Abstract
When dealing with the function of the human hand, an automatic link to relevant previous books on this subject is generated. Obviously, one commences with The Hand Its Mechanism and Vital Endowments as Evincing Design by Sir Charles Bell. The 1833 edition was made available to the vast majority of us when Graham Stack reproduced a facsimile on behalf of the British Society for Surgery of the Hand, and we are all indebted to him for that initiative. Over the years, a number of books dealing with this subject have been added: Functional and Surgical Anatomy of the Hand by Emanuel Kaplan, Structural and Dynamic Bases of Hand Surgery by Eduardo Zancolli and Physiologie Articulaire by IA Kapandji, who, in the last edition, reached near perfection in the field of hand biomechanics. I believe that a thorough knowledge of these texts is mandatory before embarking on reading this fascinating book by Lynette A. Jones and Susan J Lederman. A. Lee Dellon, in his book Evaluation of Sensibility and Re-education of Sensation in the Hand, had already attempted to bridge the gap between experts in the domains of neuroscience and peripheral nerves. The present book ties in previous experience to future projects, such as man–machine interfaces, neural control of movements, vestibular ocular reflex (VOR) and the robotic hand.
This book is constructed in eleven sections: the historical overview is well designed and includes numerous references and lingers on peculiar aspects, e.g. the work by Weber who made extensive measurements of tactile acuity using his own body and that of his brother. The relevance of sensation was already very well detailed by Giulio Casseri (1552–1616), who stressed the importance that skin has for life. Extensive dissections made on the palmar aspect of the hand and plantar surface of the foot brought him to the conclusion, reported in his book, entitled Pentaesthesion, that tactile sensation is the most relevant among all the sense organs. In Chapter 3, the types of mechanoreceptors are described. The S (slowly) adapting I units, including the Merkel cell, densely distributed (1 × 2 mm2) to render them particularly sensitive to local stress–straining fields. F (fast adapting) I units, corresponding to the Meissner’s corpuscles and providing critical feedback for precise grip control. Ruffini endings and Pacini corpuscles are also well defined in their function. Basically, the underlying concept of stationary versus moving stimuli perception is laid down, so that the reader is prepared to digest a probably novel concept related to an active “haptic sense”. Haptic has a Greek root and refers to active exploration and manipulation of different tools with our hand. Textures and object weights are singled out by the active haptic sense, and mechanoreceptors in the muscle, tendons and joint of the hand and upper limb provide adjunct information. In this regard, it is relevant to quote, once again, Charles Bell—“In the use of the hand there is a double sense exercised; we must not only feel the contact of the object but we must be sensible to the muscular effort which is made to reach and grasp it.” Prehension (Chapter 6) is integrated by visuomotor and digital channels. Analysis and the theories of reach are fully explained: without continuous visual impact, the reaching movement takes longer, and, when the afferent information from cutaneous mechanoreceptors are abolished, acutely, by administration of anasthetic procedures and, chronically, by denervation, the control of prehensive force is lost. Chapter 7 on non-prehensile skilled movements is also exciting. Monastic sign language and the homologous code developed by aboriginal tribes represent concerted efforts to exploit this communication tool independently in different continents. In this section, accurate analysis of piano playing and typing is considered, with analysis of the force produced by skilled typing (mean Key-stroke, × 0.9 N), the genesis of omission errors, etc. Consistently, the bimanual music skills of the fingering of the digit in the violin or cello player have a corresponding increase in cortical representation. Chapter 9 is full of information on hand function across the lifespan. Pacinian corpuscles, for example, change in morphology with age. Cortical myelination first occurs in the somatosensory cortex and then in the motor cortex, explaining why some adaptive reflex responses, such as increase in grip force when an object begins to slip, are possible in adults but not in young children. Information of this kind helps us understand why administration of psychometric studies of prehension in infants and children, such as the Bailey scales of infant development, might be useful in the assessment of the neurologically impaired upper limb. In Chapter 10, the applied aspects of hand function are illustrated and it becomes apparent why a project of exploring art by touch, as provided in the virtual museum by Perco in Pisa, where “The Pure Form” can be perceived by haptically interacting with a simulated digitised three-dimensional sculpture. This concept represents the background for the new methods of hand rehabilitation.
I believe that this book will consolidate new assessment methods strictly related to cortex maturity and neural imaging techniques, which might be useful for those who deal with central affections, such as spasticity and the devastating consequences of brachial plexus and spinal cord injuries occurring in the perinatal and adult period of life. Its usefulness also extends into the less complicated field of routine hand and peripheral nerve injury surgery.
This book takes some time to read but represents an inspiring source of comprehension of function, treatment and outcome study design in the domain of the hand.