Article

The influence of the mechanical environment on remodelling of the patellar tendon.

St Mary's Hospital, Praed Street, Paddington, London W2 1NY, UK.
The Bone & Joint Journal (Impact Factor: 2.8). 05/2009; 91(4):557-64. DOI: 10.1302/0301-620X.91B4.21580
Source: PubMed

ABSTRACT An understanding of the remodelling of tendon is crucial for the development of scientific methods of treatment and rehabilitation. This study tested the hypothesis that tendon adapts structurally in response to changes in functional loading. A novel model allowed manipulation of the mechanical environment of the patellar tendon in the presence of normal joint movement via the application of an adjustable external fixator mechanism between the patella and the tibia in sheep, while avoiding exposure of the patellar tendon itself. Stress shielding caused a significant reduction in the structural and material properties of stiffness (79%), ultimate load (69%), energy absorbed (61%), elastic modulus (76%) and ultimate stress (72%) of the tendon compared with controls. Compared with the material properties the structural properties exhibited better recovery after re-stressing with stiffness 97%, ultimate load 92%, energy absorbed 96%, elastic modulus 79% and ultimate stress 80%. The cross-sectional area of the re-stressed tendons was significantly greater than that of stress-shielded tendons. The remodelling phenomena exhibited in this study are consistent with a putative feedback mechanism under strain control. This study provides a basis from which to explore the interactions of tendon remodelling and mechanical environment.

0 Bookmarks
 · 
80 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: It is unknown whether loss in musculo-tendinous tissue during inactivity can be counteracted by growth hormone(GH), and whether GH accelerate rehabilitation in aging individuals. Elderly men (65-75 years; n=12) had one leg immobilized two weeks followed by six weeks re-training, and were randomly assigned to daily injections of recombinant GH(rhGH, n=6) or placebo(Plc, n=6). Cross sectional area(CSA), muscle strength(MVC) and biomechanical properties of m. quadriceps and patellar tendon were determined. Muscle and tendon biopsies were analyzed for gene expressions (mRNA) of collagen(COL1A1/3A1) and insulin-like growth factors(IGF-1Ea/Ec). Fibril morphology was analyzed by transmission electron microscope(TEM). In tendon, CSA and biomechanical properties did not change following immobilization, but an increase in CSA was found after 6 weeks of rehabilitation in both groups. The changes were more pronounced when GH was injected. Furthermore, tendon stiffness increased in GH group. Muscle CSA declined after immobilization in Plc but not in GH group. Muscle CSA increased during re-training with a significant larger increase in GH group compared to Plc. Both a time and group effect was seen for IGF-1Ea/Ec and COL1A1/3A1 mRNA expression in muscle with a difference between GH and Plc. IGF-1Ea/Ec and COL-1A1/3A1 mRNA expression increased in muscle following immobilization and re-training in subjects receiving GH, whereas an increase in IGF-1Ec mRNA expression was seen in the Plc group only after re-training. In conclusion, in elderly humans GH seems to have a matrix stabilizing effect during inactivity and rehabilitation by stimulating collagen expression in the musculo-tendinous tissue and increasing tendon CSA and stiffness.
    Journal of Applied Physiology 11/2013; 116(2). DOI:10.1152/japplphysiol.01077.2013 · 3.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tendon injuries vary from acute rupture to chronic tendinopathy. For an optimal treatment of either condition, a profound knowledge is essential. Therefore, this article shall give an overview of physiology, biology, and pathology of tendon healing and state of the art in tendon bioengineering. For a preferably comprehensive survey, the current literature listed in PubMed and published in English peer-reviewed journals (March 2013) was systematically reviewed for tendon healing and tendon bioengineering including cytokine modulation, autologous sources of growth factors, biomaterials, gene therapy, and cell-based therapy. No differentiation was made between clinical and preclinical in vitro investigations. Tendon healing happens in certain stadiums of inflammation, formation, and remodelling. An additional process of "collagen recycling" close to the healing site has been described recently. With increasing comprehension of physiology and pathology of tendon healing, several promising approaches in tendon bioengineering using growth factors, biomaterials, gene therapy, or cell-based therapy are described. However, only some of these are already used routinely in clinics. Strong and resistant tendons are crucial for a healthy musculoskeletal system. The new approaches in tendon bioengineering are promising to aid physiological tendon healing and thus resulting in a stronger and more resistant tendon after injury. The growing knowledge in this field will need to be further taken into clinical studies so that especially those patients with prolonged courses, revision surgery, or chronic tendinopathy and high-demanding patients, i.e., professional athletes would benefit. LEVEL OF EVIDENCE: II.
    Knee Surgery Sports Traumatology Arthroscopy 09/2013; DOI:10.1007/s00167-013-2680-z · 2.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This review suggests why some discs degenerate rather than age normally. Intervertebral discs are avascular pads of fibrocartilage that allow movement between vertebral bodies. Human discs have a low cell density and a limited ability to adapt to mechanical demands. With increasing age, the matrix becomes yellowed, fibrous, and brittle, but if disc structure remains intact, there is little impairment in function, and minimal ingrowth of blood vessels or nerves. Approximately half of old lumbar discs degenerate in the sense of becoming physically disrupted. The posterior annulus and lower lumbar discs are most affected, presumably because they are most heavily loaded. Age and genetic inheritance can weaken discs to such an extent that they are physically disrupted during everyday activities. Damage to the endplate or annulus typically decompresses the nucleus, concentrates stress within the annulus, and allows ingrowth of nerves and blood vessels. Matrix disruption progresses by mechanical and biological means. The site of initial damage leads to two disc degeneration “phenotypes”: endplate-driven degeneration is common in the upper lumbar and thoracic spine, and annulus-driven degeneration is common at L4-S1. Discogenic back pain can be initiated by tissue disruption, and amplified by inflammation and infection. Healing is possible in the outer annulus only, where cell density is highest. We conclude that some discs degenerate because they are disrupted by excessive mechanical loading. This can occur without trauma if tissues are weakened by age and genetic inheritance. Moderate mechanical loading, in contrast, strengthens all spinal tissues, including discs. Clin. Anat., 2014. © 2014 Wiley Periodicals, Inc.
    Clinical Anatomy 04/2014; DOI:10.1002/ca.22404 · 1.16 Impact Factor