Biomechanical Analysis of Blade Plate Versus Locking Plate Fixation for a Proximal Humerus Fracture: Comparison Using Cadaveric and Synthetic Humeri

• Published in: Journal of orthopaedic trauma Vol. 20; no. 8; pp. 547 - 554
• Main Authors: Siffri, Paul C, Peindl, Richard D, Coley, Edward R, Norton, James, Connor, Patrick M, Kellam, James F
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins, Inc 01-09-2006; Lippincott Williams & Wilkins
• Subjects: Biological and medical sciences; Biomechanical Phenomena; Biomechanics. Biorheology; Bone Plates; Cadaver; Diseases of the osteoarticular system; Equipment Design; Fracture Fixation - methods; Fundamental and applied biological sciences. Psychology; Humans; Injuries of the limb. Injuries of the spine; Medical sciences; Models, Biological; Orthopedic Procedures - methods; Shoulder Fractures - surgery; Tissues, organs and organisms biophysics; Traumas. Diseases due to physical agents; Proximal; Prognosis; Torsion test; Diseases of the osteoarticular system; Fracture; biomechanics; blade plates; fracture fixation; locking plates; Cyclic load; Classification; Bending; Neck; Torsion; Locking; Human; Stability; Blade; Contrast; Rotation; Trauma; Displacement; Fixation; Loosening; proximal humerus fracture; Models; Humerus; Comparative study
• ISSN: 0890-5339; 1531-2291
• DOI: 10.1097/01.bot.0000244997.52751.58

OBJECTIVE:To compare the mechanical stability of a fixed-angle blade plate with that of a locking plate in a cadaveric proximal humerus fracture-fixation model subjected to cyclic loading. A secondary objective was to evaluate whether the use of synthetic humerus specimens would replicate significant differences found during cadaveric tests.
DESIGN:Mechanical evaluation of constructs in bending and torsion.
SETTING:Biomechanical laboratory in an academic medical center.
METHODS:Simulated humeral neck fractures (Orthopaedic Trauma Association (OTA) classification 11A3), in matched-pair cadaveric and synthetic specimens underwent fixation using either a 3.5-mm, 90-degree cannulated LC-Angled Blade Plate or a 3.5-mm LCP Proximal Humerus Locking Plate. Cadaveric specimen constructs were cyclically loaded in bending and torsion; synthetic specimens were tested in torsion.
MAIN OUTCOME MEASURE:Humeral shaft-bending displacements and angular rotations for respective cyclic bending loads and axial torques were recorded and compared at repeated cyclic intervals to evaluate construct loosening.
RESULTS:Locking-plate constructs exhibited significantly less loosening than blade-plate constructs for torsional loading in cadaveric specimens (P = 0.036). The two types of constructs performed similarly for torsional loading in synthetic specimens (P = 0.100). Under cyclic, closed-bending load conditions in which the plates served as tension members, both types of constructs performed similarly in cadaveric specimens (P = 0.079).
CONCLUSIONS:For simulated humeral neck fractures subjected to cyclic loading, locking-plate constructs demonstrated significantly greater torsional stability and similar bending stability to blade plates in a cadaveric specimen model. In contrast, these same constructs performed similarly with torsional loading when using synthetic humerus specimens. These results indicate potential advantages for locking-plate fixation. They also indicate that the synthetic specimens tested may not be appropriate for evaluating fixation stability in the humeral head, where cancellous bone fixation predominates.