Objective: Determine contributions of plate length and locked fixation in an ulna fracture.
Methods: two groups of six pairs of ulnae were plated with a small-fragment LCP around a 1 cm ostectomy. Control specimens: eight-hole plate, three consecutive unlocked screws on each side. Experimental specimens: 10-hole plate, two screws (Group 1, Unlocked; Group 2, Locked) in near- far configuration on either side.
Outcomes: Stiffness in torsion and 4-point bending stiffness and load at yield.
Results: Unlocked: mean torsional stiffness (Ncm/deg) for the experimental and control specimens, 7.57 and 7.73, respectively (p > 0.05); mean bending stiffness (kN/m), 88.50 and 90.76, respectively (p > 0.05); and mean yield strength (kN), 1.06 and 0.89, respectively (p < 0.05). Locked: mean torsional stiffness for the experimental and control specimens, 7.10 and 8.27, re- spectively (p > 0.05); mean bending stiffness, 72.96 and 79.20, respectively (p > 0.05); and mean yield strength, 1.23 and 1.03, respectively (p > 0.05). Mean differences between the experimental and control specimens in tor- sion: Unlocked, 0.17; Locked, 1.17 (p > 0.05). Mean differences in bending stiffness: Unlocked, 2.25; Locked, 6.24 (p > 0.05). Mean differences in yield strength: Unlocked, 0.17; Locked, 0.21 (p > 0.05).
Conclusions: Locked plating provided no mechanical advantage over unlocked plating. The use of a longer plate with unlocked screws increased yield strength.