Despite many reports in the literature, treatment of scaphoid nonunion has remained controversial. Screw fixation provides more successful union rates than K-wire fixation but which of the screw types provides better compression remains debatable [1
]. Most previous studies suggest that the Acutrak screw generates greater compression; these studies have usually been performed on saw bone or cancellous bone simulations from foam or frozen human cadaveric bone models and their value for illuminating the problem of scaphoid proximal pole nonunion remains doubtful. Another area of debate is the optimal compression required to promote union [4
]. As a general rule, high compression load promotes fracture union and so compression is an important biomechanical factor in accelerated fracture healing [3
]. However, the distinction between treating scaphoid proximal pole nonunion and fresh fracture should be considered in relation to compressive screw insertion. In cases of vascularly compromised and longstanding nonunions, bone fragments may have become thin, weak and resorbed and therefore unable to resist compressive forces. Small proximal fragments may not possess adequate bone stock to carry a screw and compression may actually split the proximal fragment because of bone weakness (Fig. ).
Fig. 3 a The PA view showing a longstanding proximal scaphoid nonunion with small proximal fragment and low bone stock. b An arrow points towards the proximal fragment of the same patient. The bone is weak and resorbed. The surgeon should be aware of the risk (more ...)
Our study shows that there is no significant difference between the Acutrak and cannulated Herbert screws with respect to functional outcome, consolidation rate and time to consolidation in the treatment of proximal scaphoid nonunion. Complications were also similar. It seems that difference in compressive force between these screws does not influence the outcome. Apart from selection of the screw type, bone grafting and rigid fixation are required to achieve union. Rigid fixation is one of the primary goals in the treatment of proximal scaphoid nonunion but the use of compression introduces the risk of fragmentation.
Despite multiple studies presenting a biomechanical comparison, there are few clinical comparative studies. We found one study in the English language literature that addressed the comparison of the two screws in the treatment of scaphoid nonunion [17
]. Our results were similar; however, the superiority of our study is that it adopted a uniform procedure.
Our study was designed as a retrospective case analysis and it had certain limitations. For example, due to the fact that patient groups reflected developing treatment modalities in fixation technology, they were not equal with respect to follow-up period. Secondly, the study focuses on a specific type of injury and thus its small sample size does reduce the validity of statistical analysis. However, the inequality of mean follow-up time did not prevent us from making inferences for each group. All patients had proximal pole nonunion that was treated with dorsal capsulotomy, non-vascularised bone grafting and screw fixation. The patient rehabilitation procedure was also similar for both groups. The patient groups were well matched in terms of age, gender, time lapse from injury to surgery, complications and incidence of degenerative changes in the wrist joint.