Histological and histochemical skin changes in insulin-dependent diabetic patients with and without limited joint mobility

Summary We studied 24 skin biopsies of the hand in 24 IDDM patients followed at the National Institute of Endocrinology (NIE). Biopsies of 7 healthy individuals were used as controls. The diabetics were divided into two groups, with limited joint mobility (LJM) and without LJM. We compared the different structural components of the skin, and their changes; we used quantitative, semi-quantitative and qualitative methods. We found that patients with LJM had a greater levelling, less rete pegs and dermal papillae (p<0.05), increased alteration of the mucopolysaccharides distribution (p<0.005), higher frequency of alterations of the elastic fibers (p<0.05) and collagen (p<0.005), vessel enlargement (p<0.025) acquiring cord shape, and reduction of the vessel lumen (p<0.005) in comparison with patients without LJM and controls. This could be a consequence of the chronic hyperglycemia from childhood that affects the structure, architecture and function of collagen fibers. Genetic and immunologic studies could help to elucidate the mechanisms of this alteration.     

单髁膝关节置换胫骨元件不同固定柱形状的有限元分析

目的针对单髁膝关节置换后胫骨前内侧疼痛、胫骨元件松动以及对侧关节炎恶化的问题,通过有限元方法比较分析胫骨元件固定柱的不同几何形状对胫骨应力分布的影响。方法建立有效的单髁膝关节置换有限元模型,对胫骨元件固定柱的形状进行设计。在相同的加载条件下,分别对双柱形、单脊形、双脊形和十字星形胫骨元件进行有限元分析,并与完整膝关节模型进行对比,评估胫骨元件固定柱不同形状设计对胫骨前内侧皮质骨应力、胫骨截骨面松质骨应力、胫骨对侧软骨应力的影响。结果单髁置换后胫骨前内侧皮质骨应力峰值均增大。与完整膝关节相比,在双柱形、单脊形、双脊形和十字星形胫骨元件固定柱的模型中,胫骨前内侧皮质骨应力峰值分别增加56.1%、55.9%、54.5%和68.4%。单脊形和双脊形胫骨元件松质骨截骨面应力峰值比完整胫骨分别减小8.1%和15.6%,而双柱形和十字星形则分别增大67.9%和121.5%,超过松质骨的疲劳屈服应力。双柱形、单脊形、双脊形和十字星形胫骨固定柱对应的胫骨对侧软骨应力峰值相比于完整胫骨分别减小42.1%、26.6%、24.2%和28.5%。结论单髁膝关节置换改变了胫骨内外侧的载荷分布,使置换侧承受更大的载荷。单脊形和双脊形胫骨元件在降低胫骨前内侧皮质骨和截骨面松质骨应力方面效果更好,其中单脊形胫骨元件更接近完整膝关节胫骨的应力分布。研究结果可为设计更符合膝关节力学性能的单髁膝关节假体提供理论依据。     

Micromotion of Cementless Tibial Baseplates: Keels with Adjuvant Pegs Offer More Stability Than Pegs Alone

Initial implant stability is crucial to cementless knee arthroplasty fixation. The objective of this study was to evaluate the stability of two baseplates with different fixation features: a monoblock porous tantalum baseplate featuring two hexagonal pegs alone, and a modular design featuring a keel with four adjuvant cruciform pegs. A physiologically relevant test method previously described was used to evaluate compression and liftoff of the baseplates during stair descent. The porous tantalum baseplate with dual-hex peg fixation experienced greater rocking motions and liftoff compared to the baseplate with a keel and adjuvant pegs. Liftoff and displacement motion is likely deleterious and may inhibit biological fixation due to the physical separation of the baseplate from the bone.     

纤维桩核修复牙体大面积缺损的临床疗效观察

目的：观察纤维桩核加烤瓷冠或金属桩核加烤瓷冠修复牙体大面积缺损的临床疗效。方法：将228颗经过完善根管治疗的牙体大面积缺损的患牙随机分为两组,实验组109颗植入纤维桩后行烤瓷冠修复,对照组119颗植入成品自攻金属桩钉后行烤瓷冠修复。经18个月随访,通过X线牙片和临床检查以成功和失败作为判断标准,统计分析结果。结果：实验组108颗修复体及基牙完好,成功率99．1％;对照组112颗修复体及基牙完好,成功率94．1％。结论：目前运用纤维桩进行残根残冠修复,操作快捷方便并具有良好的生物相容性,可作为牙体大面积缺损的主要修复手段。     

Micromotion of cementless tibial baseplates under physiological loading conditions

Initial implant stability is crucial to cementless knee arthroplasty success. The objective of this study was to develop a physiological relevant methodology that incorporates torsion, shear, and compression forces to evaluate two tibial component designs that feature either a keel or cylindrical porous metal pegs. The data were compared with a simplified compression loading scenario. Results show a loading profile that combines compressive, shear, and torsional loads results in significantly larger motions than occur when loading in compression only. When comparing between a keeled and a pegged device, the new method shows significant differences in tibial component subsidence/liftoff at the anterior and posterior locations, which were lacking in the simplified test model. To accurately assess implant stability, studies should use physiological relevant loading.