A novel external fixation method and its impact on wrist distraction in relation to distal radial fracture

Distal radial fractures are one of the most common fractures in the world. Indirect reduction using external fixation is a commonly used treatment option for these fractures. ligamentotaxosis is utilised to realign and heal fractures. Uneven distraction forces can lead to radial/ulnar deviation and radial shortening. A common after-effect of this is wrist stiffness. Novel therapeutic options harnessing a modified method to achieve an even distraction forces across the wrist can lead to improved outcomes for these patients.

Aim of this study is to test if modified Aberdeen method is superior to standard method by testing the ligament length changes caused by both methods and to find a safe pin insertion point for Aberdeen method.

Formalin fixed cadaveric specimens (N=8) were dissected to optimise application of Aberdeen method (N=2). Tantalum markers were inserted into bone/ligaments near ligament endpoints. Radiosteriometric Analysis (RSA) was then used to measure change of ligament length (before and after applying distraction) by two different methods to determine which method achieve better wrist distraction. Average relative ligament change (RLC) was analysed (N=6) using GraphPad Prism.

The Aberdeen method could be applied, damage free, to all wrists (N=6) on the 4rth metacarpal bone. The Dorsal Radiocarpal Ligament (DRL, average RLC, Aberdeen=0.048, Standard=0.030), the Radial Collateral (RC, average RLC, Aberdeen=0.112, Standard=0.105) Ligament and the Ulnar Collateral (UC, average RLC, Aberdeen=0.079, Standard=0.068) Ligament were described and measured. Initial results of the Aberdeen method demonstrated increased ligament length compared to the Standard method (Mann-Whitney test; P=non-significant). With a reverse order of the frame application, this data was not reproducible. However, we believe this is due to limitation of formalin fixed cadaveric specimens which led to alteration of the ligaments by the traction from the first run.

This novel cadaveric study demonstrates that the fourth metacarpal bone is a safe place to apply the Aberdeen frame. Initial results showed the Aberdeen method to be superior than the standard method. The Aberdeen method has emerged as a promising treatment option for distal radial fracture, but larger studies must now be conducted.