Total hip replacement (THR) in children and very young teenagers is experimental since we do not know long-term results in these. We investigated the clinical and radiographic outcomes of THR performed in children and teenage patients identified in the Norwegian Arthroplasty Register

We included 111 patients (132 hips) who underwent THR before 20 years of age., together with information on the primary diagnosis, types of implants, and any revisions that required implant change. Radiographs and Harris hip score (HHS) were evaluated for patients that attended clinical follow-up.

The mean age at primary THR was 17 (11–19) years, 60% were girls. Mean follow-up time was 14 (3–26) years. The 10-year survival rate after primary THR (with endpoint any revision) was 70%. Survival was better for the patients operated after 1996 (10 y 50% vs 90%). 39 patients had at least 1 revision and 16 patients had 2 or more revisions. In the latest radiographs, osteolysis and atrophy were observed in 19% and 27% of the acetabulae and 21% and 62% of the femurs, respectively. The mean HHS at the final follow-up was 83 (15–100). EQ-5DVAS was 74 (82 in normal population).

The clinical scores after THR in these young patients were acceptable, but many revisions had been performed. The bone stock in many patients was poor, which could complicate future revisions.

Introduction: C-stem is a triple taper polished femoral stem. The rationale for this design is to achieve an evenly distributed proximal loading of the cement mantle. This design is thought to enhance stability of the stem inside the mantle and lead to bone remodelling medially. There is to our knowledge no randomized trial comparing this stem to a well documented stem. We chose to compare it to the best documented stem in the Norwegian arthroplasty register, the Charnley monoblock.

Methods: 70 patients scheduled for total hip replacement were randomized to either C-stem or Charnley monoblock. All received a 22 mm stainless steel head, OGGEE cup and Palacos Cement with Gentamycin. We used a transgluteal approach in all cases. Harris and Oxford hip scores were measured preoperatively and after two years. Standard X-rays were taken postoperatively and after two years. Radiostereometry (RSA) was done postoperatively and after 3,6,12 and 24 months.

Results: There was no significant difference in Harris or Oxford hip scores after two years.

RSA after two years: (table deleted)

Discussion: Polished tapered stems are designed to sink inside the mantle. Our results confirm this theory for the C-stem. The subsidence is comparable to other collarless tapered stems with good long-term survival. For all other migrations/rotations the C-stem is as stable as the Charnley monoblock. This predicts good long-term results for this stem.

Introduction: Uncemented press fit cups function well in the medium term, but often seem to develop backside osteolysis in the long term. This study was done to compare migration and osteolysis for cups with different fixation to find out if augmentation is needed or more a risk factor.

Method: Eighty seven hips in 81 patients planned for a THA due to OA were randomised and operated with a Reflection cup inserted with under reaming and press fit. Group 1 had a porous coated cup without holes; group 2 had the same cup with additional HA coating. Group 3 had a porous coated cup with six holes and fixed with three screws; and group 4 an identical cup fixed with three pegs. Early cup stability, migration, osteolysis and function were followed over five years with RSA, x- rays and Harris hip score and the groups compared statistically.

Results: At five years the mean (SD) translation for all cups was 0.13 (0.28) mm proximally, 0.002 (0.41) mm medially, and 0.13 (0.42) mm anteriorly. The inclination increased 0.13 degrees (0.84 degrees), anteversion 0.13 degrees (0.84 degrees), and anterior tilt 0.15 degrees (0.92 degrees). There were no differences in migration between the four modes of fixation (p=0.053–0.9). An inducible displacement test of stability one week after operation showed only minor movements, below the detection limit for RSA and without group differences. Thirty-five cups had a central gap post-operatively, all disappeared within two years and did not imply either inferior fixation or radiolucencies. The HA-coated cups displayed less radiolucent lines (p=0.003) than the other groups when measured as percentage of the total interface. Most lucent lines were seen in zones 2 and 3 and developed during the initial two years. At five years, minor focal osteolytic lesions were found in 13 hips, most in cups with screws and all progressing slowly. The proximal wear was 1.02mm and the 3D wear 1.05 mm after five years, equal for the four modes of fixation and higher for young and male patients. Harris hip score was 96 at 5 and 93 at five years and equal for the groups.

Conclusion: In this study, screws and pegs did not add any stability to the already excellent fixation of cups but lead to less satisfactory interfaces. Since osteolysis is the main clinical problem and not stability, both facts suggest more cups should be used without holes, to minimise particle penetration and osteolysis.