Because the majority of children with hypoplasia of a portion of the upper extremity are very high functioning, they require no surgical care. Nonetheless, there are two instances where surgical treatments are helpful. The first indication is to remove a “floppy” digit that is interfering with the functional abilities of the hand. In such cases, excising the affected digit and reconstructing the local web space are recommended as surgical care. A short course of occupational therapy following the procedure may be helpful as well. The second circumstance, which is discussed in another chapter, involves reconstructing and improving the function of a hypoplastic thumb.

After considering hypoplasia of the upper extremity in general, a discussion of the more common clinical types is appropriate. Flatt reported that out of 2,758 collected cases of congenitally anomalous hands, brachydactyly (5.2 %) and thumb hypoplasia (3.5 %) were the most frequently seen undergrowth conditions (Flatt 1994a). Because thumb hypoplasia is discussed as a separate topic elsewhere, this section will focus on brachydactyly and symbrachydactyly.

The term brachydactyly as translated from Greek means “short finger.” While the whole digit may appear to be small, on radiographic examination, an individual bone segment is often smaller than normal. When the phalanges are involved, the middle phalanx is the most commonly affected bone. In this instance, the condition may be referred to as brachymesophalangia (short middle phalanx). Short metacarpals can be seen in association with some syndromes (e.g., Turner’s), so the term brachymetacarpia may be encountered in the literature (Fig. 1). It should be stated that these terms are purely descriptive and do not imply that one type consistently has a more favorable prognosis than others.

Most forms of brachydactyly are inherited in an autosomal dominant manner, usually with variable severity. However, there are some cases of brachydactyly are felt to be sporadic in occurrence because of no well-documented family inheritance pattern. On the molecular level, alterations in BMP cartilage-derived morphogenic protein have been shown to be associated with brachydactyly in humans and mouse models (Waters and Bae 2012a; Fig. 2). A classification system for brachydactyly, first proposed by Bell in 1951 (Fitch 1979), focuses on the anatomic location of the hypoplastic segment to categorize the anomaly (Table 3). This system has been most useful in the identification of certain inheritance patterns by being able to follow specific types along family pedigrees. For example, the most common types, A3 and D, have been shown to demonstrate autosomal dominant inheritance with reduced penetrance. Some populations also have a relatively high frequency of certain types of brachydactyly (Temtamy and Aglan 2008). As far as the clinical presentation is concerned, the degree to which any digit is involved may range from a “small, but normal” appearing finger to a tiny residual “nubbin ,” which may be nothing more than a small pouch of skin attached to the hand.

When evaluating a patient with small digits, the term symbrachydactyly may be encountered in the congenital hand anomalies literature. As defined, symbrachydactyly is the condition representing hypoplastic digits (brachydactyly), webbing between fingers (syndactyly), and a general hypoplasia of the hand. To avoid confusion, brachydactyly refers specifically to the digit, whereas symbrachydactyly describes a spectrum of clinical findings seen in the hand.

A descriptive classification system has identified four separate types of symbrachydactyly: peromelic, oligodactylic, short finger, and monodactylic (Nguyen and Jones 2009) based upon the most commonly seen anatomic features (Figs. 3 and 4). Symbrachydactyly is often seen unilaterally, and the occurrence is felt to be sporadic in nature. It is secondary to a failure of formation, but the exact manner by which this occurs continues to be investigated. Symbrachydactyly can be seen in association with other conditions, and the classic example is Poland’s syndrome (absence of the sternal head of the pectoralis major muscle with various degrees of ipsilateral hand hypoplasia; Fig. 5). This condition has recently been reported in association with transverse deficiency at the level of the forearm (Kallemeier et al. 2007). The term “atypical cleft hand” is also seen describing cases of symbrachydactyly.

Although symbrachydactyly and constriction band syndrome (CBS, discussed in another chapter) can appear similar in clinical appearance, the conditions have different diagnostic and treatment implications. There are two distinct differences. First, in patients with CBS, actual bands are usually identified elsewhere in the body. However, in symbrachydactyly, only one hand is commonly affected, and no other bands are seen. Second, with symbrachydactyly, the anatomic structures proximal to the small digits are also hypoplastic or abnormal. In CBS, the musculoskeletal structures proximal to a constriction band are normal in size (Fig. 6).

While classification schemes regarding brachydactyly and symbrachydactyly are helpful in describing the child’s clinical presentation, these systems are unable to predict the child’s ability to use the hand. Any surgical recommendations should focus on improving a child’s functional outcome as “function trumps form.” Input from the family about hand use, evaluations from therapists, and direct observation of the patient are critical in the decision-making process. Many patients with brachydactyly and symbrachydactyly are highly functional, adapt well to their hand anomaly, and do not warrant surgical intervention. They may occasionally need an assistive device to help with a specific task, however; surgery would not appreciably improve their function. There are cases that warrant surgery to augment hand use.

Probably the most common surgical technique to augment function involves altering the skin about the affected digit(s) through syndactyly release and/or web space reconstruction. Because the care of syndactylized fingers is presented in another chapter, a brief summary of web space reconstruction will be discussed here. The main goals of this procedure are to increase digital separation (span) and improve the apparent length of the fingers by providing depth to the web space. The Z-plasty and its varied modifications are the most common methods used to improve the web space (Shaw et al. 1973). Strict attention to detail is needed when designing the angles and arm’s length of flap transpositions in order to maximize skin mobilization. Also, great care must be used when handling the transposed flaps so that tension on the skin is minimized. In most cases, well-designed skin flaps do not require additional soft tissue coverage. However, if skin is needed, a full-thickness skin graft can be used to supplement the reconstruction. As mentioned in the treatment of syndactyly, skin grafts should be avoided in the web space commissure due to their propensity to contract.

The actual length of a finger can be improved in two ways. For minor changes in digit length, an osteotomy and interposition bone grafting can be used. While this technique allows for immediate gains in length, the concern is that inserting too large a graft in a small digit may compromise the surrounding skin and soft tissue structures leading to necrosis of the fingertip (Flatt 1994b). An alternative is distraction osteogenesis,which involves gradual lengthening of the bone and the soft tissues. There have been many methods described to achieve this task (Arata et al. 2011), although the basic technique requires an osteotomy and a device to gradually distract (lengthen) the osteotomy site. The most common types of distractors are uni-plane external fixators, attached to the bone by small wires. The slow distraction rate, about 0.5 mm to1mm per day, allows for both fracture callus formation and the accommodation of the soft tissues necessary for bone lengthening. Gains in digital length of up to 3.5 cm have been reported (Seitz and Froimson 1995). After the bone is lengthened to the desired amount, the distraction ceases and the external fixator is left in place until the regenerate callus matures to resemble normal bone (i.e., a cortical shell and medullary cavity). Subsequently, the device is removed and appropriate therapy is begun. Early removal can result in callus deformation or overt fracture through the regenerative bone.

Nonvascularized toe phalangeal transfer is a method used to achieve immediate length in a hypoplastic digit. The technique typically involves harvesting the proximal phalanx from a toe, then transplanting it within the skin of a hypoplastic digit. This procedure is controversial with regard to indications and outcome. The best results are when the procedure is done before 18 months of age, as the rates of physeal arrest and phalangeal resorption increase beyond this age (Nguyen and Jones 2009). Preliminary nonvascularized toe phalangeal transfer followed by distraction lengthening of the phalanx has been performed (Netscher and Lewis 2008). A recent article has shown that there is potential donor site morbidity with the nonvascularized toe phalangeal transfer, thus narrowing the indications for he procedure (Garagnani et al. 2012).