Forearm Shortening Impact on Pronation and Supination

Background: Shortening has been described to treat severely mangled extremities, replantations and nonunions. Outcomes after this procedure in the forearm are vaguely described. This study addresses how the forearm rotation is affected by: (1) location of the shortening; (2) the amount of the shortening at different locations. Methods: Nine fresh cadaveric forearms were dissected preserving intact proximal and distal radio ulnar joints and interosseous membrane. The widest point of the interosseous space and its location over the ulna were measured, defining the peak interosseous distance (PID) and the peak interosseous distance level (PIDL). Stabilization and fixation of the specimens were performed by using a platform and external fixators. Consecutive ostectomies were performed within one centimeter intervals at the distal, middle and proximal forearm thirds. A repeated measures mixed-effects (RMME) specific model was designed for the statistical analysis. Results: Before intervention, the average full forearm rotation was 157° (101-185), supination 80° (56-90)/pronation 77° (45-95). The average PID was 15.6 mm in supination and 12.5 mm in pronation. The PIDP were 52.2% and 58.3% of the ulna length in supination and pronation, respectively. The rotation lost were: middle third 5.31°/cm in supination and 6.12°/cm in pronation, distal third 1.62°/cm in supination and 2.20°/cm in pronation, the proximal third was not affected by up to 5 cm of shortening. Conclusions: These data suggest that shortening of the middle and distal third of the forearm might have more significant adverse effect on forearm rotation compared with the proximal third.