Introduction: Treatment of hip joint disease with Total Hip Arthroplasty (THA) is in continuous evolution with new approaches, new size of components and type of bearing surfaces. Meanwhile, the analyses of proven implants continues to yeld results with a high survivor-ship and almost absent osteolysis, even with the greater wear found in the poliethylene (PE) insert of 10 to 15 year old implants. The results of these THA and the need to revise some implants not loosened but with wear of the PE, is the object of this study.

Methods: 330 non-cemented THA with the CLS expansion cup, performed by four surgeons over 15 years, are retrospectively analyzed. General anthropometric data of the studied population was obtained from medical records. Clinical elements are evaluated, among others the diagnosis, size and orientation of the components, time of partial/total weight bearing, period of crutch assisted walking, subjective patient satisfaction.

X-rays were measured for numerical assessment of the orientation of the cup, migration, radiolucent lines, osteolysis and indirect evaluation of the wear of the PE insert. Obtained data recorded over the life of the implant was computed for correlations. Other studied elements include survival rate, complication, occurrence and type of revisions.

Results: The encountered populations age was 62.7 +/− 10.9 years (Min 20, Max 86), the sex 43.1% male 56.9% female, the affected side 53.5% right 46.5% left. Charts of clinical elements, radiological measurements and correlation studies are presented. The wear of the PE insert correlates with the age of the implant and the inclination of the cup but not with radiolucent lines or osteolysis, which have a very low incidence. The complications and the survivorship analysis of the implants are presented and discussed. The encountered revision rate was 2.3% in the studied population. Without loosening, most revisions consisted on simple PE and head exchange.

Conclusions: In the authors’ opinion, the very high rate of long-term survivorship with the CLS expansion cup makes this an excellent implant for THA. Even in the 10 to 15 year old group of implants presenting greater wear of PE, there is very low presence of osteolysis and low rate of loosening, permitting to perform simple exchange of the insert and head, a simple revision procedure that will allow quick functional recovery, high patient satisfaction and a good cost/efficiency relationship.

Malfunctioning of Total Knee Replacements is often related to patella-femoral problems. As the patella groove guides the patella during flexion, the difference between anatomic- and prosthetic groove geometry may be of major influence concerning patella-femoral problems. This study focusses on the orientation or direction of the femoral patella groove, relative to the mechanical axis of the femur. Literature shows a controversy in measured groove orientation: Eckhoff et al. (1996) have measured a lateral groove, and Feinstein et al. (1996) have measured a medial groove, relative to the mechanical axis. Current femoral knee components have a lateral, or neutral directed patella groove. As most TKA surgical techniques subscribe an exorotation of the femoral component during implantation, the prosthetic in vivo situation will show a lateral groove. The objectives were to clarify the described controversy and to determine whether there is a difference in anatomic- and prosthetic groove orientation, which might cause patella-femoral problems.

The patella groove orientation of 100 human femora was measured using a 3-D measurement system. A spherical measurement probe was moved through the groove, starting at the notch and finishing at the cartilage edge, to simulate patella motion. The patella groove angle was defined as the angle between the mechanical axis and the measured groove points, in the frontal plane. A medial patella groove angle of 1.8±2.6° was measured. An implanted situation of a femoral component with neutral groove showed a lateral groove angle of 1.3°. An implanted situation of a femoral component with assymmetrical groove showed a lateral groove angle of 2.6°. The authors measured a medial oriented patella groove. This anatomical groove orientation is in contradiction with current femoral knee component design and surgical practice, because that results in a lateral oriented groove. This difference in anatomic- and prosthetic groove orientation may be a cause of patella-femoral problems.