胫骨平台后倾角的测量及其在全膝关节置换术中的意义

Measurement of posterior tibial slope and its significance in total knee arthroplasty

胫骨平台后倾角(PTS)是全膝关节置换术(TKA)中重要的参数。临床上测量PTS的方法主要包括:X线、CT、MRI。X线测量PTS需选择合适的参考轴,常用的参考轴包括:胫骨近端解剖轴、胫骨骨干解剖轴、腓骨骨干纵轴、胫骨中上段前侧骨皮质延长线、胫骨后侧骨皮质延长线,不同参考轴具有各自的优缺点。X线测量PTS简单便捷,但受到投照角度的影响且不能分别测量内外侧平台。CT、MRI可使用三维重建技术测量PTS,不受投照角度的影响且可以分别测量内外侧平台。MRI还可以测量包含软骨、半月板的PTS。TKA术中,PTS可影响膝关节的屈曲度、稳定性和周围韧带的张力。PTS的增加可通过后滚机制、松弛韧带增加膝关节屈曲度。然而,PTS的增加也会造成韧带松弛、胫骨假体前向碰撞,从而导致膝关节的不稳定,进而导致假体的磨损。TKA术中,PTS的增加还可以有效减少后交叉韧带的张力,但会因手术截骨增加后交叉韧带损伤的风险。另外,PTS的增加还可以通过增加力矩的方式,减少伸膝时股四头肌腱的张力。值得注意的是,胫骨截骨参考、股骨后髁偏心距也会影响PTS的临床作用。目前,关于PTS的研究主要基于欧洲人群。PTS在亚洲人群中的测量和临床意义,有待进一步的探索。

Posterior tibial slope(PTS)is an important parameter in total knee arthroplasty(TKA).Clinicians can use X-ray,CT and MRI to measure PTS.When using X-ray,clinicians need to select a suitable reference axis.The available reference axes include:tibial proximal anatomic axis,tibial shaft anatomic axis,fibular shaft axis,anterior tibial cortex,posterior tibial cortex.Different reference axes have their own advantages and disadvantages.The X-ray measurement of PTS is affected by the projection angle,and cannot measure the lateral posterior tibial slope and the medial posterior tibial slopeseparately.CT and MRI can measure PTS by using 3D reconstruction techniques,which is not influenced by the projection angle and can measure the lateral and medial tibial slope separately.MRI can also measure PTS containing cartilage and meniscus.In TKA,PTS can affect the range of motion,stability and ligaments’tension of the knee through a variety of mechanisms.Increasing of PTS can effectively increase postoperative flexion through the roll-back mechanism and relaxation of the ligament.However,increasing of PTS will also cause relaxation of the ligament and anterior impingement of the tibial prosthesis,which results in instability of the knee and wear of the prosthesis.Furthermore,increasing of PTS can significantly reduce the tension of the posterior cruciate ligament,but increase the risk of posterior cruciate ligament injury due to osteotomy.In addition,increasing of PTS can reduce the tension of the quadriceps tendon in extension by increasing the torque.It is worth noting that clinical affects of PTS is influenced by different osteotomy references and the femoral condyle.At present,the researches on PTS are mostly based on European population.The measurement and clinical significance of PTS in Asian population need further exploration.