The incidence of congenital limb deficiencies is approximately 1 in 2,000 births. In the United States, approximately 1,500 infants annually are born with upper limb reductions and approximately 750 have lower limb reductions.¹ Reports in the literature from British Columbia range from 0.31% per 1,000% to 0.79% per 1,000 births. The variability in incidence likely results from differences in gene pools and reporting methods in different locations.^2,3,4 Approximately 30% of these infants have deficits in more than one limb (15% with two limbs, 5% with three limbs, and 10% with all four limbs).^5,6,7 The most common deficit for all congenital deficiencies is digital reductions, which account for approximately 50% of all reported cases. In approximately one-third to one-half of patients, other organs systems also are involved.

The etiology of congenital limb deficiency is briefly reviewed here in the
context of multiple limb deficiencies. Vascular disruptions remain the most common etiology and include disorders such as amniotic band syndrome, which accounts for approximately 35% of cases. Other congenital causes include gene mutation, familial occurrence, and known syndromes (24%); chromosomal abnormalities (6%); teratogenic causes (4%); and unknown causes (32%).⁸ In general, digits are more often affected than long bones, longitudinal defects are more common than transverse defects, intercalary deficits are rare, and upper limb deficits are either reported slightly more frequently or occur at an equal frequency as lower limb deficit. Both the upper and lower limbs are affected in approximately 8% of infants.^8,9 Amelia (complete absence of limb) is reported to be 1.41 in 100,000, and phocomelia (malformation of limb) is 0.62 per 100,000 births.^10,11

Limb deficiency can refer to the absence of a limb as well as to limb anomalies that might require a prosthesis or modified prosthesis for one or more of the involved limbs. For example, a child with the most severe form of thrombocytopenia-absent radius syndrome may have phocomelic upper limbs and fusion of both knees caused by congenital synchondroses. These children cannot effectively use their feet to replace limited hand function because their knees do not bend sufficiently to allow the foot to reach the mouth. If bilateral knee disarticulations are performed, the child would be able to sit in a chair more easily but would be unable to rise from the floor after a fall because their short arms could not provide adequate assistance.

Approximately 60% of children treated in amputee clinics have congenital conditions.^5,12 In addition, 10% of children with acquired amputations have a loss of more than one limb, although underreporting may occur because these children are generally treated in the community and not in pediatric amputee centers. This is particularly true of children with lower limb amputations, which are easier to manage in a less-specialized facility than are upper limb amputations.¹³ Among children who have acquired amputations, 40% involve the upper limb; however, in children treated at amputee clinics, congenital upper limb involvement is twice as likely as lower limb involvement.⁵

The reader is encouraged to review the embryology of limb bud formation. Limbs form concurrently with other organs such as the heart and kidneys between gestational weeks 4 to 7. Therefore, a thorough examination for associated anomalies is mandatory in a child with one congenital anomaly. The clinician should begin the examination at the head and work downward, checking the cranial nerves (especially cranial nerve VII) to test for associated Möbius syndrome, the palates (soft and hard), and the eyes and ears for placement and formation. The chest should be checked for the proper number and location of nipples, and the pectoral muscles should be examined. The heart should be examined for heart murmur, the anus for normal formation, and the spine for curvature and sacral dimples. The other limbs should be carefully evaluated for the presence of even minor abnormalities that could change the diagnostic (and possibly prognostic) category from single-limb to multiple-limb involvement. The presence of petechiae or bruises can suggest thrombocytopenia-absent radius syndrome because of low platelet counts. The infant’s mother and their nurses should be questioned regarding the infant’s sucking and swallowing to assess for tracheoesophageal abnormalities.

Additional studies may be indicated. Renal ultrasonography and radiography should be used to evaluate the spine and heart for all infants with a limb deficiency. A complete blood count and differential, including a platelet count, should be obtained for a child with a radial deficiency. Because upper limb deficiency syndromes, such as Holt-Oram syndrome, can have a particularly high association with cardiac defects, echocardiography should be strongly considered. Currently, there are no recommendations for a screening echocardiogram, specifically for a child with multiple limb reductions or anomalies; however, the most recent appropriate use criteria from multiple societies list clinically suspected syndrome or extracardiac congenital anomaly known to be associated with congenital heart disease as an appropriate indication for a newborn screening echocardiogram.¹⁴

Anomalies in the central nervous system or one of the receptive senses (vision or hearing) are of particular importance. Children are generally extremely adaptable, but if the central nervous system is involved, the child’s adaptive capacity may be compromised.¹⁵

Multiple limb deficiency is best managed by a multidisciplinary team in a center or group experienced with such children. Children with multiple limb deficiencies substitute other body parts to compensate for missing function of the residuum and affected limbs. Surgery requires very careful consideration because it can create secondary loss of function that is vital for the child. As an example, amputation or surgical correction of remnants of feet should not be done if they substitute for hands. This trade-off must be considered even if surgery could improve gait mechanics or lower limb prosthesis use.

Clearly, care must be individualized for each patient and their family. A few general principles do guide care. The first is to preserve length with split-thickness skin grafts and ideally prevent adherence to the bone to minimize hindrance in any prosthesis. The second is to preserve upper extremity sensation wherever possible. Experience demonstrates that many of these patients will forego even well-fitting prostheses if the residuum is long enough and sensate to allow them compensatory motion and function. For transverse deficiencies of the forearm, the Krukenberg procedure involves separation of the radius and ulna to create a pincer, and can be performed as early as age 2 years.²² The procedure is capable of restoring up to 4 mm of two-point discrimination and 10 kg of pincer carrying ability, but is less used in the modern setting because of cosmesis concerns.²³ The third is to offer only surgery, which maximizes function—this often implies waiting for the extent of full extremity function to be determined. In children with bilateral upper extremity deficiency, this then necessitates waiting to perform any lower extremity surgery until it is clear how children are using their lower extremities to accomplish their activities of daily living. Finally, consideration of how spinal mechanics may assist the child in accomplishing activities of daily living is paramount. Children often use spinal motion to compensate for deficient extremities. As such, management of scoliosis should use minimal fusion when absolutely necessary.

Children with multiple limb deficiencies have a greater need for specialized prosthetic components than do those with single limb deficiencies. Several characteristics of prosthetic components should be considered in relation to the special needs of the child with multiple deficiencies.

Prosthetic components for adults are usually available in large, medium, and small sizes, with perhaps an extra small size that is appropriate for smaller women. Children, however, need an array of sizes, ranging from those that can fit a tiny 1-year-old toddler up to devices for a teenager of nearly adult proportions. Although competition has encouraged many manufacturers to address this niche market, it is not economically feasible for manufacturers of prosthetic components to fabricate and store large stocks of multiple-sized items because of the relatively low demand. Therefore, some components may need to be individually crafted. The weight of prosthetic components is an issue not only because of the smaller muscle mass available to move the prostheses but also because children with multiple limb deficiencies find that minor difficulties with one prosthesis can adversely affect the functioning of another.²⁴

Wearing a prosthesis can be hot, especially in warm climates. The limbs provide an increase in total surface area of the skin, which is the primary source of cooling the core body temperature.²⁵ Children who wear two, three, or even four prostheses may not have enough bare skin to disperse heat adequately. In addition, prostheses for higher levels of limb deficiency demand greater energy expenditure by the child, compounding the heat problem. This is a particular problem if the child has a hip or shoulder disarticulation requiring a prosthesis that covers a considerable area of the trunk. Body temperature may become substantially elevated. Reasonable, normal activities may be prohibitive in any season but especially in the summer, and the child may understandably refuse to wear the prostheses as a result.