18 results on '"Christian Gerber"'
Search Results
2. Posterior stability of the shoulder depends on acromial anatomy: a biomechanical study of 3D surface models
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Bettina Hochreiter, Silvan Beeler, Simon Hofstede, Bastian Sigrist, Jess G. Snedeker, and Christian Gerber
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Posterior shoulder instability ,Humeral head subluxation ,Static posterior ,Walch B1 ,Acromion ,Shoulder ,Orthopedic surgery ,RD701-811 - Abstract
Abstract Purpose Primary glenohumeral osteoarthritis is commonly associated with static posterior subluxation of the humeral head. Scapulae with static/dynamic posterior instability feature a superiorly and horizontally oriented acromion. We investigated whether the acromion acts as a restraint to posterior humeral translation. Methods Five three‐dimensional (3D) printed scapula models were biomechanically tested. A statistical shape mean model (SSMM) of the normal scapula of 40 asymptomatic shoulders was fabricated. Next, a SSMM of scapular anatomy associated with posterior subluxation was generated using data of 20 scapulae (“B1”). This model was then used to generate three models of surgical correction: glenoid version, acromial orientation, and acromial and glenoid orientation. With the joint axially loaded (100N) and the humerus stabilized, an anterior translation force was applied to the scapula in 35°, 60° and 75° of glenohumeral flexion. Translation (mm) was measured. Results In the normal scapula, the humerus translates significantly less to contact with the acromion compared to all other configurations (p
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- 2023
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3. Computer‐assisted analysis of functional internal rotation after reverse total shoulder arthroplasty: implications for component choice and orientation
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Bettina Hochreiter, Michel Meisterhans, Christoph Zindel, Anna‐Katharina Calek, and Christian Gerber
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Reverse total shoulder arthroplasty ,RTSA ,Internal rotation ,Extension ,Neck shaft angle ,Baseplate ,Orthopedic surgery ,RD701-811 - Abstract
Abstract Purpose Functional internal rotation (IR) is a combination of extension and IR. It is clinically often limited after reverse total shoulder arthroplasty (RTSA) either due to loss of extension or IR in extension. It was the purpose of this study to determine the ideal in‐vitro combination of glenoid and humeral components to achieve impingement‐free functional IR. Methods RTSA components were virtually implanted into a normal scapula (previously established with a statistical shape model) and into a corresponding humerus using a computer planning program (CASPA). Baseline glenoid configuration consisted of a 28 mm baseplate placed flush with the posteroinferior glenoid rim, a baseplate inclination angle of 96° (relative to the supraspinatus fossa) and a 36 mm standard glenosphere. Baseline humeral configuration consisted of a 12 mm humeral stem, a metaphysis with a neck shaft angle (NSA) of 155° (+ 6 mm medial offset), anatomic torsion of ‐20° and a symmetric PE inlay (36mmx0mm). Additional configurations with different humeral torsion (‐20°, + 10°), NSA (135°, 145°, 155°), baseplate position, diameter, lateralization and inclination were tested. Glenohumeral extension of 5, 10, 20, and 40° was performed first, followed by IR of 20, 40, and 60° with the arm in extension of 40°—the value previously identified as necessary for satisfactory clinical functional IR. The different component combinations were taken through simulated ROM and the impingement volume (mm3) was recorded. Furthermore, the occurrence of impingement was read out in 5° motion increments. Results In all cases where impingement occurred, it occurred between the PE inlay and the posterior glenoid rim. Only in 11 of 36 combinations full functional IR was possible without impingement. Anterosuperior baseplate positioning showed the highest impingement volume with every combination of NSA and torsion. A posteroinferiorly positioned 26 mm baseplate resulting in an additional 2 mm of inferior overhang as well as 6 mm baseplate lateralization offered the best impingement‐free functional IR (5/6 combinations without impingement). Low impingement potential resulted from a combination of NSA 135° and + 10° torsion (4/6 combinations without impingement), followed by NSA 135° and ‐20° torsion (3/6 combinations without impingement) regardless of glenoid setup. Conclusion The largest impingement‐free functional IRs resulted from combining a posteroinferior baseplate position, a greater inferior glenosphere overhang, 90° of baseplate inclination angle, 6 mm glenosphere lateralization with respect to baseline setup, a lower NSA and antetorsion of the humeral component. Surgeons can employ and combine these implant configurations to achieve and improve functional IR when planning and performing RTSA. Level of evidence Basic Science Study, Biomechanics.
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- 2023
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4. Unacceptable failure of osteochondral glenoid allograft for biologic resurfacing of the glenoid
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Filippo Familiari, Bettina Hochreiter, and Christian Gerber
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Shoulder osteoarthritis ,young patients ,osteochondral glenoid allograft ,biologic resurfacing ,failure rate ,Constant and Murley score ,Orthopedic surgery ,RD701-811 - Abstract
Abstract Purpose Glenohumeral osteoarthritis (OA) represents a challenging problem in young, physically active patients. It was the purpose of this investigation to evaluate the results of a pilot study involving glenoid resurfacing with a glenoid allograft combined with a hemiarthroplasty on the humeral side. Methods Between April 2011 to November 2013, 5 patients (3 men, 2 women, mean age 46.4, range 35‐57) with advanced OA of the glenohumeral joint, were treated with a humeral head replacement combined with replacement of the glenoid surface with an osteochondral, glenoid allograft. Results Overall, clinically, there was one excellent, one satisfactory and three poor results. Mean preoperative subjective shoulder value (SSV) was 34% (range: 20‐50%) and preoperative relative Constant‐Murley‐Score (CSr) was 43 points (range: 29‐64 points). Three patients with poor results had to be revised within the first three years. Their mean pre‐revision SSV and CSr were 38% (range: 15‐80%) and 36 points (range: 7‐59 points) respectively. One patient was revised 9 years after the primary procedure with advanced glenoid erosion and pain and one patient has an ongoing satisfactory outcome without revision. Their SSVs were 60% and 83%, their CSr were 65 points and 91 points, 9 and 10 years after the primary procedure, respectively. Mean follow‐up was 7 years (2‐10 years) and mean time to revision was 4 years (range: 1‐9 years). Conclusion The in‐vivo pilot study of a previously established in‐vitro technique of osteochondral glenoid allograft combined with humeral HA led to three early failures and only one really satisfactory clinical outcome which, however, was associated with advanced glenoid erosion. Osteochondral allograft glenoid resurfacing was associated with an unacceptable early failure rate and no results superior to those widely documented for HA or TSA, so that the procedure has been abandoned. Level of evidence Level IV, Case Series, Treatment Study.
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- 2021
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5. Health problems in youth competitive alpine skiing: A 12‐month observation of 155 athletes around the growth spurt
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Thierry Schoeb, Jörg Spörri, Walter O Frey, Stefan Fröhlich, Christian Gerber, Loris Peterhans, University of Zurich, and Spörri, Jörg
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Male ,medicine.medical_specialty ,Adolescent ,Poison control ,610 Medicine & health ,Physical Therapy, Sports Therapy and Rehabilitation ,Suicide prevention ,Occupational safety and health ,Child Development ,Sex Factors ,2732 Orthopedics and Sports Medicine ,Skiing ,Surveys and Questionnaires ,Injury prevention ,Epidemiology ,Prevalence ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Prospective Studies ,3612 Physical Therapy, Sports Therapy and Rehabilitation ,Child ,biology ,Athletes ,business.industry ,Age Factors ,Human factors and ergonomics ,Anthropometry ,biology.organism_classification ,Athletic Injuries ,Female ,10046 Balgrist University Hospital, Swiss Spinal Cord Injury Center ,business ,human activities ,Switzerland ,Demography - Abstract
Alpine ski racing is known as a high-risk sport; however, little is known on the health problems occurring at youth level. The purpose of this study was to investigate the prevalence of health problems in youth competitive alpine skiers with respect to sex, age, and season differences, to describe their severity and location and to assess the influence of biological maturation. Over a 12-month period, 155 youth competitive alpine skiers around the growth spurt were prospectively monitored for health problems using the Oslo Sports Trauma Research Centre (OSTRC) questionnaire. These data were verified by supplemental interviews at the end. Biological maturation was estimated by a non-invasive, anthropometric-based assessment method. During competition season, 42.2% of the skiers suffered from health problems and 19.8% reported their problem being substantial. Females had significantly higher rates of acute and overuse injuries compared to males, while there was no sex difference in duration, severity, and time loss. Skiers of the category U15 showed higher prevalence of acute and overuse injuries than U14 skiers. During preparation season, health problem prevalence was substantially lower. The knee was found to be the most affected body part for both acute and overuse injuries. There was a direct association between the offset to the age at peak height velocity (APHV) and the occurrence and severity of acute injuries. In conclusion, youth competitive alpine skiers suffer from a large number of health problems. Since sex, age, and biological maturation are important, effective injury prevention should already start before reaching the APHV.
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- 2020
6. Neurectomy preserves fast fibers when combined with tenotomy of infraspinatus muscle via upregulation of myogenesis
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Paola Valdivieso, Christian Gerber, Martin Flück, Severin Ruoss, Karl Wieser, Brigitte von Rechenberg, Dominik C. Meyer, and Mario C. Benn
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0301 basic medicine ,Denervation ,medicine.medical_specialty ,Physiology ,Myogenesis ,business.industry ,medicine.medical_treatment ,Tenotomy ,Neurectomy ,Infraspinatus muscle ,030105 genetics & heredity ,musculoskeletal system ,MyoD ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,0302 clinical medicine ,Endocrinology ,Physiology (medical) ,Ca2+/calmodulin-dependent protein kinase ,Internal medicine ,medicine ,Neurology (clinical) ,business ,030217 neurology & neurosurgery ,Myogenin - Abstract
INTRODUCTION We evaluated the contribution of denervation-related molecular processes to rotator cuff muscle degeneration after tendon release. METHODS We assessed the levels of myogenic (myogenin and myogenic differentiation factor [myoD]) and pro-adipogenic (peroxisome proliferator-activated receptor gamma) transcription factors; the denervation-associated proteins tenascin-C, laminin-2, and calcium/calmodulin dependent kinase II (CaMKII); and cellular alterations in sheep after infraspinatus tenotomy (TEN), suprascapular neurectomy (NEU), or both (TEN-NEU). RESULTS Extracellular ground substance increased at the expense of contractile tissue 16 weeks after surgery, correlating with CaMKII isoform levels. Sheep undergoing NEU and TEN-NEU had exaggerated infraspinatus atrophy and increased fast fibers compared with TEN sheep. The βMCaMKII isoform levels increased with tenotomy, and myoD levels tripled after denervation and were associated with slow fibers. DISCUSSION In sheep, denervation did not affect muscle-to-fat conversion after tenotomy of the infraspinatus. Furthermore, concurrent neurectomy mitigated the loss of fast fibers after tenotomy by inducing a fast-contractile phenotype. This article is protected by copyright. All rights reserved.
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- 2018
7. Glenohumeral joint reaction forces increase with critical shoulder angles representative of osteoarthritis-A biomechanical analysis
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Jess G. Snedeker, Arnd F. Viehöfer, Daniel Baumgartner, and Christian Gerber
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Orthodontics ,030222 orthopedics ,medicine.medical_specialty ,Shoulders ,business.industry ,Deltoid curve ,Biomechanics ,030229 sport sciences ,Osteoarthritis ,medicine.disease ,03 medical and health sciences ,0302 clinical medicine ,medicine.anatomical_structure ,medicine ,Physical therapy ,Orthopedics and Sports Medicine ,Humerus ,Shoulder joint ,business ,Range of motion ,Joint (geology) - Abstract
Osteoarthritis (OA) of the glenohumeral joint constitutes the most frequent indication for nontraumatic shoulder joint replacement. Recently, a small critical shoulder angle (CSA) was found to be associated with a high prevalence of OA. This study aims to verify the hypothesis that a small CSA leads to higher glenohumeral joint reaction forces during activities of daily living than a normal CSA. A shoulder simulator with simulated deltoid (DLT), supraspinatus (SSP), infraspinatus/teres minor (ISP/TM), and subscapularis (SSC) musculotendinous units was constructed. The DLT wrapping on the humerus was simulated using a pulley that could be horizontally adjusted to simulate the 28° CSA found in OA or the 33° CSA found in disease-free shoulders. Over a range of motion between 6° and 82° of thoracohumeral abduction joint forces were measured using a six-axis load cell. An OA-associated CSA yielded higher net joint reaction forces than a normal CSA over the entire range of motion. The maximum difference of 26.4 N (8.5%) was found at 55° of thoracohumeral abduction. Our model thus suggests that a CSA typical for OA predisposes the glenohumeral joint to higher joint reaction forces and could plausibly play a role in joint overloading and development of OA. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1047-1052, 2016.
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- 2016
8. A larger critical shoulder angle requires more rotator cuff activity to preserve joint stability
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Philippe Favre, Elias Bachmann, Arnd F. Viehöfer, Christian Gerber, and Jess G. Snedeker
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Orthodontics ,030222 orthopedics ,business.industry ,Shoulders ,Rotator cuff injury ,Biomechanics ,Joint stability ,030229 sport sciences ,Anatomy ,medicine.disease ,Tendon ,03 medical and health sciences ,0302 clinical medicine ,medicine.anatomical_structure ,Medicine ,Orthopedics and Sports Medicine ,Rotator cuff ,Shoulder joint ,Acromion ,business - Abstract
Shoulders with rotator cuff tears (RCT) tears are associated with significantly larger critical shoulder angles (CSA) (RCT CSA = 38.2°) than shoulders without RCT (CSA = 32.9°). We hypothesized that larger CSAs increase the ratio of glenohumeral joint shear to joint compression forces, requiring substantially increased compensatory supraspinatus loads to stabilize the arm in abduction. A previously established three dimensional (3D) finite element (FE) model was used. Two acromion shapes mimicked the mean CSA of 38.2° found in patients with RCT and that of a normal CSA (32.9°). In a first step, the moment arms for each muscle segment were obtained for 21 different thoracohumeral abduction angles to simulate a quasi-static abduction in the scapular plane. In a second step, the muscle forces were calculated by minimizing the range of muscle stresses able to compensate an external joint moment caused by the arm weight. If the joint became unstable, additional force was applied by the rotator cuff muscles to restore joint stability. The model showed a higher joint shear to joint compressive force for the RCT CSA (38.2°) for thoracohumeral abduction angles between 40° and 90° with a peak difference of 23% at 50° of abduction. To achieve stability in this case additional rotator cuff forces exceeding physiological values were required. Our results document that a higher CSA tends to destabilize the glenohumeral joint such that higher than normal supraspinatus forces are required to maintain modeled stability during active abduction. This lends strong support to the concept that a high CSA can induce supraspinatus (SSP) overload. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:961-968, 2016.
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- 2015
9. Costamere protein expression and tissue composition of rotator cuff muscle after tendon release in sheep
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Martin Flück, Karl Wieser, Dominik C. Meyer, Brigitte von Rechenberg, Severin Ruoss, Christian Gerber, Christoph B. Möhl, and Mario C. Benn
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0301 basic medicine ,medicine.medical_specialty ,Chemistry ,medicine.medical_treatment ,Tenotomy ,Adipose tissue ,Anatomy ,Sarcomere ,Tendon ,Focal adhesion ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,Endocrinology ,medicine.anatomical_structure ,Nandrolone ,Internal medicine ,medicine ,Orthopedics and Sports Medicine ,Rotator cuff ,030217 neurology & neurosurgery ,Costamere ,medicine.drug - Abstract
Previous studies suggested that degradation of contractile tissue requires cleavage of the costamere, a structural protein complex that holds sarcomeres in place. This study examined if costamere turnover is affected by a rotator cuff tear in a previously established ovine model. We found the activity of focal adhesion kinase (FAK), a main regulator of costamere turnover, was unchanged at 2 weeks but decreased by 27% 16 weeks after surgical release of the infraspinatus tendon. This was accompanied by cleavage of the costamere protein talin into a 190 kDa fragment while full length talin remained unchanged. At 2 weeks after tendon release, muscle volume decreased by 17 cm from an initial 185 cm(3) , the fatty tissue volume was halved, and the contractile tissue volume remained unchanged. After 16 weeks, the muscle volume decreased by 36 cm(3) , contractile tissue was quantitatively lost, and the fat content increased by 184%. Nandrolone administration mitigated the loss of contractile tissue by 26% and prevented fat accumulation, alterations in FAK activity, and talin cleavage. Taken together, these findings imply that muscle remodeling after tendon release occurs in two stages. The early decrease of muscle volume is associated with reduction of fat; while, the second stage is characterized by substantial loss of contractile tissue accompanied by massive fat accumulation. Regulation of costamere turnover is associated with the loss of contractile tissue and seems to be impacted by nandrolone treatment. Clinically, the costamere may represent a potential intervention target to mitigate muscle loss after a rotator cuff tear. © 2017 The Authors. Journal of Orthopaedic Research published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res.
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- 2017
10. Supraspinatus tendon load during abduction is dependent on the size of the critical shoulder angle: A biomechanical analysis
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Jess G. Snedeker, Arnd F. Viehöfer, Daniel Baumgartner, and Christian Gerber
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musculoskeletal diseases ,Shoulders ,business.industry ,Deltoid curve ,Biomechanics ,Anatomy ,Supraspinatus tendon ,Tendon ,medicine.anatomical_structure ,medicine ,Orthopedics and Sports Medicine ,Rotator cuff ,Range of motion ,business - Abstract
Shoulders with supraspinatus (SSP) tears are associated with significantly larger critical shoulder angles (CSA) compared to disease-free shoulders. We hypothesized that larger CSAs increase the ratio of joint shear to joint compression forces (defined as "instability ratio"), requiring substantially increased compensatory supraspinatus loads. A shoulder simulator with simulated deltoid, supraspinatus, infraspinatus/teres minor, and subscapularis musculotendinous units was constructed. The model was configured to represent either a normal CSA of 33° or a CSA characteristic of shoulders with rotator cuff tears (38°), and the components of the joint forces were measured. The instability ratio increased for the 38° CSA compared with the control CSA (33°) for a range of motion between 6° to 61° of thoracohumeral abduction with the largest differences in instability observed between 33° and 37° of elevation. In this range, SSP force had to be increased by 13-33% (15-23 N) to stabilize the arm in space. Our results support the concept that a high CSA can induce SSP overload particularly at low degrees of active abduction.
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- 2014
11. Effect of experimental suprascapular nerve block on active glenohumeral translations in vivo
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Stephan Blumenthal, Christian Gerber, Dominik Weishaupt, Armin Curt, Philippe Favre, and Clément M. L. Werner
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Adult ,Male ,Shoulder ,medicine.medical_treatment ,Infraspinatus muscle ,Rotator Cuff ,Paralysis ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Displacement (orthopedic surgery) ,Rotator cuff ,Range of Motion, Articular ,Shoulder Joint ,business.industry ,Nerve Block ,Anatomy ,Middle Aged ,Magnetic Resonance Imaging ,medicine.anatomical_structure ,Cuff ,Nerve block ,Shoulder joint ,medicine.symptom ,business ,Range of motion - Abstract
Static superior shoulder instability is associated with long-standing rotator cuff tears. Factors or mechanisms which can prevent superior migration of the humeral head, and therefore allow preservation or restoration of shoulder function despite nonanatomical cuff repair, are poorly understood. The question has therefore arisen, whether centering of the humeral head was the result of active shoulder muscle function. It was the goal of this experimental investigation to (1) determine the pattern of glenohumeral translations during active shoulder abduction measured by open-magnetic resonance imaging (MRI) techniques, and to (2) determine the influence of experimental paralysis of the infra- and supraspinatus muscles on these translations. In contrast to prior experimental investigations, the humeral head remained always centered in the glenoid fossa during active abduction. No superior migration of the humeral head could be provoked with experimental paralysis of the supra- and/or infraspinatus muscles. The hypothesis that static or dynamic superior humeral head displacement is prevented by active-supra- and/or infraspinatus muscle function must therefore be rejected, for the shoulder with a structurally intact muscle-tendon-bone unit.
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- 2006
12. The effect of capsular tightening on humeral head translations
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Hilaire A.C. Jacob, Christian Gerber, Richard W. Nyffeler, and Clément M. L. Werner
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Joint Instability ,musculoskeletal diseases ,Subluxation ,Shoulder Joint ,business.industry ,Shoulders ,Movement ,Capsule ,Osteoarthritis ,Anatomy ,Humerus ,In Vitro Techniques ,medicine.disease ,medicine.anatomical_structure ,medicine ,Humans ,Head (vessel) ,Orthopedics and Sports Medicine ,Displacement (orthopedic surgery) ,business ,Cadaveric spasm ,Joint Capsule - Abstract
Idiopathic or surgical tightening of the glenohumeral joint capsule may cause displacement of the humeral head relative to the glenoid fossa and favor the development of instability and/or osteoarthritis. In the present investigation the relative position of the humerus to the glenoid fossa was determined at the end of the ranges of eight different passive movements before and after selective capsular plication in eight cadaveric shoulders to study the effects of selective capsular plications on the kinematics of the shoulder. While the capsule was in its unaltered state, translation of the humeral head was 3.8 mm superiorly in abduction, 7.3 mm antero-superiorly in flexion. In internal rotation in 0 degrees, 45 degrees and 90 degrees of abduction the head moved 6.1, 8.0 and 12.0 mm antero-inferiorly. In external rotation at 0 degrees of abduction the translation was 0.9 mm antero-inferiorly, at 45 degrees and 90 degrees of abduction it was 4.3 and 5.6 mm postero-inferiorly, respectively. Plications of the anterior part of the capsule reproducibly and significantly either increased or decreased translations during flexion (up to 5.9 mm anteriorly and up to 3.8 mm inferiorly), external rotation (up to 2.9 mm posteriorly and 1 mm inferiorly) and internal rotation (from 5.5 mm posteriorly to 2 mm anteriorly and up to 2.2 mm superiorly). Posterior plications had only little effect on translations (mainly a decrease of anterior translation during flexion of 2.8 mm).The 'obligate' glenohumeral translations which occur towards the end of passive shoulder movements are altered in a reproducible fashion by tightening specific parts of the glenohumeral joint capsule, as often carried out in treatment of shoulder instability. These alterations of the kinematics of the glenohumeral joint may be relevant for the development of static subluxation and osteoarthitis as seen after too tight plication in the treatment of instability [Int. Orthop. (SICOT) 67-B (1985) 709; J. Bone Joint Surg. Am. 72 (1990) 1193; J. Bone Joint Surg. Am. 66-A (1984) 169; J. Bone Joint Surg. Am. 65 (1983) 456].
- Published
- 2004
13. Glenoid version and rotator cuff tears
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Patrice Tétreault, David Zurakowski, Christian Gerber, and Andreas Krueger
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musculoskeletal diseases ,Shoulders ,Impingement syndrome ,Rotator Cuff Injuries ,Rotator Cuff ,Risk Factors ,Tendon Injuries ,X ray computed ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Rotator cuff ,Observer Variation ,Shoulder Joint ,business.industry ,Rotator cuff injury ,Significant difference ,Reproducibility of Results ,Anatomy ,musculoskeletal system ,medicine.disease ,Magnetic Resonance Imaging ,medicine.anatomical_structure ,Cuff ,Tears ,Stress, Mechanical ,Tomography, X-Ray Computed ,business - Abstract
The purpose of this study was to determine the relationship between rotator cuff (RC) tear and the orientation of the glenoid. Ninety-six shoulders (94 patients) that underwent open RC repair were grouped according to the type of tear. We measured on MRI the acromio-glenoid angle (AG) and the supraspinatus fossa glenoid angle on the anterior-posterior (SGAP) and axial (SGAX) views. RC patients had a smaller AG angle (76+/-7 degrees vs. 86+/-10 degrees ) and a larger SGAP angle (112+/-6 degrees vs. 102+/-7 degrees ) compared to controls (p
- Published
- 2004
14. Modification of Cyclosporin A (CS): Generation of an enolate at the sarcosine residue and reactions with electrophiles
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Christian Gerber, Shin-ichiro Shoda, Soo Y. Ko, Dieter Seebach, Manfred Krieger, Adrian Thaler, C. William Murtiashaw, Hans G. Bossler, Reto Naef, Albert K. Beck, and Roland Wenger
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chemistry.chemical_classification ,Stereochemistry ,Organic Chemistry ,Biochemistry ,Medicinal chemistry ,Lithium diisopropylamide ,Catalysis ,Stereocenter ,Inorganic Chemistry ,chemistry.chemical_compound ,Electrophilic substitution ,chemistry ,Cyclosporin a ,Drug Discovery ,Electrophile ,Alkoxide ,Physical and Theoretical Chemistry ,Tetrahydrofuran ,Alkyl - Abstract
Strong bases (lithium diisopropylamide (LDA) or BuLi) convert cyclosporin A (CS) to hexalithio derivative containing a Li alkoxide, four Li azaenolate, and one Li enolate units. The Li6 compound is solubilized in tetrahydrofuran (THF) by addition of excess LDA or LiCl. Reactions with electrophiles (alkyl halides, aldehydes, ClCO2R, CO2, (RS)2, D2O) at low temperatures give products containing new side chains in amino-acid residue 3 of the cyclic undecapeptide (see 1–13, Schemes 1, and 2, and Figs. 1 and 2) in moderate to high yields and, with Re- or Si-selectivities, depending upon the conditions of lithiation of up to 7:1, Pure CS derivatives (Scheme 2, Table 1 in the Exper. Part) can be isolated by column chromatography. N-Alkylations or cleavage of the peptide backbone by carbonyl addition occur only at higher temperatures and/or with prolonged reaction times (see 14 and 15 in Scheme 4). Very little or no epimerization of stereogenic centers occurs under the conditions employed. Possible reasons for the feasibility of these surprizing conversions of CS are discussed (Schemes 4 and 5 and Fig. 3). For comparision, [MeAla3]CS (2b) and [D-MeAla3]CS (2a) were also prepared by conventional peptide synthesis in solution (Schemes 6 and 7). Their 1H- and 13C-NMR spectra are compared with those of CS (Table 2 in the Exper. Part).
- Published
- 1993
15. ChemInform Abstract: Dipeptide Derivatives with a Phosphonate Instead of Carboxylate Terminus by C-Alkylation of Protected (Decarboxy-dipeptidyl) phosphonates
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Dieter Seebach and Christian Gerber
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chemistry.chemical_compound ,Deprotonation ,Dipeptide ,chemistry ,Stereochemistry ,Diastereomer ,Moiety ,General Medicine ,Carboxylate ,Alkylation ,Phosphonate ,Stereocenter - Abstract
Z-Protected diphenyl (decarboxy-dipeptidyl)phosphonates 5a-c with a (decarboxysarcosinyl)phosphonate moiety are prepared from Z-L-alanine (1a). Z-L-valine (1b), and Z-L-phenylalanine (1c) by the following series of steps: coupling with methyl sarcosinate (2a–c), saponification (3a–c), Hofer-Moest oxidative decarboxyiation by electrolysis in MeOH (4a–c), and Arbuzov reaction with P(OPh)3/TiCl4 (Scheme 3). Double deprotonation and alkylation lead to non-stereoselective incorporation of side chains next to the phosphonate group (products of type 6–8, nine examples, see Scheme 4). In the cases of 6a–c and 8c, the diastereoisomers could be separated and the configuration of the newly formed stereogenic center deduced. We assign the L,D-configuration to the diastereoisomers for which the 31P-NMR signal appears at higher field.
- Published
- 2010
16. Dipeptide Derivatives with a Phosphonate Instead of Carboxylate Terminus byC-Alkylation of Protected (Decarboxy-dipeptidyl)phosphonates
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Dieter Seebach and Christian Gerber
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Dipeptide ,Chemistry ,Stereochemistry ,Organic Chemistry ,Diastereomer ,Alkylation ,Biochemistry ,Phosphonate ,Catalysis ,Stereocenter ,Inorganic Chemistry ,chemistry.chemical_compound ,Deprotonation ,Drug Discovery ,Moiety ,Carboxylate ,Physical and Theoretical Chemistry - Abstract
Z-Protected diphenyl (decarboxy-dipeptidyl)phosphonates 5a-c with a (decarboxysarcosinyl)phosphonate moiety are prepared from Z-L-alanine (1a). Z-L-valine (1b), and Z-L-phenylalanine (1c) by the following series of steps: coupling with methyl sarcosinate (2a–c), saponification (3a–c), Hofer-Moest oxidative decarboxyiation by electrolysis in MeOH (4a–c), and Arbuzov reaction with P(OPh)3/TiCl4 (Scheme 3). Double deprotonation and alkylation lead to non-stereoselective incorporation of side chains next to the phosphonate group (products of type 6–8, nine examples, see Scheme 4). In the cases of 6a–c and 8c, the diastereoisomers could be separated and the configuration of the newly formed stereogenic center deduced. We assign the L,D-configuration to the diastereoisomers for which the 31P-NMR signal appears at higher field.
- Published
- 1991
17. Muscle filament spacing and short-term heavy-resistance exercise in humans
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J. M. Lüthi, Christian Gerber, Hans-Heinrich Hoppeler, P. Vock, and H. Claassen
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Adult ,Male ,Sarcomeres ,Muscle tissue ,medicine.medical_specialty ,Myofilament ,Time Factors ,Adolescent ,Physiology ,Myosins ,Linear distance ,Protein filament ,Internal medicine ,Myosin ,medicine ,Humans ,Exercise ,Actin ,Training period ,Chemistry ,Muscles ,Resistance training ,Anatomy ,Biomechanical Phenomena ,Radiography ,Microscopy, Electron ,Endocrinology ,medicine.anatomical_structure ,Research Article - Abstract
1. Six weeks of a dynamic heavy-resistance training of the quadriceps muscle in healthy young men resulted in a continuous increase in muscle strength, in an increase in muscle cross-sectional area (significant only in the second half of the training period) and in an increase in radiological density of the muscle tissue of 3.1% (2P less than 0.001) in the first three weeks and 1.6% (2P less than 0.01) in the second three weeks. 2. The linear distance between myosin filaments (38.7 +/- 0.3 nm before, 38.7 +/- 0.4 nm after training; mean +/- S.E.M.) as well as the ratio of actin to myosin filaments (3.94 +/- 0.03 before, 3.86 +/- 0.06 after training) did not change with training. 3. These results refute the concept that the increases in muscle strength or radiological density during short-term heavy-resistance training are caused by changes in myofilament spacing.
- Published
- 1989
18. Elektrochemische Decarboxylierung vonL.-Threonin- und Oligopeptid-Derivaten unter Bildung vonN-Acyl-N, O-acetalen: Herstellung von Oligopeptiden mit Carboxamid-oder Phosphonat-C-Terminus
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Philippe Renaud, Roland Charczuk, Christian Gerber, Heinz Berner, Dieter Seebach, and Helmut Schneider
- Subjects
Oligopeptide ,Tertiary amine ,Decarboxylation ,Stereochemistry ,Organic Chemistry ,Biochemistry ,Medicinal chemistry ,Catalysis ,Inorganic Chemistry ,Hydrolysis ,chemistry.chemical_compound ,Nucleophile ,chemistry ,Amide ,Drug Discovery ,Amine gas treating ,Stereoselectivity ,Physical and Theoretical Chemistry - Abstract
Electrochemical Decarboxylation of L-Threonine and Oligopeptide Derivatives with Formation of N-Acyl-N, O-acetals: Preparation of Oligopeptides with Amide or Phophonate C-Terminus Derivatives of α-amino acids with two stereogenic centers (cf.L-threonine) and of di-, tri-, and tetrapeptides are electrolyzed in MeOH or AcOH, with formation of N-acyl-N, O-acetals (1b–15b, 20b), in an anodic oxidative substitution of the COOH by an OR group. The amine ends of the oligopeptides may be benzyloxycarbonyl(Z)- or (tert-butoxy)carbonyl(Boc)-protected. With unprotected dipeptides, an electrolytic decarboxylative cyclization to imidazolidinones (18c, 19c) may also occur (in H2O/NH4OAc). The electrolyses are carried out in simple flasks with cooling jackets (‘undivided cell’), using constant current conditions and anodes of Pt or glassy C. The electrolyte is generated in situ by adding 10–20 mol-% of a tertiary amine. Mild acidic hydrolysis of electrolysis products thus obtained may lead to amino-acid amides or peptide amides (10c, 11c, 12c, 17c) with one amino acid less than the starting material. The N, O-acetals from L-threonine and the oligopeptides also react with organometallic nucleophiles such as Grignard compounds (21–26, 29), with formation of products in which the original COOH group has been replaced by alkyl or allyl (sometimes even with moderate stereoselectivity). By treatment of the peptide-derived (open-chain) N, O-acetals with trialkyl or triaryl phosphites/TiCl4 the RO group is replaced by a phosphodiester group in a (non-diastereoselective) Michaelis-Arbuzov-type reaction (1d, 1e, 2d–9d, 5e). Thus, the two-step sequence of electrolysis and phosphonation converts an oligopeptide derivative to an analogue with a phosphonic-acid end group. The diastereoisomeric N-protected dimethyl and diethyl dipeptidephosphonates (also prepared from the corresponding diaryl esters by Ti(OR)4-mediated transesterification) could be separated by preparative HPLC (SiO2, Lichrosorb Si 60, 10 μm); the dextrorotatory isomers of 1d–3d were assigned L, D-, the laevoratory ones L, L-configuration by hydrolysis to and identification of the known amino and aminophosphonic acids. The results described demonstrate a new simple route leading, from a given oligopeptide, to pure peptide analogues of known configuration.
- Published
- 1989
Catalog
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