Background: Total knee replacement (TKR) failure is usually due to alignment, stability or fixation defects. Objective: To quantify the loads distribution using an absorptiometric method with two different tibial stems.

Methods: We analyzed 20 patients with cemented TKR, in two groups: one of them cylindrical and the other with cruciform stem. We studied the periprosthetic bony density evolution in three areas: under the stem, internal and external baseplate. We performed dual-energy x-ray absorptiometric (DEXA) measurements at 2, 3 and 7 years of follow-up.

Results: The evolution of the bony density under the internal baseplate to 2 and 3 years decreased from 0.920.20 to 0.900.19 g/cm2; under the external baseplate changed from 0.970.36 to 0.970.38 and under the stem raised from 1.050.25 to 1.080.26 in the cylindrical group. In the cruciform group, under the internal baseplate decreased from 0.750.08 to 0.710.05, under the external one decreased from 0.890.01 to 0.850.07 and under the stem changed from 1.060.06 to 1.040.29.

Comparing only the cylindrical subgroup (three missing patients), the DEXA measurements at 2, 3 and 7 years of follow-up were: 0.88, 0.84 and 0.80 g/cm2 under the internal baseplate; 0.79, 0.78 and 0.77 under the external one, and 0.99, 0.96 and 0.99 under the stem.

Conclusions: Loss of bony density is observed progressively after TKR. Comparativily, the diminution is greater for the cruciform stem. The internal compartment is more affected.