Locally Administered Clodronate in the Prevention of Aseptic Implant Loosening

It represents the length of the translation vector of the point in a rigid body that has the greatest motion. It can only have positive values, and is not normally distributed. The reason for using MTPM is that in many cases, motion implies a biological effect of some kind and this effect is liable to be greatest at the point of maximum motion. The parameter has been measured by RSA-methods, which is an accurate method of determining the migration and wear of orthopaedic implants: it determine the precise location of two distinct objects relative to each other in three dimension such as the relative position of the femoral component and the proximal femur. In radiostereometric analysis the position in space of the original object is reconstructed from a two dimensional x-ray film using tantalum beads. Movement between segments is then calculated by localizing each segment in a coordinate system. Lower values represent a better outcome.

BMD was measured by dual-energy X-ray absorptiometry, DXA. In clinical use, precision errors are < 5 %. To evaluate the horizontal linear distribution of the BMD, seven Gruen zones, peri-prosthetic sub-regions of interest, ROI (region of interest) were calculated by the software on the anteroposterior view of the proximal femur. The value of BMD is g/cm2 and it estimates the strength of the bone. Higher values/lesser decrease in values represent a better outcome.

Subsidence and vertical movement of the femoral stem (scale micrometers), x-, y- and z-translations. Parameters were measured using RSA-methods and the scaling is linear. Lower values represent a better outcome.

The maximal MTPM value after 3 months when the expected integration of stem should have happened. Lower values represent a better outcome.

This parameters summarize the BMD and RSA values together. The investigators have planned it to evaluate the correlation between the quality of periprosthetic bone in baseline and the migration of femoral stem during 2 years follow-up period between the study groups.

Harris Hip Score (HHS) is a clinician-based outcome measure, health status scale, that is frequently used to measure the outcome of total hip arthroplasty. It is measured by questionnaire that give points from 0 to 100. Higher values represent a better outcome.