Experimental stabilization of segmental defects in the human femur. A torsional study.

One of each of thirty-five pairs of fresh intact femora were tested to failure in torsion, recording the dynamic torque, the absorbed energy, and the angle of rotation. These results were compared with the results obtained with the contralateral femur, reconstituted after removal of a segment. Intramedullary nails with polymethylmethacrylate cement, strips of titanium mesh with cement, bone plates with and without cement, and multiple Steinmann pins with cement were the reconstituting configurations. Bone plates were the strongest configuration; the failure torques in all cases were limited by the stress concentration effects of the holes in the bone used for screw fixation. The use of cement as an adjunct to single-plate fixation provided some additional strength. The torsional strength of femora fixed with Küntscher and Schneider nails was limited by failure of the cement and bone. The use of titanium mesh with polymethylmethacrylate was less effective, because this composite has a low torsional rigidity. The use of multiple Steinmann pins packed with polymethylmethacrylate in the medullary cavity should be discouraged because severe twisting and fragmentation of the surrounding acrylic will occur at low levels of torque.