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Genter J, Croci E, Müller AM, Mündermann A, Baumgartner D. Influence of Critical Shoulder Angle and Rotator Cuff Tear Type on Load-Induced Glenohumeral Biomechanics: A Sawbone Simulator Study. Appl Bionics Biomech 2024; 2024:4624007. [PMID: 38983835 PMCID: PMC11233187 DOI: 10.1155/2024/4624007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 05/15/2024] [Accepted: 06/14/2024] [Indexed: 07/11/2024] Open
Abstract
Glenohumeral (GH) biomechanics after rotator cuff (RC) tears are not fully understood. The purpose of our study was to determine if the critical shoulder angle (CSA), type of RC tears, and level of weight bearing increase GH translation, instability based on the instability ratio, muscle forces and joint reaction force (JRF), and shifts the center of force (CoF) superiorly. A GH simulator with muscle-mimicking cable systems was used to simulate 30° abduction in the scapular plane. A Sawbone humerus and five specimen-specific scapular anthropometries were used to test six types of RC tears, three weight-bearing loads, and the native and adjusted (to different CSAs) deltoid origin sites. Linear mixed effects models (CSA, RC tear type, and weight bearing) with random effects (specimen and sex) were used to assess differences in GH biomechanics. With increasing CSA, GH translation increased, JRF decreased, and the CoF position was more inferior. RC tears did not significantly alter GH translation but shifted the CoF position superiorly, close to where glenoid erosion occurs in patients with RC tears with secondary osteoarthritis. Weight bearing significantly increased GH translation and JRF. RC and deltoid muscle forces increased with the presence of RC tears and increased weight bearing. The remaining RC muscles of intact tendons compensated for the torn RC tendons but not for the altered CoF position. GH translation remained comparable to shoulders with intact RC. These findings highlight the importance of early detection, clinical management, and targeted rehabilitation strategies for patients with RC tears.
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Affiliation(s)
- Jeremy Genter
- IMES Institute of Mechanical Systems Zurich University of Applied Sciences ZHAW, Winterthur, Switzerland
- Department of Biomedical Engineering University of Basel, Basel, Switzerland
- Department of Orthopaedics and Traumatology University Hospital Basel, Basel, Switzerland
| | - Eleonora Croci
- Department of Biomedical Engineering University of Basel, Basel, Switzerland
- Department of Orthopaedics and Traumatology University Hospital Basel, Basel, Switzerland
| | - Andreas M Müller
- Department of Orthopaedics and Traumatology University Hospital Basel, Basel, Switzerland
| | - Annegret Mündermann
- Department of Biomedical Engineering University of Basel, Basel, Switzerland
- Department of Orthopaedics and Traumatology University Hospital Basel, Basel, Switzerland
- Department of Clinical Research University of Basel, Basel, Switzerland
| | - Daniel Baumgartner
- IMES Institute of Mechanical Systems Zurich University of Applied Sciences ZHAW, Winterthur, Switzerland
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Genter J, Croci E, Oberreiter B, Eckers F, Bühler D, Gascho D, Müller AM, Mündermann A, Baumgartner D. The influence of rotator cuff tear type and weight bearing on shoulder biomechanics in an ex vivo simulator experiment. J Biomech 2024; 166:112055. [PMID: 38522362 DOI: 10.1016/j.jbiomech.2024.112055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 02/16/2024] [Accepted: 03/18/2024] [Indexed: 03/26/2024]
Abstract
Glenohumeral biomechanics after rotator cuff (RC) tears have not been fully elucidated. This study aimed to investigate the muscle compensatory mechanism in weight-bearing shoulders with RC tears and asses the induced pathomechanics (i.e., glenohumeral translation, joint instability, center of force (CoF), joint reaction force). An experimental, glenohumeral simulator with muscle-mimicking cable system was used to simulate 30° scaption motion. Eight fresh-frozen shoulders were prepared and mounted in the simulator. Specimen-specific scapular anthropometry was used to test six RC tear types, with intact RC serving as the control, and three weight-bearing loads, with the non-weight-bearing condition serving as the control. Glenohumeral translation was calculated using instantaneous helical axis. CoF, muscle forces, and joint reaction forces were measured using force sensors integrated into the simulator. Linear mixed effects models (RC tear type and weight-bearing) with random effects (specimen and sex) were used to assess differences in glenohumeral biomechanics. RC tears did not change the glenohumeral translation (p > 0.05) but shifted the CoF superiorly (p ≤ 0.005). Glenohumeral translation and joint reaction forces increased with increasing weight bearing (p < 0.001). RC and deltoid muscle forces increased with the presence of RC tears (p ≤ 0.046) and increased weight bearing (p ≤ 0.042). The synergistic muscles compensated for the torn RC tendons, and the glenohumeral translation remained comparable to that for the intact RC tendons. However, in RC tears, the more superior CoF was close to where glenoid erosion occurs in RC tear patients with secondary osteoarthritis. These findings underscore the importance of early detection and precise management of RC tears.
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Affiliation(s)
- Jeremy Genter
- IMES Institute of Mechanical Systems, Zurich University of Applied Sciences ZHAW, Winterthur, Switzerland; Department of Biomedical Engineering, University of Basel, Basel, Switzerland; Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland.
| | - Eleonora Croci
- Department of Biomedical Engineering, University of Basel, Basel, Switzerland; Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland
| | - Birgit Oberreiter
- Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland
| | - Franziska Eckers
- Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland
| | - Dominik Bühler
- Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland
| | - Dominic Gascho
- Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Zurich, Zurich, Switzerland
| | - Andreas M Müller
- Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland
| | - Annegret Mündermann
- Department of Biomedical Engineering, University of Basel, Basel, Switzerland; Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland; Department of Clinical Research, University of Basel, Basel, Switzerland
| | - Daniel Baumgartner
- IMES Institute of Mechanical Systems, Zurich University of Applied Sciences ZHAW, Winterthur, Switzerland
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Ardebol J, Pak T, Kiliç AĪ, Hwang S, Menendez ME, Denard PJ. Secondary Rotator Cuff Insufficiency After Anatomic Total Shoulder Arthroplasty. JBJS Rev 2023; 11:01874474-202309000-00005. [PMID: 37729463 DOI: 10.2106/jbjs.rvw.23.00099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
» Secondary rotator cuff insufficiency is a challenging complication after anatomic total shoulder arthroplasty.» Acute tears may be amenable to open or arthroscopic repair in some instances.» Chronic attritional tears are best managed with revision to reverse shoulder arthroplasty, especially in the elderly.» Increased glenoid inclination, larger critical shoulder angle, oversized humeral components, thicker glenoid components, and rotator cuff muscle fatty infiltration have all shown to contribute to tear risk.
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Affiliation(s)
| | | | - Ali Īhsan Kiliç
- Oregon Shoulder Institute, Medford, Oregon
- Izmir Bakircay University, Izmir, Turkey
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Mangasah H, Aminata IW. Three-dimensional morphometric analysis of glenoid in the Indonesian population and its clinical significance. J Orthop 2023; 37:27-33. [PMID: 36974093 PMCID: PMC10039108 DOI: 10.1016/j.jor.2023.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 11/29/2022] [Accepted: 02/08/2023] [Indexed: 02/11/2023] Open
Abstract
Background Understanding glenoid morphometry is important in shoulder prosthetic replacement surgery. In total and reverse shoulder arthroplasty, the size of the implants has to be determined according to the morphometry of the shoulder. However, there has been no known data on glenoid morphometry in the Indonesian population. Methods Seventy-four computed tomography scans of asymptomatic shoulders were obtained from the medical databases of a third referral hospital in Jakarta. Mimics Research 21.0 was used to reconstruct 3D models of the scapula from the DICOM files. The morphometry parameters included were glenoid fossa height (GFH), maximum glenoid fossa width (MGW), glenoid width at center of the glenoid fossa (CGW), vertical distance between maximum width and center (VDMC), glenoid version angle (GVA), glenoid inclination (GI), glenopolar angle (GPA), glenoid vault depth (GVD), coracoid length (CL), coracoid midpoint length (CML), coracoid tip height (CTH) and width (CTW), and coracoid midpoint height (CMH) and width (CMW). Results Our study found the average Indonesian GFH was 30.24 mm, the MGW was 24.03 mm, the CGW was 22.46 mm, the VDMC was 3.67 mm, the GPA was 42.76°, the GVD 18.8 mm, the GVA was 2.39° retroverted, the GI was 3.15° superiorly inclined, the CL was 37.76 mm, the CML was 18.89 mm, the CTW was 13.31 mm, the CTH was 8.52 mm, the CMW was 14.21 mm, and the CMH was 10.46 mm. All parameters except VDMC, GVA, and GI showed significant differences between male and female subjects Meanwhile, there was no significant difference in dimension and orientation of the glenoid and coracoid between the right and left shoulder. Conclusion Our study showed a lower value of MGW, GFH, and GVD compared to other Asian ethnicities. These results may be helpful in designing smaller prostheses suitable for Indonesian glenoids.
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Affiliation(s)
- Holong Mangasah
- Department of Orthopaedics and Traumatology, Fatmawati General Hospital, Faculty of Medicine Universitas Indonesia, Jakarta, Indonesia
| | - Iman Widya Aminata
- Department of Orthopaedics and Traumatology, Fatmawati General Hospital, Faculty of Medicine Universitas Indonesia, Jakarta, Indonesia
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Hsu CP, Wu CT, Chen CY, Lin SC, Hsu KY. Difference analysis of the glenoid centerline between 3D preoperative planning and 3D printed prosthesis manipulation in total shoulder arthroplasty. Arch Orthop Trauma Surg 2022:10.1007/s00402-022-04688-8. [PMID: 36445496 DOI: 10.1007/s00402-022-04688-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 10/30/2022] [Indexed: 12/02/2022]
Abstract
INTRODUCTION Excessive version and inclination of the glenoid component during total shoulder arthroplasty can lead to glenohumeral instability, early loosening, and even failure. The orientation and position of the central pin determine the version and inclination of the glenoid component. The purpose of this study was to compare the differences in centerline position and orientation obtained using "3D preoperative planning based on the best-fit method for glenoid elements" and the surgeon's manipulation. MATERIALS AND METHODS Twenty-nine CT images of glenohumeral osteoarthritis of the shoulder were reconstructed into a 3D model, and a 3D printer was used to create an in vitro model for the surgeon to drill the center pin. The 3D shoulder model was also used for 3D preoperative planning (3DPP) using the best-fit method for glenoid elements. The in vitro model was scanned and the version, inclination and center position were measured to compare with the 3DPP results. RESULTS The respective mean inclinations (versions) of the surgeon and 3DPP were -2.63° ± 6.60 (2.87° ± 5.97) and -1.96° ± 4.24 (-3.21° ± 4.00), respectively. There was no significant difference in the inclination and version of the surgeon and 3DPP. For surgeons, the probability of the inclination and version being greater than 10° was 13.8% (4/29) and 10.3% (3/29), respectively. Compared to the 3DPP results, the surgeon's center position was shifted down an average of 1.63 mm. There was a significant difference in the center position of the surgeon and 3DPP (p < 0.05). CONCLUSION The central pin drilled by surgeons using general instruments was significantly lower than those defined using 3D preoperative planning and standard central definitions. 3D preoperative planning prevents the version and inclination of the centerline from exceeding safe values (± 10°).
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Affiliation(s)
- Chi-Pin Hsu
- High Speed 3D Printing Research Center, National Taiwan University of Science and Technology, Taipei, Taiwan
| | - Chen-Te Wu
- Department of Medical Imaging and Intervention Radiology, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Chao-Yu Chen
- Department of Orthopaedic Surgery Division of Sports Medicine and Musculoskeletal Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
| | - Shang-Chih Lin
- Graduate Institute of Biomedical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan
| | - Kuo-Yao Hsu
- Department of Orthopaedic Surgery Division of Sports Medicine and Musculoskeletal Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
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Glasson JM, van Rooij F, Nover L, Saffarini M, Kany J. The Y plane is a reliable CT-based reference for glenoid component positioning in shoulder arthroplasty. J Exp Orthop 2022; 9:46. [PMID: 35583701 PMCID: PMC9117575 DOI: 10.1186/s40634-022-00481-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 05/05/2022] [Indexed: 11/18/2022] Open
Abstract
Purpose To determine the reliability of anatomic references for mediolateral component positioning in shoulder arthroplasty. Materials and methods The computed tomography scans of 86 shoulders free of arthritic or anatomic deformities were studied. Two surgeons independently digitized a series of points, including the intersection of the 3 bone branches of the scapular spine (Y), the center of the glenoid surface (G), the most medial point of the scapula (MS), the cortical convergence (CC) of the anterior and posterior margins of the glenoid, the base of the coracoid (BC), the anterior (HA) and posterior (HP) margins of the subchondral bone. Results The mean mediolateral distances between G and Y, BC, CC were respectively − 19.6 mm, − 1.5 mm, and − 36.8 mm. The consistency of anatomic landmarks was greatest for Y (standard deviation (SD) =2.3 mm; interquartile range (IQR) =3 mm), compared to BC (SD = 4.6 mm; IQR = 7 mm), and CC (SD = 6.6 mm; IQR = 8 mm). The repeatability of anatomic landmarks was excellent for all measurements. The mean ratios (relative to humeral head size) of distances between G and Y, BC, CC were respectively − 0.45, − 0.04, and − 0.85. The consistency of ratios was greatest for Y (SD = 0.05; IQR = 0.06), compared to BC (SD = 0.11; IQR = 0.14), and CC (SD = 0.13; IQR = 0.17). The repeatability of ratios was excellent for Y and BC, while it was good for CC. Conclusions The Y-plane is a reliable reference for glenoid component positioning in shoulder arthroplasty, with a consistent distance from the center of the glenoid surface, and could therefore be suitable for preoperative planning. Study design Level III, comparative anatomic study.
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Affiliation(s)
- Jean-Marc Glasson
- Clinique Saint François, ELSAN, 22 Avenue Marcel Lemoine, 36000, Châteauroux, France.,Clinique du Parc Imperial, 28 Boulevard du Tzarewitch, 06000, Nice, France
| | | | - Luca Nover
- ReSurg SA, Rue Saint Jean 22, 1260, Nyon, Switzerland
| | - Mo Saffarini
- ReSurg SA, Rue Saint Jean 22, 1260, Nyon, Switzerland
| | - Jean Kany
- Clinique de l'Union, Ramsay Santé, Boulevard de Ratalens, 31240, Saint-Jean, France
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Wynell-Mayow W, Chong CC, Musbahi O, Ibrahim E. A lower critical coracoid process angle is associated with type-B osteoarthritis: a radiological study of normal and diseased shoulders. JSES Int 2021; 6:447-453. [PMID: 35572451 PMCID: PMC9091782 DOI: 10.1016/j.jseint.2021.10.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Background Degenerative rotator cuff tears and osteoarthritis (OA) are associated with differences in coronal plane scapular morphology, with particular focus on the effect of the critical shoulder angle (CSA) on shoulder biomechanics. The effect, if any, of axial plane scapular morphology is less well established. We have noticed wide disparity of axial coracoid tip position in relation to the face of the glenoid and sought to investigate the significance of this through measurement of the critical coracoid process angle (CCPA), which incorporates coracoid tip position and glenoid version. Methods CCPA, CSA, and glenoid retroversion were measured by three independent reviewers from the cross-sectional two-dimensional computed tomography (CT) and magnetic resonance imaging of 160 patients in four equal and matched case-control groups: (1) a control group of patients with a radiologically normal shoulder and no history of shoulder symptoms who had a CT thorax for another reason, (2) patients with primary OA with Walch type-A glenoid wear pattern on CT scan, (3) patients with type-B glenoid primary OA, and (4) patients with magnetic resonance imaging–proven atraumatic tears of the posterosuperior rotator cuff. Results Interobserver agreement was excellent for all measured parameters. The median CCPA was significantly lower in the type-B OA group (9.3˚) than that in controls (18.7˚), but not significantly different in the other study groups. There was a trend toward greater glenoid retroversion in the type-B OA group, but receiver operating characteristic curve analysis demonstrated the CCPA to be by far the most powerful discriminator for type-B OA. The optimal cutoff value was calculated for the CCPA at 14.3˚ with a sensitivity of 93% and specificity of 90% for type-B OA. Compared with controls, the CSA was significantly higher in the rotator cuff tear group and lower in both OA groups, but did not differentiate between type-A and type-B OA. Conclusion Combined with a lower CSA, a lower CCPA (<14.3˚) is strongly predictive of type-B glenoid OA. The authors propose a simple model of pectoralis major biomechanics to explain the effect of this axial plane anatomical variation, which requires further investigation.
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Affiliation(s)
- William Wynell-Mayow
- West Middlesex University Hospital, Chelsea and Westminster NHS Foundation Trust, Isleworth, Middlesex
- Corresponding author: William Wynell-Mayow, MRCS, Flat 317, West Block, Forum Magnum Square, London, SE1 7GL.
| | - Chung Chi Chong
- West Middlesex University Hospital, Chelsea and Westminster NHS Foundation Trust, Isleworth, Middlesex
| | - Omar Musbahi
- West Middlesex University Hospital, Chelsea and Westminster NHS Foundation Trust, Isleworth, Middlesex
- MSk Lab, White City Campus, Imperial College London, London
| | - Edward Ibrahim
- West Middlesex University Hospital, Chelsea and Westminster NHS Foundation Trust, Isleworth, Middlesex
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Serrano N, Kissling M, Krafft H, Link K, Ullrich O, Buck FM, Mathews S, Serowy S, Gascho D, Grüninger P, Fornaciari P, Bouaicha S, Müller-Gerbl M, Rühli FJ, Eppler E. CT-based and morphological comparison of glenoid inclination and version angles and mineralisation distribution in human body donors. BMC Musculoskelet Disord 2021; 22:849. [PMID: 34610804 PMCID: PMC8493698 DOI: 10.1186/s12891-021-04660-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 08/25/2021] [Indexed: 11/11/2022] Open
Abstract
Background For optimal prosthetic anchoring in omarthritis surgery, a differentiated knowledge on the mineralisation distribution of the glenoid is important. However, database on the mineralisation of diseased joints and potential relations with glenoid angles is limited. Methods Shoulder specimens from ten female and nine male body donors with an average age of 81.5 years were investigated. Using 3D-CT-multiplanar reconstruction, glenoid inclination and retroversion angles were measured, and osteoarthritis signs graded. Computed Tomography-Osteoabsorptiometry (CT-OAM) is an established method to determine the subchondral bone plate mineralisation, which has been demonstrated to serve as marker for the long-term loading history of joints. Based on mineralisation distribution mappings of healthy shoulder specimens, physiological and different CT-OAM patterns were compared with glenoid angles. Results Osteoarthritis grades were 0-I in 52.6% of the 3D-CT-scans, grades II-III in 34.3%, and grade IV in 13.2%, with in females twice as frequently (45%) higher grades (III, IV) than in males (22%, III). The average inclination angle was 8.4°. In glenoids with inclination ≤10°, mineralisation was predominantly centrally distributed and tended to shift more cranially when the inclination raised to > 10°. The average retroversion angle was − 5.2°. A dorsally enhanced mineralisation distribution was found in glenoids with versions from − 15.9° to + 1.7°. A predominantly centrally distributed mineralisation was accompanied by a narrower range of retroversion angles between − 10° to − 0.4°. Conclusions This study is one of the first to combine CT-based analyses of glenoid angles and mineralisation distribution in an elderly population. The data set is limited to 19 individuals, however, indicates that superior inclination between 0° and 10°-15°, and dorsal version ranging between − 9° to − 3° may be predominantly associated with anterior and central mineralisation patterns previously classified as physiological for the shoulder joint. The current basic research findings may serve as basic data set for future studies addressing the glenoid geometry for treatment planning in omarthritis. Supplementary Information The online version contains supplementary material available at 10.1186/s12891-021-04660-4.
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Affiliation(s)
- Nabil Serrano
- Institute of Evolutionary Medicine (IEM), University of Zurich, Zurich, Switzerland
| | - Marc Kissling
- Institute of Anatomy, University of Bern, Bern, Switzerland
| | - Hannah Krafft
- Division of Gross Anatomy, Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Karl Link
- Division of Gross Anatomy, Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Anatomy, University of Fribourg, Fribourg, Switzerland
| | - Oliver Ullrich
- Division of Gross Anatomy, Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Florian M Buck
- Medical Radiology Institute, Schulthess Clinic, Zurich, Switzerland
| | - Sandra Mathews
- Institute of Evolutionary Medicine (IEM), University of Zurich, Zurich, Switzerland
| | - Steffen Serowy
- Clinic of Neuroradiology, University Hospital of Magdeburg, Magdeburg, Germany
| | - Dominic Gascho
- Institute of Forensic Medicine, University of Zurich, Zurich, Switzerland
| | | | - Paolo Fornaciari
- Department of Orthopaedics, Balgrist University Hospital, Zurich, Switzerland.,Department of Orthopaedic Surgery and Traumatology, University Hospital Fribourg, Fribourg, Switzerland
| | - Samy Bouaicha
- Department of Orthopaedics, Balgrist University Hospital, Zurich, Switzerland
| | - Magdalena Müller-Gerbl
- Musculoskeletal Research, Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Frank-Jakobus Rühli
- Institute of Evolutionary Medicine (IEM), University of Zurich, Zurich, Switzerland.
| | - Elisabeth Eppler
- Musculoskeletal Research, Department of Biomedicine, University of Basel, Basel, Switzerland. .,Clinic of Neuroradiology, University Hospital of Magdeburg, Magdeburg, Germany. .,Institute of Anatomy, University of Bern, Bern, Switzerland.
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