AO Research Institute Davos, Davos, Switzerland; Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Münster, Germany.
AO Research Institute Davos, Davos, Switzerland.
Acta Orthop. 2024 Jun 14;95:290-297. doi: 10.2340/17453674.2024.40841.
Recommendations regarding fragment-size-dependent screw fixation trajectory for coronal plane fractures of the posterior femoral condyles (Hoffa fractures) are lacking. The aim of this study was to compare the biomechanical properties of anteroposterior (AP) and crossed posteroanterior (PA) screw fixations across differently sized Hoffa fractures on human cadaveric femora.
4 different sizes of lateral Hoffa fractures (n = 12 x 4) were created in 48 distal human femora according to the Letenneur classification: (i) type I, (ii) type IIa, (ii) type IIb, and (iv) type IIc. Based on bone mineral density (BMD), specimens were assigned to the 4 fracture clusters and each cluster was further assigned to fixation with either AP (n = 6) or crossed PA screws (n = 6) to ensure homogeneity of BMD values and comparability between the different test conditions. All specimens were biomechanically tested under progressively increasing cyclic loading until failure, capturing the interfragmentary movements via motion tracking.
For Letenneur type I fractures, kilocycles to failure (mean difference [∆] 2.1, 95% confidence interval [CI] -1.3 to 5.5), failure load (∆ 105 N, CI -83 to 293), axial displacement (∆ 0.3 mm, CI -0.8 to 1.3), and fragment rotation (∆ 0.5°, CI -3.2 to 2.1) over 5.0 kilocycles did not differ significantly between the 2 screw trajectories. For each separate subtype of Letenneur type II fractures, fixation with crossed PA screws resulted in significantly higher kilocycles to failure (∆ 6.7, CI 3.3-10.1 to ∆ 8.9, CI 5.5-12.3) and failure load (∆ 275 N, CI 87-463 to ∆ 438, CI 250-626), as well as, less axial displacement from 3.0 kilocycles onwards (∆ 0.4°, CI 0.03-0.7 to ∆ 0.5°, CI 0.01-0.9) compared with AP screw fixation.
Irrespective of the size of Letenneur type II fractures, crossed PA screw fixation provided greater biomechanical stability than AP-configured screws, whereas both screw fixation techniques demonstrated comparable biomechanical competence for Letenneur type I fractures. Fragment-size-dependent treatment strategies might be helpful to determine not only the screw configuration but also the surgical approach.
对于后股骨髁冠状面骨折（Hoffa 骨折）的片段大小依赖性螺钉固定轨迹，尚无相关建议。本研究的目的是比较不同大小 Hoffa 骨折在人体股骨标本上采用前后位（AP）和交叉前后位（PA）螺钉固定的生物力学特性。
根据 Letenneur 分类，在 48 个人体股骨远端创建了 4 种不同大小的外侧 Hoffa 骨折（n = 12 x 4）：（i）I 型，（ii）IIa 型，（ii）IIb 型和（iv）IIc 型。根据骨密度（BMD），将标本分为 4 个骨折簇，每个簇进一步分为 AP（n = 6）或交叉 PA 螺钉固定（n = 6），以确保 BMD 值的均匀性和不同测试条件之间的可比性。所有标本均在逐渐增加的循环载荷下进行生物力学测试，直至失效，并通过运动跟踪捕捉界面间的运动。
对于 Letenneur I 型骨折，在 5.0 千循环中，失效时的千循环数（平均差异 [∆] 2.1，95%置信区间 [CI] -1.3 至 5.5）、失效载荷（∆ 105 N，CI -83 至 293）、轴向位移（∆ 0.3 mm，CI -0.8 至 1.3）和片段旋转（∆ 0.5°，CI -3.2 至 2.1）在 2 种螺钉轨迹之间无显著差异。对于每个单独的 Letenneur II 型骨折亚型，交叉 PA 螺钉固定的失效时的千循环数（∆ 6.7，CI 3.3-10.1 至 ∆ 8.9，CI 5.5-12.3）和失效载荷（∆ 275 N，CI 87-463 至 ∆ 438，CI 250-626）更高，从 3.0 千循环开始，轴向位移也更小（∆ 0.4°，CI 0.03-0.7 至 ∆ 0.5°，CI 0.01-0.9），与 AP 螺钉固定相比。
无论 Letenneur II 型骨折的大小如何，交叉 PA 螺钉固定的生物力学稳定性均优于 AP 配置螺钉，而两种螺钉固定技术在 Letenneur I 型骨折中均表现出相似的生物力学能力。基于片段大小的治疗策略可能有助于确定不仅是螺钉配置，还有手术入路。
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