The course of secondary fracture healing typically consists of four major phases including inflammation, soft and hard callus formation, and bone remodeling. Callus formation is promoted by mechanical stimulation, yet little is known about the healing
Mesenchymal stem cells (MSCs) have the potential to repair and regenerate damaged
An injectable material consisting of calcium sulphate mixed with hydroxyapatite was investigated as a possible alternative to autograft in the restoration of bone defects. The material was studied both in vitro in simulated body fluid (SBF) and in vivo when implanted in rat muscles and into the proximal tibiae of rabbits. Variation in the strength and weight of the material during ageing in SBF was measured.
We have investigated whether the presence of polyethylene (PE) alone is sufficient to cause an aggressive periprosthetic
Little is known about the tissue reactions to various implant materials which coincide with an inflammatory reaction. We used the avridine arthritis rat model to evaluate the
Metal and their alloys have been widely used as implantable materials and prostheses in orthopaedic surgery. However, concerns exist as the metal nanoparticles released from wear of the prostheses cause clinical complications and in some cases result in catastrophic host
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
Summary Statement. A porcine model using Yucatan minipigs was found to be very promising for the investigation of healing around transcutaneous osseointegrated implants. Pigs demonstrated surprising agility and adaptability including the ability to ambulate on three legs during the immediate postoperative period. Introduction. Previous non weight-bearing and weight-bearing caprine, canine and ovine models have evaluated design, material, and biological coating variations in an attempt to improve the wound healing and skin-implant seal around transcutaneous osseointegrated implants. Although these models have primarily been used as a window into the application of transcutaneous osseointegrated implants in humans, some important model characteristics affecting wound healing and infection have been missing including: 1) replication of the physiological
We have studied the characteristics of bone ingrowth of a new porous tantalum biomaterial in a simple transcortical canine model using cylindrical implants 5 × 10 mm in size. The material was 75% to 80% porous by volume and had a repeating arrangement of slender interconnecting struts which formed a regular array of dodecahedron-shaped pores. We performed histological studies on two types of material, one with a smaller pore size averaging 430 μm at 4, 16 and 52 weeks and the other with a larger pore size averaging 650 μm at 2, 3, 4, 16 and 52 weeks. Mechanical push-out tests at 4 and 16 weeks were used to assess the shear strength of the bone-implant interface on implants of the smaller pore size. The extent of filling of the pores of the tantalum material with new bone increased from 13% at two weeks to between 42% and 53% at four weeks. By 16 and 52 weeks the average extent of bone ingrowth ranged from 63% to 80%. The
The pathogenesis of aseptic loosening of total joint prostheses is not clearly understood. Two features are associated with loosened prostheses, namely, particulate debris and movement of the implant. While numerous studies have evaluated the cellular response to particulate biomaterials, few have investigated the influence of movement of the implant on the biological response to particles. Our aim was therefore to test the hypothesis that excessive mechanical stimulation of the periprosthetic tissues induces an inflammatory response and that the addition of particulate biomaterials intensifies this. We allocated 66 adult Beagle dogs to four groups as follows: stable implants with (I) and without (II) particulate polymethylmethacrylate (PMMA) and moving implants with (III) and without (IV) particulate PMMA. They were then evaluated at 2, 4, 6, 12 and 24 weeks. The stable implants were well tolerated and a thin, fibrous membrane of connective tissue was observed. There was evidence of positive staining in some cells for interleukin-6 (IL-6). Addition of particulate PMMA around the stable implants resulted in an increase in the fibroblastic response and positive staining for IL-6 and tumour necrosis factor-alpha (TNF-α). By contrast, movement of the implant resulted in an immediate inflammatory response characterised by large numbers of histiocytes and cytokine staining for IL-1ß, TNF-α and IL-6. Introduction of particulate PMMA aggravated this response. Animals with particulate PMMA and movement of the implant have an intense inflammatory response associated with accelerated bone loss. Our results indicate that the initiation of the inflammatory response to biomaterial particles was much slower than that to gross mechanical instability. Furthermore, when there was both particulate debris and movement, there was an amplification of the adverse
Frozen shoulder is a chronic fibrosing condition of the capsule of the joint. The predominant cells involved are fibroblasts and myofibroblasts which lay down a dense matrix of type-I and type-III collagen within the capsule. This subsequently contracts leading to the typical features of pain and stiffness. Cytokines and growth factors regulate the growth and function of the fibroblasts of connective tissue and remodelling of the matrix is controlled by the matrix metalloproteinases (MMPs) and their inhibitors. Our aim was to determine whether there was an abnormal expression or secretion of cytokines, growth factors and MMPs in tissue samples from 14 patients with frozen shoulder using the reverse transcription/polymerase chain reaction (RT/PCR) technique and to compare the findings with those in tissue from four normal control shoulders and from five patients with Dupuytren’s contracture. Tissue from frozen shoulders demonstrated the presence of mRNA for a large number of cytokines and growth factors although the frequency was only slightly higher than in the control tissue. The frequency for a positive signal for the proinflammatory cytokines Il-1β and TNF-α and TNF-β, was not as great as in the Dupuytren’s tissue. The presence of mRNA for fibrogenic growth factors was, however, more similar to that obtained in the control and Dupuytren’s tissue. This correlated with the histological findings which in most specimens showed a dense fibrous
Aseptic loosening is a major cause of failure of total hip arthroplasty. The adverse
Introduction. Tendon disease and rupture are common in patients with diabetes and these are exacerbated by poor healing. although nanoscale changes in diabetic tendon are linked to increased strength and stiffness. The resistance to mechanical damage of a tissue may be measured using fatigue testing but this has not been carried out in diabetic tendon, although the toughness of diabetic bone is known to be reduced. The aim of this study was to measure the static fatigue behaviour of tendons from a streptozotocin (STZ)-induced rat model of diabetes, hypothesising that diabetes causes tendon to show lower resistance to mechanical damage than healthy tendon. Materials and Methods. Diabetic (n=3, 12 weeks post-STZ) and age-matched control (n=3) adult male Sprague Dawley rats were culled, tails harvested and stored at −80ºC. Following defrosting, fascicles (5 per animal) were carefully dissected, mean diameter measured using an optical micrometer and mounted in a Bose Biodynamics test machine using custom grips in a PBS bath. Static fatigue testing at 30 MPa to failure enabled both elastic modulus (initial ramp) and steady state creep rate (gradient at creep curve inflexion) to be measured. Data are reported as median ± interquartile range and pw0.05 using a Mann-Whitney U test was taken as significant. Results. Confirming previous reports, tendon from diabetic rats showed significantly higher elastic modulus (201 ± 68 MPa) than healthy (151 ± 62 MPa). Strain at failure showed no differences between groups. Tendon from diabetic rats showed significantly slower steady state creep (71 ± 44 μstrain s. −1. ) than healthy (691 ± 1000 μstrain s. −1. ). Discussion. These preliminary data show an order of magnitude larger resistance to mechanical damage in diabetic tendons, possibly associated with the previously reported increased packing and decreased fibril diameters. Energy-storing flexor tendons, the most commonly affected in diabetics, and the positional tendons tested here show similar fatigue behaviour when tested at the same fraction of “stress-in-life”. Further investigation is required into the cell
We investigated the effects on fracture healing of two up-regulators of inducible nitric oxide synthase (iNOS) in a rat model of an open femoral osteotomy: tadalafil, a phosphodiesterase inhibitor, and the recently reported nutraceutical, COMB-4 (consisting of L-citrulline, Paullinia cupana, ginger and muira puama), given orally for either 14 or 42 days. Unilateral femoral osteotomies were created in 58 male rats and fixed with an intramedullary compression nail. Rats were treated daily either with vehicle, tadalafil or COMB-4. Biomechanical testing of the healed fracture was performed on day 42. The volume, mineral content and bone density of the callus were measured by quantitative CT on days 14 and 42. Expression of iNOS was measured by immunohistochemistry.Objectives
Materials and Methods
The success of long-term transcutaneous implants
depends on dermal attachment to prevent downgrowth of the epithelium
and infection. Hydroxyapatite (HA) coatings and fibronectin (Fn)
have independently been shown to regulate fibroblast activity and
improve attachment. In an attempt to enhance this phenomenon we
adsorbed Fn onto HA-coated substrates. Our study was designed to
test the hypothesis that adsorption of Fn onto HA produces a surface
that will increase the attachment of dermal fibroblasts better than
HA alone or titanium alloy controls. Iodinated Fn was used to investigate the durability of the protein
coating and a bioassay using human dermal fibroblasts was performed
to assess the effects of the coating on cell attachment. Cell attachment
data were compared with those for HA alone and titanium alloy controls
at one, four and 24 hours. Protein attachment peaked within one
hour of incubation and the maximum binding efficiency was achieved
with an initial droplet of 1000 ng. We showed that after 24 hours
one-fifth of the initial Fn coating remained on the substrates,
and this resulted in a significant, three-, four-, and sevenfold
increase in dermal fibroblast attachment strength compared to uncoated controls
at one, four and 24 hours, respectively.
We used a biodegradable mesh to convert an acetabular defect into a contained defect in six patients at total hip replacement. Their mean age was 61 years (46 to 69). The mean follow-up was 32 months (19 to 50). Before clinical use, the strength retention and hydrolytic in vitro degradation properties of the implants were studied in the laboratory over a two-year period. A successful clinical outcome was determined by the radiological findings and the Harris hip score. All the patients had a satisfactory outcome and no mechanical failures or other complications were observed. No protrusion of any of the impacted grafts was observed beyond the mesh. According to our preliminary laboratory and clinical results the biodegradable mesh is suitable for augmenting uncontained acetabular defects in which the primary stability of the implanted acetabular component is provided by the host bone. In the case of defects of the acetabular floor this new application provides a safe method of preventing graft material from protruding excessively into the pelvis and the mesh seems to tolerate bone-impaction grafting in selected patients with primary and revision total hip replacement.