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Background Surgical treatment for hinge failure in mega‐prosthesis continues to be a challenge. This study introduces a new method for treating hinge failure by using a unilateral prosthesis and hinge revision. Case Presentation We here present two patients who underwent mega‐prosthesis reconstruction after resection of osteosarcoma in the distal femur. To address the issue of knee hyperextension after mega‐prosthesis reconstruction, one patient underwent three revision surgeries, two surgeries were performed using the original hinge, and one surgery involved a newly designed hinge. To resolve the problem of dislocation, one patient underwent three revisions, with the first two revisions not involving hinge replacement and the third revision involving a newly designed hinge. Two replacements of unilateral prosthesis and hinge renovations were successful. Conclusions Unilateral prosthesis and newly designed hinge device revision are effective in treating the failure of old‐fashioned mega‐prosthesis hinges.

Objective To explore the potential effect of three allogenic bone substitute configurations on the viability, adhesion, and spreading of osteoblasts in vitro. Methods Freeze‐dried cortical bone were ground and fractions were divided into three groups with different sizes and shapes, defined as bone fiber (0.1 mm × 0.1 mm × 3 mm), bone powder (0.45–0.9 mm), and bone granule group (3–6 mm). MC3T3‐E1 cells were divided and co‐cultured within groups to induce cell adhesion. The configuration of allogenic bone was captured by scanning electron microscopy and confocal laser scanning microscopy, and substrate roughness values were quantified. Cell adhesion rate was assessed using the hemocyte counting method, cell viability was determined by CCK‐8 assay and live/dead staining, and cell morphology was visualized by Phalloidin and DAPI, and the mRNA expression of adhesion‐related gene (vinculin) of different substitutes were determined with quantitative real‐time polymerase chain reaction. Results The roughness values of bone fiber, bone powder, and bone granule group were 1.878 μm (1.578–2.415 μm), 5.066 μm (3.891–6.162 μm), and 0.860 μm (0.801–1.452 μm), respectively (bone powder group compared with bone granule group, H = 18.015, P 0.05). In addition, representative cell adhesion rates at 24 h showed significantly lower cell adhesion rate in bone fiber group (20.3 ± 1.6%) compared to bone powder (29.3 ± 4.4%) and bone granule group (27.3 ± 3.2%) (F = 10.51，P = 0.009 and P = 0.034, respectively), but there was no significant difference between the latter two groups (P > 0.05). Interestingly, the expression of vinculin mRNA steadily decreased in a time‐dependent manner. The vinculin expression reached its peak at 6 h in each group, and the vinculin levels in bone fiber, bone powder, and bone granule group were 2.119 ± 0.052, 3.842 ± 0.108, and 3.585 ± 0.068 times higher than those in the control group, respectively (F = 733.643, all P

Objective Pre‐implantation sterilization procedures for tendons are important measures to reduce the risk of disease transmission, however these procedures may compromise tendon microarchitecture and biomechanical properties to varying degrees. We explore the effects of different sterilization procedures on the micro‐histology, biomechanical strength and biochemical properties of human tendon allografts in vitro study. Methods The tendon allografts were harvested from cadaveric donors after the donors were serologically screened by antibody or nucleic acid testing of infectious agents. All samples were divided into five groups, which were fresh‐frozen group (control group), 15 kGy gamma irradiation group, 25 kGy gamma irradiation group, 70% ethanol group, and peracetic acid‐ethanol group. Each group included 10 tendons for testing. Histological staining and transmission electron microscopy were applied to observe the internal structure and arrangement of tendon collagen fibers, while the machine learning classifier was trained to distinguish the darker cross‐sections of collagen fibers and brighter backgrounds of the electron micrograph to detect the distribution of diameters of tendon collagen fibers. The viscoelasticity, mechanical properties and material properties of tendon allografts were examined to detect the influence of different intervention factors on the biomechanical properties of tendons. Results Histological staining and transmission electron microscopy showed that the structure of fresh‐frozen tendons was similar to the structures of other experimental groups, and no obvious fiber disorder or delamination was observed. In the uniaxial cyclic test, the cyclic creep of 25 kGy irradiation group (1.5%) and peracetic acid‐ethanol group (1.5%) were significantly lower than that of the control group (3.6%, F = 1.52, P = 0.039) while in the load‐to‐failure test, the maximum elongation and maximum strain of the peracetic acid‐ethanol group were significantly higher than those of the control group (F = 4.60, P = 0.010), and there was no significant difference in other biomechanical indicators. According to the experimental results of denatured collagen, it could be seen that no matter which disinfection procedure was used, the denaturation of the tendon sample would be promoted (F = 1.97, P = 0.186), and high‐dose irradiation seemed to cause more damage to collagen fibers than the other two disinfection procedures (296.2 vs 171.1 vs 212.9 μg/g). Conclusion Biomechanical experiments and collagen denaturation tests showed that 15 kGy gamma irradiation and 70% ethanol can preserve the biomechanical strength and biochemical properties of tendons to the greatest extent, and these two sterilization methods are worthy of further promotion.

Objective To propose a simple and practical clinical classification for tenosynovial giant cell tumor (TGCT) of the knee. Methods A retrospective study was conducted to verify the value and significance of this clinical classification. TGCT growth patterns, knee joint capsule, and bone erosion were applied to establish this novel clinical classification. Seventy‐eight patients who underwent surgery for TGCT from 2008 to 2016 were identified. This novel clinical classification was retrospectively applied to patients' existing classification, and patients with different TGCT types were statistically compared to verify the significance of the clinical classification. Results The clinical classification included three types and four subtypes. Type 1: localized TGCT, Subtype 1a: localized intra‐articular TGCT, Subtype 1b: localized extra‐articular TGCT. Type 2: diffuse TGCT, Subtype 2a: diffuse intra‐articular TGCT with bone normal, Subtype 2b: diffuse intra‐articular TGCT with bone destruction. Type 3: diffuse TGCT across the knee joint capsule. The mean follow‐up time for the 78 patients was 59.6 months. Twenty‐one patients were in Subtype 1a, four were Subtype 1b, 38 were Subtype 2a, seven were Subtype 2b, and eight were Type 3. Oncological results and surgical complications differed significantly (P = 0.000, P = 0.000). The mean Musculoskeletal Tumor Society functional scores differed significantly at 27.8 for Type 1 patients, 22.9 for Type 2 patients, and 17.0 for Type 3 patients (P = 0.000). Conclusions This clinical classification can be easily used to evaluate TGCT of all knees prior to surgery or other treatments and can help determine surgical options.

Objectives To describe the technique of the aorta balloon occlusion, and evaluate the blood loss in lumbar spine tumor surgery assisted by aortic balloon occlusion, and to observe the balloon‐related complications. Methods Six patients with lumbar spine tumor underwent resuscitative endovascular balloon occlusion of the aorta prior to tumor resections in our institution between May 2018 to January 2021. Medical records including demographic, diagnosis, tumor location, surgical approach, intraoperative blood loss, surgical duration, and perioperative balloon‐related complication were evaluated retrospectively. Results This series included four males and two females, with a median age of 50 years (range 22 to 69). Of these, three primary tumors were plasmacytoma, giant cell tumor of bone, and osteosarcoma, while recurrence of undifferentiated pleomorphic sarcoma (UPS), recurrence of giant cell tumor of bone (GCT), and metastatic thyroid cancer were diagnosed in cases 1, 6, and 2, respectively. L2 was involved in cases 1 and 5. L3 was involved in case 6. L4 was involved in case 2, 3, and 6. L5 was involved in case 4. One‐stage total en bloc resection surgery (TES) was accomplished in all patients; of this series, signal anterior approach was conducted in case 1, signal posterior approach was utilized in cases 2, 3, and 6, while combined anterior and posterior approach was performed in cases 4 and 5. The median intraoperative blood loss was 1683 mL and ranged from 400 to 3200 mL with a median surgical duration of 442 min and a range from 210 to 810 min. During the perioperative period, no serious balloon‐related complications occurred. Conclusions Endovascular balloon occlusion of the aorta successfully controls intraoperative exsanguination, contributing to a more radical tumor resection and a low rate of tumor cell contamination in lumbar tumor surgery.

Objectives To investigate the contact stress and the contact area o tibial inserts and bushings with respect to different congruency designs in a spherical center axis and rotating bearing hinge knee prosthesis under gait cycle loading conditions using finite element analysis. Methods Nine prostheses with different congruency (different degrees of tibiofemoral conformity and different distances between the spherical center and the bushing) designs were developed with the same femoral and tibial components. The models were transferred to finite element software. The peak contact stresses and contact areas on tibial inserts and bushings under the gait cycle loading conditions were investigated and compared. Results For tibial insert, the peak contact stress was the highest in the low conformity‐long group (61.4486 MPa), and it was 1.88 times higher than that in the group with the lowest stress (moderate conformity‐short group, 32.754 MPa). The contact area was the largest in the low conformity‐long group (420.485 mm2), and it was 1.19 times larger than that in the group with the smallest area (moderate conformity‐middle group, 352.332 mm2). For bushing, the peak contact stress was the highest in the high conformity‐long group (72.8093 MPa), and it was 3.21 times higher than that in the group with the lowest stress (high conformity‐short group, 22.6928 MPa). The contact area was the largest in the low conformity‐short group (2.41 mm2), and it was 2.27 times larger than that in the group with the smallest area (high conformity‐middle group, 1.063 mm2). Conclusion The results of our study showed that the congruency of the tibiofemoral surface and bushing surface should be considered carefully in the design of the spherical center axis and rotating bearing hinge knee prosthesis. Different levels of contact performance were observed with different congruency designs. In addition, the influence of contact stress and contact area on the polyethylene wear of rotating hinge knee prostheses should be confirmed with additional laboratory tests.