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Ex Vivo Comparison of One Versus Two Distal Screws in 8 mm Model 11 Interlocking Nails Used to Stabilize Canine Distal Femoral Fractures
Author(s) -
REEMS MICHAEL R.,
PLUHAR G. ELIZABETH,
WHEELER DONNA L.
Publication year - 2006
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.2006.00127.x
Subject(s) - medicine , intramedullary rod , fixation (population genetics) , femur , biomechanics , orthodontics , femoral fracture , anatomy , surgery , population , environmental health
Objective— To compare the structural properties of an 8 mm model 11 interlocking nail (IN) with 2 proximal and 2 distal screws (2/2) to 2 proximal and 1 distal screws (2/1) in an unstable canine fracture model. Study Design— Ex vivo biomechanical investigation. Sample Population— Eight pairs of adult canine femurs. Methods— A simple transverse distal metaphyseal femoral fracture with a 1 cm gap was created. The unstable fracture in 1 femur was repaired with a nail with 2 distal and 2 proximal screws and the paired femur with a nail with 1 distal and 2 proximal screws. Cyclic mechanical testing in torsion was performed to assess fatigue life, peak torque, stiffness, and mode of failure. Results— All 2/1 IN‐femoral constructs, but only 2 of eight 2/2 constructs, failed before completion of 50,000 loading cycles. The 2/2 constructs had significantly greater peak torque to failure ( P =.002) and longer fatigue life ( P =.00003) compared with 2/1 constructs. There were no significant differences in stiffness between 2/2 and 2/1 constructs when the non‐failed constructs were compared ( P >.5). All constructs failed by screw deformation. Conclusions— An 8 mm model 11 IN used for fixation of unstable canine distal femoral fractures has a longer fatigue life and is stronger under torsional loads when 2 rather than 1 distal screws are placed. Clinical Relevance— When repairing unstable canine distal femoral fractures with an IN system, 2 distal screws should be inserted to avoid catastrophic implant failure before bone healing is achieved.