SICOT e-Newsletter

Issue No. 43 - April 2012

Radiologic Predictors of Functional Outcome following Fractures of the Distal Radius

Summarised by Kareem El-Sorafy

This is a summary for a paper which reviews various radiological indices that are relevant to radial fractures and identifies potential predictors of functional outcome [1].

Abstract:
The fracture most commonly treated by orthopaedic surgeons is that of the distal radius. However, as yet there is no consensus on what constitutes an ‘acceptable’ radiological position before or after treatment. This should be defined as the position that will predict good function in the majority of cases. In this paper we review the radiological indices that can be measured in fractures of the distal radius and try to identify potential predictors of functional outcome. In patients likely to have high functional demands, we recommend that the articular reconstruction be achieved with less than 2 mm of gap or step-off, the radius be restored to within 2 mm of its normal length, and that carpal alignment be restored. The ultimate aim of treatment is a pain-free, mobile wrist joint without functional limitation.

Distal radius fractures are one of the commonest fractures treated by orthopaedic surgeons constituting a sixth of total fractures [2]. There is little consensus on what constitutes an acceptable radiological position. A perfect anatomical reduction is not always achievable, nor is it always necessary for a satisfactory result. Some radiological parameters are commonly used in the assessment of distal radial fractures, including radial height, ulnar variance, dorsal/palmar tilt, carpal alignment, and intra-articular gaps and steps [1].

The article explains the methods for obtaining a PA radiograph of the wrist, with the shoulder in 90° of abduction and 90° of elbow flexion with a neutral wrist and forearm. The lateral radiographs are obtained by adducting the arm while the elbow is flexed to 90° with the hand positioned in the same plane as the humerus. A rotational change can significantly affect the palmar tilt.

There is a clear detailed explanation of how to measure radiologic parameters including carpal alignment, teardrop angle and anteroposterior distance. Below is a summary of the acceptable parameters.

Table: minimum radiologic assessment for distal radius fractures

Radiological parameters:

Radial Height:
Metaphyseal comminution and shortening is the most significant factor-affecting outcomes. This is either judged by comparison to the contralateral side or in relation to the uninjured ulnar height. Radial shortening affects the kinematics of the DRUJ (distal radioulnar joint) and results in distortion of the triangular fibrocartilage [3]. Shortening ≥4mm is associated with wrist pain [4]. These effects of radial shortening apply to young active individuals and diminish with advancing age [5]. A positive ulnar variance of >3mm compared to the contralateral side is associated with reduction in grip strength [6].

Radial inclination:
There are conflicting messages in the literature due to difference in methodologies used by different investigators.

Articular incongruity:
A step of >2mm is associated with development of degenerative changes within the joint, but this is not necessarily associated with loss of function due to adaptation of the functional demands.

Dorsal/Palmar tilt:
The effect of this is less clear and measuring carpal malalignment is more accurate and if present implies significant dorsal tilt. The minimum acceptable dorsal tilt is neutral.

Ulnar Styloid fractures:
Evidence does not recommend intervention in case of ulnar styloid fractures as long as the radius is treated satisfactorily with an intact DRUJ.

This article summarises the up-to-date evidence regarding the management of distal radius fractures, which is dependant on obtaining adequate radiographs. The tear drop angle of <70° may signify an articular step.

References:

1. Ng CY, McQueen MM. What are the radiological predictors of functional outcome following fractures of the distal radius? J Bone Joint Surg Br. 2011;93:145-150.
2. PR P. Fraturas do rádio distal. 2004.
3. Adams BD. Effects of radial deformity on distal radioulnar joint mechanics. J Hand Surg Am. 1993;18:492-498.
4. Jenkins NH, Mintowt-Czyz WJ. Mal-union and dysfunction in Colles' fracture. J Hand Surg Br. 1988;13:291-293.
5. Grewal R, MacDermid JC, Pope J, Chesworth BM. Baseline predictors of pain and disability one year following extra-articular distal radius fractures. Hand (N Y). 2007;2:104-111.
6. McQueen MM, Hajducka C, Court-Brown CM. Redisplaced unstable fractures of the distal radius: a prospective randomised comparison of four methods of treatment. J Bone Joint Surg Br. 1996;78:404-409.