Huebschmann Nathan A, Katzman Jonathan L, Robin Joseph X, Meftah Morteza, Rozell Joshua C, Schwarzkopf Ran
Department of Orthopedic Surgery, New York University Langone Health, New York, NY.
J Bone Joint Surg Am. 2025 Apr 4;107(12):1362-1370. doi: 10.2106/JBJS.24.01226.
High body mass index (BMI) is a risk factor for tibial baseplate loosening following total knee arthroplasty (TKA) but may not adequately correlate with stresses at the tibial baseplate. In this study, we aimed to determine an optimal cutoff of a weight-to-tibial baseplate surface-area ratio (weight/SA) for predicting aseptic tibial baseplate loosening. We further examined whether tibial stem extensions have a protective effect.
We identified 16,368 patients who underwent primary, elective TKA from June 2011 to March 2023. Patient demographics, including age, sex, and race, implants used, and revision surgeries were extracted. Revisions were manually reviewed to confirm revision indications. The exact surface areas of tibial baseplates were obtained from manufacturers. Receiver operating characteristic (ROC) analysis of patients without tibial stem extensions was utilized to examine the utility of BMI and weight/SA for predicting aseptic tibial baseplate loosening. Optimal weight/SA and BMI cutoffs for predicting loosening were determined. The effect of tibial stem extensions on loosening was then examined in patients at or above (n = 7,698; 3.7% with stem extension) and below (n = 8,670; 1.3% with stem extension) the determined weight/SA cutoff.
There were 16,368 patients in the final sample (median age, 67 years; 68.9% female; 54.1% White). Weight/SA (area under the curve [AUC] = 0.653; p < 0.001) was a better predictor of aseptic tibial baseplate loosening requiring revision compared with patient BMI (AUC = 0.624; p < 0.001). The optimal weight/SA cutoff for predicting loosening was 0.0162 kg/mm 2 (sensitivity = 0.747, specificity = 0.537). Multivariable logistic regression demonstrated that being at or above the weight/SA cutoff (odds ratio [OR] = 3.17; p < 0.001) but not the BMI cutoff (p = 0.911) was a significant predictor of revision for tibial baseplate loosening in patients without stem extensions. No cases of revision for aseptic tibial baseplate loosening in patients with stem extensions occurred either at or above or below the cutoff. The rate of revision for aseptic tibial baseplate loosening in patients without stem extensions was 0.3% for patients below and 1.0% for patients at or above the weight/SA cutoff.
The ratio of weight-to-tibial baseplate surface area was more predictive of revision for aseptic tibial baseplate loosening following TKA compared with BMI alone. For patients with obesity with small tibial baseplate sizes, utilization of a tibial stem extension may protect against tibial loosening.
Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.
高体重指数（BMI）是全膝关节置换术（TKA）后胫骨基板松动的危险因素，但可能与胫骨基板处的应力没有充分关联。在本研究中，我们旨在确定体重与胫骨基板表面积比（体重/SA）的最佳截断值，以预测无菌性胫骨基板松动。我们还进一步研究了胫骨柄延长是否具有保护作用。
我们确定了2011年6月至2023年3月期间接受初次择期TKA的16368例患者。提取患者的人口统计学信息，包括年龄、性别和种族、使用的植入物以及翻修手术情况。对翻修病例进行人工审核以确认翻修指征。胫骨基板的确切表面积从制造商处获取。对没有胫骨柄延长的患者进行受试者操作特征（ROC）分析，以检验BMI和体重/SA对预测无菌性胫骨基板松动的效用。确定预测松动的最佳体重/SA和BMI截断值。然后在体重/SA截断值及以上（n = 7698；3.7% 有柄延长）和以下（n = 8670；1.3% 有柄延长）的患者中研究胫骨柄延长对松动的影响。
最终样本中有16368例患者（中位年龄为67岁；68.9% 为女性；54.1% 为白人）。与患者BMI（曲线下面积[AUC] = 0.624；p < 0.001）相比，体重/SA（AUC = 0.653；p < 0.001）是预测需要翻修的无菌性胫骨基板松动的更好指标。预测松动的最佳体重/SA截断值为0.0162 kg/mm²（敏感性 = 0.747，特异性 = 0.537）。多变量逻辑回归表明，体重/SA截断值及以上（比值比[OR] = 3.17；p < 0.001）而非BMI截断值（p = 0.911）是没有柄延长的患者胫骨基板松动翻修的显著预测因素。在截断值及以上或以下，有柄延长的患者均未发生无菌性胫骨基板松动翻修病例。没有柄延长的患者中，体重/SA截断值以下的无菌性胫骨基板松动翻修率为0.3%，截断值及以上的为1.0%。
与单独的BMI相比，体重与胫骨基板表面积之比对TKA后无菌性胫骨基板松动翻修的预测性更强。对于胫骨基板尺寸小的肥胖患者，使用胫骨柄延长可能预防胫骨松动。
预后III级。有关证据水平的完整描述，请参阅作者须知。
