Frigg Arno, Frigg Roman, Hintermann Beat, Barg Alexey, Valderrabano Victor
Department of Orthopaedic Surgery, University of Basel, Basel, Switzerland.
Knee Surg Sports Traumatol Arthrosc. 2007 Nov;15(11):1355-62. doi: 10.1007/s00167-007-0372-2. Epub 2007 Jul 13.
Chronic ankle instability (CAI) is a frequent sport orthopaedic entity. Although many risk factors have been studied extensively, little is known how it is influenced by the osseous joint configuration. Based on lateral X-rays, the radius of the talar surface and the tibial coverage of the talus (sector alpha) were measured on a DICOM/PACS system in 52 patients with CAI and an age- and sex-matched control group. The talar radius was found to be larger in patients with CAI (21.2 +/- 2.4 mm) than in the control group (17.7 +/- 1.9 mm; P < 0.0001). The tibio-talar sector was smaller in patients with CAI (80 degrees +/- 5.1 degrees ) than in the control group (88.4 degrees +/- 7.2 degrees ; P < 0.0001). The aim of this study is to analyse the biomechanical influence of the clinical data on stability of the ankle joint. A two-dimensional model of the tibio-talar joint in the sagittal plane was developed. The joint configuration was described by the tibio-talar sector (alpha) and the radius (r) of the talus. The force (F = F (BW) tan alpha/2) and energy (E = F (BW) r [1 - cos alpha/2]) to dislocate the talus out of the tibial plafond were deduced. Ankle stability is a function of the tibio-talar sector: the force necessary to dislocate the joint is decreasing with a smaller sector. The clinical data show that the force needed to dislocate the ankle of CAI patients was 14% weaker than the one needed in the case of healthy subjects (P < 0.0001). The energy to dislocate the ankle depends both on the sector and the radius. The clinical data do not show a significant difference between the energy needed to dislocate the joint of CAI patients and the one of healthy subjects. This is because there is a correlation of a small sector and a large radius for CAI ankles. CAI is associated with an unstable osseous joint configuration, which is characterized by a larger radius of the talus and a smaller tibio-talar sector. The findings of the biomechanical model explain the clinical observations and demonstrate how stability of the ankle joint is influenced by the osseous configuration. Surgical ankle ligament stabilization might be more recommended in patients with an unstable osseous configuration as such patients have a disposition for recurrent sprains. Removing anterior osteophytes for anterior impingement should be done carefully in CAI patients because this would decrease the tibial coverage of the talus and thus dispose the talus to dislocate anteriorly. People who have an unstable ankle configuration and who nevertheless engage in activities with high risk of ankle sprains could be asked to wear ankle protecting sports equipment.
慢性踝关节不稳（CAI）是一种常见的运动骨科疾病。尽管已经对许多风险因素进行了广泛研究，但对于其如何受到骨关节结构的影响却知之甚少。基于踝关节侧位X线片，在DICOM/PACS系统上对52例CAI患者及年龄和性别匹配的对照组测量距骨表面半径和距骨的胫骨覆盖度（α角）。结果发现，CAI患者的距骨半径（21.2±2.4mm）大于对照组（17.7±1.9mm；P<0.0001）。CAI患者的胫距角（80°±5.1°）小于对照组（88.4°±7.2°；P<0.0001）。本研究的目的是分析临床数据对踝关节稳定性的生物力学影响。建立了胫距关节矢状面的二维模型。关节结构由胫距角（α）和距骨半径（r）描述。推导了使距骨脱出胫骨平台所需的力（F = F（体重）tanα/2）和能量（E = F（体重）r[1 - cosα/2]）。踝关节稳定性是胫距角的函数：使关节脱位所需的力随角度减小而降低。临床数据显示，CAI患者使踝关节脱位所需的力比健康受试者弱14%（P<0.0001）。使踝关节脱位的能量既取决于角度，也取决于半径。临床数据显示，CAI患者使关节脱位所需的能量与健康受试者之间无显著差异。这是因为CAI踝关节存在小角度和大半径的相关性。CAI与不稳定的骨关节结构相关，其特征是距骨半径较大和胫距角较小。生物力学模型的研究结果解释了临床观察结果，并证明了踝关节稳定性是如何受到骨结构影响的。对于骨关节结构不稳定的患者，可能更建议进行手术踝关节韧带稳定术，因为这类患者有反复扭伤的倾向。对于CAI患者，在处理前侧撞击而切除前侧骨赘时应谨慎，因为这会减少距骨的胫骨覆盖度，从而使距骨易于向前脱位。对于踝关节结构不稳定但仍从事高踝关节扭伤风险活动的人，可要求其佩戴踝关节保护运动装备。
