*Department of Surgery, University of Western Ontario, London, Ontario, Canada; and †Hand and Upper Limb Centre, St Joseph's Health Care London, The University of Western Ontario, London, Ontario, Canada.
J Orthop Trauma. 2014 Jun;28(6):348-53. doi: 10.1097/BOT.0000000000000009.
The effect of radial head implant length on forearm biomechanics is not well understood. This study examined the influence of an increase or a decrease in radial head implant length on forearm load transfer as measured by interosseous membrane (IOM) tension and changes in radiocapitellar joint contact properties.
An upper extremity simulator was used to examine 6 cadaveric specimens with 5 different radial head implant lengths (-4 mm, -2 mm, anatomically correct, +2 mm, and +4 mm). A load-sensing device was woven into the fibers of IOM to quantify its tension. An interpositional pressure measurement sensor was used to determine radiocapitellar joint contact area and pressure. Axial loads of 160 N were applied to the forearm through active pronation and supination with the elbow fixed at 90 degrees of flexion.
Increasing radial head implant length by 4 mm unloaded the IOM in all cases. Decreasing implant length by 4 mm significantly increased the IOM tension (P = 0.005). No significant differences were found in IOM tension between the correct head implant length and the -2 mm implant (P = 0.29). Contact pressure significantly increased with increasing radial head implant length (P = 0.021) and contact area diminished with both an increase and a decrease in radial head implant length, but this was not statistically significant (P = 0.051).
Increasing radial head implant length decreased IOM tension and increased radiocapitellar joint contact pressure.
These findings illustrate the importance of precise restoration of radial length when performing a radial head replacement. If the native radial head length is difficult to accurately assess, avoid increasing the length of the radial head to prevent detrimental changes in the biomechanics of the forearm and the potential for clinically important radiocapitellar joint pathology.
桡骨小头植入物长度对前臂生物力学的影响尚不清楚。本研究通过测试骨间膜（IOM）张力和桡尺骨关节接触特性的变化，来检查增加或减少桡骨小头植入物长度对前臂负荷传递的影响。
使用上肢模拟器检查 6 个尸体标本，其桡骨小头植入物长度分别为-4mm、-2mm、解剖学上正确、+2mm 和+4mm。在 IOM 的纤维中编织了一个负载感应装置来测量其张力。使用中间压力测量传感器确定桡尺骨关节接触面积和压力。通过在 90 度弯曲的肘部固定下主动旋前和旋后，在前臂上施加 160N 的轴向载荷。
增加 4mm 的桡骨小头植入物长度使所有情况下的 IOM 卸载。减少 4mm 的植入物长度会显著增加 IOM 张力（P=0.005）。正确的头植入物长度和-2mm 植入物之间的 IOM 张力没有显著差异（P=0.29）。随着桡骨小头植入物长度的增加，接触压力显著增加（P=0.021），并且随着桡骨小头植入物长度的增加和减少，接触面积减少，但这没有统计学意义（P=0.051）。
增加桡骨小头植入物长度会降低 IOM 张力并增加桡尺骨关节接触压力。
这些发现说明了在进行桡骨小头置换时精确恢复桡骨长度的重要性。如果很难准确评估天然桡骨小头长度，则避免增加桡骨小头的长度，以防止前臂生物力学发生不利变化，并防止出现潜在的具有临床意义的桡尺骨关节病理。
