Background

Valgus-producing medial opening-wedge proximal tibial osteotomies (V-MOW-PTO) are used to treat isolated medial-compartment knee osteoarthritis in patients with varus malalignment. A fracture of the lateral cortical hinge is a risk factor for poor outcomes. Implantation of a protective K-wire has been suggested to prevent this complication. The primary objective of this bench study was to assess the ability of a protective K-wire to prevent lateral cortical fractures. The secondary objective was to evaluate the influence of the opening speed on fracture risk during the osteotomy.

Hypothesis

The primary hypothesis was that a protective K-wire decreased the risk of hinge fracture. The secondary hypothesis was that this risk was greater when the opening speed was high.

Materials and methods

We performed an experimental study of 20 simulated thermoplastic-polymer (ABS) tibias obtained by 3D printing to assess the effects of wedge-opening speed (high vs. low) and presence of a protective K-wire (yes vs. no). The opening rates were determined in a preliminary study of Sawbone® specimens opened using a distractor. The opening rate was measured using an accelerometer via a motion-capture glove. After assessing several high and low opening speeds, we selected 38 mm/min and 152 mm/min for the study. We divided the 20 ABS specimens into four groups of five each: high speed and K-wire, low speed and K-wire, high speed and no K-wire, and low speed and no K-wire. The force was applied using an Instron™ testing machine until construct failure. The primary outcome measure was the load at failure (N) and the secondary outcome measures were the displacement (mm) and maximum time to failure (s).

Results

At both speeds, values were significantly higher with vs. without a K-wire for load to failure (low: 253.3 N vs. 175.5 N, p < 0.01; high: 262.2 N vs. 154.1 N, p < 0.01), displacement (low: 11.1 mm vs. 8.7 mm, p < 0.01; high: 11 mm vs. 8.9 mm; p = 0.012), and maximal time to failure (low: 11.4 s vs. 8.9 s; p = 0.012; high: 2.2 s vs. 1.8 s; p = 0.011). Thus, the osteotomy opening speed seemed to have no influence on the risk of lateral cortex fracture.

Discussion

Our main hypothesis was confirmed but our secondary hypothesis was refuted: a protective K-wire significantly decreased the risk of hinge fracture, whereas the osteotomy opening speed had no influence. To our knowledge, this is the first published study assessing the potential influence of opening speed on risk of lateral cortex fracture. Our findings were obtained in the laboratory and should be evaluated in clinical practice.

Level of evidence

IV, experimental study.

中文翻译：

---

胫骨外翻截骨术中外侧皮质骨折风险的实验研究

背景

产生外翻的内侧开口楔形胫骨近端截骨术 (V-MOW-PTO) 用于治疗内翻畸形患者的孤立性膝关节内侧间室骨关节炎。外侧皮质铰链骨折是不良预后的危险因素。建议植入保护性克氏针以防止这种并发症。这项工作台研究的主要目的是评估保护性克氏针预防外侧皮质骨折的能力。次要目标是评估开放速度对截骨术中骨折风险的影响。

假设

主要假设是保护性克氏针降低了铰链骨折的风险。第二个假设是，当打开速度高时，这种风险更大。

材料和方法

我们对通过 3D 打印获得的 20 个模拟热塑性聚合物 (ABS) 胫骨进行了实验研究，以评估楔形打开速度（高与低）和保护性克氏针的存在（是与否）的影响。打开率是在使用牵引器打开 Sawbone® 标本的初步研究中确定的。打开率是通过运动捕捉手套使用加速度计测量的。在评估了几种高低开启速度后，我们选择了 38  mm/min 和 152 毫米/分钟的研究。我们将 20 个 ABS 样本分成四组，每组五个：高速和克氏针、低速和克氏针、高速和无克氏针以及低速和无克氏针。使用 Instron TM 测试机施加力，直到结构失效。主要结果指标是失效时的载荷 (N)，次要结果指标是位移 (mm) 和最大失效时间 (s)。

结果

在两种速度下，使用克氏针和不使用克氏针的负载失效值明显更高（低：253.3  N 对比 175.5  N，p  <  0.01；高：262.2  N 对比 154.1  N，p  <  0.01），位移（低：11.1 毫米与 8.7 毫米，p  <  0.01；高：11 毫米与 8.9 毫米；p  =  0.012）和最大故障时间（低：11.4 秒与 8.9 秒；p  =  0.012；高：2.2 秒对比 1.8 秒；p  =  0.011）。因此，截骨开放速度似乎对外侧皮质骨折的风险没有影响。

讨论

我们的主要假设得到证实，但我们的次要假设被驳斥：保护性克氏针显着降低了铰链骨折的风险，而截骨术开放速度没有影响。据我们所知，这是第一项评估打开速度对外侧皮质骨折风险的潜在影响的已发表研究。我们的研究结果是在实验室获得的，应该在临床实践中进行评估。

证据等级

四、实验研究。