Review of the anatomical and radiological differences between fluoroscopic and non-fluoroscopic positioning of osteoarthritic knees.

Objective: To determine the differences in the radioanatomical appearance of the tibiofemoral compartment in knees radiographed in the fluoroscopic semiflexed, semiflexed MTP and fixed flexion methods compared to that obtained in the extended knee position. To assess the differences in the radiological procedures between the fluoroscopic and nonfluoroscopic semiflexed methods of radiography.

Methods: Based on anatomical principals to describe the differences in (1) the content of the joint space in knees radiographed in the extended and semiflexed positions and (2) the sectional plane for joint space width (JSW) measurement in radiographs of knees positioned in the extended, fluoroscopic guided semiflexed, MTP and fixed flexion positions. From published procedures to determine the factors that affect study costs, X-ray technologists operating time and film processing in fluoroscopic and nonfluoroscopic methods of radiography.

Results: Medial compartment JSW from semiflexed methods only accurately measures cartilage thickness. All semiflexed methods reproducibly reposition the joint within any one patient. The angle at the tibiofemoral joint varies little between patients in the fluoroscopic semiflexed, less in the MTP and more so in the fixed flexion positions; the latter is due to the effect weight-associated differences in thigh girth. The sectional plane of JSW measurement is generally similar within the three views. Compared to the fluoroscopic method the radiological procedures of the nonfluoroscopic techniques were less demanding.

Conclusion: The MTP and fixed flexion methods are much easier to use than the fluoroscopic method. They reproducibly reposition the knee within patient knees and between knees in the MTP but less so in the fixed flexion view.