Congenital Longitudinal Deficiencies of the Upper Limb

Krister Freese MD, FAAOS

Stephen Butler MBBS(Hons), FRACS(Orth), FAOrthA, PFET(Hand Surgery)

Dr. Freese 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. Butler 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.

This chapter is adapted from James MA, Peck KM: Congenital longitudinal deficiencies of the upper limb, in Krajbich JI, Pinzur MS, Potter BK, Stevens PM, eds: Atlas of Amputations and Limb Deficiencies: Surgical, Prosthetic, and Rehabilitation Principles, ed 4. American Academy of Orthopaedic Surgeons, 2016, pp 823-830.

ABSTRACT

Radial and ulnar longitudinal deficiencies are the two most common congenital longitudinal deficiencies of the upper limbs and are characterized by a partially or completely absent radius or ulna, respectively. Radial longitudinal deficiency often is associated with abnormalities of other organ systems, including cardiac and renal systems, which can be potentially lethal and require a comprehensive medical evaluation. Ulnar longitudinal deficiency tends to be associated with other musculoskeletal abnormalities. Treatment aims to improve function and appearance and is best provided in a wellresourced setting in the context of a long-term relationship between the child, their family, and the hand surgeon.

Introduction

Radial longitudinal deficiency (RLD) and ulnar longitudinal deficiency (ULD) are the two most common congenital longitudinal deficiencies of the upper limbs. These conditions historically were described as radial or ulnar clubhand, but this term is no longer commonly used. The deficient bone may be partially or completely absent. In the 2013 classification by Kerby Oberg, Paul Manske, and Michael Tonkin, and approved by the International Federation of Societies for Surgery of the Hand¹, these deficiencies are classified as malformations of the upper limb resulting from a failure of formation of the radial-ulnar (fetal anterior-posterior) axis¹^,² (also known as preaxial [radius] or postaxial [ulna] longitudinal deficiencies).

Radial Longitudinal Deficiency

Clinical Features

RLD is characterized by partial or total absence of the radius and a short, bowed ulna that can result in profound radial and palmar displacement of the hand and the carpus. In severe forms the ulna is approximately two-thirds of its normal length. The humerus is often shorter than normal, and in rare cases may be absent.³ The elbow may be stiff and the thumb may be absent or hypoplastic. The index and middle fingers also may be stiff; the ring and small fingers are usually flexible.

RLD often is bilateral and asymmetric. Bilateral deficiency is twice as likely in those with syndromic RLD, as is having concurrent thumb hypoplasia.⁴ Thumb hypoplasia severity is correlated to RLD severity.⁴^,⁵^,⁶ The wrist is unstable because of a lack of radial carpal support, and grip is weak because this instability is combined with finger stiffness. Children with RLD have difficulty reaching away from the body because of radial deviation of the wrist and bowing of the ulna. Children with manifestations of radial and thumb deficiencies may have difficulty attaining independence with activities of daily living, such as fastening buttons and performing personal hygiene.

Etiology

Two recent Northern European population studies showed that the incidence of RLD is 0.4 to 1.6 per 10,000 live births.⁷^,⁸ Recent Congenital Upper Limb Differences (CoULD) data⁴ suggest that 32% of children with RLD have an associated syndrome (Table 1). Golbfarb et al⁹ found that 67% of children with RLD had an associated syndrome or musculoskeletal condition. Scoliosis was the most common associated musculoskeletal condition. Other limb anomalies include humeral hypoplasia, radioulnar synostosis, radial head dislocation, and stiff digits.¹⁰^,¹¹ The most common syndromes associated with RLD are VACTERL (vertebral malformations, imperforate anus, cardiac defects, tracheoesophageal fistula, renal abnormalities,
and limb defects) and Holt-Oram syndrome; others that are less common but critical to diagnose preoperatively are thrombocytopenia absent radius (TAR) syndrome, Diamond-Blackfan anemia (also known as congenital hypoplastic anemia), and Fanconi syndrome (also known as Fanconi anemia). Patients with TAR syndrome have severe RLD but usually have a hypoplastic thumb present. Those with Holt-Oram syndrome are more likely to have both RLD and radioulnar synostosis.⁴ The unclassifiable thumb or five-fingered hand are more common in patients with TAR syndrome or Holt-Oram syndrome and should alert the surgeon to the possible presence of these syndromes.⁴^,⁹^,¹²

VACTERL is a sporadic condition that includes anomalies of multiple different systems: vertebra, anus, cardiac, trachea/esophagus, renal, and limbs (including RLD).¹³^,¹⁴ Holt-Oram syndrome is an autosomal dominant condition that is characterized by cardiac septal defects as well as RLD.⁸ Diamond-Blackfan anemia, Fanconi syndrome, and thrombocytopenia absent radius syndrome are bone marrow failure syndromes that may present as RLD. These conditions should be diagnosed preoperatively and treated by a pediatric hematologist because they are treatable and potentially lethal if not diagnosed and treated.¹⁵

TABLE 1 Most Common Syndromes Associated With Radial Longitudinal Deficiency

Syndrome	Inheritance Pattern	Associated Anomalies
VACTERL	Sporadic	Vertebral malformations, imperforate anus, cardiac defects, tracheoesophageal fistula, renal abnormalities, and limb defects
Holt-Oram syndrome	Autosomal dominant	Cardiac septal defects and radial dysplasia
Fanconi syndrome	Autosomal recessive	Pancytopenia and radial dysplasia
Thrombocytopenia absent radius syndrome	Autosomal recessive	Thrombocytopenia, absent radii, mildly hypoplastic thumbs present
Diamond-Blackfan anemia	Inherited, but heterogeneous	Anemia and reticulocytopenia; growth retardation; craniofacial, upper limb, heart, and urinary system malformations

TABLE 2 Modified Bayne Classification of Radial Longitudinal Deficiency

Type	Thumb	Carpus	Distal Radius	Proximal Radius	Humerus
N	Hypoplastic or absent	Normal	Normal	Normal	Normal
0	Hypoplastic or absent	Absence, hypoplasia, or coalition	Normal	Normal, radioulnar synostosis, or congenital dislocation of the radial head	Normal
1	Hypoplastic or absent	Absence, hypoplasia, or coalition	>2 mm shorter than the ulna	Normal, radioulnar synostosis, or congenital dislocation of the radial head	Normal
2	Hypoplastic or absent	Absence, hypoplasia, or coalition	Hypoplasia	Hypoplasia	Normal
3	Hypoplastic or absent	Absence, hypoplasia, or coalition	Physis absent	Variable hypoplasia	Normal
4	Hypoplastic or absent	Absence, hypoplasia, or coalition	Absent	Absent	Normal
5	Hypoplastic or absent	Absence, hypoplasia, or coalition	Absent	Absent	Proximal upper extremity hypoplasia including abnormal glenoid and proximal humerus

Illustration redrawn from Forman M, Canizares MF, Bohn D, et al: Association of radial longitudinal deficiency and thumb hypoplasia: An update using the CoULD registry. J Bone Joint Surg Am 2020;102(20):1815-1822.

Thalidomide, a teratogenic agent prescribed as a sedative in the late 1950s, resulted in various limb malformations, including RLD.¹⁶ Other teratogens also may cause this malformation, depending on the timing of maternal exposure.

Diagnostic Studies

Children with RLD should undergo a complete physical examination, a thorough family history should be obtained, and a geneticist should be consulted. Radiographs of the entire upper limb (humerus, elbow, forearm, wrist, and hand—both sides) are essential to assess for associated abnormalities and to classify the condition. A spine radiograph should be obtained to evaluate for congenital spine anomalies associated with VACTERL.

A complete blood count (bone marrow failure syndromes), a cardiac echocardiogram (VACTERL and Holt-Oram syndrome), a renal ultrasonography (VACTERL), and a chromosomal breakage test (Fanconi syndrome) also are indicated.

Classification

Bayne and Klug¹⁷ classified RLD into four types based on the extent of radial hypoplasia demonstrated on radiographs. James et al⁵ combined Bayne and Klug’s classification with the modified Blauth classification for thumb hypoplasia to create a modified version that included children with carpal or thumb deficiencies in the presence of a normal radius.¹⁷ Additionally proximal longitudinal deficiency has also been included in modifications of the classification³ (Tables 2 and 3).

Treatment

The treatment of RLD is based on improving function and appearance. Functional impairments may be caused by thumb hypoplasia or absence, wrist instability with radial deviation and
palmar flexion of the hand in relation to the forearm, and an overall shortened arm. Controversy still exists concerning the best way to surgically address the radially deviated wrist, although most pediatric hand surgeons agree that children fare better with surgical rather than nonsurgical treatment. Kotwal et al¹⁸ reviewed 446 patients with RLD types 3 or 4 with a minimum follow-up of 5 years. A total of 309 patients were treated surgically, and 137 patients were treated nonsurgically. Despite the high recurrence of deformity after centralization, improvements in the surgically treated group included the appearance and alignment of the wrist and hand, finger
and wrist range of motion, and grip strength (Figure 1).

TABLE 3 Modified Blauth Classification of Hypoplastic Thumb

Type	Characteristic
I	Mild shortening or narrowing of the thumb
II	Thumb-index web space narrowing, hypoplastic intrinsic thenar muscles, and metacarpophalangeal joint instability
III	Type II hypoplasia plus:
		A: Extrinsic muscle abnormalities, hypoplastic metacarpal, and stable carpometacarpal joint B: Extrinsic muscle abnormalities, partial metacarpal aplasia, and unstable carpometacarpal joint
IV	Pouce flottant (floating thumb)
V	Absent thumb

Illustration redrawn from Forman M, Canizares MF, Bohn D, et al: Association of radial longitudinal deficiency and thumb hypoplasia: An update using the CoULD registry. J Bone Joint Surg Am 2020;102(20):1815-1822.

FIGURE 1 Images of a type 4 radial longitudinal deficiency and a type IIIB hypoplastic thumb in a child. A, AP radiograph. B, Clinical photograph of the limb. C, Postoperative photograph after centralization. D, AP radiograph after centralization, with intramedullary fixation in place.

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