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Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_2 | Pages 31 - 31
1 Mar 2021
Hopwood J Redmond A Chapman G Richards L Collins S Brockett C
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Abstract

Objectives

Implant loosening remains a common cause of total ankle replacement (TAR) revision, and has been associated with wear-mediated osteolysis. Limited pre-clinical studies for TARs have been reported and the variety of experiment settings make it difficult to compare wear rates. Factors such as simulator control mechanism; whether pneumatic or electromechanical, may influence the integrity of the simulator outputs with respect to input profiles. This study compares the wear of a TAR, tested in electromechanical and pneumatic experimental simulators under identical input conditions.

Methods

Twelve medium BOX® (MatOrtho Ltd) TARs (n=6 for each simulator) were tested in an electromechanical and pneumatic knee simulator (Simulation Solutions, UK) for 3 million cycles (Mc). Standard ‘Leeds’ displacement-controlled inputs were used. Kinematic performance was investigated by comparing the output profiles against the maximum demanded input values. The lubricant used was 25% new-born calf serum and wear was determined gravimetrically.


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_1 | Pages 64 - 64
1 Feb 2020
Hopwood J Redmond A Chapman G Richards L Collins S Brockett C
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Background

Total ankle arthroplasty (TAA) is an alternative to ankle arthrodesis, replacing the degenerated joint with a mechanical motion-preserving alternative. Implant loosening remains a primary cause of TAA revision, and has been associated with wear-mediated osteolysis. Differing implant designs have a major influence on the wear performance of joint replacements. Providing a range of implant sizes allows surgeons a greater intra-operative choice for varying patient anatomy and potential to minimise wear. Minimal pre-clinical testing exists in the literature that investigates the effect of implant size on the wear behaviour. The aim of this study therefore was to investigate the effect of two different implant sizes on the wear performance of a TAA.

Materials & Methods

Six ‘medium’ and six ‘extra small’ BOX® (MatOrtho Ltd, UK) TAA implants, of the same conceptual design and polyethylene insert thickness, were tested in a modified 6 station pneumatic knee simulator. 5 million cycles (Mc) of wear simulation were completed for each implant size, under kinematics aiming to replicate an ankle gait cycle (Figure 1) [1]. The simulator used had six degrees of freedom, of which four were controlled. The maximum axial load was 3150N, equivalent to 4.5 times body weight of a 70kg individual. The flexion profile ranged from −15° plantarflexion to 15° dorsiflexion. Rotation about the tibial component ranged from −2.3° of internal rotation to 8° external rotation, and anterior/posterior (AP) displacement ranged from 3.1 mm anterior to −0.9 mm posterior displacement. The lubricant used was 25% bovine serum supplemented with 0.04% sodium azide to prevent bacterial degradation. The wear of the TAA polyethylene inserts were determined gravimetrically after each Mc, with unloaded soak controls used to compensate for the uptake of moisture by the polyethylene.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_2 | Pages 33 - 33
1 Jan 2019
Hopwood J Chapman G Redmond A Richards L Brockett C
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Total ankle replacement (TAR) is a substitute to ankle fusion, replacing the degenerated joint with a mechanical motion-conserving alternative. Compared with hip and knee replacements, TARs remain to be implanted in much smaller numbers, due to the surgical complexity and low mid-to-long term survival rates. TAR manufacturers have recently explored the use of varying implant sizes to improve TAR performance. This would allow surgeons a wider scope for implanting devices for varying patient demographics. Minimal pre-clinical testing has been demonstrated to date, while existing wear simulation standards lack definition. Clinical failure of TARs and limited research into wear testing defined a need for further investigation into the wear performance of TARs to understand the effects of the kinematics on varying implant sizes.

Six medium and six extra small BOX® (MatOrtho) TARs will be tested in a modified knee simulator for 5 million cycles (Mc). The combinations of simulator inputs that mimic natural gait conditions were extracted from ankle kinematic profiles defined in previous literature. The peak axial load will be 3.15 kN, which is equivalent to 4.5 times body weight of a 70kg individual. The flexion profile ranges from 15° plantarflexion to 15° dorsiflexion. Rotation about the tibial component will range from −2.3° of internal rotation to 8° external rotation, while the anterior/posterior displacement will be 7mm anterior to −2mm posterior throughout the gait cycle. The components will be rotated through the simulation stations every Mc to account for inter-station variability. Gravimetric measurements of polyethylene wear will be taken at every Mc stage. A contact profilometer will also be used to measure average surface roughness of each articulating surface pre-and-post simulation.

The development of such methods will be crucial in the ongoing improvement of TARs, and in enhancing clinical functionality, through understanding the envelope of TAR performance.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_I | Pages 74 - 74
1 Jan 2011
Richards L Bladen C Fisher J Ingham E Tipper J
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Introduction: Nanometre sized UHMWPE particles have recently been isolated from periprosthetic tissues and hip simulator lubricants [1,2]. The biological response to UHMWPE particles of 0.1 μm and above has been well characterised, with particles in the 0.1–1.0 μm size range having the highest biological activity [3]. The purpose of the study was to determine the biological activity of nanometre-sized particles in terms of osteolytic cytokine release from primary human monocytes.

Methods: Monocytes were isolated from peripheral blood from 5 healthy donors by density gradient centrifugation over Lymphoprep. Cells were cultured using the agarose gel technique [3] at particle volume (μm3):cell number ratios of 10:1 and 100:1. The particles used were:

1 Polystyrene FITC-conjugated FluoSpheres (FS; Invitrogen) in 20 nm, 40 nm, 0.2 μm and 1.0 μm sizes.

2a Complete Ceridust® 3615 (CD), a low MW polyethylene powder (size range 15 nm – 53 μm).

2b Nanometresized Ceridust® (fractionated by filtration using 10, 1, 0.1, 0.05 & 0.015 μm filters).

3 Clinically relevant GUR 1120 UHMWPE debris produced aseptically using a multidirectional wear rig.

All particles were tested for the presence of endotoxin prior to culture with cells. Cells without particles were used as a negative control and 200 ng/ml LPS was used as a positive control. Cell viability was assessed using the ATP Lite assay (Perkin Elmer) and ELISA was used to determine TNF-alpha, IL-1beta, IL-6 and IL-8 release at 3, 6, 12 and 24 h.

Results: FluoSpheres and CD had no effect on cell viability at 10 or 100:1. Clinically relevant UHMWPE particles had no effect on cell viability at 10:1, however, at 100:1 significant differences (P< 0.05) were seen at 3, 12 and 24 h for Donors 1 and 3. The 40 nm, 0.2μm and 1.0 μm FS caused significant elevation of TNF-α release at the 12 and 24 h time points at 100:1. There was no significant increase in TNF-α release for the 20 nm FS (3/5 donors). Particle volume and particle size showed correlation with cellular response, with the 20 nm FS showing the lowest biological activity. Clinically relevant UHMWPE particles and nanometre sized CD produced significantly higher quantities of TNF-alpha at 100:1. Release of interleukins IL-1beta, IL-6 and IL-8 followed a similar trend to TNF-alpha release.

Discussion: This study found that all nanometre-sized particles had the potential to provoke inflammatory cytokine release from macrophages. Particle volume and particle size played critical roles in initiating cellular responses. There was a lower particle size limit, with the 20 nm FS showing the lowest activity. Nanometre-sized polyethylene particles (CD) caused elevated TNF-α release, and since it has been shown that nanometre-sized UHMWPE particles are produced in large numbers in vivo [2], the relative contribution of these particles to osteolysis should be considered. The biological response to nanometre-sized clinically relevant UHMWPE particles is currently under investigation.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_III | Pages 479 - 479
1 Jul 2010
Richards L Cumbo M
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The Specialist Sarcoma Physiotherapist aims to ensure that patients with sarcoma receive a coordinated and seamless rehabilitation programme, when and where they need it, to enable them to achieve maximum function and quality of life. The National Institute of Clinical Excellence (NICE) Sarcoma guidelines (NICE 2006), recommend that all patients should have their care supervised by, or in conjunction with a sarcoma Multidisciplinary team (MDT). The role of the specialised physiotherapist on the MDT enables rehabilitation to be provided in a timely and coordinated way (NICE 2006).

Sarcoma and its treatment can have a major effect on the quality of patients’ lives. Treatment often involves extensive surgery, coupled with chemotherapy and/or radiotherapy. Rehabilitation of patients with sarcoma is highly specialised. A Specialist Sarcoma Physiotherapy team was set up at The Christie and Manchester Royal Infirmary in 1998. All patients who need it, can access expert rehabilitation and advice. The physiotherapist is a core member of the MDT, attends clinics, MDT meetings and offers seamless rehabilitation to in-patients and out-patients undergoing treatment (surgery, radiotherapy and chemotherapy) for bone or soft tissue sarcoma.

The physiotherapist must have an in-depth understanding of all aspects of sarcoma: treatment modalities, functional and psycho-social issues, and impact of disease progression, etc. Rehabilitation is often intensive and may take months and sometimes years. The physiotherapist will spend many hours with the patient and develops a close relationship where practical as well as emotional advice and counselling become part of the treatment. In the event of metastatic disease, the physiotherapist continues to offer support and helps to maximize independence and function even in the end stages of the disease. Access to specialist advice and rehabilitation helps the patient maximise the benefits of treatment, and aims to improve physical, social and emotional outcomes both during and following treatment.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 8 | Pages 1106 - 1113
1 Aug 2008
Richards L Brown C Stone MH Fisher J Ingham E Tipper JL

Nanometre-sized particles of ultra-high molecular weight polyethylene have been identified in the lubricants retrieved from hip simulators. Tissue samples were taken from seven failed Charnley total hip replacements, digested using strong alkali and analysed using high-resolution field emission gun-scanning electron microscopy to determine whether nanometre-sized particles of polyethylene debris were generated in vivo. A randomised method of analysis was used to quantify and characterise all the polyethylene particles isolated.

We isolated nanometre-sized particles from the retrieved tissue samples. The smallest identified was 30 nm and the majority were in the 0.1 μm to 0.99 μm size range. Particles in the 1.0 μm to 9.99 μm size range represented the highest proportion of the wear volume of the tissue samples, with 35% to 98% of the total wear volume comprised of particles of this size. The number of nanometre-sized particles isolated from the tissues accounted for only a small proportion of the total wear volume. Further work is required to assess the biological response to nanometre-sized polyethylene particles.