14.1% of men & 22.8% of women over 45 years show symptoms of osteoarthritis OA of the knee [1]. Knee OA is usually associated with lower limb malalignment [2]; 50 of varus results in 70% −90% increase in compressive loading of the medial tibio-femoral compartment [3] and OA worsening over 18 months [4]. High Tibial Osteotomy (HTO) enables preservation of bone stock and soft tissue structures and could be an attractive option to younger patients who wish to return to high level activity. However, results of HTOs are unpredictable, which could be due to patient selection or surgical techniques. The long-term aim of this work is to develop a predictive tool to aid the surgeon in the selection of optimal HTO geometry for improved and more consistent surgical outcomes. The first step in achieving our longterm goal was to determine whether stress predictions at the tibio-femoral articulation were sensitive to simulated high tibial osteotomy, using finite element (FE) method.

CT and MRI data of a cadaveric knee were used to create geometrically accurate 3D models of the femur, tibia, fibula, menisci and cartilage and tendon of the knee joint, using the Mimics V12.11 commercially-available software (Materialise, Belgium). The Simulation module was used to register the bones and the soft tissues. The resulting STL files were exported to CATIA V5R18 pre-processor to generate surface meshes and create the corresponding 3D solid and FE models of the osseous and soft tissues from the STL cloud of points.

The Young’s moduli for cortical bone, cancellous bone, cartilages, menisci and ligaments were taken from literature as 17 GPa, 500 MPa, 12 MPa, 60 Mpa and 1.72 MPa respectively [5,6,7]. The Poisson’s ratios for osseous and soft tissues were taken as 0.3 and 0.45, respectively [8]. The nodes between the bones and the corresponding cartilages were merged and surface contact was applied between the cartilages. The distal ends of the tibia and fibula were fixed and a load of 2.1 KN, corresponding to 3 x body weight, was applied perpendicularly to the proximal end of the femur. Results of finite element analyses show a reduction of 67 % in principal stresses in the knee joint following an open wedge HTO surgery simulating 100 varus correction.

FE analysis results of this study show that HTO reduces stresses in specific regions of the knee, which are associated with OA progression [4]. Our future works include corroborating our results with controlled cadaveric experiments and implementing optimization techniques to predict optimum HTO geometries for patient-specific FE models.

Background: Over many years our understanding of fracture patterns and management has evolved. One of the biggest steps was the adoption of the principles of fracture fixation as described by the Arbitsgemeinschaft fur Osteosynthesefragen (AO). The application of this philosophy has allowed us to optimise fracture management and improve outcome.

In our unit we noted a number of complications resulting from suboptimal fracture fixations of ankles some of which required revision. It was decided to review fracture fixation of ankles in the unit to see whether the basic principles of fixation was being followed in our DGH.

Aim: To evaluate whether the AO principles of fixation for ankle fractures are being followed in our local unit.

Patients and Methods: 52 consecutive patients over a period of 1 year from August 2005 to August 2006 with bi malleolar and isolated medial malleolar ankle fractures, requiring surgery, had their case notes and pre operative x rays reviewed retrospectively looking at fracture patterns according to the AO and Weber classification. Post operative x rays where reviewed to see if the principles of facture fixation had been appropriately followed.

Results: Of the 52 patients evaluated 26 were Weber type B fractures, 20 were type C and 6 were isolated medial malleolar fracture. Nine of the type B and three of type C (23% of the total number) underwent fixation not in accordance with AO principles.

In every case the fibula fixation did not include a cortical lag screw.

Discussion/Conclusions: Although none of the 12 described had to undergo revision, their management was far from optimum.

By ensuring that operating surgeons have the appropriate training and experience in basic fracture fixation before being allowed to undertake such procedures, our unit hopes to show an improvement on these figures by the time this audit is repeated.

The reduced stability of hydroxyapatite (HA)-coated implants in osteopenic conditions is considered to be a major problem. We therefore developed a model of a boosted cementless implantation in osteopenic rats.

Twelve-week-old rats were either ovariectomised (OVX) or sham-operated (SO), and after 24 weeks plain or HA-coated implants were inserted. They were treated with either a prostaglandin EP4 receptor agonist (ONO-4819) or saline for one month.

The EP4 agonist considerably improved the osteoporosis in the OVX group. Ultrastructural analysis and mechanical testing showed an improvement in the implant-bone attachment in the HA-coated implants, which was further enhanced by the EP4 agonist. Although the stability of the HA-coated implants in the saline-treated OVX rats was less than in the SO normal rats, the administration of the EP4 agonist significantly compensated for this shortage. Our results showed that the osteogenic effect of the EP4 agonist augmented the osteoconductivity of HA and significantly improved the stability of the implant-bone attachment in the osteoporotic rat model.