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Silvestros P, Athwal GS, Giles JW. Scapular morphology variation affects reverse total shoulder arthroplasty biomechanics. A predictive simulation study using statistical and musculoskeletal shoulder models. J Orthop Res 2024. [PMID: 38341683 DOI: 10.1002/jor.25801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 09/11/2023] [Accepted: 01/20/2024] [Indexed: 02/13/2024]
Abstract
Reverse total shoulder arthroplasty (RTSA) accounts for over half of shoulder replacement surgeries. At present, the optimal position of RTSA components is unknown. Previous biomechanical studies have investigated the effect of construct placement to quantify mobility, stability and functionality postoperatively. While studies have provided valuable information on construct design and surgical placement, they have not systematically evaluated the importance of scapular morphology on biomechanical outcomes. The aim of this study was to assess the influence of scapular morphology variation on RTSA biomechanics using statistical models, musculoskeletal modeling and predictive simulation. The scapular geometry of a musculoskeletal model was altered across six modes of variation at four levels (±1 and ±3 SD) from a clinically derived statistical shape model. For each model, a standardized virtual surgery was performed to place RTSA components in the same relative position on each model then implemented in 50 predictive simulations of upward and lateral reaching tasks. Results showed morphology affected functional changes in the deltoid moment arms and recruitment for the two tasks. Variation of the anatomy that reduced the efficiency of the deltoids showed increased levels of muscle force production, joint load magnitude and shear. These findings suggest that scapular morphology plays an important role in postoperative biomechanical function of the shoulder with an implanted RTSA. Furthermore a "one-size-fits-all" approach for construct surgical placement may lead to suboptimal patient outcomes across a clinical population. Patient glenoid as well as scapular anatomy may need to be carefully considered when planning RTSA to optimize postoperative success.
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Affiliation(s)
- Pavlos Silvestros
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia, Canada
| | - George S Athwal
- Division of Shoulder and Elbow Surgery, Department of Orthopaedic Surgery, Roth/McFarlane Hand and Upper Limb Centre, London, Ontario, Canada
| | - Joshua W Giles
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia, Canada
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Willerth SM, Giles JW, Lindberg GCJ. Editorial: Novel biomaterial strategies for osteogenic treatments. Front Bioeng Biotechnol 2023; 11:1137760. [PMID: 36714007 PMCID: PMC9880529 DOI: 10.3389/fbioe.2023.1137760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 01/06/2023] [Indexed: 01/15/2023] Open
Affiliation(s)
- Stephanie M. Willerth
- Department of Mechanical Engineering, University of Victoria, Victoria, BC, Canada,Division of Medical Sciences, University of Victoria, Victoria, BC, Canada,Centre for Advanced Materials and Technology, University of Victoria, Victoria, BC, Canada,School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada,*Correspondence: Stephanie M. Willerth,
| | - Joshua W. Giles
- Department of Mechanical Engineering, University of Victoria, Victoria, BC, Canada,Department of Orthopaedics, University of British Columbia, Vancouver, BC, Canada
| | - Gabriella C. J. Lindberg
- Department of Bioengineering, The Phil and Penny Knight Campus for Accelerating Scientific Impact, University of Oregon, Eugene, OR, United States,Department of Orthopedic Surgery and Musculoskeletal Medicine, University of Otago, Christchurch, New Zealand
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Aminov O, Regan W, Giles JW, Simon MJK, Hodgson AJ. Targeting repeatability of a less obtrusive surgical navigation procedure for total shoulder arthroplasty. Int J Comput Assist Radiol Surg 2021; 17:283-293. [PMID: 34611779 DOI: 10.1007/s11548-021-02503-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 09/17/2021] [Indexed: 01/12/2023]
Abstract
PURPOSE Surgical navigation systems have demonstrated improvements in alignment accuracy in a number of arthroplasty procedures, but they have not yet been widely adopted for use in total shoulder arthroplasty (TSA). We believe this is due in part to the obtrusiveness of conventional optical tracking systems, as well as the need for additional intraoperative steps such as calibration and registration. The purpose of this study is to evaluate the feasibility of adapting a less-intrusive dental navigation system for use in TSA. METHODS We developed a proof-of-concept system based on validated laser-engraved surgical tools recently introduced for use in dental surgery that are calibrated once when manufactured and not recalibrated at time of use. The design also features a notably smaller bone-mounted tracker that can be tracked from a wide range of viewing angles. To assess our system's performance, we modified the dental surgical software to support guidance of a TSA procedure. We then conducted a user study in which three participants with varying surgical experience used the system to drill 30 holes in a glenoid model. Using a coordinate measuring machine, we determined the resulting drilled trajectory and compared this to the pre-planned trajectory. Since we used a model glenoid rather than anatomical specimens, we report on targeting precision rather than overall procedure precision or accuracy. RESULTS We found targeting precision < 1 mm (standard deviation) for locating the entry hole and < ~ 1° (SD) for both version and inclination. The latter value was markedly lower than the end-to-end angular precision achieved by previously reported TSA navigation systems (approximately 3°-5° SD). CONCLUSION We conclude that variability during the targeting phase represents a small fraction of the overall variability exhibited by existing systems, so a less obtrusive navigation system for TSA based on laser-engraved tooling is likely feasible, which could improve the uptake rates of surgical navigation for TSA, thereby potentially leading to improved overall surgical outcomes.
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Affiliation(s)
- Oded Aminov
- Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada.
| | - William Regan
- Department of Orthopedics, UBC, Vancouver, BC, Canada
| | - Joshua W Giles
- Mechanical Engineering, University of Victoria, Victoria, BC, Canada
| | - Maciej J K Simon
- Department of Orthopedics, UBC, Vancouver, BC, Canada.,Department of Orthopaedic and Trauma Surgery, University Medical Center Schleswig-Holstein - Campus Kiel, Arnold-Heller-Str. 3, 24105, Kiel, Germany
| | - Antony J Hodgson
- Mechanical Engineering, University of British Columbia, Vancouver, BC, Canada
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Studders C, Fraser I, Giles JW, Willerth SM. Evaluation of 3D-printer settings for producing personal protective equipment. ACTA ACUST UNITED AC 2021; 5. [PMID: 34460874 PMCID: PMC8384239 DOI: 10.2217/3dp-2021-0005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 07/28/2021] [Indexed: 12/02/2022]
Abstract
Aim: COVID-19 resulted in a shortage of personal protective equipment. Community members united to 3D-print face shield headbands to support local healthcare workers. This study examined factors altering print time and strength. Materials & methods: Combinations of infill density (50%, 100%), shell thickness (0.8, 1.2 mm), line width (0.2 mm, 0.4 mm), and layer height (0.1 mm, 0.2 mm) were evaluated through tensile testing, finite element analysis, and printing time. Results: Strength increased with increased infill (p < 0.001) and shell thickness (p < 0.001). Layer height had no effect on strength. Increasing line width increased strength (p < 0.001). Discussion: Increasing layer height and line width decreased print time by 50 and 39%, respectively. Increased shell thickness did not alter print time. These changes are recommended for printing.
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Affiliation(s)
- Carson Studders
- University of Victoria Department of Mechanical Engineering, Center for Biomedical Research, 3800 Finnerty Road, Victoria, BC V8W 2Y2, Canada
| | - Ian Fraser
- University of Victoria Department of Mechanical Engineering, Center for Biomedical Research, 3800 Finnerty Road, Victoria, BC V8W 2Y2, Canada
| | - Joshua W Giles
- University of Victoria Department of Mechanical Engineering, Center for Biomedical Research, 3800 Finnerty Road, Victoria, BC V8W 2Y2, Canada
| | - Stephanie M Willerth
- University of Victoria Department of Mechanical Engineering, Center for Biomedical Research, 3800 Finnerty Road, Victoria, BC V8W 2Y2, Canada
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Giles JW, Brodén C, Tempelaere C, Emery RJH, Rodriguez y Baena F. Development and ex-vivo assessment of a novel patient specific guide and instrumentation system for minimally invasive total shoulder arthroplasty. PLoS One 2021; 16:e0251880. [PMID: 34019573 PMCID: PMC8139503 DOI: 10.1371/journal.pone.0251880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 05/04/2021] [Indexed: 11/22/2022] Open
Abstract
Objective To develop and assess a novel guidance technique and instrumentation system for minimally invasive short-stemmed total shoulder arthroplasty that will help to reduce the complications associated with traditional open replacement such as poor muscle healing and neurovascular injury. We have answered key questions about the developed system including (1) can novel patient-specific guides be accurately registered and used within a minimally invasive environment?; (2) can accuracy similar to traditional techniques be achieved? Methods A novel intra-articular patient-specific guide was developed for use with a new minimally invasive posterior surgical approach that guides bone preparation without requiring muscle resection or joint dislocation. Additionally, a novel set of instruments were developed to enable bone preparation within the minimally invasive environment. The full procedure was evaluated in six cadaveric shoulders, using digitizations to assess accuracy of each step. Results Patient-specific guide registration accuracy in 3D translation was 2.2±1.2mm (RMSE±1 SD; p = 0.007) for the humeral component and 2.7±0.7mm (p<0.001) for the scapula component. Final implantation accuracy was 2.9±3.0mm (p = 0.066) in translation and 5.7–6.8±2.2–4.0° (0.001<p<0.009) across the humerus implants’ three rotations. Similarly, the glenoid component’s implantation accuracy was 3.0±1.7mm (p = 0.008) in translation and 2.3–4.3±2.2–4.4° (0.008<p<0.09) in rotation. Conclusion This system achieves minimally invasive shoulder replacement with accuracy similar to traditional open techniques while avoiding common causes of complications. Significance This novel technique could lead to a paradigm shift in shoulder arthroplasty for patients with moderate arthritis, which could significantly improve rehabilitation and functional outcomes.
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Affiliation(s)
- Joshua W. Giles
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia, Canada
- Department of Mechanical Engineering, Imperial College London, London, United Kingdom
- * E-mail: (JWG); (FRB)
| | - Cyrus Brodén
- Department of Surgery and Cancer, Imperial College London, London, United Kingdom
| | - Christine Tempelaere
- Department of Surgery and Cancer, Imperial College London, London, United Kingdom
| | - Roger J. H. Emery
- Department of Surgery and Cancer, Imperial College London, London, United Kingdom
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Brodén C, Sandberg O, Sköldenberg O, Stigbrand H, Hänni M, Giles JW, Emery R, Lazarinis S, Nyström A, Olivecrona H. Low-dose CT-based implant motion analysis is a precise tool for early migration measurements of hip cups: a clinical study of 24 patients. Acta Orthop 2020; 91:260-265. [PMID: 32056507 PMCID: PMC8023951 DOI: 10.1080/17453674.2020.1725345] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Background and purpose - Early implant migration is known to be a predictive factor of clinical loosening in total hip arthroplasty (THA). Radiostereometric analysis (RSA) is the gold standard used to measure early migration in patients. However, RSA requires costly, specialized imaging equipment and the image process is complex. We determined the precision of an alternative, commercially available, CT method in 3 ongoing clinical THA studies, comprising 3 different cups.Materials and methods - 24 CT double examinations of 24 hip cups were selected consecutively from 3 ongoing prospective studies: 2 primary THA (1 cemented and 1 uncemented) and 1 THA (cemented) revision study. Precision of the CT-based implant motion analysis (CTMA) system was calculated separately for each study, using both the surface anatomy of the pelvis and metal beads placed in the pelvis.Results - For the CTMA analysis using the surface anatomy of the pelvis, the precision ranged between 0.07 and 0.31 mm in translation and 0.20° and 0.39° for rotation, respectively. For the CTMA analysis using beads the precision ranged between 0.08 and 0.20 mm in translation and between 0.20° and 0.43° for rotations. The radiation dose ranged between 0.2 and 2.3 mSv.Interpretation - CTMA achieved a clinically relevant and consistent precision between the 3 different hip cups studied. The use of different hip cup types, different CT scanners, or registration method (beads or surface anatomy) had no discernible effect on precision. Therefore, CTMA without the use of bone markers could potentially be an alternative to RSA to measure early migration.
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Affiliation(s)
- Cyrus Brodén
- Department of Surgery and Cancer, Imperial College London, London, UK; ,Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden; ,Correspondence:
| | | | - Olof Sköldenberg
- Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden;
| | - Hampus Stigbrand
- Department of Orthopedic Surgery, Länssjukhuset, Gävle, Sweden; Center for Research and Development, Uppsala University/County Council of Gävleborg, Sweden;
| | - Mari Hänni
- Department of Surgical Sciences, Section of Radiology, Uppsala University Hospital, Uppsala, Sweden;
| | - Joshua W Giles
- Department of Mechanical Engineering, University of Victoria, Victoria, BC, Canada;
| | - Roger Emery
- Department of Orthopaedic Surgery, St Mary’s Hospital, London, UK;
| | - Stergios Lazarinis
- Department of Orthopedics, Institute of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden;
| | - Andreas Nyström
- Department of Orthopedics, Institute of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden;
| | - Henrik Olivecrona
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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Brodén C, Giles JW, Popat R, Fetherston S, Olivecrona H, Sandberg O, Maguire GQ, Noz ME, Sköldenberg O, Emery R. Accuracy and precision of a CT method for assessing migration in shoulder arthroplasty: an experimental study. Acta Radiol 2020; 61:776-782. [PMID: 31684750 DOI: 10.1177/0284185119882659] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Radiostereometric analysis (RSA) is the gold standard to measure early implant migration which is a predictive factor for implant survival. PURPOSE To validate an alternative computed tomography (CT) technique to measure implant migration in shoulder arthroplasty. MATERIAL AND METHODS A cadaver proximal humerus and a scapula, which had tantalum beads incorporated within them, were prepared to accept a short-stemmed humeral component and a two-pegged glenoid component of a commercial total shoulder arthroplasty (TSA) system. A five degree of freedom micrometer and goniometer equipped rig was used to translate and rotate the implant components relative to the respective bone to predetermined positions. Double CT examinations were performed for each position and CT motion analysis software (CTMA) was used to assess these movements. The accuracy and precision of the software was estimated using the rig's micrometers and goniometers as the gold standard. The technique's effective dose was also assessed. RESULTS The accuracy was in the range of 0.07-0.23 mm in translation and 0.22-0.71° in rotation. The precision was in the range of 0.08-0.15 mm in translation and 0.23-0.54° in rotation. The mean effective dose for the CT scans was calculated to be 0.27 mSv. CONCLUSION In this experimental setting, accuracy, precision, and effective dose of the CTMA technique were found to be comparable to that of RSA. Therefore, we believe clinical studies are warranted to determine if CTMA is a suitable alternative to traditional RSA for migration measurements in TSA.
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Affiliation(s)
- Cyrus Brodén
- Department of Surgery and Cancer, Imperial College London, St Mary’s Hospital, London, UK
- Karolinska Institutet, Department of Clinical Sciences, Danderyd Hospital, Division of Orthopaedics, Stockholm, Sweden
| | - Joshua W Giles
- Department of Mechanical Engineering, University of Victoria, Victoria, BC, Canada
- Mechatronics in Medicine Laboratory, Mechanical Engineering, Imperial College London, London, UK
| | - Ravi Popat
- Department of Bioengineering, Imperial College London, London, UK
| | - Shirley Fetherston
- Department of Radiology, St Mary’s Hospital, Imperial College Healthcare NHS Trust, London, UK
| | - Henrik Olivecrona
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | | | - Gerald Q Maguire
- School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Marilyn E Noz
- Department of Radiology, New York University School of Medicine, New York, NY, USA
| | - Olof Sköldenberg
- Karolinska Institutet, Department of Clinical Sciences, Danderyd Hospital, Division of Orthopaedics, Stockholm, Sweden
| | - Roger Emery
- Department of Surgery and Cancer, Imperial College London, St Mary’s Hospital, London, UK
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Abdulla I, Langohr DG, Giles JW, Johnson JA, Athwal GS. The effect of humeral polyethylene insert constraint on reverse shoulder arthroplasty biomechanics. Shoulder Elbow 2018; 10:25-31. [PMID: 29276534 PMCID: PMC5734524 DOI: 10.1177/1758573217701065] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 02/08/2017] [Indexed: 11/17/2022]
Abstract
BACKGROUND There is little information on the effects of altering reverse shoulder arthroplasty (RSA) polyethylene constraint on joint load, load angle and deltoid force. The present biomechanical study aimed to investigate the effects of changing RSA polyethylene constraint on joint load, load angle, deltoid force and range of motion. METHODS A custom RSA implant capable of measuring forces across the joint with varying polyethylene constraint was tested in six cadaveric shoulders. Standard-, low- and high-constraint (retentive) polyethylene liners were tested, and joint kinematics, loads and muscle forces were recorded. RESULTS When polyethylene constraint was altered, joint load and load angle during active abduction were not affected significantly (p > 0.19). Additionally, the force required by the deltoid for active abduction was not affected significantly by cup constraint (p = 0.144). Interestingly, active abduction range of motion was also not affected significantly by changes in cup constraint (p > 0.45). CONCLUSIONS Altering polyethylene cup constraint in RSA to enhance stability does not significantly alter resultant joint loads and deltoid forces. Surprisingly, terminal abduction range of motion was also not significantly different with varying cup constraint, indicating that terminal impingement may be tuberosity related rather than polyethylene.
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Affiliation(s)
| | | | | | | | - George S. Athwal
- George S Athwal, St Joseph’s Health Care London Roth
- McFarlane Hand & Upper Limb Center 268 Grosvenor Street, Room D0-205 London, Ontario N6A 4L6, Canada.
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Abstract
BACKGROUND Short-stem humeral replacements achieve fixation by anchoring to the metaphyseal trabecular bone. Fixing the implant in high-density bone can provide strong fixation and reduce the risk of loosening. However, there is a lack of data mapping the bone density distribution in the proximal humerus. The aim of the study was to investigate the bone density in proximal humerus. METHODS Eight computed tomography scans of healthy cadaveric humeri were used to map bone density distribution in the humeral head. The proximal humeral head was divided into 12 slices parallel to the humeral anatomic neck. Each slice was then divided into 4 concentric circles. The slices below the anatomic neck, where short-stem implants have their fixation features, were further divided into radial sectors. The average bone density for each of these regions was calculated, and regions of interest were compared using a repeated-measures analysis of variance with significance set at P < .05. RESULTS Average apparent bone density was found to decrease from proximal to distal regions, with the majority of higher bone density proximal to the anatomic neck of the humerus (P < .05). Below the anatomic neck, bone density increases from central to peripheral regions, where cortical bone eventually occupies the space (P < .05). In distal slices below the anatomic neck, a higher bone density distribution in the medial calcar region was also observed. CONCLUSION This study indicates that it is advantageous with respect to implant fixation to preserve some bone above the anatomic neck and epiphyseal plate and to use the denser bone at the periphery.
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Affiliation(s)
- Hamidreza Alidousti
- Department of Mechanical Engineering, Imperial College London, London, UK,Reprint requests: Hamidreza Alidousti, PhD, Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK. (H. Alidousti).Department of Mechanical EngineeringImperial College LondonLondonSW7 2AZUK
| | - Joshua W. Giles
- Department of Mechanical Engineering, Imperial College London, London, UK
| | - Roger J.H. Emery
- Department of Surgery & Cancer, Imperial College London, London, UK
| | - Jonathan Jeffers
- Department of Mechanical Engineering, Imperial College London, London, UK
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Lalone EA, Shannon HL, Deluce SR, Giles JW, King GJW, Johnson JA. Effect of Radial Head Implant Shape on Radiocapitellar Joint Congruency. J Hand Surg Am 2017; 42:476.e1-476.e11. [PMID: 28450100 DOI: 10.1016/j.jhsa.2017.03.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 02/14/2017] [Accepted: 03/09/2017] [Indexed: 02/02/2023]
Abstract
PURPOSE Radial head arthroplasty is indicated in displaced fractures in which comminution precludes successful internal fixation. Many types of radial head implants have been developed varying in material, methods of fixation, and degrees of modularity and geometry. The purpose of this study was to investigate the effect of radial head implant shape on radiocapitellar joint congruency. METHODS Joint congruency was quantified in 7 cadaveric specimens employing a registration and inter-surface distance algorithm and 3-dimensional models obtained using computed tomography. Forearm rotation was simulated after computer-guided implantation of an axisymmetric radial head, a population-based quasi-anatomic radial head implant, and a reverse-engineered anatomic radial head implant. Inter-surface distances were measured to investigate the relative position of the radial head implant and displayed on 3-dimensional color-contour maps. Surface area was measured for inter-surface distances (1.5 mm) and compared for each radial head geometry. RESULTS There were no statistical differences in the contact surface area between radial head implants during active or passive forearm rotation. The joint was more congruent (larger contact surface area) during active forearm rotation compared with passive forearm rotation. CONCLUSIONS This study investigated the effect of implant geometry on the radiocapitellar joint contact mechanics by examining a commercially available radial head system (axisymmetric), a quasi-anatomic design, and an anatomic reverse-engineered radial head implant. We found no statistical differences in radiocapitellar joint contact mechanics as measured by 3-dimensional joint congruency in cadaveric specimens undergoing continuous simulated forearm rotation. CLINICAL RELEVANCE The importance of choosing an implant that matches the general size of the native radial head is recognized, but the degree to which it is necessary to create an implant that replicates the native anatomy to restore elbow stability and prevent cartilage degenerative changes remains unclear. This study concluded that the geometry of the implant did not have a statistically significant effect on joint contact mechanics; therefore, future work is needed to examine additional factors related to implant design, such as material choice and implant positioning to investigate their influence on joint contact mechanics.
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Affiliation(s)
- Emily A Lalone
- Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, St Joseph's Hospital, London, Canada
| | - Hannah L Shannon
- Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, St Joseph's Hospital, London, Canada
| | - Simon R Deluce
- Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, St Joseph's Hospital, London, Canada
| | - Joshua W Giles
- Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, St Joseph's Hospital, London, Canada
| | - Graham J W King
- Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, St Joseph's Hospital, London, Canada; Department of Surgery, University of Western Ontario, London, Canada
| | - James A Johnson
- Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, St Joseph's Hospital, London, Canada; Department of Mechanical and Materials Engineering, University of Western Ontario, London, Canada.
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11
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Giles JW, Langohr GDG, Johnson JA, Athwal GS. The rotator cuff muscles are antagonists after reverse total shoulder arthroplasty. J Shoulder Elbow Surg 2016; 25:1592-600. [PMID: 27107733 DOI: 10.1016/j.jse.2016.02.028] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 02/18/2016] [Accepted: 02/24/2016] [Indexed: 02/01/2023]
Abstract
INTRODUCTION There is disagreement regarding whether, when possible, the rotator cuff should be repaired in conjunction with reverse total shoulder arthroplasty (RTSA). Therefore, we investigated the effects of rotator cuff repair in RTSA models with varying magnitudes of humeral and glenosphere lateralization. METHODS Six fresh frozen cadaveric shoulders were tested on a validated in vitro muscle-driven motion simulator. Each specimen was implanted with a custom adjustable, load-sensing RTSA after creation of a simulated rotator cuff tear. The effects of 4 RTSA configurations (0 and 10 mm of humeral lateralization and glenosphere lateralization) on deltoid force and joint load during abduction with and without rotator cuff repair were assessed. RESULTS Deltoid force was significantly affected by increasing humeral lateralization (-2.5% ± 1.7% body weight [BW], P = .016) and glenosphere lateralization (+7.7% ± 5.6% BW, P = .016). Rotator cuff repair interacted with humeral and glenosphere lateralization (P = .005), such that with no humeral lateralization, glenosphere lateralization increased deltoid force without cuff repair (8.1% ± 5.1% BW, P = .012). This effect was increased with cuff repair (12.8% ± 7.8% BW, P = .010), but the addition of humeral lateralization mitigated this effect. Rotator cuff repair increased joint load (+11.9% ± 5.1% BW, P = .002), as did glenosphere lateralization (+13.3% ± 3.7% BW, P < .001). These interacted, such that increasing glenosphere lateralization markedly increased the negative effects of cuff repair (9.4% ± 3.2% BW [P = .001] vs. 14.4% ± 7.4% BW [P = .005]). CONCLUSION Rotator cuff repair, especially in conjunction with glenosphere lateralization, produces an antagonistic effect that increases deltoid and joint loading. The long-term effects of this remain unknown; however, combining these factors may prove undesirable. Humeral lateralization improves joint compression through deltoid wrapping and increases the deltoid's mechanical advantage, and therefore, could be used in place of rotator cuff repair, thus avoiding its complications.
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Affiliation(s)
- Joshua W Giles
- Department of Mechanical Engineering, Imperial College London, London, UK; Bioengineering Research Laboratory, Roth McFarlane Hand and Upper Limb Centre, St. Joseph's Health Care, Western University, London, ON, Canada
| | - G Daniel G Langohr
- Bioengineering Research Laboratory, Roth McFarlane Hand and Upper Limb Centre, St. Joseph's Health Care, Western University, London, ON, Canada
| | - James A Johnson
- Bioengineering Research Laboratory, Roth McFarlane Hand and Upper Limb Centre, St. Joseph's Health Care, Western University, London, ON, Canada
| | - George S Athwal
- Bioengineering Research Laboratory, Roth McFarlane Hand and Upper Limb Centre, St. Joseph's Health Care, Western University, London, ON, Canada.
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Baumer TG, Giles JW, Drake A, Zauel R, Bey MJ. Measuring Three-Dimensional Thorax Motion Via Biplane Radiographic Imaging: Technique and Preliminary Results. J Biomech Eng 2016; 138:2473568. [PMID: 26592901 DOI: 10.1115/1.4032058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Indexed: 11/08/2022]
Abstract
Measures of scapulothoracic motion are dependent on accurate imaging of the scapula and thorax. Advanced radiographic techniques can provide accurate measures of scapular motion, but the limited 3D imaging volume of these techniques often precludes measurement of thorax motion. To overcome this, a thorax coordinate system was defined based on the position of rib pairs and then compared to a conventional sternum/spine-based thorax coordinate system. Alignment of the rib-based coordinate system was dependent on the rib pairs used, with the rib3:rib4 pairing aligned to within 4.4 ± 2.1 deg of the conventional thorax coordinate system.
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Welsh MF, Willing RT, Giles JW, Athwal GS, Johnson JA. A rigid body model for the assessment of glenohumeral joint mechanics: Influence of osseous defects on range of motion and dislocation. J Biomech 2016; 49:514-9. [DOI: 10.1016/j.jbiomech.2015.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 10/31/2015] [Accepted: 11/02/2015] [Indexed: 11/25/2022]
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Giles JW, Langohr GDG, Johnson JA, Athwal GS. Implant Design Variations in Reverse Total Shoulder Arthroplasty Influence the Required Deltoid Force and Resultant Joint Load. Clin Orthop Relat Res 2015; 473:3615-26. [PMID: 26310680 PMCID: PMC4586233 DOI: 10.1007/s11999-015-4526-0] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 08/14/2015] [Indexed: 01/31/2023]
Abstract
BACKGROUND Reverse total shoulder arthroplasty (RTSA) is widely used; however, the effects of RTSA geometric parameters on joint and muscle loading, which strongly influence implant survivorship and long-term function, are not well understood. By investigating these parameters, it should be possible to objectively optimize RTSA design and implantation technique. QUESTIONS/PURPOSES The purposes of this study were to evaluate the effect of RTSA implant design parameters on (1) the deltoid muscle forces required to produce abduction, and (2) the magnitude of joint load and (3) the loading angle throughout this motion. We also sought to determine how these parameters interacted. METHODS Seven cadaveric shoulders were tested using a muscle load-driven in vitro simulator to achieve repeatable motions. The effects of three implant parameters-humeral lateralization (0, 5, 10 mm), polyethylene thickness (3, 6, 9 mm), and glenosphere lateralization (0, 5, 10 mm)-were assessed for the three outcomes: deltoid muscle force required to produce abduction, magnitude of joint load, and joint loading angle throughout abduction. RESULTS Increasing humeral lateralization decreased deltoid forces required for active abduction (0 mm: 68% ± 8% [95% CI, 60%-76% body weight (BW)]; 10 mm: 65% ± 8% [95% CI, 58%-72 % BW]; p = 0.022). Increasing glenosphere lateralization increased deltoid force (0 mm: 61% ± 8% [95% CI, 55%-68% BW]; 10 mm: 70% ± 11% [95% CI, 60%-81% BW]; p = 0.007) and joint loads (0 mm: 53% ± 8% [95% CI, 46%-61% BW]; 10 mm: 70% ± 10% [95% CI, 61%-79% BW]; p < 0.001). Increasing polyethylene cup thickness increased deltoid force (3 mm: 65% ± 8% [95% CI, 56%-73% BW]; 9 mm: 68% ± 8% [95% CI, 61%-75% BW]; p = 0.03) and joint load (3 mm: 60% ± 8% [95% CI, 53%-67% BW]; 9 mm: 64% ± 10% [95% CI, 56%-72% BW]; p = 0.034). CONCLUSIONS Humeral lateralization was the only parameter that improved joint and muscle loading, whereas glenosphere lateralization resulted in increased loads. Humeral lateralization may be a useful implant parameter in countering some of the negative effects of glenosphere lateralization, but this should not be considered the sole solution for the negative effects of glenosphere lateralization. Overstuffing the articulation with progressively thicker humeral polyethylene inserts produced some adverse effects on deltoid muscle and joint loading. CLINICAL RELEVANCE This systematic evaluation has determined that glenosphere lateralization produces marked negative effects on loading outcomes; however, the importance of avoiding scapular notching may outweigh these effects. Humeral lateralization's ability to decrease the effects of glenosphere lateralization was promising but further investigations are required to determine the effects of combined lateralization on functional outcomes including range of motion.
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Affiliation(s)
- Joshua W. Giles
- Roth McFarlane Hand and Upper Limb Centre, 268 Grosvenor Street, London, ON N6A 4V2 Canada ,Western University, London, ON Canada ,Mechatronics in Medicine Laboratory, Department of Mechanical Engineering, Imperial College London, London, UK
| | - G. Daniel G. Langohr
- Roth McFarlane Hand and Upper Limb Centre, 268 Grosvenor Street, London, ON N6A 4V2 Canada ,Western University, London, ON Canada
| | - James A. Johnson
- Roth McFarlane Hand and Upper Limb Centre, 268 Grosvenor Street, London, ON N6A 4V2 Canada ,Western University, London, ON Canada
| | - George S. Athwal
- Roth McFarlane Hand and Upper Limb Centre, 268 Grosvenor Street, London, ON N6A 4V2 Canada ,Western University, London, ON Canada
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Glennie RA, Giles JW, Johnson JA, Athwal GS, Faber KJ. An in vitro study comparing limited to full cementation of polyethylene glenoid components. J Orthop Surg Res 2015; 10:142. [PMID: 26383832 PMCID: PMC4573681 DOI: 10.1186/s13018-015-0268-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 07/28/2015] [Indexed: 11/10/2022] Open
Abstract
Background Glenoid component survival is critical to good long-term outcomes in total shoulder arthroplasty. Optimizing the fixation environment is paramount. The purpose of this study was to compare two glenoid cementing techniques for fixation in total shoulder arthroplasty. Methods Sixteen cadaveric specimens were randomized to receive peg-only cementation (CPEG) or full back-side cementation (CBACK). Physiological cyclic loading was performed and implant displacement was recorded using an optical tracking system. The cement mantle was examined with micro-computed tomography before and after cyclic loading. Results Significantly greater implant displacement away from the inferior portion of the glenoid was observed in the peg cementation group when compared to the fully cemented group during the physiological loading. The displacement was greatest at the beginning of the loading protocol and persisted at a diminished rate during the remainder of the loading protocol. Micro-CT scanning demonstrated that the cement mantle remained intact in both groups and that three specimens in the CBACK group demonstrated microfracturing in one area only. Discussion Displacement of the CPEG implants away from the inferior subchondral bone may represent a suboptimal condition for long-term implant survival. Cement around the back of the implant is suggested to improve initial stability of all polyethylene glenoid implants. Clinical relevance Full cementation provides greater implant stability when compared to limited cementation techniques for insertion of glenoid implants. Loading characteristics are more favorable when cement is placed along the entire back of the implant contacting the subchondral bone.
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Affiliation(s)
- R Andrew Glennie
- Department of Orthopedics, Dalhousie University, Halifax, NS, Canada.
| | - Joshua W Giles
- Division of Orthopedics, Western University, 268 Grosvenor St, London, N6A 4L6, ON, Canada.
| | - James A Johnson
- Division of Orthopedics, Western University, 268 Grosvenor St, London, N6A 4L6, ON, Canada.
| | - George S Athwal
- Division of Orthopedics, Western University, 268 Grosvenor St, London, N6A 4L6, ON, Canada.
| | - Kenneth J Faber
- Division of Orthopedics, Western University, 268 Grosvenor St, London, N6A 4L6, ON, Canada.
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Abstract
BACKGROUND Determining the magnitude of glenoid bone loss in cases of shoulder instability is an important step in selecting the optimal reconstructive procedure. Recently, a formula has been proposed that estimates native glenoid width based on magnetic resonance imaging (MRI) measurements of height (1/3 × glenoid height + 15 mm). This technique, however, has not been validated for use with computed tomography (CT), which is often the preferred imaging modality to assess bone deficiencies. PURPOSE The purpose of this project was 2-fold: (1) to determine if the MRI-based formula that predicts glenoid width from height is valid with CT and (2) to determine if a more accurate regression can be resolved for use specifically with CT data. STUDY DESIGN Descriptive laboratory study. METHODS Ninety normal shoulder CT scans with preserved osseous anatomy were drawn from an existing database and analyzed. Measurements of glenoid height and width were performed by 2 observers on reconstructed 3-dimensional models. After assessment of reliability, the data were correlated, and regression models were created for male and female shoulders. The accuracy of the MRI-based model's predictions was then compared with that of the CT-based models. RESULTS Intra- and interrater reliabilities were good to excellent for height and width, with intraclass correlation coefficients of 0.765 to 0.992. The height and width values had a strong correlation of 0.900 (P < .001). Regression analyses for male and female shoulders produced CT-specific formulas: for men, glenoid width = 2/3 × glenoid height + 5 mm; for women, glenoid width = 2/3 × glenoid height + 3 mm. Comparison of predictions from the MRI- and CT-specific formulas demonstrated good agreement (intraclass correlation coefficient = 0.818). The CT-specific formulas produced a root mean squared error of 1.2 mm, whereas application of the MRI-specific formula to CT images resulted in a root mean squared error of 1.5 mm. CONCLUSION Use of the MRI-based formula on CT scans to predict glenoid width produced estimates that were nearly as accurate as the CT-specific formulas. The CT-specific formulas, however, are more accurate at predicting native glenoid width when applied to CT data. CLINICAL RELEVANCE Imaging-specific (CT and MRI) formulas have been developed to estimate glenoid bone loss in patients with instability. The CT-specific formula can accurately predict native glenoid width, having an error of only 2.2% of average glenoid width.
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Affiliation(s)
- Joshua W Giles
- Roth McFarlane Hand and Upper Limb Centre, London, Ontario, Canada Western University, London, Ontario, Canada Mechatronics in Medicine Laboratory, Department of Mechanical Engineering, Imperial College London, London, UK
| | - Brett D Owens
- Keller Army Hospital, US Military Academy, West Point, New York, USA
| | - George S Athwal
- Roth McFarlane Hand and Upper Limb Centre, London, Ontario, Canada Western University, London, Ontario, Canada
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Langohr GDG, Giles JW, Athwal GS, Johnson JA. The effect of glenosphere diameter in reverse shoulder arthroplasty on muscle force, joint load, and range of motion. J Shoulder Elbow Surg 2015; 24:972-9. [PMID: 25547853 DOI: 10.1016/j.jse.2014.10.018] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 10/16/2014] [Accepted: 10/19/2014] [Indexed: 02/01/2023]
Abstract
BACKGROUND Little is known about the effects of glenosphere diameter on shoulder joint loads. The purpose of this biomechanical study was to investigate the effects of glenosphere diameter on joint load, load angle, and total deltoid force required for active abduction and range of motion in internal/external rotation and abduction. METHODS A custom, instrumented reverse shoulder arthroplasty implant system capable of measuring joint load and varying glenosphere diameter (38 and 42 mm) and glenoid offset (neutral and lateral) was implanted in 6 cadaveric shoulders to provide at least 80% power for all variables. A shoulder motion simulator was used to produce active glenohumeral and scapulothoracic motion. All implant configurations were tested with active and passive motion with joint kinematics, loads, and moments recorded. RESULTS At neutral and lateralized glenosphere positions, increasing diameter significantly increased joint load (+12 ± 21 N and +6 ± 9 N; P < .01) and deltoid load required for active abduction (+9 ± 22 N and +11 ± 15 N; P < .02), whereas joint load angle was unaffected (P > .8). Passive internal rotation was reduced with increased diameter at both neutral and lateralized glenosphere positions (-6° ± 6° and -12° ± 6°; P < .002); however, external rotation was not affected (P > .05). At neutral glenosphere position, increasing diameter increased the maximum angles of both adduction (+1° ± 1°; P = .03) and abduction (+8° ± 9°; P < .05). Lateralization also increased abduction range of motion compared with neutral (P < .01). CONCLUSIONS Although increasing glenosphere diameter significantly increased joint load and deltoid force, the clinical impact of these changes is presently unclear. Internal rotation, however, was reduced, which contradicts previous bone modeling studies, which we postulate is due to increased posterior capsular tension as it is forced to wrap around a larger 42 mm implant assembly.
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Affiliation(s)
- G Daniel G Langohr
- Biomechanics Laboratory, Roth
- McFarlane Hand and Upper Limb Center, St. Joseph's Health Care, University of Western Ontario, London, ON, Canada
| | - Joshua W Giles
- Biomechanics Laboratory, Roth
- McFarlane Hand and Upper Limb Center, St. Joseph's Health Care, University of Western Ontario, London, ON, Canada
| | - George S Athwal
- Biomechanics Laboratory, Roth
- McFarlane Hand and Upper Limb Center, St. Joseph's Health Care, University of Western Ontario, London, ON, Canada.
| | - James A Johnson
- Biomechanics Laboratory, Roth
- McFarlane Hand and Upper Limb Center, St. Joseph's Health Care, University of Western Ontario, London, ON, Canada
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Abstract
BACKGROUND Recurrent shoulder instability is commonly associated with glenoid bone defects. Coracoid transfer procedures, such as the Bristow and Latarjet procedures, are frequently used to address these bone deficiencies. Despite the frequent synonymous labeling of these transfers as the "Bristow-Latarjet" procedure, their true equivalence has not been demonstrated. Therefore, our purpose was to compare the biomechanical effects of these two procedures. METHODS Eight cadaveric specimens were tested on a custom shoulder simulator capable of loading nine muscle groups and of accurately orienting the joint throughout shoulder motion. The specimens were tested in the intact state, following Bristow and Latarjet reconstructions of a capsulolabral injury (0% glenoid defect), and following each procedure after creation of 15% and 30% glenoid bone defects. The reconstruction order was randomized. In each condition, joint stiffness (anterior stability) and occurrence of dislocation were assessed in shoulder adduction and abduction with neutral and external rotation. RESULTS No significant differences (p < 0.05) in joint stiffness or stability were found between the Bristow and Latarjet reconstructions for the 0% glenoid defect in any joint position. However, substantially greater joint stiffness occurred following the Latarjet procedure, as compared with the Bristow procedure, for the 15% and 30% glenoid bone-loss conditions in adduction with neutral rotation, adduction with external rotation, and abduction with external rotation (average across the three joint positions: 8.6 ± 4.4 N/mm versus 3.9 ± 1.26.7 N/mm [p = 0.034] with 15% bone loss and 7.5 ± 4.4 N/mm versus 3.4 ± 1.5 N/mm [p = 0.045] with 30% bone loss). The Latarjet reconstruction restored the stiffness that had been measured in the intact state in eleven of the twelve tested conditions, whereas the Bristow procedure was successful in only four of the twelve conditions. In addition, during instability testing, three more specimens dislocated following the Bristow reconstruction, compared with the Latarjet procedure, in the 15% defect condition and five more dislocated in the 30% defect condition. CONCLUSIONS The Bristow and Latarjet procedures are not equivalent in terms of their effects on glenohumeral joint stiffness and stability in cases of glenoid osseous deficiency. CLINICAL RELEVANCE The Bristow and Latarjet procedures have equivalent stabilizing effects in unstable shoulders with preserved glenoid osseous anatomy. However, the Latarjet procedure confers superior stabilization in the setting of substantial glenoid bone loss.
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Affiliation(s)
- Joshua W Giles
- Hand and Upper Limb Centre, St. Joseph's Health Care, 268 Grosvenor Street, London, ON N6A 4V2, Canada. E-mail address for G.S. Athwal:
| | - Ryan M Degen
- Hand and Upper Limb Centre, St. Joseph's Health Care, 268 Grosvenor Street, London, ON N6A 4V2, Canada. E-mail address for G.S. Athwal:
| | - James A Johnson
- Hand and Upper Limb Centre, St. Joseph's Health Care, 268 Grosvenor Street, London, ON N6A 4V2, Canada. E-mail address for G.S. Athwal:
| | - George S Athwal
- Hand and Upper Limb Centre, St. Joseph's Health Care, 268 Grosvenor Street, London, ON N6A 4V2, Canada. E-mail address for G.S. Athwal:
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Degen RM, Giles JW, Johnson JA, Athwal GS. Remplissage versus latarjet for engaging Hill-Sachs defects without substantial glenoid bone loss: a biomechanical comparison. Clin Orthop Relat Res 2014; 472:2363-71. [PMID: 24385035 PMCID: PMC4079856 DOI: 10.1007/s11999-013-3436-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 12/13/2013] [Indexed: 01/31/2023]
Abstract
BACKGROUND Recurrent shoulder instability is commonly associated with Hill-Sachs defects. These defects may engage the glenoid rim, contributing to glenohumeral dislocation. Two treatment options to manage engaging Hill-Sachs defects are the remplissage procedure, which fills the defect with soft tissue, and the Latarjet procedure, which increases glenoid arc length. Little evidence exists to support one over the other. QUESTIONS/PURPOSES We performed a biomechanical comparison of the remplissage procedure to the traditional Latarjet coracoid transfer for management of engaging Hill-Sachs defects in terms of joint stiffness (resistance to anterior translation), ROM, and frequency of dislocation. METHODS Eight cadaveric specimens were tested on a shoulder instability simulator. Testing was performed with a 25% Hill-Sachs defect with an intact glenoid and after remplissage and Latarjet procedures. Joint stiffness, internal-external rotation ROM, and frequency of dislocation were assessed. Additionally, horizontal extension ROM was measured in composite glenohumeral abduction. RESULTS After remplissage, stiffness increased in adduction with neutral rotation (12.7 ± 3.7 N/mm) relative to the Hill-Sachs defect state (8.7 ± 3.3 N/mm; p = 0.016). The Latarjet procedure did not affect joint stiffness (p = 1.0). Internal-external rotation ROM was reduced in abduction after the Latarjet procedure (49° ± 14°) compared with the Hill-Sachs defect state (69° ± 17°) (p = 0.009). Horizontal extension was reduced after remplissage (16° ± 12°) relative to the Hill-Sachs defect state (34° ± 8°) (p = 0.038). With the numbers available, there was no difference between the procedures in terms of the frequency of dislocation after reconstruction: 84% of specimens (27 of 32 testing scenarios) stabilized after remplissage, while 94% of specimens (30 of 32 testing scenarios) stabilized after the Latarjet procedure. CONCLUSIONS Both procedures proved effective in reducing the frequency of dislocation in a 25% Hill-Sachs defect model, while neither procedure consistently altered joint stiffness. CLINICAL RELEVANCE In the treatment of shoulder instability with a humeral head bone defect and an intact glenoid rim, this study supports the use of both the remplissage and Latarjet procedures. Clinical studies and larger cadaveric studies powered to detect differences in instability rates are needed to evaluate these procedures in terms of their comparative efficacy at preventing dislocation, as any differences between them seem likely to be small.
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Affiliation(s)
- Ryan M. Degen
- Hand and Upper Limb Biomechanics Laboratory, St Joseph’s Health Care, 268 Grosvenor Street, London, Ontario N6A 4V2 Canada
| | - Joshua W. Giles
- Hand and Upper Limb Biomechanics Laboratory, St Joseph’s Health Care, 268 Grosvenor Street, London, Ontario N6A 4V2 Canada
| | - James A. Johnson
- Hand and Upper Limb Biomechanics Laboratory, St Joseph’s Health Care, 268 Grosvenor Street, London, Ontario N6A 4V2 Canada
| | - George S. Athwal
- Hand and Upper Limb Biomechanics Laboratory, St Joseph’s Health Care, 268 Grosvenor Street, London, Ontario N6A 4V2 Canada
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Puskas GJ, Giles JW, Degen RM, Johnson JA, Athwal GS. Humeral head reconstruction for Hill-Sachs defects: a biomechanical comparison of 2 fixation techniques for bone grafting. Arthroscopy 2014; 30:22-8. [PMID: 24215992 DOI: 10.1016/j.arthro.2013.09.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 09/10/2013] [Accepted: 09/10/2013] [Indexed: 02/02/2023]
Abstract
PURPOSE The purpose of this biomechanical study was to compare anterograde with retrograde screw fixation for allograft reconstruction of Hill-Sachs defects. METHODS In 8 pairs of fresh-frozen humeral heads, a 40% Hill-Sachs defect was created. The resultant wedge-shaped osteochondral fragment was used as allograft. For each technique, two 3.75-mm screws were used for fixation. To test the strength of fixation, a custom tool was used that would apply load to the graft. By use of a materials testing machine, a staircase cyclic loading protocol was performed (500 cycles at 10, 20, 30, and 40 N) and then load to failure. Graft displacement was measured by an optical tracking system. RESULTS For the 2 techniques, graft displacement increased with increasing load and increasing number of cycles up to a mean of 0.9 ± 0.42 mm for anterograde fixation and 1.1 ± 0.79 mm for retrograde fixation. This increase was significant within each technique across all 4 loading levels (P < .05). However, there were no significant differences in graft displacement between the 2 techniques at any loading level or number of cycles (P = .16 to P = .96). In addition, the load to failure between the anterograde and retrograde techniques (98.5 N and 95.6 N, respectively) was not significantly different (P = .706). CONCLUSIONS The initial fixation and failure strength of anterograde and retrograde graft fixation techniques for substantial Hill-Sachs defects do not significantly differ in a biomechanical cadaveric model. CLINICAL RELEVANCE This biomechanical study supports that in an engaging Hill-Sachs defect, both anterograde and retrograde screw fixation techniques can be used for fixation of humeral head allografts.
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Affiliation(s)
- Gabor J Puskas
- Orthopedic Department, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Joshua W Giles
- Hand and Upper Limb Centre, St. Joseph's Health Care, University of Western Ontario, London, Ontario, Canada
| | - Ryan M Degen
- Hand and Upper Limb Centre, St. Joseph's Health Care, University of Western Ontario, London, Ontario, Canada
| | - James A Johnson
- Hand and Upper Limb Centre, St. Joseph's Health Care, University of Western Ontario, London, Ontario, Canada
| | - George S Athwal
- Hand and Upper Limb Centre, St. Joseph's Health Care, University of Western Ontario, London, Ontario, Canada.
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Giles JW, Puskas GJ, Welsh MF, Johnson JA, Athwal GS. Suture anchor fixation of bony Bankart fractures: comparison of single-point with double-point "suture bridge" technique. Am J Sports Med 2013; 41:2624-31. [PMID: 24007759 DOI: 10.1177/0363546513501795] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND As an alternative to the standard single-point suture-anchor technique, a suture-bridge technique has been described for the treatment of bony Bankart fractures. There is, however, little evidence supporting one technique over the other. Purpose/ HYPOTHESIS To compare the failure strength, fixation stability, and loading mechanics of the 2 techniques for the fixation of bony Bankart fractures. We hypothesized that use of the double-point suture-bridge technique would result in superior strength and fixation stability because of the increased compression and contact area between the bony fragment and glenoid fracture site. STUDY DESIGN Controlled laboratory study. METHODS A total of 16 shoulders (8 pairs) were tested with an intact glenoid, after creation of a 15% bony Bankart fracture, and after fragment fixation using a single-point or suture-bridge technique. Paired specimens were randomly assigned to each technique. Cyclic progressive loading was applied via a materials testing machine to the glenoid concentrically and eccentrically according to a staircase protocol. Failure strength, fragment displacement, glenoid strain load transfer, and contact area were quantified. RESULTS No significant differences in failure strength were found between the single-point and suture-bridge techniques (mean strength, 74 ± 28 N vs 77 ± 56 N, respectively; P = .91). Additionally, no significant differences were found for glenoid load transfer (P ≥ .318) and glenohumeral joint contact (P = .357) between the 2 techniques. Centralized loading, however, produced significant differences in fragment displacement at 5, 150, and 200 N (P ≤ .045), with the single-point technique permitting greater fragment displacement in all cases (0.06-0.28 mm). Similarly, eccentric loading caused significantly greater fragment displacement with the single-point technique at ≥25 N compared with the suture-bridge technique (mean range, 0.38-0.63 mm vs 0.14-0.19 mm, respectively; .009 ≤ P ≤ .048). CONCLUSION Single-point and suture-bridge techniques for the fixation of bony Bankart fragments have equivalent failure strengths and load transfers. The suture-bridge technique does provide statistically greater initial fracture fragment stability; however, the clinical implications of this are presently unknown. CLINICAL RELEVANCE This study will aid in the selection of the optimal repair technique for bony Bankart fractures by providing important insights into the quality of initial fixation and ultimate strength.
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Affiliation(s)
- Joshua W Giles
- George S. Athwal, The Hand and Upper Limb Centre, St Joseph's Health Care London, 268 Grosvenor Street, London, ON, Canada, N6A 4L6.
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Abstract
Identification and treatment of the osseous lesions associated with complex shoulder instability remains challenging. Further biomechanical testing is required to delineate critical defect values and determine which treatments provide improved glenohumeral joint stability for the various defect sizes, while minimizing the associated complications.
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Affiliation(s)
- Ryan M Degen
- Division of Orthopedic Surgery, Western University, 1151 Richmond Street, London, ON N6A 3K7, Canada
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Degen RM, Giles JW, Boons HW, Litchfield RB, Johnson JA, Athwal GS. A biomechanical assessment of superior shoulder translation after reconstruction of anterior glenoid bone defects: The Latarjet procedure versus allograft reconstruction. Int J Shoulder Surg 2013; 7:7-13. [PMID: 23858289 PMCID: PMC3707337 DOI: 10.4103/0973-6042.109879] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Background: The coracoacromial ligament (CAL) is an important restraint to superior shoulder translation. The effect of CAL release on superior stability following the Latarjet is unknown; therefore, our purpose was to compare the effect of two Latarjet techniques and allograft reconstruction on superior instability. Materials and Methods: Eight cadaveric specimens were tested on a simulator. Superior translation was monitored following an axial force in various glenohumeral rotations (neutral, internal, and external) with and without muscle loading. Three intact CAL states were tested (intact specimen, 30% glenoid bone defect, and allograft reconstruction) and two CAL deficient states (classic Latarjet (classicLAT) and congruent-arc Latarjet (congruentLAT)). Results: In neutral without muscle loading, a significant increase in superior translation occurred with the classicLAT as compared to 30% defect (P = 0.046) and allograft conditions (P = 0.041). With muscle loading, the classicLAT (P = 0.005, 0.002) and the congruentLAT (P = 0.018, 0.021) had significantly greater superior translation compared to intact and allograft, respectively. In internal rotation, only loaded tests produced significant results; specifically, classicLAT increased translation compared to all intact CAL states (P < 0.05). In external rotation, only unloaded tests produced significant results with classicLAT and congruentLAT allowing greater translations than intact (P ≤ 0.028). For all simulations, the allograft was not significantly different than intact (P > 0.05) and no differences (P = 1.0) were found between classicLAT and congruentLAT. Discussion: In most simulations, CAL release with the Latarjet lead to increased superior humeral translation. Conclusion: The choice of technique for glenoid bone loss reconstruction has implications on the magnitude of superior humeral translation. This previously unknown effect requires further study to determine its clinical and kinematic outcomes.
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Affiliation(s)
- Ryan M Degen
- Department of Orthopedic Surgery, The University of Western Ontario, London, Ontario, Canada
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Giles JW, Johnson JA, Athwal GS. Authors' response. Am J Sports Med 2013; 41:NP32. [PMID: 23977675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Elkinson I, Giles JW, Boons HW, Faber KJ, Ferreira LM, Johnson JA, Athwal GS. The shoulder remplissage procedure for Hill-Sachs defects: does technique matter? J Shoulder Elbow Surg 2013; 22:835-41. [PMID: 23107147 DOI: 10.1016/j.jse.2012.08.015] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 07/20/2012] [Accepted: 08/16/2012] [Indexed: 02/01/2023]
Abstract
BACKGROUND This biomechanical study evaluated the effects of 3 remplissage techniques on shoulder stability and motion in a Hill-Sachs (HS) instability model. MATERIALS AND METHODS Cadaveric forequarters were tested on an active shoulder simulator. Three remplissage techniques were performed for 15% and 30% HS defects. Testing conditions included intact and 15% and 30% HS defects, and the 3 remplissage techniques: T1, anchors in the defect valley; T2, anchors in humeral head rim; and T3, anchors in valley with medial suture placement. Outcomes included stability, internal-external rotation range of motion (IE-ROM), and joint stiffness. RESULTS All remplissage techniques improved shoulder stability. In 15% HS defects tested in adduction, T3 significantly reduced IE-ROM (P = .037), whereas T1 and T2 did also (mean IE-ROM reductions: T1, 14°; T2, 11°; T3, 21°), but not to significance (P ≥ .088). In abduction, no significant reductions in IE-ROM occurred (P ≥ .060). In 30% HS defects tested in adduction (mean reduction IE-ROM: T1, 11°; T2, 19°; T3, 28°) and abduction (mean reduction: T1, 9°; T2, 15°; T3, 21°), all techniques significantly reduced IE-ROM (P ≤ .046). All techniques increased joint stiffness from 100% to 320% beyond the Bankart repair alone. A significant increase in joint stiffness was observed for T3 compared with the 30% HS group (P = .004), whereas T2 trended toward an increase (P = .078). There was no significant increase in joint stiffness with T1 (P = .249). CONCLUSIONS All remplissage techniques enhanced shoulder stability, restricted ROM, and increased joint stiffness. No significant differences were found between anchors placed in the valley (T1) vs those placed in the humeral head rim (T2). Medial suture placement (T3) resulted in the greatest joint stiffness values and mean restriction in motion.
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Affiliation(s)
- Iia Elkinson
- Hand and Upper Limb Centre, St. Joseph's Health Centre, The University of Western Ontario, London, ON, Canada
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Giles JW, Puskas G, Welsh M, Johnson JA, Athwal GS. Do the traditional and modified latarjet techniques produce equivalent reconstruction stability and strength? Am J Sports Med 2012; 40:2801-7. [PMID: 23024149 DOI: 10.1177/0363546512460835] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND The Latarjet procedure has been described as a reconstructive option for instability associated with substantial glenoid bone defects. A modification, termed the Congruent-Arc, is thought to improve glenoid reconstruction through better articular congruency and greater bone reconstitution. The strengths of these techniques, however, have not been reported. Purpose/ HYPOTHESIS To compare the fixation stability, strength, glenoid vault load transfer, and joint contact between the Classic and Congruent-Arc techniques. The authors hypothesized that the Classic Latarjet would exhibit inferior joint contact characteristics while having greater stability and strength and more normal glenoid vault strain. STUDY DESIGN Controlled laboratory study. METHODS Sixteen shoulder specimens (8 pairs) were tested by loading the glenohumeral joint with the glenoid intact, following creation of a 25% anterior bone defect, and after random assignment to the Classic or Congruent-Arc Latarjet techniques. Specimens were mounted to a testing apparatus that allowed concentric, centralized loading and loading 30° anterior on the glenoid rim. Cyclic loading (100 cycles at 1 Hz) was applied with a staircase protocol (50, 100, 150, and 200 N). Graft interface displacement and glenoid load transfer, quantified in terms of strain, were recorded during loading. Contact was quantified during 50-N loading using a thin pressure sensor. After cyclic loading, specimens were loaded to failure, defined as 5 mm of graft interface displacement. RESULTS The 30° loading ≥100 N resulted in significantly greater graft displacement (P < .004) in the Congruent-Arc group as compared with the Classic (mean displacement range, 0.9-2.6 vs 0.1-0.5 mm, respectively). Failure testing yielded a significantly (P = .010) greater ultimate strength for the Classic (557 N) as compared with the Congruent-Arc (392 N). Load-transfer measurements demonstrated that neither technique's glenoid vault strain values significantly differed from intact (P ≥ .076). Both techniques resulted in contact areas significantly less than intact (P < .035); however, the Congruent-Arc trended toward better contact characteristics (P = .074). CONCLUSION The Congruent-Arc results in significantly poorer fixation stability as compared with the Classic technique but did more closely reproduce intact joint contact, which may yield more favorable long-term outcomes. CLINICAL RELEVANCE Care must be taken in balancing the consideration of initial fixation stability and joint contact for the Congruent-Arc and Classic Latarjet, as these factors have opposing implications for each of the 2 reconstructions' outcomes.
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Affiliation(s)
- Joshua W Giles
- Bioengineering Research Laboratory, Hand and Upper Limb Centre, St Joseph's Health Centre, Ontario, Canada
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Elkinson I, Giles JW, Faber KJ, Boons HW, Ferreira LM, Johnson JA, Athwal GS. The effect of the remplissage procedure on shoulder stability and range of motion: an in vitro biomechanical assessment. J Bone Joint Surg Am 2012; 94:1003-12. [PMID: 22637206 DOI: 10.2106/jbjs.j.01956] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND The remplissage procedure may be performed as an adjunct to Bankart repair to treat recurrent glenohumeral dislocation associated with an engaging Hill-Sachs humeral head defect. The purpose of this in vitro biomechanical study was to examine the effects of the remplissage procedure on glenohumeral joint motion and stability. METHODS Cadaveric shoulders (n = 8) were mounted on a biomechanical testing apparatus that applies simulated loads to the rotator cuff and the anterior, middle, and posterior heads of the deltoid muscle. Testing was performed with the shoulder intact, after creation of the Bankart lesion, and after repair of the Bankart lesion. In addition, testing was performed after Bankart repair with and without remplissage in shoulders with 15% and 30% Hill-Sachs defects. Shoulder motion and glenohumeral translation were recorded with an optical tracking system. Outcomes measured included stability (joint stiffness and defect engagement) and internal-external glenohumeral rotational motion in adduction and in 90° of composite shoulder abduction. RESULTS In specimens with a 15% Hill-Sachs defect, Bankart repair combined with remplissage resulted in a significant reduction in internal-external range of motion in adduction (15.1° ± 11.1°, p = 0.039), but not in abduction (7.7° ± 9.9, p = 0.38), compared with the intact condition. In specimens with a 30% Hill-Sachs defect, repair that included remplissage also significantly reduced internal-external range of motion in adduction (14.5° ± 11.3°, p = 0.049) but not in abduction (6.2° ± 9.3°, p = 0.60). In specimens with a 15% Hill-Sachs defect, addition of remplissage significantly increased joint stiffness compared with isolated Bankart repair (p = 0.038), with the stiffness trending toward surpassing the level in the intact condition (p = 0.060). In specimens with a 30% Hill-Sachs defect, addition of remplissage restored joint stiffness to approximately normal (p = 0.41 compared with the intact condition). All of the specimens with a 30% Hill-Sachs defect engaged and dislocated after Bankart repair alone. The addition of remplissage was effective in preventing engagement and dislocation in all specimens. None of the specimens with a 15% Hill-Sachs defect engaged or dislocated after Bankart repair. CONCLUSIONS In this experimental model, addition of remplissage provided little additional benefit to a Bankart repair in specimens with a 15% Hill-Sachs defect, and it also reduced specific shoulder motions. However, Bankart repair alone was ineffective in preventing engagement and recurrent dislocation in specimens with a 30% Hill-Sachs defect. The addition of remplissage to the Bankart repair in these specimens prevented engagement and enhanced stability, although at the expense of some reduction in shoulder motion.
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Affiliation(s)
- Ilia Elkinson
- H.U.L.C. Bioengineering Research Laboratory, University of Western Ontario, London, Ontario, Canada
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Armitage MS, Elkinson I, Giles JW, Athwal GS. An anatomic, computed tomographic assessment of the coracoid process with special reference to the congruent-arc latarjet procedure. Arthroscopy 2011; 27:1485-9. [PMID: 21924857 DOI: 10.1016/j.arthro.2011.06.020] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 06/12/2011] [Accepted: 06/14/2011] [Indexed: 02/02/2023]
Abstract
PURPOSE The purpose of this study was to determine the dimensions of the coracoid and to compare the radius of curvature (ROC) of the intact glenoid to the ROC of the coracoid undersurface, as oriented in the congruent-arc Latarjet procedure. The ROC of the coracoid undersurface was also compared with various glenoid bone loss scenarios. METHODS Thirty-four computed tomography-based 3-dimensional models of the shoulder were examined by use of commercially available software. The mean dimensions of the coracoid were determined, and the ROC was calculated for the coracoid undersurface, the intact glenoid, and 20%, 35%, and 50% anterior glenoid bone loss scenarios. Intra-rater and inter-rater statistics were calculated. RESULTS The mean length, width, and thickness of the coracoid were 16.8 mm (SD, 2.5 mm), 15.0 mm (SD, 2.2 mm), and 10.5 mm (SD, 1.7 mm), respectively. The mean ROC values were 13.6 mm (SD, 3.4 mm) for the coracoid, 13.8 mm (SD, 2.1 mm) for the intact glenoid, 27.6 mm (SD, 5.3 mm) for 20% anterior glenoid bone loss, 30.5 mm (SD, 5.2 mm) for 35% bone loss, and 33.3 mm (SD, 5.2 mm) for 50% bone loss. The coracoid ROC was not significantly different from the intact glenoid (P = .75); however, it was significantly less (P < .01) when compared with all glenoid bone loss scenarios. Intra-rater reliability and inter-rater reliability were good or excellent. A coracoid oriented in the congruent-arc manner can reconstitute a significantly greater glenoid bone defect than a coracoid oriented in the classic manner (P < .001). CONCLUSIONS This image-based anatomic study found that the ROC of the coracoid undersurface matches the ROC of the intact anterior glenoid articular margin. In conditions with anterior glenoid bony deficiency, the radii of curvature differ significantly at the graft-native glenoid interface; however, the coracoid graft placed in the congruent-arc manner reconstitutes the ROC of the missing anterior glenoid rim. In addition, orienting the coracoid in the congruent-arc manner can reconstitute a greater glenoid bone defect than a coracoid placed in the original manner as described by Latarjet. CLINICAL RELEVANCE The congruent-arc Latarjet procedure, a modification of the original procedure, is truly congruent in relation to the intact anterior glenoid rim. In addition, the congruent-arc modification can reconstitute a greater glenoid bone defect when compared with the original Latarjet procedure.
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Affiliation(s)
- Marshal S Armitage
- The Hand and Upper Limb Centre, St. Joseph's Health Care, University of Western Ontario, London, Ontario, Canada
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Giles JW, Boons HW, Ferreira LM, Johnson JA, Athwal GS. The effect of the conjoined tendon of the short head of the biceps and coracobrachialis on shoulder stability and kinematics during in-vitro simulation. J Biomech 2011; 44:1192-5. [PMID: 21377681 DOI: 10.1016/j.jbiomech.2011.02.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 01/03/2011] [Accepted: 02/14/2011] [Indexed: 11/26/2022]
Abstract
The kinematics and stability of the shoulder during in-vitro simulation are affected by the muscles chosen for simulation and their loads. Existing simulators have commonly actuated the rotator cuff and deltoids; however, the contribution of secondary muscles, such as those which form the conjoined tendon, are not well understood. The conjoined tendon consists of the origins of the short head of the biceps and coracobrachialis (SH&C), and is thought to produce an anterior stabilizing effect. This study investigated the effect of SH&C tension at four loading levels: 0, 5, 10, 15N. Our primary outcome variable was glenohumeral stiffness for anterior loading but internal/external rotation and extension ranges of motion were also measured. Four joint configurations were tested: adduction and 90° combined abduction, each in neutral and maximal external rotation. Increasing SH&C load resulted in a significant trend of increased glenohumeral stiffness across the average of all joint configurations (p=0.008). In abduction, neutral rotation differences were found between the stiffness at 10 and 15N compared to 0N (p=0.038 and 0.043, respectively); however, no differences were found for the three other joint configurations. There was a tendency for a decrease in the range of shoulder extension with increasing SH&C load, but this did not achieve significance (p=0.065). These findings demonstrate that the SH&C provides a stabilizing barrier effect, but only in configurations when it wraps directly anterior to the humeral head. Thus SH&C loading is likely critical to in-vitro simulation due to its effect on joint stability and kinematics.
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Affiliation(s)
- Joshua W Giles
- Bioengineering Research Laboratory, The Hand and Upper Limb Centre, St. Joseph's Health Care London, London, Ontario, Canada
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Sear JW, Giles JW, Howard-Alpe G, Foëx P. Perioperative beta-blockade, 2008: what does POISE tell us, and was our earlier caution justified? Br J Anaesth 2008; 101:135-8. [PMID: 18614596 DOI: 10.1093/bja/aen194] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Giles JW, Bankman IN, Sova RM, Morgan TR, Duncan DD, Millard JA, Green WJ, Marcotte FJ. Lidar system model for use with path obscurants and experimental validation. Appl Opt 2008; 47:4085-4093. [PMID: 18670566 DOI: 10.1364/ao.47.004085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
When lidar pulses travel through a short path that includes a relatively high concentration of aerosols, scattering phenomena can alter the power and temporal properties of the pulses significantly, causing undesirable effects in the received pulse. In many applications the design of the lidar transmitter and receiver must consider adverse environmental aerosol conditions to ensure the desired performance. We present an analytical model of lidar system operation when the optical path includes aerosols for use in support of instrument design, simulations, and system evaluation. The model considers an optical path terminated with a solid object, although it can also be applied, with minor modifications, to cases where the expected backscatter occurs from nonsolid objects. The optical path aerosols are characterized by their attenuation and backscatter coefficients derived by the Mie theory from the concentration and particle size distribution of the aerosol. Other inputs include the lidar system parameters and instrument response function, and the model output is the time-resolved received pulse. The model is demonstrated and experimentally validated with military fog oil smoke for short ranges (several meters). The results are obtained with a lidar system operating at a wavelength of 0.905 microm within and outside the aerosol. The model goodness of fit is evaluated using the statistical coefficient of determination whose value ranged from 0.88 to 0.99 in this study.
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Affiliation(s)
- J W Giles
- The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, USA.
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Giles JW, Sear JW, Foëx P. Effect of chronic β-blockade on peri-operative outcome in patients undergoing non-cardiac surgery: an analysis of observational and case control studies*. Anaesthesia 2004; 59:574-83. [PMID: 15144298 DOI: 10.1111/j.1365-2044.2004.03706.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Little is known about the effect of chronic beta-adrenoceptor antagonist therapy during the peri-operative period in patients undergoing non-cardiac surgery. We conducted a literature review to identify studies examining the relationship between chronic therapy and adverse peri-operative outcome. Eighteen studies were identified in which it was possible to ascertain the incidence of adverse cardiac outcomes in those patients who were and were not receiving chronic beta-blocker therapy. None of the studies demonstrated a protective effect of chronic beta-blockade. The results of these studies were then combined and a cumulative odds ratio calculated for the likelihood of myocardial infarction, cardiac death and major cardiac complications. Patients receiving chronic beta-blocker therapy were more likely to suffer a myocardial infarction (p < 0.05). These findings differ from the published effects of acute beta-blockade. Reasons for this discrepancy are considered.
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Affiliation(s)
- J W Giles
- Nuffield Department of Anaesthetics, University of Oxford, John Radcliffe Hospital, Headley Way, Headington, Oxford, UK.
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Rose RC, Grossman AM, Giles JW. Infective endocarditis due to the CDC group M6 bacillus. J Tenn Med Assoc 1990; 83:603-4. [PMID: 2287169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Although staphylococcal endocarditis has occasionally been associated with a TTP-like syndrome, a similar syndrome has not been reported with endocarditis due to aerobic gram-negative rods. We report a case of subacute bacterial endocarditis with a thrombocytopenic syndrome that at first resembled TTP which was due to an unusual gram-negative rod. This case emphasizes the need for repeated examination of the bacteremic patient to detect the changing murmurs of endocarditis.
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Affiliation(s)
- R C Rose
- Department of Medicine, St. Mary's Medical Center, Knoxville, TN
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Abstract
The photodecomposition of aqueous solutions of 2,2-bis (p-chlorophenyl) acetic acid (DDA) was slow in sunlight and rapid in the laboratory, producing p,p'-dichlorobenzophenone (DCB), p-chlorobenzaldehyde, p-chlorophenol, and several unidentified polar products. p,p'-Dichlorobenzilic acid, and p,p'-dichlorobenzhydrol gave rise to the same photoproducts, while bis-(p-chlorophenyl) methane (DDM) and chlorogenzilate were converted only to DCB. DCB and p-chlorogenzaldehyde proved to be resistant to photodegradation but gradually produced p-chlorobenzoic acid which, in turn, formed p-hydroxybenzoic and benzoic acids, probably the last environmentally detectable links in the long chain of DDT degradation to CO2 and water. High pressure liquid chromatography (HPLC) proved to be ideal for separating and quantitating the parent compounds and their photoproducts directly from the aqueous photolysates or from methanol solutions of the isolates and standards.
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Giles JW, Smith IM. The study of a rubella outbreak. J Iowa Med Soc 1972; 62:238-41. [PMID: 5025119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Giles JW. Stronger laws needed against illegal dental practice. Oral Hyg 1966; 56:27-32. [PMID: 5218529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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