Department of Orthopedic Surgery, Prisma Health-Upstate, Greenville, SC.
J Orthop Trauma. 2022 May 1;36(5):224-227. doi: 10.1097/BOT.0000000000002288.
The most common screw placement across the femoral neck is the inverted triangle. The posterosuperior screw has a high incidence of cortical breach, creating an in-out-in (IOI) screw. This study examined the use of the radiographic landmark of the piriformis fossa (PF) to prevent screws being placed IOI. The hypothesis was that posterior screws placed below the PF inferior margin would prevent femoral neck cortex breach.
Five bilateral cadaveric specimens were used to place 10 screws along the femoral neck posterosuperior cortex. On the AP view, 5 screws were placed in a traditional manner, below the femoral neck superior cortex but above the inferior margin of the PF (APF screws), and 5 were placed below the inferior margin of the PF (BPF). All 10 screws were placed inside the posterior cortex on the lateral view. After screw placement, each hip was dissected, and the femoral necks were evaluated for signs of cortical breach.
All screws placed below the PF inferior margin were contained within the femoral neck with no incidence of being IOI. All screws placed above the PF inferior margin breached the cortex to a varying degree. All screws were similar in relation to their distance from the posterior cortex on the lateral view, with the APF screws averaging 1.98 mm and the BPF screws averaging 1.82 mm (P value = 0.46).
Placing the posterosuperior screw of the inverted triangle caudal to the PF inferior margin on the AP view seems to avoid cortical breach during percutaneous screw fixation of femoral neck fractures.
股骨颈最常见的螺钉放置方式是倒三角形。后上方螺钉皮质穿透率较高，形成内-外-内（IOI）螺钉。本研究通过使用梨状窝（PF）的影像学标志来防止螺钉IOI。假设是将后下方螺钉放置在 PF 下边缘以下，可以防止股骨颈皮质穿透。
使用 5 具双侧尸体标本，在股骨颈后上方皮质放置 10 枚螺钉。在前后位片上，5 枚螺钉以传统方式放置，位于股骨颈上皮质下方但低于 PF 下边缘（APF 螺钉），5 枚螺钉放置在 PF 下边缘下方（BPF）。所有 10 枚螺钉在侧位片上均位于后皮质内。螺钉放置后，每个髋关节均进行解剖，并评估股骨颈是否有皮质穿透的迹象。
所有放置在 PF 下边缘以下的螺钉均包含在股骨颈内，无 IOI 发生。所有放置在 PF 下边缘以上的螺钉均不同程度地穿透皮质。所有螺钉在侧位片上与后皮质的距离相似，APF 螺钉平均为 1.98mm，BPF 螺钉平均为 1.82mm（P 值=0.46）。
在前后位片上将倒三角形的后上方螺钉放置在 PF 下边缘下方似乎可以避免经皮固定股骨颈骨折时的皮质穿透。
