Introduction: Hip simulator tests, analyses of retrieved components as well as radiostereometric measurements revealed that cups made of highly linked polyethylene show a much better wear performance than cups of conventional polyethylene. However, to the best of our knowledge, histomorphological studies of tissues from the surrounding of highly cross – linked polyethylene components have not been reported yet. The aim of this study was to examine such tissues for particles, released from highly cross – linked polyethylene cups and to compare the findings with those of conventional polyethylene.

Material and methods: So far, periprosthetic tissues retrieved at revisions of 11 total hip endoprostheses with highly cross – linked polyethylene cups could be analysed. The revisions became necessary 3 to 50 months after implantation because of cup loosening (4), stem loosening (1), infection (3), periprosthetic fracture of the femur (1), multiple dislocations (1) and periarticular ossification (1). The findings were compared with those of 5 artificial joints (2 ABG, 2 Müller Cup older design, 1 Metalback pressfit) with conventional polyethylene cups and 54 to 231 months of function. 5 μm sections were made from the tissues and conventionally stained with HE and van Gieson. Morphometric measurements were done using objectives 10 and 40 of an Olympus microscope and the ‘Analysis’ program of Soft Ware Imaging GmbH. In the Durasul TM – cases, the total amount and the total area of particles were ascertained while in the cases used for comparison only random CX 40 samples could be measured because of the much higher content of particles.

Results: The DurasulTM cases showed in contrast to the cases with conventional polyethylene cups, no distinct foreign body reaction. In four of the DurasulTM cases no particles could be detected at all and in the remaining seven particles could be found only in a few areas. Their number per section was between 6 and 1208, their total area per mm² section ranged between 0,03 and 6,99 × 10 5.mm² In the conventional polyethylene cases the number of particles per section was between 2832 and 71447, their total area per mm² section ranged between 1,06 and 25,91 × 10 3mm²! The average size of the DurasulTM particles was clearly bigger than the size of the conventional Polyethylene.

Discussion: The measurements in tissues of early revisions show that DurasulTM releases much less particles into the surrounding than PE and cause rather no foreign body reaction. Accordingly, the burden of the tissue with polyethylene debris is much lower while the particle size is bigger with DurasulTM than with PE.

Introduction: Improved treatment of primary tumors leads to an increased life expectancy and thus to an increasing number of patients with bone metastases. Techniques like auto- or allogenic bone grafts, vascularised bone transfer and distraction osteogenesis often require multistage surgical procedures and inhibit full early limb function. Diaphyseal replacement using nails, plates and bone cement do not guarantee long term bone stability. Due to this experiences a new diaphyseal replacement device for humerus, femur and tibia has been developed.

Materials and Methods: The diaphyseal replacement implant OSTEOBRIDGE^™ consists of two semi-circular cylindrical shells. The spacer is clamped around two nails via eight screws. Different sizes of spacers and nails can be used to bridge the bone loss correctly.

The outer diameter of the spacer ranges from 20–25–30 mm and the length from 40 to 70 mm. Two or three spacers can be combined via a special connector. Nails in the length 60 to 200 mm and the Ø 7 to 18 mm with the possibility of static or dynamic interlocking complete the modular system entirely made from Ti-6Al-4V.

Biomechanical Testing: Static compression tests to determine the maximum longitudinal forces of the clamp connection spacer/nail were performed, 4-point bending tests with the complete system to investigate the fatigue resistance were undertaken and torsional test to evaluate the rotational stability.

Prospectiv clinical evaluation: In between 2004 and 2006 35 patients were treated with the OSTEO-BRIDGE^™ system.

The indication: Tumor: Humerus 8, Femur 16, Tibia 2, Postinfectious: Tibia 4, Posttramatic Femur 4, Tibia 2.

Results:

Biomechanical testing: the clamp connection spacer/ nail can neutralize axial loads which can not be expected in human beings. The clamp connection spacer/nail Ø 10 mm resisted an average axial load of 8,5 kN. This can be compared to a force of 850 kN (equivalent to 10 multiples of 85 kg body weight). The bending test with a nail Ø 10 mm shows that the spacer can resist long term loads from an occurring stress of 400 N/mm² in the nail.

One spacer was removed during amputation for recurrency of osteosarcoma. No infection, no loosing were reported.

Discussion: The OSTEOBRIDGE^™ spacer system allows to replace lost daiphyseal bone over long distances with proved biomechanical stability. An advantage seems to be the early bony bridging over the spacer within the first 9 months. There might be another advantage in using the spacer as a container for antitumor, bactericidal or bone growth stimulating drugs.

Aims: Hipsimulator tests with highly cross-linked PE shows excellent results after 20 million cycles. Since March 99 we implanted hips with the Fitmore-Cup, Durasul-Inlay and an anatomical stem. In vivo investigations with 300 hips with highly cross-linked PE are introduced. Methods:. We used three methods to test the highly cross-linked PE in vivo: With Polyware-edge-detection we measured the penetration-rate of the Durasul ball-head.

With electron scan microscopy we measured the wear rate in 5 retrierals.

Histological examination of the periprosthetic tissue in 5 retrievals were done.

Results: 1. The linear penetration rate after 1 year is 0,42 mm and after 2 years 0,096 mm.

2. Surface investigation shows no wear in the 5 retrieval cases.

3. Histological examination revealed extremely low depostion of smallest polyethylene particules.

Conclusions:Now we have 3 years clinical experience with highly cross-linked PE. 3D-penetration results are as expected: we see no significant difference between conventional-PE and highly cross-linked PE (bedding in and creep). Surface investigation confirm the plastic deformation and the wear resistence of highly cross-linked PE. Histological examination shows ultra low depostion of PE particles and confirm the excellent in vitro results with highly cross-linked PE. The clinical investigation will be continued.