33.1.1 Diagnosis of Transverse Arrest

Transverse arrest can occur at multiple levels, from the humeral down to the metacarpal level of the upper limb. Transverse arrest above the elbow is rare. The distal stump is usually rounded and often contains some nubbinlike hand/digital remnants (Fig. 33‑1). Areas of dimpling are sometimes present where the skin is tethered to the end of hypoplastic skeletal structures. The condition is most often unilateral and more often affects the left side. It has a 3:2 female predominance.

33.1.2 Treatment of Transverse Arrest

Regular detailed assessments of function and psychosocial well-being are required prior to embarking on any treatment given these children often adapt remarkably well to their limb differences.

The management of transverse arrest varies according to the level of involvement. In above-elbow transverse deficiencies, the main treatment options involve prostheses. However, in unilateral cases, compliance to prostheses can be poor in part due to a lack of sensory feedback from the devices. However, a variety of prostheses are available for trial and range from static to dynamic, some of which can be controlled by remaining skeletal structures or myoelectric impulses.

Surgical options for proximal transverse deficiencies include the removal of excess functionless parts such as digital nubbins or stump revision to facilitate prosthetic fitting. At the forearm level, few surgical options exist; one historic option described is the Krukenberg procedure. The radius and ulna are separated to create a basic prehensile pattern between the two bones. This procedure is not recommended because the cosmetic appearance is very poor and the separation of the forearm bones can prevent the effective use of prostheses.

Vascularized second-toe transfer is an option in children with carpal and metacarpal hands. In children with carpal hands, second toes can be transferred to the positions of the first and fifth digits. In the absence of digits, the transfer of two second toes in this way allows the creation of a basic prehension pattern. This tends to be more effective in cases where the child is able to cup their palm.

Distal cases of transverse arrest are often referred to as symbrachydactyly. Treatment options in these cases include web deepening, metacarpal transposition, distraction lengthening of existing skeletal parts, vascularized second-toe transfers, and nonvascularized toe phalangeal transfers. Preservation of the phalangeal periosteum and minimization of tension within the recipient soft-tissue envelopes in the hypoplastic digits are key to long-term survival of nonvascularized toe phalangeal transfers.

33.1.3 Outcomes and Complications

Careful assessment of cases is vital to prevent unnecessary intervention given these children adapt remarkably well. All viable treatment options must be explained to the child and family. The unpredictably of prosthesis use in unilateral cases must be emphasized. In more distal cases, at the carpal and metacarpal level, the creation or upgrade of a prehension pattern can significantly improve hand functionality and increase a child’s bimanual repertoire.

Donor site issues appear to be common in cases of nonvascularized toe phalangeal transfers particularly when children reach their adolescent growth spurt. However, techniques to minimize these complications such as the use of replacement iliac crest bone grafts have been shown to be effective.

Distal transverse deficiency is often an ideal indication for free vascularized toe transfer. Excellent outcomes have been seen in terms of function, cosmesis, and psychosocial well-being with little donor site morbidity in large series with significant long-term follow-up.

33.2.1 Radial Longitudinal Deficiency

Radial Longitudinal Deficiency (RLD) represents a spectrum of anomalies, which can involve the entire preaxial side of the upper limb. In the past, a variety of terms have been used to refer to the condition, including radial club hand, radial hypoplasia, and meromelia. RLD is the most common out of the longitudinal deficiencies and occurs in 1/30,000 cases. Unilateral cases are more common with a R:L predilection of 2:1. Genetic and environmental factors such as thalidomide have been shown to play a role in RLD.

RLD can be linked with other anomalies and syndromes, and therefore screening is essential (Box 33.1). Bilateral cases of RLD are more likely to have a syndromic association.

33.2.2 Diagnosis of Radial Longitudinal Deficiency

As a result of skeletal deficiency and soft-tissue abnormalities in RLD, the hand adopts a radially deviated and abnormally flexed posture at the end of a hypoplastic forearm (Fig. 33‑2). Complete assessment of the upper limb is important given that abnormalities can occur along its entire length from the shoulder to the radial side of the hand. The upper arm may be shorter with distal humeral epiphyseal involvement and in some cases a stiff elbow. The forearm is shorter to varying degrees and the severity of skeletal hypoplasia is classified into four grades based on radiographic assessment according to the system described by Bayne and Klug (Table 33‑1). Type 1 represents a short radius and type 2 a hypoplastic radius with involvement of the proximal and distal epiphyses. In type 3, the distal part of the radius is replaced by a tethering fibrous anlage and in type 4 there is complete radial aplasia. The main factors contributing to radial deviation are hypoplasia and mal-insertion of a combined muscle mass of FCR, ECRB, ECRL, and BR, radial displacement of the median nerve, tightened deep fascia, and in some type 3 cases a radial anlage. The forearm–wrist articulation is often unstable and nonfunctional with hypoplasia of the radial side of the carpus. Within the hand, the thumb is hypoplastic or most often absent. The index and middle fingers are also affected with varying degrees of hypoplasia and stiffness.

33.2.3 Associated Syndromes

There are a number of syndromes linked to RLD; these include VACTERL (vertebral anomalies, anal atresia, cardiac abnormalities, tracheoesophageal fistula, renal agenesis, and limb defects) association, TAR (thrombocytopenia and absent radius) syndrome, and Holt–Oram and Fanconi anemia (Box 33.1). These syndromes, which occur in approximately one-third of patients with RLD, confer a poorer prognosis and require early detection and treatment. Complete assessment of the limbs, cardiac, renal, spinal, and hematological systems must be carried out.