Biomechanical evaluation of extramedullary versus intramedullary fixation for reverse obliquity intertrochanteric fractures
| Autor: | Paul R.T. Kuzyk, Emil H. Schemitsch, Joel Lobo, Rad Zdero, Michael D. McKee, Daniel B. Whelan |
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| Rok vydání: | 2008 |
| Předmět: |
musculoskeletal diseases
medicine.medical_specialty Medullary cavity External Fixators medicine.medical_treatment Osteotomy medicine.disease_cause law.invention Weight-bearing Intramedullary rod Weight-Bearing Femoral head law Fracture fixation Materials Testing medicine Cadaver Humans Orthopedics and Sports Medicine Pliability Aged Mechanical Phenomena Orthodontics Aged 80 and over business.industry Biomechanics General Medicine Anatomy Middle Aged musculoskeletal system Internal Fixators Fracture Fixation Intramedullary Equipment Failure Analysis medicine.anatomical_structure Orthopedic surgery Surgery Stress Mechanical business Femoral Fractures |
| Zdroj: | Journal of orthopaedic trauma. 23(1) |
| ISSN: | 1531-2291 |
| Popis: | OBJECTIVES This study evaluated the 135-degree hip screw, 95-degree hip screw, and intramedullary hip screw (IMHS) for fixation of reverse obliquity intertrochanteric fractures. METHODS Twelve matched pairs of human femora (mean age 64 years) were obtained. Osteotomies were created in left femurs at a 33-degree angle, running inferolaterally from the lesser trochanter to mimic reverse obliquity intertrochanteric fractures. Right femora acted as controls. Three groups of left femora (n = 4 per group) had a 135-degree hip screw, 95-degree hip screw, or IMHS inserted. Strain gages were placed distal to the fracture site to monitor fragment strain. A linearly variable differential transformer measured lateral displacement of the proximal femur. An Instron tester applied vertical loads to the femoral head. Outcome measures of stiffness, strain, and lateral displacement were determined at 25-degree adduction, 25-degree abduction, 25-degree flexion, and 90-degree flexion. A 2-cm bone gap was then created at the fracture site to simulate comminution and the mechanical tests repeated. Failure load was assessed in 25-degree adduction with a bone gap. RESULTS There was no difference in normalized stiffness between constructs before creation of a gap. After gap creation, stiffness of all constructs was reduced (P = 0.03), and there was a significant difference in adduction (135-degree hip screw, 46.6% +/- 3%; 95-degree hip screw, 22.9% +/- 2%; and IMHS, 53.7% +/- 7.8%) (P < 0.05). Similar results were noted for abduction and flexion. There was no significant difference in lateral displacement between constructs before (P = 0.92) or after (P = 0.26) gap creation. Failure load was significantly different (135-degree hip screw, 1222 +/- 560 N; 95-degree hip screw, 2566 +/- 283 N; and IMHS, 4644 +/- 518 N) (P = 0.02). CONCLUSIONS With bone contact, there were no statistically significant differences in the stiffness between the constructs. With a gap, however, the IMHS bone implant construct was significantly stiffer and had a greater load to failure than the 135-degree and 95-degree constructs. |
| Databáze: | OpenAIRE |
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