Pediatric patients with congenital or acquired lower limb amputations require special considerations to maximize their function and minimize complications. Clinician should become familiar with a wide range of etiologies for lower limb amputation and their treatment implications. The growing skeleton introduces some unique challenges to the management of amputations, but also provides opportunities for growth modulation and deformity correction. Prosthetic management for pediatric patients varies depending on their anatomy, size, and functional needs.

Pediatric lower limb deficiencies or differences can be broadly categorized as either congenital or acquired.¹ Congenital conditions include transverse, both terminal and intercalary (ie, terminal aplasia, phocomelia), or longitudinal deficiencies (ie, tibial hemimelia, fibular hemimelia). Acquired etiologies for amputation include traumatic, infectious, oncologic, dysvascular, and neurogenic causes. Amputations through the tibial diaphysis or ankle joint are commonly used when the foot or ankle joint are not viable or functional.

The treatment of pediatric patients requiring lower limb amputation may differ from that for adult patients in several ways. In cases of elective amputation, the timing of amputation should correlate with the patient’s developmental milestones. It is generally recommended that lower extremity amputation be performed at 6 to 10 months of age, when children are pulling to stand and starting to walk.² Their gait pattern and velocity will continue to mature until age 3 to 4 years, at which time they may be candidates for more dynamic prostheses or activity-specific prostheses.^2,3 During childhood, patients typically require a new prosthesis every 12 to 24 months, compared with every 3 to 5 years for adults. This is due to both the continued growth of the limb as well as the increased activity level and demands of pediatric patients.

Pediatric patients with both congenital and acquired amputations must be monitored until skeletal maturity for any associated bony deformity or joint instability. This may include hip dysplasia or instability, angular deformity around the knee joint, or growth disturbance from trauma or infection.⁴ The residual limb length may also need to be optimized for an ideal prosthetic fit. Surgical options can include hemiepiphysiodesis for angular deformity, epiphysiodesis for a long residual limb, or gradual lengthening of a short tibial segment. Transtibial amputations are also prone to bony overgrowth in skeletally immature patients, who require close monitoring and often additional surgical management.^5,6,7,8 Many studies in adult patients have

shown differences in energy expenditure, function, and patient satisfaction based on the level of amputation. This is especially evident when comparing transfemoral versus transtibial amputations.^9,10,11 However, studies have shown that pediatric patients with amputation through the knee or distal have the same walking speed and oxygen consumption as children of the same age without amputation.^10,12 A comparative gait study between pediatric patients with Syme and transtibial amputation showed small differences in the prosthetic ankle range of motion, but comparable Pediatric Outcomes Data Collection Instrument scores.¹³
McQuerry et al¹⁴ reported that Pediatric Outcomes Data Collection Instrument scores were similar between pediatric patients of various amputation levels in the subcategories of pain, happiness, transfers, and basic mobility. There was a trend toward poorer sports and physical function in patients with transtibial amputation compared with transfemoral amputation.

Both elective and unexpected amputations can create significant stress and anxiety for patients and their families. Pediatric patients who have undergone amputation and their families significantly benefit from a multidisciplinary treatment team, including orthopaedic surgeons, prosthetists, physical and occupational therapists, psychologists or behavioral health specialists, and social workers. There are many additional community resources and support networks for families, both locally and nationally.^15,16

The Syme amputation is a true disarticulation of the ankle joint with maintenance of the heel pad for end weight bearing^17,18,19 (Figure 1). The malleoli are left intact. Its advantages include relative technical ease, decreased wound complications, and quick time to prosthetic fitting. The residual limb length and distal soft-tissue envelope allow patients to bear weight reasonably well without donning a prosthesis. In pediatric patients, amputation through the tibiotalar joint also avoids the potential for bony overgrowth seen with transosseous amputations.

The potential disadvantage of a Syme amputation is migration of the heel pad over time (8% to 45%).^20,21,22 A systematic review of pediatric Syme amputations reported a 28% incidence of heel pad migration (49 of 176 children).²³ Posterior heel pad migration is most common (Figure 2), although varus or valgus migration has also been reported. Heel pad migration can often be managed with prosthetic adjustments and may not require revision surgery.²⁴ Several technical modifications have been described to decrease the risk of heel pad migration. The anterior edge of the heel pad can either be sutured to the anterior ankle joint capsule or extensor tendons.¹⁸ Tenodesis of the Achilles tendon or peroneal tendons have also been described in an attempt to balance the residual forces on the heel pad.^25,26

The surgical technique for the Syme amputation most often describes extraperiosteal excision of the calcaneus, carefully preserving heel fat pad with its fibrous septae. The technique of subperiosteal excision of calcaneus has also been described and once secured to the distal tibia, it can potentially decrease the risk of heel pad migration and maintain the hydraulic function of the heel pad.^15,22 Some authors have noted that the calcaneal periosteum (with or without the calcaneal apophysis) can later ossify and essentially create a Boyd-type amputation²¹ (Figure 3). Other authors have noted that the ossified remnants of the periosteum or calcaneus can cause painful weight bearing or prosthetic fit, and therefore they advocate for extraperiosteal excision of the calcaneus.^19,20 Typically, the malleoli do not need to be resected in pediatric patients.

Although the residual limb length after a Syme amputation can allow end-bearing without a prosthesis and
potentially improve energy expenditure, a residual limb that is too long can limit prosthetic options. This is less likely to be an issue in patients with congenital deficiencies, because the involved limb is usually already shorter. At the time of skeletal maturity, a limb-length difference of 8 to 18 cm will provide enough clearance for a more dynamic or advanced prosthesis.^2,27 Morrison et al suggested that the optimal residual limb length be tailored to the patient’s level of function and activity, as well as preferred prosthetic option, rather than maximizing length in all patients²⁸ (Figure 4). If additional shortening is needed, surgical options include epiphysiodesis in a skeletally immature patient or acute shortening osteotomy of either the femur or tibia in skeletally mature patients.