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.

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.

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.

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.

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.

Tensile properties of articular cartilage are altered by meniscectomy in a canine model of osteoarthritis.

Loss of or damage to the meniscus alters the pattern of loading in the knee joint and frequently leads to cartilage degeneration and osteoarthritis. The mechanical properties of articular cartilage have been shown to reflect the extent of cartilage degeneration in human osteoarthritis and in experimental models of joint disease, but there is little experimental data documenting changes in cartilage mechanics following meniscectomy. We hypothesized that the tensile properties of the surface zone of articular cartilage are altered following total medial meniscectomy. Twelve mongrel dogs underwent complete resection of the medial meniscus in the right knee, and the femoral cartilage was studied 12 weeks after the operation. We performed uniaxial, tensile stress-relaxation tests to determine the equilibrium tensile modulus of surface-zone cartilage. Water and glycosaminoglycan content were also measured at site-matched locations. The tensile moduli of the cartilage decreased significantly following meniscectomy. The linear region modulus decreased by 40%, from 25.5 +/- 7.7 to 15.3 +/- 7.2 MPa. There was a weak (r = -0.45), but significant, correlation between the linear region modulus and the gross morphological grade for cartilage damage. Water and glycosaminoglycan content did not change following meniscectomy. Composition was not correlated with mechanical properties or morphological grade, suggesting that cartilage structure may play a more important role than composition in determining the mechanical properties. The observed decrease in cartilage material properties provides a quantitative measure of the loss of cartilage function following meniscectomy and reflects a pattern of change that is consistent with damage to the collagen-proteoglycan solid network.

Gentamicin distribution from a collagen carrier.

Local delivery of antibiotics by a degradable carrier has the potential for high local antibiotic levels and avoids systemic toxicity. Intravenous access, renal function monitoring, and subsequent surgical removal may not be required when degradable local delivery modalities are used. This study examined the in vivo elution of gentamicin from processed bovine collagen (type I) in 66 adult White rabbits. Collagen impregnated with gentamicin (3 mg/kg) was implanted into the vastus lateralis, and data were collected from 15 minutes to 28 days after implantation. Local tissue biopsies were taken a minimum of 2 mm from the implantation site. The gentamicin was released into the local tissue and averaged more than 3,800 micrograms/ml during the initial 4 hours after implantation. Local levels fell to 6.90 +/- 5.22 micrograms/ml at 24 hours and subsequently were 2.70 +/- 1.75 micrograms/ml or more through day 28. Serum levels reached an average peak of 4.04 +/- 1.75 micrograms/ml at 5 hours after implantation, decreased after the initial 24 hours, and subsequently were less than 0.41 +/- 0.20 microgram/ml through day 28. Collagen impregnated with gentamicin proved to be an effective degradable carrier of gentamicin in the healthy rabbit; it provided local tissue concentrations above the minimum inhibitory concentration and serum concentrations below levels associated with systemic toxicity for 28 days after implantation.

Longitudinal characterization of synovial fluid biomarkers in the canine meniscectomy model of osteoarthritis.

Damage to the meniscus can lead to posttraumatic osteoarthritis. Early markers of joint injury and tissue disease may be useful in developing and administering clinical treatment. We investigated the effects of total medial meniscectomy on biomarkers measured serially in synovial lavage fluid each month for 3 months. Following meniscectomy in dogs, four biomarkers were evaluated: cartilage oligomeric matrix protein, keratan sulfate epitope (5D4), the 3B3(-) neoepitope of chondroitin-6-sulfate, and the 3B3(+) chondroitinase-generated epitope of chondroitin-6-sulfate. Meniscectomy led to statistically significant elevations of all four biomarkers, with levels peaking at 4 weeks. By 12 weeks, the level of the 5D4 epitope returned to the preoperative baseline level whereas that of cartilage oligomeric matrix protein, 3B3(-), and 3B3(+) remained above the baseline. Concentrations of these biomarkers in the knees not operated on did not change significantly from the baseline. The levels of cartilage oligomeric matrix protein and 3B3(-) relative to 3B3(+) remained constant in all knees. In contrast, the level of 5D4 relative to 3B3(+) declined over time in the knee operated on but remained constant in the knee not operated on. These results demonstrate a quantitative change in the molecular components of synovial fluid after meniscectomy, as well as a qualitative change evinced by an alteration in the relative proportions of these epitopes. Extensive analyses showed a strong correlation between serum levels of 3B3(-) from the femoral and cephalic veins; however, serum 3B3(-) was not correlated with synovial fluid 3B3(-). These findings support the hypothesis that the concentrations of select cartilage biomarkers in synovial fluid are altered following meniscectomy and are promising tools for objectively monitoring the induction of osteoarthritis in this model system.

Simultaneous changes in the mechanical properties, quantitative collagen organization, and proteoglycan concentration of articular cartilage following canine meniscectomy.

The mechanical properties and microstructure of articular cartilage from the canine tibial plateau were studied 12 weeks after total medial meniscectomy. The organization of the birefringent collagen network was measured with quantitative polarized light microscopy to determine the thickness and the degree of organization of the superficial and deep zones. The zonal concentration of sulfated glycosaminoglycan was quantified with digital densitometry of safranin-O staining. Equilibrium compressive and shear properties, as well as dynamic shear properties, were measured at sites adjacent to those of microstructural analysis. The results evinced significant loss of cartilage function following meniscectomy, with decreases of 20-50% in the compressive and shear moduli. There was no evidence of alterations in the degree of collagen fibrillar organization, although a complete loss of the surface zone was seen in 60% of the samples that underwent meniscectomy. Meniscectomy resulted in a decreased concentration of sulfated glycosaminoglycan, and significant positive correlations were found between the equilibrium compressive modulus and the glycosaminoglycan content. Furthermore, the shear properties of cartilage correlated directly with collagen fibrillar organization measured at the superficial zone of corresponding sites. These findings demonstrate that meniscectomy leads to impaired mechanical function of articular cartilage, with significant evidence of quantitative correlations between cartilage microstructure and mechanics.

Donor-site morbidity with use of vascularized autogenous fibular grafts.

One hundred and ninety-eight consecutive patients (247 vascularized fibular grafts) were studied to determine the prevalence of morbidity at the donor site after the grafts had been obtained. Objective motor weakness, subjective discomfort in the ankle and other sites in the leg, and sensory abnormalities in the lower limb (or limbs) from which the graft had been obtained were recorded. The average duration of follow-up was forty-seven months (range, twenty-four to 144 months). Kaplan-Meier analysis was used to estimate the prevalence of each finding for the entire cohort over time. Forty-seven (19.0 per cent) of the 247 lower limbs had at least one of the findings, and eighteen(24.3 percent) of the seventy-four limbs for which data were available at five years or more had findings at that time. Twenty-five (10.1 per cent) of the 247 limbs had evidence of motor weakness at three months postoperatively, although no limb had this finding subsequently. At five years or more postoperatively, the prevalence had decreased to two (2.7 per cent) of the seventy-four limbs. Twelve (4.9 per cent) of the 247 limbs had sensory deficits at three months; this increased to 11.8 per cent (95 per cent confidence interval, 7.7 to 17.7 per cent), according to the Kaplan-Meier analysis, at five years. Pain at sites other than the ankle was noted in nine (3.6 per cent) of the 247 limbs at three months and in 8.9 per cent (95 per cent confidence interval, 5.5 to 14.1 per cent), according to the Kaplan-Meier analysis, at five years. The prevalence of pain in the ankle also increased with time, from four (1.6 per cent) of the 247 limbs at three months to 11.5 per cent (95 per cent confidence interval, 7.4 to 17.6 per cent), according to the Kaplan-Meier analysis, at five years. Removal of a vascularized portion of the fibula is associated with a low prevalence of motor weakness and sensory deficits in the foot. The prevalence of pain in the ankle and lower limb increases with time, with some patients having a late onset of the symptoms. While free vascularized fibular grafts remain ideal for many applications, the morbidity must be weighed against the benefits.

The effect of hip stem material modulus on surface strain in human femora.

Human femora were used to compare the changes in bone surface strain resulting from decreasing the material modulus of a collarless hip stem to determine whether a highly elastic stem increased bone loading. Three substrate materials were tested: titanium (modulus of elasticity 110 GPa), carbon fiber composite (modulus of elasticity 52 GPa), and polymethylmethacrylate (PMMA, modulus of elasticity of 1.9 GPa). Two separate analyses were performed in which femora were implanted randomly with one of the three stem types. Results showed that assembly strains did not differ significantly among different materials. There was a large strain reduction in the proximal region of the femora for all stem substrates relative to the intact femur. Although there was statistically greater surface shear strain as the material modulus decreased, the PMMA stem did not substantially increase bone loading.

Long-term functional results in patients with anterolateral rotatory instability treated by iliotibial band transfer.

The purpose of this paper is to define the use of the extraarticular, lateral reconstruction in the spectrum of patients with cruciate deficiency. A review was conducted of 112 consecutive patients with a MacIntosh-type iliotibial band transfer done between 1972 and 1986. Fifty-six of the patients had a partial or complete meniscectomy, and 24% had failed a previous extraarticular procedure. Eighty-one percent were men, with a mean age of 23. Twenty-five percent of the patients had radiographic degenerative changes at the knee at the outset. Ninety-eight percent had an anterior drawer of 1+ or greater; 97% had a pivot shift greater than trace. All patients had symptomatic knee instability. Seventy-seven of the 112 patients (69%) were available for followup (range, 24 months to 15.5 years; median, 7.6). Twenty-three patients (21%) returned for examination, KT-1000 and Cybex testing, and radiographs. An additional 54 patients (48%) were seen by their local physicians or returned a detailed questionnaire that included the Cincinnati knee rating scale. At final followup, 38% complained of some knee instability, 36% had recurrent effusions, 61% had intermittent pain, 79% had radiographic gonarthrosis, and 25% had undergone additional surgery. Forty-two percent had a positive Lachman after surgery, and only 15% had a pivot shift. The mean knee score was 81.1. Previous extraarticular anterior cruciate ligament reconstruction, meniscectomy, and generalized ligamentous laxity were associated with a significant decrement in the knee rating (P = 0.05). Ligamentous laxity strongly correlated with symptoms of giving way.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between diagnosis and outcome in arthroscopy of the hip.

PURPOSE: The purpose of this study was to compare the results of arthroscopy of the hip for osteonecrosis (ON) with those obtained for other diagnoses by presenting a cohort of patients with diagnosis and symptoms as dependant variables in a consecutive series of 86 cases of hip arthroscopy. TYPE OF STUDY: Retrospective review of outcomes. METHODS: There were 83 patients (86 hips) who underwent arthroscopy. Indications included ON (43%), labral injuries (20%), osteoarthritis (degenerative joint disease, DJD) (10%), Legg-Calvé-Perthes (LCP) disease (10%), and loose bodies (10%). All but 2 patients had had symptoms for at least 6 months. Symptoms were pain (100%), mechanical problems (78%), and loss of motion (56%). Arthroscopy was performed in the supine position, using a standard traction table, 30 degrees and/or 70 degrees arthroscopes, and the anterior and peritrochanteric portals. Data were collected longitudinally, retrospectively reviewed, and statistically analyzed. RESULTS: No complications were seen; 60% of the patients had significant improvement over an average follow-up of 30 months. Better results were with labral tears (91%, P <.003) or LCP disease (89%, P <.05). ON and DJD did worse with only 40% and 44% improvement, respectively. After free-vascularized fibular graft (FVFG), 34% of patients showed improvement at follow-up (P =.003). Eighteen patients (21%) underwent total hip arthroplasty at an average of 8.4 months after arthroscopy. Mechanical symptoms were a significant favorable prognostic factor (P =.0019), with 85% having a good result. Patients with ON and mechanical symptoms had a significantly lower conversion rate to total hip arthroplasty than those with only pain or pain and decreased range of motion (P =.0043). CONCLUSIONS: Arthroscopy of the hip is useful for diagnosis and therapy of loose bodies, labral injuries, focal chondral lesions, or the late sequellae of LCP disease. We conclude that the presence of mechanical symptoms is a favorable prognostic factor for any diagnosis except degenerative arthritis. Furthermore, the identification of mechanical symptoms is a specific indication for arthroscopy in ON before or after FVFG.

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.

Hematogenous patellar osteomyelitis associated with human immunodeficiency virus.

The case of a 37-year-old man with hematogenous osteomyelitis associated with the human immunodeficiency virus (HIV) is presented, with a review of the literature. Hematogenous osteomyelitis is a relatively rare entity in the patella; most cases have involved adolescents and immunocompromised patients. There have been no previous reports of hematogenous osteomyelitis in HIV-positive patients. The diagnosis requires clinical suspicion and roentgenographic evidence. Point tenderness over the patella and a painful, swollen knee joint are signs that should alert a physician to the possibility of hematogenous osteomyelitis. Laboratory studies are often of little value, and systemic symptoms are often absent. Treatment requires appropriately directed intravenous antibiotics and open drainage and curettage of the patella. Patellectomy may be required for large lesions and in instances of articular involvement. Computed tomography is a helpful diagnostic tool. The patient in this presentation had osteomyelitis of the patella with a knee pyarthrosis. He had open debridement of the extensor mechanism and knee joint, but ultimately required amputation because of repeat pyarthroses.

Treatment of pathologic fracture of the humerus.

Twenty-one patients with 22 pathologic humeral fractures were seen between January 1977 and November 1988. All fractures were secondary to myeloma or metastatic disease. Primary bone tumors were not included. Nineteen of 22 fractures were treated with intramedullary fixation: 12 of these fractures were also treated with methylmethacrylate. Two patients had compression plating, and the remaining patient had no surgery. Twenty-eight percent had a previously undiagnosed malignancy. Postoperatively, 78% of the patients had only mild or moderate pain. Five patients had progression of local disease postoperatively, two resulting in failure of fixation. Both plates failed. Three patients required additional humeral procedures, one of which was a shoulder disarticulation for pain. Intramedullary fixation of pathologic fractures improves the quality of life by controlling pain for most patients. Complications, treatment failures, and pain are related to a 29% rate of tumor progression and a 23% rate of fixation failure.

Outcomes in surgical treatment of femoral neck fracture: analysis of failures secondary to osteonecrosis.

We analyzed failures of surgical treatment of femoral neck fractures due to osteonecrosis in a consecutive series of 26 patients with an average age of 31 (range, 10 to 49 years). These patients were referred for treatment of osteonecrosis that developed after internal fixation of a fracture of the femoral neck. The average Harris hip score at the time of referral was 59. The length of time from fracture treatment to the development of osteonecrosis averaged 22.5 months (range, 5 months to 13 years). All patients were symptomatic at the time of presentation. Internal fixation used at the time of the initial trauma included a variety of cannulated and noncannulated screws and sliding hip screws. Of the 27 fractures, 7 (26%) were nondisplaced, 20 (74%) were displaced, and 2 (7%) were open and displaced. Fifteen patients had previously had removal of hardware, making magnetic resonance imaging of the femoral head possible. Of those patients, 2 had involvement of 25% or less of the femoral head, 7 had involvement of 25% to 50%, 5 had involvement of 50% to 75%, and 1 patient appeared to have complete involvement of the femoral head. Among the displaced fractures, 30% (6/20) had a radiographically evident malreduction. Radiographs were adequate for evaluation of hardware placement in 78% (21/27) of the fractures. Central placement of the hardware was noted in only 9% (2/21). Superolateral positioning of the hardware within the femoral head was most frequently noted.