Quantitative evaluation of the posterior deltoid to triceps tendon transfer based on muscle architectural properties

The architectural properties of the posterior deltoid muscle and the 3 head s of the triceps were measured using microdissection techniques to determin e whether substitution of triceps function by the posterior deltoid is arch itecturally appropriate. Muscles from 10 fresh cadaver specimens were fixed by high-pressure perfusion using buffered formaldehyde. Muscle architectur al properties, including pennation angle, fiber bundle length, sarcomere le ngth, and physiologic cross-sectional area, were determined. Fiber bundle l ength varied significantly among the deltoid (123.1 +/- 7.8 mm), medial (64 .5 +/- 3.8 mm), lateral (66.5 +/- 5.4 mm), and long (85.3 +/- 9.5) heads of the triceps. The physiologic cross-sectional area of the posterior deltoid was significantly less than the total triceps area and was predicted to pr ovide only approximately 20% of the maximum isometric tension of the combin ed triceps heads. These data demonstrate that the long fibers of the poster ior deltoid render it a very suitable transfer to provide elbow extension b ecause of its tremendous excursion and also show why useful functional resu lts seem relatively independent of posterior deltoid tension at the time of surgery. (J Hand Surg 2001;26A:247-155. Copyright (C) 2001 by the American Society for Surgery of the Hand.).