Hebei Medical University, the Third Affiliated Hospital, Hebei, China.
Clin Orthop Relat Res. 2022 Sep 1;480(9):1804-1814. doi: 10.1097/CORR.0000000000002224. Epub 2022 Apr 29.
It has been reported that trochlear dysplasia occurs very early in development, and environmental factors like swaddling may cause developmental dysplasia of the hip, which is associated with a shallower trochlear groove. However, to our knowledge, there are no definitive studies about the relationship between trochlear dysplasia and traditional straight-leg swaddling.
QUESTIONS/PURPOSES: Using a rat model of femoral trochlear dysplasia, we asked: Does straight-leg swaddling for 1 and 2 weeks in newborn Wistar rats alter the femoral trochlea with respect to (1) gross morphology, (2) histologic appearance, as well as (3) trochlear sulcus angle, width, and depth?
Eighty-four newborn Wistar rats (44 females and 40 males) were divided into two equal groups: 42 in the unswaddled group and 42 in the swaddled group; each group was comprised of 22 females and 20 males. In the swaddled group, the rats were wrapped in surgical tape to maintain hip and knee extension to simulate traditional human straight-leg swaddling. To determine whether longer periods of swaddling were associated with more severe trochlear dysplasia, 21 rats in each group were euthanized at 1 and 2 weeks, respectively, and the gross morphology of the femoral trochlea was observed by one observer blinded to condition. Then hematoxylin and eosin staining of the femoral trochlea was performed and the distribution and number of the chondrocytes of the trochlear groove were viewed through a microscope. The trochlear sulcus angles, depth, and width were measured by an experienced technician blinded to condition.
By observing the gross morphology, we found that the trochlear groove in the swaddled group became qualitatively flatter compared with the unswaddled group at 1 week, and at 2 weeks, the trochlear groove became much shallower. At 1 and 2 weeks, histologic examinations showed obvious qualitative changes in the distribution and number of chondrocytes of the trochlear groove in the swaddled than in the unswaddled groups. In the swaddled group, trochlear dysplasia was more common at 2 weeks, occurring in 62% (26 of 42 [16 of 22 females and 10 of 22 males]) versus 33% (14 of 42 [8 of 22 females and 6 of 20 males]) at 1 week. At 1 week, the swaddled group showed more trochlear dysplasia compared with the unswaddled group as measured by angle of the trochlear groove (137° ± 6° versus 132°± 3.6°, mean difference 5° [95% confidence interval 2.9° to 7.2°]; p < 0.001), depth of the trochlear grove (0.28 ± 0.04 mm versus 0.31 ± 0.02 mm, mean difference 0.03 mm [95% CI 0.01 to 0.04]; p < 0.001). At 2 weeks, the swaddled group showed more severe trochlear dysplasia than at 1 week compared with the unswaddled group as measured by the angle of the trochlear groove (135° ± 6.0° versus 128° ± 4.8°, mean difference 7° [95% CI 5.7° to 10.4°]; p < 0.001), depth of the trochlear grove (0.32 ± 0.04 mm versus 0.36 ± 0.02 mm, mean difference 0.04 mm [95% CI 0.03 to 0.06]; p < 0.001). There was no difference in the width of the trochlear sulcus between the swaddled and the unswaddled groups at 1 week (1.29 ± 0.14 mm versus 1.30 ± 0.12 mm, mean difference 0.01 mm [95% CI -0.05 to 0.07]; p = 0.73) and 2 weeks (1.55 ± 0.12 mm versus 1.56 ± 0.12 mm, mean difference 0.01 mm [95% CI -0.05 to 0.07]; p = 0.70).
Our results indicate that traditional straight-leg swaddling could induce trochlear dysplasia in this model of newborn rats. With an increased swaddling time of 2 weeks, more severe trochlear dysplasia appeared in the swaddled group.
Our findings suggest that traditional straight-leg swaddling may impair trochlear development in the human neonate and lead to trochlear dysplasia in infants. We believe our animal model will be useful in future work to observe and study the change of cartilage and subchondral bone in each stage of the development of trochlear dysplasia and the change of mechanotransduction-associated proteins (such as, TRPV4/ Piezo1 and CollagenⅡ) in cartilage and subchondral osteocytes. It will also be helpful to further investigate the mechanism of developmental femoral trochlea dysplasia caused by biomechanical changes.
据报道，滑车发育不良在发育早期就已出现，环境因素如襁褓包裹可能导致发育性髋关节发育不良，其与较浅的滑车沟有关。然而，据我们所知，尚无关于滑车发育不良与传统直腿襁褓之间关系的明确研究。
问题/目的：我们使用股骨滑车发育不良的大鼠模型，提出以下问题：在新生 Wistar 大鼠中，直腿襁褓 1 周和 2 周是否会改变股骨滑车，分别在（1）大体形态、（2）组织学外观以及（3）滑车沟角、宽度和深度方面？
将 84 只新生 Wistar 大鼠（44 只雌性和 40 只雄性）分为两组，每组 42 只，分别为未包裹组和包裹组；每组又分为 22 只雌性和 20 只雄性。在包裹组中，用手术胶带包裹大鼠，保持髋关节和膝关节伸展，模拟传统的人类直腿襁褓。为了确定更长时间的襁褓包裹是否与更严重的滑车发育不良有关，每组中的 21 只大鼠分别在 1 周和 2 周时安乐死，然后由一名观察者对股骨滑车的大体形态进行观察。然后对股骨滑车进行苏木精-伊红染色，并通过显微镜观察滑车沟的软骨细胞分布和数量。由一名经验丰富的技术员对滑车沟角、深度和宽度进行测量，技术员对包裹条件不知情。
通过观察大体形态，我们发现包裹组的滑车沟在 1 周时比未包裹组变得更平坦，在 2 周时变得更浅。在 1 周和 2 周时，组织学检查显示滑车沟中软骨细胞的分布和数量明显存在定性变化。在包裹组中，2 周时滑车发育不良更为常见，发生率为 62%（42 只中的 26 只[22 只雌性中的 16 只和 22 只雄性中的 10 只]），而 1 周时为 33%（42 只中的 14 只[22 只雌性中的 8 只和 20 只雄性中的 6 只]）。在 1 周时，与未包裹组相比，包裹组的滑车沟角（137°±6°比 132°±3.6°，平均差异 5°[95%置信区间 2.9°至 7.2°]；p<0.001）、滑车沟深度（0.28±0.04mm 比 0.31±0.02mm，平均差异 0.03mm[95%置信区间 0.01mm 至 0.04mm]；p<0.001）的滑车发育不良更为常见。在 2 周时，与未包裹组相比，包裹组的滑车沟角（135°±6.0°比 128°±4.8°，平均差异 7°[95%置信区间 5.7°至 10.4°]；p<0.001）、滑车沟深度（0.32±0.04mm 比 0.36±0.02mm，平均差异 0.04mm[95%置信区间 0.03mm 至 0.06mm]；p<0.001）的滑车发育不良更为严重。在 1 周时（1.29±0.14mm 比 1.30±0.12mm，平均差异 0.01mm[95%置信区间 -0.05mm 至 0.07mm]；p=0.73）和 2 周时（1.55±0.12mm 比 1.56±0.12mm，平均差异 0.01mm[95%置信区间 -0.05mm 至 0.07mm]；p=0.70），包裹组和未包裹组之间的滑车沟宽度无差异。
我们的结果表明，传统的直腿襁褓可能会在这种新生大鼠模型中引起滑车发育不良。随着襁褓包裹时间增加到 2 周，包裹组出现更严重的滑车发育不良。
我们的发现表明，传统的直腿襁褓可能会损害人类新生儿的滑车发育，并导致婴儿的滑车发育不良。我们相信，我们的动物模型将有助于未来的工作，观察和研究滑车发育不良各个阶段的软骨和软骨下骨的变化，以及软骨细胞中机械转导相关蛋白（如 TRPV4/Piezo1 和 CollagenⅡ）的变化。这也将有助于进一步研究由生物力学变化引起的发育性股骨滑车发育不良的机制。
