Imaging of exercise-induced spinal remodeling in elite rowers.

OBJECTIVES: As in-vivo knowledge of training-induced remodeling of intervertebral discs (IVD) is scarce, this study assessed how lumbar IVDs change as a function of long-term training in elite athletes and age-matched controls using compositional Magnetic Resonance Imaging (MRI). DESIGN: Prospective case-control study. METHODS: Prospectively, lumbar spines of 17 elite rowers (ERs) of the German national rowing team (mean age: 23.9 ±â€¯3.3 years) were imaged on a clinical 3.0 T MRI scanner. ERs were imaged twice during the annual training cycle, i.e., at training intensive preseason preparations (t0) and 6 months later during post-competition recovery (t1). Controls (n = 22, mean age: 26.3 ±â€¯1.9 years) were imaged once at corresponding time points (t0: n = 11; t1: n = 11). Segment-wise, the glycosaminoglycan (GAG) content of lumbar IVDs (n = 195) was determined using glycosaminoglycan chemical exchange saturation transfer (gagCEST). Linear mixed models were set up to assess the influence of cohort and other variables on GAG content. RESULTS: During preseason, IVD GAG values of ERs were significantly higher than those of controls (ERs(t0): 2.58 ±â€¯0.27% (mean ±â€¯standard deviations); controls(t0): 1.43 ±â€¯0.36%; p ≤ 0.001), while during post-competition recovery, such differences were not present anymore (ERs(t1): 2.11 ±â€¯0.18%; controls(t1): 1.89 ±â€¯0.24%; p = 0.362). CONCLUSIONS: Professional elite-level rowing is transiently associated with significantly higher gagCEST values, which indicate increased lumbar IVD-GAG content and strong remodeling effects in response to training. Beyond professional rowing, core-strengthening full-body exercise may help to enhance the resilience of the lumbar spine as a potential therapeutic target in treating back pain.

Machine learning-augmented and microspectroscopy-informed multiparametric MRI for the non-invasive prediction of articular cartilage composition.

BACKGROUND: Articular cartilage degeneration is the hallmark change of osteoarthritis, a severely disabling disease with high prevalence and considerable socioeconomic and individual burden. Early, potentially reversible cartilage degeneration is characterized by distinct changes in cartilage composition and ultrastructure, while the tissue's morphology remains largely unaltered. Hence, early degenerative changes may not be diagnosed by clinical standard diagnostic tools. METHODS: Against this background, this study introduces a novel method to determine the tissue composition non-invasively. Our method involves quantitative MRI parameters (i.e., T1, T1ρ, T2 and [Formula: see text] maps), compositional reference measurements (i.e., microspectroscopically determined local proteoglycan [PG] and collagen [CO] contents) and machine learning techniques (i.e., artificial neural networks [ANNs] and multivariate linear models [MLMs]) on 17 histologically grossly intact human cartilage samples. RESULTS: Accuracy and precision were higher in ANN-based predictions than in MLM-based predictions and moderate-to-strong correlations were found between measured and predicted compositional parameters. CONCLUSION: Once trained for the clinical setting, advanced machine learning techniques, in particular ANNs, may be used to non-invasively determine compositional features of cartilage based on quantitative MRI parameters with potential implications for the diagnosis of (early) degeneration and for the monitoring of therapeutic outcomes.

Human articular cartilage mechanosensitivity is related to histological degeneration - a functional MRI study.

OBJECTIVE: To investigate changes in response to sequential pressure-controlled loading and unloading in human articular cartilage of variable histological degeneration using serial T1ρ mapping. METHOD: We obtained 42 cartilage samples of variable degeneration from the medial femoral condyles of 42 patients undergoing total knee replacement. Samples were placed in a standardized artificial knee joint within an MRI-compatible whole knee-joint compressive loading device and imaged before (δ0), during (δld1, δld2, δld3, δld4, δld5) and after (δrl1, δrl2, δrl3, δrl4, δrl5) pressure-controlled loading to 0.663 ± 0.021 kN (94% body weight) using serial T1ρ mapping (spin-lock multigradient echo sequence; 3.0T MRI system [Achieva, Philips]). Reference assessment included histology (Mankin scoring) and conventional biomechanics (Tangent stiffness). We dichotomized sample into intact (n = 21) and degenerative (n = 21) based on histology and analyzed data using Mann Whitney, Kruskal Wallis, one-way ANOVA tests and Spearman's correlation, respectively. RESULTS: At δ0, we found no significant differences between intact and degenerative samples, while the response-to-loading patterns were distinctly different. In intact samples, T1ρ increases were consistent and non-significant, while in degenerative samples, T1ρ increases were significantly higher (P = 0.004, δ0 vs δld1, δ0 vs δld3), yet undulating and variable. With unloading, T1ρ increases subsided, yet were persistently elevated beyond δ0. CONCLUSION: Cartilage mechanosensitivity is related to histological degeneration and assessable by serial T1ρ mapping. Unloaded, T1ρ characteristics are not significantly different in intact vs degenerative cartilage, while load bearing is organized in intact cartilage and disorganized in degenerative cartilage.

Multiparametric MRI and Computational Modelling in the Assessment of Human Articular Cartilage Properties: A Comprehensive Approach.

Quantitative magnetic resonance imaging (qMRI) is a promising approach to detect early cartilage degeneration. However, there is no consensus on which cartilage component contributes to the tissue's qMRI signal properties. T1, T1ρ, and T2⁎ maps of cartilage samples (n = 8) were generated on a clinical 3.0-T MRI system. All samples underwent histological assessment to ensure structural integrity. For cross-referencing, a discretized numerical model capturing distinct compositional and structural tissue properties, that is, fluid fraction (FF), proteoglycan (PG) and collagen (CO) content and collagen fiber orientation (CFO), was implemented. In a pixel-wise and region-specific manner (central versus peripheral region), qMRI parameter values and modelled tissue parameters were correlated and quantified in terms of Spearman's correlation coefficient ρs. Significant correlations were found between modelled compositional parameters and T1 and T2⁎, in particular in the central region (T1: ρs ≥ 0.7 [FF, CFO], ρs ≤ -0.8 [CO, PG]; T2⁎: ρs ≥ 0.67 [FF, CFO], ρs ≤ -0.71 [CO, PG]). For T1ρ, correlations were considerably weaker and fewer (0.16 ≤ ρs ≤ -0.15). QMRI parameters are characterized in their biophysical properties and their sensitivity and specificity profiles in a basic scientific context. Although none of these is specific towards any particular cartilage constituent, T1 and T2⁎ reflect actual tissue compositional features more closely than T1ρ.

Non-invasive T1ρ mapping of the human cartilage response to loading and unloading.

OBJECTIVE: To define the physiological response to sequential loading and unloading in histologically intact human articular cartilage using serial T1ρ mapping, as T1ρ is considered to indicate the tissue's macromolecular content. METHOD: 18 macroscopically intact cartilage-bone samples were obtained from the central lateral femoral condyles of 18 patients undergoing total knee replacement. Serial T1ρ mapping was performed on a clinical 3.0-T MRI system using a modified prostate coil. Spin-lock multiple gradient-echo sequences prior to, during and after standardized indentation loading (displacement controlled, strain 20%) were used to obtain seven serial T1ρ maps: unloaded (δ0), quasi-statically loaded (indentation1-indentation3) and under subsequent relaxation (relaxation1-relaxation3). After manual segmentation, zonal and regional regions-of-interest were defined. ROI-specific relative changes were calculated and statistically assessed using paired t-tests. Histological (Mankin classification) and biomechanical (unconfined compression) evaluations served as references. RESULTS: All samples were histologically and biomechanically grossly intact (Mankin sum: 1.8 ± 1.2; Young's Modulus: 0.7 ± 0.4 MPa). Upon loading, T1ρ consistently increased throughout the entire sample thickness, primarily subpistonally (indentation1 [M ± SD]: 9.5 ± 7.8% [sub-pistonal area, SPA] vs 4.2 ± 5.8% [peri-pistonal area, PPA]; P < 0.001). T1ρ further increased with ongoing loading (indentation3: 14.1 ± 8.1 [SPA] vs 7.7 ± 5.9% [PPA]; P < 0.001). Even upon unloading (i.e., relaxation), T1ρ persistently increased in time. CONCLUSION: Serial T1ρ-mapping reveals distinct and complex zonal and regional changes in articular cartilage as a function of loading and unloading. Thereby, longitudinal adaptive processes in hyaline cartilage become evident, which may be used for the tissue's non-invasive functional characterization by T1ρ.

[Chondral and osteochondral defects : Representation by imaging methods]. / Chondrale und osteochondrale Defekte : Darstellung mittels bildgebender Verfahren.

Morphological imaging of cartilage at high resolution allows the differentiation of chondral and osteochondral lesions. Nowadays, magnetic resonance imaging is the principal diagnostic tool in the assessment of cartilage structure and composition. Conventional radiography, computed tomography, ultrasound or optical coherence tomography are adjunct diagnostic modalities in the assessment of cartilage pathologies. The present article discusses the up-to-date diagnostic practice of cartilage imaging in terms of its scientific basis and current clinical status, requirements, techniques and image interpretation. Innovations in the field such as functional MRI are discussed as well due to their mid- to long-term clinical perspective.

[Multidisciplinary Rehabilitation and Fast-track Rehabilitation after Knee Replacement: Faster, Better, Cheaper? A Survey and Systematic Review of Literature]. / Multidisziplinäre Rehabilitation und multimodale Fast-Track-Rehabilitation in der Knieendoprothetik: Schneller, besser, günstiger? Eine Umfrage und systematische Literaturrecherche.

INTRODUCTION: The aim of multidisciplinary rehabilitation after total knee replacement (TKA) is to reduce postoperative complications and costs and enable faster convalescence. The goals of fast-track rehabilitation, as a multidisciplinary concept, are to reduce the length of hospital stay and achieve early functional improvements by optimizing the perioperative setting. METHOD: A literature review was carried out for the years 1960-2013. The search terms were: "rehabilitation", "training", "physiotherapy", "physical therapy", "recovery", "exercise program", "knee surgery", "TKA", "total knee replacement", "arthroplasty", "intensive", "multidisciplinary", "accelerated", "rapid" or "fast track". Only randomized controlled trials and metaanalyses were included. A survey was also performed to assess care as actually offered in orthopaedic rehabilitation clinics in North Rhine-Westphalia. RESULTS: A total of 729 articles were identified of which 11 studies were included. Fast-track rehabilitation can significantly reduce both the duration of hospital stay and costs after TKA. Current studies showed that a better short-/middle-term clinical outcome might be achieved with multidisciplinary rehabilitation. However, a difference in the long-term outcome could not be observed. Our survey shows that most patients are admitted to a rehabilitation clinic in a state of poor general condition as well as decreased mobility and knee range of motion. CONCLUSIONS: Fast-track rehabilitation facilitates a shortened hospital stay as well as cost saving. It probably can be used to optimize the condition of the patient before admission to a rehabilitation facility.

[Tissue engineering of cartilage replacement material - mechanical stimulation in the in-vitro cultivation of human chondrocytes]. / Tissue Engineering von Knorpelersatzgewebe - Mechanische Stimulation in der In-vitro-Kultivierung von humanen Chondrozyten.

The treatment of cartilage defects remains a major problem in orthopaedics. With regard to cartilage tissue engineering, the reimplantation of pre-cultivated chondrocytes in the form of a chondrocyte graft is a promising alternative to conventional methods. Clinical practice requires this MACT procedure (matrix-associated autologous chondrocyte transplantation) to produce a biocompatible replacement tissue with adequate mechanical properties. Mechanical stimulation has the capacity to improve the quality of these cell-seeded biomaterials. By altering chondrocytes' cellular activities, the biological and biomechanical properties of cartilage replacement tissue can be modulated. Different systems are used for this purpose, e.g. shear, perfusion, hydrostatic pressure or compression. The mechanisms, biological effects, chances and problems of the techniques are presented and assessed. Among the stimulating techniques considered are systems that apply indirect and direct shear forces such as spinner flasks, rotating-wall bioreactors, direct tissue shear and perfusion culture systems. The application of hydrostatic pressure or compression may be brought about by either static or dynamic loading systems. Compressive loading is considered in the light of both its short- and long-term effects; additionally two exemplified systems are discussed in detail. However, despite promising approaches and seemingly favourable tissue characteristics, the in vitro culturing of functional cartilage replacement tissue with cartilage-like mechanical and biological characteristics still remains elusive. Furthermore, controlling, monitoring and regulating culturing conditions are general biotechnological requirements of a standardised in vitro cultivation. Among these, different aspects such as aseptic operation, media supplementation, nutrient and gas exchange, temperature and humidity control are considered.

[Soft-tissue management in primary knee arthroplasty: common techniques, navigation and force-sensing devices]. / Weichteilmanagement in der primären Kniegelenkendoprothetik: konventionelle Techniken, Navigation und sensorintegrierte Messsysteme.

Soft-tissue management is essential for the outcome in total knee arthroplasty. In combination with osseous resections and component positioning, correction of the underlying ligamentous dysbalance should yield a stable joint throughout the flexion arc. Different "philosophies" with regard to technique, timing and tactics in ligament balancing are described. So far, surgeons have not been provided with standardised devices that allow the objective measurement of this complex issue. Moreover, knowledge concerning the "ideal" soft-tissue stability following knee arthroplasty is still sparse. As part of the scientific project "OrthoMIT" (minimal invasive orthopaedic therapy) an approach to combine conventional soft-tissue management with navigation and force-sensing devices should be realized technically. The aim is to develop an instrument for the objective measurement of soft-tissue management in scientific and clinical applications.