Abstract
The first porous-coated femoral component approved for use without cement was released in 1983. Today, there are many implants with a similar amount of porous coating. The hallmark of these porous-coated implants is a cylindrical shape distally and a triangular metaphyseal shape. Extensively coated components gain initial stability in the femoral diaphysis.
Since 1982, we have used extensively porous-coated femoral components in all our patients. Our oldest series of patients is a consecutive non-selected group of 211 hips that have been followed for a mean of 20 years. Combining the loose and the revised, there is only a 3% femoral failure. In addition, we have studied patients with disease processes not originally thought to work well with cementless techniques, including rheumatoid arthritis, avascular necrosis and patients over 65.
Despite the good results, the main concern is that proximal bone loss secondary to the stress shielding caused by a stiff extensively porous-coated femoral component will lead to difficulty at the time of revision. At a mean 14 years, we have not seen any adverse clinical consequences that can be attributed to proximal stress shielding, though the longer term consequences of adaptive femoral remodeling need to be followed. In our patients, extensive proximal bone loss secondary to stress shielding is a radiographic sign of bone ingrowth that occurs in 25% of cases. In the remaining 70–75% of cases, lesser degrees of proximal bone loss occur which confirm bone ingrowth.
Extensively coated components gain stability in the femoral diaphysis. The femoral diaphysis is prepared with straight reamers until the reamer engages the cortex for 5cm. A slightly larger straight femoral component is inserted with a scratch fit. No matter what the shape of the femur or how osteoporotic the patient, there will always be 4–5cm of cortical bone for fixation of a straight 6 inch stem.
