Second Department of Orthopedics, Wangjing Hospital of China Academy of Chinese Medical Sciences, Beijing, China.
Third Department of Orthopedics, Wangjing Hospital of China Academy of Chinese Medical Sciences, Beijing, China.
BMC Musculoskelet Disord. 2024 Aug 31;25(1):686. doi: 10.1186/s12891-024-07802-6.
Previous studies have reported that positive buttress is as effective as anatomical reduction in treating young femoral neck fractures, but whether this effect is related to the Pauwels classification remains unclear. The purpose of this study was to retrospectively analyze the clinical prognosis of positive buttress in young femoral neck fractures with different Pauwels classifications, as well as to assess its biomechanical properties.
A total of 170 young patients with femoral neck fractures who were treated with three cannulated screws were included in this study. Patients were divided into three groups based on their preoperative Pauwels classification. Each group was divided into three subgroups based on the reduction quality: positive buttress, negative buttress and anatomical reduction. The femoral neck shortening, the incidence of necrosis of the femoral head (AVN) and the Harris hip scores at the last follow-up were compared across the three reduction quality within each Pauwels classification. Subsequently, a volunteer was recruited, CT data of the hip was obtained, and finite element models representing different reduction quality under varying Pauwels classifications were established. The biomechanical properties of each model were then evaluated following the application of strains.
In Pauwels type I, there were no significant differences in postoperative femoral neck shortening, incidence of AVN, or Harris score among the three types of reduction quality (P > 0.05). However, positive buttress provided superior biomechanical stability compared to negative buttress and anatomical reduction. In Pauwels type II, the incidence of AVN was similar between the positive buttress and the anatomical reduction groups, and both were significantly lower than that in the negative buttress (P < 0.05). The Harris score of the positive buttress was higher than that of the negative buttress, and there was no significant difference in the occurrence of femoral neck shortening between the three groups (P > 0.05). Finite element analysis showed that the biomechanical stability of positive buttress was equivalent to anatomical reduction, and both were better than negative buttress. In Pauwels type III, the incidence of AVN in the anatomical reduction group was lower than that in both the positive buttress and negative buttress (P < 0.05). There was no significant difference in the occurrence of AVN or femoral neck shortening between positive buttress and negative buttress (P > 0.05). There was also no difference in postoperative Harris scores between the three reduction qualities (P > 0.05). Both positive buttress and negative buttress exhibited identical biomechanical qualities and were inferior to anatomical reduction.
The biomechanical and clinical dominance of positive buttress correlates with Pauwels type. Specifically, Positive buttress is biomechanically stable in Pauwels types I and II. In Pauwels type III, positive buttress is not advantageous. As the Pauwels angle increases, the biomechanical benefit of the positive buttress is lost. Therefore, regardless of the Pauwels classification, negative buttress should be avoided after reduction of femoral neck fractures in young patients.
既往研究报道，在治疗年轻股骨颈骨折时，阳性支撑与解剖复位同样有效，但这种效果是否与 Pauwels 分型有关尚不清楚。本研究旨在回顾性分析不同 Pauwels 分型年轻股骨颈骨折阳性支撑的临床预后，并评估其生物力学特性。
本研究纳入了 170 例采用三根空心螺钉治疗的年轻股骨颈骨折患者。根据术前 Pauwels 分型将患者分为三组，每组再根据复位质量分为阳性支撑、阴性支撑和解剖复位三个亚组。比较各组内不同复位质量的股骨颈缩短、股骨头坏死（AVN）发生率及末次随访时的 Harris 髋关节评分。随后招募一位志愿者，获取其髋关节 CT 数据，建立不同 Pauwels 分型下不同复位质量的有限元模型，评估各模型在施加应变后的生物力学特性。
在 Pauwels Ⅰ型中，三种复位质量的术后股骨颈缩短、AVN 发生率及 Harris 评分差异均无统计学意义（P>0.05）。但阳性支撑的生物力学稳定性优于阴性支撑和解剖复位。在 Pauwels Ⅱ型中，阳性支撑与解剖复位组的 AVN 发生率相似，均明显低于阴性支撑组（P<0.05），阳性支撑的 Harris 评分高于阴性支撑，且三组股骨颈缩短的发生率差异无统计学意义（P>0.05）。有限元分析显示，阳性支撑的生物力学稳定性与解剖复位相当，均优于阴性支撑。在 Pauwels Ⅲ型中，解剖复位组的 AVN 发生率低于阳性支撑和阴性支撑组（P<0.05），阳性支撑和阴性支撑组的 AVN 发生率及股骨颈缩短发生率差异均无统计学意义（P>0.05），三组术后 Harris 评分差异亦无统计学意义（P>0.05）。阳性支撑和阴性支撑的生物力学特性相同，均逊于解剖复位。
阳性支撑的生物力学和临床优势与 Pauwels 分型相关。具体而言，在 Pauwels Ⅰ型和Ⅱ型中，阳性支撑具有生物力学稳定性。在 Pauwels Ⅲ型中，阳性支撑不占优势。随着 Pauwels 角度增加，阳性支撑的生物力学优势丧失。因此，无论 Pauwels 分型如何，年轻患者股骨颈骨折复位后应避免阴性支撑。
