Roentgen stereophotogrammetry in high tibial osteotomy for gonarthrosis.

In three cases operated with high tibial osteotomy for medial gonarthrosis the exact method of roentgen stereophotogrammetry with tantalum balls as bone markers (Selvik 1974) was used to study angular and translational movement in three dimensions at the operation and during the healing period. Tibial osteotomy caused angular and translational movements even in planes where correction was not intended, and the stereo technique revealed that stability was not present when knee mobilisation started. Correlation between the stereo values and conventional radiographic measurements were best in the frontal plane (root mean square value of discrepancies 1.3 degrees). Roentgen stereophotogrammetry gives superior information compared with the conventional radiographic technique, but it is concluded that the latter has sufficient accuracy for the clinical assessment of corrections in the frontal plane.