Artificial custom prosthesis replacement has become an important method for functional reconstruction of bone tumor resection in limb-sparing surgery [1]. Like common prosthetic replacements, tumor prosthesis replacements have been associated with complications such as infection, loosening, and prosthesis fracture. Unlike group-mounted prostheses where only the destroyed portion can be replaced after a fracture, a fracture revision of a custom-made oncologic prosthesis usually requires replacement of the entire prosthesis. In cases where the extramedullary portion of a cemented custom tumor prosthesis is accidentally fractured and the intramedullary portion is intact without loosening, it is very difficult to remove the bone cement from the medullary cavity of the stem and remove the stem during revision surgery. As with the revision of a cemented prosthesis, the stem is usually dissected, the cement is removed with special instruments, and the stem is removed. The dissected stem is repositioned and tied in place, and a new prosthesis with an elongated stem is reinserted and cemented in place. This step is more difficult in cemented custom tumor prosthesis revision. Firstly, it is very difficult to remove the broken stem, which may cause fracture of the backbone; it is traumatic and takes a long time, which increases the chance of infection; secondly, the stem of the custom tumor prosthesis itself is already very long, and the remaining length of the backbone is small, which is not conducive to further lengthening the stem of the new prosthesis; the dissection of the backbone is not easily healed by the bone cement; it is not conducive to early functional exercise after surgery, etc. Cemented custom tumor prosthesis revision complications are high, postoperative functional recovery is poor, and the expected prosthesis life is short. In cases where the extramedullary portion of cemented custom tumor prosthesis is accidentally fractured and the residual body part of the prosthesis is of sufficient length, while the intramedullary portion is intact and no loosening occurs, the residual portion of the prosthesis can be used. We have designed our own sleeve type revision prosthesis for this situation. This prosthesis is made of the same material as the original prosthesis. One end of this prosthesis is the snapped part, the snapped part is cylindrical, the wall thickness is 4mm, there are some locking holes on the wall, its length is 5-7cm, the inner diameter is larger than the extramedullary part of the broken prosthesis 2-3mm, it can be directly snapped on the residual extramedullary part of the broken prosthesis, and connected with bone cement bonding and locking nail fixation; the other end is the same as the original prosthesis The other end is the same as the corresponding part of the original prosthesis. We applied this prosthesis to a case of cervical junction fracture of a custom-made tumor prosthesis in the proximal femur and a case of extramedullary body fracture of a custom-made tumor prosthesis in the distal femur, and we report the following. 1. General information Case 1: fracture of the cervical body junction of the proximal femoral custom tumor prosthesis. The patient was a 54-year-old male who underwent custom-made artificial tumor hip prosthesis replacement for chondrosarcoma of the upper right femur. The prosthesis fractured 28 or 5 months after surgery. Enneking score 27 before prosthesis breakage and Enneking score 1 after prosthesis breakage. Case 2: Distal femoral tumor customizing the extramedullary body of the prosthesis fracture. The patient was a 51-year-old female who underwent custom-made artificial tumor knee prosthesis replacement for a giant cell tumor of the right lower femur. The prosthesis fractured 32 months after surgery. The Enneking score was 28 before the prosthesis rupture and 4 after the prosthesis rupture. 2. Method The revision surgery was performed under epidural or general anesthesia. 1/2 or 1/3 of the original surgical incision length was taken and incised sequentially, revealing only the fractured part of the prosthesis. The fractured portion of the prosthesis is removed, and the snapped revision prosthesis is snapped to the extramedullary portion of the original prosthesis and attached by cemented and locked nail extrusion. The incision was rinsed, a drainage tube was placed, and sutures were placed in sequence. Intraoperative and postoperative antibiotics were applied for 3 days, and low molecular heparin sodium 2500 IU was injected subcutaneously for 7-10 days, and functional exercises were performed after the drainage tube was removed on the second day after surgery. 3. Results The surgeries were completed successfully. The operation time was 1~2 hours, and the intraoperative bleeding was less than 200ml. 14 days after the operation, the stitches were removed and the Ⅰ/nail healed. The mean score of the latest Enneking evaluation was 26 at 24 and 31 months of follow-up after revision of the knee and hip femoral socket prosthesis, respectively. There were no incision and periprosthetic infections, no deep vein thrombosis, no lower limb inequality and no complications such as prosthesis loosening and fracture, and no tumor recurrence and metastasis during the follow-up period. The application of various measures such as neoadjuvant chemotherapy has resulted in a 5-year survival rate of 50%-60% for patients with malignant bone tumors. Tumor prosthesis replacement has become an important procedure for limb preservation. In China, the number of custom tumor prosthesis used is high, with the extension of the use of years, custom tumor prosthesis fracture has become more and more problems we face. The incidence of custom oncology prosthesis fracture is 2,2%-5,8% [2,3].Slone RM et al. concluded that prosthesis fracture is caused by continuous cyclic stress that makes the prosthesis active or repeatedly stretched, while some parts of the custom prosthesis are thinner to suit the needs of the individual patient and the stress is too concentrated [4]. High restriction of the prosthesis, design defects that make a high concentration of stress in one part of the prosthesis, loosening of the prosthesis, and problems with the prosthesis material and manufacturing process are also factors associated with prosthesis fracture. Both domestic and international follow-up literature on a large number of custom tumor prostheses have reported that a new prosthesis is generally required in the revision of a fractured prosthesis [3 , 5]. In cases where the extramedullary portion of a custom tumor prosthesis is accidentally fractured, but the intramedullary portion is intact and not loosened, the removal of the still cemented prosthesis is very difficult and is one of the most difficult aspects of revision surgery, as is the revision of a normal cemented prosthesis. Although Glassman, Cameron, and Sydney recommended the use of greater trochanteric extension osteotomy, femoral stem osteotomy, and femoral cortical opening to assist in the removal of the prosthesis and cement in the revision of common prostheses [6, 7], special instruments are generally required, and the operation is complex, requiring a high level of surgeon skill and increasing the chance of complications such as fracture, osteotomy failure, and infection. This step is even more difficult when custom tumor prosthesis revision is performed. Because of the long intramedullary stalk of the cemented custom tumor prosthesis and the narrower intramedullary space of the diaphysis, the fracture, osteotomy failure, and infection occur. There is a higher chance of fracture, non-union of the osteotomy and other complications. With less bone remaining after tumor prosthesis replacement, it is more difficult to deal with various complications, sometimes catastrophic, and the patient has to undergo amputation. For patients, the surgery is long, traumatic, slow to recover and costly, and sometimes patients cannot afford the high cost and give up treatment. Revision of tumor prosthesis is usually fixed with bone cement again. Dohmae et al [8] measured the shear force at the bone-cement interface of cadaveric bone and found that the stress value after revision was 20.6% of that after the initial THR procedure, whereas the stress value after the second revision was only 6.8% of that after the initial THR procedure. The high complication and revision rate of cemented prostheses in revision surgery has been reported in the early literature [9], with the revision rate approaching or reaching 40% at 5-year follow-up [10]. Our design of the femoral socket revision prosthesis was searched and no similar design or application has been reported in China or abroad. It is indicated for cases in which the extramedullary portion of the prosthesis is accidentally fractured, the body of the prosthesis is of adequate length, and the intramedullary portion is firmly cemented intact. The use of socket revision prosthesis provides a new option and concept for the revision of prosthetic rupture. The snapped prosthesis has the following features compared with the traditional tumor prosthesis revision method: 1, easy to operate, only exposing the prosthesis break, directly snapping the new prosthesis to the original prosthesis with bone cement and strengthening the fixation with locking nails, without exposing the prosthesis in the intramedullary part of the femoral stem, greatly simplifying the surgical process, low surgical technique requirements, shortening the operation time, making the revision surgery simple and easy to perform. 2, no need to remove the bone cement fixed prosthesis stem in the medullary cavity, no need to remove the prosthesis stem in the medullary cavity, and no need to remove the bone cement fixed prosthesis stem. 3. short incision, patient trauma, fast recovery, early functional exercise, good recovery of limb function. 4. reduced the chance of complications such as infection in prosthetic revision. 5. lower cost of prosthesis than traditional revision prosthesis and safer operation, so that the patient’s medical costs are greatly reduced. 6. 6, does not affect the combination of prosthesis and bone, the expected life of the prosthesis socket should exceed the traditional revision prosthesis. The revision prosthesis is an innovative prosthesis, and the socket revision prosthesis can be used not only for the femur but also for other parts of the tumor custom prosthesis. It is worth to be promoted and applied in clinical work. 5.Conclusion Femoral socket revision prosthesis has high application value and good recent clinical results. The use of femoral socket revision prosthesis provides a new option and concept for the revision of prosthesis fracture. It overcomes the disadvantages of traditional revision techniques within its scope of application and makes the revision surgery simple and easy, with reduced intraoperative and postoperative complication rates, short operative time, minimal patient trauma, rapid recovery, and greatly reduced costs. The medium- and long-term results are subject to further observation.