Document Type
Thesis
Date of Award
8-31-1991
Degree Name
Master of Science in Biomedical Engineering - (M.S.)
Department
Biomedical Engineering Committee
First Advisor
Mark Zimmerman
Second Advisor
J. Russell Parsons
Third Advisor
Clarence W. Mayott
Fourth Advisor
David S. Kristol
Abstract
Often, humeral fractures requiring internal fixation can be a challenging orthopaedic procedure. Each method of treatment possesses clinical and biomechanical advantages and disadvantages. Rigid plate fixation is highly successful in treating a large variety of long bone fractures. Nevertheless, excessive soft tissue dissection is necessary, and vascular and neural anatomy of the humerus can make plate application and removal difficult. An intramedullary nail offers a relatively simple procedure, thereby reducing these anatomical concerns. However, rotational instability at the fracture site is a common complication with a conventional intramedullary nail. Thus, a study was conducted to evaluate a new interlocking intramedullary humeral fracture fixation system, the Orthofix system,a and compare its biomechanical characteristics with those of the Seidel Humeral Locking Nail system.b Additionally, both systems were compared to the AO/ASIF broad Dynamic Compression Plate system.c
An initial comparative mechanical analysis between the Orthofix nails and the Seidel nails was performed by nondestructive four-point bending tests. Twelve pairs of fresh frozen, intact humeri were harvested and subsequently tested in four point bending. Standardized, midshaft transverse osteotomies were created in each specimen. Left and right specimens were fixed with plates and nails, respectively. Nondestructive four-point bending tests and destructive torsional tests were conducted, and biomechanical analyses were performed on the humerus/implant constructs. The bending properties of an Orthofix nail and a Seidel nail are nearly the same, and approximate those of an intact humeral specimen. Bending tests demonstrated the humerus/plate constructs to be more stiff and rigid than the humerus/nail constructs in both the lateral-medial and the anterior-posterior planes. However, the plated specimens exhibited significantly higher bending properties than the intact humeri. Regarding torsional tests, an osteotomized humeral specimen fixed with a solid interlocking nail possessed superior torsional properties as compared with a AO/ASIF broad Dynamic Compression Plate or Seidel nail. The Orthofix targeting device for proximal and distal screw insertion is effective, and reduces radiation exposure of the surgical team. In conclusion, the Orthofix system is extremely successful in achieving rotational stability, potentially extending the indications for humeral fracture fixation to include comminuted and pathological fractures.
a Orthofix Srl., Verona, Italy
b Howmedica, Rutherford, New Jersey
c Synthes, Paoli, Pennsylvania
Recommended Citation
Waite, Alina Michelle, "A biomechanical analysis of three humeral fracture fixation systems" (1991). Theses. 2651.
https://digitalcommons.njit.edu/theses/2651
