Publications
14 results found
Puthumanapully PK, Browne M, 2016, The Influence of Coating Length on Osseointegration of Uncemented Implants: A Computational Study, The 2012 meeting of the Orthopaedic Research Society
Puthumanapully PK, Harris SJ, Leong A, et al., 2014, A morphometric study of normal and varus knees, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 22, Pages: 2891-2899, ISSN: 0942-2056
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- Citations: 26
Puthumanapully PK, Amis A, Harris S, et al., 2013, Measurements of the Varus Knee and Their Influence on Implant Design, Orthopaedic Proceedings, Publisher: The British Editorial Society of Bone & Joint Surgery, Pages: 89-89, ISSN: 1358-992X
Introduction:Varus alignment of the knee is common in patients undergoing unicondylar knee replacement. To measure the geometry and morphology of these knees is to know whether a single unicondylar knee implant design is suitable for all patients, i.e. for patients with varus deformity and those without. The aim of this study was to identify any significant differences between normal and varus knees that may influence unicondylar implant design for the latter group.Methodology:56 patients (31 varus, 25 normal) were evaluated through CT imaging. Images were segmented to create 3D models and aligned to a tri-spherical plane (centres of spheres fitted to the femoral head and the medial and lateral flexion facets). 30 key co-ordinates were recorded per specimen to define the important axes, angles and shapes (e.g. spheres to define flexion and extension facet surfaces) that describe the femoral condylar geometry using in-house software. The points were then projected in sagittal, coronal and transverse planes. Standardised distance and angular measurements were then carried out between the points and the differences between the morphology of normal and varus knee summarised. For the varus knee group, trends were investigated that could be related to the magnitude of varus deformity.Results:Several significant differences between normal and varus knees were found, but most of these were small differences unlikely to be clinically significant or have an influence on implant design. However, two strong trends were observed. Firstly, the version of the femoral neck was significantly less for patients with varus knees (mean difference 9°; p < 0.05).The second trend was a significant difference in the sagittal morphology of the medial condyle. The kink angle, the angle formed by the intersection of the circles fitted to the flexion and extension facet surfaces, and their centres (Figure 1) was either absent or small in normal knees (mean 1°). An absent kink angle o
Puthumanapully PK, Stewart M, Browne M, et al., 2013, Modular Junction Testing of Large Diameter Metal on Metal Hip Replacements: A Pilot Study, Orthopaedic Proceedings, Vol: 95-B, Pages: 288-288, ISSN: 1358-992X
IntroductionFatigue and wear at the head/stem modular junction of large diameter total hip replacements can be exacerbated as a result of the increase in frictional torque. In vivo, a ?toggling,? anterior-posterior (A-P) movement of the head taper on the trunnion may facilitate corrosion in the presence of physiological fluids, leading to increased metal ion release. Clinically, metal ion release has been linked to the formation of pseudo tumours and tissue necrosis [1].AimsIn this investigation, a large diameter metal on metal THR was tested on a rig designed to recreate the toggling motion at the head/stem junction. Post-test analyses are conducted to look for evidence of mechanical and corrosive damage.Methods and MaterialsA 58 mm diameter metal head (12/14 taper) was assembled onto a sectioned Freeman stem affixed to custom designed rig that enabled both, axial loads and a frictional torque (for the AP toggle load) about the rotation of the femoral head to be applied as shown in Figure 1. A linear variable differential transformer (LVDT), which had a minimum resolution of 0.5 microns, was positioned in contact with the neck directly under the modular head to track A-P movements at the junction. An axial load of 150N with toggle loads varying between 100 (± 50N) and 200N (± 50N) at 1 Hz were run on 4 taper assemblies, 2 dry and 2 wet (incorporating a physiological fluid at the junction) between 400,000 and 600,000 cycles. Movement at the junction was recorded, followed by visual inspection and RedLux? surface profile analysis of the taper and trunnion.Results and ConclusionThe LVDT could successfully record movement at the junction. Initially (?1000 cycles), the movement at the junction was found to be variable and between 5?10 microns, which can be attributed to the taper ?bedding-in? on to the trunnion. The movement was then found to steadily increase before stabilising. The dry tapers recorded motion ranging between 5?15 microns, and between 10?2
Puthumanapully PK, Shearwood-Porter N, Stewart M, et al., 2013, The Role of Surface Roughness, Temperature, Viscosity and Application Time of Bone Cement on the Mechanical Interlock With Implant Surfaces-a Parametric Study, Orthopaedic Proceedings, Vol: 95-B, Pages: 287-287, ISSN: 1358-992X
IntroductionImplant-cement debonding at the knee has been reported previously [1]. The strength of the mechanical interlock of bone cement on to an implant surface can be associated with both bone cement and implant related factors. In addition to implant surface profile, sub-optimal mixing temperatures and waiting times prior to cement application may weaken the strength of the interlock.AimsThe study aimed to investigate the influence of bone cement related factors such as mixing temperature, viscosity, and the mixing and waiting times prior to application, in combination with implant surface roughness, on the tensile strength at the interface.Materials and MethodsTensile tests were carried out on two types of hand-mixed cement, high (HV) and medium viscosity (MV), sandwiched between two cylindrical Cobalt-Chrome coupons with either smooth (60 grit) or rough (20 grit) surface finishes. 144 Specimens were prepared with a cement thickness layer of 2.5 mm in customised rigs (Figure 1). The samples were grouped and tested at two mixing temperatures (23 and 19 degrees), at different mixing times (HV-30s, MV-45s). Waiting times after mixing were varied between early (1.5 min), optimal (4.5 min) or late (8 min); for HV and 4 min, 7.5 min and 11 min for MV cements. All the samples were cured for 24 hours prior to testing. The peak force and stress was calculated for all specimens.Results and ConclusionSurface Finish: Rough surfaced samples had significantly higher (p < 0.05) mean tensile forces and stress than smooth samples at both 19 and 23 degrees across HV and MV cement types.Cement Type: MV cements, when applied to rough samples with waiting times of 4 minutes at 23 degrees, and 11 minutes at 19 degrees, resulted in the highest peak tensile forces, followed by 7.5 minutes at 23 and 19 degrees respectively (Figure 2).Temperature at different application times for rough and smooth samples: for MV cement, rough samples prepared at 23 degrees, 4 minutes, and smooth sa
Pal B, Puthumanapully PK, Amis AA, 2013, (ii) Biomechanics of implant fixation, Orthopaedics and Trauma, Vol: 27, Pages: 76-84, ISSN: 1877-1327
In joint replacement, stability of the implant is provided by a combination of the techniques adopted to fix the implant to the surrounding bone and the geometric features of the implant. Fixation techniques can either use cement or be cementless. Cemented fixation uses PMMA bone cement to grout the implant and bone together, while cementless fixation involves either a press-fit between the implant and bone, or specific design features that encourage bone growth into or onto the implant. Although both of these fixation techniques perform well in terms of longevity, each method functions better than the other in certain patient groups, and each has some positives and negatives. This article reports an overview of the fundamental aspects of the fixation techniques, their clinical advantages and disadvantages, associated clinical concerns and recent trends of fixation in clinical practice. This will be coupled with specific examples on how certain geometric features of an implant help in achieving initial and long-term stability and fixation. © 2013 Elsevier Ltd.
Puthumanapully PK, 2011, Simulation of tissue differentation in uncemented hip implants based on a mechanoregulatory hypothesis
Simulation of tissue differentiation in uncemented hip implants based on a mechanoregulatory hypothesis
Puthumanapully PK, Browne M, 2011, Tissue Differentiation around a Short Stemmed Metaphyseal Loading Implant Employing a Modified Mechanoregulatory Algorithm: A Finite Element Study, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 29, Pages: 787-794, ISSN: 0736-0266
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- Citations: 15
Puthumanapully PK, New A, Browne M, 2010, Design influences of a short-stemmed and long-stemmed uncemented implant on tissue differentiation at the interface: A computational study based on a mechanoregulatory hypothesis, The 9th international symposium of computer methods in biomechanics and biomedical engineering
Puthumanapully PK, New A, Browne M, 2009, Simulating bone ingrowth in porous coated implants, Exploring the biological/biomechanics interface
Puthumanapully PK, New A, Browne M, 2009, Do size and shape matter? Osseointegration in a short stemmed femoral prosthesis as predicted by a mechanoregulatory algorithm, The 22nd Annual Congress of International Society for Technology in Arthroplasty
Puthumanapully PK, New A, Browne M, 2009, Osseointegration of a short stemmed femoral prosthesis as predicted by a mechanoregulatory algorithm, The 55th annual meeting of the Orthopaedic Research Society
Puthumanapully PK, Browne M, 2009, Predicting bone ingrowth and tissue differentiation around a long stemmed porous coated hip implant using fracture healing principles, The 22nd Annual Congress of International Society for Technology in Arthroplasty
Puthumanapully PK, New A, Browne M, 2008, Do multi-layer beads on porous coated implants influence bone ingrowth? A finite element study, Journal of Biomechanics, ISSN: 1873-2380
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