Predisposing factors for migration of epiphyseal screws into physis in tension band plating.

The migration of epiphyseal screws into growing physis in tension band plating is a known complication. We investigated the screw migration into physis in 10 patients (18 plates) to study the various technical details, which may have contributed to this complication. The methodology involved retrospective review of radiological records. Among these 10 affected patients, in four patients, there were eight additional tension band plates, which had remained uncomplicated ('controls') at the time when implant failure was detected. We statistically compared the length of epiphyseal screw, proximity of screw start point to the physis, screw trajectory angle, interscrew angle and correction rate between the migrated and other uncomplicated plates. Majority patients were postrachitic ( n = 7). The mean time from primary procedure to detection of radiological complication was 15.1 months. The mean epiphyseal screw length proportion in migrated and uncomplicated plates matched. The starting point of epiphyseal screw was relatively closer to physis in migrated plates. The trajectory of epiphyseal screw with respect to physis was more divergent in the migrated plates ( P = 0.02). All implants were inserted in a divergent manner with mean interscrew angle being 22.3° for migrated and 13.8° for the uncomplicated plates ( P = 0.02). The correction rate of the implant reduced as it failed. Osteopenic bone and pathological physis predispose to migrated plates. Technically, a wider trajectory of epiphyseal screw and too divergent screws should be avoided. A migrated implant becomes less effective in its function.