The "midsulcus line" as a landmark for tibial resection during total knee arthroplasty

Background: Proper tibial alignment is an important goal of total knee arthroplasty. Most surgeons agree that tibial coronal alignment should be within three degrees of neutral mechanical alignment. The "midsulcus line" is a line drawn along the sulcus of the tibial spines, and then the line is continued in the sagittal plane and extended onto the anterior tibia where it intersects the tibial tubercle approximately 3 to 4 mm lateral to the tubercle's medial border. The tibial cut was then made perpendicular to this line. The aim of our study was to assess, using CT scans, whether this line provided a consistent guide for planning the tibial cut in total knee arthroplasty. Methods: We reviewed the CT scans of the knees of 107 patients with osteoarthritis who had undergone a CT scan for planning of custom cutting guides. The midsulcus line was drawn on all scans. Results: We found that in 105 of 107 knees, a perpendicular cut to this tibial landmark would have delivered a cut surface within three degrees of neutral mechanical alignment. Conclusions: The midsulcus line is a reliable landmark for planning the tibial resection in total knee arthroplasty. Level of Evidence: III.