2025 ISAKOS Biennial Congress ePoster
Effect Of Tibia-First Gap-Balancing Technique On Gap Width Changes And Component Positioning In Robotic-Arm Assisted Total Knee Arthroplasty
Hong Yeol Yang, MD, PhD, Hwasun KOREA, REPUBLIC OF
Jong-Keun Seon, MD, PhD, Prof, Gwangju, Jeonnam KOREA, REPUBLIC OF
Sung Ju Kang, MD, Hwasun, Chonnam KOREA, REPUBLIC OF
Chonnam National University Hospital, Hwasun, KOREA, REPUBLIC OF
FDA Status Not Applicable
Summary
Tibia-first gap-balancing technique achieved balancing goals in 98% of cases, despite varying gap increments observed between initial assessments and subsequent bone resections.
ePosters will be available shortly before Congress
Abstract
Purpose
Achieving coronal plane balance in total knee arthroplasty (TKA) is essential. Concerns regarding pre-resection balancing potentially leading to asymmetrical gap alterations post-resection have been raised. This study aims to quantitatively assess the predictability of post-resection gap dimensions and the attainment of balanced gaps using robotic-arm assisted TKA.
Methods
This retrospective cohort study included 100 consecutive patients who underwent robotic-arm assisted TKA for varus knee osteoarthritis employing a tibia-based functional alignment (FA) technique from January to July 2023. Tibial cuts were performed according to preoperative tibial anatomy within a predefined boundaries, and femoral cuts were adjusted based on tensioned soft tissues to achieve balanced lateral and medial gaps in both extension and flexion. The primary outcome was the proportion of balanced gaps, defined as differential laxities of ≤ 2 mm, across extension, flexion, lateral, and medial gap measurements. Ligament balancing in lateral and medial compartments was assessed using a robotic system at 10° and 90° flexion to evaluate if FA facilitated a balanced knee. Secondary outcomes included implant alignment, resection depth, and patient-reported outcome measures (PROMs).
Results
Significant increases in both lateral and medial gaps at 10° and 90° flexion were observed following tibial and femoral bone cuts (p < 0.001). The increments in gap widths were inconsistent, and post hoc analysis indicated a more pronounced effect of bone cutting on the medial flexion gap than on other gaps, suggesting asymmetrical gap changes (P < 0.01). Nevertheless, tibia-based FA achieved overall balance in 98% of all gap measurements. The tibial component was placed at an average of 2.1° varus, while the femoral component was positioned at 0.3° varus and 1.3° external rotation relative to the surgical transepicondylar axis. All measured depths of bone resections post-resection were significantly reduced compared to initial assessments. Significant improvements in PROMs were also noted between preoperative and one-year postoperative evaluations (all P < 0.05).
Conclusions
Tibia-first gap-balancing technique achieved balancing goals in 98% of cases, despite varying gap increments observed between initial assessments and subsequent bone resections.