Osteoarthritic (OA) chondrocytes are metabolically active, displaying increased synthesis of type II collagen. Here, we show by immunohistochemistry and polymerase chain reaction that in comparison with healthy cartilage, OA articular chondrocytes exhibit increased in vivo synthesis of collagen prolyl-4-hydroxylase type II, a pivotal enzyme in collagen triple helix formation. Exposure of primary human articular chondrocytes to 1% oxygen enhanced accumulation of native type II collagen and stabilized hypoxia-inducible factor-1␣ (HIF-1␣). This effect was abolished by addition of the HIF-1 inhibitor 2-methoxyestradiol. Real-time polymerase chain reaction analyses of mRNAs from these cultures revealed increased transcript levels of both ␣-subunits of prolyl-4-hydroxylase (P4HA1, ϳ2-fold; P4HA2, ϳ2.3-fold) and of classical HIF-1 target genes (glucosetransporter-1, ϳ2.1-fold; phosphoglyceratekinase-1, ϳ2.2-fold). Treatment of hypoxic chondrocytes with 2-methoxyestradiol reduced transcriptional activity of HIF-1 and synthesis of ␣(II), and to a lesser extent ␣(I), subunits of collagen prolyl-4-hydroxylases. mRNA levels of type II collagen (Col2A1) and the ␤-subunit (P4HB) of prolyl-4-hydroxylase, however, displayed only modest changes at 1% oxygen. From these results and our in vivo data, we inferred that besides increased Articular hyaline cartilage is the most important component in synovial joints for frictionless joint motion. During movement, the articular cartilage is compressed by load and is then able to recover from this deformity. These unique biomechanical properties depend on the specific zonal architecture of articular cartilage as well as the extracellular matrix (ECM), which consists of two phases: solid and fluid phases. The main ECM components are proteoglycans, glycoproteins, and collagens, mainly type II collagen.1-3 Type II collagen is synthesized as a procollagen molecule with noncollagenous amino and carboxy extension peptides, by articular chondrocytes which represent the only living elements within hyaline cartilage. 4 Large type II collagen fibrils form a network with embedded proteoglycans, glycoproteins, water, and soluble ions. Since this collagen network is established in adults, the half-life of collagens is estimated to be over decades.Proper function of a load-bearing joint depends on the structural integrity of this highly specialized cartilage tissue and its ability to absorb and respond to mechanical stress. During the course of osteoarthritis, increased degradation processes of the ECM by mechanical factors as well as activity of metalloproteinases and aggrecanases have been observed. 5,6 Ultimately, destruction of large parts of the collagen network and ion-binding capacity via loss of negatively charged proteoglycans lead to a significantly decreased water-binding capability of the ECM. These biochemical changes are responsible for the devel-

The CLS((R)) Spotorno stem allows excellent long-term results in cementless hip arthroplasty, leaving only minimal options for substantial improvements. Our findings on progressive stress shielding point towards a more diaphyseal load transfer of the CLS stem.

In conclusion, the periacetabular bone density measurement as conducted in this CT study is a new reproducible method for in vivo evaluation of cortical and cancellous pelvic bone after cemented and uncemented acetabular cup implantation. In vivo CT measurements will allow a thorough assessment of periacetabular stress-shielding phenomena.

In a previous radiostereometric analysis (RSA) of the Lubinus SP II (Link, Hamburg, Germany), which is one of the most often used cemented hip stems worldwide, our research group detected a very small but statistically significant distal migration of -0.03±0.17 mm 2 years after surgery compared to the postoperative radiograph. Maximum subsidence occurred between 6 and 12 months. The implant appeared to have stabilized after 2 years. The mean value of maximum total point motion (MTPM) was 0.99±0.69 mm, which was detected 2 years after surgery. The purpose of this study was to analyze the migration pattern and to verify the predictive value of short-term RSA of the Lubinus SP II stem after 10 years. After a follow-up of 5 and 10 years, 38 and 27 out of 100 patients remained available for further assessment, respectively. No statistically significant implant translation or rotation was found along or about the axes of the global coordinate system 5 and 10 years after surgery with respect to the postoperative radiograph. Furthermore, the MTPM was stable in both follow-up periods. The results suggest that the Lubinus SP II hip stem is still stable 10 years after surgery, supporting that determining prognosis by short-term RSA follow-up of 2 years could be an appropriate tool for appraisal of implant behavior 10 years after surgery.

The rough-blasted threaded Weill cup provides a good long-term performance in cementless total hip arthroplasty. The results compare favourably to the smooth threaded cup design.