Several factors distinguish the care of pediatric limb deficiencies versus adult amputations. Data suggest that 70% of the children seen in pediatric clinics have a congenital limb deficiency, and the remaining 30% have acquired amputations resulting from causes such as trauma and sarcomas.¹ For the child who has a congenital limb deficiency, both advantages and challenges need to be addressed. Children who are born with a limb deficiency are incredibly adaptable because they know no other existence. The use of a prosthesis often becomes second nature if it is incorporated during the child’s growth and development. When not wearing their prostheses, children also learn locomotion strategies, such as hopping, scooting, and crawling, which allows for the development of greater balance and strength in their sound limb. Patients with bilateral lower limb deficiency use their upper limbs and torso to propel themselves forward on the ground when not using prostheses, thus affording greater muscle development and dexterity.

Challenges in care relate to the appearance of the affected limb. Congenital limb deficiencies can be associated with other anomalies, such as irregular bone and muscle development, joint instability, and joint malrotation.² Data further suggest that 40% of patients have multiple limb involvement, potentially increasing prosthetic fitting challenges.³ Bony overgrowth is a challenge specific to a transosseous amputation. The terminal bone overgrowth can eventually overtake the soft-tissue envelope, potentially resulting in bone piercing through the skin.⁴

When given the opportunity, it is always preferable for the surgeon to perform a knee disarticulation that preserves the end-bearing surfaces, allows for additional growth through the distal femoral epiphyseal plate, and avoids terminal bony overgrowth. In the pediatric cohort, knee disarticulation is considered preferable to transfemoral amputation for many reasons. The primary concern in a growing child is that the development of the affected limb will keep pace with the sound limb. Knee disarticulation preserves the femoral epiphysis, allowing the growth mechanism in the femur to be unaffected. An end-bearing limb with primarily intact thigh musculature makes a knee disarticulation functionally superior to a transfemoral amputation.^5,6

In the pediatric patient, the indications to perform transfemoral amputation or a knee disarticulation are very broad. They can vary widely from congenital anomalies, as in the case of tibial deficiency, to traumatic lawn mower accidents, to oncologic cases.⁷ Data suggest a gradual decline in sport/physical functioning with higher level amputations. However, the literature suggests that amputation level did not affect pain scores, happiness, or basic mobility.⁸

When dealing with any level of amputations in children there two main fundamental principles. The first principle is to preserve as much length as possible. The longer lever arm allows for greater power and ease of prosthetic use.⁹ The second principle is to attempt to perform a disarticulation whenever possible; in part for the longer lever arm, but also to avoid the dreaded complication of terminal overgrowth.

In attempting to conserve energy, the child’s innate biologic potential allows for the surgeon to use surgical techniques that would have been likely unsuccessful in adults. In an adult there may be a reluctance to attempt wound closures under tension, and also skepticism about using split-thickness skin grafts. A split-thickness skin graft, even over large areas of the residual limb, may be tolerated relatively well by the child, while in an adult it can be fraught with complications.¹⁰

Disarticulations preserve the epiphyseal plate and ensure continued longitudinal growth. This is critical when dealing with transfemoral amputations. In amputations at this level, sacrificing the distal femoral physis, which accounts for 70% of the longitudinal growth of the femur, the residual limb length may provide a challenging prosthetic option if it is too short. What may have appeared to be a long transfemoral amputation in a very young child could potentially be extremely short in an adult.

Disarticulation precludes the development of terminal overgrowth or appositional growth of the transected bone. The prominent condyles usually atrophy, thereby eliminating the cosmetic objection to this type of surgery that is present when performed in adults. It should also be borne in mind that there is also an attempt made to provide enough space on the distal residual limb to accommodate knee components. The desired length of the residual limb, even in a knee disarticulation, must be discussed with the prosthetist to achieve an ideal outcome. It is not uncommon to perform a distal femoral growth arrest to achieve this ideal length. If the patient is skeletally mature and an epiphysiodesis is not an alternative, intercalary resection is also a viable option.

Pediatric transfemoral surgical techniques do not differ significantly from those of adults. Transfemoral amputation levels illustrate the importance of muscle reconstruction. The goals of reconstruction after transfemoral amputation are to regain muscle balance and to better position the limb so that it can sustain some weight on the side of the thigh. The transfemoral amputee can support very little weight directly on the end of their residual limb.

To balance the thigh muscles, the surgeon must perform myodesis (attachment of muscle to bone). The surgeon can secure the muscle by drilling holes into the bone and suturing the muscle directly to bone or by securing it onto the periosteum.

Because the adductor and extensor muscles of the hip attach at the lower end of the thigh, their insertion is sacrificed in a transfemoral amputation. The net effect is an unbalanced residual limb. Without a myodesis there is tendency for the limb to stay in a flexed and abducted position. Myodesis will provide a stronger residual limb that is more balanced and centered in the muscle mass. Myodesis can also provide benefits in reducing the adductor roll. The adductor roll is soft-tissue redundancies that can form high on the inner thigh and become bothersome with prosthetic fit. The cause of the adductor roll is believed, in part, to be caused by retraction of the muscles that are no longer held in place by a distal anchor. Myodesis is not a simple task. Muscles do not generally hold sutures well. In that case, the fascia may be the best available anchor point. Meticulous dissection should be performed to enable a good fascial layer to be sutured later.

When performing an amputation on a congenital limb deficiency the possibility of hip instability should always be considered. Hip instability may need to be addressed to provide an adequate fulcrum for a proper lever arm to function.

Indications for a knee disarticulation are congenital deficiency, a nonfunctional knee, and when reconstruction is not an option. Knee disarticulation is the preferred surgical option over a transfemoral amputation on a growing child, so that risks of overgrowth are obviated, length is preserved, and muscle transection is minimized.

This surgery can be performed with the patient in a supine or lateral position. A sterile tourniquet is preferred, and a posterior-based or anterior-based flap
can be used. The patella is excised at the time of the original amputation to minimize the risk of future patellofemoral pain. The patellar tendon and hamstrings are sutured to the cruciate residuum or the knee capsule to achieve appropriate myodesis (Figure 1).