L Karamat | PubMed Health

PubMed2005

Tribological considerations for a new hip system.

PURPOSE OF THE STUDY: 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. MATERIAL AND 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. CONCLUSION: 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.

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[Risk factors for dislocation of a cementless total hip endoprosthesis--a statistical analysis].

AIM: This retrospective study aimed at the statistical identification of risk factors for dislocation for a certain cementless hip endoprothesis. MATERIAL AND METHOD: At our department 2605 primary total hip arthroplasties were performed between 1987 and 1997. In 40 patients (1.5%) a dislocation occurred. These patients were compared with a control group matched in number. RESULTS: No difference was found in both groups with respect to age, height, weight, body-mass index, and diagnosis. A tendency was found that more males were involved in the dislocation group. There were more previous operations found in this group (p = 0.005). Also significant was the fact, that patients in the dislocation group more often had epidural anaesthesia (p = 0.02), more often the implantation of the smaller 28-mm head (vs. 32 mm) (p = 0.02), and a higher inclination angle of the acetabular component (p = 0.02). No difference was found in terms of the surgeons experience, the postoperative leg length, femoral offset, medialisation, cranialisation and antetorsion of the acetabular component. CONCLUSION: Dislocation after total hip arthroplasty is a multifactorial complication. With the use of the Alloclassic/Zweymüller total hip endoprothesis, a higher risk for dislocation was found for patients with previous hip surgery, the use of the smaller endoprosthesis head, a high acetabular inclination angle, and in the use of epidural anaesthesia.

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