1995 William J. Stickel Silver Award. Structural analysis of absorbable pin and screw fixation in first metatarsal osteotomies

The structural characteristics of 4.0-mm stainless steel screws compared with 4.0-mm poly-L-lactic acid absorbable screws and 2.0-mm stainless steel Steinmann pins compared with 2.0-mm poly-L-lactic acid absorbable pins in oblique closing base wedge osteotomies of the first metatarsal were evaluated. The authors performed oblique closing base wedge using an osteotomy guide in six matched pairs of fresh frozen first metatarsal bones. Fixation was achieved with either a 4.0-mm stainless steel screw or poly-L-lactic acid absorbable screw. An additional five pairs of matched specimens were used to compare 2.0-mm stainless steel and poly-L-lactic acid absorbable pins with the same approach. Specimens were loaded to failure with the Bionix Material Testing System at a constant rate of 0.166 mm/sec. A Student's t-test for paired samples was used with a 95% confidence interval to measure differences in ultimate load, ultimate displacement, and structural stiffness. There was not a significant difference in any of the parameters evaluated in the 4.0-mm poly-L-lactic acid absorbable versus stainless steel screw comparison (P > 0.05). Stainless steel 2.0-mm pins had significantly greater structural stiffness (P = 0.032) and less ultimate displacement (P = 0.021) than their poly-L-lactic acid absorbable counterparts. There was not a significant difference in ultimate load in poly-L-lactic acid absorbable and stainless steel pins (P = 0.59).