Bioabsorbable screws for anterior cruciate ligament reconstruction (ACLR) have been shown to be associated with femoral tunnel widening and cyst formation.

To compare a poly-L-lactide–hydroxyapatite screw (PLLA-HA) with a titanium screw with respect to clinical and radiological outcomes over a 5 year period.

40 patients were equally randomized into 2 groups (PLLA-HA vs titanium) and ACLR performed with a 4 strand hamstring graft with femoral tunnel drilling via the anteromedial portal. Evaluation at 2 and 5 years was performed using the International Knee Documentation Committee assessment (IKDC), Lysholm knee score, KT 1000 arthrometer, single-legged hop test. Magnetic resonance imaging was used to evaluate tunnel and screw volume, ossification around the screws, graft integration and cyst formation.

There was no difference in any clinical outcome measure at 2 or 5 years between the 2 groups. At 2 years, the PLLA-HA femoral tunnel was significantly smaller than the titanium screw tunnel (p=0.015) and at 5 years, there was no difference. At 2 years the femoral PLLA-HA screw was a mean 76% of its original volume and by 5 years, 36%. At 2 years the tibial PLLA-HA screw mean volume was 68% of its original volume and by 5 years, 46%. At 5 years, 88% of femoral tunnels and 56% of tibial tunnels demonstrated a significant ossification response. There was no increase in cyst formation in the PLLA-HA group and no screw breakages.

The PLLA-HA screw provides adequate aperture fixation in ACLR with excellent functional outcomes. It was not associated with femoral tunnel widening or increased cyst formation when compared with the titanium screw. The resorbtion characteristics appear favourable and the hydroxyapatite component of the screw may stimulate osteoconduction, contributing to these results. The PLLA-HA screw is a good alternative to a titanium screw in ACLR, which may aid revision procedures and allow for imaging without artifact.

Introduction

Debate remains which surgical technique should be used for ankle arthrodesis. Several open approaches have been described, as well as the arthroscopic method, using a variety of fixation devices.

Both arthroscopic and open procedures have good results with union rates of 93–95%, 3% malunion rate and patient satisfaction of 70–90%, although some report complication rates as high as 40%.

Introduction

Adolescent idiopathic scoliosis (AIS) is the most common paediatric spinal deformity, affecting about 3% of school-aged children worldwide. This disorder occurs in otherwise healthy children who bear no obvious deficiencies in the components of the spinal column itself. The cause of AIS is poorly understood, as is implied by the name. Lesions of the bony composition of the vertebrae, the vertebral endplates, the paraspinous muscles, or the neurological system each have been proposed to explain disease pathogenesis. Progress has been hampered by the absence of an obvious AIS animal model. Consequently we have used genetic studies in human populations to identify factors underlying AIS susceptibility.

The complex inheritance and population frequency of AIS suggest that many genetic factors are involved in this disease. To search comprehensively for such factors we previously undertook the first genome-wide association study (GWAS) of AIS susceptibility in a cohort of 419 families in Texas, USA. We found that chromosome 3 SNPs in the proximity of the CHL1 gene yielded strongest results, which we replicated in additional cohorts (rs10510181 OR 1·49, 95% CI 1·29–173, p=2·58×10–8). CHL1 is of interest because it encodes an axon guidance protein and is functionally related to the ROBO3 gene that causes hereditary gaze palsy with progressive scoliosis (HGPPS), a rare disease marked by severe scoliosis. Here we expanded the study to 702 Texas families.

Introduction

The Rapid Recovery Program (RRP) is a holistic perioperative accelerated discharge process that aims to improve efficiency and quality of care, improve patient education, standardise protocols and pathways and encourage early mobilisation & discharge.

Introduction: Cell adhesion to titanium alloy implants is important in osseointegration [1,2] and attachment of the soft tissues to skin penetrating implants e.g. external fixator pins and Intraosseous Transcutaneous Amputation Prostheses [3,4]. Cell adhesion can be assessed using cell area data and immunolocalisation of focal contact proteins e.g. vinculin; however no method of assessing biophysical attachment is performed routinely. Cell adhesion can be enhanced with adhesion proteins including fibronectin (Fn)[5]. We have previously shown that covalently binding Fn to titanium also increases cell adhesion, and produces a more robust protein coating [6]. However the strength of adhesion of cells to this coating has not been measured. Our hypothesis was that biophysical cell adhesion measured using novel radial flow apparatus would correlate with cell area and focal contact data and that covalently bound fibronectin substrates would increase cell adhesion compared with adsorbed and uncoated controls.

Method: Dermal fibroblasts were cultured for 1, 4, and 24 hours on 30mm and 10mm diameter polished titanium alloy discs (n = 6). Cells on 30mm discs were calcein stained and subjected to shear stress in a submerged, media filled, custom-made radial flow apparatus at 37¬C at 1.66ml/s for 15s. Cells were fixed in 10% formal saline and photographs were taken using a tangential light source. Fluorescent microscopy was performed at 2mm intervals along two perpendicular diameters. Using image analysis, the central cell free zone was measured and radial distance and shear stress calculated. Cells on 10mm discs were fixed, permeablised and vinculin stained (mouse vinculin antibody (1:200) 2hrs; FITC mouse antibody (1:100)1hr). Images were analyzed with a Zeiss microscope linked to image analysis software and the number of focal contacts were counted per cell area. The medians of the radial flow data were compared with data for cell area and focal contact production at the same time points using Spearman¡s regression correlation. This method was subsequently used to compare cell adhesion at one hour with adsorbed and covalently bound Fn substrates (10¥ìg/disc).

Results/Discussion: The shear strength of cells increased between 4 and 24hrs (p=0.002) on polished untreated control substrates. Attachment values (dynes/cm2) were 84.90 (73.98–97.19), 96.30 (91.66–100.89), and 136.69 (134.68–140.30) for 1, 4 and 24 hours respectively. At 1hr, covalently bound Fn (509.90 dynes/cm2 (490.55–528.49) significantly increased cell adhesion compared with adsorbed Fn(434.45 dynes/cm2(385.25–465.62)) and control substrates(p=0.002). There was significant correlation between shear stress and focal contacts/cell (1.00(p< 0.01)) and focal contacts/cell area (0.900(p=0.037)), but not cell area (0.600(p=0.285)).

Conclusion: Radial flow measurement is a useful direct method to quantify cell adhesion to orthopaedic implants and correlates well with other methods of measurement. Covalently bound Fn significantly increases biophysical cell attachment compared with adsorbed and uncoated controls.

Introduction: Intraosseous Transcutaneous Amputation Prostheses (ITAP) could overcome the problems associated with conventional stump-socket prostheses for amputees (pressure sores, pain, infections and unnatural gait), by attaching the external prosthesis directly to the skeleton via a skin penetrating abutment. Despite this, the skin breach introduces a potential route for infection. For success, a biological seal at the skin-ITAP interface is essential.

The protein Laminin-5 (L-5) is a ‘biological glue’, which is integral to epitheial cell adhesion. Covalently bonding L-5 to the ITAP titanium alloy (Ti6Al4V), may enhance the strength of the skin-ITAP interface.

Silanisation, a chemical technique that covalently bonds proteins to metals, could be used to bond L-5 to Ti6Al4V. We have assessed the characteristics L-5 silanised Ti6Al4V as a potential substrate for ITAP.

Method: To determine the maximum quantity of L-5 that could be silanised to Ti6Al4V, and its relative stability when soaked in foetal calf serum (FCS) over time; polished Ti6Al4V discs were silanised by immersing in aminopropyltriethoxysilane followed by glutaraldehyde. Radiolabelled rat laminin-5-I125 was then added. Discs were immersed in FCS for 4 days (37 C) and analysed at 24 hour intervals in a liquid scintillation counter. Un-silanised discs were used as controls.

Results: L-5 was successfully covalently bound to Ti6Al4V. 10ng, 100ng, 250ng and 500ng droplets yielded significantly more silanised L-5 (p< 0.05), but no difference was observed between 750ng and 1000ng. Percentage L-5 covalently bound ranged from 33% and 65%.

A small decrease in bound L-5 occurred after 24 hours of FCS soaking (p< 0.05), but subsequent to this no significant reduction was observed for 4 days (p< 0.05). Controls showed a significantly larger reduction after 24 hours (p< 0.05).

Conclusion: Covalently bonding L-5 to Ti6Al4V by silanisation can be achieved with predictable results. Large enough quantities can be immobilised to influ-ence cellular function. L-5 silanised to Ti6Al4V remains stable in vitro over time and is not removed. Following the study of cellular interactions with silanised L-5, a stable skin seal may be achieved at the transcutaneous portion of the ITAP.

Conventional amputation prostheses rely on the attachment of the socket to the stump, which may lead to soft-tissue complications. Intraosseous transcutaneous amputation prostheses (ITAPs) allow direct loading of the skeleton, but their success is limited by infection resulting from breaching of the skin at the interface with the implant. Keratinocytes provide the skin’s primary barrier function, while hemidesmosomes mediate their attachment to natural ITAP analogues. Keratinocytes must attach directly to the surface of the implant. We have assessed the proliferation, morphology and attachment of keratinocytes to four titaniumalloy surfaces in order to determine the optimal topography in vitro. We used immunolocalisation of adhesion complex components, scanning electron microscopy and transmission electron microscopy to assess cell parameters.

We have shown that the proliferation, morphology and attachment of keratinocytes are affected by the surface topography of the biomaterials used to support their growth. Smoother surfaces improved adhesion. We postulate that a smooth topography at the point of epithelium-ITAP contact could increase attachment in vivo, producing an effective barrier of infection.

Introduction: Transcutaneous Amputation Prosthesis (ITAP) is an alternative for transfemoral amputees to conventional stump-socket prostheses which have many problems. These include: poor fit, stump pressure sores, pain, infections and unnatural gait. ITAP aims to overcome these by being osseointegrated into the femoral medulla with a pin protruding through the skin to which the external prosthesis attaches. Thus, the forces normally encountered by the stump soft tissues are now transferred directly to the skeleton. However, the transcutaneous pin produces a route for infection from the external to internal environment. Therefore, a key feature to the success of the ITAP is to produce a biological seal at the transcutaneous interface. Epithelial cells have been shown to attach to dental transcutaneous titanium devices via hemidesmosomes (HD).2 Focal contacts (FC) are also important in cell adhesion and to the underlying substratum.3 We grew human keratinocytes on different titanium surfaces to assess their morphology, ability to proliferate and produce HD and FC. Hypothesis: Surface topography influences keratinocytes morphology and proliferative capacity and expression of HD and FC.

Materials and Methods: 4 titanium alloy (Ti6Al4V) surface topographies were used (10mm x 4mm discs): polished, machine finished, sandblasted and hydrofluoric acid etched (HF) and a control – plastic thermanox. Surface roughness profiling of titanium discs were measured (Mitutoyo Surftest SV-400). HaCaT keratinocytes were grown on disc surfaces in wells of culture medium at +37oC, 5% CO2 and analysed at 1, 2, 3 and 4 days. Cells were processed to visualise HD with fluorescence microscopy using antibodies to the 6-integrin and plec-tin. Anti-vinculin antibodies were used to visualise FC. Fluorescein isothiocyanate (FITC) secondary antibodies enabled counting of structures (all product: Sigma-Aldrich, UK). Alamar blue (Serotec, UK) measured cell proliferation and SEM (surface morphology, cell area) and TEM were also performed. Cells grown on polished, machined and thermanox discs supported a regular, confluent layer with many cytoplasmic processes and dividing cells. HF and sandblasted discs grew an irregularly layer with fewer cytoplasmic processes and fewer dividing cells (not quantified). Day 3 TEM revealed HD, FC and desmosomes; cells on polished and thermanox were more closely packed and in layers.

Conclusion: Keratinocytes are significantly influenced by titanium surface topography. Smooth polished titanium alloy may be the ideal surface for a transcutaneous pin in the ITAP. Further experiments into isolating favourable biological components needed to encourage keratinocytes to attach onto titanium should be carried out.

Results: No significant difference shown in cell proliferation between titanium discs but cells on thermanox grew significantly more (p< 0.05). FC and HD numbers increased on all surfaces (days 1–3); a negative correlation between surface roughness and HD and FC numbers observed (lower Ra values = more HD and FC expressed).