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Limb Deficiencies

  • Anna D. VergunEmail author
  • Hugh G. Watts
Chapter

Abstract

Limb deficiencies can result in functional disability and are often associated with significant social stigmas. Surgeons treating these conditions in resource-rich countries work in a team that includes prosthetists, physical and occupational therapists, and social workers. In places with limited resources, failure to appreciate the limitations imposed by the absence of such professionals, or deficiencies in their skills, can result in a lack of functional improvement and unnecessary use of resources. Treatment must be individualized and tailored to personal or cultural beliefs. The purpose of this chapter is to equip the surgeon with some basic principles to guide management of limb-deficient children in a variety of circumstances.

Overview

Limb deficiencies can result in functional disability and are often associated with significant social stigmas. Surgeons treating these conditions in resource-rich countries work in a team that includes prosthetists, physical and occupational therapists, and social workers. In places with limited resources, failure to appreciate the limitations imposed by the absence of such professionals, or deficiencies in their skills, can result in a lack of functional improvement and unnecessary use of resources. Treatment must be individualized and tailored to personal or cultural beliefs. The purpose of this chapter is to equip the surgeon with some basic principles to guide management of limb-deficient children in a variety of circumstances.

Most limb-deficient children have normal intellects and developmental milestones. Deficiencies may change the way a child crawls or walks, but will not change their major motor milestones. Interventions depend on functional and social circumstances.

Acquired amputations will have normal bone, bone growth potential, and soft tissues proximal to the amputation. Non-acquired amputations (congenital constriction bands), congenital limb deficiencies, and dysplasias commonly require an amputation and prosthetic fitting or limb reconstruction and surgery to address the accompanying foot deformity; hip, knee, or ankle instability; and limb length discrepancy (see Table 36.1, Fig. 36.1). In these cases, it is important to look for and recognize subtle deficiencies of the whole limb. Cardiac and renal anomalies are associated with congenital spine and limb deformities. The surgeon may be the first person to recognize that other organ systems are affected and should refer the patient appropriately.
Table 36.1

Congenital limb deficiencies. Limb deficiencies may involve the femur, tibia, or fibula and are associated with a spectrum of abnormalities within the osseous and soft tissue structures

Congenital limb deficiencies

Features

Treatment options

Femoral deficiencies

Congenital short femur (femoral length >50% of normal side)

If congenital short femur, then lengthen femur (or shorten contralateral femur)

Proximal femoral focal deficiency (PFFD)

If PFFD with stable hip, length <50%, then proximal femoral osteotomy, foot ablation, and knee fusion with fitting as a through-knee amputee

 Stable hip (coxa vara, has proximal femur and acetabulum ± pseudarthrosis

 Unstable hip or subtotal absence of proximal femur

If PFFD with unstable or subtotal absence, then foot ablation and knee fusion or custom prosthesis

Longitudinal deficiency of the fibula

Femoral deficiency common

If three or more rays on foot, then foot reconstruction, epiphysiodesis versus lengthening for leg length inequality

Fibula absent or hypoplastic

Knee cruciate deficiency, patellar dysplasia

If severe leg length discrepancy anticipated and/or severe foot deformity (<2 rays), then foot ablation and prosthetic fitting as a below-knee amputee

Tibia short with anteromedial bow

Equinovalgus foot with tarsal coalition, lateral deficiency

Longitudinal deficiency of the tibia

1/1 million births

If no tibia present and no knee extension, then through-knee amputation and prosthetic fitting as through-knee amputee

Most sporadic, rarely genetic (AD, AR)

Hand anomalies most common, visceral rare

If proximal tibia present, then foot ablation ± proximal tibiofibular synostosis and prosthetic fitting as a below-knee amputee

Femoral hypoplasia

Tibia can be (1) completely absent, (2) proximal tibia present with intact extensor mechanism, or (3) distal tibial deficiency with diastasis between tibia and fibula

If distal diastasis, then foot ablation and prosthetic fitting as a below-knee amputee

Knee cruciate deficiency, patellar dysplasia

Fibula angulated, dislocated proximal tibiofibular joint

Equinovarus or equinus foot

Fig. 36.1

A spectrum of abnormalities occurs in patients with longitudinal deficiencies of the femur, tibia, and fibula. Variations of femoral deficiency include (a) congenital short femur and (bd) proximal focal femoral deficiency. Tibial deficiencies include (e, f) complete absence of the tibia, (g, h) presence of an intact proximal tibia and extensor mechanism, (i) tibiofibular diastasis, (j) a fibular deficiency with a dysplastic fibula, and (k) postsurgical fibular to proximal tibial transfer with fusion of the calcaneus to the distal fibula (modified Boyd) to improve function as a below-knee amputee.

It is important to address the family’s fears of the recurrence of similar deformities or deficiencies in future offspring. However, if there is not already a family history, it is extremely unlikely future children will be affected as most cases are thought to be spontaneous mutations.

Both acquired and congenital amputations from constriction bands can have long bone overgrowth, requiring surgical capping of the bone ends with cartilage (Fig. 36.2).
Fig. 36.2

Modified Marquardt procedure. The periosteum is reflected off the distal aspect of the recipient bone, as well as off the proximal end of the “cap” (fibular head). The proximal aspect of the fibular graft is placed into the recipient bone, and the periosteal sleeve from the fibular graft is repaired. The periosteal sleeve from the recipient bone is wrapped around the graft and sutured to itself and to the periosteum over the distal aspect of the fibular graft

Patient Evaluation

The history focuses on limb function by considering the following questions:
  • What are the missing segments, and how do they affect function?

  • Are there any muscle, nerve, fat, or skin abnormalities or dimples to suggest additional soft tissue involvement?

  • What is the resting posture of the limb?

  • What muscle groups are used to effectively flex, extend, abduct, and adduct the limb?

  • Which joints are stable or unstable?

Thoroughly examine both upper and lower extremities, look at the spine, and watch the child move around and do activities of daily living. Focusing the exam on the most severely involved limb is a common pitfall. Carefully consider what tasks are functionally important for the child and how surgery may improve or worsen their function. For instance, a child with PFFD may have a very externally rotated femur with limited hip range of motion. Internally rotating the femur may improve the gait but will not easily allow for sitting cross-legged on a floor, which is important in some communities. If there is an associated scoliosis, determine how important spine flexibility is for gait and other activities.

For the lower limbs, determine the length inequality. The relative contribution of the femoral segment is determined with the hips and knees flexed while the child lies supine on a firm surface. The relative contribution from the leg and foot segments is determined with the child prone with the hips extended and the knees flexed. For children who can stand, the total discrepancy can be measured with the patient standing on calibrated wooden blocks or a measurable platform. Contractures at the hip, knee, and/or ankle may contribute to the functional discrepancy, as may shortening associated with a foot deformity, such as clubfoot.

Additional Studies

X-rays supplement clinical information regarding the location of a bone deformity and the limb length discrepancy. If there is a joint contracture or the child is very young, lateral views of both lower limbs give a good idea of any relative discrepancy. Delayed ossification of the cartilage anlage can give the appearance of a missing joint. Look for secondary signs of joint formation by examining the more normal side of the joint. For instance, a well-defined acetabulum indicates the presence of a cartilaginous femoral head. An ultrasound can help identify an unossified or partially ossified cartilaginous anlagen. If the local anatomy remains unclear, it may be wise to wait and reevaluate in 1 or 2 years.

General Treatment Considerations

Predicting future growth is essential, and the surgeon should be prepared to predict the projected discrepancy.

For an infant or small child with a congenital, (non-acquired) deficiency, the limbs will grow proportionally. An estimate of the projected discrepancy will determine if an amputation at a young age should be considered. A useful tip: when comparing limb lengths, a heel on the shorter side that rests at the level of the mid-tibia on the longer side will also rest at this level at skeletal maturity. In an average height person, the distance from the mid-tibia to the ground is about 20 cm, which is about the maximum difference one would consider lengthening a limb in a resource-rich country. This can help project length differences and guide whether an amputation or length equalizing surgery is most appropriate.

At maturity, the average length of a femur is 41 cm for girls and 44 cm for boys [1, 2]. The average length of a tibia is 34 cm for girls and 37 cm for boys [1, 2]. For example, if the affected femur measures 80% of the length of the normal, contralateral femur, a rough estimate of the discrepancy at maturity will be 20% of 44, or 8.8 cm, for a boy.

Another rough guide: girls reach half their skeletal height by age 3 and boys by age 4. The discrepancy at these ages can be doubled for an estimate of final discrepancy. At ages 6 for girls and 8 for boys, the discrepancy can be multiplied by 1.5 [3].

For children aged 8 and older with a congenital deficiency, while there is still future growth to consider, a large projected discrepancy at maturity will be obvious on clinical exam, and management decisions can be made without detailed calculations. For projected discrepancies ≤10 cm, a more accurate assessment is important to consider timing of an epiphysiodesis or an acute shortening to better equalize the limb lengths. To project the final discrepancy and time for epiphysiodesis, the arithmetic method is simple and reasonably accurate [4, 5] (Table 36.2).
Table 36.2

Arithmetic method [3, 4]

This method is used in timing epiphysiodesis in patients older than 8 years, based on several assumptions

1. Distal femoral growth plate grows at 3/8 in. (9 mm) per year

2. Proximal tibial growth plate grows at 1/4 in. (6 mm) per year

3. Boys stop growing at 16 years of age

4. Girls stop growing at 14 years of age

5. If one of the growth plates is completely arrested, the discrepancy will increase at a rate corresponding to the normal rate of growth for that plate. Otherwise, it will increase at 1/8 in. (3 mm) per year

6. Calendar age is adequate in assessing growth, and skeletal age need not be assessed

In the setting of growth arrest from trauma or infection, assume normal growth parameters per year until skeletal maturity. Add this value to the current discrepancy to project the final discrepancy. For children affected at a very young age—for example, neonatal sepsis with total physeal ablation—it is useful to know the percentages of growth provided by each growth plate for the entire limb. These are roughly as follows: proximal femur, 15%; distal femur, 35%; proximal tibia, 30%; and distal tibia, 20%. The yearly growth of individual physes has also been estimated (see Chap.  26, Table  26.2).

Determining the skeletal age of the child is the source of the greatest error in predicting limb length discrepancies. The calendar age is clearly the most convenient number to use; however, children undergo a prepubertal growth spurt at a variety of ages, and growth can be severely affected by malnutrition.

Predicting future function is critical when planning treatment. One of the first considerations is the child’s access to skilled prosthetic care. Anything other than a standard below- or above-knee prosthesis requires more skill to make, and a poorly fitting prosthesis will be painful and lead to pressure sores, infection, and nonuse. If the patient with a short lower limb can be fitted for a standard prosthesis without changing the limb (e.g., a small foot can be incorporated into the prosthesis), this may be a good first step for management. Though this avoids surgery and maintains a good weight-bearing end to the limb without the prosthesis, reliable access to a good prosthetist is the final determinant to success. If unsure of the skill of the prosthetist, ask what surgical modifications can be made to the limb to simplify the prosthesis and provide a better fit.

For acquired amputations, either from trauma or infection, effort should be made to preserve growth of the physis in young children. For instance, the bone and physis may be unaffected, but there may be inadequate distal soft tissue coverage for primary closure. Instead of amputating at a higher level, which would sacrifice the growth plate, the long bone can be shortened at the metaphyseal diaphyseal junction, allowing the soft tissues to telescope for primary skin closure over the growth plate.

Avoid mid-diaphyseal amputations in children if at all possible because of bone overgrowth. If this cannot be avoided, the surgeon should cap the distal bone with an osteochondral graft, as described by Marquardt [6]. This can be taken from the amputated limb, such as a metatarsal head, or from the proximal fibula with good success for permanently halting the painful overgrowth [7]. The periosteum from both the donor and recipient bone should be approximated with suture after the bone is wedged into the canal with an interference fit. Cartilage capping is ideally performed at the time of amputation but can be equally successful with a fibular head autograft to treat overgrowth that has already occurred (Fig. 36.2).

Avoid scars along the weight-bearing portion of the limb. Begin shrinking the stump as early as 2 weeks postoperatively to prepare for prosthetic fitting. Unlike adults, the skin, including split-thickness skin grafts, and other soft tissues will often hypertrophy at the weight-bearing end of the stump.

Upper Extremity Deficiencies

The goal for the upper extremity is to assist activities of daily living. Do not take off nubbins unless they are problematic, as they provide traction and sensation. Patients with unilateral upper extremity deficiencies often compensate with the contralateral upper extremity, while those with bilateral deficiencies may be able to compensate with their lower extremities. When the deficiency is well compensated, it is inadvisable to recommend an upper extremity prosthesis that is insensate. Many children will reject upper extremity prostheses unless introduced before 1 year of age. In the rare circumstance when a child is poorly compensated, such as bilateral below-elbow deficiencies, a Krukenberg reconstruction can be considered [8], as described in Chap.  41. In addition, while a severe foot deficiency may make ambulation difficult, the foot may be used to substitute for the hands if the child is missing both upper extremities (Fig. 36.3). In this case, it would be shortsighted to amputate the feet.
Fig. 36.3

This child with the absence of both upper extremities will learn to use his feet for a variety of tasks

Lower Extremity Deficiencies

The most appropriate management depends on the severity of the foot deformity, knee and ankle joint stability, ongoing access to a prosthetist, and the social situation of the child. While longitudinal growth will usually remain proportional, angular deformities and contractures can increase, and the gait will change as the child matures. A deformed but functional joint in a child may become painful and nonfunctional in an adult.

See Table 36.1 for major categories of congenital lower extremity deficiencies and common treatment algorithms. If possible, preserve the knee joint, as energy expenditures are considerably less for a below-knee amputation versus one more proximal. However, an above-knee amputation is preferable in the absence of active knee extension. If the femur is >50% the length of the contralateral side, consider a through-knee amputation. For the patient with an extremely short femur, <50% of the length of the contralateral femur, consider combining a knee fusion with a foot ablation procedure, so the patient can be fitted as a through-knee amputee. The authors prefer a Boyd amputation (excision of the ankle joint, including the distal tibial physis, with fusion of the calcaneus to the distal tibia) rather than a Syme amputation (ankle disarticulation) (see Chap.  43).

Any of these procedures may need to be combined with an epiphysiodesis to allow the mechanical knee to fall near the same level as the contralateral side at skeletal maturity. Large discrepancies in knee height lead to differences in swing phase duration and can produce a dysfunctional compensatory gait pattern. The surgeon should plan for the femur to be shortened with a timed epiphysiodesis so the above-knee amputation results in a stump that is about 5–6 cm proximal to the contralateral knee at skeletal maturity. A below-knee prosthesis requires about 10 cm for cosmetic appearing ankle and foot components, and the ideal stump length is between 15 and 25 cm at skeletal maturity.

The timing of surgical interventions depends on the projected limb length discrepancy and whether it is more reasonable to preserve the affected limb and shorten the long side or if an amputation on the affected side is better. Ideally, intervention is timed to allow the child to reach his normal motor milestones. Amputations are psychologically easier for the child the earlier they are performed. If the function of the limb is uncertain, particularly concerning hip and knee extension, it is best to wait until the child develops and the clinical picture clarifies. In the meanwhile, children can be fitted with an extension orthosis or a large external shoe lift to improve their gait (Fig. 36.4).
Fig. 36.4

An extension orthosis on an adolescent girl with a congenitally short femur

In most austere environments, lengthening the short limb is not an option due to the high complication rate and need for ongoing monitoring and surgical interventions.

Although the concept has been popularized that a limb should not be shortened more than 5 cm, this has no basis other than concern for the appearance of a relatively long trunk relative to the limbs. If shortening a long limb by 10 cm with an epiphysiodesis will be a simple surgery to address a complicated problem, it is probably the right choice despite cosmetic concerns. A common error is to correct the current discrepancy and not the projected discrepancy at maturity. An acute shortening can be performed at any time; however, the surgeon is limited up to 5 cm in the femur and 3 cm in the tibia due to difficulty with soft tissue closure after the soft tissues telescope around the shortened segment. Acute shortenings can be staged once the soft tissues have shrunk to provide a larger magnitude of shortening.

Prosthetic Pearls

  • Even prosthetists who have considerable experience with adult amputees may not understand all the needs specific to children. Ideally, the surgeon and prosthetist work together to best address the individual needs of the child.

  • Due to growth a child may need a new socket every 6 months or a year. A prosthetic foot will last about 1 year, and a prosthetic knee can last between 1 and 3 years before needing replacement.

  • Pain in the residual limb may be a result of poor socket fit, a bony prominence like tip overgrowth or exostosis, a neuroma, or skin problems from pressure or sheering of the skin against the inside of the prosthetic socket. Sometimes the socket needs to be changed, and sometimes the surgeon needs to change the shape of the limb. This is best determined by a conversation between the surgeon and prosthetist.

  • Bilateral amputees may not initially tolerate prostheses at full height, especially if their walking has been delayed due to limb deformities. Their initial prostheses should allow for a low center of gravity with height gradually increasing as tolerated.

References

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Internet Resources for Limb Deficiency and Loss

  1. For care providers: http://www.acpoc.org/.
  2. The Association of Children’s Prosthetic-Orthotic Clinics provides a comprehensive resource of treatment options.Google Scholar
  3. This site provides education, support and advocacy.Google Scholar

Copyright information

© Springer Nature Switzerland AG 2020

Authors and Affiliations

  1. 1.Department of OrthopedicsUniversity of North CarolinaChapel HillUSA
  2. 2.Shriners Hospital for ChildrenPasadenaUSA

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