1 Principles of Thumb and Finger Reconstruction: Concept of Ray and Cascade

David T. W. Chiu, J. William Littler, and Joseph Upton

1.1 Key Points

• Refined knowledge of hand anatomy is a prerequisite for a successful reconstruction.

• Rebuilding a thumb or a finger involves both restoration of missing structures and a dynamic and harmonious cascade.

• In motion, the thumb and fingers move rhythmically in sequence simulating the well-known Fibonacci series.

• Emphasis is placed upon the details of skeletal, vascular, musculotendinous, and cutaneous systems as they pertain to a successful reconstruction of a thumb or a finger.

• Functional levels of loss are more accurate and pertinent than those based solely on radiologic appearance.

• Functional cutaneous units of the thumb, fingers, and hand are important parameters affecting treatment.

• The impact of microsurgical transfers has dramatically broadened the options for reconstruction at every level.

1.2 Introduction

Reconstruction of a thumb or finger is an artistic process. It involves accurate assessment of the anatomical deficit, discerning appreciation of the functional loss, insightful conceptualization of a simile of the normalcy, and of getting there. Execution of a well-conceived formulation also requires flawless skill, precise instrumentation, seamless logistics, figuring a way to get there, and harmonious teamwork. Rehabilitation could make or break the most well-conceived and executed repair efforts; timely therapy is crucial. Objective evaluation of results is the springboard to progress and demands utmost intellectual honesty. Such an effort may be likened to a journey, which is much more efficient when there is a compass to indicate the direction and a torch to brighten the path. Collectively, we call these “principles” (Gilles, 1957; Littler, 1964c:1612, 1977e:3103; Chase, 1983). Our teachers bestowed upon us many of these salient principles. Others we learn through critical deductions. This publication presents a careful analysis of these principles through the collective experience of five hand surgeons with a combined 225 years of clinical practice of hand surgery over a 75-year period. This is what we would like to share with our colleagues when they consider reconstructive surgery of the hand.

1.3 Concept of Ray and Cascade

In reconstructing a digit, one aims to rebuild not only a part that bears an anatomical similarity to a thumb or finger but also a subunit that complements the remainder of the hand, to restore a dynamic and harmonious cascade. In repose, the human hand characteristically projects in an orderly manner with the central digit being the longest, the thumb the shortest on one side, and the “pinky” the second shortest on the opposing side. In motion, the intercalated series of small joints in the hand move rhythmically in sequence. When a digit flexes or extends, this motion initiates at the metacarpophalangeal joint (MPJ) and propagates in a proximal-to-distal sequence to the proximal interphalangeal joint (PIPJ) and distal interphalangeal joint (DIPJ). Such orderliness in repose and rhythmicity in motion invite comparisons to the punctuated descent of falling waters in a cascade. Reconstruction of a ray is successful only when it restores the countenance of a cascade of the hand in both form and function ( ▶ Fig. 1.1).

Da Vinci’s interpretation of the Vitruvian man was an attempt to probe the questions of how the proportions of man fit into the orderliness of the universe: of squaring the circle, finding the relationships of geometric shapes, determining specific measurements of individual human proportions, and defining both science and art into “the golden ratio” or “divine proportion.” Littler’s version of the Vitruvian hand defines similar relationships within the human hand, which are like the well-known mathematical series so prevalent in Nature: the Fibonacci sequence. The hand is an embodiment of nature (Littler, 1974a; ▶ Fig. 1.2 and ▶ Fig. 1.3).

1.4 The Essence of Hand Anatomy

The beauty in form and grace in motion of the human hand results from the dynamic display of an ensemble of uniquely structured bones, muscles, tendons, nerves, vessels, and integument. The relationship between form and function is succinctly summarized by John Hunter who noted “…structure is the ultimate expression of function” and Littler who observed that “...function imparts beauty to form” (Littler, 1974a).

It all begins in the embryonic stage as a limb bud, recognizable at 3 weeks post fertilization as a swelling derived from proliferating mesodermal cells covered by ectodermal cells lateral to the 8th to 12th myotomes. The limb bud grows rapidly in a proximal-to-distal sequence and differentiates into a complete form by 8 weeks, which marks the end of embryogenesis. The central core of...