Metal-on-metal (MOM) hip resurfacings release chromium and cobalt wear debris into the surrounding joint. The hip tissue taken from failed MOM hips shows specific histological features including a subsurface band-like infiltrate of macrophages with particulate inclusions, perivascular lymphocytic infiltrate and fibrin exudation. This tissue response has been called Aseptic Lymphocytic Vasculitis Associated Lesion (ALVAL). There is a recognised carcinogenic potential associated with hexavalent chromium and epidemiological data from first generation MOM arthroplasties may suggest an increased incidence of haematological malignancy. The ALVAL type reaction includes a marked proliferation of lymphocytes in the perivascular space and thorough investigation of this lymphocytic response is warranted. This study aims to further characterise the lymphocytic infiltrate using immunohistochemistry and to test clonality using polymerase chain reaction (PCR). Tissues from revised all cause failed MOM hip arthroplasties (n=77) were collected and analysed initially using routine H&E staining. Those that met the diagnostic criteria of ALVAL described above (n=34) were further stained with a panel of immunohistochemical markers (CD3, CD4, CD8 (T-cell markers) and CD20 (B-cell marker)). 10 representative ALVAL cases were selected and sent for gene rearrangement studies using PCR to determine whether the lymphocytes were polyclonal or monoclonal in nature. The analysis of the lymphocytic aggregates in ALVAL, showed a mixed population of B and T cells. Within the aggregates, there was a predominance of B cells (CD20) over T cells (CD3). Of the 10 cases which were analysed by PCR, 7 were suitable for interpretation. None of these cases showed evidence of monoclonal lymphocyte proliferation. The carcinogenic potential of wear debris from MOM hips, particularly affecting the haematopoietic system should be investigated. This study has shown a predominantly B-lymphocyte response in tissues surrounding MOM hips which is polyclonal. Although the numbers are small, the study suggests an immune mediated response in MOM hip tissue and excludes a neoplastic proliferation. However, long term follow up of patients with MOM hips may be prudent.
linear wear rate (depth of the femoral head and acetabular socket wear patch/time from operation); the diagnosis and severity of ALVAL from histological sections of periprosthetic tissue (Wilhert grading system); pre-revision whole blood cobalt, and chromium levels using Inductively Coupled Plasma Mass Spectrometry. All implants and tissue samples were analysed against control samples from patients undergoing revision of MOM hips for fractured femoral neck or impingement.
The purpose of this study was to determine and compare the effects of radiofrequency ablation and mechanical shaving on tendon using histological and ultrastructural techniques. A single cut using a scalpel blade was used to create a standardised reproducible lesion in 12 freshly harvested ovine infraspinatus tendons. Each lesion was then subjected to either bipolar radiofrequency ablation or mechanical shaving. Specimens were either fixed in formalin and processed for light microscopy or fixed in glutaraldehyde and processed for transmission electron microscopy. Samples of normal and untreated cut tendon were analysed as suitable controls. The radiofrequency treated samples showed an area of coagulative necrosis with an average diameter of 2mm around the lesion. Conversely, the shaved samples showed viable cells up to the edges of the lesion. These findings were supported by ultrastructural appearances, which showed preservation of tendon architecture in shaved samples and widespread denaturation of the tendon matrix with loss of fibrillar structure in the radiofrequency treated samples. Radio-frequency electrical energy and mechanical shaving are often used for resection of soft tissues during arthroscopic reconstructive procedures. The effects of these techniques on tendon are not yet clearly understood. The results of this study indicate that thermal resection of tendon causes an immediate additional 2mm area of tissue necrosis which is not present after mechanical shaving. These findings may have implications for the success of arthroscopic debridement and tendon repair procedures.
Vascular Endothelial Growth Factor (VEGF) has been shown to stimulate angiogenesis in a number of tissues and, in addition, to possess direct vasoactive properties. Stimulation of blood flow and angiogenesis are important features of the fracture healing process, particular in the early phases of healing. Inadequate vascularity has been associated with delayed union after fracture. The periosteum, and in particular its osteogenic cambial layer, has been shown to be very reactive to fracture and to contribute substantially to fracture healing. Fracture haematoma contains a considerable concentration of VEGF and enhanced plasma levels are observed in patients with multiple trauma. VEGF has been suggested to play a role during new bone formation possibly providing an important link between hypertrophic cartilage, angiogenesis and consequent ossification. However, the expression of VEGF in normal periosteum and in periosteum close to a fracture has not been previously reported. We hypothesise that the expression of VEGF in long bone periosteum will show a distinct response to fracture. We investigated the expression of VEGF In Group 1 the periosteum showed abundant but delicate blood vessels staining throughout for VEGF but there was no other visible staining of other structures or cells. In Group 2 the vasculature in the periosteum close to the fracture site demonstrated a characteristic, time-dependent course of expression of VEGF. At 24 and 48h following fracture the vasculature showed a heterogenous picture. The vessels in periosteum showed signs of activation: thickened endothelia and dilated lumina, but did not express VEGF. At 60h the vessels began to show signs of the presence of VEGF protein and by 4 days most periosteal vessels expressed VEGF. Also at this time, VEGF staining was visible in some of the stromal cells of the periosteum that was not seen in any of the earlier times. At 9 days VEGF was visible not only in the omnipresent vasculature, but now consistently in spindle shaped cells of fibroblastic appearance and chondrocytes throughout the early callus. This study, though limited by the number of patients, shows for the first time the expression of VEGF in normal periosteum as well as in periosteum during fracture healing. Interestingly, activated vessels in the early healing phase show little expression of VEGF; however it is known that the fracture haematoma contains VEGF in abundance. It is possible that the vasoactive role of VEGF prevails in these early days. There may be a critical time point at around 48h post fracture following which angiogenesis begins and VEGF is expressed in the endothelium throughout the vessel wall. The study suggests an important role for VEGF in the regulation of fracture healing. VEGF is not only expressed in endothelial cells within the periosteum but also in fibroblast-like stem cells and chondrocytes throughout the early callus suggesting it may play an important role in both osteo- and angiogenesis
Radio frequency (RF) electrothermal capsulorrhaphy has potential to enhance the results of arthroscopic stabilisation. However, early clinical reports have shown variable results when compared with open stabilisation. Numerous experiments have shown that the mechanical properties of thermally treated tissue are mechanically inferior to normal tissue during the early phase of remodelling. Ultimately, the real issue is how thermally treated tissue compares with tissue shortened by surgical plication, as would occur in an open procedure. Using a validated technique the tibial insertion of the medial collateral ligament (MCL) of the knee was shifted proximally to induce abnormal laxity in 30 mature NZ White rabbits. Bipolar RF shrinkage was applied to the MCL in 15 rabbits, while in the remainder the MCL was surgically transected and plicated with a nonabsorbable suture. Unlimited mobilisation was permitted until euthanasia at 12 weeks after surgery. Bone-ligament-bone complexes were harvested and underwent low-load (viscoelastic) and high-load (tensile failure) analysis on an Instron mechanical testing apparatus. Specimens from intact MCLs were also collected for polarised light microscopy and transmission electron micrography. Quantitative analysis of collagen fibril morphology was performed on the TEM images. There were no significant complications postoperatively. In both groups there was evidence of ligament healing and remodelling with a thin layer of scar tissue surrounding the MCL. Preliminary analysis has demonstrated that the cross-sectional area of the thermally treated MCLs was increased compared with the plicated MCLs. Somewhat surprisingly, the plicated group had greater vascularity and cellularity in the healing zone than the thermal group. Although crimp patterns remained disorganised in both groups, the collagen matrix appeared more organised in the thermal group. These results support the concept that the thermally denatured matrix may act as a scaffold for rapid remodelling of the MCL, resulting in a larger mass of ‘scar’ tissue at the site of shrinkage. Since scar tissue following surgical transection is known to be materially inferior to normal ligament tissue, the increased volume in the thermal group may confer an advantage in structural terms. Mechanical testing is presently underway in our laboratory to determine this issue.
Osteofibrous dysplasia is a rare condition usually affecting the tibiae and fibulae of males in the first two decades of life. Involvement at the ulna has also been reported in some cases. We describe an extensive, rapidly progressive lesion of the ulna in a three-year-old girl. The progression of the disease accelerated after a local marginal removal, and required extensive resection of the ulna with reconstruction using a fibular autograft. The particular features of this case are the change in the aggressive nature of the condition, which has not been previously reported. We believe that this is only the second recorded case of histologically proven involvement of the ulna.
Needle biopsy is an established technique for the histological diagnosis of bone tumours, usually guided by fluoroscopy or CT. Surface lesions and aggressive tumours which have extended through the cortex are also amenable to imaging with ultrasound (US). We have assessed the diagnostic accuracy of US-guided Trucut needle biopsy in a consecutive series of patients referred to a Bone Tumour Unit with suspected primary bone tumours. Of 144 patients (83 men, 61 women; mean age 34.7 years) referred over a period of two years, 63 were considered suitable for US-guided biopsy. This was based on the presence of a relatively large extraosseous component, seen typically in osteosarcoma and malignant round-cell tumours. The results of needle biopsy were compared with those of surgical biopsy. The diagnostic accuracy was 98.4%, with only a single failed biopsy. Thus, in a selected group of patients, US is a very reliable technique of guidance for percutaneous needle biopsy of bone tumours.