[Conception and first results of the Spiron cementless femoral neck screw prosthesis]

The Spiron cementless femoral neck prosthesis is based on the idea of proximal force transmission. The concept of osseous anchorages has been proven successful various times. The prosthesis is a conical, self-cutting screw that is inserted without cement into the prepared subcapital implant bearing. It is produced from a corundum blasted titanium-vanadium alloy and is covered with a second-generation calcium phosphate coating. The coating and the form of the thread increase the implant's surface and help to optimize osseointegration. From February 2003 to April 2003, 38 Spiron prostheses were implanted at the DRK hospital in Neuwied (Germany) in 34 patients. Four patients received it for the replacement of both hip joints. The average age of the patients was 60.1 years at the time of the implantation (43-73 years); 20 male and 14 female patients received the prosthesis. We implanted 19 left-sided and 19 right-sided arthroplasties. The preoperative Harris hip score (HHS) was 51 (24-76), n=38. After 1 year, HHS(1) was 94 (86-100), n=20 (of 23 implants). Until now, we have not discovered any prosthesis-specific complications; the rehabilitation time shows a tendency to be shorter than after stem arthroplasty. Revision was necessary in one case because of an early infection. After 3 months, the radiological follow-up examinations showed the development of increasing trabecular reinforcement of the femoral neck and pertrochanteric regions. Until now, there is no evidence of any varus tendency of the Spiron prosthesis.