Deficiencies of acetabular bone stock at revision hip replacement were reconstructed with two different types of allograft using impaction bone grafting and a Burch-Schneider reinforcement ring. We compared a standard frozen non-irradiated bone bank allograft (group A) with a freeze-dried irradiated bone allograft, vitalised with autologous marrow (group B). We studied 78 patients (79 hips), of whom 87% (69 hips) had type III acetabular defects according to the American Academy of Orthopaedic Surgeons classification at a mean of 31.4 months (14 to 51) after surgery. At the latest follow-up, the mean Harris hip score was 69.9 points (13.5 to 97.1) in group A and 71.0 points (11.5 to 96.5) in group B. Each hip showed evidence of trabeculation and incorporation of the allograft with no acetabular loosening.

These results suggest that the use of an acetabular reinforcement ring and a living composite of sterile allograft and autologous marrow appears to be a method of reconstructing acetabular deficiencies which gives comparable results to current forms of treatment.

The major challenges in an increasing number of periprosthetic femoral fractures are pre-existent aseptic loosening and femoral bone loss. The successful concept of interlocked intra medullarynailing of multi fragmentary femoral fractures has been applicated onperiprosthetic fractures. A specially designed revision stem combines the features of an intramedullary nail in its distal part and of an uncemented coated prosthesis in the proximal part. This prosthesis has been used successfully in elective revision surgery for aseptic loosening.

Thirty-nine patients with periprosthetic fractures have been operated between 1994 and 2000. Eleven patients were male, the mean age was 70,3 years. The series includes three intra operative fractures of the femoral shaft, in which a revision stem was applied, in the other cases the primary intervention was 10.9 years before the periprosthetic fracture. In 16 cases the shaft was loose prior to the fractures, and in 13 cases the cup was loose as well.> A modified transfemoral approach was done in any case, and long revision stem with distal interlocking was applied. The fragments were adapted to the shaft by cerclage wires, and bone grafting was done in 14 selected cases.

All patients could be followed up. In all but 4 cases the fracture was healed and the revision stem was well osteointegrated. Radiologically, the bone stock of the proximal femur was restored by means of bone grafting and fracture healing in this cases. A recurrent revisionhad to be undertaken in four cases due to lack of osteointegration and subsidence of the stem. In 5 cases the cerclage wires had to be removed due to local irritation. 3 patients had a recurrent trauma and a new periprosthetic fracture distal to the tip of the revision stem; plating had to be performed in this cases.

We conclude that interlocked intramedullary stabilisation of periprosthetic fractures with a revision stem can be a option especially in those challenging cases with pre-existent shaft loosening and bone loss.

Aim: The healing capacity of human articular cartilage is very limited in the adult. Therefore tissue engineering techniques were developed to treat cartilage lesions. To it, autologous chondrocytes are harvested from the affected joint and expanded in vitro. During expansion chondrocytes may dedifferentiate, characterized by an increase in type I collagen and a decrease in type II collagen expression. Since high expression of type II collagen is of central importance for the properties of cartilage after transplantation, we investigated if the human platelet supernatants (hPS) containing PDGF and TGF-b or recombinant human bone morphogenetic protein-2 (BMP-2) may modulate the chondrogenic phenotype in monolayer cell cultures (2D) and in three-dimensional culture (3D) systems.

Methods: Chondrocytes from articular knee cartilage of 14 individuals (mean age 36.5 6.5 years) with no history of inflammatory joint disease were isolated and expanded under GMP conditions suitable for clinical purposes. The hPS was prepared from blood of 3 donors and pooled. Cells were seeded either in 2D cultures or embedded in alginate beads (3D) in presence or absence of hPS or recombinant human BMP-2 (generous gift of Dr. Hortschansky, Jena, FRG). After two weeks in culture, cells were harvested and analysis of the chondrogenic phenotype was performed using quantitative RT-PCR, immunocytochemistry and ELISA methods.

Results: Expansion of chondrocytes in primary culture (P0) did not yield populations of dedifferentiated or hypertrophic cells. Expanding cells in first subculture (P1) resulted in spontaneous reduction of type II collagen expression and increase in type I collagen mRNA amounts. Seeding P1 chondrocytes in 3D culture significantly reduced type I collagen, BMP-4 and IL-18 and maintained high type II collagen and BMP-2 encoding mRNA (p < 0.05). Reduction of IL-1b and elevation of IL-10 mRNA were noted but were statistically not significant. Addition of BMP-2 to 2D chondrocytes had no effect on type II collagen or IL-1b mRNA amounts (p < 0.05). In alginate cultures BMP-2 induced type II collagen and reduced IL-1b mRNA amounts. In contrast, addition of hPS containing PDGF and TGF-b, promoted mitotic activity in 2D and alginate cultures. The hPS reduced in 2D cultures type II and induced type I collagen expression. Even in alginate beads induction of type I collagen was detected.

Conclusions: We conclude that the chondrogenic phenotype is stabilized by BMP-2 more effectively in alginate beads but not in monolayer cultures. The hPS promotes proliferation of chondrocytes in vitro but induces elevated type I expression, an indicator of chondrocyte dedifferentiation.

Introduction: Within the last few years numerous operative procedures have been described aiming a biological repair of damaged articular cartilage. Current techniques are: Microfracture, Osteochondral Autografting (Mosaicplasty) and Autologous Chondrocyte Transplantation (ACT).

Several new studies have shown, that the defect size plays a major role in the clinical outcome of the different procedures. Thus, it makes sense to measure the size of a cartilage defect before indicating a certain method for biological repair.

Material and Methods: We have developed a software (beta-version) for measuring the size of a cartilage defect during a routine arthroscopy in a real-time mode. The programme is based on an Infrared-Navigation tool (Orthopilot, B.Braun-Aesculap, Germany).

In order to proof the reliability and the usefulness of this device, we carried out following study: in each of 6 cadaver-knees we performed 2 full-thickness cartilage defects (MFC and LFC) of different size.

In a first run 3 surgeons had to scope the joint and estimate the defect size with means of a scaled probe-hook. In a second run we performed a measurement of the defect with the Orthopilot™; finally an open measurement after arthrotomy was done to act as reference.

Results: Measurement of the cartilage defect size was clearly superior to an estimation by probehook. Especially the inter-observer difference between the surgeons was widely spread, whereas the max. mismeasurement with the Orthopilot was 2mm.

Discussion: Our study has shown, that navigational-assisted determination of chondral defects is superior to a simple estimation of a defect size by a probehook. Considering that the defect size is a crucial point in choosing the appropriate procedure for the treatment of cartilage defects, navigation devices like the CDM-software is maybe a helpful tool in making the right decision for a suitable method of biological cartilage repair.

The treatment of fractures of the proximal tibia is complex and makes great demands on the implants used. Our study aimed to identify what levels of primary stability could be achieved with various forms of osteosynthesis in the treatment of diaphyseal fractures of the proximal tibia. Pairs of human tibiae were investigated. An unstable fracture was simulated by creating a defect at the metaphyseal-diaphyseal junction. Six implants were tested in a uniaxial testing device (Instron) using the quasi-static and displacement-controlled modes and the force-displacement curve was recorded. The movements of each fragment and of the implant were recorded video-optically (MacReflex, Qualysis). Axial deviations were evaluated at 300 N.

The results show that the nailing systems tolerated the highest forces. The lowest axial deviations in varus and valgus were also found for the nailing systems; the highest axial deviations were recorded for the buttress plate and the less invasive stabilising system (LISS). In terms of rotational displacement the LISS was better than the buttress plate.

In summary, it was found that higher loads were better tolerated by centrally placed load carriers than by eccentrically placed ones. In the case of the latter, it appears advantageous to use additive procedures for medial buttressing in the early phase.

Aims: A femoral stem design (BiCONTACT¨) for cementless þxation is being used without any technical modiþcation since 14 years. The long term results should be evaluated in this study. Methods: A consecutive series was continuously monitored in a prospective follow-up study. A survival analysis was performed, clinical results were rated according to the HARRIS Score. Results: There were 236 patients with 250 hips, mean age at time of implantation was 58.2 years. Indications for THR included osteoarthritis (62.4%), dysplasia (16.8%), trauma (8.4%) and femoral head necrosis (16.8%). Average time of follow-up evaluation was 11.8 years (range 10.6 Ð 13.7 years). At follow-up, 44 patients have died and three could not be located. Eight patients have been revised, 2 for infection, 1 for recurrent dislocation, 2 for component undersizing with rapid subsidence and 1 for aseptic loosening of a varus-malaligned stem. Two stems have been revised during acetabular revision. Survival estimate showed an overall survival of 96.6% after 14 years (conþdence limits: 98.4% (upper) and 92.8% (lower)). The average HARRIS hip score at time of follow-up was 78.3 points. Radiologically, tiny reactive lines (< 2mm) were present in the distal zones of the femoral shaft in 39%, but no radiolucencies could be found in the proximal anchoring zone. Conclusions: The long-term follow-up results with the BiCONTACT¨ femoral component are encouraging and are comparable to those of modern techniques of cementing in primary total hip arthroplasty.