Advertisement for orthosearch.org.uk
Results 1 - 5 of 5
Results per page:
Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_5 | Pages 143 - 143
1 Apr 2019
Hillstrom R Morgan OJ Rozbruch SR Fragomen AT Ranawat A Hillstrom H
Full Access

Introduction

Osteoarthritis (OA), a painful, debilitating joint disease, often caused by excessive joint stress, is a leading cause of disability (World Health Organisation, 2003) and increases with age and obesity. A 5° varus malalignment increases loading in the medial knee compartment from 70% to 90% (Tetsworth and Paley, 1994). Internal unloading implants, placed subcutaneously upon the medial aspect of the knee joint, are designed to offload the medial compartment of the knee without violating natural joint tissues. The aim of this study is to investigate the effect of an unloading implant, such as the Atlas™ knee system, on stress within the tibiofemoral joint with different grades of cartilage defects.

Methods

To simulate surgical treatment of medial knee OA, a three-dimensional computer-aided design of an Atlas™ knee system was virtually fixed to the medial aspect of a validated finite element knee model (Mootanah, 2014), using CATIA v5 software (Dassault Systèmes, Velizy Villacoublay, France). The construct was meshed and assigned material properties and boundary conditions, using Abaqus finite element software (Dassault Systèmes, Velizy Villacoublay, France). A cartilage defect was simulated by removing elements corresponding to 4.7 mm2. The international cartilage repair society (ICRS) Grade II and III damage were simulated by normalized defect depth of 33% and 67%, respectively. The femur was mechanically grounded and the tibia was subjected to loading conditions corresponding to the stance phase of walking of a healthy 50-year-old 68-Kg male with anthropometrics that matched those of the cadaver. Finite element analyses were run for peak shear and von Mises stress in the medial and lateral tibiofemoral compartments.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_14 | Pages 111 - 111
1 Nov 2018
Kraszewski A Drakos M Hillstrom H Toresdahl B Allen A Nwawka O
Full Access

This investigation of elite male collegiate basketball players aims to determine 1) the change in 3D dynamic functional variables across a single season and 2) correlate cross-season changes in functional variables with changes in clinical and quantitative ultrasound measures. Eleven male college basketball players (mean age 19, range 18–21 years) from a single team underwent baseline patellar tendon shear wave (SW) elastography and dynamic function at the start of the season (Visit1) and at a late-season time point (Visit2). Players reported their VISA-P scores every two weeks across their 24-week season. Each athlete performed a box-ground-box jump five times while 3D lower extremity kinematic and kinetic variables were collected. Functional measures included for landing (LAND) and take-off (TOFF) phases: knee valgus angle, valgus torque, and peak limb force. Knee valgus angular impulse and ground contact time were also measured. Paired t-tests and Pearson correlation coefficients (r) compared Visit1 and Visit2 variables and assessed the strength of linear dependency, respectively. The mean change in VISA-P score was 15.18 (+/-8.55). No functional variables were different across the season. Clinical, quantitative ultrasound and functional variables were moderately correlated with take-off valgus moment, landing force, take-off force and contact time. Other correlations were low (< 0.4). Our analyses have shown moderate correlations between important clinical, quantitative imaging and function measurements. These correlations reflect the changes that occur between relevant time points and which relate internal structure and external function.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_9 | Pages 54 - 54
1 May 2016
Carpanen D Hillstrom H Walker R Reisse F Cheah K Mootanah R
Full Access

Introduction

Partial meniscectomy, a surgical treatment for meniscal lesions, allows athletes to return to sporting activities within two weeks. However, this increases knee joint shear stress, which is reported to cause osteoarthritis. The volumes and locations of partial meniscectomy that would result in a substantial increase in knee joint stress is not known. This information could inform surgeons when a meniscus reconstruction is required.

Aim

Our aim was to use a previously validated knee finite element (FE) model to predict the effects of different volumes and locations of partial meniscectomy on cartilage shear stress. The functional point of interest was at the end of weight acceptance in walking and running, when the knee is subjected to maximum loading.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_21 | Pages 13 - 13
1 Apr 2013
Russell R Mootanah R Truchetet A Rao S Hillstrom H
Full Access

Introduction

Osteoarthritis commonly affects the first metatarsophalangeal joint. Stress across this joint has been postulated to increase the incidence of osteoarthritis. Certain foot structures have been associated with a higher incidence of osteoarthritis of the big toe. Utilizing finite elemental analysis, bone stress across the first metatarsophalangeal joint was calculated during mid stance phase of gait and compared in different foot structures.

Method

A geometrically accurate three dimensional model of the first metatarsophalangeal joint was created utilising a high resolution 7 tesla MRI and Mimics v14 imaging software. Planus, rectus and cavus feet were simulated by varying the metatarsophalangeal declination angle to 10.1, 20.2 and 30.7 degrees, respectively. A non-manfold computer aided design technique in Mimics v14.2 and finite element method in ANSYS v12 FE were utilised to create the boundary conditions, representing the double support stance phase of gait. Using information from 61 asymptomatic patients with different foot types walking over a Novel emed-x plantar pressure measuring system, plantar loading conditions were applied. Finite elemental analysis was used to predict stress in the first metatarsophalangeal joint in the different foot types.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_IV | Pages 440 - 440
1 Nov 2011
Mootanah R Hillstrom H New A Imhauser C Walker R Cheah K Blanc E Mangeot S Daré C Mouton C Burton A Ali SA Dowell J
Full Access

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.