CD4+ T cell-mediated rejection of major histocompatibility complex class I-disparate grafts: A role for alloantibody

Experimental studies of the T cell requirement for rejection of class I major histocompatibility complex (MHC)-disparate grafts have generated controversy over both the autonomy of CD8⁺ T cells and the mechanism whereby CD4⁺ T cells are able to independently mediate rejection. In this study of rejection of RT1A^a class I MHC-disparate rat cardiac and skin allografts by high-responder PVG RT1^u recipients, we show that elimination of CD8⁺ T cells [by anti-CD8 monoclonal antibody (mAb) administration in vivo] fails to prolong graft survival, whereas partial depletion of CD4⁺ T cells (by anti-CD4 mAb treatment) markedly delays rejection of class I-disparate heart grafts, and marginally prolongs survival of skin grafts. Anti-CD4-treated PVG-RT1^u athymic nude rats reconstituted with CD8⁺ T cells failed to reject class I-disparate skin grafts for several weeks and eventual rejection correlated with re-emergence of a small number of donor derived CD4⁺ T cells. Conversely, anti-CD8-treated nude rats reconstituted with CD4⁺ T cells alone rapidly rejected class I-disparate skin grafts. Passive transfer of anti-class I immune serum to anti-CD4-treated euthymic recipients promptly restored their ability to specifically reject a class I-disparate heart graft. Similarly, passive transfer of immune serum to PVG-RT1^u nude rats bearing skin allografts caused destruction of class I-disparate but not third-party grafts. These results demonstrate that CD4⁺ T cells are both necessary and sufficient to cause rejection of class I-disparate heart and skin grafts in this model and that CD4⁺ T cell-dependent alloantibody plays a decisive role in effecting rejection.     

皮质骨圈在椎弓根钉固定系统中支撑作用的生物力学评价

目的：了解脊椎椎弓根钉固定系统在人体皮质骨圈（allograft fusion cage,AFC)植入椎间隙前后对脊柱稳定性的影响。方法：在8具新鲜成年猪离体腰椎标上，以L2－3，L3－R，L4－5节段为实验对象，测试各节段在正常状态下（正常组）、椎间盘切除并Steffee钢板固定（内固定组）、椎间盘切除AFC植入Steffee钢板固定（AFC组）等三种种状态下的轴向压缩刚度。结果：（1）内固定组节段轴向压缩刚度为正常组的14．0％；（2）AFC组节段的轴向压缩刚度明显增加，达到了正常椎间的轴向压缩刚度；（3）在相同轴向压缩载荷作用下，AFC给椎弓根钉受力移位较内固定组明显减小。结论：脊椎椎弓根钉固定系统在AFC椎间植入后，对脊椎稳定性较无AFC植入显著增强，其受力移位明显减小，即可显著减少临床断钉。钢板折弯的机会。     

桡侧腕短伸肌腱部分移位修复第一腕掌关节脱位的应用解剖与手术设计

目的:为桡侧腕短伸肌腱部分移位修复第一腕掌关节脱位提供解剖学依据。方法:30侧成人上肢标本,将桡侧腕短伸肌腱分为上、中、下3部分,进行形态学测量。结果:桡侧腕短伸肌腱长度为(15.3±1.9)cm(10～22.5cm),其宽度:上段为(15.4±5.2)mm(5.3～23.8mm),中段(10.0±3.0)mm(4.2～18.5mm),下段(5.5±0.6)mm(3.7～9.6mm);厚度:上段为(0.6±0.3)mm(0.1～1.4mm),中段为(1.8±0.7)mm(0.7～3.0mm),下段为(2.1±1.2)mm(0.8～3.1mm)。结论:桡侧腕短伸肌腱部分转位有足够的长度以修复第一腕掌关节脱位。     

Inhibition of Smad3 promotes the healing of rotator cuff injury in a rat model

To investigate the effect of inhibiting transforming growth factor‐β (TGF‐β1)/Smad2/3 signaling on rotator cuff (RC) healing. A bilateral supraspinatus tendon detachment‐repair model of Sprague‐Dawley (SD) rats was utilized. A total of 120 SD rats were randomly assigned to six groups and each group received the subacromial injection of normal saline, empty vectors, or lentiviral vectors containing small interfering RNA against TGF‐β1, Smad2, Smad3 at the bone‐tendon junction. Biomechanical and histological analyses were performed to evaluate bone‐tendon junction healing quality at 8 weeks after repair. Histologically, scar healing was found in all surgical groups. Animals with inhibited Smad3 exhibited better bone‐tendon junction structures with higher density, parallel orientation, and collagen fiber continuity than other surgical group animals. Immunohistochemistry revealed that the protein expression level of collagen I in animals with inhibited Smad3 was more prominent compared with all other surgical groups. Biomechanically, Animals with inhibited Smad3 showed better results in the maximum load at 4, 6, and 8 weeks after surgery compared with other surgical groups. Besides, C3H10T1/2 (Smad3?) cells increased TT‐D6 cell migration and tendon‐associated genes expression (scleraxis, tenascin C, collagen I) in coculture system. We conclude that inhibition of Smad3 promotes RC tendon healing in the rat supraspinatus model.     

Simultaneous bilateral versus unilateral tibial tubercle fractures

PurposeTibial tubercle/tuberosity fractures are rare injuries in young patients accounting for less than one percent of physeal fractures. Bilateral simultaneous fractures are even rarer, with only a few case reports in literature. The purpose of our study was to describe the largest case series of bilateral simultaneous tibial tuberosity avulsion fractures and compare it with unilateral fractures. We also wanted to compare our bilateral fractures case series with all the cases reported in the last 65 years.MethodsIRB approved retrospective study involving patients under age 18 years with tibial tuberosity avulsion fractures. Bilateral simultaneous fractures were compared to a unilateral group including demographic data, mechanism of injury, clinical exam findings, complication rates, and outcomes including return to function. Statistical analysis was performed using Mann-Whitney and Fisher Exact tests to compare the different groups.Results138 patients (131 males, 7 females) from a tertiary children’s hospital between 2012 and 2019 with tibial tuberosity avulsion fractures were included. 11 bilateral simultaneous fractures (BL Group) were identified and compared to age matched cohort from the 127 unilateral fracture patients (UL group). There was no significant difference found in BMI, height, weight, age, sex, mechanism of injury, return to functional range of motion, and return to sports between the groups. 7/11 (63%) of the patients in the BL group who sustained simultaneous fractures had to be home bound and could not attend school for an average of 8.3 weeks. There was a higher rate of complications in the BL group (63.3%) compared to the UL group (21.1%), which was statistically significant. The most common complications in the bilateral group were hardware removal and wound dehiscence.ConclusionThis first case series comparing unilateral versus bilateral simultaneous tibial tuberosity avulsion fractures suggests that the final outcomes of the two groups are similar, however it shows a significantly higher complication rate and hardware removal rate in the BL group. This study is also the first to highlight the significant initial morbidity in the BL fracture group with issues with regards to early mobility and loss of school-days. Keeping in mind the profound initial impact the bilateral injury poses to the patient; surgeons can possibly plan for rigid fixation for early mobilization to better prepare bilateral fracture patients for the early post-operative recovery process.     

Elbow reconstruction after excision of proximal ulna tumors: Challenges and solutions

Most malignant bone tumors are treated with surgical excision, adhering to oncologic principles, followed by reconstruction to preserve form and function whenever feasible. Primary bone tumors around the elbow are rare accounting for <1% of all skeletal tumors. They pose a reconstructive challenge, due to the complex interplay between the osseous & capsulo-ligamentous structures which is essential for elbow stability and function. Tumors affecting the proximal ulna are rare and reconstruction of the defects following these tumors is extremely challenging. Various reconstruction options like arthrodesis, autogenous bone grafts, allografts, re-implantation of sterilized tumor bone, pseudoarthrosis, and endoprosthesis have been tried with variable success. However, due to lack of standardization and the rarity of the site, surgeons are often in a dilemma to choose the correct option. This can lead to suboptimal functional outcomes and long-term failures. In this article, we reviewed the published literature on proximal ulnar tumors and noted the pros and cons of various reconstructive procedures. We have also attempted to formulate reconstruction recommendations based on the level of resection of proximal ulna.