Increased conditional risk of recurring complications with contralateral total hip arthroplasty surgery.

AIMS: Increasingly, patients with bilateral hip arthritis wish to undergo staged total hip arthroplasty (THA). With the rise in demand for arthroplasty, perioperative risk assessment and counselling is crucial for shared decision making. However, it is unknown if complications that occur after a unilateral hip arthroplasty predict complications following surgery of the contralateral hip. PATIENTS AND METHODS: We used nationwide linked discharge data from the Healthcare Cost and Utilization Project between 2005 and 2014 to analyze the incidence and recurrence of complications following the first- and second-stage operations in staged bilateral total hip arthroplasty (BTHAs). Complications included perioperative medical adverse events within 30 to 60 days, and infection and mechanical complications within one year. Conditional probabilities and odds ratios (ORs) were calculated to determine whether experiencing a complication after the first stage of surgery increased the risk of developing the same complication after the second stage. RESULTS: A total of 13 829 patients (5790 men and 8039 women) who underwent staged BTHAs were analyzed. The mean age at first operation was 62.9 years (14 to 95). For eight of the 12 outcomes evaluated, patients who experienced the outcome following the first arthroplasty had a significantly increased probability and odds of developing that same complication following the second arthroplasty, compared with those who did not experience the complication after the first surgery. This was true for digestive complications (OR 25.67, 95% confidence interval (CI) 13.86 to 46.08; p < 0.001), urinary complications (OR 6.48, 95% CI 1.7 to 20.73; p = 0.01), haematoma (OR 12.17, 95% CI 4.55 to 31.14; p < 0.001), deep vein thrombosis (OR 4.82, 95% CI 2.34 to 9.65; p < 0.001), pulmonary embolism (OR 12.03, 95% CI 2.02 to 46.77; p = 0.01), deep hip infection (OR 534.21, 95% CI 314.96 to 909.25; p < 0.001), superficial hip infection (OR 1574.99, 95% CI 269.83 to 9291.81; p < 0.001), and mechanical malfunction (OR 117.49, 95% CI 91.55 to 150.34; p < 0.001). CONCLUSION: The occurrence of certain complications after unilateral THA is associated with an increased risk of the same complication occurring after staged arthroplasty of the contralateral hip. Patients who experience these complications after unilateral hip arthroplasty should be appropriately counselled regarding their risk profile prior to undergoing staged contralateral hip arthroplasty. Cite this article: Bone Joint J 2019;101-B(6 Supple B):77-83.

Structured three-dimensional co-culture of mesenchymal stem cells with chondrocytes promotes chondrogenic differentiation without hypertrophy.

OBJECTIVE: This study investigated a novel approach to induce chondrogenic differentiation of human mesenchymal stem cells (hMSC). We hypothesized that a structured three-dimensional co-culture using hMSC and chondrocytes would provide chondroinductive cues to hMSC without inducing hypertrophy. METHOD: In an effort to promote optimal chondrogenic differentiation of hMSC, we created bilaminar cell pellets (BCPs), which consist of a spherical population of hMSC encased within a layer of juvenile chondrocytes (JC). In addition to histologic analyses, we examined proteoglycan content and expression of chondrogenic and hypertrophic genes in BCPs, JC pellets, and hMSC pellets grown in the presence or absence of transforming growth factor-ß (TGFß) following 21 days of culture in either growth or chondrogenic media. RESULTS: In either growth or chondrogenic media, we observed that BCPs and JC pellets produced more proteoglycan than hMSC pellets treated with TGFß. BCPs and JC pellets also exhibited higher expression of the chondrogenic genes Sox9, aggrecan, and collagen 2A1, and lower expression of the hypertrophic genes matrix metalloproteinase-13, Runx2, collagen 1A1, and collagen 10A1 than hMSC pellets. Histologic analyses suggest that JC promote chondrogenic differentiation of cells in BCPs without hypertrophy. Furthermore, when cultured in hypoxic and inflammatory conditions intended to mimic the injured joint microenvironment, BCPs produced significantly more proteoglycan than either JC pellets or hMSC pellets. CONCLUSION: The BCP co-culture promotes a chondrogenic phenotype without hypertrophy and, relative to pellet cultures of hMSCs or JCs alone, is more resistant to the adverse conditions anticipated at the site of articular cartilage repair.

Recommendations of the OARSI FDA Osteoarthritis Devices Working Group.

Osteoarthritis (OA) is the most common type of arthritis and a major cause of chronic musculoskeletal pain and functional disability. While both pharmacologic and non-pharmacologic modalities are recommended in the management of OA, when patients with hip or knee OA do not obtain adequate pain relief and/or functional improvement, joint replacement surgery or other surgical interventions should be considered. Total joint arthroplasties are reliable and cost-effective treatments for patients with significant OA of the hip and knee. Evidence from cohort and observational studies has confirmed substantial improvements in pain relief with cumulative revision rates at 10 years following total hip (THA) and total knee arthroplasties (TKA) at 7% and 10%, respectively. Joint replacements have been used in most every synovial joint, although results for joints other than hip and knee replacement have not been as successful. The evolution of new device designs and surgical techniques highlights the need to better understand the risk to benefit ratio for different joint replacements and to identify the appropriate methodology for evaluating the efficacy and optimal outcomes of these new devices, designed to treat OA joints.

Association of bone scintigraphic abnormalities with knee malalignment and pain.

OBJECTIVE: The information content of knee bone scintigraphy was evaluated, including pattern, localisation and intensity of retention relative to radiographic features of knee osteoarthritis, knee alignment and knee symptoms. METHODS: A total of 308 knees (159 subjects) with symptomatic and radiographic knee osteoarthritis of at least one knee was assessed by late-phase (99m)Technetium methylene disphosphonate bone scintigraph, fixed-flexion knee radiograph, full limb radiograph for knee alignment and for self-reported knee symptom severity. Generalised linear models were used to control for within-subject correlation of knee data. RESULTS: The compartmental localisation (medial vs lateral) and intensity of knee bone scan retention were associated with the pattern (varus vs valgus) (p<0.001) and severity (p<0.001) of knee malalignment and localisation and severity of radiographic osteoarthritis (p<0.001). Bone scan agent retention in the tibiofemoral, but not patellofemoral, compartment was associated with severity of knee symptoms (p<0.001) and persisted after adjusting for radiographic osteoarthritis (p<0.001). CONCLUSION: To the authors' knowledge, this is the first study describing a relationship between knee malalignment, joint symptom severity and compartment-specific abnormalities by bone scintigraphy. This work demonstrates that bone scintigraphy is a sensitive and quantitative indicator of symptomatic knee osteoarthritis. Used selectively, bone scintigraphy is a dynamic imaging modality that holds great promise as a clinical trial screening tool and outcome measure.

Management of bone loss in revision total knee arthroplasty.

Bone deficiencies around the knee can present a substantial challenge during revision total knee arthroplasty. Bone loss occurs from stress shielding, osteolysis, chronic infection, and bone removed during implant extraction. Smaller defects have traditionally been treated with cement filling or allograft bone chips. Larger defects can be reconstructed with bulk allografts or custom prostheses. A hinged prosthesis may be necessary to account for ligamentous insufficiency. In addition to traditional methods of managing bone loss, recent developments include the use of metaphyseal-filling implants made of highly porous metal. These implants can be press-fit into host bone to accommodate large metaphyseal defects. Each revision knee surgery provides unique challenges, requiring proficiency in multiple techniques of bone loss management.

Clinical experience with metal-on-metal total joint replacements: indications and results.

Survivorship of total joint arthroplasty depends on the durability of fixation and durability of articulation. The metal-on-polyethylene articular couple has been the most widely used. Polyethylene wear (and the associated cytochemical events that culminate in osteolysis) has been identified as a major factor adversely influencing the durability of joint replacement. This stimulated the orthopaedic community to explore the possibility of using alternative bearings with lower wear rates. Hard-on-hard bearings have been shown to be associated with reduced wear. Metal-on-metal bearings have wear rates that are 20-100 times lower than metal on conventional polyethylene. However, patients with metal-on-metal articulations have increased levels of cobalt and chromium in the serum and urine, and this has raised concerns about toxicity, mutagenesis, and hypersensitivity. At this stage there is no epidemiological evidence to suggest that the risk of carcinogenesis is anything more than theoretical. Successful long-term results have been reported with the cast cobalt-chromium metal-on-metal couples of the mid-1960s. Tissues retrieved at revision of these implants did not show the giant-cell inflammatory response associated with polyethylene particles. Several researchers have reported excellent mid-term results with the current generation of high-precision metal-on-metal bearings.

Development rationale for an articular surface replacement: a science-based evolution.

Hip resurfacing has an enduring appeal because of the advantages of bone conservation and maximal joint stability. However, a far from satisfactory experience with earlier resurfacing designs led to its virtual disappearance in the 1980s. The concept was reintroduced in the late 1990s. The current generation of resurfacing devices generally consisted of a large-diameter metal-on-metal articulation, the femoral components being cemented and the acetabular components utilizing various forms of cementless fixation. The encouraging medium-term results, with a follow-up of up to 8 years using the current generation of surface replacement joints, combined with favourable reports related to long-term performance of some metal bearings have led to a rapid increase in the use of such components with these devices. This trend is most marked in younger, more active patients who have expectations of restoration of lifestyle in addition to improved mobility and pain relief and in whom failure with conventional total hip replacement is much higher than previously reported with more sedentary patients. The aim of this paper is, firstly, to highlight a number of areas of improvement and, secondly, to explain how these may be addressed by making modifications to the design of both implants and instrumentation and to the surgical technique. The areas identified for improvement were tissue preservation (thinner components, and reduced steps between sizes), acetabular cup issues (fixation, insertion, and positioning), femoral component issues (design, loading, and cementation), improved bearing surface characteristics, and simplified precise instrumentation with a low-trauma surgical technique.

Sensitivity of MR arthrography in the evaluation of acetabular labral tears.

OBJECTIVE: MRI has historically provided suboptimal visualization of tears of the acetabular labrum. Degenerative fraying and underlying cartilage abnormalities can often mimic tears of the labrum on conventional MRI. Administration of intraarticular gadolinium enhances the MRI appearance of the labrum to improve detection of labral abnormalities. This study examined the improved diagnostic sensitivity of MR arthrography compared with conventional MRI and the importance of confining the study to a small field of view. MATERIALS AND METHODS: Fifty-one hips were imaged in 48 patients. Fourteen hips underwent conventional MRI with a large field of view (30-38 cm). Seven hips underwent conventional MRI with a small field of view (14-20 cm). Thirty hips underwent MR arthrography with a small field of view (14-20 cm). Labral tears were diagnosed when contrast material was identified within the labrum or between the labrum and the acetabulum, when a displaced fragment was noted, or when a paralabral cyst was identified. All study results were compared with findings at the time of hip arthroscopy. RESULTS: Conventional MRI with a large field of view was 8% sensitive in detecting labral tears compared with findings at the time of arthroscopy. Diagnostic sensitivity was improved to 25% with a small field of view. MR arthrography with a small field of view was 92% sensitive in detecting labral tears. CONCLUSION: A combination of MR arthrography and a small field of view is more sensitive in detecting labral abnormalities than is conventional MRI with either a large or a small field of view.

Impact of disease severity and gastrointestinal side effects on the health state preferences of patients with osteoarthritis.

OBJECTIVE: To describe the health state preferences of patients with osteoarthritis (OA) according to the level of pain and disability and the extent of gastrointestinal side effects from nonsteroidal antiinflammatory drugs (NSAIDs). METHODS: Using combinations of 5 OA health states (4 specifying medication use) and 6 gastrointestinal side effect profiles, we developed 25 scenarios. In an Internet survey, adults with OA evaluated 5 randomly chosen health state-side effect scenarios (in addition to scenarios for congestive heart failure and wearing dentures, as benchmarks). They rated the scenarios on a 0-100 scale, in which 100 corresponds to best imaginable health. Unadjusted mean ratings were calculated using a difference-in-difference approach. A generalized linear model was used to estimate the effects of disease severity and side effect severity on the ratings, after controlling for patient characteristics. RESULTS: A total of 4,386 respondents whose mean age was 55.3 years, of whom 3,107 (70.8%) were women and 4,007 (91.4%) were white, completed the survey. Mean adjusted ratings for health state-side effect scenarios ranged from 94.9 for the mildest scenario to 25.3 for the most severe scenario. Severity of NSAID side effects had a greater negative influence on the ratings in milder OA states than in more severe OA states. Ratings were lower among men (P < 0.001) and among respondents with OA pain in the previous 24 hours (P < 0.001). Disease severity had a greater effect on ratings than did side effect severity. CONCLUSION: Patients consider pain and functional limitations associated with OA to be important determinants of well-being. Future research should attempt to determine whether patients prefer reductions in their OA-related pain and disability over improvements in treatment side effect profiles.

A comparative assessment of alignment angle of the knee by radiographic and physical examination methods.

OBJECTIVE: To compare the knee-alignment angle from a full-limb radiograph (mechanical axis) with the anatomic-axis angle as measured by physical examination using a goniometer and by 2 other radiographic methods. METHODS: The knee-alignment angle was measured in 114 knees of 57 subjects who had radiographic osteoarthritis (OA), with a Kellgren/Lawrence grade of >/=1 in at least one knee. The mechanical axis was defined as the angle formed by the intersection of 2 lines, one from the center of the head of the femur to the center of the tibial spines, and a second from the center of the talus to the center of the tibial spines. The anatomic axis was defined as the angle formed by 2 lines, each originating from a point bisecting the femur and tibia and converging at the center of the tibial spine tips. The anatomic-axis angle was measured by 3 methods: 1) physical examination using a goniometer, 2) a posteroanterior (PA) fixed-flexion knee radiograph (anatomic(PA) axis), and 3) an anteroposterior (AP) full-limb radiograph (anatomic(AP) axis). RESULTS: Significant correlations were found between the mechanical-axis angle and the anatomic-axis angle measured by each of the 3 methods: by goniometer (r = 0.70, P < 0.0001), by anatomic(PA) axis (r = 0.75, P < 0.0001), and by anatomic(AP) axis (r = 0.65, P < 0.0001). The anatomic axis was offset a mean 4.21 degrees valgus from the mechanical axis (3.5 degrees in women, 6.4 degrees in men), which was consistent across all methods. CONCLUSION: Knee alignment assessed clinically by goniometer or measured on a knee radiograph is correlated with the angle measured on the more cumbersome and costly full-limb radiograph. These alternative measures have the potential to provide useful information regarding the risk of progression of knee OA when a full-limb radiograph is not available.

Comparison of a hydroxyapatite-coated sleeve and a porous-coated sleeve with a modular revision hip stem. A prospective, randomized study.

BACKGROUND: Bone ingrowth into a cementless prosthesis can be achieved by both porous and hydroxyapatite coatings. The purpose of this study was to compare the performance of a hydroxyapatite-coated proximal sleeve and a porous bead-coated sleeve in patients managed with a modular revision hip system. METHODS: Between August 1992 and December 1996, fifty-three consecutive femoral revisions performed with an S-ROM stem in fifty-two patients were prospectively randomized at the time of surgery to either a hydroxyapatite-coated or a porous-coated sleeve. All patients were evaluated clinically and radiographically at three months, six months, and yearly for a minimum of two years (average, four years; range, two to 7.5 years). Femoral defects were classified according to the criteria of Paprosky et al. Six patients died and four patients were lost to follow-up, leaving forty-two patients (forty-three hips) as the final study group. RESULTS: For the entire group, two femoral stems, one of which had been implanted in a hip with a Paprosky type-II femoral defect and the other in a hip with a Paprosky type-IIIB femoral defect, required a repeat revision, one for pain and the other for aseptic loosening. Radiographic evidence of bone ingrowth was observed in 96% (twenty-six) of the twenty-seven femora with type-I or II defects and in 81% (thirteen) of the sixteen femora with type-III defects. Femoral component survival, with use of revision as the end point, was 95% at four years for the entire group. The Harris hip scores were not significantly different when stratified by implant type, but were significantly different when stratified by bone loss (p < 0.05). In the femora with type-I or II defects, no difference was detected between those treated with a hydroxyapatite-coated implant and those that received a porous-coated implant with respect to bone ingrowth. However, in femora with type-III defects, the likelihood of the development of bone ingrowth was 2.6 (95% confidence interval, 1.3 to 5.17) times greater in hips that received a hydroxyapatite-coated implant (all eight developed ingrowth) than in hips that had a porous-coated implant (five of eight developed ingrowth) (p = 0.05). CONCLUSIONS: Bone fixation was achieved more often with hydroxyapatite-coated sleeves in femora with Paprosky type-III defects, but no significant difference was noted in outcomes between the two implant types when used in bone with type-I or type-II femoral defects. Overall, the S-ROM modular hip stem performed better in femora with type-I or II bone defects than in femora with type-III defects. LEVEL OF EVIDENCE: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Photocrosslinkable hyaluronan as a scaffold for articular cartilage repair.

Hyaluronan-based scaffolds are of interest for tissue-engineered cartilage repair due to an important role for hyaluronan in cartilage development and function. In this study, an in situ photocrosslinkable hyaluronan (HA-MA) was developed and evaluated as a scaffold for articular cartilage repair. Chondrocytes were encapsulated in crosslinked HA-MA and evaluated for their ability to synthesize cartilaginous matrix in vitro. The mechanical and physical properties of the crosslinked HA-MA hydrogels were similar to that of other hydrogels, with compressive and dynamic shear moduli of 0.6 and 0.3 kPa, respectively, and diffusion coefficients of 600-8000 microm2/s depending on molecular weight. Chondrocytes remained rounded in the HA-MA hydrogels in vitro, and accumulated significant amounts of cartilaginous matrix. Osteochondral defects filled with HA-MA were infiltrated with cells, appeared to integrate well with native tissue, and also accumulated substantial cartilaginous matrix by 2 weeks after surgery. In summary, photocrosslinkable HA-MA promoted the retention of the chondrocytic phenotype and cartilage matrix synthesis for encapsulated chondrocytes in vitro and accelerated healing in an in vivo osteochondral defect model.

The role of the cytoskeleton in the viscoelastic properties of human articular chondrocytes.

Biomechanical factors are believed to play an important role in regulating the metabolic activity of chondrocytes in articular cartilage. Previous studies suggest that cytoskeletal proteins such as actin, vimentin, and tubulin influence cellular mechanical properties, and may therefore influence the mechanical interactions between the chondrocyte and the surrounding tissue matrix. In this study, we investigated the role of specific cytoskeletal components on the mechanical properties of individual chondrocytes isolated from normal or osteoarthritic hip articular cartilage. Chondrocytes were exposed to a range of concentrations of chemical agents that disrupt the primary cytoskeletal elements (cytochalasin D for F-actin microfilaments, acrylamide for vimentin intermediate filaments, and colchicine for microtubules). Chondrocyte mechanical properties were determined using the micropipette aspiration technique coupled with a viscoelastic solid model of the cell. Chondrocyte stiffness (elastic modulus) was significantly increased with osteoarthritis. With increasing cytochalasin D treatment, chondrocyte stiffness decreased by up to 90% and apparent viscosity decreased by up to 80%. The effect of cytochalasin D was greater on normal chondrocytes than those isolated from osteoarthritic cartilage. Treatment with acrylamide also decreased the moduli and viscosity, but only at the highest concentration tested. No consistent changes in cell mechanical properties were observed with colchicine treatment. These findings suggest that microfilaments and possibly intermediate filaments provide the viscoelastic properties of the chondrocyte, and changes in the structure and properties of these cytoskeletal elements may reflect changes in the chondrocyte with osteoarthritis.

Multipotent stromal cells derived from the infrapatellar fat pad of the knee.

Tissue engineering approaches for promoting the repair of skeletal tissues have focused on cell-based therapies involving multipotent stromal cells. Recent studies have identified such cells in several tissues in the adult human, including skin, muscle, bone marrow, and subcutaneous fat. This study examined the hypothesis that the infrapatellar fat pad of the adult knee contains progenitor cells that have the ability to differentiate into chondrocytes, osteoblasts, or adipocytes under appropriate culture conditions. Cells isolated from the fat pad stroma had a profile of cell-surface molecules similar but not identical to that of bone marrow-derived mesenchymal stem cells. Using defined culture conditions, fat pad-derived stromal cells were induced to differentiate cells with phenotypic characteristics of: (1) chondrocytes, synthesizing cartilage matrix molecules; (2) adipocytes, producing lipid vacuoles and leptin; or (3) osteoblasts, forming mineralized tissue. The culture conditions also modulated the expression of characteristic gene markers for each lineage. This study supports the hypothesis that multipotent stromal cells are present in many connective tissues in the adult human. Given its location and accessibility, the fat pad may prove to be a potential source of progenitor cells for musculoskeletal tissue engineering.

Joint degeneration following meniscal allograft transplantation in a canine model: mechanical properties and semiquantitative histology of articular cartilage.

This study examined the hypothesis that meniscal allograft transplantation serves a "chondroprotective" role and prevents the histological and biomechanical changes of the articular cartilage following meniscectomy. Skeletally mature mongrel dogs underwent total medial meniscectomy and received either a fresh meniscal allograft ( n=10) or no further treatment ( n=10). Semiquantitative histology and biomechanical analysis of the femoral articular cartilage was used to assess cartilage pathology 12 weeks following surgery. Histological analysis showed significant changes in cartilage structure that did not differ between the meniscectomy and allograft transplantation groups. Similarly, the tensile modulus of the surface zone cartilage was significantly lower than that in unoperated controls following either meniscectomy or allograft transplantation. A significant correlation was observed between the biomechanical and histological changes, suggesting that degenerative changes in cartilage structure and mechanical function are interrelated. Our findings do not support the hypothesis that meniscal allograft transplantation provides chondroprotection of the femoral condyle and also suggest that it does not lead to increased degenerative changes.

Urea as a passive transport marker for arthritis biomarker studies.

OBJECTIVE: To develop a method to correct for the unknown dilution of synovial fluid that occurs during lavage of a joint, we evaluated the utility of urea, a molecule that is neither synthesized nor metabolized by joint tissues, as a means of correcting for the dilutional effects of lavage procedures and effusions. METHODS: Joint fluids were obtained from normal canine joints by direct aspiration (n = 41) and lavage (n = 10). Acute joint injury was induced in 4 joints by intraarticular injection of chymopapain. Serum and joint fluid levels of urea and joint fluid concentrations of glucose, lactate, cartilage oligomeric matrix protein (COMP), and keratan sulfate (KS) were measured in these 55 joints. RESULTS: Urea concentrations in joint fluid were directly proportional to those in serum throughout a wide range of concentrations in normal joints. From this relationship, the dilution factor introduced by joint lavage was determined. This method was applied to quantify biomarker concentrations in synovial lavage fluid and was found to successfully correct for lavage-induced dilution of glucose, lactate, COMP, and KS to levels equivalent to those in samples aspirated directly. In the context of chymopapain-induced joint effusion, urea concentrations continued to be proportional to serum concentrations, but were much lower, enabling an estimation of the change in the volume of distribution (V(d)) of a marker due to a change in joint water content in the setting of inflammation characterized by effusion. Lactate and KS levels rose markedly in response to chymopapain. After adjustment for the V(d), the glucose concentration in the chymopapain-injected joints did not change. CONCLUSION: Urea provides a robust method of quantifying and correcting for the dilution of synovial fluid due to joint lavage or inflammation. This method is potentially applicable to surrogate marker studies in human arthritis.

The mechanical properties of the human hip capsule ligaments.

The human hip capsule is adapted to facilitate upright posture, joint stability, and ambulation, yet it routinely is excised in hip surgery without a full understanding of its mechanical contributions. The objective of this study was to provide information about the mechanical properties of the ligaments that form the hip capsule. Cadaver bone-ligament-bone specimens of the iliofemoral, ischiofemoral, and femoral arcuate ligaments were tested to failure in tension. The hip capsule was found to be an inhomogeneous structure and should be recognized as being composed of discrete constituent ligaments. The anterior ligaments, consisting of the 2 arms of the iliofemoral ligament, were much stronger than the posterior ischiofemoral ligament, withstanding greater force at failure and exhibiting greater stiffness. Knowledge of the anatomy and mechanical properties of the capsule may help the hip surgeon choose an appropriate surgical approach or repair strategy.

Hip arthroscopy in the adolescent and pediatric athlete.

The current literature offers only sparse reports of the use of hip arthroscopy in the pediatric patient injured during athletics. In contrast, the role of this technique in the diagnosis and treatment of multiple childhood hip conditions including pyarthrosis, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, coxa vara, juvenile chronic arthritis, chondrolysis, and avascular necrosis is well described. The application of this relatively uncommon technique to the young athlete has only recently become more attractive. The ability to examine and treat traumatic intra-articular pathology with minimal morbidity and prompt recovery is mandated by the young age of these patients and their demanding activity levels. Hip arthroscopists are now beginning to correlate preoperative physical exam findings and history with diagnosis and expectations for outcome. As our combined experience with this technique grows, the specific indications for its use in the young athlete become increasingly better defined. In pediatric and adolescent patients, the new onset of hip pain should warrant a high level of suspicion for the more common causes of pain such as infection, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, or developmental dysplasia. When these have been evaluated, further differential diagnosis should include labral tears, loose bodies, synovitis, and chondral lesions. As this review begins to elucidate, these conditions are amenable to arthroscopic evaluation and treatment. At this time, the presence of reproducible mechanical symptoms after a twisting or axial loading injury during athletics should prompt the orthopaedic surgeon to consider arthroscopic examination of the hip if conservative therapy fails. Satisfying and reproducible results have been achieved when using hip arthroscopy within these parameters.

Interleukin-1, tumor necrosis factor alpha, and interleukin-17 synergistically up-regulate nitric oxide and prostaglandin E2 production in explants of human osteoarthritic knee menisci.

OBJECTIVE: In osteoarthritis (OA), a combination of biochemical and biomechanical factors may damage both menisci and articular cartilage. Nitric oxide (NO) and prostaglandin E2 (PGE2) have been implicated as mediators of inflammation in OA. The goals of this study were to determine if menisci from patients with OA produce NO and PGE2, and if the proinflammatory cytokines interleukin-1beta (IL-1beta), tumor necrosis factor a (TNFalpha), and IL-17 augment NO and PGE2 production by these tissues. METHODS: Menisci were obtained from 17 patients (age 47-75 years) undergoing total knee replacement for OA. Tissue explants were cultured alone or with IL-1beta, IL-17, or TNFalpha, and the release of NO and PGE2 from the tissue as well as the presence of type 2 nitric oxide synthase (NOS2) and cyclooxygenase 2 (COX-2) antigens were measured. RESULTS: All menisci constitutively produced NO, and significant increases in NO production were observed in the presence of IL-1beta, TNFalpha, or IL-17 (P < 0.05). The combination of IL-17 and TNFalpha significantly increased NO production compared with either cytokine alone. Basal and cytokine-stimulated NO synthesis was inhibited by the NOS inhibitors NG-monomethyl-L-arginine or N-3-aminoethylbenzylacetamidine (1400W). IL-1beta significantly increased PGE2 production. The combination of IL-1beta and TNFalpha had an additive effect on PGE2 production, while addition of IL-17 to TNFalpha or IL-1beta synergistically enhanced PGE2 production. Inhibition of NO production by 1400W significantly increased IL-1beta-stimulated PGE2 production, and inhibition of PGE2 production by the COX-2 inhibitor N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide significantly increased IL-17-stimulated NO production. CONCLUSION: Menisci from humans with OA spontaneously produced NO and PGE2 in a manner that was synergistically or additively augmented by cytokines. NO and PGE2 exhibited reciprocal regulatory effects on one another, suggesting that pharmaceutical agents designed to inhibit NOS2 or COX-2 production may in fact be influencing both pathways.

Regional material properties of the human hip joint capsule ligaments.

The hip joint capsule functions to constrain translation between the femur and acetabulum while allowing rotational and planar movements. Despite the crucial role it plays in the pathogenesis of hip instability, little is known about its biomechanical properties. The goal of this study was to determine the regional material properties of the iliofemoral and ischiofemoral ligaments of the capsule. Ten human cadaveric specimens of each ligament were tested to failure in tension. The stress at failure, strain at failure, strain energy density at failure, toe- and linear-region elastic moduli, and the Poisson's ratio were measured for each ligament. The strain to failure was greatest in the ischiofemoral ligament, while no significant difference was noted in failure stress by region or ligament. The Young's moduli of elasticity ranged from 76.1 to 285.8 MPa among the different ligaments, and were generally consistent with properties previously reported for the shoulder capsule. The elastic moduli and strain energy density at failure differed by region. No significant differences in Poisson's ratio were found by region or ligament. The average Poisson's ratio was approximately 1.4, consistent with anisotropic behavior of ligamentous tissues. Understanding the material properties of the hip capsule may help the orthopaedic surgeon better understand normal ligament function, and thereby choose a surgical approach or strategy of repair. Furthermore, knowledge of the normal mechanical function of the hip capsule ligaments could assist in the evaluation of the success of a repair.