Institute of Human Anatomy, Department of Neurosciences, University of Padova, Padova, Italy.
Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy.
J Anat. 2019 Jul;235(1):80-87. doi: 10.1111/joa.12995. Epub 2019 Apr 4.
The infrapatellar fat pad (IFP) is an intracapsular but extrasynovial structure, located between the patellar tendon, the femoral condyles and the tibial plateau. It consists of white adipose tissue, organised in lobules defined by thin connective septa. The aim of this study is the morphometric and ultrasonographic analysis of IFP in subjects without knee pathology during flexion-extension movements. The morphometric study was conducted on 20 cadavers (15M, 5F, mean age 80.2 years). Ultrasound was performed on 24 volunteers with no history of knee diseases (5M, 19F, mean age: 45 years). The characteristics of the adipose lobules near the patellar tendon and in the deep portion of the IFP were evaluated. Numerical models were provided, according to the size of the lobules. At histological examination, the adipose lobules located near the patellar tendon were larger (mean area 12.2 mm ± 5.3) than those at a deeper level (mean area 1.34 mm ± 0.7, P < 0.001) and the thickness of the septa of the deepest adipose lobules (mean value 0.35 mm ± 0.32) was greater than that of the superficial one (mean value 0.29 mm ± 0.25, P < 0.001). At ultrasound, the IFP was seen to be composed of very large lobules in the superficial part (mean area 0.29 cm ± 0.17 in extension), with a significant reduction in flexion (mean area 0.12 cm ± 0.07, P < 0.01). The deep lobules were smaller (mean area 0.11 cm ± 0.08 in extension) and did not change their values (mean area 0.19 cm ± 0.52 in flexion, P > 0.05). In the sagittal plane, the reduction of thickness of the superficial layer (with large adipose lobules) during flexion was 20.6%, whereas that of the deep layer (with small adipose lobules) was 1.3%. Numerical simulation of vertical loads, corresponding to flexion of the knee, showed that stress mainly developed within the interlobular septa and opposed bulging of the lobules. The characteristics of the lobular arrangement of the IFP (large lobules with superficial septa in the superficial part and small lobules with thick septa in the deep one), significant changes in the areas and perimeters of the superficial lobules, and the reduced thickness of the superficial layer during flexion all indicate the dynamic role played by the IFP in knee kinematics.
髌下脂肪垫（IFP）是一种位于髌腱、股骨髁和胫骨平台之间的囊内但关节外结构。它由白色脂肪组织组成，组织成由薄的结缔组织隔定义的小叶。本研究的目的是在膝关节无病理的情况下，对 IFP 在屈伸运动中的形态和超声分析。形态学研究在 20 具尸体（15 名男性，5 名女性，平均年龄 80.2 岁）上进行。对 24 名无膝关节疾病史的志愿者（5 名男性，19 名女性，平均年龄：45 岁）进行了超声检查。评估了靠近髌腱和 IFP 深部的脂肪小叶的特征。根据小叶的大小提供了数值模型。组织学检查显示，靠近髌腱的脂肪小叶较大（平均面积 12.2mm ± 5.3），比深部的脂肪小叶大（平均面积 1.34mm ± 0.7，P < 0.001），深部脂肪小叶的隔厚度（平均值 0.35mm ± 0.32）大于浅层的隔厚度（平均值 0.29mm ± 0.25，P < 0.001）。在超声检查中，IFP 被观察到在浅层由非常大的小叶组成（伸展时平均面积为 0.29cm ± 0.17），在弯曲时显著减少（平均面积为 0.12cm ± 0.07，P < 0.01）。深层小叶较小（伸展时平均面积为 0.11cm ± 0.08），其值无变化（弯曲时平均面积为 0.19cm ± 0.52，P > 0.05）。在矢状面，弯曲时浅层（大脂肪小叶）厚度减少 20.6%，而深层（小脂肪小叶）厚度减少 1.3%。对应于膝关节弯曲的垂直载荷的数值模拟表明，应力主要在小叶间隔内发展，并与小叶的隆起相对抗。IFP 小叶排列的特征（浅层的大隔和深层的厚隔中的小小叶）、浅层小叶的面积和周长的显著变化以及弯曲时浅层厚度的减少，都表明 IFP 在膝关节运动学中发挥了动态作用。
