The curved shape of the stem enables it to finds its way into the femoral canal, where it adapts perfectly to the anatomy.6 This means that stress peaks, as occur with three-point locking of straight shafts, are avoided and the stem has greater rotational stability.2
Developed in 1978, and available with a modular prosthesis head since 1984, this femoral stem was a great success and had a major influence on the principle of the anatomical hip prosthesis.1 The S‑shaped curvature, which follows the natural anatomy of the femur, has proved highly successful in this system. This has been repeatedly confirmed over the last 40 years in numerous publications, including the Swedish Hip Arthroplasty Register.1, 3 The outstanding clinical history was the reason for developing the SP-CL, based on the same principle.
The anatomical shape of the stem enables it to fit centrally in the medullary canal. This helps to ensure a uniform cement coating, which can envelop the implant optimally.7 At the same time, anteroposterior and mediolateral ribs contribute to rotational stability.2, 8, 9, 10
The SP II offers a system with great modularity. The multiplicity of possible variations in CCD angle, neck length, and stem length gives maximum flexibility for reconstruction of the anatomical structures in primary and revision arthroplasties. The stem tip is curved on the lateral side in order to prevent impacts when it is introduced into the medullary canal. The slender stem design meets all the requirements for minimally invasive, soft tissue, and bone-conserving implantation.
Many long-term outcomes with survival rates of up to 92.3 percent after 23 years emphasize the success and great reliability of the SP II Stem.1
* www.odep.org.uk; Orthopaedic Data Evaluation Panel