Orthopaedic Surgery, Weill Cornell Medical College, New York, NY 10065 USA ; Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
Harvard Medical School, 25 Shattuck Street, Boston, MA 02115 USA.
HSS J. 2014 Feb;10(1):6-12. doi: 10.1007/s11420-013-9359-3. Epub 2013 Sep 24.
The success of ankle distraction arthroplasty relies on the separation of the tibiotalar articular surfaces.
QUESTION/PURPOSE: The purpose of this study was to find the minimum distraction gap needed to ensure that the tibiotalar joint surfaces would not contact each other with full weight-bearing while under distraction.
Circular external fixators were mounted to nine cadaver ankle specimens. Each specimen was then placed into a custom-designed load chamber. Loads of 0, 350, and 700N were applied to the specimen. Radiographic joint space was measured and joint contact pressure was monitored under each load. The external fixator was then sequentially distracted, and the radiographic joint space was measured under the three different loads. The experiment was stopped when there was no joint contact under 700N of load. The radiographic joint space was measured and the initial (undistracted) radiographic joint space was subtracted from it yielding the distraction gap. The minimum distraction gap (mDG) that would provide total unloading was calculated.
The average mDG was 2.4 mm (range, 1.6 to 4.0 mm) at 700N of load, 4.4 mm (range, 3.7 to 5.8 mm) at 350N of load, and 4.9 mm (range, 3.7 to 7.0 mm) at 0N of load.
These results suggest that if the radiographic joint space of on a standing X-ray of an ankle undergoing distraction arthroplasty shows a minimum of 5.8 mm of DG, then there will be no contact between joint surfaces during full weight-bearing. Therefore, 5 mm of radiographic joint space, as recommended historically, may not be adequate to prevent contact of the articular surfaces during weight-bearing.
踝关节牵张成形术的成功依赖于距下关节表面的分离。
问题/目的:本研究的目的是找到确保在牵张时距下关节表面在全负重下不会相互接触所需的最小牵开间隙。
将环形外固定器安装在九个尸体踝关节标本上。然后将每个标本放入定制的负载室中。在标本上施加 0、350 和 700N 的载荷。测量放射学关节间隙,并在每个载荷下监测关节接触压力。然后,外固定器依次牵开,在三种不同载荷下测量放射学关节间隙。当在 700N 载荷下没有关节接触时,实验停止。测量放射学关节间隙并从初始(未牵开)放射学关节间隙中减去,得到牵开间隙。计算提供完全卸载的最小牵开间隙(mDG)。
在 700N 载荷下,平均 mDG 为 2.4mm(范围,1.6 至 4.0mm),350N 载荷下为 4.4mm(范围,3.7 至 5.8mm),0N 载荷下为 4.9mm(范围,3.7 至 7.0mm)。
这些结果表明,如果在接受牵张成形术的踝关节站立 X 光片上的放射学关节间隙显示最小的 5.8mm 的 DG,则在全负重下关节表面之间不会发生接触。因此,5mm 的放射学关节间隙,如历史上推荐的那样,可能不足以防止在负重时关节表面接触。