Cement – within – cement revision of the femoral component in revision hip arthroplasty.
Background
It is over 25 years since Greenwald and colleagues questioned the need to remove existing well fixed bone cement at the time of revision of a cemented total hip arthroplasty (1). Instead, they advocated the retention of well fixed cement and the re-cementation of a new component onto the existing cement. They highlighted the need to ensure that the old cement surface was clean and dry, and recommended roughening of the surface to promote fixation. They also recommended the early application of new cement.
Even with interposed blood between the 2 layers Greenwald found an interface shear strength of 2/3rds that of a single block of cement, and when preparation was maximised by rasping and drying, the shear strength was 94% that of a single block. The shear strength was maximum when the new cement was added early (Simplex, at 3 minutes). This was attributed to the availability of free monomer promoting polymerisation with the old cement. They suggested that rasping served to help clean the surface and expose residual old activator and monomer in the old cement as well as improving interlock.
Although others have questioned this practice (2), further biomechanical and clinical studies have supported its use in appropriate circumstances. Lieberman et al, from the Hospital for Special Surgery, New York, reported 19 femoral cases with no stem loosenings at a mean of 5 years (3). Rosenstein at al, when measuring the interface shear strength of cement in samples from human femora found that in all cases the cement – cement shear strength was greater than the cement bone interface strength. The cement bone interfaces however, were 30% weaker when fresh cement was placed against a revised bare bone surface. This supports the retention of well fixed cement rather than its removal and then re-cementation (4).
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