Tribological considerations for a new hip system.
OBJECTIVE
This paper was initiated to evaluate a new total hip system based on cementless fixation and focusing options for different articulations within a single hip system.


METHODS
100 patients provided with the cementless Variall hip system were evaluated clinically and radiographically. The 59 female and 41 male patients were followed for a minimum of 3 years postoperative. They were clinically evaluated using the Harris Hip Score. Radiographic analysis was based on plain x-rays at the latest follow-up evaluation.


RESULTS
The evaluated patients achieved an excellent clinical result with an average Harris Hip Score of 94,3 points after an average follow-up of 42 months. The radiographic evaluation of the threaded cup did not exhibit any migration of the implant nor could we find radiolucencies. All tapered stems were radiographically stable. Due to the modified proximal design and the macrostructure an improved stem bone interface was found during the follow-up period. DISCUSSION The new cementless cup with its cylindrical threads and the spherical floor achieves an anatomic fit within the acetabulum and provides excellent primary stability. The design of the gamma inlay offers the fixation of ceramic and metal articulations without polyethylene interface. Additionally, options for conventional and cross-linked polyethylenes are available. These facts make the cup a cost-effective device. The design of the new uncemented stem guarantees a high degree of primary stability and excellent rotational stability due its rectangular cross section. This pressfit is further enhanced by the proximal macrostructure of the implant, again ensuring an excellent bond between prosthesis and bone.


CONCLUSIONS
Thanks to the versatility of all the components this comprehensive new total hip prosthesis offers many options for a long-term successful implant. Additionally, it is a cost-effective solution - an important fact of nowadays strained financial situation in public health care.
Knahr
K
K
Orthopaedic Hospital Vienna -- Speising, Vienna, Austria.
Karamat
L
L
Loho
G
G
Pospischill
M
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011859:Radiography