Campbell David G, Johnson Luke J, West Simon C
Wakefield Orthopaedic Clinic, Adelaide, SA, Australia.
ANZ J Surg. 2006 Sep;76(9):782-7. doi: 10.1111/j.1445-2197.2006.03867.x.
Unicompartmental knee arthroplasty is a popular alternative to total knee replacement in selected patients. Component alignment has not yet been described by computer-assisted tomography (CAT) imaging techniques; these have been developed for total knee arthroplasty analysis. The aims of this study were to report two new technologies; a new unicompartmental knee arthroplasty system was radiographically assessed with a new CAT scan protocol.
In a consecutive cohort study, 60 knees were analysed by the 'UniCAT Protocol'. Patients were implanted with a unicompartmental knee arthroplasty system that uses a unique ligament tensor for femoral component alignment. The uniCAT protocol requires a long anteroposterior and lateral scout scan to measure limb alignment and component orientation. A spiral computer-assisted tomography at the knee is used to measure component rotation. The total scan time was 20 s with a calculated unshielded radiation dose of 1 mSv or less.
The mechanical axis had a mean of 2.7 degrees varus. Femoral components were implanted with a mean of 0.37 degrees valgus and 1.3 degrees flexion. Tibial components were implanted with a mean 3.47 degrees varus and 5.1 degrees posterior slope. Femoral components were externally rotated a mean of 3.36 degrees, tibial components were externally rotated 6.59 degrees from the posterior tibia and 5.68 degrees from the transepicondylar axis.
The UniCAT protocol uses less radiation than whole-limb spiral scans and is a method that can be used with all modern computer-assisted tomography machines. The coronal and sagital alignment results compare favourably with previous published reports without computer-assisted tomography. Component rotation has not previously been reported and its implications are yet to be defined.
单髁膝关节置换术是部分患者全膝关节置换术的常用替代方案。计算机断层扫描（CAT）成像技术尚未用于描述组件对齐情况；这些技术是为全膝关节置换术分析而开发的。本研究的目的是报告两项新技术；采用一种新的CAT扫描方案对一种新型单髁膝关节置换系统进行影像学评估。
在一项连续队列研究中，采用“UniCAT方案”对60个膝关节进行分析。患者植入了一种单髁膝关节置换系统，该系统使用独特的韧带张量进行股骨组件对齐。UniCAT方案需要进行长轴前后位和侧位定位扫描以测量肢体对齐和组件方向。使用膝关节螺旋计算机断层扫描测量组件旋转。总扫描时间为20秒，计算得出的无屏蔽辐射剂量为1毫希沃特或更低。
机械轴平均内翻2.7度。股骨组件植入时平均外翻0.37度、屈曲1.3度。胫骨组件植入时平均内翻3.47度、后倾5.1度。股骨组件平均向外旋转3.36度，胫骨组件相对于胫骨后侧平均向外旋转6.59度，相对于髁间轴向外旋转5.68度。
UniCAT方案的辐射量低于全肢体螺旋扫描，是一种可与所有现代计算机断层扫描机器配合使用的方法。冠状面和矢状面的对齐结果与之前未使用计算机断层扫描的已发表报告相比更优。此前尚未报道过组件旋转情况，其影响尚待确定。
