Femoral Cement Mantle - Alistair Jepson 17/6/2003

Shape of cementmantle determined by:

1. Cross-sectional area of stem & of medullary canal
2. Orientation of stem & cup
3. Orientation of stem in canal
4. Amount of cancellous bone removed

Miller : ‘controversial … suggested that minimum of 2mm or “two-thirds”rule’ i.e. 2/3 of canal filled by prosthesis & 1/3 by cement

Campbell ’s : ‘stems to occupy ~80% of cross section of medullarycanal with an optimal cement mantle of 4mm proximally & 2mm distally’

Postel etal (France): usedalmost universally in France – thin mantle – prosthesis used should be same s normal

Varus positioninghas been implicated as contributory to mechanical loosening due to increasedbending moment and decreased axial loading on the stem – thereforetraditionally many authors have recommended stems in neural or slight valgus.

Cement has poortensile and shear strength (strongest in compression, although not as strong asbone), therefore cement #’s tend to occur on lateral (tension) side. Reductionin the number of voids (porosity) with 2 ^nd /3 ^rd generationtechniques increases cement strength and decreases cracking