Deformation pattern and load transfer of an uncemented femoral stem with modular necks. An experimental study in human cadaver femurs

BackgroundModular necks in hip arthroplasty allow variations in neck-shaft angles, neck version and neck lengths and have been introduced to improve accuracy when reconstructing the anatomy and hip joint biomechanics. Periprosthetic bone resorption may be a consequence of stress shielding in the proximal femur after implantation of a femoral stem. The purpose of this study was to investigate the deformation pattern and load transfer of an uncemented femoral stem coupled to different modular necks in human cadaver femurs.MethodsA cementless femoral stem was implanted in twelve human cadaver femurs and tested in a hip simulator corresponding to single leg stance and stair climbing activity with patient-specific loading. The stems were tested with four different modular necks; long, short, retro and varus. The long neck was used as reference in statistical comparisons, as it can be considered the “standard” neck. The deformation of bone during loading was measured by strain gauge rosettes at three levels of the proximal femur on the medial, lateral and anterior side.FindingsThe cortical strains were overall reduced on the medial and lateral side of femur, for all implants tested, and in both loading conditions compared to the unoperated femur. Although there were statistical significant differences between the necks, the results did not show a consistent pattern considering which neck retained or lost most strain. In general the differences were small, with the highest significant difference between the necks of 3.23 percentage points.InterpretationThe small differences of strain between the modular necks tested in this study are not expected to influence bone remodeling in the proximal femur.     

2008～2014年北医三院骨科脊柱退行性疾病的住院人群特征分析

目的:探讨人口学特征与脊柱退行性疾病(spinal degenerative diseases,SDD)的相关性,为脊柱退行性疾病的预防和诊疗、降低患病率提供相关依据。方法:根据2008年1月1日~2014年12月31日北京大学第三医院骨科电子病历数据,纳入年龄≥18岁首次手术治疗的脊柱退行性疾病患者。分析其人口学特征(如年龄、性别、职业、出生地、民族以及伴随疾病)与脊柱退行性疾病的相关性,采用描述性统计和卡方检验。结果:共纳入符合标准的SDD患者22951例,男性12838例(55.9%),女性10113例(44.1%)。平均年龄52.4±11.6岁(18~86岁)。其中颈椎退行性疾病(CDD)10941例(47.7%),胸椎退行性疾病(TDD)588例(2.6%),腰椎退行性疾病(LDD)11422例(49.8%);不同部位SDD患者的性别、年龄、职业及地区分布差异均有统计学意义(P0.001),而民族分布差异无统计学意义(P0.05)。在CDD患者中,以男性(55.9%)、50~54岁(18.2%)、办公室人员(22.2%)占比高;在TDD患者中,以男性(57.5%)、农民(26.5%)占比高;在45岁的LDD患者中,男性占比高(χ~2=66.56,P0.001),特别是在18~29岁年龄组中,男性占比明显增高(8.7%∶3.2%);然而,在45岁的LDD患者中,女性占比高(χ~2=17.50,P0.05)。有伴随疾病者8160例,其中伴有骨质疏松(404例)和伴有膝关节炎(210例)的SDD患者以LDD占比最高,分别为86.1%(348/404)和70.0%(147/210);伴有韧带肥厚/骨化(2645例)的SDD患者以CDD占比最高,为79.9%(2114/2645)。伴有高血压及糖尿病的SDD患者占比分别为20.8%(4749/22951)和9.7%(2230/22951)。结论 :SDD有着明显的人口学特征,在不同部位发病的人群特征不同。男性、50~54岁、办公室人员是CDD的高发人群;男性、农民是TDD的高发人群;45岁的男性,特别是18~29岁的男性以及45岁的女性是LDD的高发人群。此外,伴有骨质疏松或伴有膝关节炎是LDD的危险因素,伴有韧带肥厚/骨化是CDD的危险因素。针对上述高危人群进行有重点的干预和宣教可能是降低SDD发病率的重要措施。     

脊髓型颈椎病患者脊髓MRI T2WI高信号的危险因素

目的:探讨脊髓型颈椎病(CSM)患者脊髓MRI T2WI高信号的危险因素。方法 :2014年1月~2014年4月因CSM于我院骨科行手术治疗的185例患者被纳入研究。将脊髓MRI T2WI高信号分为3级:0级,无高信号;1级,T2WI有模糊而边界不清的高信号,且高信号范围局限于一个节段;2级,T2WI有明亮而边界清晰的高信号或高信号范围超过一个节段。在MRI T2WI横断位上测量脊髓压迫程度,在过伸、过屈位X线片上测量颈椎节段和整体活动度。对可能影响高信号的因素(性别、年龄、病程、术前mJOA评分、脊髓压迫程度、颈椎活动度、椎间盘退变程度)行单因素分析,挑选出有意义指标(P0.1)行有序Logistic回归分析。结果:脊髓MRI T2WI高信号的发生率为72.4%。按照分级标准,0级51例(27.6%),1级86例(46.5%),2级48例(25.9%)。性别和脊髓压迫程度对高信号的影响有统计学意义(女性相对于男性的OR=0.366,脊髓压迫比值的OR=0.904,P0.05),而年龄、病程、术前mJOA评分、椎间盘退变程度、颈椎活动度与高信号均无明显相关性(P0.05)。结论:男性、脊髓压迫程度重为CSM患者脊髓MRI T2WI高信号的独立危险因素。     

Effect of repeated freezing–thawing on the Achilles tendon of rabbits

The increased use of allograft tissue in the reconstruction of anterior cruciate ligament has brought more focus to the effect of storage and treatment on allograft. The purpose of this study was to observe the effect of histology and biomechanics on Achilles tendon in rabbits through repeated freezing–thawing before allograft tendon transplantation. Rabbit Achilles tendons were harvested and processed according to the manufacture’s protocol of tissue bank, and freezing–thawing was repeated three times (group 1) and ten times (group 2). Those received only one cycle were used as controls. Then, tendons in each group were selected randomly to make for histological observations and biomechanics test. Histological observation showed that the following changes happened as the number of freezing–thawing increased: the arrangement of tendon bundles and collagen fibrils became disordered until ruptured, cells disrupted and apparent gaps appeared between tendon bundle because the formation of ice crystals. There were significant differences between the experimental and control groups in the values of maximum load, energy of maximum load and maximum stress, whereas no significant differences existed in other values such as stiffness, maximum strain, elastic modulus, and energy density. Therefore, repeated freezing–thawing had histological and biomechanical effect on Achilles tendon in rabbits before allograft tendon transplantation. This indicates that cautions should be taken in the repeated freezing–thawing preparation of allograft tendons in clinical application.     

床旁快速牵引复位在治疗颈椎脱位关节突交锁中的作用

目的探讨床旁快速牵引复位在治疗颈椎关节突脱位交锁中的作用,以期找到快速牵引的适用情况。方法回顾性分析1992年6月～2004年3月颈椎外伤致关节突脱位交锁术前行颅骨牵引快速复位的33例患者的临床资料。双侧关节突脱位交锁21例,单侧关节突交锁12例。常见脱位节段:C4,4 8例、C5,6 15例和C6,7 10例。所有患者均采用床旁颅骨牵引快速复位法,牵引复位成功者均采用颈椎前路间盘切除植骨融合;复位失败者行颈后路切开复位内固定术。结果双侧颈椎关节突脱位交锁者牵引复位成功率为85.7%,单侧颈椎关节突脱位交锁患者牵引复位成功率为16.6%,两组间差异有统计学意义(P<0.01)。23例患者获平均21.6个月(13～36个月)随访。随访病例中植骨融合者均获骨性愈合,颈椎序列良好。结论床旁颅骨快速牵引复位法适用于双侧颈椎关节突脱位交锁患者;双侧关节突脱位交锁患者可先行颅骨快速牵引复位,复位后行颈前路间盘切除植骨融合术;单侧颈椎关节突脱位交锁患者宜行后路切开复位。