Quantifying proximal patellar tendon changes during adolescence in elite ballet dancers, a 2-year study

Patellar tendon pathology appears to develop in young athletes. It is not known how this tendon develops through adolescence. This longitudinal study investigated proximal patellar tendon development during the adolescent growth spurt in young ballet dancers and identified whether puberty (estimated by maturity offset) had an effect on tendon development. Fifty two dancers (32 female and 20 male dancers, ages 11-18 at baseline) had ultrasound images of their tendons every 6 months for 2 years. Changes in tendon size (anterior-posterior diameter) on grayscale images and echogenicity, as quantified using ultrasound tissue characterization, were recorded each time. Maturity offset was calculated used to estimate peak height velocity (adolescent growth spurt). Maturity offset did not affect effect tendon composition before peak height velocity; however, after participants passed peak height velocity, maturity offset increased the composition of stable echopattern (P < .05): a 4% differential increase in type I echopattern, indicative of normal tendon structure, and a decrease in type III echopattern (more disorganized echopattern) by 0.7% per year. Anterior-posterior thickness increased by 0.2 mm/y (P < .05) measured 2 cm below the patella. Following peak height velocity, the proximal patellar tendon attachment increased in thickness and demonstrated a more stable echopattern representative of aligned fibrillar structure. Future research is required to further understand this normal maturation and the factors that support this process, with the aim of reducing the development of patellar tendon pathology in the adolescent jumping athlete.

Ultrasound elastography and ultrasound tissue characterisation for tendon evaluation

Ultrasound elastography (UE) and ultrasound tissue characterisation (UTC) are two newer modes of ultrasound (US) which have begun to attract scientific interests as ways to improve tendon characterisation. These modes of US show early promise in improved diagnostic accuracy, prediction of at-risk tendons and prognostication capability beyond conventional grey-scale US. Here, we provide a review of the literature on UE and UTC for Achilles, patellar and rotator cuff tendons.

The translational potential of this article: The present literature indicates that UE and UTC could potentially increase the clinician's ability to accurately diagnose the extent of tendon pathology, including preclinical injury.

Achilles Pain, Stiffness, and Muscle Power Deficits: Midportion Achilles Tendinopathy Revision 2018

The Orthopaedic Section of the American Physical Therapy Association (APTA) has an ongoing effort to create evidence-based practice guidelines for orthopaedic physical therapy management of patients with musculoskeletal impairments described in the World Health Organization's International Classification of Functioning, Disability, and Health (ICF). The purpose of these revised clinical practice guidelines is to review recent peer-reviewed literature and make recommendations related to midportion Achilles tendinopathy. J Orthop Sports Phys Ther 2018;48(5):A1-A38. doi:10.2519/jospt.2018.0302.

The Role of the Vascular and Structural Response to Activity in the Development of Achilles Tendinopathy: A Prospective Study

BACKGROUND

Several risk factors have been suggested in the development of Achilles tendinopathy, but large-scale prospective studies are limited.

PURPOSE

To investigate the role of the vascular response to activity of the Achilles tendon, tendon thickness, ultrasound tissue characterization (UTC) of tendon structure, and foot posture as possible risk factors in the development of Achilles tendinopathy.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

The study began with 351 first-year students at Ghent University. After 51 students were excluded, 300 were tested in the academic years 2013-2014 and 2014-2015 and were followed prospectively for 2 consecutive years by use of a multilevel registration method. Of those, 250 students were included in the statistical analysis. At baseline, foot posture index and UTC were investigated bilaterally. Blood flow and tendon thickness were measured before and after a running activity. Cox regression analyses were performed to identify significant contributors to the development of Achilles tendinopathy.

RESULTS

During the 2-year follow-up, 27 of the included 250 participants developed Achilles tendinopathy (11%). Significant predictive effects were found for female sex and blood flow response after running ( P = .022 and P = .019, respectively). The risk of developing Achilles tendinopathy increased if the blood flow increase after running was reduced, regardless of sex, foot pronation, and timing of flow measurements. The model had a predictive accuracy of 81.5% regarding the development of Achilles tendinopathy, with a specificity of 85.0% and a sensitivity of 50.0%.

CONCLUSION

This prospective study identified both female sex and the diminished blood flow response after running as significant risk factors for the development of Achilles tendinopathy. UTC of tendon structure, Achilles tendon thickness, and foot posture did not significantly contribute to the prediction of Achilles tendinopathy. A general evaluation of tendon structure by UTC, measurement of tendon thickness, or determination of the foot posture index will not allow clinicians to identify patients at risk for developing Achilles tendinopathy. Furthermore, it may be possible to improve blood flow after activity by using noninvasive techniques (such as prostaglandins, compression stockings, heat, massage, and vibration techniques). These techniques may be useful in the prevention and management of Achilles tendinopathy, but further research is needed.

Tendon injury and repair - A perspective on the basic mechanisms of tendon disease and future clinical therapy

Tendon is an intricately organized connective tissue that efficiently transfers muscle force to the bony skeleton. Its structure, function, and physiology reflect the extreme, repetitive mechanical stresses that tendon tissues bear. These mechanical demands also lie beneath high clinical rates of tendon disorders, and present daunting challenges for clinical treatment of these ailments. This article aims to provide perspective on the most urgent frontiers of tendon research and therapeutic development. We start by broadly introducing essential elements of current understanding about tendon structure, function, physiology, damage, and repair. We then introduce and describe a novel paradigm explaining tendon disease progression from initial accumulation of damage in the tendon core to eventual vascular recruitment from the surrounding synovial tissues. We conclude with a perspective on the important role that biomaterials will play in translating research discoveries to the patient.

STATEMENT OF SIGNIFICANCE

Tendon and ligament problems represent the most frequent musculoskeletal complaints for which patients seek medical attention. Current therapeutic options for addressing tendon disorders are often ineffective, and the need for improved understanding of tendon physiology is urgent. This perspective article summarizes essential elements of our current knowledge on tendon structure, function, physiology, damage, and repair. It also describes a novel framework to understand tendon physiology and pathophysiology that may be useful in pushing the field forward.

Tissue alignment enhances remodeling potential of tendon-derived cells - Lessons from a novel microtissue model of tendon scarring

Tendinopathy is a widespread and unresolved clinical challenge, in which associated pain and hampered mobility present a major cause for work-related disability. Tendinopathy associates with a change from a healthy tissue with aligned extracellular matrix (ECM) and highly polarized cells that are connected head-to-tail, towards a diseased tissue with a disorganized ECM and randomly distributed cells, scar-like features that are commonly attributed to poor innate regenerative capacity of the tissue. A fundamental clinical dilemma with this scarring process is whether treatment strategies should focus on healing the affected (disorganized) tissue or strengthen the remaining healthy (anisotropic) tissue. The question was thus asked whether the intrinsic remodeling capacity of tendon-derived cells depends on the organization of the 3D extracellular matrix (isotropic vs anisotropic). Progress in this field is hampered by the lack of suitable in vitro tissue platforms. We aimed at filling this critical gap by creating and exploiting a next generation tissue platform that mimics aspects of the tendon scarring process; cellular response to a gradient in tissue organization from isotropic (scarred/non-aligned) to highly anisotropic (unscarred/aligned) was studied, as was a transient change from isotropic towards highly anisotropic. Strikingly, cells residing in an 'unscarred' anisotropic tissue indicated superior remodeling capacity (increased gene expression levels of collagen, matrix metalloproteinases MMPs, tissue inhibitors of MMPs), when compared to their 'scarred' isotropic counterparts. A numerical model then supported the hypothesis that cellular remodeling capacity may correlate to cellular alignment strength. This in turn may have improved cellular communication, and could thus relate to the more pronounced connexin43 gap junctions observed in anisotropic tissues. In conclusion, increased tissue anisotropy was observed to enhance the cellular potential for functional remodeling of the matrix. This may explain the poor regenerative capacity of tenocytes in chronic tendinopathy, where the pathological process has resulted in ECM disorganization. Additionally, it lends support to treatment strategies that focus on strengthening the remaining healthy tissue, rather than regenerating scarred tissue.

Quantification of Internal Stress-Strain Fields in Human Tendon: Unraveling the Mechanisms that Underlie Regional Tendon Adaptations and Mal-Adaptations to Mechanical Loading and the Effectiveness of Therapeutic Eccentric Exercise

By virtue of their anatomical location between muscles and bones, tendons make it possible to transform contractile force to joint rotation and locomotion. However, tendons do not behave as rigid links, but exhibit viscoelastic tensile properties, thereby affecting the length and contractile force in the in-series muscle, but also storing and releasing elastic stain energy as some tendons are stretched and recoiled in a cyclic manner during locomotion. In the late 90s, advancements were made in the application of ultrasound scanning that allowed quantifying the tensile deformability and mechanical properties of human tendons in vivo. Since then, the main principles of the ultrasound-based method have been applied by numerous research groups throughout the world and showed that tendons increase their tensile stiffness in response to exercise training and chronic mechanical loading, in general, by increasing their size and improving their intrinsic material. It is often assumed that these changes occur homogenously, in the entire body of the tendon, but recent findings indicate that the adaptations may in fact take place in some but not all tendon regions. The present review focuses on these regional adaptability features and highlights two paradigms where they are particularly evident: (a) Chronic mechanical loading in healthy tendons, and (b) tendinopathy. In the former loading paradigm, local tendon adaptations indicate that certain regions may “see,” and therefore adapt to, increased levels of stress. In the latter paradigm, local pathological features indicate that certain tendon regions may be “stress-shielded” and degenerate over time. Eccentric exercise protocols have successfully been used in the management of tendinopathy, without much sound understanding of the mechanisms underpinning their effectiveness. For insertional tendinopathy, in particular, it is possible that the effectiveness of a loading/rehabilitation protocol depends on the topography of the stress created by the exercise and is not only reliant upon the type of muscle contraction performed. To better understand the micromechanical behavior and regional adaptability/mal-adaptability of tendon tissue it is important to estimate its internal stress-strain fields. Recent relevant advancements in numerical techniques related to tendon loading are discussed.

The tendinopathic Achilles tendon does not remain iso-volumetric upon repeated loading: insights from 3D ultrasound

Mid-portion Achilles tendinopathy (MAT) alters the normal three-dimensional (3D) morphology of the Achilles tendon (AT) at rest and under a single tensile load. However, how MAT changes the 3D morphology of AT during repeated loading remains unclear. This study compared the AT longitudinal, transverse and volume strains during repeated loading in MAT with those of the contralateral tendon in people with unilateral MAT. Ten adults with unilateral MAT performed 10 successive 25 second submaximal (50%) voluntary isometric plantarflexion contractions with both legs. Freehand 3D ultrasound scans were recorded and used to measure whole AT, free AT, and proximal AT longitudinal strains and free AT cross-sectional area (CSA) and volume strains. The free AT experienced higher longitudinal and CSA strain and reached steady state following a greater number of contractions (5 contractions) in MAT compared to the contralateral tendon (3 contractions). Further, free tendon CSA and volume strained more in MAT than contralateral tendon from the first contraction, whereas free AT longitudinal strain was not greater than the contralateral tendon until the fourth contraction. Volume loss from the tendon core therefore preceded the greater longitudinal strain in MAT. Overall, these findings suggest that the tendinopathic free AT experiences an exaggerated longitudinal and transverse strain response under repeated loading that is underpinned by an altered interaction between solid and fluid tendon matrix components. These alterations are indicative of accentuated poroelasticity and an altered local stress-strain environment within the tendinopathic free tendon matrix, which could affect tendon remodelling via mechanobiological pathways.

Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research?

The pathogenesis of tendinopathy and the primary biological change in the tendon that precipitates pathology have generated several pathoaetiological models in the literature. The continuum model of tendon pathology, proposed in 2009, synthesised clinical and laboratory-based research to guide treatment choices for the clinical presentations of tendinopathy. While the continuum has been cited extensively in the literature, its clinical utility has yet to be fully elucidated. The continuum model proposed a model for staging tendinopathy based on the changes and distribution of disorganisation within the tendon. However, classifying tendinopathy based on structure in what is primarily a pain condition has been challenged. The interplay between structure, pain and function is not yet fully understood, which has partly contributed to the complex clinical picture of tendinopathy. Here we revisit and assess the merit of the continuum model in the context of new evidence. We (1) summarise new evidence in tendinopathy research in the context of the continuum, (2) discuss tendon pain and the relevance of a model based on structure and (3) describe relevant clinical elements (pain, function and structure) to begin to build a better understanding of the condition. Our goal is that the continuum model may help guide targeted treatments and improved patient outcomes.

Plantaris Excision and Ventral Paratendinous Scraping for Achilles Tendinopathy in an Athletic Population

BACKGROUND

Achilles tendinopathy is a frequent problem in high-level athletes. Recent research has proposed a combined etiologic role for the plantaris tendon and neovascularization. Both pathologies can be observed on ultrasound imaging.(1,13) However, little is known about the change in structure of the Achilles tendon following the surgical treatment of these issues. The purpose of the study was to assess if excising the plantaris and performing ventral paratendinous "scraping" of the neovascularization improved symptoms of Achilles tendinopathy and whether there was a change in the fibrillar structure of the tendon with ultrasound tissue characterization (UTC) following this operation.

METHODS

This prospective consecutive case series included 15 professional/semiprofessional athletes (17 Achilles tendons) who underwent plantaris excision and paratendinous scraping to treat noninsertional Achilles tendinopathy. The plantaris tendon was excised if adherent to the Achilles tendon, and the area of neovascularization for scraping was demarcated on preoperative imaging. Preoperative and postoperative Victorian Institute of Sports Assessment-Achilles (VISA-A) scores were taken. UTC was performed on 11 of 17 tendons preoperatively and postoperatively. The mean follow-up was for 25 months.

RESULTS

Fourteen of 15 patients had a successful outcome after the surgery. The mean VISA-A improved from 51 to 95 (p=.0001). There was a statistically significant (p=.04) improvement in the aligned fibrillar structure of the tendon confirmed with UTC scanning following surgery from 90% (±8) to 96% (±5).

CONCLUSION

This group of high-level athletes derived an excellent clinical result from this operation. Furthermore, UTC scanning offered an objective method to evaluate the healing of Achilles tendons.

LEVEL OF EVIDENCE

Level IV, case series.

Tendon neuroplastic training: changing the way we think about tendon rehabilitation: a narrative review

Tendinopathy can be resistant to treatment and often recurs, implying that current treatment approaches are suboptimal. Rehabilitation programmes that have been successful in terms of pain reduction and return to sport outcomes usually include strength training. Muscle activation can induce analgesia, improving self-efficacy associated with reducing one's own pain. Furthermore, strength training is beneficial for tendon matrix structure, muscle properties and limb biomechanics. However, current tendon rehabilitation may not adequately address the corticospinal control of the muscle, which may result in altered control of muscle recruitment and the consequent tendon load, and this may contribute to recalcitrance or symptom recurrence. Outcomes of interest include the effect of strength training on tendon pain, corticospinal excitability and short interval cortical inhibition. The aims of this concept paper are to: (1) review what is known about changes to the primary motor cortex and motor control in tendinopathy, (2) identify the parameters shown to induce neuroplasticity in strength training and (3) align these principles with tendon rehabilitation loading protocols to introduce a combination approach termed as tendon neuroplastic training. Strength training is a powerful modulator of the central nervous system. In particular, corticospinal inputs are essential for motor unit recruitment and activation; however, specific strength training parameters are important for neuroplasticity. Strength training that is externally paced and akin to a skilled movement task has been shown to not only reduce tendon pain, but modulate excitatory and inhibitory control of the muscle and therefore, potentially tendon load. An improved understanding of the methods that maximise the opportunity for neuroplasticity may be an important progression in how we prescribe exercise-based rehabilitation in tendinopathy for pain modulation and potentially restoration of the corticospinal control of the muscle-tendon complex.