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Bonnevialle N, Geais L, Müller JH, Berhouet J. Effect of RSA glenoid baseplate central fixation on micromotion and bone stress. JSES Int 2020; 4:979-986. [PMID: 33345244 PMCID: PMC7738598 DOI: 10.1016/j.jseint.2020.07.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Background In reverse shoulder arthroplasties (RSA), osseous in-growth is promoted if glenoid micromotion does not exceed 150 μm. The purpose of this study was to determine whether the configuration of central fixation for RSA glenoid baseplates reduces implant micromotion or changes scapula bone stresses. Methods Using finite element analysis, glenoid baseplate fixation was tested in a cohort of 3 male and 2 female patients who were to undergo RSA. Computer models were created for 3 different RSA glenoid baseplate and 84 glenosphere designs, a central threaded peg (1 variant, D-TP), a central unthreaded peg (2 variants, I- 85 P(15) and I-P(25)), and a central peg with a screw (2 variants, A-PS and I-PS). A compressive and shear force of 756 N was distributed across the glenosphere with the scapula anchored. Results Displacement was within 20-130 μm at the glenosphere baseplate-bone interface for all baseplates. The glenospheres with unthreaded pegs had intermediate displacement values (I-P(15): median, 89 μm; range, 32-112 μm; and I-P(25): median, 93 μm; range, 31-109 μm). The von Mises stresses were 1.8-7.0 MPa within cortical bone and 0.6-1.6 MPa within trabecular bone. Cortical bone stresses were similar with unthreaded pegs (I-P(15): median, 4.2 MPa; range, 1.8-6.0 MPa; and I-P(25): median, 4.2 MPa; range, 1.8-6.1 MPa), whereas mean trabecular stresses were similar for all configurations. Conclusions All configurations yielded adequate stability, with micromotions being below 150 μm. The unthreaded pegged designs provided a valid alternative to the stable threaded pegged convex baseplates in terms of micromotions and bone stresses.
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Affiliation(s)
| | | | | | | | - Julien Berhouet
- Faculté de Médecine de Tours, CHRU Trousseau Service d'Orthopédie Traumatologie, Université de Tours, Tours, France.,Laboratoire d'Informatique Fondamentale et Appliquée de Tours (EA6300), Ecole d'Ingénieurs Polytechnique Universitaire de Tours, Tours, France
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Reeves JM, Knowles NK, Athwal GS, Johnson JA. Methods for Post Hoc Quantitative Computed Tomography Bone Density Calibration: Phantom-Only and Regression. J Biomech Eng 2019; 140:2680998. [PMID: 29801170 DOI: 10.1115/1.4040122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Indexed: 11/08/2022]
Abstract
Quantitative computed tomography (qCT) relies on calibrated bone mineral density data. If a calibration phantom is absent from the CT scan, post hoc calibration becomes necessary. Scanning a calibration phantom after-the-fact and applying that calibration to uncalibrated scans has been used previously. Alternatively, the estimated density is known to vary with CT settings, suggesting that it may be possible to predict the calibration terms using CT settings. This study compares a novel CT setting regression method for post hoc calibration to standard and post hoc phantom-only calibrations. Five cadaveric upper limbs were scanned at 11 combinations of peak tube voltage and current (80-140 kV and 100-300 mA) with two calibration phantoms. Density calibrations were performed for the cadaver scans, and scans of the phantoms alone. Stepwise linear regression determined if the calibration equation terms were predictable using peak tube voltage and current. Peak tube voltage, but not current, was significantly correlated with regression calibration terms. Calibration equation slope was significantly related to the type of phantom (p < 0.001), calibration method (p = 0.026), and peak tube voltage (p < 0.001), but not current (p = 1.000). The calibration equation vertical intercept was significantly related to the type of phantom (p < 0.001), and peak tube voltage (p = 0.006), but not calibration method (p = 0.682), or current (p = 0.822). Accordingly, regression can correlate peak tube voltage with density calibration terms. Suggesting that, while standard qCT calibration is preferable, regression calibration may be an acceptable post hoc method when necessary.
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Affiliation(s)
- Jacob M Reeves
- Department of Mechanical Engineering, Western University Canada, 1151 Richmond Street, London, ON N6A3K7, Canada e-mail:
| | - Nikolas K Knowles
- Department of Biomedical Engineering, Western University Canada, 1151 Richmond Street, London, ON N6A3K7, Canada e-mail:
| | - George S Athwal
- Roth
- McFarlane Hand and Upper Limb Centre, 268 Grosvenor Street, London, ON N6A4V2, Canada e-mail:
| | - James A Johnson
- Department of Mechanical Engineering, Western University Canada, 1151 Richmond Street, London, ON N6A3K7, Canada e-mail:
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Barth J, Garret J, Geais L, Bothorel H, Saffarini M, Godenèche A. Influence of uncemented humeral stem proximal geometry on stress distributions and torsional stability following total shoulder arthroplasty. J Exp Orthop 2019; 6:8. [PMID: 30805747 PMCID: PMC6389999 DOI: 10.1186/s40634-019-0178-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 02/15/2019] [Indexed: 11/23/2022] Open
Abstract
Background While surgeons tend to implant larger stems to improve torsional stability, numerous studies demonstrated that increasing humeral stem diameter could exacerbate stress-shielding and lead to bone resorption. We aimed to determine the influence of humeral stem proximal geometry on stress distributions and torsional stability following total shoulder arthroplasty. Methods Preoperative computed tomography scans were acquired from 5 patients and processed to form 3-dimensional models of the proximal humerus. Computer models of 3 generic implants were created based on three designs: predominantly oval, semi-angular, and predominantly angular. All stems shared identical head geometry and differed only in the proximal metaphyseal area. Finite element analyses were performed, with the humerus rigidly constrained distally, and loaded to simulate the joint reaction force. Implant torsional stability and proximal bone stress distributions were assessed for the three different stem designs with three sizes: oversized (stem making contact with the cortical diaphysis), normosized (one increment smaller) and undersized (two increments smaller). Results Considering the normosized stems, the angular design increased the physiologic bone stresses at the proximal section by 39–42%, while the oval and semi-angular designs reduced them by 5–9% and 8–13%, respectively. The oval design exhibited a median rotation of 2.1°, while the semi-angular and angular designs exhibited median rotations of 1.8°. Conclusion The semi-angular stem granted an adequate compromise between physiologic stress distributed by the oval stem and torsional stability of the angular stem. Surgeons should be aware of the various benefits and drawbacks of the different humeral stem designs to ensure adequate torsional stability and physiologic loading.
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Affiliation(s)
- Johannes Barth
- Department of Orthopaedic Surgery, Centre Osteoarticulaire des Cèdres, Grenoble, France
| | | | | | - Hugo Bothorel
- ReSurg SA, Chemin de la Vuarpillière 35, 1260, Nyon, Switzerland
| | - Mo Saffarini
- ReSurg SA, Chemin de la Vuarpillière 35, 1260, Nyon, Switzerland.
| | | | - Arnaud Godenèche
- Ramsay Générale de Santé, Hôpital Privé Jean Mermoz, Centre Orthopédique Santy, Lyon, France
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Reeves JM, Athwal GS, Johnson JA, Langohr GDG. The Effect of Inhomogeneous Trabecular Stiffness Relationship Selection on Finite Element Outcomes for Shoulder Arthroplasty. J Biomech Eng 2019; 141:2718204. [DOI: 10.1115/1.4042172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Indexed: 11/08/2022]
Abstract
An important feature of humeral orthopedic finite element (FE) models is the trabecular stiffness relationship. These relationships depend on the anatomic site from which they are derived; but have not been developed for the humerus. As a consequence, humeral FE modeling relies on relationships for other anatomic sites. The variation in humeral FE outcomes due to the trabecular stiffness relationship is assessed. Stemless arthroplasty FE models were constructed from CT scans of eight humeri. Models were loaded corresponding to 45 deg and 75 deg abduction. Each bone was modeled five times with the only variable being the trabecular stiffness relationship: four derived from different anatomic-sites and one pooled across sites. The FE outcome measures assessed were implant-bone contact percentage, von Mises of the change in stress, and bone response potential. The variance attributed to the selection of the trabecular stiffness relationship was quantified as the standard deviation existing between models of different trabecular stiffness. Overall, variability due to changing the trabecular stiffness relationship was low for all humeral FE outcome measures assessed. The variability was highest within the stress and bone formation potential outcome measures of the trabecular region. Variability only exceeded 10% in the trabecular stress change within two of the eight slices evaluated. In conclusion, the low variations attributable to the selection of a trabecular stiffness relationship based on anatomic-site suggest that FE models constructed for shoulder arthroplasty can utilize an inhomogeneous site-pooled trabecular relationship without inducing marked variability in the assessed outcome measures.
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Affiliation(s)
- Jacob M. Reeves
- Department of Mechanical Engineering, Western University Canada, 1151 Richmond Street, London, ON N6A3K7, Canada e-mail:
| | - George S. Athwal
- Roth
- McFarlane Hand and Upper Limb Centre, 268 Grosvenor StreetE-p, London, ON N6A4V2, Canada e-mail:
| | - James A. Johnson
- Department of Mechanical Engineering, Western University Canada, 1151 Richmond Street, London, ON N6A3K7, Canada e-mail:
| | - G. Daniel G. Langohr
- Department of Mechanical Engineering, Western University Canada, 1151 Richmond Street, London, ON N6A3K7, Canada e-mail:
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Knowles NK, Reeves JM, Ferreira LM. Quantitative Computed Tomography (QCT) derived Bone Mineral Density (BMD) in finite element studies: a review of the literature. J Exp Orthop 2016; 3:36. [PMID: 27943224 PMCID: PMC5234499 DOI: 10.1186/s40634-016-0072-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 11/30/2016] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Finite element modeling of human bone provides a powerful tool to evaluate a wide variety of outcomes in a highly repeatable and parametric manner. These models are most often derived from computed tomography data, with mechanical properties related to bone mineral density (BMD) from the x-ray energy attenuation provided from this data. To increase accuracy, many researchers report the use of quantitative computed tomography (QCT), in which a calibration phantom is used during image acquisition to improve the estimation of BMD. Since model accuracy is dependent on the methods used in the calculation of BMD and density-mechanical property relationships, it is important to use relationships developed for the same anatomical location and using the same scanner settings, as these may impact model accuracy. The purpose of this literature review is to report the relationships used in the conversion of QCT equivalent density measures to ash, apparent, and/or tissue densities in recent finite element (FE) studies used in common density-modulus relationships. For studies reporting experimental validation, the validation metrics and results are presented. RESULTS Of the studies reviewed, 29% reported the use of a dipotassium phosphate (K2HPO4) phantom, 47% a hydroxyapatite (HA) phantom, 13% did not report phantom type, 7% reported use of both K2HPO4 and HA phantoms, and 4% alternate phantom types. Scanner type and/or settings were omitted or partially reported in 31% of studies. The majority of studies used densitometric and/or density-modulus relationships derived from different anatomical locations scanned in different scanners with different scanner settings. The methods used to derive various densitometric relationships are reported and recommendations are provided toward the standardization of reporting metrics. CONCLUSIONS This review assessed the current state of QCT-based FE modeling with use of clinical scanners. It was found that previously developed densitometric relationships vary by anatomical location, scanner type and settings. Reporting of all parameters used when referring to previously developed relationships, or in the development of new relationships, may increase the accuracy and repeatability of future FE models.
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Affiliation(s)
- Nikolas K. Knowles
- Graduate Program in Biomedical Engineering, The University of Western Ontario, 1151 Richmond St, London, ON Canada
- Roth|McFarlane Hand and Upper Limb Centre, Surgical Mechatronics
Laboratory, St. Josephs Health Care, 268 Grosvenor St, London, ON Canada
- Collaborative Training Program in Musculoskeletal Health Research, and
Bone and Joint Institute, The University of Western Ontario, 1151 Richmond St, London, ON Canada
| | - Jacob M. Reeves
- Roth|McFarlane Hand and Upper Limb Centre, Surgical Mechatronics
Laboratory, St. Josephs Health Care, 268 Grosvenor St, London, ON Canada
- Collaborative Training Program in Musculoskeletal Health Research, and
Bone and Joint Institute, The University of Western Ontario, 1151 Richmond St, London, ON Canada
- Department of Mechanical and Materials Engineering, The University of Western Ontario, 1151 Richmond St, London, ON Canada
| | - Louis M. Ferreira
- Graduate Program in Biomedical Engineering, The University of Western Ontario, 1151 Richmond St, London, ON Canada
- Roth|McFarlane Hand and Upper Limb Centre, Surgical Mechatronics
Laboratory, St. Josephs Health Care, 268 Grosvenor St, London, ON Canada
- Collaborative Training Program in Musculoskeletal Health Research, and
Bone and Joint Institute, The University of Western Ontario, 1151 Richmond St, London, ON Canada
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Quantifying the competing relationship between adduction range of motion and baseplate micromotion with lateralization of reverse total shoulder arthroplasty. J Biomech 2016; 52:24-30. [PMID: 28024662 DOI: 10.1016/j.jbiomech.2016.11.053] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 11/17/2016] [Accepted: 11/19/2016] [Indexed: 11/21/2022]
Abstract
Lateralizing the center of rotation (COR) of reverse total shoulder arthroplasty (rTSA) could improve functional outcomes and mitigate scapular notching, a commonly occurring complication of the procedure. However, resulting increases in torque at the bone-implant interface may negatively affect initial fixation of the glenoid-side component, especially if only two fixation screws can be placed. Shoulder-specific finite element (FE) models of four fresh-frozen cadaveric shoulders were constructed. Scapular geometry and material property distributions were derived from CT data. Generic baseplates with two and four fixation screws were virtually implanted, after which superiorly-oriented shear loads, accompanied by a compressive load, were applied incrementally further from the glenoid surface to simulate lateralization of the COR. Relationships between lateralization, adduction range of motion (ROM), the number of fixation screws and micromotion of the baseplate (initial implant fixation) were characterized. Lateralization significantly increases micromotion (p=0.015) and adduction ROM (p=0.001). Using two, versus four, baseplate fixation screws significantly increases micromotion (p=0.008). The effect of lateralization and the number of screws on adduction ROM and baseplate fixation is variable on a shoulder-specific basis. Trade-offs exist between functional outcomes, namely adduction ROM, and initial implant fixation and the negative effect of lateralization on implant fixation is amplified when only two fixation screws are used. The possibility of lateralizing the COR in order to improve functional outcomes of the procedure should be considered on a patient-specific basis accounting for factors such as availability and quality of bone stock.
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