Pediatric Upper Extremity Disorders
Micah Sinclair, MD
Sarah E. Sibbel, MD
Dr. Sibbel or an immediate family member serves as a board member, owner, officer, or committee member of the Pediatric Orthopaedic Society of North America. Neither Dr. Sinclair nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.
ABSTRACT
Classification and understanding of congenital hand and upper extremity disorders has vastly improved since the 1970s. Congenital upper extremity disorders are challenging to treat, and there is a primary focus on achieving optimal function. Recognizing the various types of deformity, identifying potential surgical options, and managing patient expectations may lead to satisfactory results to both the surgeon and patient. It is important to evaluate the risks and benefits of surgery and work on a multidisciplinary team, as well as collaborate with other hand surgeon, to provide the patient with the best potential outcome.
Keywords: congenital hand disorders; dysplasias; malformations; pediatrics; syndactyly
Introduction
Treatment of congenital disorders of the hand and upper extremity requires an understanding of the embryology and developmental anomalies of the pediatric upper extremity. This chapter will include the most frequent congenital disorders that occur in the upper extremity, from the fingertips to the brachial plexus. Each section will feature a brief summary of the disorder and include recent developments in the understanding of the pathophysiology or treatment of each included diagnosis.
Embryology
The upper-limb bud appears in the human embryo 26 days after fertilization and continues until 47 days when the joints of the hand develop. The skeletal elements and connective tissues are derived from a core of mesoderm covered in epithelial cells derived from ectoderm. There are three known signaling centers in the limb that direct development with associated chemical signaling. These are listed in1,2,3,4 Table 1. Limb development is complex and specific timing of all of the associated signaling pathways that intersect at multiple points is responsible for the development of the upper extremity. Sonic hedgehog (SHH) protein plays a pivotal role in linking the three axes of growth.
The classification of congenital differences of the upper limb was initially accepted in the 1970s, before the current understanding of molecular and developmental biology and genetics. In 2010, the Oberg-Manske-Tonkin (OMT) classification system was proposed, separating congenital deformities into three groups: malformations, deformations, and dysplasias. This classification system has recently been shown to have excellent intraobserver and intraobserver reliability among pediatric hand surgeons.5
Symbrachydactyly
Symbrachydactyly is a congenital hand difference that can present with a variety of morphologic findings including brachydactyly, syndactyly, hand hypoplasia, and the presence of rudimentary nubbins that include elements of nail plate, bone, and cartilage. The central digits are typically absent, with relative sparing of the border digits.6
The incidence of symbrachydactyly is approximately 0.6 per 10,000 live births. It occurs primarily in males and is typically unilateral in presentation with the left side being predominantly affected.7 It is usually not due to a known genetic abnormality, but can be associated with Poland syndrome, in which unilateral hypoplasia or absence of the pectoralis major occurs.8
Table 1 Signaling Centers That Direct Development of the Limb | ||||||||||||||||||||
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The etiology of symbrachydactyly is unknown. A leading hypothesis is the “subclavian artery supply disruption sequence.”9 This hypothesis states that isolated transverse terminal limb deficiencies are associated with interruption of the subclavian artery at the sixth week of embryologic development, leading to a failure of outward limb growth.
The hand affected by symbrachydactyly can present with a variety of findings. The hand or entire limb is shorter and smaller than the uninvolved upper limb with underdeveloped digits: short or webbed digits, digital nubbins, or absent digits. The mesoderm is primarily affected in symbrachydactyly with characteristic preservation of ectodermal elements such as the nail plate and distal phalanges.
The surgical treatment of symbrachydactyly is specific to each patient and focuses on improving hand function if necessary. This includes providing length to the thumb or ulnar sided digits to enhance prehensile function.
Syndactyly and web contractures are released to improve aesthetics, independent digital function, and hand span. Nonvascularized toe phalangeal bone transfers provide additional length and stability for short, hypoplastic digits that have redundant soft tissue present. Distraction osteogenesis lengthening has also been described for the treatment of shortened digits in symbrachydactyly. Microsurgical toe transfers are another option to enhance pinch and prehension in symbrachydactyly.
Radial Longitudinal Deficiency
Radial longitudinal deficiency (RLD) is a spectrum of upper extremity dysplasia and hypoplasia affecting the entire limb. Presentation rests on a spectrum from mild hypoplasia of the thumb, to absence of the radius or proximal humerus. Some forms are spontaneous, but it can be inherited in both autosomal dominant and recessive patterns. RLD is associated with an underlying syndrome 33% to 44% of the time. Associated syndromes include Holt-Oram syndrome, thrombocytopenia absent radius (TAR), Fanconi anemia, and VACTERL association. The hand surgeon may be the first physician to see the child because of the visible upper extremity differences. Appropriate testing must be performed to evaluate for these associated anomalies and syndromes10 (Table 2). The patient and family should also be referred for genetics counseling. Holt-Oram syndrome can have a distinctive or unusual presentation of RLD, which includes atypical radioulnar synostosis, extending distally into the forearm with a reduced radial head and/or first web space syndactyly. If either of these defining features are present, Holt-Oram syndrome should be suspected and a cardiac evaluation and genetic testing should be performed.11
Table 2 Recommended Tests for Important Syndromic Associated Conditions in Radial Longitudinal Deficiency Patients | ||
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 Figure 1 Radiograph images and associated clinical photograph of a child with bilateral thumb hypoplasia. (Courtesy of Micah K. Sinclair, MD.) |
Involvement of the forearm in RLD is classified according to the severity of skeletal dysplasia of the radius. The spectrum includes abnormalities of the proximal radius with normal length, to mild shortening of the radius, to complete absence of the radius and severe radial deviation of the hand. In more severe radial shortening, with a radially deviated hand, the initial treatment is stretching and splinting. Soft tissue distraction with an external fixator before centralization is associated with a worse final radial deviation and volar subluxation position compared with centralization alone.12 Centralization at 1 year of age has been described with overall outcome of further shortening of the ulna due to physeal trauma and recurrence of deformity 36% to 47% of patients.12 Recently, the release of the radial soft tissue and volar bilobed flap transposition has been shown to be successful at maintenance of wrist motion and avoidance of injury to the ulnar physis, with similar recurrence rates to formal centralization.13,14 In a study of adults with RLD, grip strength, key pinch, forearm length, and elbow and digital motion were found to be more important to activity than radial angulation of the wrist.15
Thumb hypoplasia is included on the spectrum of RLD (Figure 1). Treatment is based upon the degree of hypoplasia, with the goal being stable, strong pinch and opposition (Table 3). For hypoplastic thumbs, opponensplasty can be performed using abductor digiti minimi with the benefit being increased bulk substituting for absent thenar musculature. Alternatively, the ring finger flexor digitorum superficialis may be used with excellent opposition function.16 There is no evidence to support one transfer over another; however, one must take into account available anatomy and patient size.
Table 3 Thumb Hypoplasia Classifications and Treatment Options | |||||||||||||||||||||||||||||||||||||||
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It is critical to differentiate the presence of a stable or unstable carpometacarpal joint when considering reconstruction versus pollicization in a hypoplastic thumb. Thumb ablation and pollicization is recommended for those with an unstable carpometacarpal joint. An important consideration when planning pollicization is the presence of index finger stiffness and patient preference for ulnar sided pinch, which occurs in severe RLD. The benefit of pollicization in this setting is controversial. Although the severity of radial dysplasia has been found to correlate with the quality of function after pollicization, overall satisfaction of the family with pollicization for both function and cosmesis has been shown despite stiffness of the pollicized thumb.17
Ulnar Longitudinal Deficiency
Ulnar longitudinal deficiency (ULD) is four times less common than RLD.7 It is a sporadic condition and is not associated with systemic conditions. It is often associated with other musculoskeletal conditions, including proximal femoral focal deficiency, fibular deficiency, phocomelia, and congenital scoliosis. Unilateral involvement is the most common presentation and the entire limb is involved. There is can be an abnormal or fused elbow. Most patients have missing ulnar digits, up to 70% present with thumb abnormalities and 30% present with syndactyly.
The majority of surgical procedures performed for ULD are for correction of thumb and hand deformity.18 Wrist and forearm deformities do not typically require surgery.
Radioulnar Synostosis
Congenital radioulnar synostosis (CRUS) is an abnormal connection between the radius and ulna that results from an insult in utero within the second month of gestation. Up to 30% are reported to be associated with syndromes or anomalies, and 60% are bilateral.19
Commonly described activity limitations include toileting, hand washing, catching a ball with a baseball glove, and swinging a tennis racket or baseball bat.
Patients present with some degree of fixed forearm rotation. The pronation of the forearm is measured as the angle between the humeral line and the axis of the radial styloid to center of ulnar head. Pain is not a common report.
Most of the patients with CRUS are high functioning and surgery is seldom indicated because of the common presentation of fixed rotation in a functional position. Surgical treatment includes an osteotomy that rotates the fixed forearm position into one that allows bimanual function.
Late presentation of elbow pain in a previously painful elbow can occur in some adolescents, particularly in those with anterior dislocation of their radial head. They may have loss of elbow range of motion and acute locking. When this occurs, excision of radial head to remove the block to motion is found to be successful in restoring previously painful range of motion.20
Preaxial Polydactyly
Thumb duplication has a reported incidence of 0.08 to 1.4 in 1,000 live births.21 The inheritance pattern is sporadic, and typically unilateral in presentation. The etiology is truly a split thumb, rather than a true duplication. The affected thumbs are more slender in appearance compared with the contralateral thumb. The ulnar thumb tends to be the larger and more dominant thumb.
The most common classification is the Wassel classification (Figure 2). An easy way to remember this classification is to count the number of abnormal bones, which correlates to the Wassel type. The most common type is a Wassel type IV thumb duplication, which is duplication of both the distal and proximal phalanges of the thumb on a common metacarpal. The pattern of counting abnormal bones yields true for all but the triphalangeal thumb, which is a Wassel type VII. This thumb difference may be associated with genetic syndromes.22
Surgical reconstruction typically consists of excision of the less developed digit and reconstruction of the more dominant thumb. The collateral ligaments should be preserved or reconstructed for long-term joint stability.
During reconstruction, a pollex abductus may be encountered. This is an abnormal connection between the extensor pollicis longus and the flexor pollicis longus (FPL), which can lead to angular deformity of the digit.
Postaxial Polydactyly
Postaxial polydactyly, or duplication of a digit on the ulnar border of the hand, is most common in those of African American descent.23 It is inherited in an autosomal dominant fashion. Postaxial polydactyly in those of Caucasian descent should trigger a more thorough genetic workup, as polydactyly in these individuals may be associated with other system abnormalities.
 Figure 2 Illustration of Wassel classification for preaxial polydactyly. (Reprinted with permission from Wassel HD: The results of surgery for polydactyly of the thumb. A review. Clin Orthop Relat Res 1969;64[22]:175-193. Available at: https://journals.lww.com/clinorthop/Citation/1969/05000/22_The_Results_of_Surgery_for_Polydactyly_of_the.24.aspx.) |
Postaxial polydactyly is classified as two types. Type A is a well-formed digit, and type B is a vestigial digit with the appearance of a skin tag. A type A digit should undergo formal surgical reconstruction, should the family elect this. A type B digit has traditionally been ligated with suture or surgical clips as a newborn. This may leave a small bump on the ulnar border of the hand. Formal surgical ablation may be preferred to improve cosmesis and avoid the observation of digit necrosis and autoamputation.
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