Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 183
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Artigo em Inglês | MEDLINE | ID: mdl-32044251

RESUMO

BACKGROUND: Radial head instability continues to be a challenge in the management of anterior Monteggia injuries; however, there is a paucity of literature on the factors that contribute to this instability. The aim of this biomechanical investigation was to examine the effects of ulnar angulation and soft tissue insufficiency on radial head stability in anterior Monteggia injuries. METHODS: Six cadaveric arms were mounted in an elbow motion simulator. Radial head translation was measured during simulated active elbow flexion with the forearm supinated. After testing the elbows in the intact state, the ulna was osteotomized and tested at 0°, 10°, 20°, and 30° of extension angulation. To examine the effect of soft tissue insufficiency, the anterior radiocapitellar joint capsule, annular ligament, quadrate ligament, and the proximal and middle interosseous membrane (IOM) were sequentially sectioned. RESULTS: There was a significant increase in anterior radial head translation with greater ulnar extension angulation. Sequential soft tissue sectioning also significantly increased anterior radial head translation. There was no increase in radial head translation with isolated sectioning of the anterior radiocapitellar joint capsule. Additional sectioning of the annular ligament and quadrate ligament slightly increased anterior radial head translation but did not reach statistical significance. Subsequent sectioning of the proximal and middle IOM resulted in significant increases in anterior radial head translation. CONCLUSION: Our study demonstrates that progressive ulnar extension angulation results in an incremental increase in anterior radial head translation in anterior Monteggia injuries. Moreover, increasing magnitudes of soft tissue disruption result in greater anterior radial head instability.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32061510

RESUMO

BACKGROUND: The purpose of this study was 2-fold: (1) to quantify type E2 bone loss orientation and its association with rotator cuff fatty infiltration and (2) to examine reverse baseplate designs used to manage type E2 glenoids. METHODS: Computed tomography scans of 40 patients with type E2 glenoids were examined for pathoanatomic features and erosion orientation. The rotator cuff fatty infiltration grade was compared with the erosion orientation angle. To compare reconstructive options in light of the pathoanatomic findings, virtual implantation of 4 glenoid baseplate designs (standard, half wedge, full wedge, and patient-matched) was conducted to determine the volume of bone removal for seating and impingement-free range of motion. RESULTS: The mean type E2 erosion orientation angle was 47° ± 17° from the 0° superoinferior glenoid axis, resulting in the average erosion being located in the posterosuperior quadrant directed toward the 10:30 clock-face position. The type E2 neoglenoid, on average, involved 67% of the total glenoid surface (total surface area, 946 ± 209 mm2; neoglenoid surface area, 636 ± 247 mm2). The patient-matched baseplate design resulted in significantly (P ≤ .01) less bone removal (200 ± 297 mm3) for implantation, followed by the full-wedge design (1228 ± 753 mm3), half-wedge design (1763 ± 969 mm3), and standard (non-augmented) design (4009 ± 1210 mm3). We noted a marked difference in erosion orientation toward a more superior direction as the subscapularis fatty infiltration grade increased from grade 3 to grade 4 (P < .001). CONCLUSION: The average type E2 erosion orientation was directed toward the 10:30 clock-face position in the posterosuperior glenoid quadrant. This orientation resulted in the patient-matched glenoid augmentation requiring the least amount of bone removal for seating, followed by the full-wedge, half-wedge, and standard designs. Implant selection also substantially affected computationally derived range of motion in external rotation, flexion, extension, and adduction.

3.
J Med Chem ; 63(4): 1660-1670, 2020 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-31990537

RESUMO

Endothelial lipase (EL) hydrolyzes phospholipids in high-density lipoprotein (HDL) resulting in reduction in plasma HDL levels. Studies with murine transgenic, KO, or loss-of-function variants strongly suggest that inhibition of EL will lead to sustained plasma high-density lipoprotein cholesterol (HDL-C) increase and, potentially, a reduced cardiovascular disease (CVD) risk. Herein, we describe the discovery of a series of oxadiazole ketones, which upon optimization, led to the identification of compound 12. Compound 12 was evaluated in a mouse pharmacodynamics (PD) model and demonstrated a 56% increase in plasma HDL-C. In a mouse reverse cholesterol transport study, compound 12 stimulated cholesterol efflux by 53% demonstrating HDL-C functionality.

4.
J Anim Ecol ; 89(1): 207-220, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30771254

RESUMO

Currently, the deployment of tracking devices is one of the most frequently used approaches to study movement ecology of birds. Recent miniaturization of light-level geolocators enabled studying small bird species whose migratory patterns were widely unknown. However, geolocators may reduce vital rates in tagged birds and may bias obtained movement data. There is a need for a thorough assessment of the potential tag effects on small birds, as previous meta-analyses did not evaluate unpublished data and impact of multiple life-history traits, focused mainly on large species and the number of published studies tagging small birds has increased substantially. We quantitatively reviewed 549 records extracted from 74 published and 48 unpublished studies on over 7,800 tagged and 17,800 control individuals to examine the effects of geolocator tagging on small bird species (body mass <100 g). We calculated the effect of tagging on apparent survival, condition, phenology and breeding performance and identified the most important predictors of the magnitude of effect sizes. Even though the effects were not statistically significant in phylogenetically controlled models, we found a weak negative impact of geolocators on apparent survival. The negative effect on apparent survival was stronger with increasing relative load of the device and with geolocators attached using elastic harnesses. Moreover, tagging effects were stronger in smaller species. In conclusion, we found a weak effect on apparent survival of tagged birds and managed to pinpoint key aspects and drivers of tagging effects. We provide recommendations for establishing matched control group for proper effect size assessment in future studies and outline various aspects of tagging that need further investigation. Finally, our results encourage further use of geolocators on small bird species but the ethical aspects and scientific benefits should always be considered.

5.
J Shoulder Elbow Surg ; 29(1): 167-174, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31473132

RESUMO

BACKGROUND: Little is known about the cortical-like and cancellous bone density variations in superiorly eroded glenoids due to cuff tear arthropathy. The purpose of this study was to analyze regional bone density in type E2 glenoids. METHODS: Clinical shoulder computed tomography scans were obtained from 32 patients with a type E2 superior erosion (10 men and 22 women; mean age, 73 years). Measurement regions were organized into quadrants (superior, inferior, anterior, and posterior) and depth regions. The depth regions were incremented by 2 mm from 0 to 10 mm. A repeated-measures multiple analysis of variance was performed to assess differences and interactions between mean densities (cortical-like and cancellous bone) in each depth, in each quadrant, and between sexes. RESULTS: The lowest cancellous bone density was found in the inferior glenoid quadrant compared with all other quadrants (307 ± 50 Hounsfield units [HU], P < .001). At the glenoid surface, the superior quadrant contained the highest mean density for cortical-like bone (895 ± 97 HU); this differed significantly from the posterior, anterior, and inferior quadrants (P ≤ .033). As for depth of measurement, cortical-like bone was most dense at the glenoid surface (0-2 mm, 892 ± 91 HU), and density decreased significantly at depths greater than 2 mm (P ≤ .019). CONCLUSION: In patients with type E2 glenoids due to cuff tear arthropathy, the densest bone was found in the superior quadrant in the area of erosion. The inferior quadrant, which tends to be unloaded as the humeral head migrates superiorly, had the lowest density bone. In addition, the best-quality bone was located at the glenoid surface as compared with deeper in the vault.


Assuntos
Densidade Óssea , Osso Esponjoso/diagnóstico por imagem , Cavidade Glenoide/diagnóstico por imagem , Artropatia de Ruptura do Manguito Rotador/diagnóstico por imagem , Idoso , Idoso de 80 Anos ou mais , Feminino , Cavidade Glenoide/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Artropatia de Ruptura do Manguito Rotador/fisiopatologia , Articulação do Ombro/diagnóstico por imagem , Tomografia Computadorizada por Raios X
6.
Artigo em Inglês | MEDLINE | ID: mdl-31711829

RESUMO

BACKGROUND: Several humeral stem design modifications for shoulder arthroplasty, including reduced stem length, changes to metaphyseal geometry, and alterations to implant surface texture, have been introduced to reduce stress shielding. However, the effect of changes in the diametral size of short-stem humeral components remains poorly understood. The purpose of this finite element study was to quantify the effect of varying the size of short-stem humeral components on the changes in bone stress from the intact state to the reconstructed state. METHODS: Three-dimensional models of 8 male cadaveric humeri (mean age, 68 ± 6 years; all left-sided humeri) were constructed from computed tomography data using Mimics software. Each humerus was then reconstructed with 2 short-stem components (Exactech Preserve), one having a larger diametral size (SH+) and one having a smaller diametral size (SH-). Modeling was conducted for loading states consistent with 45° and 75° of abduction, and the resulting changes in bone stress compared with the intact state and the expected bone response were determined. RESULTS: The smaller (SH-) short-stem implant produced humeral cortical and trabecular bone stresses that were closer to the intact state than the larger (SH+) short-stem implant at several locations beneath the humeral head resection (P ≤ .032). A similar trend was observed for expected bone response, where the smaller (SH-) short-stem implant had a smaller proportion of bone that was expected to resorb following reconstruction compared with the larger (SH+) short-stem implant for several slice depths in the medial quadrant (P ≤ .02). DISCUSSION: These findings may indicate that smaller short-stem components are favorable in terms of stress shielding.

7.
J Shoulder Elbow Surg ; 28(12): 2394-2399, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31371158

RESUMO

BACKGROUND: Radial head hemiarthroplasty is commonly used to manage comminuted displaced fractures. Regarding implant fixation, current designs vary, with some prostheses aiming to achieve a tight "fixed" fit and others using a smooth stem with an over-reamed "loose" fit. The purpose of this study was to evaluate the effect of radial head hemiarthroplasty stem fit on radiocapitellar contact using a finite element model that simulated both fixed (size-for-size) and loose (1-, 2-, and 3-mm over-reamed) stem fits. It was hypothesized that a loose stem fit would improve radiocapitellar contact mechanics, with an increased contact area and decreased contact stress, by allowing the implant to find its "optimal" position with respect to the capitellum. METHODS: Finite element models of the elbow were produced to compare the effects of stem fit on radiocapitellar contact of a metallic axisymmetric radial head implant. Radiocapitellar contact mechanics (contact area and maximum contact stress) were computed for 0°, 45°, 90°, and 135° of elbow flexion with the forearm in neutral rotation, pronation, and supination. RESULTS: The data suggest that the loose smooth stem radial head implant may be functioning like a bipolar implant in optimizing radiocapitellar contact. Over-reaming of 3 mm produced a larger amount of stress concentration on the capitellum, suggesting there may be a limit to how loose a smooth stem implant should be implanted. CONCLUSIONS: The loose 1 to 2 mm over-reamed stem provided optimal contact mechanics of the metallic axisymmetric radial head implant compared with the fixed stem.


Assuntos
Articulação do Cotovelo/fisiopatologia , Articulação do Cotovelo/cirurgia , Prótese de Cotovelo , Hemiartroplastia/métodos , Desenho de Prótese , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Epífises/lesões , Epífises/cirurgia , Feminino , Análise de Elementos Finitos , Antebraço/fisiopatologia , Fraturas Cominutivas/cirurgia , Hemiartroplastia/instrumentação , Humanos , Masculino , Pessoa de Meia-Idade , Pronação , Fraturas do Rádio/cirurgia , Amplitude de Movimento Articular , Rotação , Supinação , Tomografia Computadorizada por Raios X
8.
Am J Sports Med ; 47(12): 2827-2835, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31461303

RESUMO

BACKGROUND: Medial collateral ligament (MCL) injuries are common after elbow trauma and in overhead throwing athletes. A hinged elbow orthosis (HEO) is often used to protect the elbow from valgus stress early after injury and during early return to play. However, there is minimal evidence regarding the efficacy of these orthoses in controlling instability and their influence on long-term clinical outcomes. PURPOSE: (1) To quantify the effect of an HEO on elbow stability after simulated MCL injury. (2) To determine whether arm position, forearm rotation, and muscle activation influence the effectiveness of an HEO. STUDY DESIGN: Controlled laboratory study. METHODS: Seven cadaveric upper extremity specimens were tested in a custom simulator that enabled elbow motion via computer-controlled actuators and motors attached to relevant tendons. Specimens were examined in 2 arm positions (dependent, valgus) and 2 forearm positions (pronation, supination) during passive and simulated active elbow flexion while unbraced and then while braced with an HEO. Testing was performed in intact elbows and repeated after simulated MCL injury. An electromagnetic tracking device measured valgus angulation as an indicator of elbow stability. RESULTS: When the arm was dependent, the HEO increased valgus angle with the forearm in pronation (+1.0°± 0.2°, P = .003) and supination (+1.5°± 0.0°, P = .006) during active motion. It had no significant effect on elbow stability during passive motion. In the valgus position, the HEO had no effect on elbow stability during passive or active motion in pronation and supination. With the arm in the valgus position with the HEO, muscle activation reduced instability during pronation (-10.3°± 2.5°, P = .006) but not supination (P = .61). CONCLUSION: In this in vitro study, this HEO did not enhance mechanical stability when the arm was in the valgus and dependent positions after MCL injury. CLINICAL RELEVANCE: After MCL injury, an HEO likely does not provide mechanical elbow stability during rehabilitative exercises or when the elbow is subjected to valgus stress such as occurs during throwing.

9.
J Shoulder Elbow Surg ; 28(10): 1841-1847, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31272890

RESUMO

BACKGROUND: The current management of massive, irreparable rotator cuff tears is challenging, and no individual surgical technique has demonstrated clinical superiority. This study evaluated the role of a subacromial balloon spacer and its ability to depress the humeral head in the setting of a massive, irreparable rotator cuff tear. METHODS: Eight cadaveric shoulders were tested. The specimens were mounted onto a shoulder simulator that applied muscle loading. Five shoulder states were tested: intact; irreparable rotator cuff tear; and inflation of the subacromial balloon spacer with 10, 25, and 40 mL of saline solution on the irreparable rotator cuff tear. Humeral head migration was measured at 0°, 30°, 60°, and 90° of shoulder abduction. RESULTS: After creation of a massive, irreparable rotator cuff tear, in 0° of abduction, the humeral head migrated superiorly by a mean of 3.5 ± 0.7 mm compared with the intact shoulder state (P = .002). The subacromial balloon spacer inflated to 25 mL translated the humeral head inferiorly relative to the torn state by an average of 3.2 ± 0.6 mm (P = .001) for all abduction angles. The balloon inflated to 10 mL was ineffective at restoring humeral head position as it was still significantly superior than intact (P = .017). The balloon inflated to 40 mL was successful in depressing the humeral head; however, it over-translated the humeral head anteroinferiorly, such that it was significantly different from the intact condition (P < .001). Overall, the 25-mL balloon best restored the humeral head position. CONCLUSION: The results of this study demonstrate that the subacromial balloon spacer is most effective in depressing the humeral head and restoring the glenohumeral joint position when inflated to 25 mL.


Assuntos
Cabeça do Úmero/fisiopatologia , Lesões do Manguito Rotador/fisiopatologia , Lesões do Manguito Rotador/cirurgia , Idoso , Fenômenos Biomecânicos , Cadáver , Humanos , Masculino , Pessoa de Meia-Idade , Procedimentos Ortopédicos/instrumentação , Ruptura/fisiopatologia , Ruptura/cirurgia , Articulação do Ombro/cirurgia
11.
Bioorg Med Chem Lett ; 29(15): 1918-1921, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31176700

RESUMO

A low level of high density lipoprotein (HDL) is an independent risk factor for cardiovascular disease. HDL reduces inflammation and plays a central role in reverse cholesterol transport, where cholesterol is removed from peripheral tissues and atherosclerotic plaque. One approach to increase plasma HDL is through inhibition of endothelial lipase (EL). EL hydrolyzes phospholipids in HDL resulting in reduction of plasma HDL. A series of benzothiazole sulfone amides was optimized for EL inhibition potency, lipase selectivity and improved pharmacokinetic profile leading to the identification of Compound 32. Compound 32 was evaluated in a mouse pharmacodynamic model and found to show no effect on HDL cholesterol level despite achieving targeted plasma exposure (Ctrough > 15 fold over mouse plasma EL IC50 over 4 days).

12.
Science ; 364(6445)2019 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-31196986

RESUMO

Kubelka et al (Reports, 9 November 2018, p. 680) claim that climate change has disrupted patterns of nest predation in shorebirds. They report that predation rates have increased since the 1950s, especially in the Arctic. We describe methodological problems with their analyses and argue that there is no solid statistical support for their claims.


Assuntos
Mudança Climática , Comportamento de Nidação , Animais , Regiões Árticas , Comportamento Predatório
13.
J Hand Surg Am ; 44(8): 669-679, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31171375

RESUMO

PURPOSE: To evaluate the effect of ulnar shortening on distal forearm loading following simulated dynamic motion. METHODS: Ulnar shortening was simulated using a custom-built adjustable implant to simulate up to 4 mm of ulnar shortening (-4 mm) in 9 cadaveric extremities. Load cells were placed in the distal ulna and radius to quantify axial loading. Using a wrist and forearm motion simulator, absolute and percentage loads were measured during dynamic flexion, ulnar deviation (UD), flexion dart throw (DT), and pronation. RESULTS: There was a significant decrease in absolute and percentage distal ulnar loads at each interval of ulnar shortening during flexion, UD, DT, and pronation. The distal ulna bore no compressive loads, and in fact, tensile loads were measured in the ulna at 2 mm of ulnar shortening during DT and pronation, at 3 mm during flexion, and at 4 mm during UD. CONCLUSIONS: A progressive decrease in distal ulnar loads with generation of tensile loads was observed with sequential ulnar shortening. CLINICAL RELEVANCE: Ulnar shortening greater than 2 mm can result in tensile loading in the distal ulna. When managing ulnar impaction syndrome, excessive shortening may not be required to provide relief of symptoms.

14.
Clin Biomech (Bristol, Avon) ; 67: 85-89, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31078898

RESUMO

BACKGROUND: Clinical tests for posterolateral rotatory instability of the elbow apply external torsional moments to the forearm; however, biomechanical studies of lateral collateral ligament injuries and their surgical repair, reconstruction and rehabilitation have primarily relied on varus gravity loading to quantify instability. The aim of this investigation was to determine the effect of torsional moments on the posterolateral rotatory instability of the lateral ligament deficient elbow. METHODS: Six cadaveric arms were tested in an elbow motion simulator with the arm in the varus position. A threaded outrigger was inserted on the dorsal aspect of the proximal ulna to suspend 400 g, 600 g, and 800 g of weight to allow torsional moments of 0.12, 0.18, and 0.23 Nm respectively on the ulna. An injured model was created by sectioning of the common extensor origin, and the lateral collateral ligament. FINDINGS: During simulated active flexion with the arm in varus, the injured model resulted in a significant increase in external rotation of the ulnohumeral articulation with the forearm both pronated and supinated (pronation: P = .021; supination: P = .015). The application of torsional moments to the lateral ligament deficient elbow resulted in a significant increase in the posterolateral rotatory instability of the elbow. INTERPRETATION: This investigation demonstrates that the application of even small amounts of external torsional moments on the forearm with the arm in the varus position increases the rotational instability of the lateral ligament deficient elbow. During clinical examination for posterolateral rotatory instability and biomechanical studies of lateral ligament injury, the application of external torsion to the forearm should be considered to detect subtle instability. LEVEL OF EVIDENCE: Basic Science Study.

15.
J Hand Surg Am ; 44(7): 556-563.e5, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31126814

RESUMO

PURPOSE: To evaluate the effect of radial length change on distal forearm loading during simulated dynamic wrist motion. METHODS: A custom-built adjustable radial implant was used to simulate up to 4 mm of distal radius shortening (-4 mm) and 3 mm of lengthening (+3 mm). Load cells were placed in the distal radius and ulna in cadavers to measure their respective axial loads. The specimens were mounted on a wrist motion simulator that produced active wrist motion via tendon actuation. To simulate radial lengthening osteotomy following radial shortening from malunion, the radius was sequentially lengthened by 1-mm intervals from -4 mm to +3 mm. Radial and ulnar loads were measured during simulated wrist flexion, ulnar deviation (UD), and flexion dart throw (DT) at each interval of radial lengthening up to +3 mm. RESULTS: During wrist flexion and UD, for each millimeter of radial lengthening from -4 mm to the native length, there was a significant increase in distal radial loads. No significant change in radial load was observed beyond the native length during flexion and UD. There was no change in distal radial loads during DT for each interval of radial lengthening from -4 mm to +3 mm. A sequential decrease in ulnar loads was observed as the radius was lengthened from -4 mm to +3 mm for all wrist motions evaluated. CONCLUSIONS: Radial lengthening beyond the native length was not detrimental to radial loading and further reduced distal ulnar loading; achieving at least native ulnar variance seems to be appropriate to restore normal biomechanical loading based on this in vitro study. CLINICAL RELEVANCE: Lengthening of the radius beyond native variance in the setting of ulnar impaction syndrome, distal radius malunion, or distal radioulnar instability may not result in excessive loading of the distal radius and further reduces loading on the distal ulna. Surgeons should obtain contralateral wrist x-rays to serve as a template when performing distal radius osteotomies.

16.
J Wrist Surg ; 8(2): 124-131, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30941252

RESUMO

Background The scapholunate ligament (SLL) is the most commonly injured intercarpal ligament of the wrist. It is the primary stabilizer of the scapholunate (SL) joint, but the scaphotrapeziotrapezoid (STT) and radioscaphocapitate (RSC) ligaments may also contribute to SL stability. The contributions of SL joint stabilizers have been reported previously; however, this study aims to examine their contributions to SL stability using a different methodology than previous studies. Purpose The purpose of this in vitro biomechanical study was to quantify changes in SL kinematics during wrist flexion and extension following a previously untested sequential sectioning series of the SL ligament and secondary stabilizers. Methods Eight cadaveric upper extremities underwent active wrist flexion and extension in a custom motion wrist simulator. SL kinematics were captured with respect to the distal radius. A five-stage sequential sectioning protocol was performed, with data analyzed from 45-degree wrist flexion to 45-degree wrist extension. Results Wrist flexion and extension caused the lunate to adopt a more extended posture following sectioning of the SLL and secondary stabilizers compared with the intact state ( p < 0.009). The isolated disruption to the dorsal portion of the SLL did not result in significant change in lunate kinematics compared with the intact state ( p > 0.05). Scaphoid kinematics were altered in wrist flexion following sequential sectioning ( p = 0.013). Additionally, disruption of the primary and secondary stabilizers caused significant change to SL motion in both wrist flexion and wrist extension ( p < 0.03). Conclusions The SLL is the primary stabilizer of the SL articulation, with the STT and RSC ligaments playing secondary stabilization roles. Clinical Relevance Understanding the role primary and secondary SL joint stabilizers may assist in the development of more effective treatment strategies and patient outcomes following SLL injuries.

17.
J Shoulder Elbow Surg ; 28(5): 974-981, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30723030

RESUMO

BACKGROUND: The role of the anconeus in elbow stability has been a long-standing debate. Anatomic and electromyographic studies have suggested a potential role as a stabilizer. However, to our knowledge, no clinical or biomechanical studies have investigated its role in improving the stability of a combined lateral collateral ligament and common extensor origin (LCL + CEO)-deficient elbow. METHODS: Seven cadaveric upper extremities were mounted in an elbow motion simulator in the varus position. An injured model was created by sectioning of the CEO and the LCL. The anconeus tendon and its aponeurosis were sutured in a Krackow fashion and tensioned to 10 N and 20 N using a transosseous tunnel. Varus-valgus angles and ulnohumeral rotations were recorded using an electromagnetic tracking system during simulated active elbow flexion with the forearm pronated and supinated. RESULTS: During active motion, the injured model resulted in a significant increase in varus angulation (P = .0001 for pronation; P = .001 for supination) and external rotation (P = .001 for pronation; P = .003 for supination) of the ulnohumeral articulation compared with the intact state. Tensioning of the anconeus significantly decreased the varus angulation (P = .006 for 10 N pronation; P = .0001 for 20 N pronation; P = .0001 for 10 N supination; P = .0001 for 20 N supination) and external rotation angle (P = .008 for 10 N pronation; P = .0001 for 20 N pronation; P = .0001 for 10 N supination; P = .0001 for 20 N supination) of the injured elbow. CONCLUSIONS: In the highly unstable varus elbow orientation, anconeus tensioning restores the in vitro stability of a combined LCL + CEO-deficient elbow during simulated active motion with the forearm in both pronation and supination. These results may have several clinical implications in managing symptomatic lateral elbow instability.


Assuntos
Ligamentos Colaterais/fisiopatologia , Articulação do Cotovelo/fisiopatologia , Instabilidade Articular/etiologia , Idoso , Fenômenos Biomecânicos , Cadáver , Ligamentos Colaterais/patologia , Feminino , Antebraço , Humanos , Instabilidade Articular/fisiopatologia , Masculino , Pessoa de Meia-Idade , Músculo Esquelético , Pronação , Amplitude de Movimento Articular , Supinação
18.
Shoulder Elbow ; 11(1): 45-52, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30719097

RESUMO

Background: Both unlinked and linked total elbow arthroplasty (TEA) implants have been employed with no consensus as to the optimal design. The present study aimed to evaluate the effect of collateral ligament integrity and implant linkage on wear-inducing loads in a convertible TEA. Methods: Eight fresh frozen upper extremities were tested in an elbow motion simulator. A convertible TEA with an instrumented humeral stem was inserted using computer navigation. Elbow kinematics and humeral loading were recorded with the TEA both linked and unlinked. The collateral ligaments were then sectioned and testing was repeated. Results: In the dependent position, there was no effect of implant linkage or ligament sectioning on humeral loading. Humeral loading was significantly greater following sectioning of the collateral ligaments but not after linking the TEA with the arm in the valgus position. Humeral loading was significantly greater after linking the TEA but not after sectioning of the collateral ligaments and with the arm in the varus position. Conclusions: Collateral ligament integrity reduces wear-inducing loads for both an unlinked and linked TEA. Linkage of a convertible TEA increases humeral loading, which may have detrimental effects on implant longevity.

19.
J Biomech Eng ; 141(3)2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30656350

RESUMO

An important feature of humeral orthopedic finite element (FE) models is the trabecular stiffness relationship. These relationships depend on the anatomic site from which they are derived; but have not been developed for the humerus. As a consequence, humeral FE modeling relies on relationships for other anatomic sites. The variation in humeral FE outcomes due to the trabecular stiffness relationship is assessed. Stemless arthroplasty FE models were constructed from CT scans of eight humeri. Models were loaded corresponding to 45 deg and 75 deg abduction. Each bone was modeled five times with the only variable being the trabecular stiffness relationship: four derived from different anatomic-sites and one pooled across sites. The FE outcome measures assessed were implant-bone contact percentage, von Mises of the change in stress, and bone response potential. The variance attributed to the selection of the trabecular stiffness relationship was quantified as the standard deviation existing between models of different trabecular stiffness. Overall, variability due to changing the trabecular stiffness relationship was low for all humeral FE outcome measures assessed. The variability was highest within the stress and bone formation potential outcome measures of the trabecular region. Variability only exceeded 10% in the trabecular stress change within two of the eight slices evaluated. In conclusion, the low variations attributable to the selection of a trabecular stiffness relationship based on anatomic-site suggest that FE models constructed for shoulder arthroplasty can utilize an inhomogeneous site-pooled trabecular relationship without inducing marked variability in the assessed outcome measures.

20.
Arthroscopy ; 35(2): 382-389, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30522801

RESUMO

PURPOSE: To compare the subacromial balloon spacer with superior capsular reconstruction (SCR) for the treatment of massive irreparable rotator cuff tears. METHODS: Eight male cadaveric shoulders were mounted on a custom shoulder simulator that permitted quasistatic deltoid and rotator cuff muscle loading. Four shoulder conditions were tested: intact, irreparable rotator cuff tear (torn), subacromial balloon spacer, and SCR. The primary outcomes were superior humeral head migration and functional shoulder abduction force, which were measured at 0°, 30°, 60°, and 90° of shoulder abduction. RESULTS: In comparison to the intact condition, the torn condition resulted in a significant increase in superior humeral head migration at 0° (P = .03) and 30° (P = .02) of abduction. Insertion of the subacromial balloon spacer restored the humeral head position such that it was not significantly different from the intact condition (P = .18). Similarly, SCR restored the humeral head position such that it was not significantly different from the intact condition (P = .99). No significant differences were found between the balloon and SCR (P = .99). The functional abduction force was significantly decreased after tear creation (P = .01); however, the subacromial balloon (P = .40) and SCR (P = .99) restored functional abduction force comparable to the intact shoulder state. CONCLUSIONS: On the basis of the results, both techniques function to decrease superior humeral head migration and to restore more normal glenohumeral joint position and forces during various abduction positions. No substantial differences were identified between techniques at time zero. CLINICAL RELEVANCE: The results of this laboratory study indicate that the balloon and SCR both provided mechanical effects that restored the humeral head position from the superiorly migrated location. As such, similar clinical effects can be expected at time zero in patients with massive rotator cuff tears.


Assuntos
Procedimentos Ortopédicos/instrumentação , Lesões do Manguito Rotador/cirurgia , Idoso , Fenômenos Biomecânicos , Cadáver , Humanos , Masculino , Pessoa de Meia-Idade , Articulação do Ombro/fisiologia , Articulação do Ombro/cirurgia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA