Femoral Head Cartilage Research Articles

Safe Arthroscopic Access to the Central Compartment of the Hip

This technical note describes a new method that allows access to the central compartment of the hip under arthroscopic control via the peripheral compartment with less risk of labral perforation and/or cartilage scuffing. After placement of the anterolateral portal in the peripheral compartment without traction, the anterior head area with the anterior acetabular labrum and the anterior surface of the femoral head are inspected. Under arthroscopic control, a guidewire is introduced through the anterior portal in between the anterior labrum and anterior femoral head cartilage and into the central compartment. The arthroscope is then removed from the anterolateral portal, the hip distracted, and the arthroscope introduced via cannulated instruments over the guidewire into the central compartment. Further portal placement can be controlled arthroscopically.

Arthroscopic Surgery to Treat Intra-articular Type Snapping Hip

To reveal the causes of the intra-articular type snapping hip and their frequency. Case series. We studied 2 hip joints of 2 male patients and 30 hip joints of 28 female patients with snapping hip syndrome, in which the accompanying pain was transiently relieved by intra-articular injection of local anesthetic. The mean age at diagnosis was 26 years. Plain radiography, hip arthrography, magnetic resonance imaging (MRI), and arthroscopy were performed in these patients and the findings were compared. Plain radiography findings showed no abnormality in 11 joints, hip osteoarthritis in 19 joints, and femoral head deformation caused by Perthes disease and synovial osteochondromatosis in 1 joint each. Excluding the case of synovial osteochondromatosis, 31 joints were examined by MRI, which failed to identify the cause of snapping hip in all cases. Hip arthrography revealed an intra-articular loose body in 2 joints with osteoarthritis. Arthroscopy revealed acetabular labral tears in all 11 joints with no abnormalities and 15 of 19 joints with osteoarthritis on plain radiography films, and incompatibility between acetabular labrum and deformed femoral head in 2 joints with osteoarthritis. In the case of femoral head deformation after Perthes disease, arthroscopy revealed detachment of the femoral head cartilage as a result of impingement of the acetabulum on the femoral head. Arthroscopic surgeries were conducted: partial limbectomy for acetabular labral tears, surgical removal of loose bodies, partial femoral head excision for incompatibility between acetabular labrum and deformed femoral head, and shaving or articular cartilage detachment. The surgeries resolved the snapping in all cases. Acetabular labral tear was the cause of 80% of cases of intra-articular type snapping hip. Incompatibility between the acetabular labrum and a deformed femoral head was found to be a cause of intra-articular type snapping hip. Level IV, case series.

ADAMTS‐1–Knockout mice do not exhibit abnormalities in aggrecan turnover in vitro or in vivo

To determine the role of the proteinase ADAMTS-1 in normal and accelerated catabolism of aggrecan in articular and growth plate cartilage of mice. Expression of ADAMTS-1 was determined using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of RNA isolated from microdissected chondrocytes from different zones of mouse growth plate and articular cartilage. Real-time RT-PCR for ADAMTS-4, ADAMTS-5, and ADAMTS-9 was performed on femoral head cartilage of wild-type (WT) and ADAMTS-1-knockout (KO) mice. Histologic and immunohistologic evaluation of growth plate and articular cartilage was performed in WT and KO mice from birth to 12 weeks of age. The effect of ADAMTS-1 ablation on cartilage proteoglycan loss was studied in antigen-induced arthritis (AIA). Aggrecan catabolism in WT and KO mice was studied in an in vitro model of cartilage degradation, by quantitation of glycosaminoglycan loss and histologic, immunohistologic, and Western immunoblot analyses. ADAMTS-1 messenger RNA (mRNA) was expressed in normal mouse articular and growth plate cartilage and was up-regulated in terminal hypertrophic differentiation of growth plate chondrocytes. There was no difference in mRNA levels in the cartilage of WT compared with KO mice for the other potential aggrecanases ADAMTS-4, ADAMTS-5, or ADAMTS-9. ADAMTS-1-KO mice were significantly smaller than their WT littermates; however, no morphologic differences between the genotypes were evident in growth plate or articular cartilage from birth to skeletal maturity (12-16 weeks). Similarly, no difference in cartilage aggrecan content or presence of aggrecan degradation products was detected between WT and KO mice. There was no difference between WT and KO mice in the degree of synovial inflammation or depletion of cartilage aggrecan in AIA. There was no difference between WT and KO cartilage in either basal or stimulated aggrecan loss in vitro; however, subtle changes in the aggrecanase-generated aggrecan catabolites were observed in interleukin-1-treated cartilage. Although ADAMTS-1 is expressed in articular and growth plate cartilage and is able to cleave aggrecan at physiologically relevant sites, our results indicate that it does not play a significant nonredundant role in normal cartilage and bone development and growth. Similarly, ablation of ADAMTS-1 offered no protection from accelerated aggrecanolysis in an inflammatory model of arthritis or in an in vitro model of early cartilage degradation. ADAMTS-1 does not appear to be a viable target for treatment of cartilage destruction in arthritis.

Factors associated with hip cartilage volume measured by magnetic resonance imaging: The Tasmanian Older Adult Cohort Study

To compare associations between anthropometric and lifestyle factors and femoral head cartilage volume/thickness and radiographic features of osteoarthritis (OA) and to provide evidence of construct validity for magnetic resonance imaging (MRI) assessment of femoral cartilage volume and thickness. We studied a cross-sectional sample of 151 randomly selected subjects (79 men, 72 women; mean age 63 years) from the Tasmanian Older Adult Cohort Study. A sagittal T1-weighted fat-suppression MRI scan of the right hip was performed to determine femoral head cartilage volume, cartilage thickness, and size. An anteroposterior radiograph of the pelvis with weight bearing was performed and scored for radiographic evidence of OA in the right hip. Other factors measured were height, weight, leg strength, serum vitamin D levels, and bone mineral density. Hip cartilage volume was significantly associated with female sex, body mass index, and femoral head size, whereas hip cartilage thickness was significantly associated only with the size of the femoral head. Only female sex was significantly associated with the total radiographic OA score and the joint space narrowing (JSN) score, but not the osteophyte score. Radiographic JSN of the hip, especially axial JSN (but not osteophytes), was significantly correlated with hip cartilage volume and thickness. Femoral head cartilage volume and thickness have modest but significant construct validity when correlated with radiographic findings. Furthermore, the generally stronger associations with volume compared with radiographic OA suggest that MRI may be superior at identifying risk factors for hip OA.

Magnetic resonance imaging of the hip: Detection of labral and chondral abnormalities using noncontrast imaging

Traditional imaging techniques have limited ability to detect subtle chondral and labral injuries of the hip. We performed a retrospective review of patients who underwent magnetic resonance imaging (MRI) of the hip and subsequent hip arthroscopy in order to evaluate the ability of optimized, noncontrast MRI to identify tears of the acetabular labrum and defects in articular cartilage. Retrospective review of a consecutive sample. Between January 1997 and July 2000, 92 patients had MRI of the hip, followed by arthroscopic surgery of that hip by 1 of 2 surgeons (R.B., D.E.P.). Two musculoskeletal MR radiologists blinded to the initial MRI and surgical findings, independently interpreted the studies, looking for the location and degree of articular cartilage and acetabular labral pathology. Of the 92 patients studied, each of 2 radiologists correctly identified 83 (94%) and 84 (95%) of the 88 labral tears present at surgery, respectively. There was 92% interobserver agreement on the MRI studies. For articular cartilage defects on the femoral head and acetabulum, there was good agreement (92% and 86% within 1 grade) between MRI and surgical grading and between the 2 MR readers (kappa of 0.8 for femoral head cartilage and 0.7 for acetabular cartilage). This study shows that noncontrast MRI of the hip, using an optimized protocol, can noninvasively identify labral and chondral pathology. Such information may facilitate deciding which patients warrant surgical intervention, thus preserving hip arthroscopy as a therapeutic tool. Level II, Development of Diagnostic Criteria Study.

Heat-shock proteins and their role in chondrocyte protection, an application for autologous transplantation

Articular cartilage injury presents a unique therapeutic challenge. As cartilage possesses no blood or nerve supply of its own it has a particular susceptibility to early injury and a poor capacity for self-repair. Treatment options are limited and injury can eventually lead to osteoarthritis. Autologous chondrocyte transplantation is an exciting therapeutic development, but despite initial encouraging results, graft failure and formation of fibro- as opposed to hyaline cartilage remain problematic. Bleeding is an inevitable consequence of surgery, and blood-induced cartilage damage is well documented. It is hypothesised here that protecting chondrocytes against blood could significantly improve results. Heat-shock protein induction may confer chondroprotection. The expression of heat-shock proteins in human chondrocytes and rat femoral head cartilage following heat shock was analysed by Western blotting, and red-blood-cell-induced chondrocyte death was assessed by cell viability and apoptosis by flow cytometry. We demonstrate that heat-shock induced expression of heat-shock protein 70 (HSP70) (rat and human) and HSP32 (human). Blood and blood products reduced rat cartilage proteoglycan synthesis and human chondrocyte viability, and induced human chondrocyte apoptosis at concentrations considerably lower than those reported previously. The induction of HSP70 in rat cartilage was ineffective in reducing chondrocyte death in the absence or presence of red blood cells or red cell products. Heat shock to human chondrocytes reduced low levels of apoptosis (<20%) and cell death induced by low levels of blood products, but not higher levels. Induction of HSP32 with diacetylrhein appeared to be more effective and may hold greater promise. Blood has potent adverse effects on chondrocytes and the induction and chondroprotective effects of heat-shock proteins could be applied to increase the initial success of implanted chondrocytes improving the outcome of autologous chondrocyte transplantation.

Stimulation of chondrocytes in vitro by gene transfer with plasmids coding for epidermal growth factor (hEGF) and basic fibroblast growth factor (bFGF)

Human epidermal growth factor (hEGF) and basic fibroblast growth factor (bFGF) influence critical characteristics of chondrocytes. The effects on metabolism and differentiation were evaluated following transfection using specific plasmids coding for both cytokines. Chondrocytes were isolated from femoral head cartilage of patients undergoing a hip arthroplasty for femoral neck fracture. Following collagenase-digestion, cells were cultured in monolayers, and cell proliferation, glucosaminoglycan-production and collagen type II expression were monitored 10 days after isolation. Addition of recombinant hEGF and bFGF resulted in a significant increase in cell proliferation and glucosaminoglycan production. Chondrocytes were transfected with vectors coding for either hEGF or bFGF and the production of these proteins was measured in supernatants by ELISA. Expression kinetics showed different patterns: hEGF was detectable 2.5 days following transfection and peaked at day 5.5, whereas bFGF-production reached its maximum 1.5 days after transfection, declining thereafter. Chondrocytes endogenously produced significant amounts of bFGF within 5 days following isolation. Proliferation of hEGF-transfected cells increased up to 81%; bFGF-transfection caused an increase up to 76%. Similarly, glucosaminoglycan-production was enhanced up to 120% by hEGF-transfection and 37% by bFGF transfection, respectively. Collagen type II production decreased following transfection with both plasmids. Temporary in vitro gene transfer of the growth factors hEGF and bFGF provides a method to stimulate chondrocyte proliferation and induces signs of dedifferentiation, which would limit a reasonable clinical application.

Transverse relaxation mechanisms in articular cartilage

Relaxation rates in the rotating frame ( R 1 ρ ) and spin–spin relaxation rates ( R 2) were measured in articular cartilage at various orientations of cartilage layer to the static magnetic field ( B 0), at various spin locking field strengths and at two different static magnetic field strengths. It was found that R 1 ρ in the deep radial zone depended on the orientation of specimens in the magnet and decreased with increasing the spin locking field strength. In contrast, R 1 ρ values in the transitional zone were nearly independent of the specimen orientation and the spin locking field strength. Measurements of the same specimens at 2.95 and 7.05 T showed an increase of R 1 ρ and most R 2 values with increasing B 0. The inverse B 0 dependence of some R 2 values was probably due to a multicomponent character of the transverse magnetization decay. The experiments revealed that the dominant T 1 ρ and T 2 relaxation mechanism at B 0⩽3 T is a dipolar interaction due to slow anisotropic motion of water molecules in the collagen matrix. On average, the contribution of scalar relaxation due to rapid proton exchange in femoral head cartilage at 2.95 T is about 6% or less of the total R 1 ρ at the spin locking field of 1000 Hz.

An open-configuration MRI study of femoro-acetabular impingement and subluxation in extreme leg positions

It recently has been reported that femoro-acetabular impingement is a cause of hip osteoarthritis (OA) in nondysplastic hip. It has not been, however, visualized in what position femoro-acetabular impingement actually happens. It is not been known if subluxation occurs after femoro-acetabular impingement with or without symptoms. The purpose of our study is to visualize the impingement and subluxation in various sitting postures, which may give occasion to femoro-acetabular impingement. Five healthy volunteers without hip dysplasia or hip pain were the subjects of this study. Average age was 21 years. Average height was 155 cm, and average body weight was 46 kg. Spin echo images of the hip were obtained in five sitting postures (sitting straight, bowing from sitting straight, sitting cross-legged, W-sitting, squatting) which may lead to the impingement and subluxation of the femoral head, using an open-configuration MRI (SIGNA SP 0.5T, GE Medical Systems, Milwaukee WI). Oblique multiple plane reconstructed (MPR) views through the femoral head center were made on a 3D viewer software (M-view; Medical Image Laboratory, Tokyo). The impingement point was searched and the existence of the gap between acetabular and femoral head cartilage on the MPR views. No volunteers complained of hip pain in such extreme bending posture for an imaging period ranging from 10 to 14 min. Hip subluxation was observed in all volunteers in W-sitting. The anterior femoral neck impinged on the antero-lateral acetabular rim or labrum in this sitting posture. Hip subluxation was also seen in two of five volunteers in sitting cross-legged or squatting. This study clearly visualized femoro-acetabular impingement and subluxation of nondysplastic hips in some sitting postures which bended the hip extremely. Because no volunteers complained of hip pain in such extreme postures which led to impingement and subluxation of the hip, femoro-acetabular impingement may not be related to hip OA. This MRI technique is unique and can be useful to analyze the hip joint kinematics in various postures.

Telomere length, telomerase activity, and expression of human telomerase reverse transcriptase mRNA in growth plate of epiphyseal articular cartilage in femoral head during normal human development and in thanatophoric dysplasia

Telomeres are important in chromosome structure and function, protecting against their degradation. However, few studies have examined telomeres in growth plates within articular cartilage during normal development. We investigated frozen sections that were obtained from 57 reference autopsy cases (aged from 16 weeks of gestation to 91 years) and from 2 patients with thanatophoric dysplasia. In the reference cases, telomere length was significantly longer in growth plates obtained from the 10 cases that were aged from 16 weeks of gestation to 10 years than in those from 47 of the adult cases (aged 20 to 91 years). In fetal, neonatal, and child cases, telomerase activity was significantly higher in the hypertrophied zone (HZ) in growth plates than in the other 3 zones. The hTERT mRNA staining intensity (staining area) was stronger (larger) in HZ and the proliferating zone than in the calcified zone and resting zone. In thanatophoric dysplasia, telomere length and telomerase activity were short and low, respectively, compared with those of normal growth plates at an equivalent age, and expression of hTERT mRNA was negative or weakly positive in all 4 zones within growth plates. These results suggest that telomere length and telomerase activity have significant effects in the growth plates of articular cartilage, particularly at developmental ages from fetus to child. We speculate that short telomere length and low telomerase activity may be important for chondrocyte differentiation in rhizomeric shortening of the limbs in thanatophoric dysplasia.

Anti-arthritic properties of FK506 on collagen-induced arthritis in rats.

To determine the effect of FK506 (tacrolimus) on paw inflammation, TNF-alpha expression in joint, and bone and cartilage destruction in type II collagen-induced arthritis (CIA) model in rats. CIA was induced by immunization of female Lewis rats with an emulsion of bovine type II collagen and incomplete Freund's adjuvant. Paw inflammation was assessed by the increase in paw volume. Tumor necrosis factor (TNF) -alpha expression in hind knee joint was assessed by immunohistochemical analysis. Lesions of bone and cartilage were assessed on the basis of histological change in knee joint, radiographic analysis in hind paw, bone mineral density in femora and proteoglycan contents in the cartilage of femoral heads. FK506 at doses of 1, 1.8 and 3.2 mg/kg or its placebo formulation was orally administered to rats for 28 days from the day after immunization (n = 10). Effect of FK506 was compared with that of vehicle (distilled water). FK506 at a dose of 1.8 mg/kg significantly suppressed paw swelling (p < 0.01) and histological change in knee joint (p < 0.05). Tumor necrosis factor (TNF)-alpha was mainly expressed in the region with a marked infiltration of inflammatory cells in the hind knee joint. FK506 (3.2 mg/kg) markedly reduced TNF-alpha expression. FK506 at a dose of 1.8 mg/kg suppressed radiographic changes in hind paw (p < 0.05) and also recovered the decrease in bone mineral density in the femora (p < 0.05). Proteoglycan contents in the cartilage of femoral heads were determined to evaluate the cartilage destruction more quantitatively and found to significantly decrease in CIA rats. FK506 at a dose of 1.8 mg/kg recovered the loss of proteoglycan contents (p < 0.01). These results show that FK506 is effective in suppressing inflammation, TNF-alpha expression in joint, and damage to bone and cartilage in rat CIA, and may be useful in the treatment of rheumatoid arthritis.

Increased presence of cells with multiple elongated processes in osteoarthritic femoral head cartilage

Objective: This study examined the morphology of chondrocytes in articular cartilage from osteoarthritic (OA) and non-OA human femoral heads and in particular the appearance of a sub-population of cells with multiple elongated processes radiating up to 30 μm into the extracellular matrix. Methods: Cartilage explants were removed from 8 anatomical sites over the surface of OA ( n=6) and non-OA ( n=5) femoral heads. Cells were labeled for vimentin intermediate filaments and visualized using epi-fluorescence and confocal microscopy. The percentage of cells with elongated processes was correlated with macroscopic and histological indicators of osteoarthritis. Results: Cells with processes accounted for less than 10% of the total cell population in non-OA cartilage. By contrast, in the peripheral regions of the OA femoral head these cells accounted for 20–45% of the total cell population, the differences being statistically significant. These peripheral areas are habitually non-load bearing and were also the most likely to show gross fibrillation and pannus formation. A statistically significant correlation was demonstrated between the percentage of cells with processes and the histological extent of the OA degradation, quantified in terms of the Mankin score. Conclusions: The extension of cell processes, which may be associated with localized breakdown of the pericellular matrix, will undoubtedly alter numerous aspects of cell function including phenotypic expression and mechanotransduction. Hence these significant changes in chondrocyte morphology are likely to have important implications for the aetiology of osteoarthritis and the development of potential treatment strategies.

Acetabular rim degeneration: a constant finding in the aged hip.

During recent years the acetabular labrum has gained increased interest because its degeneration frequently is found in association with early osteoarthritis of the hip. To determine spatial distribution of labral degeneration in the aged hip and to identify the pathologic features triggering this event, an anatomic postmortem and an intraoperative in vivo study were done in 30 cadavers (range, 60-90 years) and in 18 elderly patients (range, 69-97 years) who had hemiarthroplasty for displaced femoral neck fractures. In both groups, no gross anatomic or radiographic abnormalities suggesting advanced osteoarthritis were present. All cadaveric acetabuli (30 of 30) revealed labrum and cartilage damage. Labrum damage (17 of 18) and cartilage lesions (16 of 18) occurred less frequently and were smaller in the elderly patients. Peripheral joint degeneration was most frequent at the superior acetabular rim close to the anterior inferior iliac spine. More centrally localized cartilage lesions were present in 47% of cadavers and in 28% of patients. The majority of femurs (cadavers) (80%) showed reduced narrowing at the anteromedial femoral head-neck junction causing impingement against the corresponding acetabular rim or squeezing of this area into the joint during flexion, whereas the femoral head cartilage appeared normal in all but one hip. Acetabular rim degeneration is a constant finding in the aged hip, which seems to be triggered by femoroacetabular impingement.

Early osteoarthritic changes of human femoral head cartilage subsequent to femoro-acetabular impingement

Objective: To use the surgical samples of patients with femoro-acetabular impingement due to a nonspherical head to analyze tissue morphology and early cartilage changes in a mechanical model of hip osteoarthritis (OA). Design: An aberrant nonspherical shape of the femoral head has been assumed to cause an abutment conflict (impingement mechanism) of the hip with subsequent cartilage lesions of the acetabular rim and surface alterations of the nonspherical portion of the head. In this study, 22 samples of the nonspherical portions of the head have been obtained during hip surgery from young adults (mean 30.4 years, range 19–45 years) with an impingement conflict. The samples were first compared with tissue from the same area obtained from six age-matched deceased persons (control group) with normal hip morphology and second with cartilage from 14 older patients with advanced OA. All samples were characterized histologically and hyaline cartilage was graded according to the Mankin criteria. They were further subjected to examination on a molecular basis by immunohistology for cartilage oligomeric matrix protein (COMP), tenascin-C and a collagenase cleavage product (COL2-3/4C long) and by in situ hybridization for collagen type I and collagen type II. Results: All samples from the patient group revealed hyaline cartilage with degenerative signs. According to the Mankin criteria, the cartilage alterations were significantly different when compared with the control group ( p=0.007) but were less distinct when compared with cartilage from patients with advanced OA ( p=0.014). Positive staining and distribution pattern for COMP, tenascin-C and COL2-3/4C longshowed similarities between the samples from the impingement group and osteoarthritic cartilage but they were distinctly different when compared with healthy cartilage. Levels of collagen I and II transcripts were upregulated in 6 and 10, respectively, of the 14 samples with OA and in 9 and 12, respectively, of the 22 samples from the impingement group. None of the samples from the control group showed upregulation of Collagen I and II mRNA. Conclusions: The aberrant nonspherical portion of the femoral head in young patients with an impingement conflict consists of hyaline cartilage which shows clear degenerative signs similar to the findings in osteoarthritic cartilage. The tissue alterations are distinctly different when compared with a control group, which substantiates an impingement conflict as an early mechanism for degeneration at the hip joint periphery.

Temporal dynamic changes in synthesis of chondroitin sulfate isomers in canine articular chondrocyte culture.

To investigate temporal dynamic changes in the synthesis of chondroitin 6-sulfate (CS6) and chondroitin 4-sulfate (CS4) in vitro, normal articular cartilage of femoral heads was harvested from three dogs. Chondrocytes were isolated and cultured in alginate microspheres for 21 days. On days 7, 14 and 21, DNA content was quantified by fluorometric assay using Hoechst 33258. On days 14 and 21, proteoglycans were extracted, and the amounts of CS6 and CS4 were quantified after chondroitinase ABC digestion using capillary electrophoresis. The DNA content and amounts of CS6 and CS4 increased during the culture period. The amounts of CS6 and CS4 divided by DNA content revealed that the synthesis of CS6 was more up-regulated than CS4.

Phenotypic differences in murine chondrocyte cell lines derived from mature articular cartilage

Objective To obtain well characterized immortalized murine chondrocyte cell lines. The cell lines were obtained from mature articular chondrocytes, instead of embryonal cells which are used in most other studies.Methods Pieces of articular cartilage were cut from murine patellae and femoral heads. Chondrocytes were isolated by digestion with collagenase. These cells were cultured in monolayer and immortalized by transfection of the SV40 large T antigen gene. To preserve the differentiated phenotype, the resulting clones were cultured in three-dimensional carriers, alginate beads. The phenotypes of the cells were characterized using the following parameters: Cell morphology (light microscopy), messenger RNA (RT-PCR) and protein (immunohistochemistry) levels of extracellular matrix molecules. Moreover, responsiveness to interleukin-1(IL-1) was determined by measuring production of proteoglycans (35S-sulfate incorporation) and of nitric oxide (Griess reaction).Results Sixteen clones were obtained, ten (P1 to P10) derived from patellar cartilage, and six (H1 to H6) from femoral head cartilage. In seven cell lines (P2, P5, H1, H3, H4, H5, H6) high production of type II collagen corresponded with high levels of mRNA of type II collagen (and prevalence of the IIB type) and with high IL-1-induced suppression of proteoglycan synthesis. Like intact murine articular cartilage, all cell lines produced type I and type X collagens, but mRNA levels of both types of collagen were never higher in the cell lines as compared with intact cartilage.Conclusion Our results demonstrate that it is possible to immortalize mature murine articular chondrocytes. Each of the obtained chondrocyte cell lines appeared to have a stable phenotype. Both relatively differentiated and relatively dedifferentiated chondrocyte cell lines could be identified. Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved.

Tissue inhibitor of metalloproteinases‐4 (TIMP‐4) gene expression is increased in human osteoarthritic femoral head cartilage

Tissue inhibitor of metalloproteinases-4 (TIMP-4), the newest member of the TIMP family, blocks the activities of several matrix metalloproteinases (MMPs) implicated in the arthritic cartilage erosion. By utilizing semi-quantitative RT-PCR, immunoblotting, and immunohistochemistry, we investigated whether the TIMP-4 gene is expressed in human non-arthritic and osteoarthritic (OA) cartilage. Directly analyzed femoral head cartilage showed TIMP-4 RNA expression in 2 of 9 non-arthritic and 12 of 14 OA patients. Femoral head cartilage from 6 of 9 OA patients had elevated TIMP-4 protein compared to the low-level expression in 3 of 8 non-arthritic controls. In most patients, there was correlation between TIMP-4 RNA and protein expression. TIMP-4 protein was also detected immunohistochemically in the upper zone of OA cartilage. The widespread TIMP-4 RNA and protein expression and augmentation in femoral OA cartilage suggests its important role in joint tissue remodeling and pathogenesis of OA. Increased TIMP levels in arthritic cartilage may not be a sufficiently effective defense against cartilage resorption by excessive multiple MMPs and aggrecanases.

Early lesions of the labrum and acetabular cartilage in osteonecrosis of the femoral head

Osteonecrosis of the femoral head can be caused by a variety of disorders and affects the relatively young patient. Most studies have concentrated on the femoral changes; the sites of early lesions of the labrum and acetabular cartilage have not been recorded. We studied 17 hips with osteonecrosis and a wide congruent joint space on radiographs and by direct inspection of the femoral head, labrum and acetabular cartilage during surgery. All of the femoral heads had some anterosuperior flattening which reduced the head-neck ratio in this area. A consistent pattern of damage to the labrum and the acetabular cartilage was seen in all hips. Intraoperatively, impingement and the cam-effect with its spatial correlation with lesions of the labrum and acetabular cartilage were observed. These findings could be helpful when undertaking conservative surgery for osteonecrosis, since the recognition of early radiologically undetectable acetabular lesions may require modification of the surgical technique.

Early lesions of the labrum and acetabular cartilage in osteonecrosis of the femoral head.

Osteonecrosis of the femoral head can be caused by a variety of disorders and affects the relatively young patient. Most studies have concentrated on the femoral changes; the sites of early lesions of the labrum and acetabular cartilage have not been recorded. We studied 17 hips with osteonecrosis and a wide congruent joint space on radiographs and by direct inspection of the femoral head, labrum and acetabular cartilage during surgery. All of the femoral heads had some anterosuperior flattening which reduced the head-neck ratio in this area. A consistent pattern of damage to the labrum and the acetabular cartilage was seen in all hips. Intraoperatively, impingement and the cam-effect with its spatial correlation with lesions of the labrum and acetabular cartilage were observed. These findings could be helpful when undertaking conservative surgery for osteonecrosis, since the recognition of early radiologically undetectable acetabular lesions may require modification of the surgical technique.

Development of a hybrid finite element model for individual simulation of intertrochanteric osteotomies

Intertrochanteric osteotomies of the proximal femur are used to improve the anatomy and function of the hip joint in a number of orthopaedic diseases. To investigate the geometrical and biomechanical aspects of pre-operative planning we created a set of programs to automatically perform a simulation of intertrochanteric osteotomies on a three-dimensional finite element model of the human proximal femur based on computed tomography (CT) data and using uniform brick-shaped elements. To eliminate artefacts resulting from the rough surface of the brick elements, the femoral head was represented by a tetrahedron-based head that included a cartilage layer and a subchondral cortical zone. Applicability of the procedure was tested by performing a parametric study using a model created from CT scans taken in vivo, by applying individually calculated force conditions for the one-leg stance situation. We found a large influence of osteotomy angle on the observed stress in the femoral head cartilage, especially in a situation with insufficient containment of the femoral head. The model presented here is a biomechanical tool to simulate intertrochanteric osteotomies patient-specifically for a better understanding of the effects of such operations in the individual case. The open design of the described programs allows future interfacing with surgical navigation and robot systems.