Jean Claude Guimberteau

Introduction

Traditional basic concepts, terms, and information to describe natural organ intermobility seem to be at variance with anatomical reality. The traditional notion of different fascias or the sliding, gliding, collagenous system historically referred to as paratenon, connective or areolar tissues focuses on the separateness of these structures. Electron scanning microscopy suggests that this system does not consist of different, superimposed layers. In reality, there is a single, tissular architecture with different specializations. To emphasize its functional implications, we call this tissue the multimicrovacuolar collagenous (dynamic) absorbing system (MVCAS) (Plate 3.6.1).

Mechanical observations

In finger flexion, the movement of the flexor tendon is barely discernible in the palm. It is the same under the skin areolar tissue, which is the connective link between muscle, tendon, fat, aponeurosis and subdermal areas. The MVCAS system situated between the tendon and its neighboring tissue seems to favor optimal sliding. Tendon excursion can be large and rapid without resistance and without provoking any movement in neighboring tissue, thus accounting for the absence of any dynamic repercussions of such movement on the skin surface.

Microanatomical observations in vivo

Our observations are a result of over 20 years performing and improving complex flexor tendon transfers. We video-recorded the MVCAS during 95 in-vivo human surgical dissections using light microscopy (magnification × 25) either directly under the skin or close to tendons, muscles or nerve sheaths. Further, an in-vitro study was carried out on human and animal samples, such as the flexor carpi radialis in cattle in which the organization is very similar to that of the human flexor profundus. The live results show what cadaver results can not: The MVCAS can be seen as a continuous structure composed of billions of dynamic, microvacuolar, multidirectional filaments, intertwining and creating partitions that enclose vacuolar shapes, organized in dispersed, fractal, pseudo-geometrics (Plate 3.6.1C). We want to express that the living matter is built of microvacuolar architectures (Plate 3.6.2).

Microvacuolar observations

Microvacuoles have diameters ranging from a few to several dozen micrometers and they vary in length from a few microns to a few millimeters, thus giving an overall disorganized, chaotic appearance (Plate 3.6.2A). The vacuoles are organized on several levels in different directions (Plate 3.6.2B): The pattern is pseudogeometric, polygonal, and tends to be icosahedric (Plate 3.6.2D). The levels are hierarchically arranged, fractally shaped and may span several partial subunits. The entire framework contains a highly hydrated (70%) proteoglycan gel. The lipid content (4%) is high. The sides of the intertwined vacuoles are composed of collagen 75% and elastine 25%.

An appearance of dynamic roles

The MVCAS we studied appears to be organized differently depending on the function of the structure. The collagen framework and the intravacuolar spaces give form and stability. The gel permits easy change of shape during movement while volume remains constant. The greater the distance that the structure must travel, the smaller and denser are the vacuoles. The microvacuolar structure has a consistency of conformation, capable of taking on many shapes, adaptable to the physical constraints that it undergoes, and has a form of memory allowing it to return to its initial position. A major role of this framework is to make sure that the structures can move freely without anything else moving around them. The overall configuration is highly efficient, combining great mechanical strength and lightness with thermodynamic energy conservation, diminishing friction with easy deformability (see Plate 3.6.5).

The tendon is not nourished by synovial fluid, but by its own vascular system, like every organ. A tendon has optimal functional value only when it is surrounded by its original sliding sheath and its vascular heritage. Our observation of this nutritional role has altered our surgical procedures. The MVCAS system is important for the nutrition of the structures embedded in it and acts as a frame for blood and lymph vessels. The histological continuity between the paratenon, the common carpal sheath and the flexor tendons illustrates the vascularization of this functional ensemble and introduces a new concept: The sliding unit, composed of the tendon and its surrounding sheaths.