Valderrabano Victor, Hintermann Beat, Nigg Benno M, Stefanyshyn Darren, Stergiou Pro
University of Basel, Clinic of Orthopaedic Surgery, Kantonsspital, Basel, Switzerland.
Foot Ankle Int. 2003 Dec;24(12):897-900. doi: 10.1177/107110070302401204.
The purpose of this study was to determine talar movement (e.g., talar rotation and talar shift during (dorsiflexion/plantarflexion) with respect to the tibia in the normal ankle, in the fused ankle, and in the replaced ankle by currently used prosthetic designs.
A 6-df device with an axial load of 200 N and a four-camera high-speed video system were used for the measurement of the range of motion in six fresh-frozen cadaveri leg specimens. While moving the foot through the whole range of motion for plantarflexion/dorsiflexion, segmental motion of the marked bones of the foot and shank were measured dynamically. Rotation and medial-lateral shift of the talus were then calculated with regard to flexion position of the foot.
In the normal ankle, plantarflexion movement was coupled with talar inversion of 3.5 degrees, and dorsiflexion movement with talar eversion of 1.0 degree, in totally accounting for 4.5 degrees of talar rotation. While both the HINTEGRA and the S.T.A.R. prostheses did not show changes to the normal condition during the dorsiflexion/plantarflexion cycle (p < .05), talar rotation had a 60% decrease (p < .05) for the AGILITY prosthesis. In the normal ankle joint, a lateral talar shift of 1.4 mm was found to occur during dorsiflexion, and a lateral talar shift of 5.2 mm during plantarflexion. In both, the HINTEGRA and S.T.A.R. ankles, talar shift was converted into medial direction during dorsiflexion of the foot (difference to normal: p < .05), whereas talar shift in the lateral direction was found to occur during plantarflexion of the foot which was comparable to the normal ankle. The AGILITY ankle evidenced an 80% decrease of talar shift (p < .05) during the whole dorsiflexion/plantarflexion cycle.
The two-component ankle (AGILITY) obviously tends to restrict tremendously talar motion within the ankle mortise, whereas the three-component ankles (HINTEGRA, S.T.A.R.) seem to allow talar range of motion comparable to that in the normal ankle. It is suggested that such a restriction of talar motion results in an increase of stress forces within and around the prosthesis, leading to polyethylene wear and potential loosening at the bone-implant interfaces. Therefore, a successful prosthetic design for the ankle should consist of three components that are shaped as anatomically as possible to provide a normal range of motion and to allow the full transmission of movement transfer between foot and shank and unconstrained movement of the talus within the ankle mortise.
本研究的目的是确定在正常踝关节、融合踝关节以及使用当前假体设计的置换踝关节中，距骨相对于胫骨在（背屈/跖屈）过程中的运动情况（例如距骨旋转和距骨移位）。
使用一个轴向载荷为200 N的6自由度装置和一个四摄像头高速视频系统，对六个新鲜冷冻尸体腿部标本的运动范围进行测量。在使足部进行整个跖屈/背屈运动范围内移动时，动态测量足部和小腿标记骨骼的节段性运动。然后根据足部的屈曲位置计算距骨的旋转和内外侧移位。
在正常踝关节中，跖屈运动伴有距骨内翻3.5度，背屈运动伴有距骨外翻1.0度，距骨总旋转为4.5度。在背屈/跖屈周期中，HINTEGRA和S.T.A.R.假体均未显示出与正常情况的差异（p <.05），而AGILITY假体的距骨旋转减少了60%（p <.05）。在正常踝关节中，背屈时距骨外侧移位1.4 mm，跖屈时距骨外侧移位5.2 mm。在HINTEGRA和S.T.A.R.踝关节中，足部背屈时距骨移位转变为内侧方向（与正常情况的差异：p <.05），而足部跖屈时距骨向外侧移位，这与正常踝关节相当。AGILITY踝关节在整个背屈/跖屈周期中距骨移位减少了80%（p <.05）。
双组件踝关节（AGILITY）明显倾向于极大地限制距骨在踝关节窝内的运动，而三组件踝关节（HINTEGRA、S.T.A.R.)似乎允许距骨的运动范围与正常踝关节相当。有人认为，距骨运动的这种限制会导致假体内部和周围的应力增加，从而导致聚乙烯磨损以及骨-植入物界面处的潜在松动。因此，成功的踝关节假体设计应包括三个尽可能符合解剖形状的组件，以提供正常的运动范围，并允许足部和小腿之间的运动传递完全传递，以及距骨在踝关节窝内不受限制地运动。
