X-ray based morphological analysis of the knee - a review

Mismatch between the patient’s knee morphology and the implant geometry is linked to poorer clinical outcome after total knee arthroplasty (TKA). Hence, patients whose knee morphology differs strongly from the norm may have a higher risk to be dissatisfied after surgery. Consequently, a preoperative risk assessment regarding differences between individual knee morphology and implant geometry is favorable. For adequate availability and limited radiation dose, this should be based on standard imaging in TKA, being conventional radiographs.We reviewed morphological measures of the knee to be evaluated on X-ray images. Only measures of the articulating areas, without connections to pathologies such as patellar instability or pain, were included. In addition, the accuracy of 2D-3D knee reconstruction was reviewed, in order to assess the potential use for 3D X-ray based analysis.Various parameter definitions for the evaluation on anterior-posterior and lateral X-rays exist in the literature. If given, the inter- and intraobserver reliability can be interpreted as moderate to excellent. Several authors have reported on 2D-3D reconstruction accuracies with maximum absolute errors of ~5-6 mm for in vitro studies.Mismatch between the bone morphology implant geometry can partly be assessed in 2D, using single X-rays. Methods for 2D-3D reconstruction demonstrated potential for enabling 3D X ray-based analyses. However, improvements regarding accuracy and larger in vivo validation studies are pending.A basic preoperative risk assessment using X-rays is possible. Future steps could include the automation of the parameter derivation and an enhancement of 2D-3D reconstruction for enabling a more comprehensive assessment.