Changes in the upper femur after low friction arthroplasty.

In 169 low friction arthroplasties, an extension to 10 years of the radiological appearances, noted at 4 years after acrylic cement had been in the medullary cavity of the femur, there was no grossly visible evidence of deterioration. An increased number of femora showed hypertrophy with normal bone texture. The number showing atrophy remained the same at about 4.8%. Absorption of the medial neck of the femur averaged 5.5 mm over the whole study and was often preceded by small cystic areas. Evidence of demarcation of cement from the endosteal surface of the femur was absent in 66%. When demarcation did occur, in most cases it was confined to the tip or below the midlevel of the stem. In only 2.4% did it reach slightly above the midlevel. No tendency could be found for the radiological appearances of medial femoral neck absorption or cement demarcation to predominate in patients with lower grade levels of function. Improved techniques, by which more perfect fixation between cement and bone in the upper level of the prosthetic stem is achieved, may eliminate instances of loosening and localized bone erosion encountered elsewhere.