Abstract:

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.

Key words: Knee joint, Tibia, Arthroplasty, Diagnostic imaging