A novel “Precision technique” for preoperative planning of posterior tibial slope correction osteotomy

Identification of posterior tibial slope (PTS) and slope correction osteotomies have lately gained importance in various knee surgeries. The preferred surgical methods have been a flexion (opening)/extension (closing) wedge osteotomy at the proximal tibia. Current methods of PTS measurements use the anterior tibial cortical line (ATL), posterior tibial cortical line (PTL), or the anatomical axis of tibia (AAT) on a short lateral view X-ray of the tibia. This can have a high inter and intra-observer variability. Measuring the PTS using the “mechanical axis” has potentially less inter and intra-observer error. However, simply using the difference between pre-operative and planned post-operative PTS measures as the osteotomy correction angle (OCA), with the reference line as “mechanical axis” gives erroneous correction. A novel “Precision technique” is devised to calculate the OCA with least errors using the “mechanical axis” as the reference line. This technique minimizes errors in pre-operative planning. This can further translate into better clinical results due to a reduction in pre-operative planning errors. The principles of this technique can also be used to plan other osteotomies for angular corrections of long bones where the joint line/slope/alignment is to be corrected with reference to the mechanical axis.