Enhancement of holding strength of cannulated screw supported with PMMA: a biomechanical study on femoral head [corrected].

Objective: The aim of this study was to evaluate the holding strength of cannulated screw with multiple holes on threaded area, supported with PMMA in femoral head.

Material And Methods: A total of 48 human femoral heads were divided into two groups after mineral density measurement with Q-CT. Seven-millimeter cannulated screws with multiple holes on threaded area supported with PMMA were used in the study group, while in the control group standard 7-mm cannulated screws were used. Each group was divided into three subgroups with eight femoral heads. Mineral density of each subgroup was equal to the other. Groups were compared in terms of pull-out, maximum extraction torque and cut-out.

Results: In pull-out group, maximum holding strength (N) was measured, while axial pull-out of 0.5 mm/sec applied with Instron. Results showed meaningful significant difference (p < 0.011) between two groups. In cut-out group, femoral heads were placed into Instron and loading was started from 5 N at 2 mm per minute at first, and it was continued until a failure, at least 5 mm, of implant was observed. Results showed significant difference (p < 0.05) between two groups. In maximum extraction group, 4° per second reverse torque (Nm) was applied with torque meter. Highest torque value was measured during extraction time, and results showed very significant difference (p < 0. 001) between two groups.

Conclusion: The results of our new design of cannulated screw augmented with PMMA provided background data to clinical application.