[Role of wrist instability in the onset of pseudoarthrosis of the scaphoid bone].

INTRODUCTION: The most common fracture involving the wrist is a fracture of the scaphoid bone. Fracture of the scaphoid most frequently occurs in young adult male and usually involves the wrist of the scaphoid. There is a universal agreement that the majority of these fractures will heal if immobilized property and for a long period of time [1, 2]. In the treatment of these fractures much attention has been payed to bone damage and not to associated ligament injury. It is reported that the incidence of nonunion of scaphoid fractures is ten per cent and that the frequency of this complication remains essentially unchanged [3, 4]. Failure to improve the outcome suggests that the mechanisms and causes of this complication are poorly understood. Explanations of nonunion or delayed union of scaphoid bone are: poor initial treatment or even no treatment [3], delayed diagnosis [5], fragments displacement [5-8], improper immobilization [9], site and direction of the fracture [3] and wrist instability [8, 10].

AIM: The study was undertaken to analyse the influence of carpal instability on the development of scaphoid nonunion.

METHOD: The study concerned 40 patients with painful nonunions of the scaphoid bone. Duration of nonunion was 1.43 year. There were 37 (92%) male and 3 (8%) female patients. Site and direction of the fracture, initial treatment and carpal collaps were analysed. Data processing was done for all examined patients (Table 1).

RESULTS: Dominant hand was involved in 24 (60%) patients and nondominant hand in 16 (40%) subjects. Carpal collaps was present in 68% of patients. There were 14 (35%) untreated patients (Graph 1). Untreated fractures were statistically insignificant regarding the intensity of carpal collaps (p = 0.101; p > 0.05). The physical examination usually revealed focal tenderness, a palpable click with ulnar deviation, abnormal antero-posterior mobility with passive range of motion or a combination of these findings. Standard X-rays evaluated fracture location and carpal instability or collaps. There were 14 (35%) proximal third located fractures and 26 (65%) in the middle third of wrist (Graph 2). There was no statistically significant correlation between location of the fracture and presence of carpal collaps (p = 0.081; p > 0.05).

DISCUSSION: There were 35 per cent overlooked fractures. Delay in diagnosis of a scaphoid fracture has been suggested as a significant factor in the development of nonunion [5, 7]. However, in our series of nonunions, non treatment does not occur frequently enough to be the critical factor. Most series report about 2/3 of nonunions occurring at the wrist [7, 9]. Our series shows a similar distribution, arguing against site as a critical factor. There appears to be a nearly uniform rate of nonunion in most of the reported series [7, 15, 16], regardless of the position of the wrist, whether or not the thumb was immobilized. Evidence of ligamentous injury in our series led us to conclude that scaphoid nonunion is consistently associated with carpal instability pattern. In our series 68% of nonunions associated with carpal collaps were present. We found no statistically significant correlation between carpal collaps and nontreated fractures or location of fracture site. Therefore, we concluded that carpal collaps was consistently present and, thus the critical factor in wrists with ununited scaphoid fractures.