Bone microindentation and pressure algometry applied to revision total knee replacement and tibial end-of-stem pain. Preliminary results in a group of twenty patients

Abstract

ObjectivesTo study the relationship between the appearance of end-of-stem pain with a preoperative decrease in local bone strength by using the bone microindentation technique. The potential usefulness of pressure algometry in the diagnosis and monitoring of this group of patients is also determined. Materials and methodsA preliminary intra- and inter-rater correlation study was performed in a group of 50 healthy volunteers in order to validate the algometry technique. A prospective study was then conducted on 20 patients with a mean age of 74 years (range 57–84) undergoing knee prosthetic surgery with use of a cementless tibial stem. Bone microindentation and pressure algometry measurements were made preoperatively, and after one year of follow-up. The statistical analysis was performed using the Intraclass correlation coefficient and the Student's t-test for paired data. ResultsThe intra- and inter-rater correlation values were excellent; 0.91 (0.84–0.95) and 0.86 (0.74–0.92), respectively. No significant variations were found in the microindentation (P=0.11) or in the pressure algometry (P=0.6) values after one year of follow-up. Nevertheless, a significant correlation was observed between the values for pressure algometry and the EVA (P=0.002) and functional scale (P=0.02) at the end of follow-up. ConclusionsPressure Algometry is a useful tool to evaluate this group of patients. Bone microindentation does not seem to be useful in identifying patients with increased risk of developing tibial end-of-stem pain.