Duncan Whitwell

Pseudotumours associated with metal-on-metal hip resurfacings

We report 17 patients (20 hips) in whom metal-on-metal resurfacing had been performed and who presented with various symptoms and a soft-tissue mass which we termed a pseudotumour. Each patient underwent plain radiography and in some, CT, MRI and ultrasonography were also performed. In addition, histological examination of available samples was undertaken. All the patients were women and their presentation was variable. The most common symptom was discomfort in the region of the hip. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. To date, 13 of the 20 hips have required revision to a conventional hip replacement. Two are awaiting revision. We estimate that approximately 1% of patients who have a metal-on-metal resurfacing develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. We are concerned that with time the incidence of these pseudotumours may increase. Further investigation is required to define their cause.

Optimal acetabular orientation for hip resurfacing

Pseudotumours are a rare complication of hip resurfacing. They are thought to be a response to metal debris which may be caused by edge loading due to poor orientation of the acetabular component. Our aim was to determine the optimal acetabular orientation to minimise the risk of pseudotumour formation. We matched 31 hip resurfacings revised for pseudotumour formation with 58 controls who had a satisfactory outcome from this procedure. The radiographic inclination and anteversion angles of the acetabular component were measured on anteroposterior radiographs of the pelvis using Einzel-Bild-Roentgen-Analyse software. The mean inclination angle (47 degrees, 10 degrees to 81 degrees) and anteversion angle (14 degrees, 4 degrees to 34 degrees) of the pseudotumour cases were the same (p = 0.8, p = 0.2) as the controls, 46 degrees (29 degrees to 60 degrees) and 16 degrees (4 degrees to 30 degrees) respectively, but the variation was greater. Assuming an accuracy of implantation of +/- 10 degrees about a target position, the optimal radiographic position was found to be approximately 45 degrees of inclination and 20 degrees of anteversion. The incidence of pseudotumours inside the zone was four times lower (p = 0.007) than outside the zone. In order to minimise the risk of pseudotumour formation we recommend that surgeons implant the acetabular component at an inclination of 45 degrees (+/- 10) and anteversion of 20 degrees (+/- 10) on post-operative radiographs. Because of differences between the radiographic and the operative angles, this may be best achieved by aiming for an inclination of 40 degrees and an anteversion of 25 degrees.

Necrotic granulomatous pseudotumours in bilateral resurfacing hip arthoplasties: evidence for a type IV immune response.

Clinical, radiological and histological findings were analysed in four patients who developed bilateral pseudotumours following metal-on-metal (MoM) resurfacing arthroplasties of both hips. Using a panel of monoclonal antibodies directed against HLA-DR, macrophages (CD14, CD68), dendritic cells (DC-SIGN, S100, CD11c), B cells (CD20), and T cells (CD3, CD4, CD8), the nature of the heavy inflammatory response seen in these cases was examined. Bilateral masses developed in periprosthetic soft tissues following the second MoM arthroplasty; these were characterised histologically by extensive coagulative necrosis, a heavy macrophage infiltrate and the presence of granulomas containing macrophages and giant cells; there was also a diffuse lymphocyte and variable plasma cell and eosinophil polymorph infiltrate. Immunohistochemistry showed strong expression of HLA-DR, CD14 and CD68 in both granulomatous and necrotic areas; lymphocytes were predominantly CD3+/CD4+ T cells. The clinical, morphological and immunophenotypic features of these necrotic granulomatous pseudotumours, which in all cases develop following a second resurfacing hip arthroplasty, is suggestive of a type IV immune response, possibly to MoM metal alloy components.

Role of the transcription factor T (brachyury) in the pathogenesis of sporadic chordoma: a genetic and functional-based study

A variety of analyses, including fluorescence in situ hybridization (FISH), quantitative PCR (qPCR) and array CGH (aCGH), have been performed on a series of chordomas from 181 patients. Twelve of 181 (7%) tumours displayed amplification of the T locus and an additional two cases showed focal amplification; 70/181 (39%) tumours were polysomic for chromosome 6, and 8/181 (4.5%) primary tumours showed a minor allelic gain of T as assessed by FISH. No germline alteration of the T locus was identified in non‐neoplastic tissue from 40 patients. Copy number gain of T was seen in a similar percentage of sacrococcygeal, mobile spine and base of skull tumours. Knockdown of T in the cell line, U‐CH1, which showed polysomy of chromosome 6 involving 6q27, resulted in a marked decrease in cell proliferation and morphological features consistent with a senescence‐like phenotype. The U‐CH1 cell line was validated as representing chordoma by the generation of xenografts, which showed typical chordoma morphology and immunohistochemistry in the NOD/SCID/interleukin 2 receptor [IL2r]

Case report: imaging and surgical treatment of a snapping hip due to ischiofemoral impingement

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The imaging spectrum of peri-articular inflammatory masses following metal-on-metal hip resurfacing

mouse model. In conclusion, chromosomal aberrations resulting in gain of the T locus are common in sporadic chordomas and expression of this gene is critical for proliferation of chordoma cells in vitro. Copyright

Ischiofemoral impingement: a retrospective analysis of cases in a specialist orthopaedic centre over a four-year period.

An association between hip pain and quadratus femoris MRI abnormality with concurrent narrowing of the ischiofemoral space has been reported in a number of patients to date, raising the possibility that the muscular damage observed is due to ischiofemoral impingement [1]. Possible impingement has been noted primarily in middle-aged females either with or without a history of trauma or surgery, and associated snapping of the hip is a rarely described feature [1–3]. We report here on a 17-year-old girl who presented with post-traumatic hip pain; she later developed evidence of ischiofemoral narrowing and quadratus femoris edema on MRI in addition to an audible snapping. Surgical resection of the lesser trochanter was performed, relieving both her hip pain and the snapping. To our knowledge, this is the first reported case of non-iatrogenic ischiofemoral impingement with surgical confirmation. The diagnosis of ischiofemoral impingement should be considered in patients complaining of a snapping hip.

Osteoclast formation and function in pigmented villonodular synovitis

IntroductionResurfacing metal-on-metal hip arthroplasty is increasing in popularity, especially in younger patients. To date, studies indicate that the procedure is associated with a good outcome in the medium-term. Formation of a peri-articuar mass is a rarely reported complication. In this study we analyse the imaging findings in patients with resurfacing implants presenting to our institution with peri-articular masses identified on cross sectional imaging.Materials and methodsAll patients with documented peri-articular masses following resurfacing arthroplasty were included. The available imaging related to the masses was reviewed and the findings documented along with the patient’s demographics.ResultsThere were 10 patients (13 joints). All patients were female. Patients presented with periprosthetic anterior or posterolateral solid and cystic masses. The anterior masses involved psoas muscle and were predominately solid. The posterolateral masses were predominately cystic. In the three cases with bilateral arthroplasties, masses were detected in both hips. Histology in six cases showed features compatible with a type IV hypersensitivity reaction.ConclusionsThe preponderance of females, the bilateral nature of the masses and the histological features suggest that peri-articular masses following resurfacing arthroplasty is due to the metal hypersensitivity.

Durable Response of Spinal Chordoma to Combined Inhibition of IGF-1R and EGFR.

Background Ischiofemoral impingement is a recently identified cause of chronic hip pain, the pathophysiology and clinical features of which are poorly understood. Aim To determine the clinical significance of MRI findings of ischiofemoral impingement. Materials and Methods Retrospective search for cases of ischiofemoral impingement in the Nuffield Orthopaedic Centre, Oxford, over a 4 year period, and review of medical notes to identify correlation between clinical and MRI features. Results Sixteen hips in 13 patients with MRI signs of ischiofemoral impingement were identified. All patients were females with a median age of 36 years (range 17-80 years). In six patients the symptoms corresponded to the side of the quadratus femoris abnormality and narrowed ischiofemoral distance. In two patients the symptoms were on the same side as the abnormality but were more consistent with back pain and sciatica. In five patients the symptoms were not anatomically related to the abnormality. Abnormalities identified; seven patients had muscle oedema (six unilateral, one bilateral) and six had muscle wasting (four unilateral, two bilateral). Of the patients with quadratus femoris oedema, two had gluteus medius enthesopathy and one had hamstring enthesopathy. Two patients presented with a chronic loud clunking of the hip on walking. Conclusions Ischiofemoral impingement on MRI is seen in patients with pain localised to the ipsilateral buttock and in patients with symptoms unrelated to the abnormality. The condition may be associated with wasting or oedema of the quadratus femoris muscle on MRI and may occur secondary to injury in other muscles controlling movement of the hip such as the hamstrings and gluteus medius. Ischiofemoral impingement is a cause of a clunking hip.

Intraosseous schwannoma in schwannomatosis.

Pigmented villonodular synovitis (PVNS) is a synovial tumour‐like lesion that frequently causes osteolysis. PVNS contains numerous macrophages and osteoclast‐like giant cells. In this study, we have analysed the cytochemical and functional characteristics of mononuclear and multinucleated cells in PVNS and determined the cellular and humoral mechanisms underlying giant cell formation and resorption in PVNS. Giant cells and CD14+ and CD14− mononuclear cell populations were isolated from PVNS synovial tissue and cultured alone or in the presence and absence of the osteoclastogenic factors, RANKL and M‐CSF. Osteoclast formation and activity was assessed by expression of TRAP and evidence of lacunar resorption. Giant cells in PVNS expressed an osteoclast‐phenotype (CD51+, TRAP+, CD14−, HLA‐DR−) and were formed only in cultures of mononuclear cells that expressed the macrophage marker CD14. Osteoclast formation required RANKL and occurred in both the presence and absence of exogenous M‐CSF. CD14− cells in PVNS expressed RANKL. Lacunar resorption by PVNS‐derived giant cells was abolished by the addition of the bisphosphonate, zoledronate. Our findings indicate that osteoclasts form by a RANKL‐dependent mechanism from CD14+ mononuclear phagocytes in PVNS. Osteoclast formation occurred even in the absence of exogenous M‐CSF, a finding which is in keeping with over‐expression of M‐CSF playing a pathogenic role in this condition. Anti‐osteoclast resorptive treatment may be useful to control osteolysis in PVNS. Copyright