Enhancing proximal femoral pressure during cemented stem insertion

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering
• Medical Device Technology

Background:

• Poor proximal femoral pressures in cemented primary hip replacements can lead to aseptic loosening.
• Calcar occlusion during stem insertion aims to improve proximal fixation and prosthesis longevity.

Purpose of the Study:

• To evaluate the effect of calcar occlusion on intra-medullary pressure during cemented hip stem insertion.
• To compare pressure generation using different cementing techniques and occlusion methods.

Main Methods:

• 54 Exeter stems were implanted into plaster of Paris femoral moulds.
• Intra-medullary pressures were measured proximally, medially, and distally.
• Occlusion methods included no occlusion, thumb occlusion, and a horse-collar, with Palacos-R and Simplex-P cements.

Main Results:

• Proximal occlusion significantly increased proximal and distal intra-medullary pressures across all cements (P < 0.01-0.001).
• Palacos-R cement, inserted 4-4.5 minutes post-mixing with thumb occlusion, yielded the highest pressures.
• Palacos-R insertion resulted in higher pressures than Simplex-P, irrespective of occlusion method.

Conclusions:

• Calcar occlusion effectively generates and sustains high intra-medullary pressures in cemented hip replacements.
• Palacos-R cement with thumb occlusion at 4-4.5 minutes post-mixing provides optimal pressure.
• A horse-collar offers a slight pressure advantage with Simplex-P cement.