[Experimental comparative study of 3 systems of osteosynthesis for proximal humeral fractures. Preliminary study of the mechanical properties of conserved trabecular bone].
OBJECTIVE
We have compared three systems for osteosynthesis of proximal humeral fractures on a four-fragment fracture model: Plate with tuberosity screwing (P), Kirschner wires with bone sutures (K) and an original implant, the "bilboquet" (Stryker) (B), composed of a hook for the head supported on a diaphyseal stem.


METHODS
Because of the unavailability of fresh human material, we have turned to embalmed bones after having shown, on cancellous femoral head bone, the little influence of our method Vs freezing conservation. Settings were tested in compression. We measured their mechanical resistance judged on the ultimate strength and on the slope (displacement/load), to this limit. We similarly analyzed by video recording displacement of the different fragments according to four components (head slipping, its lateral displacement, its see-saw and the separation of tuberosities), to show the weak points of the three systems.


CONCLUSIONS
K was more deformable (p < 0.001) that P and B (average slopes in mm/100N to 0.67 for K, 0.42 for P and 0.43 for B). The ultimate strength differed but not significantly (average values in Newton to 1223 for K, 1601 for P and 1721 for B). We also showed for the three techniques, the significant correlation between slopes and bony densities. Video analysis showed that P opposed lateral displacement of the head and separation of tuberosities better, the resistance to slipping and see-saw seems to be improvable by greater divergence of screws or a modification of the plate (mini canon). B opposed slipping and see-saw better but its weak point was the risk of articular break-in of the hook, by defect of resistance to lateral displacement, that for us could be limited by a less peripheral position of teeth or a modification of their form. K is indeed the least effective of the four components but we think that it would be improvable by using, for example, a centro-medullary technique, allowing an internal cortical support.
Gicquel
P
P
Service d'orthopédie, hôpital de Hautepierre, Strasbourg.
Bonnomet
F
F
Boutemy
P
P
Schlemmer
B
B
Kempf
J F
JF
D015519:Bone Density; D002102:Cadaver; D005069:Evaluation Studies as Topic; D005593:Fracture Fixation, Internal / Q000379:methods*; D006801:Humans; D006810:Humeral Fractures / Q000601:surgery*; D013314:Stress, Mechanical