Scholarlink

Background <p>Accurate femoral component rotation is essential for optimal outcomes in total knee arthroplasty (TKA), yet reliable intraoperative assessment remains challenging. The “grand piano sign” has been described as a qualitative visual cue, but its quantitative clinical value has not been clearly established. This study aimed to evaluate the diagnostic performance of the grand piano ratio as an intraoperative tool for detecting excessive femoral component external rotation using advanced postoperative imaging as a reference standard.</p> Methods <p>A retrospective analysis was conducted on 170 knees undergoing primary TKA. The intraoperative grand piano ratio was measured after completion of all femoral resections and before trial component implantation using the anterior femoral resection surface. Postoperative femoral component rotation was assessed using MAVRIC-sequence magnetic resonance imaging referenced to the surgical transepicondylar axis (sTEA). Excessive femoral component external rotation was defined as postoperative external rotation greater than 3° relative to the sTEA reference. Receiver operating characteristic (ROC) analysis was performed to evaluate diagnostic performance of the grand piano ratio and determine the optimal cutoff value, while multivariable logistic regression analysis was used to identify independent predictors of excessive external rotation.</p> Results <p>Excessive femoral component external rotation (&gt; 3°) was identified in 39 of 170 knees (22.9%). The mean grand piano ratio was significantly lower in knees with external rotation compared to those without (0.41 vs. 0.54, <i>p</i> &lt; 0.001). The grand piano ratio demonstrated moderate discriminative ability for detecting femoral component external rotation greater than 3° (AUC = 0.74, 95% CI 0.65–0.83). The optimal cutoff value was 0.44, yielding a sensitivity of 71.8% and a specificity of 74.0%. In multivariable analysis, the grand piano ratio was the only independent predictor of malrotation (<i>p</i> &lt; 0.001). At the identified threshold, the negative predictive value reached 89.9%, suggesting that excessive external rotation was unlikely when the grand piano ratio exceeded the proposed cutoff.</p> Conclusion <p>The grand piano ratio may serve as a simple and readily available adjunctive intraoperative screening parameter for identifying excessive femoral component external rotation in TKA. A threshold value of 0.44 demonstrated a high negative predictive value and may assist surgeons in intraoperative decision-making. However, the ratio should be considered a complementary assessment tool rather than a definitive method for determining femoral component rotation. The grand piano ratio should be viewed as a complementary intraoperative assessment tool rather than an alternative to navigation or robotic-assisted techniques.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

The grand piano ratio: an adjunctive intraoperative screening tool for detecting excessive femoral component external rotation in total knee arthroplasty

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年7月7日

查看全文
  • Özgür Avci,
  • Alpaslan Öztürk,
  • Burak Olcay Güler,
  • Hünkar Çağdaş Bayrak,
  • Ali Ömer Kaya,
  • Yakup Doğan

摘要

Background

Accurate femoral component rotation is essential for optimal outcomes in total knee arthroplasty (TKA), yet reliable intraoperative assessment remains challenging. The “grand piano sign” has been described as a qualitative visual cue, but its quantitative clinical value has not been clearly established. This study aimed to evaluate the diagnostic performance of the grand piano ratio as an intraoperative tool for detecting excessive femoral component external rotation using advanced postoperative imaging as a reference standard.

Methods

A retrospective analysis was conducted on 170 knees undergoing primary TKA. The intraoperative grand piano ratio was measured after completion of all femoral resections and before trial component implantation using the anterior femoral resection surface. Postoperative femoral component rotation was assessed using MAVRIC-sequence magnetic resonance imaging referenced to the surgical transepicondylar axis (sTEA). Excessive femoral component external rotation was defined as postoperative external rotation greater than 3° relative to the sTEA reference. Receiver operating characteristic (ROC) analysis was performed to evaluate diagnostic performance of the grand piano ratio and determine the optimal cutoff value, while multivariable logistic regression analysis was used to identify independent predictors of excessive external rotation.

Results

Excessive femoral component external rotation (> 3°) was identified in 39 of 170 knees (22.9%). The mean grand piano ratio was significantly lower in knees with external rotation compared to those without (0.41 vs. 0.54, p < 0.001). The grand piano ratio demonstrated moderate discriminative ability for detecting femoral component external rotation greater than 3° (AUC = 0.74, 95% CI 0.65–0.83). The optimal cutoff value was 0.44, yielding a sensitivity of 71.8% and a specificity of 74.0%. In multivariable analysis, the grand piano ratio was the only independent predictor of malrotation (p < 0.001). At the identified threshold, the negative predictive value reached 89.9%, suggesting that excessive external rotation was unlikely when the grand piano ratio exceeded the proposed cutoff.

Conclusion

The grand piano ratio may serve as a simple and readily available adjunctive intraoperative screening parameter for identifying excessive femoral component external rotation in TKA. A threshold value of 0.44 demonstrated a high negative predictive value and may assist surgeons in intraoperative decision-making. However, the ratio should be considered a complementary assessment tool rather than a definitive method for determining femoral component rotation. The grand piano ratio should be viewed as a complementary intraoperative assessment tool rather than an alternative to navigation or robotic-assisted techniques.