The results of cementless hip arthroplasty with use of the first-generation Spongiosa implant were excellent at a minimum of twenty years of follow-up. The probability of survival of the acetabular component exceeded that of the femoral stem.
The objective of the study was to evaluate the precision, concordance, practicability and the early clinical outcome of the use of a computerised navigation system in a comparative study with a group of 100 patients. Two groups of 50 patients each underwent implantation of a bicondylar knee prosthesis either by means of the freehand navigation system or by means of technical instrumentation. We found that the computerised navigation system provided a higher precision than the technically instrumented implantation: 94% of the prostheses implanted with the navigation system have an alignment within a range of -3°to 3°on of the Mikulicz line. Only 46% of the patients operated by means of the technical instrumentation reached this aspired result. Furthermore, the navigation system showed smaller ranges in the deviation of the aspired alignment. The radiological and computer-modeled alignment values differed both pre-and postoperatively, but to a larger extent before surgery. The varus or valgus deviations of the axis were more distinct radiologically under the weight of the patient's body than in the computer model. The clinical outcome examined by the use of the HSS score after a mean followup of 7 months is good in both groups, and without significant differences. On average, the duration of surgery was 13 minutes longer in the computerised navigation group. We conclude that the benefit of the computerised navigation system is represented by the high improvement of precision. Achieving early clinical results identical to those in the technical instrumentation group, we expect a reduction of aseptic loosening in the computerised navigation group.
Bionic systems are aiming to integrate natural observing into mechanical solutions. This has been realized in the design of metal on metal bearing in total hip resurface arthroplasty. The articular side of the femoral cup is covered with a dimple like surface. Under laboratory condition this so called "surf-metal-cup" achieved a reduction of the mechanical wear to almost a third part in comparison to a metal-cup with plane surface. This advantage, caused by the reduced friction-coefficient due to improved hydrodynamic lubrication could also be proved under laboratory conditions. The clinical introduction is expected to offer a significant extension of durability in this prosthetic system and needs to be proved in a long-term study.
Hip resurfacing is used as an alternative option for young patients suffering from osteoarthritis. Standard implants used for resurfacing have similar designs and biomechanical properties. We present a hip resurfacing system that restores the surface with minimal bone loss and preserves the subchondral bone stock of the femoral head by reaming the surface only without any bone resection and insertion of an onlay femoral cap. This technique is performed without guide pins or the need of navigation. No stem is used in the onlay resurfacing technique. The surface of the femoral component was designed using a biosurf structure, which achieved 14% less wear by reducing metal debris and increasing lubrication because of the biosurf-structured surface. The acetabular component is a modular system, which allows easier revision if required. Low viscosity cement is used for fixation of the femoral component. A cementless acetabular cup with trabecular metal structured surface is used, which is made of titanium-niobium, hydroxylapatit coated. A highly polished insert is placed into the cementless fixated socket. We also describe a modified minimally invasive anterolateral approach with complete prevention of any muscle resection. FIGURE 3. Femoral head after reaming.FIGURE 4. Surface of the femoral component with defined dimples.www.techortho.com | 69 FIGURE 9. Femoral preparation and reaming profiles for traditional resurfacing (left) and onlay resurfacing (right).
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