Radiological Criteria for Instability in Distal Radius Fractures

1. Background

Distal radius fracture is the most common fractures in adults, and there is agreement that there is a correlation between anatomical reduction and function in younger age groups (McQueen 1988, Cooney 1989). In the case of elderly patients (over 65 years), this is more debated (Egol 2010, Hassellund 2021, Panigrahi 2022).

Dislocated distal radius fractures are initially treated with closed reduction and plaster (Arora 2011, Earnshaw 2002, Mackenney 2006). An unstable distal radius fracture is a fracture that dislocates after casting despite a successful reduction (Chung 2023). It is important to find out as early as possible whether a fracture is unstable only with a cast, so that these patients can be operated on without unnecessary delay, as a delayed operation can lead to reduced function (Selles 2021). Many have tried to come up with criteria that can predict whether the fracture is too unstable for plaster treatment only, but currently there are no standard criteria for this (Mackenney 2006, Lafontaine 1989, Nesbitt 2004, Abbaszadegan 1989, Tahririan 2013, Hove 1994, Leone 2004 ). Only increasing age, female gender and dorsal cortical comminution (all of which are factors that can indicate osteoporosis/osteopenia) have been shown to be significant criteria based on a meta-analysis from 2016 (Walenkamp 2016). However, there is a need for further studies of this, as practice now differs between the various hospitals in Norway, and also between different countries.

According to the Norwegian guidelines, a distal radius fracture is considered for surgery based on certain radiological criteria. For patients under 65 years of age, it is strongly recommended to operate on a distal radius fracture if there is ≥ 10 degrees of dorsal angulation of the radius articular surface (from 90º on the longitudinal axis of the radius), ulnar variance ≥ 2 mm, intra-articular step ≥ 2 mm, incongruence in the distal radioulnar joint or cortical comminution in the fracture area/substance loss of the dorsal cortex of the distal radius before reduction. If one chooses conservative treatment for a well-reduced but possibly unstable fracture, it is good practice to follow the patient with regular X-ray checks. In American guidelines, there is a moderate recommendation to operate on fractures with dorsal tilt more than10 degrees, ulnar variance more than 3mm, intra-articular diastasis or step more than 2 mm after reduction. The recommendations behind the guidelines in Norway and in the USA are based on various studies with varying degrees of strength, as well as the surgeons experiences. Most of these studies include patients over 65 years of age, and increasing age has been shown to be one of the strongest indicators of whether a reduced fracture dislocates (Mackenney 2006). Many studies also exclude patients who have been set up directly for surgery without the criteria for why these patients have been considered for surgery being specified in more detail (Walenkamp 2016). Furthermore, most studies do not distinguish between displaced and minimally displaced fractures. Dorsal angulation that is accepted varies from 10-15 degrees from the neutral plane or 5 degrees from the starting point in various studies. Dorsal cortical comminution is not defined in most studies. Intra-articular fractures are often also included without any reflection on this. Some studies show that these are more unstable than extra-articular fractures (Lutz 2011). Although the meta-analysis (Walenkamp) from 2016 did not find that intra-articular fractures are more unstable, it was discussed whether part of the reason could be that many intra-articular fractures go straight to surgery and that only the least dislocated intra-articular fractures are considered for conservative treatment. 2. Problems and goal setting

There is reason to ask whether the guidelines, especially the Norwegian ones, can lead to overtreatment, as clinical experience indicates that a portion of the distal radius fractures in patients between 18 and 65 years of age retain their position after closed reduction without surgery. In particular, this applies to extra-articular A fractures (based on the AO classification), as it has been shown that dorsal tilt is what most often triggers an indication for surgery (Cross 2022). Most people would agree that there is a difference between a comminuted, intra-articular fracture that is reduced to a suboptimal position, and a simple A2 fracture with a dorsal angulation of 20 degrees that is reduced to an anatomical position, but often this last group still ends up with surgery . There are no guidelines that separate these types of fractures. The question is how we can select the fractures that maintain their position after closed reduction. A closed reduction is considered successful when the most anatomical appearance of the bone is achieved. Whether the volar cortex is hooked on after reduction has been shown to be an important indication that a fracture holds its position (LaMartina 2015, Phillips 2014), but none of the guidelines in Norway, the USA, Great Britain or Denmark include this as a criterion. Only the Swedish guidelines have taken this into consideration. In addition, it should be considered whether patients between 50-65 years should be separated as a group, as many of these patients have osteoporosis/osteopenia.