27 research outputs found
Highly Crosslinked Polyethylene Liners Have Negligible Wear at 10 Years: A Radiostereometric Analysis Study.
No full textBackground: The introduction of crosslinked ultra-high molecular weight polyethylene (XLPE) acetabular liners has been very successful, with decreased wear and reduction in the rates of revision hip arthroplasties. XLPE is the preferred articulation for most surgeons; however, there are concerns about the long-term performance of XLPE liners created with different manufacturing processes, which may lead to time-dependent failure, including accelerated wear, after several years. Questions/purposes: (1) What is the amount and rate of wear during the first 10 years using radiostereometric analysis (RSA) measurements of patients who had THAs that included a second-generation XLPE bearing? (2) Does the rate of wear change after 5 years in situ? Methods: This is a brief follow-up of a previous RSA study. In that study, we prospectively enrolled 21 patients with osteoarthritis who underwent primary cementless THA with an XLPE acetabular liner (three cycles of 3Mrad annealed) and 32-mm articulation. That group represented 44% of the 48 THAs performed by the surgeon at the hospital where RSA was available; 16 had cemented hips, leaving 32 who were invited to participate in this study. Of those, 11 lived rurally and declined to participate, leaving 21 patients who were included in the initial study. Since then, three patients died, one developed dementia and could not participate, and one had revision THA for reasons other than wear, leaving 16 patients available for analysis at 10 years. Tantalum markers were inserted during surgery, and all patients had RSA radiographs taken at 1 week, 6 months, and 1, 2, 5, and 10 years postoperatively. Femoral head penetration into the acetabular component was measured with RSA, including bedding-in during the first year and annual wear thereafter. Results The median medial, proximal, anterior, two-dimensional (2D), and three-dimensional (3D) wear rates between 1 and 10 years were -0.001, 0.004, -0.012, 0.000, and 0.002 mm/year, respectively. No patient in this cohort had a proximal or 2D wear rate greater than 0.025 mm/year. The median proximal wear rate between 5 and 10 years (0.002 mm/year) was not greater than wear at 1 to 5 years (0.004 mm/year). Conclusion: Femoral head penetration in this second-generation XLPE liner remained very low at 10 years and accelerated wear after 5 years in situ did not occur. Concerns about late-onset wear from oxidation of irradiated-annealed XLPE were not observed. The low level of wear remains encouraging for the future clinical performance of this material. Level of Evidence Level II, therapeutic study.David G. Campbell, Stuart A. Callary
Biomechanical methods for the assessment of fracture repair
No full textThe progress of fracture healing is directly related to an increasing stiffness and strength of the healing fracture. Similarly the weight bearing capacity of a bone directly relates to the mechanical stability of the fracture. Therefore, assessing the progress of fracture repair can be based on the measurement of the mechanical stability of the healing fracture. However, fracture stability is difficult to assess directly due to various obstacles of which shielding of the mechanical properties by the fracture fixation construct is the most relevant one. Several assessment methods have been proposed to overcome these obstacles and to obtain some sort of mechanical surrogate describing the stability of the fracture. The most direct method is the measurement of the flexibility of a fracture under a given external load, which comprises the challenge of accurately measuring the deformation of the bone. Alternative approaches include the measurement of load share between implant and bone by internal or by external sensors. A direct 3 dimensional measurement of bone displacement is provided by radiostereometric analysis which can assess fracture migration and can detect fracture movement under load. More indirect mechanical methods induce cyclic perturbations within the bone and measure the response as a function of healing time. At lower frequencies the perturbations are induced in the form of vibration and at higher frequencies in the form of ultrasonic waves. Both methods provide surrogates for the mechanical properties at the fracture site. Although biomechanical properties of a healing fracture provide a direct and clinically relevant measure for fracture healing, their application will in the near future be limited to clinical studies or research settings.P. Augat, M. Faschingbauer, K. Seide, K. Tobita, S.A. Callary, L.B. Solomon, J.H. Holstei
Screw Placement Influence on Implant Stability and Osseointegration Potential in Revision Hip Arthroplasty Involving Acetabular Defects: A Cohort-Based Modeling Study
No full textAchieving acetabular cup stability following revision total hip arthroplasty (rTHA) involving acetabular defects is challenging. Current computational modeling approaches to investigate implant stability under physiological loading are time consuming to implement and, to date, have been based on low sample sizes across limited defect classifications. This study had two aims. First, to develop an automated rTHA simulation framework to estimate postoperative implant response to physiological loading across the range of Paprosky acetabular defects; and second, to use this framework to estimate regional implant stability and osseointegration potential of rTHA implants augmented with four different screw configurations: (i) superior fixation only (ii) superior and infero‐posterior fixation (iii) superior and infero‐anterior fixation, and (iv) superior, infero‐posterior, and infero‐anterior fixation. A modeling pipeline employing artificial neural networks and statistical shape modeling was developed to convert patient computed tomography (CT) images to finite element models for automated surgical planning and simulation of rTHA involving acetabular defects. Computed tomography images from sixty subjects were used as input to the framework resulting in 214 completed simulations. An infero‐posterior screw when used with a superior screw was associated with a significant reduction in posterior acetabular micromotion compared to using a superior screw alone (mean reduction: 129 μm, p < 0.001). Use of an infero‐posterior screw improved overall implant stability more than that of an infero‐anterior screw. The results suggest that screw holes allowing inferior fixation ought to be made standard in revision acetabular components. The findings of this study may be useful in surgical planning for rTHA.Daniel Hopkins, Stuart A. Callary, L. Bogdan Solomon, Peter V. S. Lee, David C. Acklan
Highly porous tantalum acetabular components without ancillary screws have similar migration to porous titanium acetabular components with screws at 2 years: a randomized controlled trial
No full textBackground: It is proposed that highly porous coatings on acetabular components, such as a porous tantalum coating, provide adequate fixation without ancillary screw fixation in primary total hip arthroplasty (THA). However, tantalum acetabular components have been associated with higher rates of revision than other uncemented components in national registries. The aim of this randomized controlled trial is to determine whether the early migration of a solid-backed tantalum acetabular component was no greater than that of a titanium acetabular component with ancillary screw fixation that has proven good clinical results. Methods: Sixty-six patients aged 40 to 64 years, with osteoarthritis and Charnley grade A or B activity grade and who underwent primary THA, were recruited into the trial. Patients were randomized intraoperatively to receive either the tantalum or titanium acetabular component. All patients received the same cemented polished tapered femoral stem, 28-mm cobalt-chromium femoral head, and highly cross-linked polyethylene liner. Acetabular component migration was measured using radiostereometric analysis at 4-6 days postoperatively and at 6 weeks, 3 months, 1 and 2 years following THA. Results: The mean proximal migration at 2 years for the tantalum cohort was 0.17 mm (95% confidence interval, 0.09-0.24) which was no greater than that of the titanium cohort which was 0.19 mm (0.07-0.32). Harris hip scores and functional activity scores were similar between groups. Conclusion: These results demonstrate that early stability can be achieved without ancillary screw fixation through the use of a highly porous high friction coating on a solid-backed modular acetabular component. Level of Evidence: Level I.Donald W. Howie, Oksana T. Holubowycz, Stuart A. Callary, Thomas S. Robertson, Lucian B. Solomo
Ex vivo assessment of surgically repaired tibial plateau fracture displacement under axial load using large-volume micro-CT
No full textPostoperative weight bearing has the potential to generate fragmental motion of surgically repaired tibial plateau fractures (TPFs), which may contribute to loss of fracture reduction. The effect of loading on the internal distribution of fragmentary displacements is currently unknown. The aim of this study was to determine the internal displacements of surgically repaired split TPFs due to a three-bodyweight load, using large-volume micro-CT imaging and image correlation. Fractures were generated and surgically repaired for two cadaveric specimens. Load was applied to the specimens inside a large-volume micro-CT system and scanned at 0.046 mm isotropic voxel size. Pre- and post-loading images were paired, co-registered, and internal fragmentary displacements quantified. Internal fragmental displacements of the cadaveric bones were compared to in vivo displacements measured in the lateral split fragments of TPFs in a clinical cohort of patients who had similar surgical repair and were prescribed pain tolerated postoperative weight bearing. The split fragments of cadaveric specimens displaced, on average, less than 0.3 mm, consistent with in vivo measurements. Specimen one rotated around the mediolateral axis, while specimen two displaced consistently caudally. Specimen two also had varying displacements along the mediolateral axis where, at the fracture site, the fragment displaced caudally and laterally, while the most lateral edge of the tibial plateau displaced caudally and medially. The methods applied in this study can be used to measure internal fragmental motion within TPFs.Kieran J. Bennett, Stuart A. Callary, Gerald J. Atkins, Saulo Martelli, Egon Perilli, L. Bogdan Solomon, Dominic Thewli
Differentially loaded radiostereometric analysis (DLRSA) in torsion adds essential information in diaphyseal bone healing: the example of a tibial osteotomy
No full textBACKGROUND: Clinical assessment and conventional imaging, which are currently used to monitor fracture healing, do not provide information on the mechanical properties of the healing construct. This limits their use in patient management decisions. Differentially loaded radiostereometric analysis (DLRSA) is a technique developed to assess the mechanical properties of healing fractures in vivo. DLRSA measures the relative micromotion of tantalum beads inserted into bone fracture fragments in response to load across the fracture site. To date, these loads have been applied axially, although in fractures fixed with devices which are highly resistant to axial loads, such as locked intramedullary nails, torsional testing may be more sensitive to healing. The aim of this study was to establish a method to investigate DLRSA using torsional loading for clinical application. METHODS: A device was designed and built to apply torsional loads to the tibia. The test case was an oblique plain corrective osteotomy of a tibial diaphysis stabilized with an intramedullary nail and with tantalum beads inserted into the two adjacent bone segments. Post surgical examinations were made at 2 weeks, 2, 4, and 6 months as well as 1 and 2 years. Healing was monitored with the use of plain film radiographs, computed tomography (CT) and DLRSA. Axial loads of 30kg and an external torsion of 5Nm were applied during DLRSA examinations and the resultant displacement and stiffness were calculated. RESULTS: Torsional DLRSA demonstrated progressive changes in angular displacements and torsional stiffness consistent with the fracture healing observed by CT. By contrast, axial DLRSA was not informative and was more reflective of the stability of the fixation than healing bone. CONCLUSION: The addition of torsional assessments to DLRSA provides an important investigative option in assessing the biomechanical properties of bone healing in vivo.M.J. Chehade, I.A. Vakaci, S.A. Callary, D.M. Findlay and L.B. Solomo
Corroboration of coupled musculoskeletal model and finite element predictions with in‐vivo RSA migration of an uncemented acetabular component
No full textFirst published: 01 August 2023While finite element (FE) models have been used extensively in orthopedic studies, validation of their outcome metrics has been limited to comparison against ex vivo testing. The aim of this study was to validate FE model predictions of the initial cup mechanical environment against patient‐matched in vivo measurements of acetabular cup migration using radiostereometric analysis (RSA). Tailored musculoskeletal and FE models were developed using a combination of three‐dimensional (3D) motion capture data and clinical computerized tomography (CT) scans for a cohort of eight individuals who underwent primary total hip replacement and were prospectively enrolled in an RSA study. FE models were developed to calculate the mean modulus of cancellous bone, composite peak micromotion (CPM), composite peak strain (CPS) and percentage area of bone ingrowth. The RSA cup migration at 3 months was used to corroborate the FE output metrics. Qualitatively, all FEpredicted metrics followed a similar rank order as the in vivo RSA 3D migration data. The two cases with the lowest predicted CPM (917 MPa) were confirmed to have the lowest in vivo RSA 3D migration (80 μm), larger CPS (>0.0119) and lowest bone modulus (0.78 mm). This study enabled the first corroboration between tailored musculoskeletal and FE model predictions with in vivo RSA cup migration. Investigation of additional patient‐matched CT, gait, and RSA examinations may allow further development and validation of FE models.Khosro Fallahnezhad, Stuart A. Callary, Dermot O'Rourke, Jasvir S. Bahl, Dominic Thewlis, Lucian B. Solomon, Mark Taylo
The variation in hip stability measurements between supine and standing radiographs of dysplastic hips
No full textAIMS: The aims of this study were to compare clinically relevant measurements of hip dysplasia on radiographs taken in the supine and standing position, and to compare Hip2Norm software and Picture Archiving and Communication System (PACS)-derived digital radiological measurements. METHODS: Preoperative supine and standing radiographs of 36 consecutive patients (43 hips) who underwent periacetabular osteotomy surgery were retrospectively analyzed from a single-centre, two-surgeon cohort. Anterior coverage (AC), posterior coverage (PC), lateral centre-edge angle (LCEA), acetabular inclination (AI), sharp angle (SA), pelvic tilt (PT), retroversion index (RI), femoroepiphyseal acetabular roof (FEAR) index, femoroepiphyseal horizontal angle (FEHA), leg length discrepancy (LLD), and pelvic obliquity (PO) were analyzed using both Hip2Norm software and PACS-derived measurements where applicable. RESULTS: Analysis of supine and standing radiographs resulted in significant variation for measurements of PT (p < 0.001) and AC (p = 0.005). The variation in PT correlated with the variation in AC in a limited number of patients (R2 = 0.378; p = 0.012). CONCLUSION: The significant variation in PT and AC between supine and standing radiographs suggests that it may benefit surgeons to have both radiographs when planning surgical correction of hip dysplasia. We also recommend using PACS-derived measurements of AI and SA due to the poor interobserver error on Hip2Norm.Ameya Bhanushali, Mukai Chimutengwende-Gordon, Martin Beck, Stuart Adam Callary, Kerry Costi, Donald W. Howie, Lucian Bogdan Solomo
Computational modeling of revision total hip arthroplasty involving acetabular defects: A systematic review
No full textRevision total hip arthroplasty (rTHA) involving acetabular defects is a complex procedure associated with lower rates of success than primary THA. Computational modeling has played a key role in surgical planning and prediction of postoperative outcomes following primary THA, but modeling applications in rTHA for acetabular defects remain poorly understood. This study aimed to systematically review the use of computational modeling in acetabular defect classification, implant selection and placement, implant design, and postoperative joint functional performance evaluation following rTHA involving acetabular defects. The databases of Web of Science, Scopus, Medline, Embase, Global Health and Central were searched. Fifty‐three relevant articles met the inclusion criteria, and their quality were evaluated using a modified Downs and Black evaluation criteria framework. Manual image segmentation from computed tomography scans, which is time consuming, remains the primary method used to generate 3D models of hip bone; however, statistical shape models, once developed, can be used to estimate pre‐defect anatomy rapidly. Finite element modeling, which has been used to estimate bone stresses and strains, and implant micromotion postoperatively, has played a key role in custom and off‐the‐ shelf implant design, mitigation of stress shielding, and prediction of bone remodeling and implant stability. However, model validation is challenging and requires rigorous evaluation and comparison with respect to mid‐ to long‐term clinical outcomes. Development of fast, accurate methods to model acetabular defects, including statistical shape models and artificial neural networks, may ultimately improve uptake of and expand applications in modeling and simulation of rTHA for the research setting and clinic.Daniel Hopkins, Stuart A. Callary, L. B. Solomon, Sarah C. Woodford, Peter V. S. Lee, David C. Acklan
