasive lengthenable prostheses still increase the patient’s chances of infection. Traditional open lengthening procedures have a higher chance of causing infection than minimally invasive lengthening procedures, and reconstruction of the upper tibial lengthenable prosthesis continues to have the highest chance of infection of any site. Another advancement in prosthesis design is the biologic preserved articular surface noninvasive lengthenable prosthesis, in which the prosthesis is secured to the preserved articular surface at one end by a hydroxyapatite spray surface and small fixation screws so that the affected articular surface can be preserved. A recent publication reported the use of this type of prosthesis for limb reconstruction after tumor resection in eight patients with distal femoral osteosarcoma, with an average follow-up of 24 months after surgery and full weight bearing at 6 weeks postoperatively; there were no prosthesis-related complications or revision surgery. One patient underwent noninvasive lengthenable extension with an average MSTS93 score of 80%. If this prosthesis design proves to be successful in practice, it has the potential to change conventional wisdom regarding the treatment of certain tumors. IV. Summary As more clinical follow-up results accumulate, the design and use of oncology-based prostheses will continue to improve. The design of prostheses that are more compatible with the human biomechanical environment will effectively reduce the incidence of aseptic loosening and prosthetic fracture. In the next few years, the focus will continue to be on updating the design of prostheses to reduce mechanical failure, improving the design of non-invasive extendable prostheses for children, and the choice of fixation methods. As the development of artificial prostheses continues, more patients with bone malignancies will be able to retain a functional limb with a longer service life and fewer complications.