Abstract
Background
Angular stable volar locking plates have become increasingly popular for more comminuted fractures of the distal radius. Newer designs of plates have been thicker in profile and incorporate more options for distal fragment fixation. Although they have been shown to be successful at maintaining reduction to allow early mobilisation the main drawback is from screw cut-out. In our practice we have noticed that the newer style of plates that offer more rigid fixation has lead to more instances of screw cut-out. We aimed to quantify the minimum number of locking pegs and or screws need to maintain the operative reduction.
Method
We retrospectively looked at a series of 46 patients that had undergone volar plating. We assessed the fracture severity on pre-operative films (according to AO classification) and compared radiographic parameters (volar tilt VT, radial inclination RI and radial height RH) on post-operative films. We calculated the amount of reduction lost from initial post operative x-rays to radiographs taken when union was confirmed. We compared this to the number of locking units used to fix the distal radius and also the configuration they were inserted, i.e. the number in the radial and middle columns.
Results
The mean loss of reduction in all plates was 0.9mm of RH, 2.2degs of RI and 2.8degs of VT. There was no difference in mean ‘reduction lost’ between plates that had a total of 2 or 3 locking units (RH 1mm and 1mm, RI 2.0deg and 2.7deg and VT 2.9deg and 3.2 deg respectively). This was also case when sub-analysing more severe OTA Type C fractures.
Conclusion
Only one locking peg is needed under each column for adequate stability (i.e. a total of two distal locking units). Any more than this confers no additional benefit in maintaining reduction, ever in more severe fractures. The extra rigidity provided by more locking screws/pegs and also thicker plates: as provided by newer designs of plates, may make them more prone to cut out.
