Objective:

To evaluate the relationship between the intraoperative grand piano ratio in patients undergoing primary TKA and the postoperative femoral component rotation measured using sTEA, and to assess its diagnostic performance in identifying excessive femoral component external rotation greater than 3°.

Approach:

• Study Design: Retrospective diagnostic accuracy and correlation analysis conducted at a tertiary-level arthroplasty center.
• Patient Selection: Patients who underwent primary TKA for primary gonarthrosis between January 2018 and December 2022 were evaluated, excluding those with valgus deformity or significant femoral deformity.
• Surgical Technique: All surgeries were performed using a standard medial parapatellar approach without robotic assistance or navigation systems.
• Measurement of Grand Piano Ratio: The grand piano ratio was measured after femoral resections by calculating the height of the medial anterior cortex divided by the lateral anterior cortex.
• Postoperative Assessment: Postoperative femoral component rotation was assessed using MAVRIC MRI with sTEA as the reference.

Key Findings:

• The grand piano ratio demonstrated a significant correlation with postoperative femoral component rotation as measured by sTEA-referenced MAVRIC MRI.
• The study aimed to validate the grand piano ratio as a reliable intraoperative tool for assessing femoral component rotation in primary TKA.

Interpretation:

Limitations:

• The study was retrospective and conducted at a single center, which may limit generalizability.
• Exclusion of patients with valgus deformity may affect the applicability of findings.

Conclusion:

The grand piano ratio was evaluated for its role in achieving optimal femoral component alignment during TKA.