SEDL / STP / STP1008-EB / STP10366S

Mechanics of Distal Locking in Intramedullary Rods: Comparison in Osteoporotic and Normal Femurs

Latta, L
Director of research, associate professor and chief of Trauma Service, and resident, University of Miami, School of Medicine, Miami, FL

Zych, GA
Director of research, associate professor and chief of Trauma Service, and resident, University of Miami, School of Medicine, Miami, FL

Greenbarg, P
Director of research, associate professor and chief of Trauma Service, and resident, University of Miami, School of Medicine, Miami, FL

Milne, T
Biomedical engineer, University of Miami, Orthopaedic Biomechanics Laboratory Mt. Sinai, Mt. Sinai Medical Center, Miami Beach, FL

Pages: 9    Published: Jan 1989

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Abstract

The pseudostatic torsional stiffness and strength of fixation of two types of distal locking intramedullary nails was measured in embalmed human femora which were graded for osteoporosis. Cortical distal locking (Grosse-Kempf) was stronger than cancellous distal locking (Brooker-Wills) rods in both normal and osteoporotic femora. There was also a significant loss in strength of fixation for osteoporotic versus normal bones with either type of fixation, but the difference was more pronounced with cancellous fixation.

Cyclic testing to ±20 deg internal and external rotation showed no difference in loosening between cortical and cancellous locking in normal bones. But in osteoporotic bone, loosening was proportional to degree of osteoporosis with cancellous locking and was significantly greater than with cortical locking. There was no significant difference in loosening for cortical locking rods in normal versus osteoporotic bone.