OBJECTIVE: To explore the design points of a three-dimensional (3D) printed customized cementless intercalary endoprosthesis with an intra-neck curved stem and to evaluate the key points and mid-term effectiveness of its application in the reconstruction of ultrashort bone segments in the proximal femur. METHODS: Between October 2015 and January 2021, 17 patients underwent reconstruction with a 3D printed-customized cementless intercalary endoprosthesis with an intra-neck curved stem. There were 11 males and 6 females, the age ranged from 10 to 76 years, with an average of 30.1 years. There were 9 cases of osteosarcoma, 4 cases of Ewing sarcoma, 2 cases of chondrosarcoma, 1 case of liposarcoma, and 1 case of myofibroblastoma. The disease duration was 5-14 months, with an average of 9.5 months. Enneking staging included 16 cases of stage ⅡB and 1 case of stage ⅢB. The distances from the center of the femoral head to the body midline and the acetabular apex were measured preoperatively on X-ray images. Additionally, the distances from the tip of the intra-neck curved stem to the body midline and the acetabular apex were measured at immediate postoperatively and last follow-up. The neck-shaft angle was also measured preoperatively, at immediate postoperatively, and at last follow-up. The status of osseointegration at the bone-prosthesis interface and bone growth into the prosthesis surface were assessed by X-ray films, CT, and Tomosynthesis-Shimadzu metal artefact reduction technology (T-SMART). The survival status of the patients, presence of local recurrence or distant metastasis, and occurrence of postoperative complications were assessed. The recovery of lower limb function was evaluated pre- and post-operatively using the Musculoskeletal Tumor Society (MSTS) scoring system, and pain relief was evaluated using the visual analogue scale (VAS) scores. RESULTS: The patient's femoral resection length was (163.1±57.5) mm, the remaining proximal femoral length was (69.6±9.3) mm, and the percentage of femoral resection length/total femoral length was 38.7%±14.6%. All 17 patients were followed up 25-86 months with an average of 58.1 months. During the follow-up, 1 patient died of lung metastasis at 46 months postoperatively, and the remaining 16 patients survived tumor-free. There was no complication such as periprosthetic infection, delayed incision healing, aseptic loosening, prosthesis fracture, or periprosthetic fracture. No evidence of micromotion or wear around the implanted stem of the prosthesis was detected in X-ray and T-SMART evaluations. There was no significant radiolucent lines, and radiographic evidence of bone ingrowth into the bone-prosthesis interface was observed in all stems. There was no significant difference in the distance from the tip of the curved stem to the body midline and the apex of the acetabulum at immediate postoperatively and last follow-up compared with the distance from the center of the femoral head to the body midline and the apex of the acetabulum before operation, respectively (P>0.05), and there was no significant difference in the above indexes between immediate postoperatively and last follow-up (P>0.05). The differences in the neck-shaft angle at various time points before and after operation were also not significant (P>0.05). At last follow-up, the MSTS score was 26.1±1.2 and the VAS score was 0.1±0.5, which were significantly improved when compared with those before operation [19.4±2.1 and 5.7±1.0, respectively] (t=14.735, P<0.001; t=21.301, P<0.001). At last follow-up, none of the patients walked with the aid of crutches or other walkers. CONCLUSION The 3D printed customized cementless intercalary endoprosthesis with an intra-neck curved stem is an effective method for reconstructing ultrashort bone segments in the proximal femur following malignant tumor resection. The operation is reliable, the postoperative lower limb function is satisfactory, and the incidence of complications is low.
Female ; Male ; Humans ; Child ; Adolescent ; Young Adult ; Adult ; Middle Aged ; Aged ; Femur/surgery* ; Lower Extremity ; Bone-Implant Interface ; Femur Head ; Artificial Limbs

OBJECTIVE: To investigate the long-term effectiveness of uncemented allograft-prosthesis composite (APC) for reconstruction of bone defects after proximal femur tumor resection. METHODS: Between June 2007 and March 2014, 21 patients who underwent uncemented APC reconstruction of proximal femur after tumor resection were retrospectively evaluated. There were 9 males and 12 females with an average age of 33.2 years (range, 19-54 years). There were 9 cases of giant cell tumor of bone, 5 cases of osteosarcoma, 4 cases of osteoblastic osteosarcoma, 2 cases of chondrosarcoma, and 1 case of undifferentiated pleomorphic sarcoma. Thirteen cases of benign bone tumors were all classified as stage 3 by Enneking staging; and 8 cases of malignant bone tumors were classified as grade ⅡB in 7 cases and grade ⅡA in 1 case according to the American Joint Committee on Cancer (AJCC) staging system. Among them, 7 patients underwent reoperation after recurrence, and the rest were primary operations; 8 patients presented with pathological fractures. The preoperative Harris hip score (HHS) and American Musculoskeletal Tumor Society (MSTS) score was 40 (30, 49) and 9.1±3.5, respectively. The length of osteotomy was 80-154 mm, with an average of 110 mm. At 1 year after operation and last follow-up, HHS and MSTS scores were utilized to evaluate the function of hip joint; the gluteus medius strength score was used to evaluation of the hip abduction function. Image examinations were taken at 1, 3, 6, 9, and 12 months after operation and every year thereafter to assess the union of allograft-host bone interfaces. Intra- and post-operative complications were also recorded. RESULTS: All patients were followed up 84-163 months (mean, 123.5 months). At 1 year after operation and last follow-up, the HHS and MSTS scores significantly improved when compared with the preoperative scores ( P<0.05). However, there was no significant difference in the HHS score, MSTS score, and gluteus medius strength score between the two time points after operation ( P>0.05). Image examination showed that all allograft-host bone interfaces achieved union after 5-10 months (mean, 7.6 months). At last follow-up, all patients had bone resorption, including 11 severe cases, 4 moderate cases, and 6 mild cases; the bone resorption sites included Gruen 1, 2, and 7 regions. Complications included 10 fractures and 1 prosthetic fracture. Local recurrence occurred in 3 patients and pulmonary metastasis in 3 patients. CONCLUSION Uncemented APC is a reliable method for the reconstruction of bone defects after proximal femur tumor resection. It has the good long-term effectiveness and possesses obvious advantages in the union at the bone-bone surface.
Adult ; Female ; Humans ; Male ; Allografts/pathology* ; Bone Neoplasms/surgery* ; Bone Resorption/pathology* ; Bone Transplantation/methods* ; Femur/surgery* ; Osteosarcoma/pathology* ; Prostheses and Implants ; Retrospective Studies ; Treatment Outcome ; Young Adult ; Middle Aged