Session VI Upper Extremity

*Unstable Fractures of the Distal Radius: Metaphyseal versus Bridging External Fixation

M. M. McQueen MD, FRCSEd(Orth), C. Hajducka, C. M. Court-Brown MF, FRCSEd (Orth)

Edinburgh Orthopaedic Trauma Unit, Royal Infirmary of Edinburgh, Edinburgh, Scotland

Introduction: The management of unstable fractures of the distal radius remains controversial. Previous reports of bridging external fixation, with or without mobilization have resulted in adequate anatomical results but poor functional results. The move in other anatomic areas such as the tibial pilon fracture is to joint sparing external fixation and this study was designed to explore the results of this technique in the wrist.

Method: A prospective study was performed on 60 patients with unstable fractures of the distal radius randomized into two groups. Group 1 had the distal fixator pins inserted into the distal fragment from dorsal to volar with a limited open technique in order to protect the extensor tendons. Group 2 had the distal fixator pins inserted into the 2nd metacarpal. Both groups had the proximal pins inserted into the proximal radius using an open technique. The Pennig fixator was used throughout the study. Exclusion criteria were displaced articular fractures, inability to give informed consent, treatment later than two weeks from injury and inadequate initial closed reduction. There were 30 patients in each group and the groups were similar for age, sex and mode of injury although the metaphyseal group had a larger number of AO Type C fractures than the bridging group. Radiological and functional outcome were measured at a maximum review time of one year.

Results: The average dorsal angulation for Group 1 was -5° i.e. 5° of volar tilt compared with 12° of residual dorsal angulation in Group 2. There were 2mm of shortening in Group 1 compared to 3mm in Group 2. Carpal collapse was noted in only two patients in Group 1 compared to 15 patients in Group 2. Three patients in Group 1 were considered to be mal-united compared to 15 patients in Group 2.

Mass grip strength was considerably better in Group 1 at an average of 80% of the opposite normal side compared to 64% of the opposite normal side in Group 2. There was an increased range of flexion at 88% in Group 1 compared to 75% in Group 2. Rotation was consistently regained to over 90% in both Groups.

Excluding mal-union, two of 30 patients in Group 1 and two of 30 patients in Group 2 had significant complications. In Group 1 these consisted of one late extensor pollicis longus rupture and one pin track infection requiring early removal of the fixator. In Group 2 these consisted of two patients with reflex sympathetic dystrophy.

Discussion: Metaphyseal external fixation is a significant advance in the management of the unstable distal radial fracture giving significantly better results in the management of unstable distal radial fractures than fixation across the joint. Anatomically mal-union is unusual and in particular the normal volar tilt is regained by metaphyseal external fixation thus preventing carpal collapse. The grip strength one year after injury is significantly higher with metaphyseal external fixation as is the range of flexion. Excluding mal-union the complication rates are similar with a slightly increased rate of reflex sympathetic dystrophy in the bridging fixation group.