Long term results with the BiCONTACT system--aspects to investigate and to learn from

[Cement-free and cemented Excia hip shaft prosthesis: comparison of intermediate term results]

AIM OF THE STUDY

For fixation of total hip prostheses, cemented and cement-free techniques are available. Normally, anchoring techniques and the definitive endoprosthesis model are determined preoperatively based on the available information, such as the quality of bone. Some newer endoprosthesis models utilize the same instruments for both implantation techniques. In this way it is possible to decide on the final anchoring technique intraoperatively. Because such a combined endoprosthesis system has been used in our clinic for 10 years, we were interested in the clinical results at the intermediate stage.

MATERIAL AND METHODS

In a prospective, non-randomized study 105 pairs from a continuing series were formed from 105 cases treated with cement-free prostheses and the latest cemented shaft implants from the same year. In this way a total of 210 hip shaft endoprostheses from the years 2002 to 2006 were included in the study. After an average time period of 6.3 years (range 4.5-8.2 years) the patients were recalled for a follow-up examination. The clinical results, early and late complications were analyzed. The immediately postoperative X-ray images and those from the follow-up examination were evaluated by an independent external expert with respect to primary positioning, migration and any signs of loosening.

RESULTS

At the follow-up examination at an average of 6.3 years the quota was 73%. The indications for cement-free/cemented total hip endoprosthesis were: primary arthritis 87%/98%, secondary arthritis 10%/2% and others 3%/0%. At the time of the last follow-up examination 4 and 14 patients, respectively, had died. The visual analog scale (VAS) for pain was given as 0.72/0.78. The Harris hip score improved from 54/48 to 93/90 points. The implant-related survival rate was 99.5%. Due to a periprosthetic fracture one of the cemented shafts had to be removed. Luxation occurred in 3/2 cases, respectively, of which 4 could be conservatively treated. In one cement-free case a head elongation and a change to an inlay with an anti-luxation shoulder was necessary. A fracture of the trochanter major was conservatively treated and an intraoperative shaft fissure was stabilized with wire cerclage and titan banding. The radiological evaluation showed no implant loosening or statistically significant differences in the shaft positioning.

DISCUSSION

Short and intermediate clinical and radiological results showed no differences in patients of similar average age in the sixth decade of life. The significant improvements in the Harris hip score and the range of movement could be confirmed in the intermediate term and are comparable to other current implants. It can be concluded that an intraoperative decision on the fixation technique based on the macroscopically visible bone quality supports the reliably good results of both methods.

Zementfreie Hüftschäfte

Optimal fixation of cementless stems is a precondition for long-lasting stability. Thus, anchorage, stabilizers, material and surface are of essential importance. To achieve primary stability, good rotational, tilting and axial stability is necessary. Stabilizers such as fins and ribs optimize stability. The CCD-angle and length of neck-axis determine the offset (laterality), leg-length and center of rotation. The stem, is responsible for the fixation of the prosthesis and for transmitting forces to the bone. The types of fixation are epiphyseal (the femoral head is covered by a cup prosthesis), metaphyseal and meta-diaphyseal (with straight or anatomically shaped monoblock-prostheses of different lengths, modular and custom-made prostheses) and diaphyseal (using predominantly modular systems). Titanium alloys are the predominate material for cementless stems. The surfaces are generally corundum-blasted or plasma sprayed. For metaphyseal and meta-diaphyseal stems, survival rates from 95 to 98% have been reached after 15 years. Diaphyseal-fixed stems have mid-term survival-rates of 92-99%.