下肢力线（下肢机械轴）的问题

冠状面、矢状面上下肢力线问题是一个很复杂的问题。

膝关节中心

踝关节中心

胫骨机械轴及胫骨平台后倾角

TSAA in the sagittal plane was created by the use of two points.One point wasobtained by projecting the middle of the medial intercondylar eminence upon theside of the medial plateau, in a lateral view (A in Fig. 2a). The second point was the middle of the medialmalleolus measured at its most distal end (B in Fig. 2a).

Fig. 2. Method used to measure the posterior slope. (a)Shows the points A and B that create the tibial shaft anatomical axis (TSAA);white line in figure, when the device was placed in a true anterior toposterior position in the sagittal plane. (b) Shows a closer view of how theposterior slope was obtained.(Johannes J. de Boer , LeendertBlankevoort , Idsart Kingma?etc.In vitro study ofinter-individual variation in posterior slope in the knee joint?[J].Clinical Biomechanics?,2009,24:448-492.)


取胫骨棘中点稍外侧及距骨中点连线为小腿机械轴。


Thesagittal plane does not have an equivalent to the MA of the coronal planebecause the load bearing line changes instantly with the degree of flexion^[5], andsome investigators defined the sagittal MA in their own ways with noverification of its validity?^[16,18]. Oswald et al?^[16]defined the MA of tibia in sagittal plane as the line between the intersectionof the plane of the tibial plateau and a line running through the midpoints ofthe outer shaft diameter at distances of 10 and 20 cm from the tibial plateau, and the midpoint of thewidth of the tibiotalar joint. Denis et al?^[18]?defined the MAof the tibia in sagittal plane as the line connecting the midpoint of the planeof the tibial plateau and the midpoint of the talus. In the current study, wedefined the sagittal MA as the line connecting the midpoints of the medialtibia plateau and the tibia plafond in the sagittal plane, which is similar tothat of the study by Denis et al?^[18]. We found several advantageswith the use of this definition for the sagittal MA. It can avoid the effectsof intervening bone deformity because the overall orientation of the entire boneis reflected. It can be used as a standard to compare other anatomicalreferences as in this study. It is in accordance with the definition of thecoronal MA^[5], but this study does not convey the data revealingits mechanical significance.Future studies are warranted to elucidate itsmechanical significance.?(JaeHo Yoo, MD,Chong Bum Chang, MD, PhD,Kwang Sook Shin, MS, et al.?Anatomical References to Assess the Posterior Tibial Slope in Total KneeArthroplasty: A Comparison of 5 Anatomical Axes?[J].J Arthroplasty,2008,23(4): 586-592. )

Allmeasurements were carried out by a trained investigator (one of the authors, K.S. S.). In the measurements, a true lateral radiograph of the lower legcovering the whole length of the tibia was used. The measurements were donewith the use of a working software of PACS (picture archiving and communicationsystem) (Impax, Agfa, Antwerp, Belgium). The sagittal MA of thetibia was defined as the line connecting the midpoints of the medial tibiaplateau and the tibia plafond. Five anatomical references wereidentified: the anterior cortical line (ACL) of tibia, the proximal anatomicalaxis (PAA), the central anatomical axis (CAA), the posterior cortical line(PCL) of proximal tibia, and the fibular shaft axis (FSA) (Fig. 1).Definitionfor each anatomical reference was made as following: ACL, the lineconnecting the 2 points on the anterior cortex of the proximal tibia at 5 and 15 cm distalto the knee joint line; PAA, the lineconnecting midpoints of outer cortical diameter at 5 and 15cm distal to the knee joint; CAA, the line connecting midpoints of outer cortical diameterat 10 cm distal to theknee joint and 10 cmproximal to the ankle joint; PCL, the lineconnecting the 2 points on the posterior cortex of the tibia at 5 and 15 cm distalto the knee joint; and FSA, the lineconnecting midpoints of outer cortical diameter of proximal and distal ends ofthe fibular diaphysis.

(Jae Ho Yoo, MD,Chong BumChang, MD, PhD,Kwang Sook Shin, MS, et al.?AnatomicalReferences to Assess the Posterior Tibial Slope in Total Knee Arthroplasty: AComparison of 5 Anatomical Axes[J].J Arthroplasty,2008, 23(4): 586-592. )

Theaccuracy of the mechanical axis of the tibia was influenced by the accuracy inthe selection of the anatomical landmarks during registration process (ie, thecenter of the proximal tibia, the medial and the lateral malleolus)^[25]?and the methods of determiningthe center of the ankle joint?^[26].?(W.P. Yau, MBBS, FRCSE, FHKCOS, K.Y. Chiu, MBBS, FRCSE, FHKCOS,and W.M. Tang,MBBS, FRCSE, FHKCOS.How Precise is the Determination of Rotational Alignment ofthe Femoral Prosthesis in Total Knee Arthroplasty,An In Vivo Study. The Journalof Arthroplasty, 2007, 22( 7):1042-1048)

The anatomical axis most parallel to the sagittal MA was the PAA (meanangle between the sagittal MA, ?0.2°)，PAA, the line connectingmidpoints of outer cortical diameter at 5 and 15cm distal to the knee joint?(Jae Ho Yoo, MD,Chong Bum Chang, MD, PhD,Kwang SookShin, MS, et al.?AnatomicalReferences to Assess the Posterior Tibial Slope in Total Knee Arthroplasty: AComparison of 5 Anatomical Axes[J].J Arthroplasty,2008, 23(4): 586-592. )

在侧位X线片上，采用3种不同的测量方法来获取胫骨平台后倾角（PS）。首先制定3条不同的参考线，在膝关节平面以下15cm水平处和胫骨结节下5cm水平处分别取其与胫骨前侧皮质、胫骨干轴线、胫骨后侧皮质的交点，依次连接上下两点，就得到了胫骨中上段前侧骨皮质切线、胫骨中上段轴线和胫骨中上段后侧骨皮质切线。而内外侧胫骨平台前后缘连线与这些参考线的垂线之间的夹角就分别构成了内外侧胫骨平台后倾角。由于胫骨平台内外侧的后倾角不同，所以经测量每张侧位片可获得6个数值不同的后倾角度数（图2）。