Introduction Debonding at the cement-prosthesis interface leading to stem movement and abrasion, has been proposed as initiating events in aseptic loosening of cemented total hip arthroplasties. A polished tapered or an absolutely stable stem possibly minimises this risk. This study evaluated a cemented, precoated femoral stem for stable fixation.

Methods The study included 24 patients, mean age of 64 years (48 to 78) undergoing single total hip arthroplasty for osteoarthritis. All were treated with cemented Definition (Stryker) stems which are straight, chromium-cobalt, with an integrated proximal polymethylmethacrylate mantle. One surgeon using fourth generation cementation techniques performed all surgeries. UHMWPE cups and Zirconia heads were used. At the time of surgery, tantalum markers were inserted into the femur, cement and stem for Radiostereometric analysis (RSA) of migration. Measurements were performed at two, 12 and 24 months intervals. Standard radiographs and Harris Hip Scores were obtained post-operatively and at two years.

Results During the first two years post-operatively the stems were shown to be absolutely fixed within the cement mantle and the mantle itself stable with the femur. At two years the mean subsidence of the stem in relation to the femur was 0.00 mm (SD 0.1), while the cement mantle subsided 0.2 mm (SD 0.2) in relation to the femur. The femoral head mean rotation was 0.02 retroversion. Postoperative radiolucent lines of > 1 mm where present in a mean of 1.4% (0 to 5%) of the cement-bone interfaces. This remained unchanged at two years (0 to 3%). Stems were in average positioned 0.8 in varus (1.2 valgus to 4.0 varus). Harris Hip Scores improved from a mean of 46 (23 to 68) pre-operatively to 93 (57 to 100) at two years.

Conclusions This is the first stem where no migration could be detected during the first two years. These results so far indicate good long-term performance of this precoated stem.

Aim: A debonding in the stem-cement interface is often the þrst event leading to clinical failure of hip prostheses. We have tested the stability of a pre cement mantled stem were the concept of composite beam stems is taken to a new level. Methods: Twenty four patients with a mean age of 64 years (48–73), a weight of 72 kg and allocated to total hip arthroplasty due to OA were operated. All received a Deþnition stem (a straight CoCr stem proximally coated with a PMMA mantle). All poly cups, Palacos cement and 4th generation cementing technique was used in all. Tantalum markers were inserted in femur and the stem and migration measured with RSA at 2, 12 and 24 months. Radiographs and Harris hip score was obtained post op and at 2 years. Results: The subsidence of stems in relation to femur was 0.00 mm (SEM 0.02) and the cement mantle subsided 0.2 mm (SEM 0.02) in relation to femur. The femoral head rotated backward 0.02 mm.(SEM 0.07) Post op radiolucent lines of 1 mm thickness or more were present to a mean of 0.3% (0–3%) in the cement-bone interface at 2 years. Harris hip score increased from a mean of 46 (23–68) pre op to 93 (57–100) at 2 years. Conclusion: Deþnition is the þrst stem investigated with RSA were no migration at all could be recorded the þrst 2 years. Togeher with a stable cement mantle and no radiolucent lines it so far indicates a good long term performance of the Deþnition stem.

Aims: Comparing periprosthetic bone remodeling in 5 stem designs and the effects of the bone remodeling on stem migration. Methods: Bone remodeling at the proximal femur in 89 cemented THA of 5 stem designs (Exeter,Sp2_aluminum,Sp2_CoCr,SHP,Spectron) were followed up at 1 week, 2 years, and 5 years postoperatively by measuring bone mineral density (BMD) in 7 Gruen zones using dual energy x-ray absorptiometer (DEXA). The migrations of the femoral stem measured by Radiostereometric Analysis (RSA) during the same time period were compared with the changes in BMD. Results: An 8% to 25% decrease in BMD at the proximal femur, especially at the medial cortex, was found 5 years after cemented THA. Exeter showed the most favourable bone remodeling, whereas the SHP and Sp2_CoCr stems showed the worst bone remodeling (with bone loss of 15–27%), and the bone loss in Sp2_aluminum and Spectron stems were between (8–13%). The majority of the bone loss occurred within 2 years without major progress thereafter. The rate of the bone loss was significantly related to the design of the stem as well as gender and body mass index (BMI). A significant relation between the rate of bone loss and the migration of the femoral stem could not be established by the current study. Conclusions: The stiffness of the stem as well as the concept of stem design significantly affected the bone remodeling at the proximal femur. However, the rate of bone loss seemingly did not affect the migration of the femoral stem in the current study.