Department of Orthopaedic Surgery, Tokyo Medical University Ibaraki Medical Center, 3-20-1 Chuo Ami, Inashiki, Ibaraki, 300-0395, Japan.
Department of Rehabilitation, Tokyo Medical University Ibaraki Medical Center, Ami, Ibaraki, 300-0395, Japan.
J Orthop Surg Res. 2019 Jun 27;14(1):195. doi: 10.1186/s13018-019-1237-3.
Diagnosing distal radioulnar joint (DRUJ) instability remains a challenge as it relies on physical examination. To quantitatively assess DRUJ stability, a pressure-monitor ultrasound system was developed. The objective of this study was to evaluate the force-displacement relationship of DRUJ in normal subjects.
Nine wrists of 9 asymptomatic volunteers were evaluated. The pressure-monitor ultrasound system was developed to apply pressure to the tissue with a pre-determined cycle and displacement of the transducer. Each subject was imaged sitting with the elbow flexed and forearm pronated. The dorsal surface of the distal radius and the center of the ulnar head were displayed at DRUJ level. The pressure toward palmar direction was applied to the distal ulna with different levels of transducer displacements, i.e., 1 mm, 2 mm, and 3 mm. The distance between the dorsal surface of the ulnar head and the dorsal surface of the distal radius was measured. The first measurement was performed at the initial position, and the second measurement was performed when the transducer pressed down the ulna to the degree that the ulnar head had shifted to the most palmar position. At the same time, the pressure to the transducer was measured. The changes of radioulnar distance (=the measurement at the most palmar position-the measurement at the initial position) and pressure, and pressure/distance ratio were compared among the different transducer displacements.
The pressure was significantly increased as the transducer displacement became larger (P < 0.01). The changes of radioulnar distance were smaller in the 1 mm displacement condition compared to the 2 and 3 mm displacement conditions (P < 0.05). The pressure/distance ratio was larger in the 1 mm displacement condition compared to the 2 and 3 mm displacement conditions (P < 0.05).
A method to assess DRUJ stability by measuring changes in radioulnar distance and force application was developed. It was found that the application of 2 mm displacement and 200 g force was the critical stress for the capsuloligamentous structures to start stabilizing DRUJ. This methodology and the indices may be clinically useful to investigate the mechanical properties of patients with DRUJ instability.
诊断远端桡尺关节（DRUJ）不稳定仍然是一个挑战，因为它依赖于体格检查。为了定量评估 DRUJ 的稳定性，开发了一种压力监测超声系统。本研究的目的是评估正常受试者 DRUJ 的力-位移关系。
评估了 9 名无症状志愿者的 9 个腕关节。压力监测超声系统用于以预定的周期和换能器的位移向组织施加压力。每位受试者均在肘部弯曲和前臂旋前的坐姿下进行成像。在 DRUJ 水平上显示桡骨远端的背侧表面和尺骨头的中心。向尺骨的掌侧方向施加不同程度的换能器位移（即 1mm、2mm 和 3mm）的压力。测量尺骨头背侧表面和桡骨远端背侧表面之间的距离。第一次测量在初始位置进行，第二次测量在换能器向下按压尺骨，使尺骨头向最掌侧位置移动的程度进行。同时，测量对换能器的压力。比较不同换能器位移时桡尺距离的变化（=最掌侧位置的测量值-初始位置的测量值）和压力、压力/距离比。
随着换能器位移的增加，压力显著增加（P<0.01）。1mm 位移条件下桡尺距离的变化明显小于 2mm 和 3mm 位移条件（P<0.05）。1mm 位移条件下的压力/距离比明显大于 2mm 和 3mm 位移条件（P<0.05）。
开发了一种通过测量桡尺距离变化和施加力来评估 DRUJ 稳定性的方法。发现应用 2mm 位移和 200g 力是使囊韧带结构开始稳定 DRUJ 的临界应力。该方法和指标可能对研究 DRUJ 不稳定患者的机械特性具有临床意义。
