Conventional navigation and extension gap first technique for proper bone cuts in TKA

Background: Achieving optimal component alignment and soft tissue balance remains a primary challenge in total knee arthroplasty (TKA). Traditional techniques rely either on bony landmarks (measured resection) or soft tissue tension (gap balancing), both of which present specific limitations regarding femoral component rotation and joint line maintenance.

Objective: This study describes a "conventional navigation" protocol and an "extension gap first" technique to optimize bone resection and ligamentous balancing without computerized assistance. The study evaluates the clinical efficacy of this combined approach in 100 consecutive primary TKA cases.

Key Points: Preoperative planning utilized full-leg weight-bearing radiographs to determine the mechanical distal lateral femoral angle (LDFA) and medial proximal tibial angle (MPTA). Intraoperatively, distal femoral and proximal tibial cuts were verified using calipers and extramedullary rods. The "extension gap first" concept involved balancing the extension space through standardized soft tissue releases before determining femoral rotation. Axial femoral positioning integrated both the surgical transepicondylar axis and a flexion spacer to ensure gap symmetry. Results indicated that 94% of patients achieved frontal alignment within 3° of the neutral mechanical axis. The average femoral external rotation was 3.2° in varus knees and 5.1° in valgus knees. No cases required lateral retinacular release, and intraoperative trials confirmed balanced flexion and extension gaps in all patients.

Conclusion: The integration of conventional navigation and the extension gap first technique provides a reproducible framework for achieving precise component positioning. By combining bony landmarks with soft tissue assessment, this method identifies outliers and minimizes rotational malalignment, offering a cost-effective alternative to computer-assisted surgery.