Effects of hybrid plating with locked and nonlocked screws on the strength of locked plating constructs in the osteoporotic diaphysis.
BACKGROUND
Hybrid plating (HP) may improve fixation strength of locked plating (LP) constructs by combining the use of locked and nonlocked screws within a bone segment. This biomechanical study evaluated whether a hybrid bridge plating construct provides greater fixation strength than an all-locked construct in the osteoporotic diaphysis.


METHODS
LP and HP constructs were applied to a validated surrogate of the osteoporotic femoral diaphysis in a bridge plating configuration. In LP constructs, plates were applied with three locking screws on each side of the fracture gap and remained 1 mm elevated. In HP constructs, plates were applied with two conventional screws complemented by a single locked screw on each side of the fracture. Constructs were tested under dynamic loading to failure in bending, torsion, and axial loading to analyze construct strength and failure mechanism in each loading mode.


RESULTS
Compared with the LP construct, the HP construct was 7% stronger in bending (p = 0.17), 42% stronger in torsion (p < 0.001), and 7% weaker in axial compression (p = 0.003). In bending, constructs failed by periprosthetic fracture. In torsion, LP constructs failed by screw breakage, and HP constructs failed by periprosthetic fracture or breakage of the locking screw. In axial compression, all constructs failed by screw migration.


CONCLUSIONS
HP delivered similar bending strength and higher torsional strength than an all-locked bridge plating construct, while causing only a small decrease in axial strength. It may therefore provide an attractive alternative to an all-locked construct for plate fixation in the osteoporotic diaphysis.
Doornink
Josef
J
Biomechanics Laboratory, Legacy Research & Technology Center, Portland, Oregon 97232, USA.
Fitzpatrick
Dan C
DC
Boldhaus
Sebastian
S
Madey
Steven M
SM
Bottlang
Michael
M
D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D018483:Diaphyses / Q000473:pathology / Q000601:surgery*; D005264:Femoral Fractures / Q000209:etiology / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D008422:Materials Testing; D008954:Models, Biological; D010024:Osteoporosis / Q000150:complications* / Q000473:pathology; D013314:Stress, Mechanical; D013718:Tensile Strength; D016474:Weight-Bearing