Meadows Molly, Vuong Brian, Storaci Hunter, Tam Kaysie, Shea Kevin
Stanford University Department of Orthopaedic Surgery, Stanford, CA, USA.
J Pediatr Soc North Am. 2024 Apr 2;7:100036. doi: 10.1016/j.jposna.2024.100036. eCollection 2024 May.
Radial head subluxation, known as pulled elbow or nursemaid's elbow, is a common pediatric condition that occurs when a longitudinal traction force is applied to an extended elbow. The purpose of our study was to demonstrate and quantify the axial traction force required to produce a nursemaid's elbow in a pediatric cadaver specimen and to review the current relevant literature.
We performed a literature search to identify relevant articles describing the nursemaid's elbow injury, as well as relevant biomechanical studies of the radiocapitellar joint. For the biomechanical model, 2 fresh-frozen cadaveric elbows from a single 3-year-old male donor were dissected by a fellowship-trained orthopedic surgeon. An Instron 5,944 testing machine with a 2 kN load cell was used to perform uniaxial testing. The radius and humerus were mounted to the Instron machine and loaded in the axial direction with the elbow in full extension. Loading occurred at a rate of 10 mm/second for 4 seconds, during which the force and actuator displacement were continuously recorded. The local instantaneous load and extension displacement at the time of subluxation were recorded.
The load to failure required to produce the nursemaid's elbow injury in our first specimen was 31 N, with a failure displacement of 4.6 mm. The second specimen demonstrated a load to failure of 26 N, with a failure displacement of 4.6 mm. After subluxation, we reduced the annular ligament from the first specimen. The elbow was then retested and demonstrated a load to failure of 20 N, with a failure displacement of 2.6 mm.
Axial traction applied to a pediatric elbow results in subluxation of the annular ligament into the radiocapitellar joint, at relatively low loads. We demonstrated a mean load to failure in a pediatric cadaveric model of 28.5 N, and a lower load to failure was required to produce a recurrent subluxation in a previously injured specimen.
(1)Radial head subluxation, known as pulled elbow or nursemaid's elbow, is a common pediatric condition that occurs when a longitudinal traction force is applied to an extended elbow.(2)This study is the first to demonstrate and quantify the axial traction force required to produce a nursemaid's elbow in a pediatric cadaver specimen.(3)Axial traction applied to a pediatric cadaver specimen results in subluxation of the annular ligament into the radiocapitellar joint.(4)The mean load to failure is 28.5 N, and a lower load to failure is required to produce a recurrent subluxation in a previously injured specimen.(5)Literature supports that the nursemaid's elbow injury is a result of subluxation of the annular ligament into the radiocapitellar joint, though this may involve a spectrum of injury to the annular ligament itself.
桡骨头半脱位，又称牵拉肘或保姆肘，是一种常见的儿科疾病，当对伸直的肘部施加纵向牵引力时就会发生。我们研究的目的是在儿科尸体标本中演示并量化产生保姆肘所需的轴向牵引力，并回顾当前的相关文献。
我们进行了文献检索，以确定描述保姆肘损伤的相关文章以及桡骨头关节的相关生物力学研究。对于生物力学模型，由一名接受过 fellowship 培训的骨科医生解剖了来自一名 3 岁男性供体的 2 个新鲜冷冻尸体肘部。使用配备 2 kN 测力传感器的 Instron 5944 测试机进行单轴测试。将桡骨和肱骨安装到 Instron 机器上，并在肘部完全伸直的情况下沿轴向加载。以 10 毫米/秒的速率加载 4 秒，在此期间持续记录力和致动器位移。记录半脱位时的局部瞬时载荷和伸展位移。
在我们的第一个标本中产生保姆肘损伤所需的破坏载荷为 31 N，破坏位移为 4.6 毫米。第二个标本的破坏载荷为 26 N，破坏位移为 4.6 毫米。半脱位后，我们从第一个标本中松解了环状韧带。然后对肘部重新进行测试，其破坏载荷为 20 N，破坏位移为 2.6 毫米。
对儿科肘部施加轴向牵引力会导致环状韧带半脱位进入桡骨头关节，且载荷相对较低。我们在儿科尸体模型中证明平均破坏载荷为 28.5 N，并且在先前受伤的标本中产生复发性半脱位所需的破坏载荷更低。
（1）桡骨头半脱位，又称牵拉肘或保姆肘，是一种常见的儿科疾病，当对伸直的肘部施加纵向牵引力时就会发生。（2）本研究首次在儿科尸体标本中演示并量化产生保姆肘所需的轴向牵引力。（3）对儿科尸体标本施加轴向牵引力会导致环状韧带半脱位进入桡骨头关节。（4）平均破坏载荷为 28.5 N，并且在先前受伤的标本中产生复发性半脱位所需的破坏载荷更低。（5）文献支持保姆肘损伤是环状韧带半脱位进入桡骨头关节的结果，尽管这可能涉及环状韧带本身的一系列损伤。
