Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh PA, USA.
Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh PA, USA.
Injury. 2021 Mar;52(3):414-418. doi: 10.1016/j.injury.2021.02.007. Epub 2021 Feb 6.
Peritrochanteric fractures are a growing problem and complications relating to operative fixation of these fracture, including varus collapse and screw cutout, are common in elderly osteoporotic patients. We hypothesize that unlocked nails will demonstrate increased varus collapse and inferior construct stiffness in specimens with increased diaphyseal medullary diameter.
Sixteen non-cadaveric osteoporotic biomechanical femur specimens were utilized in this study, with eight specimens having an artificially large femoral canal to represent Dorr C femurs. All femurs were instrumented with a short cephalomedullary nail with and without distal cross-lock screw fixation and had an unstable intertrochanteric fracture created in a repeatable pattern. Specimens underwent cyclic compression to a maximal load of 1000N with segmental motion quantified through the use of visual tracking markers. Statistical comparisons were performed using one-way ANOVA with Tukey post-hoc analysis to determine differences between specific groups. Significance was defined as p<0.05.
Unlocked short cephalomedullary nails showed increased varus collapse due to motion of the nail within the femoral canal in capacious femoral canals compared with narrow femoral canals and distally cross-locked nails. The coronal deformation of the wide canal unlocked group (17.9 ±2.6) was significantly greater in the varus direction than any other fixation under compressive load of 1000N. There was no significant difference in varus angulation between the wide canal or narrow canal locked groups (11.1±8.7 vs. 8.2±1.7 respectively, p=0.267). The narrow canal unlocked group (13.7±2.4) showed significantly greater varus angulation than the narrow canal locked (p=0.015). The wide canal unlocked group showed significantly greater varus angulation than the wide canal locked group (p=0.003). Motion between the femoral shaft and the cephalomedullary nail (toggling of the nail within the shaft) was significantly greater in narrow or wide canal unlocked specimens, 7.94±2.13 and 10.2±1.7 respectively, than in the narrow or wide canal locked specimens, 2.4±0.2 and 4.2±0.5 respectively (p<0.05) CONCLUSION: Unlocked short intramedullary fixation for unstable peritrochanteric fractures results in increased varus collapse under axial compression. This study supports the use of distal cross-locking of short intramedullary fixation for unstable peritrochanteric fractures in patients with capacious femoral canals secondary to osteoporosis who might otherwise be as risk for varus collapse, device failure, and malunion.
股骨转子间骨折是一个日益严重的问题，与这些骨折的手术固定相关的并发症，包括内翻塌陷和螺钉切出，在老年骨质疏松患者中很常见。我们假设未锁定的钉子在骨干髓腔直径增加的标本中会表现出更大的内翻塌陷和较低的结构刚度。
本研究使用了 16 个非尸体骨质疏松生物力学股骨标本，其中 8 个标本的股骨管人为增大，以代表 Dorr C 型股骨。所有股骨均用短的顺行髓内钉固定，无论是否使用远端交叉锁定螺钉固定，并以可重复的模式造成不稳定的转子间骨折。标本在最大负载为 1000N 的情况下进行循环压缩，通过使用视觉跟踪标记来量化节段运动。使用单向方差分析和 Tukey 事后分析进行统计学比较，以确定特定组之间的差异。显著性定义为 p<0.05。
与窄髓腔未锁定钉和远端交叉锁定钉相比，在髓腔宽大的股骨中，未锁定的短顺行髓内钉会因钉子在髓腔内的运动而导致更大的内翻塌陷。在 1000N 压缩负荷下，宽管未锁定组（17.9±2.6）的冠状面变形明显向内侧（17.9±2.6），比任何其他固定方式都大。在 1000N 压缩负荷下，宽管或窄管锁定组之间的内翻角度没有显著差异（分别为 11.1±8.7 和 8.2±1.7，p=0.267）。窄管未锁定组（13.7±2.4）的内翻角度明显大于窄管锁定组（p=0.015）。宽管未锁定组的内翻角度明显大于宽管锁定组（p=0.003）。与窄或宽管锁定标本相比，窄或宽管未锁定标本（2.4±0.2 和 4.2±0.5）之间的股骨干与顺行髓内钉之间的运动（髓内钉在骨干内的摆动）明显更大，分别为 7.94±2.13 和 10.2±1.7（p<0.05）。
不稳定股骨转子间骨折的未锁定短髓内固定在轴向压缩下会导致更大的内翻塌陷。本研究支持在骨质疏松症患者中使用远端交叉锁定短髓内固定治疗宽大髓腔的不稳定股骨转子间骨折，这些患者可能存在内翻塌陷、器械失败和畸形愈合的风险。
