Interfascicular matrix-mediated transverse deformation and sliding of discontinuous tendon subcomponents control the viscoelasticity and failure of tendons.

In the present article, we investigated the sliding of discontinuous tendon subcomponents and the variation of nonhomogeneous deformation in the human Achilles tendon (AT) over time using uniaxial tensile and relaxation tests. The deformation and the resulting strain distribution under uniaxial tension are examined using a vision-based 3-D digital image correlation (DIC) system, which allows estimation of the strain field in the axial and lateral directions. Relaxation test under B-mode ultrasound imaging with the use of DIC method provides information about the local strain variation over time in the axial and anteroposterior directions. The observed nonhomogeneous deformation, a result from the twisted structure of the tendon, shows both compressive and tensile transverse strains that can generate interfascicular matrix (IFM) failure and initiate water accumulation in the course of tendinopathy. Moreover, using B-mode elastography with the DIC method, we have observed areas of low stiffness when the strain values exceed the strength limits, and this could correspond to IFM carrying the load between discontinuous tendon subcomponents. Thus, IFM carrying complex multiscale stresses may be responsible for the strength and viscoelastic properties of the AT. The results presented here reveal a new pathomechanism of AT failure. This could be useful in further studies on tendinopathy as well as effective planning of the AT therapy.

Pilot study of new training model for laparoscopic surgery.

The aim of this study was to evaluate whether an assessment exercise performed on a laparoscopic trainer model reliably reflects previous laparoscopic experience and can therefore be used to accurately assess laparoscopic skills in surgical trainees. Subjects were recruited from a cross-section of surgical trainees and students at the Great Ormond Street Hospital for Children and the Institute of Child Health. Subjects were required to complete a baseline laparoscopic surgical skills questionnaire and an exercise on a new laparoscopic trainer model. Nine subjects completed both the baseline questionnaire and the exercise. These subjects exhibited a wide range of previous experience in laparoscopic surgery. Subjects with higher self-assessment scores had the lowest exercise scores (i.e. better scores; P=0.003). Furthermore, the exercise score was strongly negatively correlated with the baseline number of training modalities received (P=0.007) and the laparoscopic experience score (P=0.027). The assessment exercise on a novel laparoscopic trainer was capable of differentiating between subjects with little laparoscopic experience and those with more extensive previous laparoscopic training. The correlation between the exercise score and measured baseline variables suggests that the scoring system used in this model is sensitive and specific to measuring skills relevant to laparoscopic surgery.