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Preparation for Proximal Tibial Cut


- Discussion: 
- telescoping tibial alignment device has proximal platform that conforms to the curved shape of the anterior cortex of the tibia;
- this allows the cutting platform to fit snugly up against the tibial cortex and improve the accuracy of the resection; 
- cylinder of stylus assembly is inserted into its receptable on the alignment platform and adjusted to the appropriate level; 
- because anatomic proximal tibia is generally in 3 deg of Varus & because recommended resection angle is 0 deg, more bone is typically taken from the lateral condyle; 
- tibial stylus is used to determine the exact level of resection; 
- removable stylus protrudes from top of platform and telescopes up & down in 2 mm increments to help MD plan level of resection; 
- measurement off Less Involved (medial) Plateau; 
- Depth of Tibial Cut
- arms of platform are positioned against anterior tibial cortex at level 4-6 mm distal surface of the less involved tibial cortex; 
- upper platform is adjusted so stylus rests in center of condyle; 
- measured off More Involved Plateau; 
- level of 0 is used for resection based on more involved condyle; 
- platform is secured by the large anterior set screw; 
- if resecting to 0 on deficient plateau results in > 10 mm of resection from opposite plateau, deficient side should be augmented w/ bone grafts or modular metal wedge; 
- two pins fix the proximal cutting platform; 
- these two pins can be retained & two additional cutting blocks can be slid onto them to further modify the resection as necessary; 
- these blocks come w/ three stations at 2 mm increments to either incr or decrease the amount of resection; 
- one block is neutral & reproduces initially chosen flex/ext attitude; 
- second cutting block is slanted posteriorly 5 deg (see post slope) & therefore incr post slope applied to previous cut by 5 deg amount; 
- this block is used if trial reduction of the components shows a knee that is stable in extension but too tight in flexion