Treating osteoarthritis of the hip in patients with an altered anatomy is technically more challenging when using standard implants. Such an altered anatomy is observed in patients with congenital dyplasia of the hip (CDH), in patients with a severe varus position of the femoral neck, an increased antetorsion or a narrow medullary canal. Two-dimensional [, ] and three-dimensional analyses in an Asian [ , ] and Caucasian [ ] CDH population further demonstrated a straight femur with a distalized anterior femoral bow, making it even more difficult to fit a standard implant in the femoral canal in these particular cases.
Both Charnley and Harris developed special cemented CDH stems to address the difficulties faced in this specific patient group. Recently, long-term results were published showing a 20-year survival rate with aseptic loosening as the endpoint in 63% of the Charnley and in 78% of the Harris CDH stem . Excellent results have been reported for the small variant of the Exeter stem for patient with small femurs [ ]. Good long-term survival rates in CDH patients have also been reported for uncemented [ ] and modular stem designs [ ] with survival rates of 96% after 12 years and 97% after 8-year follow-up, respectively.
In hip arthroplasty, the original Müller straight stem is one of the most common implanted cemented straight stems with excellent long-term results [, , , ]. The cemented Müller CDH stem belongs to the same implant series. Appropriate indications for its usage amongst others are hip joints with small and hypoplastic bony anatomy with narrow femoral canals as well as osteoarthritis secondary to congenital or childhood disorders of the hip. However, up to now, no data are available showing its long-term outcome.
The aim of this study was to analyze long-term survival, identify potential risk factors for aseptic loosening, and analyze radiological outcome of the cemented Müller CDH stems.