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Assessing physical activity is important in the treatment of chronic conditions, including chronic low back pain (cLBP). ActiGraph™, a widely used physical activity monitor, collects raw acceleration data, and processes these data through proprietary algorithms to produce physical activity measures. The purpose of this study was to replicate ActiGraph™ algorithms in MATLAB and test the validity of this method with both healthy controls and participants with cLBP. MATLAB code was developed to replicate ActiGraph™'s activity counts and step counts algorithms, to sum the activity counts into counts per minute (CPM), and categorize each minute into activity intensity cut points. A free-living validation was performed where 24 individuals, 12 cLBP and 12 healthy, wore an ActiGraph™ GT9X on their non-dominant hip for up to seven days. The raw acceleration data were processed in both ActiLife™ (v6), ActiGraph™'s data analysis software platform, and through MATLAB (2022a). Percent errors between methods for all 24 participants, as well as separated by cLBP and healthy, were all less than 2%. ActiGraph™ algorithms were replicated and validated for both populations, based on minimal error differences between ActiLife™ and MATLAB, allowing researchers to analyze data from any accelerometer in a manner comparable to ActiLife™.
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Algoritmos , Exercício Físico , Dor Lombar , Humanos , Dor Lombar/fisiopatologia , Dor Lombar/diagnóstico , Exercício Físico/fisiologia , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Actigrafia/métodos , Actigrafia/instrumentação , Acelerometria/métodos , Acelerometria/instrumentação , Dor Crônica/fisiopatologia , Dor Crônica/diagnóstico , Estudos de Casos e ControlesRESUMO
OBJECTIVE: Biomechanics represents the common final output through which all biopsychosocial constructs of back pain must pass, making it a rich target for phenotyping. To exploit this feature, several sites within the NIH Back Pain Consortium (BACPAC) have developed biomechanics measurement and phenotyping tools. The overall aims of this article were to: 1) provide a narrative review of biomechanics as a phenotyping tool; 2) describe the diverse array of tools and outcome measures that exist within BACPAC; and 3) highlight how leveraging these technologies with the other data collected within BACPAC could elucidate the relationship between biomechanics and other metrics used to characterize low back pain (LBP). METHODS: The narrative review highlights how biomechanical outcomes can discriminate between those with and without LBP, as well as among levels of severity of LBP. It also addresses how biomechanical outcomes track with functional improvements in LBP. Additionally, we present the clinical use case for biomechanical outcome measures that can be met via emerging technologies. RESULTS: To answer the need for measuring biomechanical performance, our "Results" section describes the spectrum of technologies that have been developed and are being used within BACPAC. CONCLUSION AND FUTURE DIRECTIONS: The outcome measures collected by these technologies will be an integral part of longitudinal and cross-sectional studies conducted in BACPAC. Linking these measures with other biopsychosocial data collected within BACPAC increases our potential to use biomechanics as a tool for understanding the mechanisms of LBP, phenotyping unique LBP subgroups, and matching these individuals with an appropriate treatment paradigm.
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Dor Lombar , Humanos , Dor Lombar/diagnóstico , Estudos Transversais , Fenômenos Biomecânicos , Literatura de Revisão como AssuntoRESUMO
As a member of the Back Pain Consortium (BACPAC), the University of Pittsburgh Mechanistic Research Center's research goal is to phenotype chronic low back pain using biological, biomechanical, and behavioral domains using a prospective, observational cohort study. Data will be collected from 1,000 participants with chronic low back pain according to BACPAC-wide harmonized and study-specific protocols. Participation lasts 12 months with one required in person baseline visit, an optional second in person visit for advanced biomechanical assessment, and electronic follow ups at months 1, 2, 3, 4, 5, 6, 9, and 12 to assess low back pain status and response to prescribed treatments. Behavioral data analysis includes a battery of patient-reported outcomes, social determinants of health, quantitative sensory testing, and physical activity. Biological data analysis includes omics generated from blood, saliva, and spine tissue. Biomechanical data analysis includes a physical examination, lumbopelvic kinematics, and intervertebral kinematics. The statistical analysis includes traditional unsupervised machine learning approaches to categorize participants into groups and determine the variables that differentiate patients. Additional analysis includes the creation of a series of decision rules based on baseline measures and treatment pathways as inputs to predict clinical outcomes. The characteristics identified will contribute to future studies to assist clinicians in designing a personalized, optimal treatment approach for each patient.
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Dor Lombar , Humanos , Dor Lombar/diagnóstico , Dor Lombar/terapia , Estudos de Coortes , Estudos Prospectivos , Dor nas Costas , Fenótipo , Estudos Observacionais como AssuntoRESUMO
Rehabilitation has been shown to improve functional outcomes following total knee replacement (TKR). However, its delivery and associated costs are highly variable. The authors have developed and previously validated the accuracy of a remote (wearable) rehabilitation monitoring platform (interACTION). The present study's objective was to assess the feasibility of utilizing interACTION for the remote management of rehabilitation after TKR and to determine a preliminary estimate of the effects of the interACTION system on the value of rehabilitation. Specifically, we tested post-operative outpatient rehabilitation supplemented with interACTION (n = 13) by comparing it to a standard post-operative outpatient rehabilitation program (n = 12) using a randomized design. Attrition rates were relatively low and not significantly different between groups, indicating that participants found both interventions acceptable. A small (not statistically significant) decrease in the number of physical therapy visits was observed in the interACTION Group, therefore no significant difference in total cost could be observed. All patients and physical therapists in the interACTION Group indicated that they would use the system again in the future. Therefore, the next steps are to address the concerns identified in this pilot study and to expand the platform to include behavioral change strategies prior to conducting a full-scale randomized controlled trial. Trial registration: ClinicalTrials.gov NCT02646761 "interACTION: A Portable Joint Function Monitoring and Training System for Remote Rehabilitation Following TKA" 6 January 2016.
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Artroplastia do Joelho/reabilitação , Modalidades de Fisioterapia , Telerreabilitação , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Resultado do TratamentoRESUMO
Rehabilitation following knee injury or surgery is critical for recovery of function and independence. However, patient non-adherence remains a significant barrier to success. Remote rehabilitation using mobile health (mHealth) technologies have potential for improving adherence to and execution of home exercise. We developed a remote rehabilitation management system combining two wireless inertial measurement units (IMUs) with an interactive mobile application and a web-based clinician portal (interACTION). However, in order to translate interACTION into the clinical setting, it was first necessary to verify the efficacy of measuring knee motion during rehabilitation exercises for physical therapy and determine if visual feedback significantly improves the participant's ability to perform the exercises correctly. Therefore, the aim of this study was to verify the accuracy of the IMU-based knee angle measurement system during three common physical therapy exercises, quantify the effect of visual feedback on exercise performance, and understand the qualitative experience of the user interface through survey data. A convenience sample of ten healthy control participants were recruited for an IRB-approved protocol. Using the interACTION application in a controlled laboratory environment, participants performed ten repetitions of three knee rehabilitation exercises: heel slides, short arc quadriceps contractions, and sit-to-stand. The heel slide exercise was completed without feedback from the mobile application, then all exercises were performed with visual feedback. Exercises were recorded simultaneously by the IMU motion tracking sensors and a video-based motion tracking system. Validation showed moderate to good agreement between the two systems for all exercises and accuracy was within three degrees. Based on custom usability survey results, interACTION was well received. Overall, this study demonstrated the potential of interACTION to measure range of motion during rehabilitation exercises for physical therapy and visual feedback significantly improved the participant's ability to perform the exercises correctly.
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Articulação do Joelho/fisiopatologia , Sistemas de Identificação de Pacientes/métodos , Reabilitação/instrumentação , Reabilitação/métodos , Telerreabilitação/instrumentação , Telerreabilitação/métodos , Tecnologia sem Fio/instrumentação , Adulto , Exercício Físico/fisiologia , Terapia por Exercício/instrumentação , Terapia por Exercício/métodos , Retroalimentação , Feminino , Humanos , Masculino , Aplicativos Móveis , Amplitude de Movimento Articular/fisiologia , Adulto JovemRESUMO
PURPOSE: To quantify the mechanical role of posterior column components in human cervical spine segments. METHODS: Twelve C6-7 segments were subjected to resection of (1) suprasinous/interspinous ligaments (SSL/ISL), (2) ligamenta flavum (LF), (3) facet capsules, and (4) facets. A robot-based testing system performed repeated flexibility testing of flexion-extension (FE), axial rotation (AR), and lateral bending (LB) to 2.5Nm and replayed kinematics from intact flexibility tests for each state. Range-of-motion, stiffness, moment resistance and resultant forces were calculated. RESULTS: The LF contributes largely to moment resistance, particularly in flexion. Facet joints were primary contributors to AR and LB mechanics. Moment/force responses were more sensitive and precise than kinematic outcomes. CONCLUSIONS: The LF is mechanically important in the cervical spine; its injury could negatively impact load distribution. Damage to facets in a flexion injury could lead to AR or LB hypermobility. Quantifying the contribution of spinal structures to moment resistance is a sensitive, precise process for characterizing structural mechanics.
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Vértebras Cervicais/fisiologia , Ligamento Amarelo/fisiologia , Amplitude de Movimento Articular/fisiologia , Articulação Zigapofisária/fisiologia , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Ligamentos Articulares/fisiologia , Masculino , Pessoa de Meia-Idade , RotaçãoRESUMO
STUDY DESIGN: An in vitro biomechanical study for rabbit lumbar functional spinal units (FSUs) using a robot-based spine testing system. OBJECTIVE: To elucidate the effect of annular puncture with a 16 G needle on mechanical properties in flexion/extension, axial rotation, and lateral bending. SUMMARY OF BACKGROUND DATA: Needle puncture of the intervertebral disk has been shown to alter mechanical properties of the disk in compression, torsion, and bending. The effect of needle puncture in FSUs, where intact spinal ligaments and facet joints may mitigate or amplify these changes in the disk, on spinal motion segment stability subject to physiological rotations remains unknown. METHODS: Rabbit FSUs were tested using a robot testing system whose force/moment and position precision were assessed to demonstrate system capability. Flexibility testing methods were developed by load-to-failure testing in flexion/extension, axial rotation, and lateral bending. Subsequent testing methods were used to examine a 16 G needle disk puncture and No. 11 blade disk stab (positive control for mechanical disruption). Flexibility testing was used to assess segmental range-of-motion (degrees), neutral zone stiffness (N m/degrees) and width (degrees and N m), and elastic zone stiffness before and after annular injury. RESULTS: The robot-based system was capable of performing flexibility testing on FSUs-mean precision of force/moment measurements and robot system movements were <3% and 1%, respectively, of moment-rotation target values. Flexibility moment targets were 0.3 N m for flexion and axial rotation and 0.15 N m for extension and lateral bending. Needle puncture caused significant (P<0.05) changes only in flexion/extension range-of-motion and neutral zone stiffness and width (N m) compared with preintervention. No. 11 blade-stab significantly increased range-of-motion in all motions, decreased neutral zone stiffness and width (N m) in flexion/extension, and increased elastic zone stiffness in flexion and lateral bending. CONCLUSIONS: These findings suggest that disk puncture and stab can destabilize FSUs in primary rotations.
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Vértebras Lombares/fisiologia , Vértebras Lombares/cirurgia , Agulhas , Punções , Animais , Fenômenos Biomecânicos , Feminino , Técnicas In Vitro , Disco Intervertebral/fisiologia , Coelhos , Amplitude de Movimento Articular , Rotação , Articulação Zigapofisária/fisiologia , Articulação Zigapofisária/cirurgiaRESUMO
Background: Previous animal models of intervertebral disc degeneration (IDD) rely on open surgical approaches, which confound the degenerative response and pain behaviors due to injury to surrounding tissues during the surgical approach. To overcome these challenges, we developed a minimally invasive percutaneous puncture procedure to induce IDD in a rat model. Methods: Ten Fischer 344 male rats underwent percutaneous annular puncture of lumbar intervertebral discs (IVDs) at L2-3, L3-4, and L4-5. Ten unpunctured rats were used as controls. Magnetic resonance imagings (MRIs), serum biomarkers, and behavioral tests were performed at baseline and 6, 12, and 18 weeks post puncture. Rats were sacrificed at 18 weeks and disc histology, immunohistochemistry, and glycosaminoglycan (GAG) assays were performed. Results: Punctured IVDs exhibited significant reductions in MRI signal intensity and disc volume. Disc histology, immunohistochemistry, and GAG assay results were consistent with features of IDD. IVD-punctured rats demonstrated significant changes in pain-related behaviors, including total distance moved, twitching frequency, and rearing duration. Conclusions: This is the first reported study of the successful establishment of a reproducible rodent model of a percutaneous lumbar annular puncture resulting in discogenic pain. This model will be useful to test therapeutics and elucidate the basic mechanisms of IDD and discogenic pain.
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BACKGROUND: Pediatric and adolescent athletes are a large demographic undergoing anterior cruciate ligament reconstruction (ACL-R). Postoperative rehabilitation is critical, requiring patients to complete home exercise programs (HEPs). To address obstacles to HEP adherence, we developed an interactive health technology, interACTION (iA), to monitor knee-specific rehabilitation. iA is a web-based platform that incorporates wearable motion sensors and a mobile app that provides feedback and allows remote monitoring. The Wheel of Sukr is a gamification mechanism that includes numerous behavioral elements. OBJECTIVE: This study aims to use a user-centered design process to incorporate behavioral change strategies derived from self-management theory into iA using the Wheel of Sukr, with the aim of influencing patient behavior. METHODS: In total, 10 athletes aged 10-18 years with a history of ACL-R were included in this study. Patients were between 4 weeks and 1 year post-ACL-R. Participants underwent a 60-minute triphasic interview. Phase 1 focused on elements of gaming that led to high participation and information regarding surgery and recovery. In phase 2, participants were asked to think aloud and rank cards representing the components of the Wheel of Sukr in order of interest. In phase 3, the patients reviewed the current version of iA. Interviews were recorded, transcribed, and checked for accuracy. Qualitative content analysis segmented the data and tagged meaningful codes until descriptive redundancy was achieved; next, 2 coders independently coded the data set. These elements were categorized according to the Wheel of Sukr framework. The mean age of participants was 12.8 (SD 1.32) years, and 70% (7/10) were female. Most participants (7/10, 70%) reported attending sessions twice weekly. All patients were prescribed home exercises. Self-reported HEP compliance was 75%-100% in 40% (4/10), 50%-75% in 40% (4/10), and 25%-50% of prescribed exercises in 20% (2/10) of the participants. RESULTS: The participants responded positively to an app that could track home exercises. Desirable features included exercise demonstrations, motivational components, and convenience. The participants listed sports specificity, competition, notifications, reminders, rewards, and social aspects of gameplay as features to incorporate. In the Wheel of Sukr card sort exercise, motivation was ranked first; self-management, second; and growth, esteem, and fun tied for the third position. The recommended gameplay components closely followed the themes from the Wheel of Sukr card sort activity. CONCLUSIONS: The participants believe iA is a helpful addition to recovery and want the app to include exercise movement tracking and encouragement. Despite the small number of participants, thematic saturation was reached, suggesting the sample was sufficient to obtain a representative range of perspectives. Future work will implement motivation; self-management; and growth, confidence, and fun in the iA user experience. Young athlete ACL-R patients will complete typical clinical scenarios using increasingly developed prototypes of the gamified iA in a controlled setting.
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In vitro biomechanical studies of the osteoligamentous spine are widely used to characterize normal biomechanics, identify injury mechanisms, and assess the effects of degeneration and surgical instrumentation on spine mechanics. The objective of this study was to determine how well four standards in vitro loading paradigms replicate in vivo kinematics with regards to the instantaneous center of rotation and arthrokinematics in relation to disc deformation. In vivo data were previously collected from 20 asymptomatic participants (45.5 ± 5.8 years) who performed full range of motion neck flexion-extension (FE) within a biplane x-ray system. Intervertebral kinematics were determined with sub-millimeter precision using a validated model-based tracking process. Ten cadaveric spines (51.8 ± 7.3 years) were tested in FE within a robotic testing system. Each specimen was tested under four loading conditions: pure moment, axial loading, follower loading, and combined loading. The in vivo and in vitro bone motion data were directly compared. The average in vitro instant center of rotation was significantly more anterior in all four loading paradigms for all levels. In general, the anterior and posterior disc heights were larger in the in vitro models than in vivo. However, after adjusting for gender, the observed differences in disc height were not statistically significant. This data suggests that in vitro biomechanical testing alone may fail to replicate in vivo conditions, with significant implications for novel motion preservation devices such as cervical disc arthroplasty implants.
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Vértebras Cervicais/fisiologia , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Disco Intervertebral/fisiologia , Masculino , Pessoa de Meia-Idade , Amplitude de Movimento Articular , RotaçãoRESUMO
The human cervical spine supports substantial compressive load in vivo. However, the traditional in vitro testing methods rarely include compressive loads, especially in investigations of multi-segment cervical spine constructs. Previously, a systematic comparison was performed between the standard pure moment with no compressive loading and published compressive loading techniques (follower load - FL, axial load - AL, and combined load - CL). The systematic comparison was structured a priori using a statistical design of experiments and the desirability function approach, which was chosen based on the goal of determining the optimal compressive loading parameters necessary to mimic the segmental contribution patterns exhibited in vivo. The optimized set of compressive loading parameters resulted in in vitro segmental rotations that were within one standard deviation and 10% of average percent error of the in vivo mean throughout the entire motion path. As hypothesized, the values for the optimized independent variables of FL and AL varied dynamically throughout the motion path. FL was not necessary at the extremes of the flexion-extension (FE) motion path but peaked through the neutral position, whereas, a large negative value of AL was necessary in extension and increased linearly to a large positive value in flexion. Although further validation is required, the long-term goal is to develop a "physiologic" in vitro testing method, which will be valuable for evaluating adjacent segment effect following spinal fusion surgery, disc arthroplasty instrumentation testing and design, as well as mechanobiology experiments where correct kinematics and arthrokinematics are critical.
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Vértebras Cervicais/fisiologia , Modelos Biológicos , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pressão , Amplitude de Movimento ArticularRESUMO
STUDY DESIGN: In vitro biomechanical analysis. OBJECTIVES: Compare the destabilizing effects of anterior discectomy to posterior spinal releases. SUMMARY OF BACKGROUND DATA: Posterior release and pedicle screw fixation has become the accepted form of treatment for lumbar and thoracolumbar pediatric scoliotic spinal deformity. A biomechanical evaluation of posterior releases with comparison to traditional anterior releases has not been reported in the lumbar spine. METHODS: Eleven fresh-frozen human thoracolumbar specimens (T9-L5) were tested by a robotic manipulator (Staubli RX90; moment target of 5.0 Nm, force target of 50 N) in axial rotation (AR), plus lateral and anterior translation (LT and AT). Specimens underwent either sequential anterior release (partial and full discectomy) or posterior release (inferior facetectomy and wide posterior release) from T10 to L4. Partial discectomy retained the posterior 50% of disc and posterior longitudinal ligament, whereas full discectomy removed all of the disc and PLL. Wide posterior release included total facetectomy plus ligamentum flavum and spinous process resection. RESULTS: Inferior facetectomy produced an average increase of 1.5° ± 1.0° (p = .0625), 1.0 ± 0.8 mm (p = .0313), and 0.2 ± 0.3 mm (p = .156) in AR, LT, and AT, respectively. Compared with partial facetectomy, wide posterior release produced an average additional increase of 8.1° ± 4.0° (p = .0312), 2.0 ± 2.2 mm (p = .4062), and 1.1 ± 1.0 mm (p = .0625) in AR, LT, and AT, respectively. Full discectomy produced 201%, 161%, and 153% of the motion relative to wide posterior release in AR, LT, and AT, respectively (p = .0043, .0087, and .0173). Partial discectomy and wide posterior release proved statistically equivalent. CONCLUSIONS: Wide posterior release of the thoracolumbar spine allows significant correction and may be superior to inferior facetectomy in axial rotation. Although complete discectomy with PLL resection would likely allow greater correction, a more clinically realistic partial discectomy confers similar corrective potential in vitro compared with wide posterior release. LEVEL OF EVIDENCE: Not applicable.
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Discotomia/métodos , Vértebras Lombares , Amplitude de Movimento Articular/fisiologia , Vértebras Torácicas , Idoso , Fenômenos Biomecânicos , Feminino , Humanos , Vértebras Lombares/fisiologia , Vértebras Lombares/cirurgia , Masculino , Pessoa de Meia-Idade , Procedimentos Ortopédicos/métodos , Vértebras Torácicas/fisiologia , Vértebras Torácicas/cirurgiaRESUMO
The existence of a ligamentous structure within the anterolateral capsule, which can be injured in combination with the anterior cruciate ligament, has been debated. Therefore, the purpose of this study was to determine the magnitude and direction of the strain in the anterolateral capsule in response to external loads applied to the knee. The anterolateral capsule was hypothesized to not function like a traditional ligament. A 6-degree-of-freedom robotic testing system was used to apply ten external loads to human cadaveric knees (n = 7) in the intact and anterior cruciate ligament (ACL) deficient states. The position of strain markers was recorded on the midsubstance of the anterolateral capsule during the resulting joint kinematics to determine the magnitude and direction of the maximum principal strain. The peak maximum principal strain ranged from 22% to 52% depending on the loading condition. When histograms of strain magnitude values were analyzed to determine strain uniformity, the mean kurtosis was 1.296 ± 0.955, lower than a typical ligament, and the mean variance was 0.015 ± 0.008, higher than a typical ligament. The mean angles of the strain direction vectors compared to the proposed ligament ranged between 38° and 130° (p < 0.05). The magnitude of the maximum principal strain in the anterolateral capsule is much larger than a typical ligament and does not demonstrate a uniform strain distribution. The direction of strain is also not aligned with the proposed ligament. Clinical Significance: Reconstruction methods using tendons will not produce normal joint function due to replacement of a multi-axial structure with a uni-axial structure. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
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Lesões do Ligamento Cruzado Anterior/fisiopatologia , Articulação do Joelho/fisiologia , Humanos , Pessoa de Meia-Idade , Estresse MecânicoRESUMO
BACKGROUND: Double bundle ACL reconstruction has been demonstrated to decrease rotational knee laxity. However, there is no simple, commercially-available device to measure knee rotation. The investigators developed a simple, non-invasive device to measure knee rotation. In conjunction with a rigid boot to rotate the tibia and a force/moment sensor to allow precise determination of torque about the knee, a magnetic tracking system measures the axial rotation of the tibia with respect to the femur. This device has been shown to have acceptable levels of test re-test reliability to measure knee rotation in cadaveric knees. METHODS: The objective of this study was to determine reliability of the device in measuring knee rotation of human subjects. Specifically, the intra-tester reliability within a single testing session, test-retest reliability between two testing sessions, and inter-tester reliability were assessed for 11 male subjects with normal knees. RESULTS: The 95% confidence interval for rotation was less than 5 degrees for intra-tester, test-retest, and inter-tester reliability, and the standard error of measurement for the differences between left and right knees was found to be less than 3 degrees . CONCLUSION: It was found that the knee rotation measurements obtained with this device have acceptable limits of reliability for clinical use and interpretation.
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Artrometria Articular/instrumentação , Articulação do Joelho/fisiologia , Magnetismo/instrumentação , Adulto , Ligamento Cruzado Anterior/fisiologia , Artrometria Articular/métodos , Fenômenos Biomecânicos , Gráficos por Computador , Desenho de Equipamento , Fêmur/fisiologia , Humanos , Masculino , Variações Dependentes do Observador , Amplitude de Movimento Articular , Valores de Referência , Reprodutibilidade dos Testes , Rotação , Tíbia/fisiologia , TorqueRESUMO
In-vitro biomechanical testing is widely performed for characterizing the load-displacement characteristics of intact, injured, degenerated, and surgically repaired osteoligamentous spine specimens. Traditional specimen fixture devices offer an unspecified rigidity of fixation, while varying in the associated amounts and reversibility of damage to and "coverage" of a specimen - factors that can limit surgical access to structures of interest during testing as well as preclude the possibility of testing certain segments of a specimen. Therefore, the objective of this study was to develop a specimen fixture system for spine biomechanical testing that uses components of clinically available spinal fixation hardware and determine whether the new system provides sufficient rigidity for spine biomechanical testing. Custom testing blocks were mounted into a robotic testing system and the angular deflection of the upper fixture was measured indirectly using linear variable differential transformers. The fixture system had an overall stiffness 37.0, 16.7 and 13.3 times greater than a typical human functional spine unit for the flexion/extension, axial rotation and lateral bending directions respectively - sufficient rigidity for biomechanical testing. Fixture motion when mounted to a lumbar spine specimen revealed average motion of 0.6, 0.6, and 1.5° in each direction. This specimen fixture method causes only minimal damage to a specimen, permits testing of all levels of a specimen, and provides for surgical access during testing.
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Vértebras Lombares/fisiologia , Teste de Materiais/instrumentação , Fenômenos Mecânicos , Fenômenos Biomecânicos , Humanos , Amplitude de Movimento Articular , RotaçãoRESUMO
The objective of this study was to implement a follower load (FL) device within a robotic (universal force-moment sensor) testing system and utilize the system to explore the effect of FL on multi-segment cervical spine moment-rotation parameters and intradiscal pressure (IDP) at C45 and C56. Twelve fresh-frozen human cervical specimens (C3-C7) were biomechanically tested in a robotic testing system to a pure moment target of 2.0â¯Nm for flexion and extension (FE) with no compression and with 100â¯N of FL. Application of FL was accomplished by loading the specimens with bilateral cables passing through cable guides inserted into the vertebral bodies and attached to load controlled linear actuators. FL significantly increased neutral zone (NZ) stiffness and NZ width but resulted in no change in the range of motion (ROM) or elastic zone stiffness. C45 and C56 IDP measured in the neutral position were significantly increased with application of FL. The change in IDP with increasing flexion rotation was not significantly affected by the application of FL, whereas the change in IDP with increasing extension rotation was significantly reduced by the application of FL. Application of FL did not appear to affect the specimen's quantity of motion (ROM) but did affect the quality (the shape of the curve). Regarding IDP, the effects of adding FL compression approximates the effect of the patient going from supine to a seated position (FL compression increased the IDP in the neutral position). The change in IDP with increasing flexion rotation was not affected by the application of FL, but the change in IDP with increasing extension rotation was, however, significantly reduced by the application of FL.
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Vértebras Cervicais/fisiologia , Disco Intervertebral/fisiologia , Adulto , Fenômenos Biomecânicos , Humanos , Pessoa de Meia-Idade , Pressão , Amplitude de Movimento Articular , Robótica , Rotação , Suporte de CargaRESUMO
The role of the anterolateral capsule complex in knee rotatory stability remains controversial. Therefore, the objective of this study was to determine the in situ forces in the anterior cruciate ligament (ACL), the anterolateral capsule, the lateral collateral ligament (LCL), and the forces transmitted between each region of the anterolateral capsule in response to a simulated pivot shift test. A robotic testing system applied a simulated pivot shift test continuously from full extension to 90° of flexion to intact cadaveric knees (n = 7). To determine the magnitude of the in situ forces, kinematics of the intact knee were replayed in position control mode after the following procedures were performed: (i) ACL transection; (ii) capsule separation; (iii) anterolateral capsule transection; and (iii) LCL transection. A repeated measures ANOVA was performed to compare in situ forces between each knee state (*p < 0.05). The in situ force in the ACL was significantly greater than the forces transmitted between each region of the anterolateral capsule at 5° and 15° of flexion but significantly lower at 60°, 75°, and 90° of flexion. This study demonstrated that the ACL is the primary rotatory stabilizer at low flexion angles during a simulated pivot shift test in the intact knee, but the anterolateral capsule plays an important secondary role at flexion angles greater than 60°. Furthermore, the contribution of the "anterolateral ligament" to rotatory knee stability in this study was negligible during a simulated pivot shift test. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:847-853, 2018.
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Ligamento Cruzado Anterior/fisiologia , Ligamentos Colaterais/fisiologia , Articulação do Joelho/fisiologia , Fenômenos Biomecânicos , Humanos , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Physical exams that apply anterior tibial loads are typically used to evaluate knees with anterior cruciate ligament (ACL) injuries. The amount of anterior tibial translation that occurs during these exams can be difficult to assess due to a "soft" endpoint. Therefore, the objective of this study is to determine the biomechanical characteristics of the endpoint for the intact and ACL deficient knee using quantitative criteria. METHODS: Eight porcine knees were tested using a robotic testing system. An 89N anterior tibial load was applied to the intact and ACL deficient knee at 30°, 45°, 60° and 75° of flexion. The stiffness of the toe and linear regions was determined from the load-translation curve. The width of the transition region was defined by the distance between the points where the best-fit lines used to define the stiffness of the toe and linear regions diverged from the load-translation curve. RESULTS: Stiffness of the toe and linear regions significantly decreased after transecting the ACL at all flexion angles (71-85% and 38-62%, respectively). Width of the transition region was significantly increased in the ACL deficient knee at all flexion angles (approximately four to five times and four to nine times, respectively). CONCLUSIONS: The novel quantitative criteria developed in this study have the potential to be deployed in clinical practice by coupling them with data from knee arthrometers that are commonly used in clinical practice. Thus, additional information from the load-translation curve can be provided to improve the diagnosis of ACL injury.
Assuntos
Lesões do Ligamento Cruzado Anterior/diagnóstico , Lesões do Ligamento Cruzado Anterior/fisiopatologia , Articulação do Joelho/fisiopatologia , Animais , Fenômenos Biomecânicos , Fêmur/fisiopatologia , Modelos Animais , Exame Físico , Robótica , Suínos , Tíbia/fisiopatologiaRESUMO
BACKGROUND: The "gold standard" treatment of anterolateral capsular injuries in anterior cruciate ligament (ACL)-deficient knees has not been determined. The purpose of this study was to determine the effects of ACL reconstruction and extra-articular reconstruction on joint motion in the ACL-deficient knee and in the combined ACL and anterolateral capsule-deficient knee. METHODS: An anterior tibial load of 134 N and internal tibial torque of 7 Nm were applied to 7 fresh-frozen cadaveric knees using a robotic testing system continuously throughout the range of flexion. The resulting joint motion was recorded for 6 knee states: intact, ACL-deficient, ACL-reconstructed, combined ACL and anterolateral capsule-deficient, ACL-reconstructed + anterolateral capsule-deficient, and ACL-reconstructed + extra-articular tenodesis. RESULTS: Anterior tibial translation of the ACL-reconstructed + anterolateral capsule-deficient knee in response to an anterior tibial load was restored to that of the intact knee at all knee-flexion angles (p > 0.05). However, for this knee state, internal tibial rotation in response to internal tibial torque was not restored to that of the intact knee at 60° or 90° of knee flexion (p < 0.05). For the knee state of ACL-reconstructed + extra-articular tenodesis, internal rotation in response to internal tibial torque was restored to the motion of the intact knee at each of the tested knee-flexion angles (p > 0.05). Compared with the intact knee, 2 of 7 specimens showed decreased internal tibial rotation with ACL reconstruction + extra-articular tenodesis. CONCLUSIONS: In this study, an extra-articular tenodesis was necessary to restore rotatory knee stability in response to internal tibial torque in a combined ACL and anterolateral capsule-deficient knee. The amount of rotatory knee instability should be carefully assessed to avoid over-constraint of the knee in these combined ligament-reconstruction procedures. CLINICAL RELEVANCE: On the basis of our findings, the surgical procedure needs to be personalized depending on the amount of rotatory knee instability in the injured knee and the amount of rotation in the contralateral knee.
Assuntos
Lesões do Ligamento Cruzado Anterior/cirurgia , Reconstrução do Ligamento Cruzado Anterior/métodos , Cápsula Articular/lesões , Traumatismos do Joelho/cirurgia , Tenodese/métodos , Lesões do Ligamento Cruzado Anterior/complicações , Cadáver , Humanos , Traumatismos do Joelho/complicações , Pessoa de Meia-Idade , Amplitude de Movimento ArticularRESUMO
STUDY DESIGN: Biomechanical testing of partially nucleotomized ovine cadaveric spines. OBJECTIVE: To explore how the nucleus pulposus (NP) affects the biomechanical behavior of the intervertebral disc (IVD) by performing a partial nucleotomy via the transpedicular approach. SUMMARY OF BACKGROUND DATA: Mechanical loading represents a crucial part of IVD homeostasis. However, traditional regenerative strategies require violation of the annulus fibrosus (AF) resulting in significant alteration of joint mechanics. The transpedicular nucleotomy represents a suitable method to create a cavity into the NP, as a model to study IVD regeneration with intact AF. METHODS: A total of 30 ovine-lumbar- functional spinal units (FSUs) (L1-L6) randomly assigned to 5 groups: control; transpedicular tunnel (TT); TT + polymethylmethacrylate (PMMA) to repair the bone tunnel; nucleotomy; nucleotomy + PMMA. Flexion/extension, lateral-bending, and axial-rotation were evaluated under adaptive displacement control. Axial compression was applied for 15 cycles of preconditioning followed by 1 hour of constant compression. Viscoelastic behavior was modeled and parameterized. RESULTS: TT has minimal effects on rotational biomechanics. The nucleotomy increases ROM and neutral zone (NZ) displacement width whereas decreasing NZ stiffness. TT + PMMA has small effects in terms of ROM. Nucleotomy + PMMA brings ROM back to the control, increases NZ stiffness, and decreases NZ displacement width. The nucleotomy tends to increase the rate of early creep. TT reduces early and late damping. The use of PMMA increased late elastic stiffness (S2) and reduced viscous damping (η2) culminating in faster resolution of creep. CONCLUSION: Biomechanical properties of NP are crucial for IVD repair. This study demonstrated that TT does not affect rotational stability whereas partial nucleotomy with intact AF induce rotational instability, highlighting the central role of NP in early stages of IDD. Therefore, this model represents a successful platform to validate and optimize disc regeneration strategies. LEVEL OF EVIDENCE: N/A.