27 results found
Clarke SG, Logishetty K, Halewood C, et al., 2023, Low dose CT-based spatial analysis (CTSA) to measure implant migration after ceramic hip resurfacing arthroplasty (HRA): A phantom study., Proc Inst Mech Eng H
Implant migration is a predictor of arthroplasty survivorship. It is crucial to monitor the migration of novel hip prostheses within premarket clinical investigations. RSA is the gold standard method, but requires calibrated radiographs using specialised equipment. A commercial computed tomography micromotion analysis solution is a promising alternative but is not yet available for use with monobloc ceramic implants. This study aimed to develop and validate a CT-based spatial analysis (CTSA) method for use with ceramic implants. A phantom study was undertaken to assess accuracy and precision. A ceramic hip resurfacing arthroplasty (HRA) and 20 tantalum beads were implanted into a synthetic hip model and mounted onto a 6-degree of freedom motion stage. The hip was repeatedly scanned with a low dose CT protocol, with imposed micromovements. Data were interrogated using a semiautomated technique. The effective radiation dose for each scan was estimated to be 0.25 mSv. For the head implant, precision ranged between 0.11 and 0.28 mm for translations and 0.34°-0.42° for rotations. For the cup implant, precision ranged between 0.08 and 0.11 mm and 0.19° and 0.42°. For the head, accuracy ranged between 0.04 and 0.18 mm for translations and 0.28°-0.46° for rotations. For the cup, accuracy ranged between 0.04 and 0.08 mm and 0.17° and 0.43°. This in vitro study demonstrates that low dose CTSA of a ceramic HRA is similar in accuracy to RSA. CT is ubiquitous, and this method may be an alternative to RSA to measure prosthesis migration.
Jones G, Clarke S, Harris S, et al., 2019, A novel patient-specific instrument design can deliver robotic level accuracy in unicompartmental knee arthroplasty, The Knee, Vol: 26, Pages: 1421-1428, ISSN: 0968-0160
BackgroundA previous randomised controlled trial (RCT) by our group found that robotic assisted unicompartmental knee arthroplasty (UKA) surgery was significantly more accurate than conventional instrumentation. The aim of this study was to determine whether a low-cost novel PSI design could deliver the same level of accuracy as the robot in the same time efficient manner as conventional instruments.MethodsThirty patients undergoing medial UKA took part. Tibial component position was planned using a low dose CT-scan, and compared to a day 1 postoperative CT-scan to determine the difference between the planned and achieved positions. Operations were performed by one expert surgeon using PSI (Embody, London, UK).ResultsThe mean absolute difference between planned and achieved tibial implant positions using PSI was 2.0° (SD 1.0°) in the coronal plane, 1.8° (SD 1.5) in the sagittal plane, and 4.5° (SD 3.3) in the axial plane. These results were not significantly different to the 13 historical robotic cases (mean difference 0.5°, 0.5°, and 1.7°, p = 0.1907, 0.2867 and 0.1049 respectively). PSI mean operating time was on average 62 min shorter than the robotic group (p < 0.0001) and 40 min shorter than the conventional instrument group (p < 0.0001). No complications were reported.ConclusionsIn conclusion, this clinical trial demonstrates that for tibial component positioning in UKA, a novel design PSI guide in the hands of an expert surgeon, can safely deliver comparable accuracy to a robotic system, whilst being significantly faster than conventional instruments.NIHR Clinical Research Network Reference: 16100.
Uemura K, Boughton O, Logishetty K, et al., 2019, A single-use, size-specific, nylon arthroplasty guide: a preliminary study, Hip International, ISSN: 1120-7000
Jones GG, Clarke S, Jaere M, et al., 2019, Prothèse unicompartimentaire et désostéotomie pour échec d’ostéotomie tibiale : une alternative chirurgicale à l’arthroplastie totale de genouFailed high tibial osteotomy: A joint preserving alternative to total knee arthroplasty, Revue de Chirurgie Orthopedique et Traumatologique, Vol: 105, Pages: 41-41, ISSN: 1877-0517
High tibial osteotomy is an attractive treatment option for young active patients wishing to return to high level activities. However, it is not considered a long-term solution, with 30% revised at ten years. Currently, the only revision option is a total knee arthroplasty, a procedure that might not deliver the functional level expected by these highly active patients. This paper describes a novel joint preserving approach to HTO revision, using assistive technology, in the form of 3D printed guides, to reverse the osteotomy and simultaneously perform a unicompartmental knee replacement. The indications and planning aims for this procedure are discussed, and the preliminary results in four patients presented. Level of evidence: IV.
Jones GG, Clarke S, Jaere M, et al., 2019, Failed high tibial osteotomy: A joint preserving alternative to total knee arthroplasty, Orthopaedics and Traumatology: Surgery and Research, Vol: 105, Pages: 85-88, ISSN: 1877-0568
High tibial osteotomy is an attractive treatment option for young active patients wishing to return to high-level activities. However, it is not considered a long-term solution, with 30% revised at ten years. Currently, the only revision option is a total knee arthroplasty, a procedure that might not deliver the functional level expected by these highly active patients. This paper describes a novel joint preserving approach to HTO revision, using assistive technology, in the form of 3D printed guides, to reverse the osteotomy and simultaneously perform a unicompartmental knee replacement. The indications and planning aims for this procedure are discussed, and the preliminary results in four patients presented.
Jones GG, Logishetty K, Clarke S, et al., 2018, Do patient-specific instruments (PSI) for UKA allow non-expert surgeons to achieve the same saw cut accuracy as expert surgeons?, Archives of Orthopaedic and Trauma Surgery, Vol: 138, Pages: 1601-1608, ISSN: 0936-8051
INTRODUCTION: High-volume unicompartmental knee arthroplasty (UKA) surgeons have lower revision rates, in part due to improved intra-operative component alignment. This study set out to determine whether PSI might allow non-expert surgeons to achieve the same level of accuracy as expert surgeons. MATERIALS AND METHODS: Thirty-four surgical trainees with no prior experience of UKA, and four high-volume UKA surgeons were asked to perform the tibial saw cuts for a medial UKA in a sawbone model using both conventional and patient-specific instrumentation (PSI) with the aim of achieving a specified pre-operative plan. Half the participants in each group started with conventional instrumentation, and half with PSI. CT scans of the 76 cut sawbones were then segmented and reliably orientated in space, before saw cut position in the sagittal, coronal and axial planes was measured, and compared to the pre-operative plan. RESULTS: The compound error (absolute error in the coronal, sagittal and axial planes combined) for experts using conventional instruments was significantly less than that of the trainees (11.6°±4.0° v 7.7° ±2.3º, p = 0.029). PSI improved trainee accuracy to the same level as experts using conventional instruments (compound error 5.5° ±3.4º v 7.7° ±2.3º, p = 0.396) and patient-specific instruments (compound error 5.5° ±3.4º v 7.3° ±4.1º, p = 0.3). PSI did not improve the accuracy of high-volume surgeons (p = 0.3). CONCLUSIONS: In a sawbone model, PSI allowed inexperienced surgeons to achieve more accurate saw cuts, equivalent to expert surgeons, and thus has the potential to reduce revision rates. The next test will be to determine whether these results can be replicated in a clinical trial.
Jones G, Jaere M, Clarke S, et al., 2018, A Clinical Trial Examining the Accuracy of High Tibial Osteotomy When Performed by Experts Using a Novel Patient Specific Instrument (PSI), SSRN
Jones GG, Jaere M, Clarke S, et al., 2018, 3D printing and high tibial osteotomy, EFORT Open Reviews, Vol: 3, Pages: 254-259, ISSN: 2058-5241
High tibial osteotomy (HTO) is a relatively conservative surgical option in the management of medial knee pain. Thus far, the outcomes have been variable, and apparently worse than the arthroplasty alternatives when judged using conventional metrics, owing in large part to uncer-tainty around the extent of the correction planned and achieved.This review paper introduces the concept of detailed 3D planning of the procedure, and describes the 3D printing technology that enables the plan to be performed.The different ways that the osteotomy can be undertaken, and the varying guide designs that enable accurate regis-tration are discussed and described. The system accuracy is reported.In keeping with other assistive technologies, 3D printing enables the surgeon to achieve a preoperative plan with a degree of accuracy that is not possible using conventional instruments. With the advent of low dose CT, it has been possible to confirm that the procedure has been under-taken accurately too.HTO is the ‘ultimate’ personal intervention: the amount of correction needed for optimal offloading is not yet com-pletely understood.For the athletic person with early medial joint line over-load who still runs and enjoys life, HTO using 3D printing is an attractive option. The clinical effectiveness remains unproven.
Jones GG, Clarke S, Jaere M, et al., 2018, 3D printing and unicompartmental knee arthroplasty, EFORT Open Reviews, Vol: 3, Pages: 248-253, ISSN: 2058-5241
In suitable patients, unicompartmental knee arthroplasty (UKA) offers a number of advantages compared with total knee arthroplasty. However, the procedure is technically demanding, with a small tolerance for error. Assistive technology has the potential to improve the accuracy of implant positioning. This review paper describes the concept of detailed UKA planning in 3D, and the 3D printing technology that enables a plan to be delivered intraoperatively using patient-specific instrumentation (PSI). The varying guide designs that enable accurate registration are discussed and described. The system accuracy is reported. Future studies need to ascertain whether accuracy for low-volume surgeons can be delivered in the operating theatre using PSI, and reflected in improved patient reported outcome measures, and lower revision rates.
Clarke S, Cobb J, Jaere M, et al., 2018, Osteotomies: Advanced and complex techniques, ESSKA Instructional Course Lecture Book: Glasgow 2018, Pages: 129-151, ISBN: 9783662561263
We started performing precise surgery based upon CT plans in the last century - the first embodiment of this approach was a robotic assistant built for total knee replacement, the “Acrobot” . Abundant evidence now exists to confirm that assistive technologies enable surgeons to achieve their preoperative goals . The concept of planned surgery is therefore not novel. Patient-matched instruments share several key elements with the robotic platform, and these formed the basis of this current project. The essential elements include image segmentation, planning, and registration. We applied the know-how of these dimensions to design and build patient-matched guides for a range of tasks using biocompatible polymer 3D printers. Having established a workflow for arthroplasty, the adaptation of the same principles to osteotomy was a short step, requiring software to be developed to deliver semiautomated useful information regarding limb segment alignment and the shapes of bones.
Li J, Clarke S, Cobb JP, et al., 2017, Novel curved surface preparation technique for knee resurfacing, Medical Engineering and Physics, Vol: 49, Pages: 89-93, ISSN: 1350-4533
Conventional tools are incapable of preparing the curved articular surface geometry required during cartilage repair procedures. A novel curved surface preparation technique was proposed and tested to provide an accurate low-cost solution. Three shapes of samples, with flat, 30 mm radius and 60 mm radius surfaces, were manufactured from foam bone substitute for testing. Registering guides and cutting guides were designed and 3-D printed to fit onto the foam samples. A rotational cutting tool with an adapter was used to prepare the surfaces following the guidance slots in the cutting guides. The accuracies of the positions and shapes of the prepared cavities were measured using a digital calliper, and the surface depth accuracy was measured using a 3-D scanner. The mean shape and position errors were both approximately ± 0.5 mm and the mean surface depth error ranged from 0 to 0.3 mm, range − 0.3 to + 0.45 mm 95% CI. This study showed that the technique was able to prepare a curved surface accurately; with some modification it can be used to prepare the knee surface for cartilage repair.
Ng CTJ, Newman S, Harris S, et al., 2017, Patient-specific instrumentation improves alignment of lateral unicompartmental knee replacements by novice surgeons., International Orthopaedics, Vol: 41, Pages: 1379-1385, ISSN: 0341-2695
PurposePatient-specific instrumentation (PSI) has the potential to offer numerous benefits—not least of all, improved resection accuracy; but its potential has not been realised in clinical studies. An explanation may be the focus of such studies on the total knee replacement (TKR—a common procedure, with which surgeons are generally very familiar. Consequently, we sought to investigate the potential role of PSI in guiding novice surgeons to perform the more technically demanding and less familiar lateral unicondylar knee replacement (LUKR).MethodsTwelve orthopaedic trainees naive to LUKR were instructed to perform the procedure according to a pre-operative plan. These were carried out on synthetic sawbones and were completed once with conventional instrumentation alone and once with the adjunct of PSI, allowing a comparison of the plan adherence achieved by the two sets of instrumentation.ResultsThere was a tendency for PSI to demonstrate improved plan adherence, though a statistically significant improvement was only seen in compound rotational error of the femoral implant (p = 0.004). PSI was, however, able to produce narrower standard deviations in the mean translational displacement of the femoral implant and also the mean rotational displacement of both implants, suggesting a higher degree of precision.ConclusionsOur study provides some evidence that PSI can improve the ability of novice surgeons to replicate a pre-operative plan, but our results suggest the need for larger-scale clinical studies to establish the role of PSI in this procedure.
Aqil A, Wiik A, Clarke S, et al., 2015, Resurfacing head size and femoral fracture: Are registry conclusions on head size justified?, Eur J Orthop Surg Traumatol, Vol: 25, Pages: 1301-1305
BACKGROUND: Joint registries report that peri-prosthetic fractures are the most common reason for early revision of a hip resurfacing arthroplasty (HRA) and are twice as likely with small implant sizes. However, a national survey found peri-prosthetic fracture to be strongly associated with surgical accuracy. We therefore asked whether the force required to induce a peri-prosthetic fracture: (1) was significantly lower when using smaller implants and (2) correlated to the size of implant used, when surgery was performed accurately. METHODS: To ensure an adequate power, we calculated our sample size from pilot data. Forty-four femurs were tested in two experiments. The first experiment tested femurs with either a small (48 mm) or a large (54 mm) HRA implant. The second involved testing femurs with a range of implant sizes. A rapid prototyped femur-specific guide ensured accurate implantation. Specimens were then vertically loaded in a servo-hydraulic testing machine till fracture. Displacement (mm) and force (N) required for fracture were recorded. RESULTS: A median force of 1081 N was required to fracture specimens implanted with small 48-mm heads, while 1134 N was required when a 54-mm head was used (U = 77, z = -0.054, p = 0.957). Implant head size and force required to fracture were not related, r = 0.12, p = 0.63. CONCLUSIONS: The force required to induce a resurfacing peri-prosthetic fracture was not related to the size of the implant. The increased failure rate seen in all registries is unlikely to be directly the result of this single variable. Correctly performed resurfacing arthroplasty is highly resistant to fracture.
Jones C, Aqil A, Clarke S, et al., 2015, Short uncemented stems allow greater femoral flexibility and may reduce peri-prosthetic fracture risk: a dry bone and cadaveric study, Journal of Orthopaedics and Traumatology, Vol: 16, Pages: 229-235, ISSN: 1590-9921
BackgroundShort femoral stems for uncemented total hip arthroplasty have been introduced as a safe alternative to traditional longer stem designs. However, there has been little biomechanical examination of the effects of stem length on complications of surgery. This study aims to examine the effect of femoral stem length on torsional resistance to peri-prosthetic fracture.Materials and methodsWe tested 16 synthetic and two paired cadaveric femora. Specimens were implanted and then rapidly rotated until fracture to simulate internal rotation on a planted foot, as might occur during stumbling. 3D planning software and custom-printed 3D cutting guides were used to enhance the accuracy and consistency of our stem insertion technique.ResultsSynthetic femora implanted with short stems fractured at a significantly higher torque (27.1 vs. 24.2 Nm, p = 0.03) and angle (30.3° vs. 22.3°, p = 0.002) than those implanted with long stems. Fracture patterns of the two groups were different, but showed remarkable consistency within each group. These characteristic fracture patterns were closely replicated in the pair of cadaveric femora.ConclusionsThis new short-stemmed press-fit femoral component allows more femoral flexibility and confers a higher resistance to peri-prosthetic fracture from torsional forces than long stems.
Jaffry Z, Masjedi M, Clarke S, et al., 2013, Unicompartmental knee arthroplasties: Robot vs. patient specific instrumentation, The Knee
Clarke SG, Phillips ATM, Bull AMJ, et al., 2012, A hierarchy of computationally derived surgical and patient influences on metal on metal press-fit acetabular cup failure, Journal of Biomechanics, Vol: 45, Pages: 1698-1704
Clarke SG, Phillips ATM, Cobb JP, 2012, The Locality of Female Morphological Acetabular Disorders, Orthopaedic Research Society Annual Meeting
Clarke SG, Phillips ATM, Bull AMJ, 2012, Validation of FE micromotions and strains around a press-fit cup: introducting a new micromotion technique, Annals of Biomedical Engineering, Vol: 40, Pages: 1586-1596
Clarke SG, Phillips ATM, Bull AMJ, 2011, Evaluating a suitable level of model complexity for finite element analysis of the intact acetabulum, Computational Methods in Biomechanics and Biomedical Engineering
Clarke SG, 2011, Factors Influencing Press-fit Acetabular Cup Failure: an Experimentally Validated Finite Element Study, PhD Thesis
Clarke SG, Phillips ATM, 2011, Multi-factorial FE Analysis of Metal on Metal Acetabular Cup Failure, British Orthopaedic Research Society Annual Meeting
Clarke SG, Phillips ATM, Bull AMJ, 2011, Surgical and Patient Influences on Metal on Metal Press-fit Acetabular Cup Failure: a Computational Finite Element Study, Engineers and Surgeons: Joined at the Hip III
Clarke SG, Hart AJ, Phillips ATM, 2010, The Effect of Acetabular Inclination on Metal on Metal Wear: a Computational Study Including Daily Activity Loading, British Hip Society Annual Meeting
Clarke SG, Phillips ATM, Bull ATM, 2009, The Response of the Acetabulum During Loading, XXII Congress of the International Society of Biomechanics
Clarke SG, Phillips ATM, 2009, A Priori Sensitivity Studies for FEA of an Acetabular Cup, Bath Biomechanics Symposium
Clarke SG, Phillips ATM, 2008, Statistical Analysis of Pelvic Geometry; and Assessment of Numerical Modelling Assumptions, Computer Methods in Biomechanics and Biomedical Engineering
Clarke SG, Phillips ATM, 2008, Statistical Analysis of Pelvis Geometry, British Orthopaedic Research Society Annual Meeting
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