Adjusted mechanical alignment to achieve a well-balanced knee with less soft tissue releases: Surgical tips and tricks for a modified “extension gap first technique” in TKA

Background: Traditional mechanical alignment in total knee arthroplasty aims for a neutral limb axis to ensure implant longevity, yet approximately 20% of patients report functional dissatisfaction. This has prompted interest in alternative alignment philosophies, such as adjusted mechanical alignment, which prioritize patient-specific anatomy and soft tissue tension over systematic neutral targets.

Objective: This article describes a surgical technique for adjusted mechanical alignment using a modified extension gap-first approach and a guided-motion total knee system to improve functional outcomes in varus osteoarthritis.

Key Points: The technique utilizes preoperative long-leg radiographs to differentiate between osteoarthritic and constitutional varus. Intraoperatively, an adjustable distal femoral cutting block allows for a maximum of 2.5° additional medial varus to balance the extension gap, reducing the need for extensive medial soft tissue releases. Femoral rotation is determined by soft tissue tension using a quantitative laminar tensioner, with bony landmarks serving as secondary controls. Clinical data from 600 patients demonstrated a mean postoperative hip-knee-ankle angle of -2.9° ± 2.1°, indicating a deliberate residual varus. A randomized trial of 75 patients showed that this adjusted approach yielded significantly higher Knee Society Scores (178.5 vs. 162.4) and Forgotten Joint Scores (78.2 vs. 64.1) at 24-month follow-up compared to traditional mechanical alignment.

Conclusion: Adjusted mechanical alignment combined with gap balancing effectively restores knee function and improves patient satisfaction scores. By allowing conservative deviations from a neutral axis, surgeons can achieve symmetrical ligament tension while maintaining safe implant alignment parameters.