Background

In the late 1980's Michael Freeman conceived the idea that knee replacement would most closely replicate the natural knee joint, if the medial Tibio-Femoral articulation was configured as a “ball-in-socket”. Over the last three decades, medial rotation and medial pivot designs have proved successful in clinical use. Freeman's final iteration of the medial ball-in-socket concept was the Medial Sphere knee. We report the three-year survivorship, clinical outcomes, patient reported outcome measures (PROMs) and radiographic analysis of this implant in a multi-centre, multi-surgeon, prospective observational study.

More than two thirds of TKA are performed on women. Most TKA systems are based on the male anatomy. Therefore one could ask if a women specific design is needed in Knee Arthroplasty. There are two distinct types of distal femur: the normal one and the narrow one. In the narrow femur the problem of overhang can occur because for a given AP dimension (sizing of the implant) the corresponding ML dimension is too large. Many years ago these findings were already published in different articles. It is only in recent years that interest came from the industry. In our department a study project was initiated in January 2006. This led to the development of the Stature Femoral component for the Advance Medial Pivot knee prosthesis. The first one was implanted in June 2007 and since then it is used in 60% of our female patients and 11% in our male patients. The reason why it is quite often used in male patients is because not only gender influences distal femoral geometry but also morphotype is an important factor. Therefore irrespective of gender, ectomorphs will have smaller ML ratios and thus will have smaller knees and will benefit from a Stature variant. Moreover we have seen that the correct use of the Stature variant can also influence our clinical scores and our percentages of ligament releases with overall better results.