[Incidence and severity of degenerative changes in the wrist in pseudoarthrosis of the scaphoid bone]]

In patients with symptomatic scaphoid nonunion there was an increased evidence of progressive osteoarthrosis expressed as instability of the wrist [1, 2]; it is defined as a scapholunate angle of more than 70 degrees or a radiolunate angle of more than 10 degrees. Intercarpal instability causes unnatural joint movement of the wrist. This disorganization of the wrist mechanism associated with hypermobility of the schapoid bone induces degenerative changes [3]. Arthritic changes begin at the distal scaphoid-radial styloid joint and later progress to the capitolunate joint. A similarity was noted with rotatory instability of the scaphoid bone associated without fracture [2]. If mid-carpal joint exists the joint becomes unstable, the lunate rotates backwards and carpal bones show the so-called concertina deformity [4] or dorsal intercalated segment instability pattern [5].

We tried to determine the factors of risk and prognostic indicators of degenerative arthritis.

In this study 40 patients with painful nonunion of the scaphoid bone were analysed. Duration of nonunion was 1.43 year (range from 8 months to 15 years). Roentgenograms of the hand were done in anteroposterior, lateral and oblique projections. Fracture location and configuration were determined as described by Russe. Instability was determined by measuring the scapholunate and radiolunate angle in the lateral roentgenogram. Scapholunate angle more than 70 degrees and radiolunate angle more than 10 degrees were considered abnormal. To asses the amount of carpal collapse the carpal index was determined as described by Youm [6]. Abnormal value was 0.50 or less (normal value: 0.54 +/- 0.03). Four roentgenographic groups were established based on the extent of degenerative changes [7]. Group I showed no sign of degenerative changes. Group II had sclerotic lesions in fracture margins with or without a cystic formation. Group III showed lesions of radioscaphoid arthritis, including joint-space narrowing and pointing the radial styloid. Group IV had lesions of generalized arthritis of the wrist.

Duration of nonunion was not in correlation with development of osteoarthritic changes (p = 0.644, p > 0.05) (Table 1). Progressive degenerative changes correlated well with radiolunate angle (p = 0.398, p < 0.05), capitolunate angle (p = 0.381, p < 0.05) and carpal index (p = 0.392, p < 0.05) (Table 2). The average values of intercarpal angles increased with progression of osteoarthritic changes (Table 3). There were 14 (35%) proximal third located fractures and 26 (65%) in the middle third or waist. There was a statistically strong correlation between location of the fracture in proximal third and presence of degenerative changes (p = 0.341, p < 0.01) (Table 4). Intensity of arthritic changes showed no statistically significant correlation regarding untreated fractures (p = 0.665, p > 0.05).

In our study the most significant factors associated with arthritis were instability of the wrist and fracture location at the proximal third of the scaphoid bone. Mack [7] reviewed forty-seven symptomatic nonunions of the scaphoid and found a correlation between the presence of arthritis and the duration of nonunion. Also, he concluded that instability of the wrist can occur as late phenomenon in previously stable nonunion. Similar results were noted by Ruby [8] in his series. Conclusion of these authors was that the incidence of degenerative changes increased with the time after fracture of the scaphoid bone occurred [8-12]. We demonstrated that in untreated fractures associated with carpal instability, arthritis developed much earlier. Fourteen (35%) patients in our study were not treated and 92.8% belonged to Group II and Group III, with average time of nonunion duration of 27.2 months. Lunate dorsiflexion is a useful guide to carpal instability. In our experience the lunate silhouette is easily visualized on a lateral roentgenogram even in the presence of degenerative arthritis. There is a high probability that degenerative changes will occur. We recommend that a scaphoid nonunion associated with carpal instability should be operated before degenerative changes develop.