Department of Orthopaedic Surgery, Keller Army Community Hospital, West Point, NY.
MedStar Health Research Institute, Hyattsville, MD.
J Hand Surg Am. 2023 Jul;48(7):736.e1-736.e7. doi: 10.1016/j.jhsa.2022.01.019. Epub 2022 Mar 4.
Several improvised dynamic external fixation devices are used for treating unstable dorsal proximal interphalangeal (PIP) joint fracture-dislocations. We compared the effectiveness of 3 constructs for simulated dorsal PIP joint fracture-dislocations in a cadaver model.
We tested 30 digits from 10 fresh-frozen, thawed cadaver hands. We aimed to remove the palmar 50% of the base of each digit's middle phalanx (P2), simulating an unstable dorsal PIP joint fracture-dislocation. Each PIP joint was then stabilized via external fixation with either a pins-and-rubber-bands construct, pins-only construct, or tuberculin syringe-pins construct. We allocated 10 digits per fixation group. The finger tendons were secured to a computer-controlled stepper motor-driven linear actuator. Via this mechanism, all PIP joints were taken through 1,400 cycles of flexion-extension. With the PIP joint in neutral extension, we measured the P2 dorsal translation at baseline, after fixator stabilization, and after the motion protocol.
The actual mean P2 palmar defect created was 48% of the base. All PIP joints were unstable after creating the defect, with a mean initial P2 dorsal displacement of 3.7 mm. After application of the fixators, all PIP joint dislocations were reduced. The median residual P2 dorsal displacements were 0.0 mm for the pins-rubber bands group, 0.1 mm for the pins-only group, and 0.5 mm for the syringe-pins group. There were no cases of PIP joint redislocation after flexion-extension cycling, and the median dorsal P2 displacements were 0.0 mm for the pins-rubber bands group; 0.0 mm for the pins-only group; and 0.5 mm for the syringe-pins group.
All 3 external fixators restored PIP joint stability following simulated dorsal fracture-dislocation, with all reductions maintained after motion testing. The syringe-pins construct had significantly greater median residual P2 dorsal displacement after the initial reduction and motion testing, which is of unclear clinical importance.
This study informs surgeon decision-making when considering dynamic external fixator options for dorsal PIP joint fracture-dislocations.
几种临时的动力性外固定器被用于治疗不稳定的背侧近节指间关节（PIP）骨折-脱位。我们在尸体模型中比较了 3 种结构治疗模拟背侧 PIP 关节骨折-脱位的效果。
我们测试了 10 个新鲜冷冻解冻的尸体手的 30 个手指。我们旨在去除每个手指中节指骨的掌侧 50%的基底（P2），模拟不稳定的背侧 PIP 关节骨折-脱位。然后，通过外部固定器将每个 PIP 关节固定，使用针和橡胶带结构、仅针结构或结核菌素注射器针结构。我们为每个固定组分配了 10 个手指。手指肌腱固定在计算机控制的步进电机驱动的线性执行器上。通过这个机制，所有 PIP 关节都经过了 1400 次屈伸循环。在 PIP 关节中立伸展位，我们在基线、固定器稳定后和运动方案后测量 P2 背侧平移。
实际创建的 P2 掌侧缺陷的平均百分比为 48%。在创建缺陷后，所有 PIP 关节均不稳定，初始 P2 背侧移位的平均值为 3.7mm。应用固定器后，所有 PIP 关节脱位均得到复位。针和橡胶带组的中位数残余 P2 背侧移位为 0.0mm，仅针组为 0.1mm，注射器针组为 0.5mm。屈伸循环后没有 PIP 关节再脱位的病例，针和橡胶带组的中位数背侧 P2 位移为 0.0mm；仅针组为 0.0mm；注射器针组为 0.5mm。
所有 3 种外固定器在模拟背侧骨折脱位后均恢复了 PIP 关节的稳定性，在运动测试后所有复位均得以维持。在初始复位和运动测试后，注射器针组的中位数残余 P2 背侧移位明显更大，但其临床意义尚不清楚。
当考虑用于背侧 PIP 关节骨折-脱位的动力性外固定器选择时，本研究为外科医生提供了决策依据。
