Femoral Components: The French Paradox

It has become generally accepted that the cement surrounding a proximal femoral implant should be not less than 2 mm thick and that it should be complete i.e. without any ‘windows’ in the mantle. The widely used Barrack grading for cementing included no comment on the thickness of the cement mantle on its introduction in 1992 [1]. The following year the ‘A’ grade was qualified by the addition of the minimal thickness of 2 mm to its requirements [7]. Certain considerations arise: ▬ If a rectangular section tapered implant is used, distally the cement is unlikely to be uniform in thickness. At the corners of the prosthesis in all probability the cement will be thin at a site exposed to the increased torsional forces. Is this desirable? Amongst the contributing authors there is no consensus. On one hand it is felt that a rectangular cross section to the stem dissipates the torsional moment within cement mantle at the bone cement interface. On the other hand a stem rounded in the diaphyseal region would transfer torsional load in the metaphyseal region and risk cement cracking. This latter concern has been specifically addressed in one stem reported here by intentionally retaining of the femoral neck [2]. ▬ If the medullary canal is narrow in the presence of thick cortices either extensive reaming of cortical bone or the use of a very thin stem would be necessary. Are either desirable? Two recent publications have questioned whether the 2 mm minimum thickness is the only way to successfully stabilize a proximal femoral component.