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Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_15 | Pages 32 - 32
7 Aug 2024
Raftery K Tavana S Newell N
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Introduction

Vertebral compression fractures are the most common type of osteoporotic fracture. Though 89% of clinical fractures occur anteriorly, it is challenging to replicate these ex vivo with the underlying intervertebral discs (IVDs) present. Furthermore, the role of disc degeneration in this mechanism is poorly understood. Understanding how disc morphology alters vertebral strain distributions may lead to the utilisation of IVD metrics in fracture prediction, or inform surgical decision-making regarding instrumentation type and placement.

Aim

To determine the effect of disc degeneration on the vertebral trabecular bone strain distributions in axial compression and flexion loading.


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_9 | Pages 24 - 24
1 Oct 2022
Tavana S Leong J Freedman B Newell N
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Background

In vivo evaluation of IVD strains is crucial to better understand normal and pathological IVD mechanics, and to evaluate the effectiveness of treatments. This study aimed to 1) develop a novel in vivo technique based on 3T MRI and digital volume correlation (DVC) to measure strains within IVDs and 2) to use this technique to resolve 3D strains within IVDs of healthy volunteers during extension.

Methods

This study included 40 lumbar IVDs from eight healthy subjects. The optimal MR sequence to minimise DVC uncertainties was identified by scanning one subject with four different sequences: CISS, T1VIBE, T2SPACE, and T2TSE. To assess the repeatability of the strain measurements in spines with different anatomical and morphological variations four subjects were scanned with the optimal sequence, and uncertainties of the strain measurements were quantified. Additionally, to calculate 3D strains during extension, MRIs were acquired from six subjects in both the neutral position and after full extension.


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_9 | Pages 9 - 9
1 Oct 2022
Rahman T Baxan N Murray R Tavana S Schaer T Smith N Bull J Newell N
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Introduction

Nucleus replacement surgery has the potential to be an early treatment option for chronic lower back pain. The surgery involves removal (nuclectomy) and replacement of the native degenerated nucleus with a material designed to restore the disc's physiological properties. Multiple techniques have been considered to perform a nuclectomy, however the advantages and disadvantages of each are not well understood. The aim of this study was to quantitatively compare three nuclectomy techniques: automated-shaver, rongeurs, and laser.

Methods and results

Fifteen human vertebra-disc-vertebra lumbar specimens were split into three groups. Before and after nuclectomy axial mechanical tests were performed and T2-weighted 9.4T MRIs were acquired for each specimen. Using the automated-shaver and rongeur similar volumes of disc material were removed (2.51±1.10% and 2.76±1.39% of the total disc volume, respectively), whilst considerably less material was removed when using the laser (0.12±0.07%). Using the automated-shaver and rongeur significantly reduced the toe-region stiffness, while the linear region stiffness was significantly reduced only in the rongeur group. From the MRIs, more homogeneous cavities were seen in the center of the disc when using the automated shaver compared to rongeur, whilst laser ablation resulted in small, localized cavities.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_2 | Pages 48 - 48
1 Mar 2021
Tavana S Freedman B Baxan N Hansen U Newell N
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Abstract

Objectives

Back pain will be experienced by 70–85% of all people at some point in their lives and is linked with intervertebral disc (IVD) degeneration. The aim of this study was to 1) compare 3D internal strains in degenerate and non-degenerate human IVD under axial compression and 2) to investigate whether there is a correlation between strain patterns and failure locations.

Methods

9.4T MR images were obtained of ten human lumbar IVD. Five were classed as degenerate (Pfirrmann = 3.6 ± 0.3) and five were classed as non-degenerate (Pfirrmann = 2.0 ± 0.2). MR Images were acquired before applying load (unloaded), after 1 kN of axial compression, and after compression to failure using a T2-weighted RARE sequence (resolution = 90 µm). Digital Volume Correlation was then used to quantify 3D strains within the IVDs, and failure locations were determined from analysis of the failure MRIs.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_7 | Pages 20 - 20
1 May 2018
Bonner T Masouros S Newell N Ramasamy A Hill A West A Clasper J Bull A
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The lower limbs of vehicle occupants are vulnerable to severe injuries during under vehicle explosions. Understanding the injury mechanism and causality of injury severity could aid in developing better protection. Therefore, we tested three different knee positions in standing occupants (standing, knee in hyper-extension, knee flexed at 20˚) of a simulated under‐vehicle explosion using cadaveric limbs in a traumatic blast injury simulator; the hypothesis was that occupant posture would affect injury severity.

Skeletal injuries were minimal in the cadaveric limbs with the knees flexed at 20˚. Severe, impairing injuries were observed in the foot of standing and hyper‐extended specimens. Strain gauge measurements taken from the lateral calcaneus in the standing and hyper-extended positions were more than double the strain found in specimens with the knee flexed position. The results in this study demonstrate that a vehicle occupant whose posture incorporates knee flexion at the time of an under‐vehicle explosion is likely to reduce the severity of lower limb injuries, when compared to a knee extended position.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_26 | Pages 16 - 16
1 Jun 2013
Bonner T Newell N Pullen A Bull A Masouros S
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Characterising material properties of ligaments is essential in the analysis of human morbidity and mortality of low-speed sporting accidents, high-speed road traffic accidents, and very high-speed battlefield injuries. At lower strain rates the elastic modulus and ultimate stress increase relative to strain rate, although very high strain rate testing has not been performed to date.

A porcine stifle joint lateral collateral ligament experiment was conducted that simulated the strain rates that occur during across a full range of different human knee ligament injuries. Tensile testing was performed at five strain rates, each an order of magnitude apart, in the range 100–104%/s. Seven specimens were tested at each rate. Three loading techniques were used: 1) screw-driven, 2) servo-hydraulic, 3) drop weight rig with tensile impact adaptor. Cross sectional area was measured by counting pixels on a standardized digital photograph of an alginate-paste cast of the mid-substance of each sample. Strain was measured directly from the mid-substance of each ligament by high-speed video extensometry. Stress-strain curves were produced and used to quantify the elastic modulus, failure strain and ultimate stress at each strain rate.

Across the range of strain rates, elastic modulus increased from 288 to 905 MPa (p< 0.05), and ultimate stress increased from 39.9 to 77.3 MPa (p< 0.05). A relationship between strain rate and both, elastic modulus and ultimate stress was identified. Strain rate sensitivity was not observed at very fast strain rates.

Ligament strength increases when strain rates are high. These data provide an explanation for very high strain rate failure of ligaments under extreme loading conditions, that can be considered protective of bone fracture, such as can be seen in traumatic through knee amputations in blast injuries.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_8 | Pages 15 - 15
1 Feb 2013
Ramasamy A Masouros S Newell N Bonner T West A Hill A Clasper J Bull A
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Current military conflicts are characterised by the use of the Improvised Explosive Device (IED). Improvements in personal protection, medical care and evacuation logistics have resulted in increasing numbers of casualties surviving with complex musculoskeletal injuries, often leading to life-long disability. Thus, there exists an urgent requirement to investigate the mechanism of extremity injury caused by these devices in order to develop mitigation strategies. In addition, the wounds of war are no longer restricted to the battlefield; similar injuries can be witnessed in civilian centres following a terrorist attack.

Key to mitigating such injuries is the ability to deconstruct the complexities of an explosive event into a controlled, laboratory-based environment. In this study, an anti-vehicle underbelly injury simulator, capable of recreating in the laboratory the impulse from an anti-vehicle (AV) explosion, is presented and characterised. Tests were then conducted to assess the simulator's ability to interact with human cadaveric legs. Two mounting conditions were assessed, simulating a typical seated and standing vehicle passenger using instrumented cadaveric lower limbs.

This experimental device, will now allow us (a) to gain comprehensive understanding of the load-transfer mechanisms through the lower limb, (b) to characterise the dissipating capacity of mitigation technologies, and (c) to assess the biofidelity of surrogates.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXII | Pages 3 - 3
1 Jul 2012
Bonner T Eardley W Newell N Masouros S Gibb I Matthews J Clasper J
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Circumferential pelvic binders have been developed to allow rapid closure of the pelvic ring in unstable fracture patterns. Despite evidence to support the use of pelvic binders, there is a paucity of clinical data regarding the effect of binder position on symphyseal diastasis reduction.

All patients presenting to the UK's military hospital in Afghanistan who survived and underwent pelvic radiography were reviewed. Cases were identified by retrospective assessment of all digital plain pelvic radiographs performed between January 2008 and July 2010. All radiographs and CT images were assessed to identify the presence of any pelvic fracture. Patients were grouped into three categories according to the vertical level of the buckle: superior to the trochanters (high), inferior to the trochanters (low) and at the level of the trochanters (troch). Diastasis reduction was measured in patients with Anterior-Posterior Compression (APC) grades II and III, or Combined Mechanical Injuries(CMI). Comparison of diastasis reduction between the high and troch groups was assessed by an independent samples Student's t-test.

We identified 172 radiographs where the metallic springs in the buckle of a SAM Pelvic Sling were clearly visible. The binders were positioned at the trochanteric level in 50% of radiographs. A high position was the commonest site of inaccurate placement (37%). In the patients with fractures and an open diastasis, the mean pelvic diastasis gap was 2.75 times greater in the high group compared to the trochanteric level (mean difference 22 mm) (p < 0.01).

Application of pelvic binders superior to the greater trochanters is commonplace and associated with inadequate fracture reduction, which is likely to delay cardiovascular recovery in these significantly injured casualties.


The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 11 | Pages 1524 - 1528
1 Nov 2011
Bonner TJ Eardley WGP Newell N Masouros S Matthews JJ Gibb I Clasper JC

The aim of this study was to assess the accuracy of placement of pelvic binders and to determine whether circumferential compression at the level of the greater trochanters is the best method of reducing a symphyseal diastasis.

Patients were identified by a retrospective review of all pelvic radiographs performed at a military hospital over a period of 30 months. We analysed any pelvic radiograph on which the buckle of the pelvic binder was clearly visible. The patients were divided into groups according to the position of the buckle in relation to the greater trochanters: high, trochanteric or low. Reduction of the symphyseal diastasis was measured in a subgroup of patients with an open-book fracture, which consisted of an injury to the symphysis and disruption of the posterior pelvic arch (AO/OTA 61-B/C).

We identified 172 radiographs with a visible pelvic binder. Five cases were excluded due to inadequate radiographs. In 83 (50%) the binder was positioned at the level of the greater trochanters. A high position was the most common site of inaccurate placement, occurring in 65 (39%). Seventeen patients were identified as a subgroup to assess the effect of the position of the binder on reduction of the diastasis. The mean gap was 2.8 times greater (mean difference 22 mm) in the high group compared with the trochanteric group (p < 0.01).

Application of a pelvic binder above the level of the greater trochanters is common and is an inadequate method of reducing pelvic fractures and is likely to delay cardiovascular recovery in these seriously injured patients.